Speaker
Description
The Batch Mode Ion Source (BMIS) [1] at the Facility for Rare Isotope Beams (FRIB) has been in use since 2021 to provide long-lived and stable isotope beams of various elements for successful user experiments [2]. Its design is based on target-ion-source modules developed and employed at the ISOLDE frontends at CERN [3]. At FRIB, source samples of the desired isotope, which consist of the desired isotope distributed on a Ta foil, are placed into the resistively heated target container. BMIS allows standalone operation in FRIB’s stopped and reaccelerated beam areas, independent of and complementary to operations requiring the FRIB driver linac and FRIB’s gas stoppers. Samples of stable or near-stable isotopes can provide unique beams over many days, either to satisfy user requests or to provide pilot beams for reaccelerated stopped beams. A planned future application of a BMIS-type source is to provide beams of long-lived isotopes generated in FRIB’s emerging isotope harvesting program. Challenges of BMIS operation include handling at times toxic, high-dose radioactive sources and minimizing stable beam contamination. Preparing the appropriate chemical forms for beam production can be difficult as well, but allows modifying the compound for optimum release and transport to the ionizer, maximizing yield. This presentation will discuss experience gained in BMIS operations so far, with examples of newly developed beams, i.e., $^{44}$Ti, $^{59}$Ni, $^{99}$Tc, $^{120}$Te, $^{229}$Th, and $^{232}$Th.
Molecular beams of $^{229}$Th and $^{232}$Th are of high interest to research groups looking for physics beyond the Standard Model. Both were recently developed using ThCl$_4$ as the precursor, followed by reacting it with NF$_3$ gas inside the oven of BMIS. Details on the production of Th, ThF and ThO beams, successfully delivered for laser spectroscopy at FRIB’s BECOLA setup, will be presented. High rates of stable $^{120}$Te and radioactive $^{56}$Ni beams were produced for experiments at FRIB’s ReAccelerator (ReA). The development of $^{120}$Te led to a successful experiment after addressing safety challenges related to toxicity and the large quantities of material involved. In the case of $^{56}$Ni, elevated contamination levels of the isobaric $^{56}$Fe along with the short 6-day half-life added significant operational challenges. The production of $^{44}$Ti and $^{99}$Tc beams poses significant difficulties due to the chemical reactivity of these elements and the physical properties of corresponding compounds. Ongoing efforts to provide a Ti beam using TiO$_2$ and ilmenite (FeTiO$_3$) compounds on Ta and Zr foils in various inert gas environments, as well as a Tc beam using chemically homologous Re compounds in combination with Ir, Ru, and Rh foils will also be discussed.
[1] C. Sumithrarachchi et al., The new batch mode ion source for standalone operation at the facility for rare isotope beams (FRIB), Nuclear Instruments and Methods in Physics Research B541 (2023) 301304.
[2] Domnanich et al. Applied Radiation and Isotopes 200 (2023) 110958.
[3] R. Catherall et al.,The ISOLDE facility, Journal of Physics G 44 (9) (2017) 094002.
This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics and used resources of the Facility for Rare Isotope Beams (FRIB), which is a DOE Office of Science User Facility, operated by Michigan State University, under Award Number DE-SC0000661.
| Funding Agency | U.S. Department of Energy, Office of Science, Office of Nuclear Physics |
|---|---|
| Classification | Isotope production, target, and ion source techniques |
