n-DVCS/E03-106 status report Malek MAZOUZ The 18th of May 2004 Hall A collaboration meeting LPSC Grenoble n-DVCS/E03-106 status report -Tagger description Electronics Experimental tests Mechanics Simulations The 20th of May 2004
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
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
The 57 scintillators of the tagger 1ere couche etalee The 57 scintillators of the tagger M. Mazouz
The light guide is glued to the scintillator using a UV glue M. Mazouz
Scintillator and its guide are wrapped with aluminium and black tedlar M. Mazouz
All tagger scintillators and light guides are glued and wrapped (thanks to Kathy’s hard work!) M. Mazouz
Electronics : LPC Clermont-Ferrand supplied and tested 70 PMTs and determined their characteristics Hamamatsu R7788 PMT # of dynodes : 8 Gain at 650 Volts : 1. 105 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
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
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
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
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
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
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
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
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