Dorothea Schumann Isotope and Target Chemistry Paul Scherrer

Dorothea Schumann: : Isotope and Target Chemistry : : Paul Scherrer Institut Samples and Targets: Peanuts or Core Components? n_TOF collaboration meeting, 23. -24. 9. 2020

How important is the target? Basic nuclear physics Cosmo- and Geoscience Nuclear energy research Isotope and target production Nuclear medicine and radiopharmacy Superheavy element research A target or sample should • contain a sufficient amount of the desired isotope • without disturbing by-products • with well-known composition Nuclear astrophysics • in a suitable shape • be mechanically stable and Neither research production nor possible is without suitable samples and targets. easy to handle Transport of reaction products Z to chemical or physical separation device Beam x Target T Detector y; Z Data acquisition system Page 2

n-TOFs highest ranking papers (PRL) • 2004 U. Abbondanno et al. , 151 Sm(n, g) no info about sample origin • 2013 C. Lederer et al. , 63 Ni(n, g) sample from Los Alamos/Karlsruhe target preparation at PSI • 2016 M. Barbagallo et al. , 7 Be(n, a) sample produced at PSI targets produced at PSI • 2018 L. Damone et al. , 7 Be(n, p) sample produced at PSI targets produced at PSI • 2020 C. Guerrero et al. , 171 Tm(n, g) second irradiation at SARAF sample produced at ILL target produced at PSI Highly radioactive targets, 4 produced at PSI Page 3

Effort to produce a target: 7 Be 1. Development, test and validation of the separation of 7 Be from the cooling water Filter Hotcell for separation SINQ cooling loop Incell equipment Post. Doc 2 years; preparation, performance and reporting for every campaign: 2 -3 months, 2 -3 colleagues 2. Development and test of the target preparation method (droplet, electrodeposition) for 7 Be(n, a) reaction; target preparation and characterisation Electroplating 2 -3 months per target, 1 colleague 3. Delivery of 80 GBq to CERN ISOLDE for the implantation (7 Be(n, p) reaction) Vessel for 7 Be-solution ISOLDE oven Droplet machine evaporation of 80 GBq 7 Be(N 03)2 solution transfer to a walk-in hotcell package for shipping including shielding 26 colleagues from 5 departments Total effort (estimated): > 500 hours Page 4

Effort to produce a target: 171 Tm Separation columns Method development: 1 Post. Doc 6 months Ampoule crashing and heating device Sample and target preparation and characterisation 3 month 2 colleagues Molecular plating in plastic bag to avoid contamination Isolated 171 Tm fraction Consequences: Unclear whether the target was still intact after the SARAF irradiation simulations point on up to a factor 6 off due to geometry effect examination of all components target including backing dissolved, separation repeated new target prepared and characterised, experiment at SARAF repeated Target three years later 2 months 1 colleague Page 5

Conclusions and improvements Present situation • Production of radioactive targets is extremely time consuming. • Researchers are not aware of the effort needed for sample and target preparation. • Researchers are not aware of the problems when working with radioactive samples • PSI is running out of personell and cannot fulfill all requests. • What we need • Include target makers from the beginning into your planning. Example 94 Nb(n, g): A wire was irradiated at ILL, but the target should be a disc. To transfer radioactive samples in the desired form is much more complicated. • • Include a budget for target preparation into your proposal. Include a budget for disposal of used targets. Think about a storage of valuable radioactive targets for reuse. Build laboratory on site with a hotcell for target handling. Example 7 Be(n, p): It would have been easy to ship the 7 Be sample in the graphite cylinder with a 3 cm shielding (weight ca. 10 kg). We needed to shield and transport the entire ISOLDE oven (~1000 kg). Page 6

My thanks go to all former and present members of the Isotope and Target Chemistry Group at PSI, who contributed to sample and target preparation for n_TOF and other experiment groups. Page 7