Upload
kolya
View
52
Download
0
Tags:
Embed Size (px)
DESCRIPTION
Liquid Xenon Detector for the MEG Experiment. Toshiyuki Iwamoto 4/Oct/2006 10 th Topical Seminar on Innovative Particle and Radiation Detectors (IPRD06) Siena. MEG Physics. Lepton flavor violating process already violated in neutrino sector Forbidden in the Standard Model - PowerPoint PPT Presentation
Citation preview
4/Oct/2006 Siena 2006 1
Liquid Xenon Detector for the MEG Experiment
Toshiyuki Iwamoto4/Oct/2006
10th Topical Seminar on Innovative Particle and Radiation Detectors
(IPRD06) Siena
4/Oct/2006 Siena 2006 2
MEG Physics• Lepton flavor violating process
– already violated in neutrino sector
• Forbidden in the Standard Model
• Sensitive to the new physics models, SUSY GUT, or SUSY seesaw etc.
• The present experimental limit – ~ 1.2x10-11 by MEGA experiment
Clear 2-body kinematicsEe = E = 52.8 MeVBack to back (e= 180°)Simultaneous (Te = T)
4/Oct/2006 Siena 2006 3
SensitivityBackground Radiative decay : e+ e < 10-14
Accidental overlap: decay e random To reject these background, energy, timing and vertex resolution pile-up rejection from waveform analysis
Single event sensitivity ~ 4x10-14
Background event ~ 4x10-14
90% C.L. sensitivity ~ 1x10-13
photon detector requirement E= 5% (FWHM) T= 150ps (FWHM) X= 9mm (FWHM)
MEGA
MEG
4/Oct/2006 Siena 2006 4
MEG detector
Approved in 1999 at PSIPhysics run in 2007
4/Oct/2006 Siena 2006 5
MEG Detector590 MeV proton Ring Cyclotron
COBRA magnet w/ graded B field
Photon detector
Drift chamber
Timing counter
H. Nishiguchi, 5th Oct“The MEG positron spectrometer”
Most intense DC muon beam (108/s)
4/Oct/2006 Siena 2006 6
Photon Detector800 liter liquid xenon, 846 2” PMTs in liquidHigh light yield, fast response and good uniformity (~40000ph/MeV, 4.2, 22, 45ns)
Low temperature (~160K), = 178nm : development of PMT, refrigeratorXenon purity : remove H2O
Performance test of Xe detector 2.3 liter prototype confirmed the principle of Xe 68.6 liter prototype 10, 20, and 40 MeV inverse Compton scattering energy, timing and vertex resolution 55, 83MeV, 129MeV from -p->n0,n reaction energy, and timing resolution
4/Oct/2006 Siena 2006 7
Improvement PMTQ.E. : ~15%Photocathode : K-Cs-SbMetal channel dynode, 12 stagesSilica window (for UV light)
Compact, and low heat loadTolerance up to 100G magnetic fieldAl strip to keep surface resistance at low temp.Zener diode for high rate background
PurificationGas & Liquid phase purification testedMetal getter (zirconium) by gas ~0.5l/hMolecular sieves by liquid ~100l/h
2.5m
1m
57mm
4/Oct/2006 Siena 2006 8
Prototype test, 10~40MeV
Vertex distribution
4mm1.6% in
40MeV Energy
68.6l liquid xenon prototype detector
228 PMTs
4/Oct/2006 Siena 2006 9
Prototype test, 55~129MeV
- (at rest) + p -> 0 + n, 0(28MeV/c) -> + (54.9MeV<E<82.9MeV) Almost monochromatic is available- + p -> n + (129MeV) Energy, timing resolution neutron response
Opening angle ()
Ener
gy (M
eV)
PrototypeLXe
LYSO
NaI
H2 target
170°
175°
ENaI + ELYSO (MeV)
phe
Xeno
n de
tect
or
55MeV
83MeV
4/Oct/2006 Siena 2006 10
Photon detector performance
110 - 64 (LYSO) - 61 (Beam) = 65psec
110 psec
= 1.23 ±0.09 %FWHM=4.8 %
Expected Performance Energy : 5% (FWHM) Timing : 150 psec (FWHM) Vertex : 9mm (FWHM)
5%
1%En
ergy
Res
olut
ion
() [
%]
Energy resolution vs. EnergyEnergy distribution @ 55MeV
Timing distribution
4/Oct/2006 Siena 2006 11
Detector operation
LXe Calorimeter Liquid circulating purifier
Liquid pump (100L/h)
Purifier1000L storage dewar
Cryocooler (100W)
LN2
LN2
Getter+Oxysorb
GXe pump (10-50L/min)
GXe storage tank
Cryocooler (150W)
Heat exchanger
Refrigerator
250l gas xenontank x 8
1000l liquid xenonstorage tank
purifier
4/Oct/2006 Siena 2006 12
Calibration method• Gain monitor : LED• Q.E. : 241Am source• Energy
– 55, 83, and 129 MeV from -p0n, 02
– Ni thermal n capture 9MeV– Proton accelerator
• Li(p,)Be 17.6MeV• B(p,)C 16.1MeV
• Timing– Laser– radiative decay– 55 MeV from -p0n reaction (Pb+Scintillat
or)• Vertex
– 55 MeV from -p0n reaction (collimator)
3x3 NaI array
LH2 target
4/Oct/2006 Siena 2006 13
Detector Construction
4/Oct/2006 Siena 2006 14
Detector Construction
The performance of all PMTs checked in the liquid xenon before installation
outer
side
top
inner
4/Oct/2006 Siena 2006 15
Schedule• Cryostat will come to PSI in the end of this
year• PMT installation into holders almost done• Liquid xenon detector assembly will be done
in the beginning of next year, and then liquefaction, purification and stable operation test will be continued.
• physics run starts in 2007• Positron spectrometer run and calibration
run will be done in this year
4/Oct/2006 Siena 2006 16
Summary• MEG experiment will search for ->e with better
sensitivity than previous experiment • The performance of liquid xenon detector has be
en tested by using prototype, and the real detector is being constructed
• Physics run of MEG experiment will start in 2007.• Positron spectrometer data and calibration data
will be taken in this year.