Electron detectors for happex2 and he
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Electron detectors for HAPPEX2 and He. 4. Design Tests with high E electrons PMT tests Installation in HRS. Focal plane Detector. t = 65 Mhz Dose = 2 MRad. 100 x 600 mm. Geometry. Detector stack overlaps elastic line. Two segments geometry for HAPPEX2. Mechanics.

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Electron detectors for HAPPEX2 and He

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Electron detectors for happex2 and he

Electron detectors for HAPPEX2 and He

4

  • Design

  • Tests with high E electrons

  • PMT tests

  • Installation in HRS


Focal plane detector

Focal plane Detector

t = 65 Mhz

Dose = 2 MRad


Geometry

100 x 600 mm

Geometry

Detector stack overlaps elastic line

Two segments geometry for

HAPPEX2


Mechanics

Mechanics

5 inches PMT

Brass-quartz stack

Light guide

Filter box


Fused quartz

Fused quartz

  • Radiation hard (Babar, CMS, E158)

  • Optical polished

  • (15-20 Angstr)

  • 92% transmission in the range

  • [350,550] tested with optical

  • bench and with cosmic rays


Magnetic materials

Magnetic materials

Bext

False asymmetry

Fe

Fe

N+

N-

FA= M(Fe) x P(Fe) x <A>

Polarized electrons

M(Fe) -> specified ~ 1%

P(Fe) -> a) Bext at focal plane

b) mr

<A> Mean Moeller asymmetry -> numerical calculations.


Magnetic materials1

Magnetic materials

  • -Bext <= 0.4 Gauss, mr <=2

  • PFe < 10-5

    -<AMoller> << 1 ppm

  • -Negligible contribution in

  • the detector asymmetry.


Test with high energy electrons

Test with high energy electrons

Moeller dipole

Beam pipe

h2

h1

Motorized rail

Trigger scintillators

Hodoscope

Selection of 2 e- of same energy


Resolution

Resolution

  • Nge/e- = 250

DE/E = 18 %


Edge effects

100 x600 mm

Edge Effects

DE/E=20%

  • Larger resolution balanced

  • by extra statistics.

  • Need to correct for

  • correlations between two

  • segments for final result.

Real data to

be analyzed

DE/E=90%


Pmt tests

PMT tests

  • PMT burle 8854

  • Need wide range in gain

  • (10E3-106) :

  • 2 bases available:

  • - Happex

  • - Resistive, low gain


Pmt test

PMT test

Gain/IAnode correlations

Running conditions:

Preliminary results:

40 MHz, Filter 1/10

25 ge/e

 I=1mA with G=104

-Happex Base DG/G =5% @ 1170V

-Resistive base: DG/G= 2%@ 1420V


Installation in hrs

Horizontal rails

Installation in HRS


Installation in hrs1

Installation in HRS


Installation in hrs2

Installation in HRS

10 cm vertical gap between

VDC and detector for scanners


Detector change

Detector Change

  • Remove 1 segment in each spectro. ~4h

  • Start installation of previously prepared “L” detector.

  • Assembly of the 2 removed segments for the 2nd “L” ~8h

  • Installation of the 2nd “L”~6h

  • Could be done within 1 day

    Man power : 5


Electron detectors for happex2 and he

WEB

Eveything at:

www-dapnia.cea.fr/Phys/Sphn/Parity/


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