1. n-DVCS/E03-106 status report
Malek MAZOUZ
The 18th of May 2004
Hall A collaboration meeting
LPSC Grenoble
n-DVCS/E status report
-Tagger description
Electronics
Experimental tests
Mechanics
Simulations
The 20th of May 2004

2. Mostly sensitive to GPD E (unknown !)
Detection in Left HRS
Detection in PbF2
electromagnetic calorimeter
Detection in
proton array
(~20% of efficiency)
Mostly sensitive to GPD E (unknown !)
Information about quark orbital angular
momentum through models and Ji’s sum rule
Use of a deuterium target
Proton DVCS ( e d e γ p (n) ) is veto-ed by new detector
M. Mazouz

3. Two scintillator layers:
Tagger
Two scintillator layers:
1st layer: 28 scintillators, 9 different shapes
2nd layer: 29 scintillators, 10 different shapes
Proton array
There is an angular shift of 1.5° between the second layer and the first one
M. Mazouz

4. The 57 scintillators of the tagger
1ere couche etalee
The 57 scintillators of the tagger
M. Mazouz

5. The light guide is glued to the scintillator using a UV glue
M. Mazouz

6. Scintillator and its guide are wrapped with aluminium and black tedlar
M. Mazouz

7. All tagger scintillators and light guides are glued and wrapped
(thanks to Kathy’s hard work!)
M. Mazouz

8. Electronics :
LPC Clermont-Ferrand supplied and tested 70 PMTs and determined their characteristics
Hamamatsu R7788 PMT
# of dynodes : 8
Gain at 650 Volts :
Rise time : 1 ns
Decay time : 2 ns
LPSC Grenoble designed and tested the PMT bases.
To reduce the dynode current:
Reduction of the PMT Gain
Use of an amplificator (gain~10)
M. Mazouz

9. PMT + base 5 cm Amplification board HV distribution board PMT
LV (+/-5V) daisy chain connectors
HV-Signal-DC out Connectors
5 cm
PMT + base
M. Mazouz

10. At present we are testing the set {PMT+base+light guide+scintillator}
PMT box
Assembled paddle
At present we are testing the set {PMT+base+light guide+scintillator}
M. Mazouz

11. Experimental Tests Scintillator S1 Wire chamber H Wire chamber M
Prototype
Wire chamber B
To test our paddles we had used….Cosmic muons here repace . 2 scintillator to trigger off the acquisition. 3 wire chambers to determine the coordinates. The prototype is placed between the… and it contains. You can see 70cm lead. Every particle loses
Scintillator S2
M. Mazouz

12. Light collection uniformity
events
Amplitude (mV)
Amplitude histogram for a paddle (1st layer)
It is important to know if we have the low amplitudes in certains regions and the high ones in another regions or not.
This division lets un to compare 2 different. Of course this study could be done because using … Now we can represents this
Wire chambers
Coordinates of each event
Paddle light collection map
for each cm² :
: Number of events in this cm²
: Total number of events per paddle
: Relative average Amplitude in this cm²
M. Mazouz

13. Light collection uniformity
Light collection map for the five different shapes of the first layer.
The variation of the light amplitude is about 30% at most.
Paddles of the 2nd layer are being tested this week.
M. Mazouz

14. Mechanics: The main shielding : built by the workshop of LPSC Grenoble
The middle shielding (between the two scintillator layers) and the light tight cover will be finished next week.
M. Mazouz

15. Simulations:
The final geometry of the tagger has been introduced in the simulation program GEANT
Studies to be performed:
Background rates in the two scintillator layers
Neutron detection efficiency of the proton array
n-DVCS events distribution in the detector …
M. Mazouz

16. Planning : -Delivery time of cables and connectors : next week
-Detector Assembly at LPSC Grenoble : 3rd week of June
-Shipment to JLAB : End of June
-Detector assembly and tests at JLAB: July
-Hall A installation: August
-Beginning of DVCS experiment: 20th of September
-n-DVCS experiment: from October 31st till November 24th
M. Mazouz