1. Shower detector status report
P. Salabura
XXIII collaboration meeting
/GSI Darmstadt

2. Shower operation in Au+Au
Detector HV: V (18 chambers)
new electronics: higher electronic gain (~10) :  lowering of HV working point by 250 V w.r.t
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)

3. 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 %

4. 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

5. 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?)

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

7. 2d efficiency efficiency of Post1 RPC/Pre – Post2 as reference
Negative pions p>150 MeV/c
All particles

8. 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)

9. 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…)

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