Prototype production and test Ionization Chamber Prototype production and test 채경육 kchae@skku.edu 성균관대학교 물리학과

Usage Stage 1 after the reaction target chamber - to detect heavy recoils (blocker) - to normalize beam currents F1 In-flight separation or Beam transport F0 F2 WF Stage 2 F3 Q-Q-WF-D (VAMOS-like spectrometer) at the end of KOBRA - beam current normalization - heavy recoils (after rejection) F4 F4

Conventional design • Long life using gas flowing system • Relatively easy to make and use • Easy to fabricate large area detectors • Reasonable energy resolution • Slow response → new design is required • beam current normalization • beam composition monitoring • detecting heavy recoils

New design: tilted electrodes, tilted window • Fast IC: NIM A 751, 6 (2014) Portable IC: JKPS 64, 516 (2014) • tilted window & electrodes perpendicular 76Ge, 76Se ~700,000 pps

Prototype • based on Fast IC design (ORNL) • distance between adjacent electrodes: 1 cm → Fast response time! • easy to replace window • entrance window: gauge 20C Mylar

Electrodes • easy to replace window • entrance window: gauge 20C Mylar • electrodes: Cu frames + 0.0007" gold coated tungsten wires • wire pitch: 2 mm (transmission rate ~99%) • cathodes are combined and grounded • each anode is connected to a BNC feedthrough

Results • 241Am source • proton beams from MC-50 cyclotron • 5.443 (13%), 5.486 (85%) MeV • Energy resolution: 6.3% • proton beams from MC-50 cyclotron • will be commissioned in July • protons scattered from carbon

Electronics preamp: Canberra Model 2004 amp: Canberra Model 2020 ADC unipolar ADC preamp amp CFD bipolar strobe

Pictures

Results I - 10B beam, Ebeam = 60 MeV 50 kHz 200 kHz 300 kHz Beam particles stopping at the wire • new fast ion counter can reliably count up to 300,000 pps • transmission rate through a plane of electrode is ~98% for 1mm spacing • a set of electrodes with 2mm pitch was made

Results II – cocktail beams 76Ge, 76Se 80Ge, 80Se ~400,000 pps ~33,000 pps