TPC for 2p radioactivity studies Bertram Blank, CENBG

Energy (MeV) four 2p decay events GSI GANIL Discovery of two-proton radioactivity However: - only decay energy - no individual energies - no proton-proton angle TPC

- individual energies - proton-proton angle

Daughter boards Hybrid boards GEM: Gas electron multiplier beam 1500 electronics channels Hybrid boards Daughter boards

x z Cathodes: -768 micros-strips of copper (200  m) Anodes: -768 micros-strips of copper on a capton substrate (2x100  m) -Epoxi frame y x

Mother board + detector (15x15 cm 2 ) + 3 GEMs y x x z

TPC chamber Detector mount Electronics card Strip-strip matrix GEM  = 70  m d = 100  m

x energy | x time | y energy | y time Implantation at entrance Implantation at end saturation Different implantation depths by changing the B  Entrance of TPC Center of TPC End of TPC Threshold for implantation events Threshold for radioactivity events 48 Ca + 9 Be  26 P, 25 Si,…. x y beam Silicon detector

x energy | x time | y energy | y time Collimated  source  -delayed decay x y beam Silicon detector

Detector: double-sided microstrip detector (CERN) GEM: Gas electron multiplier (CERN) Detector gas: P10 at 1atm Active detection volume: 15 x 15 x 15 cm 3 ASICS: VAT/TAT by IDEAS, Norway TAC window: 10  s channels per chip: 32 time and energy Electronics and data acquisition: PXI – VME Dead time: 1.5 ms (max) 4 GEMs to increase the gain new a source collimation system non-linearity of the gain (-30% on sides) retract drift frames

20 mm 30 mm 28 mm beam -17% -33% Top view Possible reason: drift frames for field homogeneities GEM spectra

two-proton radioactivity: 45 Fe, 54 Zn, 59 Ge ?  2p radioactivity: 22 Al, 23 Si, 26 P, 27 S, 31 Ar,…..  correlations ???? ??? CENBG: Exotic nuclei group Electronics group Intrumentation group Mechanics group GANIL: DAQ group LISE group