Optimization of the stripper foil material and thickness

Optimization of the stripper foil material and thickness for the GF Felix Kröger, Günter Weber, Thomas Stöhlker Gamma Factory Meeting - CERN www. hi-jena. de

Overview § Stripping process § Charge exchange processes § Cross sections § § Calculation programs Stripping scenarios for Pb 80+ and Pb 81+ Stripper foil material & thickness Results for Pb 79+, Pb 80+ and Pb 81+ www. hi-jena. de 25. 03. 2019 GF Meeting – Felix Kröger

Stripper Foils Target foil free e- e- Stripped Projectile ion σionisation >> σcapture www. hi-jena. de 25. 03. 2019 GF Meeting – Felix Kröger 1/16

Cross sections Electron Capture Ionization REC Ionization NRC Pb 82+ on 13 Al at 5. 9 (Ge. V/u) www. hi-jena. de 25. 03. 2019 GF Meeting – Felix Kröger 2/16

Challenge: foil thickness Preliminary results Exact foil thickness yield Cross sections Equilibrium charge state distribution Balance rate equations Non-equilibrium charge Charge state distribution Preliminary results … Thickness & Material Beyond the required thickness to reach equilibrium www. hi-jena. de 25. 03. 2019 GF Meeting – Felix Kröger 3/16

Calculation programs § GLOBAL code, CHARGE code, … Limitations : the number of accounted charge states, ion energy range, and others § BREIT code BREIT = Balance Rate Equations of Ion Transportation Allows to overcome these limitations But: charge-exchange cross-sections have to be supplied by user www. hi-jena. de 25. 03. 2019 GF Meeting – Felix Kröger 4/16

Stripping Scenarios Up to now, usually completelty stripped ions have been stored at LHC Production of partially stripped ions 2 different stripping scenarios possible : § Low energy : GLOBAL § High energy : BREIT 5. 9 Ge. V/u 72. 2 Me. V/u Ion Source http: //te-epc-lpc. web. cern. ch/te-epc-lpc/machines/lhc/general. stm, 2017. www. hi-jena. de 25. 03. 2019 GF Meeting – Felix Kröger 5/16

Stripping Scenarios Preliminary results 72. 2 Me. V/u GLOBAL CHARGE/ BREIT www. hi-jena. de 25. 03. 2019 GF Meeting – Felix Kröger 6/16

Energy loss 72. 2 Me. V/u 5. 9 Ge. V/u • At higher energy E-loss and energy straggling are minimal www. hi-jena. de 25. 03. 2019 GF Meeting – Felix Kröger 7/16

Stripper foil material 22 Ti 29 Cu 74 W 13 Al 6 C Preliminary results www. hi-jena. de 25. 03. 2019 GF Meeting – Felix Kröger 8/16

Stripper foil thickness Preliminary results www. hi-jena. de 25. 03. 2019 GF Meeting – Felix Kröger 9/16

Proof-of-principle experiment § Testing 13 Al at beam time in 2018 Illustrations from: Picture from Witek Krasny and the Gamma Factory study group. www. hi-jena. de 25. 03. 2019 GF Meeting – Felix Kröger 10/16

Stripper foil thickness Preliminary results www. hi-jena. de 25. 03. 2019 GF Meeting – Felix Kröger 11/16

Benchmarking Preliminary results Variant 2 Variant 1 original www. hi-jena. de 25. 03. 2019 GF Meeting – Felix Kröger 12/16

Benchmarking G. Arduini et al. , Proceedings Preliminary results of the 5 th European Particle Accelerator Conference, 1996. www. hi-jena. de 25. 03. 2019 GF Meeting – Felix Kröger 13/16

Predictions for Pb 79+ G. Arduini et al. , Proceedings Preliminary results of the 5 th European Particle Accelerator Conference, 1996. Variant 1 Variant 2 55. 61 μm 71. 36 μm original 84. 33 μm max. yield of Pb 79+ expected www. hi-jena. de 25. 03. 2019 GF Meeting – Felix Kröger 14/16

Thickness probing § Usually used : movable frame for multiple foils & rc manipulator Empty target-wheel for 4 target foils. Target-wheel for 3 target foils after stripping. (illustrations: GSI/G. Otto) www. hi-jena. de 25. 03. 2019 GF Meeting – Felix Kröger 15/16

Thickness probing Target-ladder with 4 different carbon stripper foils before and after use. (Illustration: Barth, W. , et al. , "High Current U 40+ Operation in the GSI UNILAC. “ LINAC 2010, MOP 044 (2010): 154. )) www. hi-jena. de 25. 03. 2019 GF Meeting – Felix Kröger 16/16

Thank you for your attention! www. hi-jena. de 25. 03. 2019 GF Meeting – Felix Kröger