Time Projection Chamber for the R 3 B set-up Combination of detectors upstream (target) & downstream of the magnet  Improvement of A, Z & E * balances  Spallation, fragmentation  Identification (γ) of the decaying systems  Study of the Coulomb fission of radioactive actinides TPC: a multi-purpose detector R 3 B: a versatile set-up for different physics superconducting magnet R 3 B - GLAD RPC Marie-Delphine SALSAC - DSM/IRFU/Service de Physique Nucléaire

GSI Large Acceptance Dipole  Active shielding (B(target) ~ 20 mT)  Field integral ~ 4,8 Tm  Central field ~ 2,5 T  Coil current density ~ 77 A/mm 2  Indirect He cooling at 4.2 K with thermo siphon  Quench protection with external discharges Marie-Delphine SALSAC - DSM/IRFU/Service de Physique Nucléaire

13/07/2015Jean-Eric Ducret, DSM/IRFU/Service de Physique Nucleaire3 The R 3 B-TPC TPC sampling scheme PC: Proportional counters (high gas amplification)  small-Z fragments IC: ionisation chambers (low gas amplification)  large-Z nuclei  MicroMegas cover of 2 x 5m² TPC electrostatics (vertical plane) 9 rows of pads (1 X 10 cm 2 ) ~ 6000 channels Marie-Delphine SALSAC - DSM/IRFU/Service de Physique Nucléaire

13/07/2015Jean-Eric Ducret, DSM/IRFU/Service de Physique Nucleaire4 TPC active volume ~ 3.2 m ~ 1.2 m ~ 0.9 m Marie-Delphine SALSAC - DSM/IRFU/Service de Physique Nucléaire ~ 2.5 m

Signal size & processing of the R 3 B – TPC  Signal dynamics & size  From Z = 1 to Z = 92, i.e dynamics  Rise time of the primary signals: ~ 5 to 30 ns depending on the drift length  Geometrical width of the signals:  up to a few mm  Rate/channel: kHz  No constraints concerning space and temperature  Pads: 10 x 100 mm  3 pads in each row per track  Charge deposited for p: 2500 e x GAIN, scaling with Z 2 Read-out for the R 3 B-TPC cm Gas – Tension..: not defined Pressure: 1 bar E Marie-Delphine SALSAC - DSM/IRFU/Service de Physique Nucléaire

Signal size & processing of the R 3 B – TPC  Signal processing  12-bit ADC for Z determination (in the two-gas amplification scheme) 10 significant bits, 1/2 10 resolution  Horizontal coordinate by charge division  Vertical coordinate by drift time measurement  Horizontal position resolution:  x ~ 200 µm, for Z = 1 & 2,  x ~ 100 µm, for larger Z  Threshold subtraction before data buffering & DACQ, to reduce the data flow  Drift time measurement  Beam start as t 0, pad time as stop Read-out for the R 3 B-TPC -2 Marie-Delphine SALSAC - DSM/IRFU/Service de Physique Nucléaire

Signal size & processing of the R 3 B – TPC  Detector simulation  Rather sensitive to the noise in the read-out channels (to keep low with respect to the proton signals)  Rather insensitive to cross talk in between read-out channels Read-out for the R 3 B-TPC - 3 Marie-Delphine SALSAC - DSM/IRFU/Service de Physique Nucléaire