Upload
badu
View
91
Download
0
Embed Size (px)
DESCRIPTION
日本物理学会 近畿大学 2000.4.1. SPring-8 レーザー電子光 ビームラインでの タギング検出器の性能評価. 核物理研究センター 三部 勉 LEPS collaboration. 1.レーザー電子光 2.タギング検出器 3.実験セットアップ 4.エネルギー分解能 5.検出効率とバックグラウンドレート 6.まとめ. Laser Electron Photon. Electron 8GeV. Laser 3.5eV. Backward Compton scattering. Scattered photon - PowerPoint PPT Presentation
Citation preview
SPring-8 レーザー電子光ビームラインでの
タギング検出器の性能評価
核物理研究センター三部 勉
LEPS collaboration
日本物理学会 近畿大学 2000.4.1
1.レーザー電子光2.タギング検出器3.実験セットアップ4.エネルギー分解能5.検出効率とバックグラウンドレート6.まとめ
Laser 3.5eV
Scattered photon(Laser Electron Photon) Energy Max 2.4GeV
Intensity 1×107 /sec Linear/Circular polarization
Backward Compton scattering
Electron 8GeV
Laser Electron Photon
Position of Scattered electron ( SSDch )
Pho
ton
Ene
rgy
(G
eV)
Photon energy
E = Ee - Ee’
Initial electron energy
Scattered electronenergy
Analyzed by Bending Magnet
Photon Tagging
Measured by PWO calorimeter
Tagging counter (top view)
Silicon Strip Detector ×2(Analog readout,100m pitch 640 ch)
1cm8GeV electron beam
Scattered electron
Plastic scintillator ×20(3mm(T),7.4mm(W),10 mm(H))
Energy Counter Timing Counter
Accelerator chamber wall
LEPS spectrometer
• Analyzing magnet (0.7T)• Vertex Detector (SSD)• Charged particle tracking
– MWDC (3 chambers)
• Particle Identification– TOF wall (40 slats)
Experimental Setup (Top view)
TOF
Dipole Magnet (0.7 T)
MWDC
Bremsstrahlung Photon
Target( Al 2 mm width, 1 mm
thick )+
Scintillation fiber( 1mm 2)
E
Tagging Counter
Spectrometer ( e+e- )
e-
e+
Energy ResolutionTagging efficiencyBackground rate
Plastic Scintillator
e+e- Momentum Reconstruction
E(T
aggi
ng)
GeV•e+e- production point
→ localized in wire target x , z ~ 0.3mm
•One to one correspondence pe xe
Monte CarloSimulation
pe ~ 8 MeV/mm @1GeV
E ( e+e- ) GeVPe : e+/e- momentumxe : e+/e- x-position after magnet
Energy Resolution
2 = Meas2 ー e+e-
2
Energy resolution of Tagging
Resolution of momentum reconstruction
Width of Experimental Data Monte Carlo
50‐50( MeV
)0
E(Tagging) - E(e+e-)
Cou
nts
1.60<E<1.88 GeV Meas=23MeV
Ave.15.3 MeV
(
MeV
)
E (GeV)Systematic error
Electron Track in Tagging counter
ScatteredElectron
SSD
PlasticScintillator
PlasticScintillator
Event Selection / Analysis 1. Pick up two clusters in up and down stream SSD.
2. Angle of track |e - e| < 4 3. Number of corresponding hit in the scintillator array (n)
e
→ Hit pattern ‘quality’ = 0 SSD+ Scintillator(n = 0) =1 SSD+ Scintillator(n = 1) =2 SSD+ Scintillator(n = 2)
Tagging Efficiency and Background rate
Background rateHit pattern(quality)
SSD+ Scintillator(n = 2)
SSD+ Scintillator(n 1)≧
SSD+ Scintillator(n 0)≧
86.5± 0.6%
Efficiency
90.6± 0.5%
91.0± 0.5%
2.3 ± 0.1%
2.6 ± 0.1%
2.8 ± 0.1%
Efficiency = Number of tagger hit(≧1 track) ÷ Number of e+e- pair in Tagging acceptance
Background rate = Number of tagger hit(≧2 tracks) ÷ Number of tagger hit(≧1 track)
Definitions
Condition : Bremsstrahlung photon @ maximum electron current
Summary
Performance of Tagging system
1. Experimental method•e+e- momentum reconstruction using wire target.
2. Energy resolution• Photon Tagging Resolution 15 MeV
3. Efficiency and background rate (Bremsstrahlung photon)•Efficiency 90% [SSD+ Scintillator (n 1)≧ ]
•Background rate 3 %.
4. Further study is on going with Laser Electron Photon ...
Photon Energy Spectrum
1st beam observation (1999.July)
Photon energy (GeV)1 2 3
Cou
nts
Tagging counter
PMT
SSD
Beam
PlasticScintillator