Malek MAZOUZ

n-DVCS/E03-106 status report

-Tagger description

-Electronics

-Experimental tests

-Mechanics

-Simulations

The 18th of May 2004

Hall A collaboration meetingLPSC Grenoble

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

( )

e p e p

e D e n p

Detection in Left HRS Detection in PbF2electromagnetic calorimeter

Detection inproton array(~20% of efficiency)

M. Mazouz

Tagger

Two scintillator layers:

-1st layer: 28 scintillators, 9 different shapes

-2nd layer: 29 scintillators, 10 different shapes

M. Mazouz

Proton array

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

M. Mazouz

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)

Amplification board

HV distribution board

PMT

LV (+/-5V) daisy chain connectors

HV-Signal-DC out Connectors

PMT + base

5 cm

M. Mazouz

PMT box

At present we are testing the set {PMT+base+light guide+scintillator}

Assembled paddle

M. Mazouz

Experimental Tests

Scintillator S1

Wire chamber H

Wire chamber M

Wire chamber B

Prototype

Scintillator S2

M. Mazouz

Light collection uniformity

Wire chambers Coordinates of each event

Paddle light collection map

for each cm² :

²²

1

²1 ²

cm

Totcm

n icm

i cmn i

i Tot

A

n

AA

n

: Number of events in this cm²

: Total number of events per paddle

²cmn

Totn

²cmA : Relative average Amplitude in this cm²

even

ts

Amplitude (mV)Amplitude histogram for a paddle (1st layer)

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