B. Gläser, PAVI06

Rearrangement of the A4 Calorimeter for the Backward

Angle Measurement

B. Gläser, PAVI06

Outline

• Rearrangement of the Experimental Setup

• Electron Tagging Counter

• Summary and Outlook

B. Gläser, PAVI06

Rearrangement of the Experimental Setup

B. Gläser, PAVI06

Scattering Geometry under Forward and Backward Angles

Scattering ChamberCalorimeter

Target

Luminosity Monitors

Scattering ChamberElongation

B. Gläser, PAVI06

New SupportRotatable Calorimeter and Scattering Chamber Support

Plane Steel Plate

Hydraulic Oil Plunger

B. Gläser, PAVI06

New Rotatable Calorimeter

B. Gläser, PAVI06

Rearrangement Movie

B. Gläser, PAVI06

First Measurements at Backward Angles

225 MeV 255 MeV

315 MeV 570 MeV

B. Gläser, PAVI06

Background Simulation

e-

Simulated Photon Background @ 315 MeV from 0 Decay

B. Gläser, PAVI06

Electron Tagging Counter

B. Gläser, PAVI06

Counter Geometry and Efficiency

Efficiency Demands on the Counter:

Detection Efficiency Electrons -> 100%Detection Efficiency Photons -> 0%

Elastic Rate @ 20µA (One Crystal): ~ 1,1 kHz

e-

… …

Electron Beam

PbF2-Crystal

Additional Counter

Scattering Chamber

e+,e-

Cherenkov Counter vs. Scintillator

Detection Efficiency Electrons:Detection Efficiency Photons:Radiation Length Counterand Scattering Chamber:

< 100%~ 0%

~ (10,1 to 14)% X0

~ 100%> 0%

~ 15% X0

Scintillator Pulse Height SpectraCherenkov Pulse Height Spectra

Pulse Charge / a.u.

Co

un

ts

Pulse Height / a.u.

Cou

nts

B. Gläser, PAVI06

Counter Types

• Diffusely Reflective Aerogel Cherenkov Counter

• Gas Cherenkov Counter

• Scintillation Counter

Diffusely Reflective Aerogel Cherenkov Counter

Aerogel

Window forPhotomultiplier

Housing Calorimeter Crystals

Housing

Aerogel

Target

Scattering Chamber

Centerline Scattering Chamber

B. Gläser, PAVI06

Gas Cherenkov Counter

Filling:

Refractive Index:

Expected Photelectrons:

Gas Cherenkov Aerogel Cherenkov

Isobutane

1,0019

~4

Aerogel (High Transparent)

1,05

~5

B. Gläser, PAVI06

Scintillation Detector

Plastic Scintillator (EJ-204) Photomultiplier Housing(XP2262B)

Scintillator Dimension : 20 mm x 50 mm x 400mm

Cou

nts

ADC-Channel ADC-Channel ADC-Channel

Aerogel Gas Scintillator

Energy Spectra @ 315 MeV with the Tested Counters

Elastic Efficiency: ~68% ~46% ~81%Covered PbF2-Crystals: 28 28 14Expected Elastic Rate: ~30kHz ~30kHz ~15kHzMeasured Total Rate: ~2Mhz ~800kHz ~3Mhz

B. Gläser, PAVI06

The New Scintillation Counter

Scintillator Photomultiplier Base

Scintillator: Plastic Scintillator EJ-204from Eljen Technology

Photomultiplier: A Standard Fast,12-Stage, 51mm Tube XP2262B

Base: Full Active Base, our Design

Final Design

Double Ring with 72 ScintillatorModules.Each Module Covers 14 PbF2 -Detectors

B. Gläser, PAVI06

Final Calorimeter Design

Adr

ess

bit

Sci

nti

llato

r

PM

Electronic Setup

CFDprogr.Delay 20 ns

data

triggerMemory

MEDUSA

signalprocessing

PMPbF2

HistogrammUnit

pol0 pol1unused

Pola-Bit

pol0* pol1*

Delay / ns

Cou

nts

Typical Rate Scintillator: ~ 1MHzAccidential Coincidence: 1% - 4%

B. Gläser, PAVI06

Actual Energy Spectra @ 315 MeVC

ount

sC

ount

s

ADC-Channel

ADC-Channel

Cou

nts

/ 10

3

Elastic Efficiency : ~90%

PRELIMINARY

B. Gläser, PAVI06

Summary and Outlook

• Rearrangement of the Calorimeter Setup

• Electron Tagging Counters Tested

• New Scintillation Counter

• Measurements at Backward Angles

• Measurements with Deuterium