Shower detector status report P. Salabura XXIII collaboration meeting 14.1-18.11/GSI Darmstadt

Shower operation in Au+Au Detector HV: 2200 V (18 chambers) new electronics: higher electronic gain (~10) :  lowering of HV working point by 250 V w.r.t 2002-2008 Currents : (~7uA/plane) at 3*10^6/spill (spill is 1.5s) Gas flow: 10 l/hour/chamber 48%Ar : 50% Isobuthan (and 1-2% n-hepthane vapor) 1 event/beam time with chamber ignition (Pre1/Post1 sector 2 at the same time)

PreShower matching with tracks (DST-Gen0) Sz. Harabasz) Tracks & RPC hits Tracks & RPC hits & match_qual<4 All tracks Tracks & RPC hits & Pre-shower match_qual Tracks & RPC hits & match_qual<4? Tracks & RPC hits & Pre match_qual? Tracks & RPC hits & Pre &post1 match_qual? RPC - Pre X [mm] Max Hit Prob / pad ~ 1.3% Averaged 0.6%

Mean of Q vs particle velocity Example : Post1 All particles Negative pions Velocity () from RPC-tracking 10-15% differences between moduls –needs calibration for ePID

Mean of Q vs (x,y)-gain uniformity example: Pre chamber Mean (Q) for protons Negative pions Rows (y) – related to  columns (x) – related to  channel: Nr. column + i*Nr.Row 20% variations from edge to centrum : similar for all chambers ! (no need for calibration?)

Averaged efficiency vs  Pre Post1 Post2 example : Pre chamber Reference RPC-Post1 Pre chamber Pre chambers Negative pions All partciles Similar results for Post1

2d efficiency efficiency of Post1 RPC/Pre – Post2 as reference Negative pions p>150 MeV/c All particles

Shower - readout status Stable operation during whole beamtime Calibration mode and data taking mode OK. but ! timing problem in FPGA firmaware leads to corrupted ADC data (not present last year) ~4% channels concerned – (one row 25 on Post)

Shower – read-out problem Row 25 : Post2 OK charge (Y) vs column Row 25 : Post1 NOT OK Needs another iteration by experts …  (Marek/Greg/Marcin…)

Shower Summary 18 chambers working Peformance looks OK.- electrons? Timing Problem in ADC remains to be solved..