6th RaDIATE Collaboration Meeting

9 Dec 2019, 08:30 → 13 Dec 2019, 12:00 US/Pacific

TRIUMF

Alexander Gottberg (TRIUMF), Patrick Hurh (Fermi National Accelerator Laboratory)

The 2019 RaDIATE Collaboration Meeting will take place at TRIUMF between 9th and 13th December 2019. The meeting will address topical issues associated with radiation damage in accelerator targets environment, as well as providing a forum for discussing between experts in this specialized domain.

 

Topics that will be discussed include:

• Applications with radiation damage concerns
• Radiation damage studies
  • Low energy irradiation studies
  • High-energy proton irradiation studies
• Thermal shock studies
• Radiation tolerant material development
• Irradiation facilities
• Post irradiation examination and remote handling techniques
• Radiation damage modelling

 

Special added topic for the 6th RaDIATE Collaboration Meeting:

• Radiation induced chemistry in particle accelerator environments

Poster RaDIATE 2019 Group Photo

Monday, 9 December

08:30 → 09:00 Arrival and registration

09:00 → 10:30 Opening Plenary

Conveners: Dr Alexander Gottberg (TRIUMF), Mr Patrick Hurh (Fermi National Accelerator Laboratory)

09:00 Welcome to TRIUMF

Speaker: Dr Alexander Gottberg (TRIUMF)

Slides 2019-12-09_Gottberg_RaDIATE_-_Welcome.pptx

09:10 Associate Director's Welcome

Speaker: Dr Oliver Kester (TRIUMF)

Slides Welcome_RADIATE_WS_2019_OK.pdf Welcome_RADIATE_WS_2019_OK.pptx

09:15 Overview of RaDIATE Activities and Meeting Objectives

Speaker: Mr Patrick Hurh (Fermi National Accelerator Laboratory)

Slides RaDIATE_2019_Collab_Mtg_Objectives.pptx

09:45 How to make a Radioactive Ion Beam - An Alchemist's Dream

The family of Radioactive Ion Beam (RIB) facilities is growing and gaining capabilities with new projects in preparation at RISP (Korea), INFN-LNL (SPES), GSI (FAIR) and expanding facilities at ISAC (ARIEL), NSCL (FRIB), ISOLDE (HIE-ISOLDE and EPIC), RIKEN (RIBF), ANL (Caribu) and others. The programs are based on the ISOL or fragmentation production techniques with added capabilities of gas-stopping and reacceleration for the fragment approach and the fragmentation of reaccelerated RIBs produced using the ISOL technique. Physics programs are\ broad with increasing interest in the development of theranostic ions for medical applications. This talk will give an overview of the global progress in developments critical ingredient for making a radioactive ion beam.

Speaker: Dr Alexander Gottberg (TRIUMF)

Slides 2019-12-09_Gottberg_RaDIATE_-_How_to_make_a_RIB.pptx

10:30 → 11:00 Coffee Break + Group Photo

11:00 → 13:00 1st Oral Session: Applications with Radiation Damage

Convener: Mr Patrick Hurh (Fermi National Accelerator Laboratory)

11:00 Overview of the ISOLDE Facility and of the EPIC Project

The operation of the on-line isotope separator ISOLDE at CERN allows the production of a wide variety of radionuclides that are delivered in the form of Radioactive Ion Beams (RIBs) to different experimental setups installed in the ISOLDE beam lines. The radionuclides are produced in thick targets bombarded by the pulsed proton beam delivered by the Proton Synchrotron Booster (PSB). During the period 2018-2019, major improvements and consolidations of the CERN injector chain are implemented under the auspices of the LHC Injectors Upgrade (LIU) project. For ISOLDE, the higher available proton current with the new Linac4 as injector and the increase of the PSB energy from 1.4 GeV to 2.0 GeV open new perspectives and improvement objectives identified in a project proposal called EPIC (Exploiting the Potential of Isolde at CERN). For example, the higher available energy results in an increase of the production of short-lived radionuclides at the limit of nuclear existence, in particular the ones produced by fragmentation and spallation reactions. The higher available proton current allows a reduction of the required beam time for experiments previously limited by the low RIB intensity. Alternatively, the experimental capabilities and available beam time can also be significantly enhanced by the operation of new target stations constructed in such a way that RIBs can be delivered in parallel to the low energy and high-energy beam lines. In order to receive the 2 GeV beam from the PSB and construct new target stations, major modifications of the target area must be performed. In particular, the HRS and GPS beam dumps absorbing the remaining beams and secondary particles after the two target stations will have to be replaced by two new systems capable of sustaining the higher beam power and meeting modern radiation protection standards. Parasitic or dedicated irradiations have occasionally been performed in the past to serve mainly the needs of target developments but operational limitations and constraints have been identified and limit a more systematic use of the facility. The replacement of the beam dumps and the construction of new target stations could be a unique opportunity to foresee an infrastructure adapted to material irradiations in parallel to ISOLDE operation. The presentation provides an overview of the EPIC project with an emphasis on the target area upgrades and provides an assessment of the radiation fields in the areas of interest in order to assess the performances of ISOLDE for parasitic irradiations of material or equipment. A description of the strengths of ISOLDE with the presence of a laboratory dedicated to the management of radioactive material, remote handling capabilities as well as the presence of a shielded hot cell to address the radiation protection challenges associated to irradiation experiment is also provided.

Speaker: JOACHIM VOLLAIRE (CERN)

Slides ISOLDE_RadiateColMeet6.pptx

11:25 Lifetime Assessment of Beam Intercepting Devices and Moderators at the ESS Target Station during Initial Operations Phase

The ESS Target Station is designed to convert the 2 GeV protons to a high flux of low energy neutrons for scientific research, at 5 MW beam power. It will start receiving proton beam from the linac for neutron production in 2022. Upon commissioning “beam-on-target,” the linac will deliver protons at 571 MeV, which is lower than the nominal value 2 GeV. During the initial operations phase after the beam commissioning, the proton energy and beam power will be ramped up continuously towards 1.3 GeV and 3 MW, with sequential commissioning of super conducting cryomodules during long shut down periods. During neutron production, the spallation target, proton beam window, multi-wire beam profile monitor and moderators are exposed to intense flux of primary and secondary particles, suffering from radiation induced structural degradation. The service lifetimes of these components are limited mainly by the displacement damage, helium production rate, and solid transmutations, where the extent of the radiation damage depends on the kinetic energy and particle density of the impinging protons. To secure availability and reliability of the neutron production during this ramp-up phase, the proton energy dependent radiation damage rates in the core target components have to be assessed and the dose-limited lifetime be defined for the timely maintenance of the affected systems. In this talk, we present the lifetime criteria of core functional components in ESS target environments, during the proton energy ramp-up phase. Finally, we propose a set of proton beam parameters that have to be monitored, to plan the maintenance and replacement of the devices affected by radiation damage.

Speaker: Dr Yong Joong Lee (ESS)

Slides RaDIATE_Lee_V2.pptx

11:50 The current Status of CSNS solid target

A 100 kW solid target was successfully developed for the CSNS phase one. Tungsten was selected as the CSNS target material and a layer of tantalum with a thickness of only 0.3mm as a protective layer. Eleven target blocks were fixed in parallel in a stainless steel target container with 1.2mm gap between each block. Using a specially designed spreader, the target plug can be easily replaced. During the nearly two years of operation, the parameters of the target cooling water were stable and normal, the temperature rise of the target cooling water inlet and outlet increased as the proton beam power increased. Every year, the target surface was carefully observed by a high definition camera in the hot cell. Last year, no abnormal were found on the target surface, however, the surface of the target showed signs of turning yellow in some regions.

Speaker: Mr Shaohong WEI (Institute of High Energy Physics, Chinese Academy of Sciences)

12:15 Radiation induced effects in ISOL targets

The Isotope Separation On Line (ISOL) method is adopted in several accelerator facilities around the world in order to produce a number of isotopes of interest for a variety of branches of science. At the core of ISOL facilities is a target and ion source assembly which has to withstand extreme temperature conditions and constant particle irradiation, which are both playing a role in the material performance, evolution and degradation of the central components of an ISOL facility infrastructure. At TRIUMF, the ISAC facility currently delivers a 500 MeV, 50 kW proton beam to ISOL targets in order to trigger nuclear reactions with the target material and produce radioisotopes. Moreover, the new ARIEL facility will provide a 35 MeV, 100 kW electron beam onto a Bremstrahlung converter to subsequently induce photofission in uranium carbide. Both facilities include areas of high temperature and radiation field conditions on a variety of materials. This contribution will present some of the phenomena taking place at the core of our facilities, with major focus on the ongoing efforts to understand the transport properties of our target materials and their evolution over 3 weeks of operation, and the electron-to-gamma converter material investigation studies which led to the selection of tantalum-aluminum as the metal pairing to be used as converter material.

Speaker: Mr Luca Egoriti (TRIUMF)

Slides Radiate_December2019_TRIUMF.pptx

12:40 Discussion

13:00 → 14:00 Lunch

14:00 → 15:30 2nd Oral session: PIE and RH techniques

Convener: Grant Minor (TRIUMF)

14:00 A review of mechanical testing methods across multiple scales

Speaker: Dr Benjamin Eftink (LANL)

14:25 Development of ultrasonic meso-scale fatigue testing of irradiated titanium alloys for proton beam window applications

Titanium alloys such as commercially available Ti-6Al-4V are currently used as the beam window material in the T2K (Japan) proton beam target for neutrino production due to their high specific strength and low thermal expansion coefficient. Thermal spikes from the pulsed beam cause high frequency stress waves with magnitudes well below the yield stress, which subject the component to high-cycle-fatigue (HCF) loading. The effect of proton irradiation on the fatigue life in the HCF regime is largely unknown, especially at the high radiation damage doses seen in operation. With the desire to increase the incident beam power to in excess of 1 MW in future experiments, causing damage doses well in excess of 1 dpa per annum, there is a growing need for the beam window manufacturer (STFC, UK), to fully understand the material performance limits under these extreme conditions. In this collaborative research project, thin foils of titanium alloys have been irradiated to 0.25 and 1 dpa at the Brookhaven Linac Isotope Producer (BLIP) at the Brookhaven National Laboratory (BNL), USA. The alloys included the current Ti-6Al-4V beam window material in addition to several potentially radiation-resistant grades. Using an evolution of the ultrasonic meso-scale fatigue test developed at the University of Oxford, we will perform high-cycle fatigue testing on these irradiated specimens at the Materials Research Facility (MRF) at the Culham Science Centre, UK. Microstructural investigation yielding crystallographic (EBSD) and chemical (EDX) information will be performed. The effect of irradiation damage on each alloy will be assessed and related to the microstructure. This will allow suitable materials to be specified for future beam window designs. This presentation will cover the developments in the design and commissioning of an ultrasonic fatigue rig (UFR) at the MRF, UK. The capabilities of the UFR and associated real-time diagnostics will be outlined, along with the proposed ultrasonic test procedures and data analysis routines. An update on the materials research will be given, including microstructural and chemical analysis on the unirradiated specimens.

Speaker: Mr Phil Earp (University of Manchester / United Kingdom Atomic Energy Authority)

Slides 20191209_-_Phil_Earp_-_RaDIATE_2019.pptx

14:50 Microstructural Characterisation of Four Grades of Fine Grain Graphite over Multiple Length-scales

Abstract High power particle production targets are key for current and future generation accelerator driven facilities, e.g. neutrino beams such as T2K in Japan and the Long Baseline Neutrino Facility (LBNF) at Fermilab. During operation, the target materials will be bombarded by ultra-high energy protons inducing high thermal stresses and radiation damage, compromising their useful lifetime. Graphite, as a low-Z refractory material, with a low thermal expansion coefficient and low modulus, is uniquely qualified. Several past proton-irradiation experiments carried out at Brookhaven Linear Isotope Producer facility in searching for suitable target material candidates suggested that graphite properties (e.g. elastic modulus, yield strength and coefficient of thermal expansion) degraded with proton irradiation. Due to the important role played by both the initial degree of porosity, crystallinity and the crystalline size in the subsequent development of irradiation damage in graphite (e.g. anisotropic dimensional changes and physical property degradation), it is therefore imperative to obtain a sound understanding of these aspects in unirradiated graphite prior to irradiation experiment [1-5]. In collaboration with U.S. Fermi National Accelerator Laboratory under international RaDIATE programme, this work investigated the microstructures of four grades of unirradiated fine grain graphite target materials over multiple length-scales: POCO ZXF-5Q, IG 430, CL 2020 and SGL R7650, as well as one proton irradiated NT-02 target (POZO ZXF-5Q) extracted from NuMI/MINOS experiment to underpin the selection of next generation proton beam target. Specifically, a multiple length-scale approach incorporating X-ray computed tomography (Zeiss Xradia Versa 520 3D X-Ray Tomography) and Focused Ion Beam serial milling nanotomography (FEI Helios NanoLab 600i Dualbeam) was adopted for the characterisation of porosity. The results showed that the four grades of graphite have distinct porosity structures with the POCO ZXF 5Q graphite having the most uniform porosity size and spatial distribution over the measured length-scales. In addition, the crystal properties, mainly characteristic crystalline size on freshly fractured and machined surface of all four grades of graphite, were studied using Renishaw 2000 micro-Raman spectroscope (514 nm green laser excited from argon filament (Ar+, 2.41 eV excitation energy) at ∼8 mW power). The results showed that machining, either via slow speed diamond saw cutting or electron discharge machining, tends to introduce damage to the graphite surface and results in smaller characteristic crystallite size. The measurements of the ‘true’ crystallite size were therefore undertaken on freshly fractured surface on all samples. It is worth noting that POCO ZXF-5Q has the most narrowly distributed characteristic crystalline size with a mean value of ~80 nm on freshly fractured surface. Further, these Raman spectra data were compared to the results obtained from the proton irradiated NT-02 samples (POCO ZXF grade) at UKAEA Culham (532 nm green laser from argon filament source Raman System (Ar+, 2.33eV excitation energy equivalent) at ∼10 mW power). Irradiation induced disorder, as reflected in the increase in D peak intensity accompanied by G peak broadening, was observed in these irradiated NT-02 samples. The implications of the porosity on the behaviour of irradiated graphite will be discussed and it is suggested that the isotropic properties found in POZO ZXF-5Q could potentially be beneficial to the target performance under applied temperature and irradiation environment. References [1]. Krishna R, Wade J, Jones AN, Lasithiotakis M, Mummery PM, Marsden BJ. An understanding of lattice strain, defects and disorder in nuclear graphite. Carbon. 2017; 124:314 – 333 [2]. Kelly B, Burchell T. Structure-related property changes in polycrystalline graphite under neutron irradiation. Carbon. 1994;32(3):499–505. [3]. Brocklehurst J, Kelly B. The dimensional changes of highly-oriented pyrolytic graphite irradiated with fast neutrons at 430 C and 600 C. Carbon. 1993;31(1):179–183. [4]. Krishna R, Jones AN, McDermott L, Marsden BJ. Neutron irradiation damage of nuclear graphite studied by high-resolution transmission electron microscopy and Raman spectroscopy. Journal of Nuclear Materials. 2015; 467:557 – 565. [5] Liu D, Gludovatz B, S Barnard H, Kuball M, Robert O R. Damage tolerance of nuclear graphite at elevated temperatures. Nature Communications. 2017 6;8.

Speaker: Mr Ming Jiang (University of Bristol)

Slides RaDIATE_PPT_V5.pptx

15:15 Discussion

15:30 → 15:45 Coffee break

15:45 → 17:45 3rd Oral Session: Irradiation Facilities

Convener: Dr JOACHIM VOLLAIRE (CERN)

15:45 TRIUMF Irradiation Capabilities

TRIUMF had been operating high intensity proton beams at >100 µA and 480-500 MeV over 40 years for producing pion, muon, neutron, radioactive ion beams and medical isotopes. During this time many radiation damage effects have been observed and measured. The highest fluences are on the meson production targets at about 1023 protons/cm2per year. TRIUMF has several locations for proton irradiation studies and these will be described along with a few examples of radiation damage measurements.

Speaker: Dr Ewart Blackmore (TRIUMF)

Slides RADIATE_talk_ewb.pdf

16:10 BLIP 2020 Quality Assurance Trial Irradiation

The RaDIATE collaboration recently completed a two-phase material irradiation experiment at the Brookhaven Linac Isotope Producer facility at Brookhaven National Laboratory. Various materials of different grades were encapsulated in stainless steel capsules and bombarded with 181 MeV protons for a period of up to eight weeks. However, upon completion of the irradiation campaign, three out of nine capsules were observed to have been breached at the weld line, thus compromising the enclosed material specimens and irradiation parameters. Potential contributing factors to the capsule failures have been identified and are currently under investigation. Computational Fluid Dynamics (CFD) simulations are under way to examine flow characteristics around the capsules to determine whether the capsules overheated due to inadequate cooling. Thermo-mechanical Finite Element Analysis (FEA) of the capsules to explore whether beam offsets could have increased the heat deposition and stresses near the weld line is also in progress. Furthermore, improved weld designs and welding procedures are being developed to ensure a more robust capsule design. This talk will cover the ongoing efforts to better design and perform future long-term irradiation campaigns at BLIP, as well as plans to execute a quality assurance trial irradiation at the facility next year.

Speaker: Dr Kavin Ammigan (Fermilab)

Slides BLIP2020_QA_-_RaDIATE_CM_2019.pptx

16:35 Ideal Accelerator Target Irradiation Facility

Speaker: Mr Patrick Hurh (Fermi National Accelerator Laboratory)

Slides Ideal_Irradiation_Facility_-_Hurh_v2.pptx IntroMCcodes_RaDIATE6_mokhov_Dec2019.pdf

17:00 Discussion: Ideal Accelerator Target Irradiation Facility

17:45 → 19:45 Welcome event

Tuesday, 10 December

09:00 → 11:00 4th Oral session: Radiation Damage Studies I

Convener: Dr Slava Kuksenko (United Kingdom Atomic Energy Authority)

09:00 Measurement of displacement cross section in J-PARC for proton kinematic energy range from 0.4 GeV to 30 GeV

For damage estimation of structural materials in the accelerator facility, displacement per atom (DPA) is widely employed as an index of the damage calculated based on the displacement cross section obtained with the calculation model. Although the DPA is employed as the standard index of material damage, the experimental data of displacement cross section are scarce for a proton in the energy region above 20 MeV. Among the calculation models, the difference about 8 times exists for tungsten so that experimental data of the displacement cross section is crucial. To obtain the displacement cross section, which can be obtained by the change of resistivity of the sample under irradiated with proton with cryogenic temperature, we have started the experiment in J-PARC to measure the displacement cross section between 0.4 and 3 GeV. As a preliminary result, the displacement cross-section of copper was successfully obtained for 3-GeV proton. The present results showed that the widely utilized Norgertt-Robinson-Torrens (NRT) model overestimates the cross section about 3 times, as suggested by the previous experiment in the lower energy region. It is also found that the calculation with a recently proposed athermal recombination-corrected (arc) model by Nordlund et al. shows remarkably good agreement with the present data.

Speaker: Dr Shin-ichiro Meigo (J-PARC/JAEA)

Slides Meigo_RaDIATE2019.pptx

09:25 Fatigue Performance of Proton Irradiated Ti6Al4V Alloy

Titanium alloy Ti6Al4V currently used in beam windows in accelerator facilities are subjected to thermal stresses and high cycle fatigue loading due to intense pulsed proton beam. There materials interacting with beam will also undergo various radiation damage which will affect their endurance limit. Till now there is no fatigue data available for high energy proton irradiated titanium alloy. In this study we carried out fatigue test on proton irradiated Ti6Al4V using a custom-made fatigue tester. The samples are irradiated with 180 MeV proton beam at Brookhaven National Lab to receive upto 0.25 DPA. Two different grades of Titanium alloy, Grade 5 and Grade 23, with different levels beta-phases are fatigue tested and compared with unirradiated samples.

Speaker: Dr Sujit Bidhar (Fermi National Accelerator Lab)

Slides Titanium-Fatigue.pptx

Video fatigue.mp4

09:50 Status of Post Irradiation Examinations of the RaDIATE CERN2 capsule

The contribution will provide a status report of the Post Irradiation Examination of the RaDIATE-sponsored CERN2 capsule. The PIE will focus on the Mo-coated samples (MoGR and CfC), including microscopy analysis as well as coating adhesion. Perspectives on the schedule as well as on the other samples will be provided.

Speaker: Mr Nicola Solieri (CERN)

Slides Radiate_collaboration_meeting_-_NSV1.pptx

10:15 In situ tensile testing and electron backscatter diffraction characterization of irradiated 316L from Spallation Neutron Source Targets 8 and 9

Tensile testing of material from the Spallation Neutron Source (SNS) Target 2 showed abnormally large ductility for a specimen irradiated to approximately 5.4 displacements per atom (dpa). Subsequent electron backscatter diffraction (EBSD) characterization of these tested Target 2 specimens showed deformation-wave behavior from transformation-induced plasticity was responsible for the large ductility values observed. To study the deformation behavior of the target material after irradiation, relatively small “micro” tensile specimens were fabricated from material removed from SNS Targets 8 and 9, which were irradiated to approximately 7 dpa. In situ tensile testing of these specimens and unirradiated reference material was performed in a scanning electron microscope equipped with an EBSD detector system. EBSD maps were captured during different stages of each test to characterize the deformation mechanism(s) occurring during testing. This presentation will review the initial results from these tests and discuss future work for the SNS PIE program.

Speaker: David McClintock (Oak Ridge National Laboratory)

10:40 Discussion

11:00 → 11:30 Coffee break

11:30 → 13:30 5th oral session: Radiation Damage Studies II

Convener: Dr Marco Calviani (CERN)

11:30 Status of Ion Beam Irradiation at HIT Facility

An optical transmission radiation (OTR) foil as beam monitor, which is Ti-15V-3Cr-3Al-3Sn alloy with 0.05 mm in thickness, used in the J-PARC neutrino facility was examined for the irradiation damage analysis in the Pacific Northwest National Laboratory under the RaDIATE collaboration. The foil was irradiated by 30 GeV proton beam with 1.4x10^20 POT. The foil microstructures of β-phase Ti-15-3-3-3 alloy had very high densities of nano size clusters of omega phase and α’’ phases before the irradiation, and these phases were relatively stable after the irradiation. It was also found to be very low density of defect clusters formed by irradiation about 0.06 dpa. The result can suggest that Ti-15-3-3-3 alloy may have a high resistance for radiation damage. The correlations of radiation hardening measurement method from cm-scale to nano-scale can be given by tensile tests, Vickers hardness, and nano-indentation tests. From the data of tensile test and Vickers hardness test, it can be evaluated to be σy≒3 Hv, and from Vickers hardness test and nano-hardness test, it can be evaluated to be Hv≒60×Hm. Low energy ion irradiations such as HIT (High Fluence Irradiation Facility of The University of Tokyo) ion experiments are very useful in the evaluation of high DPA irradiation hardening behavior. The main objectives of this study in the HIT ion beam experiments are (1) to support for the evaluation and analysis of radiation damage induced by high energy proton irradiations, (2) to obtain the estimation of irradiation hardening behaviors in high DPA and DPA dependency of the materials, and (3) to evaluate the materials selection for higher radiation damage resistance. In the tandetron accelerator of HIT facility in the University of Tokyo, Fe^2+ ions with an energy of 2.8 MeV were irradiated to specimens under a displacement damage rate of about 8.4x10^-4 dpa/sec to 1 dpa, 5 dpa, and 10 dpa. The specimens of Ti-15-3-3-3 (metastable β-alloy, solution treatment, not aged (ST)), Ti-15-3-3-3 (metastable β-alloy, solution treatment and aged (STA)), Ti-6V-4Al with α+β phases annealed (A), Ti-64 with α+β phases heat-treated with STA (WQ+Aging), and TFGR (Toughened Fine-Grained Recrystallized) tungsten were used for the experiments. After the irradiation, the nano hardness was examined by Shimazu- DUH-211S type nano indentation testing. As preliminary results, nano-hardness data of Ti-64 A, Ti-15-3-3-3 ST, and Ti-15-3-3-3 STA irradiated to 10 dpa at RT were obtained. The radiation hardening of these Ti-15-3-3-3 alloys were smaller than Ti-64 alloy. Especially, Ti-15-3-3-3 ST was hardly increased by the irradiation. DPA nano-hardness dependence from 1 to 10 dpa will be measured, and the correlation between the BLIP data and the HIT data is under examining. Further experiments and these data analysis of HIT experiments will be performed in 2020.

Speaker: Dr Eiichi Wakai

Slides HIT-Irradiation-Experiments(wakai)-r3a.pdf

11:55 Blisters study in tungsten irradiated by MeV protons: Fracture morphology and mechanical properties

Proton irradiation damage is a common problem in structural materials at accelerators and nuclear fusion reactors. This damage may result in the degradation of the mechanical properties of structural materials and jeopardize the safe operation of nuclear facilities. Tungsten and tungsten alloys are utilized as building blocks of nuclear facilities, due to their excellent mechanical and thermal properties. Nevertheless, tungsten may also suffer from blister erosion due to proton irradiation. The choice of tungsten as material for the divertor in ITER (future thermal reactor) led to an increase in the number of studies on blister formation and hydrogen retention in tungsten in the last two decades. Most of the studies focus on low energy protons, up to several keV’s and on hydrogen plasma interaction with tungsten. Irradiation by low energy protons is characterized by shallow implantation depths, high sputtering yield and low irradiation temperatures. In spite of the extensive research carried out on the evolved damage due to irradiation by keV protons\deuterium ions, the mechanism of blisters formation and growth in tungsten remains not well understood. In contrast, under MeV proton irradiation the evolving damage should differ from that from keV protons due to deeper penetration depths, lower sputtering and higher irradiation temperatures. These differences are expected to affect the blister formation and growth processes and their analysis should contribute to improving our understanding. In this study, we investigated the evolution of irradiation damage in tungsten by high energy protons (MeV’s) at several fluxes and temperatures, to obtain a better understanding of the mechanism of blister formation and growth during irradiation. A cooled target cell was designed and built to allow ambient temperature irradiation experiments. Single and polycrystalline tungsten samples were irradiated with 2.2 MeV protons at Soreq Applied Research Accelerator Facility (SARAF). Hydrogen blisters were obtained for both single crystal and polycrystalline samples. Blisters were formed at doses of the order of 1017 protons/cm2, which are below the reported keV critical threshold for blister formation. Large, well-developed blisters are observed, indicating that for MeV range protons the critical threshold is at least an order of magnitude lower than the lowest value reported previously. The effect of temperature and flux on the critical formation dose for blisters and on their dimensions was studied. It was found that for single crystals, the critical formation dose is one order of magnitude higher than for polycrystalline tungsten at high-temperature irradiation conditions. Upon reducing the irradiation temperature to ambient, the critical dose for the formation of blisters in single crystals was reduced by a factor of three, in contrast to polycrystalline tungsten where there was no significant change with temperature; thus indicating the role of grain boundaries in blister formation. Larger blisters were obtained in single crystals than in polycrystalline tungsten at ambient temperature conditions, identifying the grain boundaries as a preferential additional hydrogen trap. The height to area ratio of the blisters is found to be strongly temperature dependent and only weakly dependent on irradiation flux for both single and polycrystalline samples. The morphology of the irradiated samples was observed by examining cross-sections of blisters obtained by the use of a focused ion beam (FIB). The thickness of the blister cap was found to be in good agreement with the irradiating protons stopping range, regardless of sample structure, temperature or total dose. Increased curvature of the surfaces was observed with increased temperature for polycrystalline and single crystal blisters and was interpreted as increased ductility of the blister growth process. The ductility is more substantial in single crystal blisters, pointing to the role of grain boundaries in blisters growth mechanism. The cap of one blister was removed, exposing the inner fracture surface of a blister and supporting the validity of the cross-sectional observations. The mechanical properties in the vicinity of a blister formed in a single crystal sample were characterized by nano-indentation. The hardness near the irradiated surface was found to increase both in the vicinity of the blister and beyond. This observation suggests that the elevation of the blister cap does not cause significant strain hardening. For the blister cap, the hardness was found to increase with increasing depth from the irradiated surface, correlating with increased irradiation damage. Comparison with neutron irradiation hardening is presented.

Speaker: Mrs Inbal Gavish Segev (Soreq)

Slides 02_RaDiate_12_2019_8.12.pptx

12:20 Characterization of radiation damage effects in high-energy neutrino target graphite using low-energy ion irradiation

Neutrino targets are constantly irradiated by high-energy protons to produce secondary particles that decay into neutrinos. Over time, radiation damage effects the macroscopic physical and structural properties of target materials and result in shortened operation lifetimes. The resulting decrease in the material’s thermal shock resistance combined with greater embrittlement results in an increased chance of component failure. The DUNE experiment at LBNF calls for a 2+MW, 60-120 GeV pulsed proton beam which is expected to push targets and other beamline components to new levels of damage; therefore, it is vital to predict what macroscopic effects may result. However, directly studying material properties of targets exposed to high-energy proton accelerators is frequently unrealistic. This is due to both the high residual dose rate of samples and the high user costs associated with these facilities. Additionally, high-energy proton irradiations have the disadvantage of a very slow number of displacements per atom (DPA) accumulation rate, for instance samples irradiated at the Brookhaven Linac Isotope Producer (BLIP) accumulated just 0.11 DPA during a 55 day irradiation. This results in an extremely long time to reach the total accumulation levels expected for the DUNE experiment. A plan for determining equivalent low-energy ion irradiation conditions that will induce the same level of damage observed in previously failed targets and expected in future higher intensity targets has been initiated at FNAL. The specific advantages of ion irradiation over high-energy protons include high DPA/s resulting in short irradiation sessions, low operating costs, and no risk of sample activation. After graphite samples have been irradiated by low-energy ions, the post-irradiation-examination (PIE) results will then be compared to previous results obtained by members of the RaDIATE collaboration. This includes PIE work done on a failed NT-02 graphite target fin and on samples from high-energy irradiations performed at BLIP. The incident ions will be helium (He++) which has been chosen due to its combination of high damage rate and significant penetration depth as compared to protons/electrons and high-Z ions respectively. Irradiation by He++ ions at 5MeV is predicted to reach 1 DPA near the surface in only ≈30hrs allowing for much more rapid irradiation cycles resulting in more possible iterations of the experiment. PIE work on the irradiated graphite will focus on: DPA, swelling and lattice spacing changes, changes in mechanical stress, strain and embrittlement, and thermal properties. The proposed irradiation will be performed at the Michigan Ion Beam Laboratory (MIBL) at the University of Michigan utilizing the 1.7MV ”Maize” Tandem particle accelerator and costing roughly $100/hr. For future experiments helium ion implantation can also be performed at the same facility using a dedicated low-energy implanter allowing for simultaneous damage inducement and implantation.

Speaker: Mr Abraham Burleigh (Illinois Institute of Technology, Fermi National Accelerator Laboratory)

Slides A_Burleigh_TRIUMF_pres.pdf

12:45 Experimental investigation of radiation damage effects in beryllium: updates on recent results obtained on proton, neutron and He-ions irradiated samples

Beryllium is an essential material for target components material in the currently running (NuMI) and near-future multi-megawatt accelerator particle sources (LBNF), reflectors and moderators in material testing nuclear reactors, plasma facing material (JET, ITER) and potential neutron multiplier (DEMO) for fusion reactor designs, and it is under extensive investigation by fission, fusion reactors and proton accelerator facilities communities. The presentation gives an overview of the recent results obtained in the Materials Research Facility of the UKAEA on beryllium samples: • exposed to high energy protons in the NuMI beamline at 50ºC (maximum dose 0.5 dpa, 2000 appm of helium transmutant); • after helium implantation at 50ºC and 200ºC (0.1 dpa, 2000 appm of helium); • after neutron irradiation at different DEMO relevant conditions during HIDOBE-2 campaign in the HFR and investigated within the collaboration with Karlsruhe Institute of Technology (Germany). • after thermal-shock experiments in the HiRadMat facility. The main part of the paper will be devoted to the micromechanical tests results obtained using nanoindentation hardness measurements and microcantilevers fracture tests. The local properties data will be analyzed in combination with observed microstructural changes. The presentation will also give an overview of the future plans.

Speaker: Dr Slava Kuksenko (United Kingdom Atomic Energy Authority)

Slides RaDIATE_Triumph_2019.pptx

13:10 Discussion

13:30 → 14:30 Lunch break

14:30 → 17:00 TRIUMF Tour

17:00 → 19:00 Poster session

Convener: Mr Patrick Hurh (Fermi National Accelerator Laboratory)

17:00 ARIEL Quick Disconnect Service Tray: Design for High Radiation

The primary function of the TRIUMF’s new Advanced Rare IsotopE Laboratory (ARIEL) is to produce and deliver radioactive ion beams to experiments though two separate target stations. The ARIEL Electron Target East (AETE) station will be used to enable the impinging of an electron driver beam for the production of exotic isotopes and to facilitate their extraction, ionization and acceleration into a radioactive ion beam. The AETE module requires several services to complete this, including power, air, gas, water, sensors and vacuum. However, due to shielding requirements, it is not possible to deliver these services directly to the target module; instead a feedthrough was developed to transport them from the top of the module to a quick-disconnect ground service tray below. This project focuses on the design of the ground service tray & components from the bottom of the feedthrough to the target module. Theoretical radiation mapping shows an expected does of 1x105Gy/hr and with a 30-year lifecycle gives a design limit of 1.2x1010Gy. This high dose of radiation limits material and component selection and requires that any maintenance be done in a hot-cell. Vacuum Coupling Radiation (VCR) fittings were chosen for between the connection plate and feedthrough as only metal sealing components can be used. Aluminum was chosen for the support structure and busbars for both weight and activation. Any insulators must be either Macor or Aluminium Nitride and transportation of water, air, and gas along the service chase is done through flexible stainless-steel braided hose. Hot-cell operations prove to be challenging due to the complexity and accessibility of the service tray, and decommissioning of the assembly means that every piece must be accessible and able to fit into a standard 55Gallon drum. Several custom tools have been developed including, pincer extensions (to engage Swagelok fittings) and a pivoting wrench (to meet torque requirements). A lifting mechanism to engage/disengage the service tray is still under development. In the next stage of development, a test stand will be used in a hot-cell to validate tooling and identify new challenges.

Speaker: Mr Mathew Brownell (TRIUMF)

Slides

• poster_in_slide.pptx
• Poster_-_RaDIATE.pdf
• slam_session.pptx

17:00 Cyanate ester insulation for the ARIEL target modules high voltage feedthrough

Fibre-reinforced cyanate ester resin-based composites have been studied and used for applications in high radiation environments such as electrical insulation for magnet coils. Here we explore the composite’s planned use in a unique, large-scale high voltage insulation application; the high voltage feedthrough (HVFT) for the ARIEL target modules. To be discussed are physical properties and characteristics of the composite relevant to the HVFT, in addition to associated technical challenges and risks.

Speaker: Alexander Shkuratoff (TRIUMF)

17:00 High Emissivity Micro-machining for Increased Emissivity of Tantalum ISOL Target Containers

TRIUMF’s Advanced Rare IsotopE Laboratory (ARIEL) requires a new design of an ISOL target container that approaches an emissivity (ε) of 1, as is achieved at ISAC via cooling fins [1]. ARIEL’s new target geometry precludes the use of cooling fins as a viable option for heat dissipation, leading to exploration of other high-emissivity options. Small-scale (µm) surface modification is considered as a way to increase the emissivity [2,3,4]. Simulations were constructed using COMSOL Multiphysics to mimic basic reflectance measurement results from literature; the same model was then used to simulate tantalum micro-geometry surface structures and report the average reflectance. Geometries were found that increased the emissivity by greater than Δε = 0.5 in a select wavelength band. Test pieces have been designed and will be used to validate the results of the simulations as well as explore the survival of the structure at ≈ 2500 K.

Speaker: Ms Cassidy Donaldson (TRIUMF)

17:00 High voltage breakdown studies under the influence of radiation fields

The ARIEL facility at TRIUMF will add two new state-of-the-art target stations to produce radioactive ion beams using the Isotope Separation On-Line (ISOL) method. In the ISOL method, a driver beam impinges a target material creating radionuclides that are ionized and extracted with a high electric field. The driver beam and target interaction cause radiation fields of around $10^9$ Gy/h that in turn affect the breakdown strength of the gas used for cooling the target station. To guarantee reliable operation, it is mandatory to assess the effect of such radiation levels on the gas breakdown strength. For this, a spark gap has been employed and a clear decrease is observed at low radiation levels. More experiments are envisioned to map the breakdown strength at levels similar to the ones expected online.

Speaker: Mr Fernando Alejandro Maldonado Millan (UVIC/TRIUMF)

17:00 Incorporation of np-SiC into polyacrylonitrile (PAN) using electrospinning

Since the first discovery of a radioactive elements, expending the chart of nuclide has been essential for the fundamental of nuclear physic research and for many other disciplines including medicine. One common method to produce radioactive ion beams is using the Isotope Separation On-line technique in which target materials are irradiated with proton driver beams. The common materials for isotope production targets are refractory materials which combine short diffusion paths and high temperature resistively needed to promote the release efficiencies. However, the inevitable sintering process has a negative impact on short-lived isotopes due to grain growth and removal of pores, thus reducing the release efficiencies. Fabrication of nanofibrous target materials is a promising way to improve the RIB intensities for such high demand short-lived radioisotopes. Nano-SiC fibres have been successfully developed and are able to be operated at high temperature with the preservation of the nanostructures.

Speaker: Mr John Wong (TRIUMF)

17:00 ISAC Target Ion Source Assembly & Manufacturing

Presentation of the various ISAC target ion sources used for the production of Radioactive Ion Beams at TRIUMF along with assembly methods, a quick overview of the SIS (Surface Ion Source) , FEBIAD (Forced Electron Beam Induced Discharge), & IG-LIS (Ion Guide Laser Ion Source) target ion sources, historical data and quality checks & parameters.

Speaker: Mr Aaron Schmidt (TRIUMF)

17:00 ISAC Target Material Production

Radioactive Ion Beam demand often centers around specificity and yield. This has made it necessary for TRIUMF to develop methods for the production of an array of Targets using materials that can best tailor the particular beam and yield demand. An overview of various ISAC target materials, their current processing methods and quality assurance methodology, as well as some historical data, will be presented.

Speaker: Mr Darwin Ortiz Rosales (TRIUMF)

17:00 LightHouse Isotopes: Challenges in the target environment of a 3 MW electron accelerator

The broad applicability of the gamma-decay of Tc-99m for diagnostic imaging makes it the most widely used medical isotope with forty million patients each year. Due to its short half-life of 6 h, it is produced directly in the hospitals utilizing the decay of Mo-99 to Tc-99m with a half-life of 66 hours. The world-wide demand of Mo-99 is currently provided by neutron-bombardment of highly purified U-235 in a few aging reactors. The bombardment of Mo-100 with high-energy electrons can also produce the desired Mo-99 in a much cleaner way that does not require a fission reactor and enriched U-235. In order to reach Mo-99 concentrations that are sufficient, however, the electron beam intensity has to be very high (40 mA at 75 MeV in the LightHouse Isotopes concept). Here we will discuss some of the challenges that result from the associated high heat load (3 MW energy input) and damage rates (~ 1 dpa/day) for the design and operation of a molybdenum target and its environment. In particular, we focus on the assessment and testing of the degradation of target material and its support structures upon irradiation. The aim is to produce a target chamber that can withstand this hostile environment for prolonged time to reliably supply the world with ‘clean’ Mo-99.

Speaker: Dr Johannes Jobst (Demcon Advanced Mechatronics)

17:00 Macroscopic and microscopic post-irradiation characterization and analysis capabilities at BNL

The array of post-radiation capabilities at BNL that link campaigns at its irradiation facilities (200 MeV Linac/BLIP and Tandem van de Graaff) with characterization of the effects in both the microstructure and the macrostructure will be presented. Emphasis will be given to the recently achieved Brookhaven, due to decades-long continuous operation of medical isotope production augmented with proton and spallation-based fast neutron irradiation studies of particle accelerator and nuclear materials, has maintained the handling and characterization capabilities of highly radioactive materials. Specifically, capabilities within the BNL hot cell laboratory, essential for nuclear material studies, include photon spectra and isotopic analysis using high-sensitivity detectors, radioactivity measurements and high precision weight loss or gain assessment. Macroscopic post-irradiation characterization within the hot cell laboratory is supported by the following capabilities: • Mechanical post-irradiation behavior consisting of tension-compression, 3-point and 4-point bending analysis. • Evaluation of thermal expansion including thermal annealing of irradiated samples • Thermal conductivity based on 4-point electrical resistivity measurements • Magnetic Whole probe • Ultrasonic measurements of irradiation-induced degradation of material modulus Microscopic Analyses: For microscopic, post-irradiation characterization of heavily irradiated materials relied over the years on the high energy X-rays of its synchrotrons, NSLS (now decommissioned) and now NSLS-II (world’s brightest light source). High energy X-rays at the BNL synchrotrons, and in particular the XPD (and future HEX that is currently under construction) beamlines at NSLS II, offer a path in establishing this important connection between micro-scale effects and physical properties of novel materials exposed to high radiation fluxes. Multiple X-ray techniques – XRD, EDXRD, SAXRD, XAS, X-ray Tomography (XPD, HEX), X-ray Imaging (HEX beamline currently under construction) have been commissioned and utilized extensively to-date to micro-characterize proton and fast neutron irradiated materials for several accelerator and reactor initiatives. Such capabilities include in-situ complex state of stress and various environments: • Multi-directional complex stress (pure bending, tension, compression, twisting) • Stress intensity/fracture toughness facilitated by high energy X-ray micro-beams recently achieved at NSLS II XPD beam • Creep (experimental set-up is under preparation/commissioning at NSLS-II • High-temperature effects, irradiation annealing with simultaneous characterization • Corrosive environments • X-ray tomography of irradiated materials (upcoming commissioning experiment) Characterization of the microstructure under extreme temperatures (currently on unirradiated materials) is provided by Center of Functional Nanomaterials (CFN) for electron microscopy (TEM, SEM, EDS), thermal analysis (DSC, TGA). In coordination with CFN, plans are being evaluated to enhance the hot cell laboratory (Target Processing Laboratory) with electron microscopy which will, in combination with the micro-characterization techniques at NSLS-II based on high-energy X-rays provide a complete PIE. Characterization of select, relevant irradiated materials of interest to the particle accelerator and reactor materials communities will be presented.

Speaker: Dr Dohyun Kim (Brookhaven National Laboratory)

17:00 Procedure for the SEM analysis of irradiated target material.

For the production of radioactive ion beams with the ISOL method, a target material is irradiated with a high energy driver beam that induces nuclear reactions and produces isotopes. This process consequently leads to the deterioration of the target material. The characterization of post irradiated target materials provides information about the level of sintering the target material suffers during irradiation. Systematically observing the same type of material submitted to different irradiation conditions will allow the development of materials with greater endurance. In contrast with other laboratories were the scanning electron microscope (SEM) is in their shielded nuclear radiation containment chambers, in TRIUMF, the SEM is in a separated room. At TRIUMF we observe different target materials previous irradiation with the in house SEM, therefore to use the same SEM to analyze pos irradiated target material it is crucial to guaranty the safety of not only the personnel during the analysis of the irradiated target materials but also the safety of the already established SEM users. That is why a procedure for the analysis of target materials is being developed. The procedure for the analysis of the material includes the retrieval of the irradiated target material, its transportation from the shielded nuclear radiation containment chambers to the SEM room, and it also comprehends the installation of the sample in the SEM. Additionally, the procedure covers the disposing of the sample and the safety measurements in case of contamination. Implementing this procedure as part of the target quality control will provide the baseline data for the synthesis of tailored target materials with enhanced isotope diffusion.

Speaker: Ms Marla Cervantes Smith (TRIUMF/UVIC)

17:00 Radiation resistance studies on vacuum seals

In the pursuit of increased research capacity, TRIUMF is constructing the Advanced Rare Isotope Laboratory (ARIEL), intended to multiply TRIUMF’s scientific output by a factor of 2-3. The ARIEL facility will provide two target stations, one driven by a proton beam and the other by an electron beam. The target stations use a modular design which requires actuated, radiation hard, high performance, reliable, and reusable vacuum seals, to interface the beam pipe between modules. TRIUMF has developed a novel solution to this unique challenge, which has been dubbed the Pillow Seal. The Pillow Seal’s purpose is to remotely, and reliably, connect vacuum space between removable modules. In addition, the expected dose rates may be as high as 10 MGy/hr within the target stations of ARIEL facility, requiring sealing solutions that do not consist of elastomers or rubbers. Due to the modular design of the target stations, limited space is available for sealing solutions, producing a challenge for the required clamping forces needed for metal seals. An investigation into the radiation hardness of Spring Energized PEEK seals is being conducted to evaluate them as a potential sealing solution.

Speaker: Mr Sam McEwen (TRIUMF)

17:00 Recirculating electron beam photo-converter for rare isotope production

The TRIUMF 30-75 MeV electron linac has the potential to provide cw beams of up to 0.5 MW to the ARIEL photo-fission facility for rare isotope science. Due to the cooling requirements, the use of a thick Bremsstrahlung target for electron to photon conversion is a difficult technical challenge in this intensity regime. Here, we present a different concept in which electrons are injected into a small storage ring where they make multiple passes through a thin internal photo-conversion target, exploiting an optimized energy range for production of gamma rays used for photonuclear reactions inside of a secondary target. The remaining energy is then deposited in a central core absorber, which can be independently cooled. We discuss design requirements and propose a set of design parameters for the Fixed Field Alternating Gradient (FFAG) ring. Using particle simulation models, we estimate various beam properties, and electron loss control.

Speaker: Aurelia Laxdal (TRIUMF)

17:00 Reliability Indexing Methods and their Application in Medical Isotope Targetry

Reliability indexing methods provide a means to combine explicit operational data with structural analysis techniques to better assess the ability of a design to undergo specific loading cases. Load variability can be assessed to add additional limits on the stresses components are able to handle, allowing for a more comprehensive estimate of operational life to be made. In design cases, this methodology can be combined with Kriging methods (Gaussian process regression) to minimize the number of Finite Element simulations required to converge on a given feature of a part.

Speaker: Mr Louis Moskven (TRIUMF)

17:00 Rotating proton beam onto TRIUMF ISAC targets

Two AC magnets were installed to scan the 500 MeV proton beam in a circular pattern on the TRIUMF ISAC target. Rotating a proton beam of reduced width on the ISAC targets contributed to a more homogeneous temperature distribution across the target and enabled the operation at a higher average temperature. Narrower beam rotation resulted in higher local power density, which enhanced the diffusions of isotopes; and an average power distributed over a larger surface area, resulted in less steep temperature gradients and enhanced the effusion of isotopes. Having the power deposition closer to the target walls, improved the heat dissipation and allowed for higher beam currents. Online tests have shown that we can increase the longevity of the target and the radioactive ion beams (RIB) yields while maintaining the same maximum temperature.

Speaker: Aurelia Laxdal (TRIUMF)

17:00 The ARIEL Proton Target West Irradiation Station

The TRIUMF ARIEL Proton Target West irradiation station will employ a 100 µA, 500 MeV proton beam to irradiate ISOL targets for the production of Radioactive Ion Beams. The APTW will combine the technical developments undertaken for the ARIEL Electron Target East irradiation station, with the developments and operational knowledge built up over the last 20 years of proton target irradiations at the TRIUMF ISAC facility. The design considerations and the current status of the APTW will be presented.

Speaker: Tom Day Goodacre (TRIUMF)

17:00 The ARIEL Symbiotic Target Module (ASTM)

TRIUMF is currently expanding its capacity for science by developing the Advanced Rare IsotopE Laboratory (ARIEL), an Isotope Separation On-Line (ISOL) facility utilizing 500 MeV proton and up to 50 MeV electron driver beams. The ARIEL Proton Target West (APTW) has been optimized for nuclear spallation reactions – with up to 20% of the proton driver beam being deposited in the ISOL target. Instead of immediately directing the beam to a copper dump, the remaining beam will be used to produce medical isotopes, in particular 225Ac. Thorium targets – comprised of discs weighing up to 1.5 kg total – will be hermetically sealed and irradiated immediately upstream of the APTW beam dump. This irradiation station will be housed within the ARIEL Symbiotic Target Module (ASTM), adhering to the modular design paradigm used in ARIEL. The target will then be rapidly transported via pneumatic transfer system to a hot cell for post processing and packaging. This design effort resulted in the definition of ASTM, including equipment for remote actuation, supply of cooling water to the target, and other infrastructure essential to of the medical isotope production.

Speaker: Mr Joshua Smith (TRIUMF)

17:00 Thermal transport in ISOL target materials

The ISOL method (Isotope Separation On-Line) is used worldwide to advance research in multiple fields, including medicine, astrophysics, materials science, and fundamental particle physics by producing radioactive isotopes. The nuclides of interest are created by directly irradiating a target material with accelerated particles. During operation, the target material must sustain temperatures around 2000°C while withstanding continuous thermal loads from interactions with the incident beam. The thermal limits of the target material restrict operation and target lifetime. Thermal properties are therefore of significant interest in target materials development. In this work, the thermal challenges facing ISOL target materials are discussed. The mechanisms of heat transport through target materials are studied and an off-line method is developed for studying target material thermal transport properties. The optimization of target material microstructures to enhance thermal transport is briefly discussed.

Speaker: Ms Mia Au (TRIUMF)

Wednesday, 11 December

09:00 → 11:00 6th Oral Session: Material Development

Convener: Dr Kavin Ammigan (Fermilab)

09:00 Developing ultra-strong and ultra-tough metallic materials with gradient nano-grained structures.

Controlling microstructural features in crystalline materials is one of the keys to achieving materials that combine mutually exclusive properties, such as strength and toughness. In this presentation, I will show the efforts made in my group to understand the generation of gradient nano-grained (GNG) structures in metallic materials under several manufacturing methods, including the impact of particles at high-velocities, and surface mechanical treatments. Specifically, I will show what are the main ingredients needed to achieve GNG in the high-velocity impact of particles, obtained directly from atomistic simulations. These results are compared with experimental works carried out in using laser impact techniques of Silver (Ag) microcubes. Our results suggest that the GNG transformation happens if three factors are present during the impact, i) large shock-wave stress, ii) at least eight slip systems are available to accommodate plastic deformation and iii) the kinetic energy is large enough to produce severe plastic deformation. Possible application of GNG materials under radiation environment will be also discussed in the presentation.

Speaker: Prof. Mauricio Ponga (The University of British Columbia)

Slides Ponga_GNG_materials_Radiate.pdf

09:25 PRESENT STATUS OF DEVELOPMENT FOR TUNGSTEN ALLOY, TFGR W-1.1%TiC, AS ADVANCED TARGET MATERIAL

J-PARC (Japan Proton Accelerator Research Complex) consists of a series of world-class proton accelerators and the experimental facilities that make use of the high-intensity proton beams. Recently, higher intense proton beams are requested due to requirement of further physics research. However, the upgrade of the intensity is dominated by the target technologies. Tungsten (W) is a principal candidate as proton-accelerator target material because of its high density (19.3 g/cm3) and extremely high melting point (3420ºC). Actually, a W target is considered to be used in the upcoming projects such as COMET Phase 2 and MLF 2nd Target Station at J-PARC, Mu2e at Fermilab, SNS 2nd Target Station at ORNL, and neutron target at ESS. However, W is known to exhibit significant embrittlement by recrystallization (recrystallization embrittlement) and by irradiation (irradiation embrittlement). Extensive efforts have been made to develop embrittlement tolerant W materials and TFGR (Toughened, Fine Grained, Recrystallized) W-1.1%TiC has been considered as a realized solution to the embrittlement problems. TFGR W-1.1%TiC exhibits grain boundary reinforced nanostructures containing a high density of effective sinks for irradiation-induced point defects, a DBTT (Ductile-to-Brittle Transition Temperature) down to around RT and enhanced resistances against surface damages by thermal shock/fatigue in the recrystallized state. We initiated to fabricate TFGR W-1.1%TiC and/or more improved W materials with sufficient dimensions for the target applications and investigate their feasibility as the target materials in 2016. While applying for budget acquisition to embody and integrate the W alloy fabrication processes, we are in the stage of producing TFGR W-1.1%TiC samples successfully with the size of about 20 mm in diameter and about 3 mm in thickness. Gradually, the performance of the TFGR-W1.1%TiC has been upgraded. The presentation will address our methodology to surmount the shortcomings of the conventional W materials and focus on prospective outcomes from the applications of the TFGR W alloys to proton-accelerator targets. This program has been supported by KEK-MTC collaboration since 2016, the Joint Usage/Research Center PRIUS, Ehime University, Japan, and JSPS KAKENHI Grant Number19H01913.

Speaker: Mr Shunsuke Makimura (KEK, J-PARC)

Slides RADIATE_SHMakimura_for_distribution.pdf

09:50 Exploration of High-Entropy Alloys for Irradiation Applications

High-entropy alloys (HEAs) have become the focus of research in many fields often exhibiting unique thermal, mechanical, chemical, and electrical properties. In addition to this, several HEAs have been shown, in both modeling and experiments, to exhibit enhanced resistance to radiation damage. While several theories have been proposed to explain this behavior, often owing to the chemical complexity and diffusion properties of HEAs, such theories require substantial experimental study over a range of HEA composition to develop a fundamental understanding. To accelerate the development of HEAs for irradiation applications, among others, researchers at the University of Wisconsin-Madison are employing high-throughput (HTP) techniques for synthesizing, testing, and characterizing arrays of different HEA compositions. These HTP techniques are then coupled with both traditional and in situ irradiation experiments and characterization methods, which add depth to the HEA development process and further the ability to link atomic-scale features with macroscopic properties.

Speaker: Michael Moorehead (University of Wisconsin-Madison)

Slides 191211_RaDIATE_MM.pptx

10:15 AN EXPLORATORY PRODUCTION OF TITANIUM-BASED OXIDE DISPERSION-STRENGTHENED ALLOY MATERIAL

An &alpha+&beta dual-phase titanium alloy Ti-6Al-4V (ASTM Grade 5 or its Extra Low Interstitial grade 23) is widely utilized as the beam window material for high-intensity particle accelerators, because of its low density and high specific strength. However, it is known that proton beam irradiation with only 0.1 dpa-NRT rapidly initiates radiation-induced hardening and loss of ductility. High-intensity beam penetration (order of 10^14 protons-per-pulse) through the beam window in the area of a few tens of mm^2 area causes a few hundred MPa compressive stress, and initiates propagation of shock waves in a few microsecond cycle. Resultant high cycle fatigue can lead to failure of the radiation-embrittled beam window in a very short time scale. There are indications that single-HCP phase &alpha-Ti alloys, such as Grade-6 Ti-5Al-2.5Sn, provide preferable ductility compared to the &alpha+&beta dual phase Ti-6Al-4V. Recent work by some of the authors indicates that this is due to radiation induced &omega-embrittlement that occurs only in the &beta phase [1]. If improved radiation tolerance of the single &alpha-phase alloy is realized, it can be adopted as the beam window material in future accelerators with upgraded power, which should bear damage levels of one to a few dpa-NRT within one year operation. It may also be attractive for certain components in fusion reactors. In order to improve the tolerance against radiation embrittlement of titanium alloys, we firstly try an oxide dispersion-strengthen (ODS) approach on titanium, which developed in other alloy systems for fusion material science based on Fe, V, Cu etc. To start with, we utilize single &alpha-phase pure titanium as the simplest case. By following the method developed on pure vanadium by one of the authors[2], pure titanium powder with addition of ~2 wt-% yttrium is processed with mechanical alloying (MA). It aims to convert solute oxygen and nitrogen impurities, which are originally contained in the base powder (and will become harmful sources to decrease ductility), to form a large number of nano-scale precipitates, working as sink sites of radiation-induced defects. The MA process dissolves all added Y into the base Ti matrices. Subsequent thermo-mechanical treatments cause reactions between solute Y and O/N impurities, resulting in oxide (Y2O3) and nitride (YN) dispersed in the base Ti matrices as nano-scale precipitates. In this presentation, our exploratory productions of the ODS-titanium alloy, aiming to optimize the MA processing and thermomechanical treatments (such as sintering), will be reported. [1] “New Aspect of Radiation Damage Behavior on Titanium Alloys under High-Intensity Proton Beam Exposure”, T.Ishida, E.Wakai, A.Casella, D.Edwards, D.Senor et al, ICFRM-19, San Diego,U.S.A., Oct.29, 2019. [2] “Microstructure Control to Improve the Resistance to Radiation Embrittlement in Vanadium”, H.Kurishita et al., J. Nucl. Mater. 343 (2005) 318-324.

Speaker: Taku Ishida (J-PARC)

Slides 191211-ODSTi-v3.pdf

10:40 Discussion

11:00 → 11:30 Coffee break

11:30 → 13:00 7th Oral session: Radiation Damage Modeling

Convener: Prof. Mauricio Ponga (The University of British Columbia)

11:30 Computer Simulation of Radiation Damage in Materials

We present an overview of computer simulation methods used to study radiation damage from the atomic to the continuum scale. Within the framework of multiscale materials modeling, the study of irradiation damage and associated materials property degradation has required modifications tailored to the application. Particle irradiation damage in accelerator targets begins at the nanometer scale and its effects can be seen at the millimeter scale and beyond. Similarly, the effects of picosecond-scale processes manifest themselves after hours and even months of continued operation. The complex phenomena associated with energetic particle impact include charge transfer, heat transfer, atomic displacement, preferential sputtering, local chemical changes, melting, and phase transformations, such as amorphization and precipitation. Modeling of irradiated materials at different scales to provide a fundamental scientific understanding of radiation-induced changes in microstructure and properties will be discussed.

Speaker: Dr Ram Devanathan (Pacific Northwest National Laboratory)

Slides Presentation slides

11:55 Irradiation induced failure investigation of NT02 graphite target fin through numerical simulation

Some of the NT02 target fin made up of isotropic POCO graphite grade has developed crack and fractured after few years of operation. The highly energetic pulsed proton beam with small beam sigma would create thermal stress wave as well as radiation damage such as displacement damage, void formation, swelling, gas formation among few. A complex interaction of dynamic loading due to beam, material degradation due to irradiation are thought to have caused such failure. Here we present a numerical simulation to capture combined effect of swelling and dynamic effect of thermal stress wave due to beam heating, to explain the failure of target. An empirical formula has been developed to take into account swelling as a function of temperature and proton fluence and has been implemented in commercial finite element code. Extensive X-ray diffraction (XRD) are done on fractured surface to understand lattice parameter change due to irradiation and the parameters of the empirical model are adjusted accordingly. Simulation results show swelling plays a major role in elevating stress state in the material closer to failure strength while the pulsed beam heating introduces fatigue loading that would explain brittle fracture emanating from inside of the material and propagating outward. Such empirical formula can be used as a predictive tool to estimate the service life of future multi-megawatt neutrino targets and targets in other accelerator environments.

Speaker: Dr Sujit Bidhar (Fermi National Accelerator Lab)

Slides NT02-Swelling-sujit.pptx

12:20 Calculations of damage energy spectra of nuclear reaction products and plan for displacement damage cross section measurements using 120 GeV protons at FNAL

The displacement per atom (dpa) value is widely used for the index of radiation damage in materials under high energy proton irradiation. It is possible to calculate dpa values using the screened Coulomb scattering theory for incident proton-nucleus collisions and the nuclear reaction model for nuclear reaction product-nucleus collisions in the high-energy region (>10 MeV). For defect production, it is the number of recoils weighted by the damage energy produced in each recoil that is most important. This quantity is determined by “weighed” the recoil spectra by the damage energy produced in each recoil. However, the damage energy spectra have not been investigated yet for the proton energy range from several MeV to hundred GeV, where recoil is regarded as nuclear reaction product. The contribution of each nuclear reaction product to the total dpa cross section has not been studied yet, although many kinds of nuclear reaction products are produced by nuclear reactions with increasing incident proton energy. In this work, we calculated damage energy spectra and dpa cross sections of all nuclear reaction products under high energy proton irradiation on tungsten with the energy range from 10 MeV to 120 GeV using the Particle and Heavy Ion Transport code System (PHITS). The damage energy spectrum of target nucleus includes the nuclear elastic scattering component in the low-energy part and the nuclear inelastic scattering component in the high-energy part. The average damage energy of tungsten was 63.7 keV for 100 MeV proton, 76.9 keV for 400 MeV, 38.3 keV for 1 GeV and 28.7 keV for 10 GeV, respectively. The damage energy spectrum of others include inelastic component only. For example, the average damage energy of lutetium produced by inelastic scattering was 628 keV for 100 MeV proton, 895 keV for 400 MeV, 872 keV for 1 GeV, 637 keV for 10 GeV, and 587 keV for 120 GeV, respectively. Note that the damage energy to the lattice atom is always smaller than the kinetic energy of nuclear reaction products because electric energy lost is subtracted in the displacement model. The damage energy of nuclear reaction product increased with proton energy up to around 1 GeV, but it decreased slightly with incident proton energy above 1 GeV. On the other hands, the number of nuclear reaction products increased with proton energy. In consideration of the relationship between the damage energy and the number of nuclear reaction products, the total dpa cross section of tungsten increased with the proton energy range from 400 MeV to 1 GeV and be almost constant over 1 GeV. The experimental data of total dpa cross sections indicated same trend with calculated results for the proton energy below 2 GeV. In this presentation, we will also introduce our experimental plan for measurement of dpa cross sections with 120 GeV protons at Fermi National Accelerator Laboratory (FNAL).

Speaker: Yosuke Iwamoto (Japan Atomic Energy Agency)

Slides Radiate2019-1212-iwamoto.pptx

12:45 Discussion

13:00 → 14:00 Lunch break

14:00 → 15:30 Seminar: MC MonteCarlo

slides IntroMCcodes_RaDIATE6_mokhov_Dec2019.pdf

14:00 → 15:30 Seminar: RH Remote Handling

Convener: Grant Minor

slides RaDIATE_RemoteHandlingTutorial_11Dec2019_comp.pdf

14:00 → 15:30 Seminar: TEM

slides Transmission_Electron_Microscopy_of_Dislocations.pptx

15:30 → 15:45 Coffee break

15:45 → 17:15 Seminar: MC MonteCarlo

15:45 → 17:15 Seminar: RH Remote Handling

Convener: Grant Minor

15:45 → 17:15 Seminar: TEM

17:15 → 22:15 Conference dinner

Dinner in a local brewery downtown Vancouver

Thursday, 12 December

09:00 → 11:00 8th Oral Session: Other Irradiation Effects

Convener: Dr Yong Joong Lee (ESS)

09:00 Post irradiation Examination of a spent Antiproton Production Target

The current contribution will detail a Post Irradiation Examination (PIE) on a spent antiproton production target (AD-target), which has been irradiated for around 10 years in the AD machine. The iridium core is estimated to have been irradiated up to 5 DPAs. The cutting procedure has well as all the measurements executed on the samples will be discussed as well as the path forward to other studies as well as the complementarity with HiRadMat experiments.

Speaker: Dr Marco Calviani (CERN)

Slides Post Irradiation Examination of a spent Antiproton Production Target: summary of findings

09:25 Harvesting Experiments on Additive Manufactured Titanium Alloy Beam Stopper with Radiation Assisted Corrosion Impacts

In preparation for isotope harvesting with a water-filled beam dump at the Facility for Rare Isotope Beams (FRIB), a flowing-water target connected to an isotope harvesting water system has been created and used in preliminary experiments. The target shell was made with a Ti64 alloy through additive manufacturing to reflect the material that is planned for the FRIB beam dump. Experiments with this target have involved low-power irradiations for isotope harvesting with 40,48Ca and 78Kr beams at the National Superconducting Cyclotron Laboratory (NSCL). Recently, a higher-power durability test was performed at the University of Wisconsin-Madison Cyclotron Lab to measure the degradation rate of the target shell material under similar irradiation conditions as those expected at the NSCL and FRIB during isotope harvesting. The flowing-water target was irradiated for several hours with a 5-50 µA proton beam, slowly increasing the beam intensity over time. The 48Ti(p,n)48V reaction, which occurred in the front face of the target shell, was used to measure the degradation rate of the target material. During the irradiation, a small quantity of 48V accumulated in the water and on an anion exchange resin in the water system. This radiotracer indicated a degradation rate of the target wall thickness on the order of 1E-8 µm/J. The implications of this rate on the durability of the target material for isotope harvesting will be discussed.

Speaker: Mrs Emily Abel (Michigan State University)

Slides RaDIATE_presentation-EmilyAbel.pptx

09:50 The formation of radiolysis products during isotope harvesting with a flowing water target

The harvesting of rare isotopes at the National Superconducting Cyclotron Laboratory (NSCL) is accomplished by the deposition of heavy ion beams in a water filled beam blocker. With the dissipation of such large amounts of energy, not only a plethora of radionuclides is formed, radiolysis reactions are induced as well. The thereby created various radiolytic products can either react with each other, resulting in mutual annihilation, or escape into the bulk solution. In general, molecular products such as hydrogen peroxide, molecular oxygen and hydrogen exhibit longer life times and could potentially increase to considerable levels in open systems. In order to ensure adequate water conditions for isotope harvesting, knowledge about the behavior of these species is vital. This will become particularly significant when considering the intended utilization of an aqueous beam blocker at the upcoming Facility for Rare Isotope Beams (FRIB). In several exploratory experiments at the NSCL the formation of H2O2, H2 and O2 was investigated with heavy ion beams of low intensity. To mimic the conditions expected at FRIB, the water filled beam blocker was irradiated with a high intensity proton beam (5–50 μA) for several hours at the Cyclotron Research Laboratory at the University of Wisconsin–Madison. The formation of H2O2, H2 and O2 in the harvesting system’s water was calculated based on the applied beam power; however, the measured levels (max. 586 μM H2O2, 5.5% H2, 10 ppm dissolved O2) were considerably lower. Based on these observations, an aqueous phase reaction of hydrogen peroxide and hydrogen is rendered possible. Additionally, elevated water temperatures could be expected, which would influence the primary yields of both species. The current model would support the interaction of all radiolytically formed species, even though the volume of irradiated water (~40 L) was much larger compared to conventional aqueous cyclotron targets.

Speaker: Dr Katharina Domnanich (NSCL, MSU)

Slides 03_Radiate_4.pptx

10:15 Proton irradiation effects on the phase stability of (α+β) Ti-6Al-4V irradiated at BLIP using dilatometry and high energy X-ray diffraction techniques at the BNL synchrotrons

Several super-alloys in the mid-Z range have been explored as targets for pion production to enable high-intensity neutrino sources. These allows have included Inconel-718, super-Invar, the Gum multi-functional alloys and the α+β titanium alloy Ti-6Al-4V. In this presentation the phase stability of the Ti-6Al-4V following irradiation with 140 MeV protons at the Brookhaven Linac Isotope Producer (BLIP) is described.. Specifically, following two sequential irradiation phases with peak fluences of ~5x10^20 p/cm^2 along with post-irradiation annealing between irradiations, the influence of irradiation on the stability of α and β phases were studied using precision dilatometry. Subsequently, by using high energy X-rays at the BNL synchrotrons (NSLS and NSLS-II) along with Energy Dispersive X-Ray Diffraction (EDXRD) and X-Ray Diffraction (XRD) techniques (where the latter was augmented with a refined Rietveld analysis), the phase evolution of these materials was studied. In-situ stresses during X-ray diffraction were applied with both techniques to assess (a) the role of twinning in accommodating deformation in the hcp a phase of titanium and (b) the effect of strain on α/β phase content. These studies revealed (a) identifiable α to β transformations based on the thermal expansion coefficient evolution with temperature, (b) the influence of proton-irradiation on these transformations, (c) the appearance of the ω phase following proton irradiation, (d) a tension-compression asymmetry based on activation of the twinning mechanism, and (e) the influence of applied strain on α and β phase fraction. Further studies of Ti6Al4V samples, in both their as-received state and after proton irradiation, are planned as part of an upcoming NSLS-II experiment. This experiment will utilize X-ray tomography to study the impact of variations in the in-situ multi-dimensional stress state as enabled by a specially designed stage. First results from the experiment, including the capabilities/features of the experimental set-up at the NSLS-II XPD beamline for X-ray tomography and XRD on irradiated materials will also be shown.

Speaker: Dr Mark Palmer (Brookhaven National Laboratory)

Slides Ti6Al4V_BLIP_Radiate2019.pdf Ti6Al4V_BLIP_Radiate2019.pptx

10:40 Discussion

11:00 → 11:30 coffee break

11:30 → 13:00 9th Oral Session: Radiation Damage Studies III

Convener: Ewart Blackmore

11:30 Post-Irradiation Examination of Proton-Irradiated Ti-base Alloys

Currently titanium alloys are used as beam windows in several accelerator facilities due to favorable beam interaction properties, high tensile strength, and high fatigue strength. The T2K neutrino beam-line currently uses the alpha+beta alloy Ti-6Al-4V as the material for its primary beam window and target beam window. Planned upgrades to the accelerators to 1.3 MW will require pushing the windows closer to their operational limits. Likewise, the Long Baseline Neutrino Facility (LBNF) facility, under design for 1.2 MW primary proton beam power at Fermilab, is planning to use this Ti alloy as the downstream target containment beam window. However, relatively little is known on how this common Ti alloy is affected by high energy proton irradiation. Understanding these radiation damage effects on this Ti-base alloy and others will lead to accurate lifetime prediction, more robust multi-MW targets, and development of new materials to extend target lifetimes. The presentation will include the latest post-irradiation examination results on a variety of Ti-base alloy samples irradiated in the BLIP facility to three different fluences. Materials include different varieties of Ti-6Al-4V, Ti-3Al-2.5V, Ti-5Al-2.5Sn, and the beta-Ti alloy Ti-15V-3Cr-3Sn-3Al. Tensile test results will be discussed, including data at room temperature and 200°C. Microscopy will also be discussed, including results from SEM/EBSD and TEM. The SEM/EBSD results will be correlated to the extent possible with nanohardness measurements made via atomic force microscopy. Finally, updates will be provided on interactions with other laboratories including shipping irradiated fatigue samples to Fermilab and meso-scale fatigue foils to the Culham Centre for Fusion Energy.

Speaker: Dr David Senor (Pacific Northwest National Laboratory)

Slides Senor_-_Ti_PIE_Update.pdf

11:55 Post-Irradiation Examination of Proton-Irradiated Beryllium

Beryllium is currently of interest for use in beam-intercepting devices. As such, samples of multiple beryllium grades (PF-60, S-65F, S-200F, S-200FH, and ultra-high purity) were irradiated in the RaDIATE BLIP irradiation and subsequently shipped to PNNL for post irradiation examination. To date, dimensional measurements of irradiated samples and tensile tests of irradiated and unirradiated samples have been completed on two grades (PF-60 and S-65F). The tensile tests were completed at two different temperatures (room temperature and 300°C) and were used to determine ultimate tensile strength, uniform elongation, total elongation, and yield strength. Currently, preparations are being made for TEM examinations of these samples. Additionally, options for correlating EBSD to AFM thermal scans are being explored.

Speaker: Dr Andy Casella (PNNL)

12:20 Material irradiation and investigation capabilities at ISAC-TRIUMF

ISAC-TRIUMF operates targets under proton irradiation in the high-power regime of 50 kW to produce radioactive isotope beams using the ISOL method. During irradiation, high-energy protons passing through the ISOL target are available for studies of radiation damage in materials. Additionally, the existing hot-cell capabilities for the routine maintenance of target components allow immediate in-situ material characterization of highly activated samples as well as preparation of microscopic samples with dose rates that allow hands on material investigation. Future direct proton irradiations aim to qualify materials for use in components for accelerator, fusion and fission applications as well as to investigate the radiation resistance of novel promising materials. Notably, nanostructured materials have undergone increasing interest in the nuclear industry due to an increased number of structural boundaries (grain boundaries, layers, precipitates) resulting in an enhanced radiation resistance by point-defect recombination. Although such materials have had traditionally the drawbacks of reduced ductility and poor microstructural stability, recent stabilization and grain structuring techniques might have unlocked their use as high performing materials under radiation fields. The ongoing development of irradiation capabilities at ISAC-TRIUMF will be presented with the achievable proton and neutron fluxes, DPA rates and helium production.

Speaker: Mr Ferran Boix Pamies (TRIUMF)

Slides FBP_radiate.pptx

12:45 Discussion

13:00 → 14:00 Lunch break

14:00 → 14:45 Collaboration meetings: RaDIATE Collaboration Business

Convener: Mr Patrick Hurh (Fermi National Accelerator Laboratory)

slides Ideal_Irradiation_Facility_Rd_2_-_Hurh_v2-2.pptx

14:45 → 15:15 RaDIATE council meeting

Private meeting between the RaDIATE collaborators

15:15 → 15:30 Coffee break

15:30 → 16:00 Closing Plenary

slides 2019-12-09_RaDIATE_-_Closeout.pptx

Friday, 13 December

09:00 → 12:00 Ad hoc working meetings by arrangement