Speaker
Description
Separation of rare isotopes is of high relevance for a multitude of different applications ranging from the half-life determination of the cosmogenic radionuclide $^{53}$Mn for MeaNCoRN [1], over decay measurements of $^{55}$Fe for the EMPIR Prima-LTD project [2], $^{157}$Tb for studies of nuclear data at the PTB [3], the precise measurement of the decay spectrum of $^{163}$Ho for neutrino mass determination in the ECHo project [4], $^{226}$Ra as a primary $^{222}$Rn emanation standard for the PTB [5], to the use of actinide tracers in environmental sample analysis with accelerator mass spectrometry (AMS). At the 30 keV off-line RISIKO mass separator of the Johannes Gutenberg University in Mainz isotopically pure ion beams of radioisotopes of a multitude of elements can be produced via element-selective resonance ionization with subsequent mass separation in a 60° sector field magnet. These isotopically pure ion beams can then be implanted into target foils with low resputtering rates or focused onto micro absorbers with an area well below 1 mm$^2$.
In this contribution, the recent activities in the purification of radioisotopes will be presented. Based on the successful implantation of $^{55}$Fe into micro calorimeters [6] an extension of the program towards collection of actinide isotopes on target foils was started on $^{248}$Cm as tracer for environmental samples. In addition, the isotope separation and purification of $^{236}$Np is foreseen. In preparation of these separations the overall efficiencies at the RISIKO mass separator were determined for different actinides to be well above 10 % applying two-step laser ionization processes.
For accurate quantification of the separated sample amounts a new and improved Faraday cup design was developed and characterized over the accessible element range from Z = 13 to Z = 92. Comparative measurements between the traditional and the new Faraday cup design show a significantly underestimated ion current in the previously used Faraday cup design, caused primarily by field ionization of sputtered neutral particles. Low level analyses of the separated $^{248}$Cm sample by AMS at ANSTO, Sydney, Australia, validates the accuracy of the new Faraday cup design.
[1] R Dressler et al., J. Phys. G: Nucl. Part. Phys. 39 105201 (2012)
[2] M. Müller et al., Journal of Low Temperature Physics 214:263-271 (2024)
[3] J. Riffaud et al., Applied Radiation and Isotopes 211 (2024)
[4] L. Gastaldo et al., Eur. Phys. J. Spec. Top. 226, 1623-1694 (2017)
[5] F. Mertes et al., Applied Radiation and Isotopes 156 (2020)
[6] T. Niemeyer et al. Applied Radiation and Isotopes 218 (2025)
| Email address | rahasse@uni-mainz.de |
|---|---|
| Supervisor's Name | Klaus Wendt |
| Supervisor's email | kwendt@uni-mainz.de |
| Funding Agency | Federal Ministry of Education and Research (Germany) under project number 02NUK075B |
| Classification | Applications of radioactive ion beams |
