1 / 22

MEG Experiment at PSI R&D of Liquid Xenon Photon Detector

R&D work on a Liquid Xenon Detector for the m  e g Experiment at PSI on behalf of the MEG Collaboration University of Tokyo, Japan Presented by S. Mihara http://meg.psi.ch. MEG Experiment at PSI R&D of Liquid Xenon Photon Detector. m  e g Search as Frontier Physics. m e g in…

kmeier
Download Presentation

MEG Experiment at PSI R&D of Liquid Xenon Photon Detector

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. R&D work on a Liquid XenonDetector for the meg Experiment at PSIon behalf of the MEG Collaboration University of Tokyo, Japan Presented by S. Miharahttp://meg.psi.ch MEG Experiment at PSI R&D of Liquid Xenon Photon Detector

  2. me g Search asFrontier Physics • meg in… • SM+Neutrino Oscillation • Suppressed as ∝(mn/mW)4 • SUSY • Large top Yukawa coupling Current limit by MEGA • Neutrino Oscillation + SUSY • Hisano and Nomura 1998 10-10 tanb nm ne 10-11 e m W 10-12 g Br(meg) 10-13 Solar Neutrino 10-14 g 10-15 ~ ~ m e MnR(GeV) SK+SNO etc.=Large Mixing Solution ~ c m e

  3. MEG Experiment Overview • Detect e+and g, “back to back” and “in time” • 100% duty factor continuous beam of ~ 108m/sec • better than pulsed beam to reduce pile-up events • Two characteristic components • Liquid Xe photon detector • Solenoidal magnetic spectrometer with a graded magnetic field (COBRA)

  4. menn+”g” n n g e ? Signal and Background Signal qeg= 180° m g e • Signal • Main background sources • Radiative m+ decay • If neutrinos carry small amount of energy, the positron and gamma can mimic the signal. • Accidental overlap • A positron from usual Michel decay with energy of half of mm • Gamma from • Radiative muon decay or • Annihilation in flight of positron NOT back to back, NOT in time Ee = 52.8 MeV Eg = 52.8 MeV menng g n n e

  5. Requirement onthe Photon Detector • Good resolutions • Energy • Position • Time • Large acceptance with good uniformity • Fast decay time to reduce pile-up events

  6. Property Unit Saturated temperature T(K) 164.78 Saturated pressure P(MPa) 0.100 Latent heat (for liquid) r(J/kg)X103 95.8 Latent heat (for solid) r'(J/kg)X103 1.2 Specific heat Cp(J/kgK)X103 0.3484 Density r(kg/m3)X103 2.947 Thermal conductivity k(W/mK) 0.108 Viscosity m(Pa-s)X10-4 5.08 Surface tension s(N/m)X10-3 18.46 Expansion coefficient b(1/K)X10-3 2.43 Temperature/Pressure at triple point Tt(K)/PT(MPa) 161.36/ 0.0815 Properties of Xenon • Fast response, Good Energy, and Position resolutions • Wph = 24 eV (c.f. Wph(NaI) = 17eV) • tfast=4.2nsec tslow=22nsec • Narrow temperature range between liquid and solid phases • Stable temperature control with a pulse-tube refrigerator

  7. Liquid XenonPhoton Detector Shallow event 800 liter LXe viewed by ~ 800PMTs Deep event

  8. Absorption of Scintillation Light Simulation For Large Prototype labs=7cm • Scintillation light emission from an excited molecule • Xe+Xe*Xe2*2Xe + hn • Water contamination absorbs scintillation light more strongly than oxygen. Depth parameter labs=500cm Depth parameter Depth

  9. R&D Strategy • Small Prototype done • Proof-of-Principle Experiment • 2.3liter active volume • Large Prototype in progress • Establish operation technique • 70 liter active volume • Final Detector starting • ~800 liter

  10. Small Prototype • 32 2-inch PMTs surround the active volume of 2.34 liter • g-ray sources of Cr,Cs,Mn, and Y • asource for PMT calibration • Operating conditions • Cooling & liquefaction using liquid nitrogen • Pressure controlled • PMT operation of 1.0x106 gain • Proof-of-Principle Experiment • PMT works in liquid xenon? • Light yield estimation is correct? • Simple setup to simulate and easy to understand. S.Mihara et al. IEEE TNS 49:588-591, 2002

  11. Small PrototypeEnergy resolution • Results are compared with MC prediction. • Simulation of g int. and energy deposition : EGS4 • Simulation of the propagation of scint. Light EGS cut off energy : 1keV Rayleigh Scattering Length: 29cm Wph = 24eV

  12. Small PrototypePosition and Timing resolutions • PMTs are divided into two groups by the y-z plane • gint. positions are calculated in each group and then compared with each other. • Position resolution is estimated as sz1-z2/√2 • The time resolution is estimated by taking the difference between two groups. • Resolution improves as ~1/√Npe

  13. Large Prototype • 70 liter active volume (120 liter LXe in use) • Development of purification system for xenon • Total system check in a realistic operating condition: • Monitoring/controlling systems • Sensors, liquid N2 flow control, refrigerator operation, etc. • Components such as • Feedthrough,support structure for the PMTs, HV/signal connectors etc. • PMT long term operation at low temperature • Performance test using • 10, 20, 40MeV Compton g beam • 60MeV Electron beam

  14. Gas return To purifier Circulation pump Purification System • Enomoto Micro Pump MX-808ST-S • 25 liter/m • Teflon, SUS • Xenon extracted from the chamber ispurified by passing through the getter. • Purified xenon is returned to the chamber and liquefied again. • Circulation speed 5-6cc/minute

  15. Purification Performance • 3 sets of Cosmic-ray trigger counters • 241Am alpha sources on the PMT holder • Stable detector operation for more than 1200 hours Cosmic-ray events a events

  16. Absorption Length • Fit the data with a function : A exp(-x/ labs) • labs >100cm (95% C.L) from comparison with MC. • CR data indicate that labs > 100cm has been achieved after purification.

  17. Response to Gamma Beam • Electron storage ring, TERAS, in AIST, Tsukuba Japan • Electron Energy, Current: 762MeV, 200mA • 266nm laser to induce inverse-Compston scattering. • 40 MeV (20MeV, and 10MeV) Compton g provided. • The Compton edge is used to evaluate the resolution. • Data taking • Feb. 2002 (w/o purification) • Apr. 2003 (w/ purification) 10MeV 20MeV 40MeV

  18. Energy Spectrum • s2 :depth parameter: 40MeV Compton gamma data w/o xenon purification 40MeV Compton gamma data w/ xenon purification Depth parameter Depth parameter Total Number of Photoelectrons Total Number of Photoelectrons

  19. Energy Resolution Simulation 52.8MeV g • Shallow events have dependence on the depth of the 1st int. point. • Discard these shallow events (~34%) for quick analysis. • Calibration not completed • Very Preliminary: sE < 2% Depth parameter Very Preliminary

  20. Position Reconstruction • 2-step reconstruction • 1st step: Pre-determination of the peak • 2nd step: Precise determination with an iteration process • Data 40MeV Compton g (a) (b) (c) (d)

  21. Timing Resolution • Estimated using Electron Beam (60MeV) data • Resolution improves in proportion to 1/sqrt(Npe). • For 52.8 MeV g, s~60 psec + depth resolution. • QE improvement and wave-form analysis will help to achieve better resolution. (Visit “The DRS chip” by S.Ritt) s=75.6+/-2.0ps 45 MeV Energy deposit by 60 MeV electron injection s Timing Resolution (psec) 52.8MeV g (nsec) 104 4x104 Number of Photoelectron

  22. Summary • New experiment to search for meg at Paul Scherrer Institut • Two characteristic components (and many others) • Liquid Xenon Photon Detector • Solenoidal magnetic spectrometer with a graded magnetic field (COBRA) • R&D of liquid xenon photon detector using the large prototype • Long term stable operation using a pulse tube refrigerator • Purification of liquid xenon • Very preliminary result from the last g beam test • sE<2% for 40MeV Compton g

More Related