1. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Liquid Xenon Detector Part I CEX beam test at piE1 Oct-Dec/03 –Hardware operation status –Analysis  A. Baldini’s presentation Other related topics –Detector Calibration –PMT R&D  A. Baldini’s presentation –Refrigerator –Liquid phase purification –Cryostat Liquid Xenon Detector Group

2. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Large Prototype 70 liter active volume (120 liter LXe in use), 228 PMTs Development of purification system for xenon Total system check in a realistic operating condition: –Monitoring/controlling systems Sensors, liquid N 2 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  beam –60MeV Electron beam –  from  0 decay

3. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting CEX beam test at piE1

4. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Elementary process  - (essentially) at rest captured on protons:  - p   0 n  - p  n   0    Photon spectru m 54.982.9 129 MeV M  /2  M  /2(1  cos  * ) M  /2 ** E  =55 MeV   * = 

5. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Angular selection  - p   0 n  0 (28MeV/c)    MeV  eV Requiring   FWHM = 1.3 MeV Requiring  > 175 o FWHM = 0.3 MeV   170 o 175 o 00     54.9MeV82.9MeV 1.3MeV for  >170 o 0.3MeV for  >175 o

6. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Overview of the beam test 25/Sep Detector was moved to the area. evacuation 27/Sep- Beam tuning 29/Sep pre-cooling 2/Oct-5/Oct Liquefaction 5/Oct-29/Oct Purification(gas phase) 5/Oct- Electronics setup 15/Oct  0 detected 24/Oct empty target run 1/Dec PMT amplifier study 6/Dec Recovery 7/Dec Cold xenon gas data for PMT calibration 22/Sep 29/Sep 6/Oct 13/Oct 20/Oct 27/Oct 3/Nov 10/Nov 17/Nov 24/Nov 1/Dec 8/Dec  0 detected Beam tuning purification pumping Cooling/liquefaction DAQ ~7weeks Recovery Cold xenon gas data

7. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Beam line –Magic momentum (110MeV/c) –FSH52, 4mm carbon degrader (110  107MeV/c) in ASY51 –26mm carbon degrader in front of the target –S1 counter (40x40x5mm3) to define the beam Area layout –The Electronics barrack placed in the area with concrete shielding around it. –All controls and monitors done in the barrack. –Liquid nitrogen supplied from a dewar located in the area.  E1 beam line Proton beam Target ASY51

8. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Setup Carbon degrader Lead Collimator at the beam line exit

9. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Hydrogen Target Thanks to Dr. J. Zmeskal. Liquid H2 cooled with a GM-refrigerator Temperature control Target cell –0.5mm t Al –40mm d x 100 L –125cc liquid hydrogen Kapton foil –  entrance –  exit    cell 

10. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting NaI detector For tagging  at the opposite side of LP 8x8 NaI crystals –40.6x6.3x6.3cm 3 Located 110cm from the target Signal processor and Trigger Box (QUAD module) to provide trigger signal ABCDEFGHABCDEFGH 8 7 6 5 4 3 2 1 For trigger Base Line Stabilizer Attenuator x10 ADC Trigger Box TDC Crystal Array HV Trigger module Differential input stage Differentiator, Attenuator and base line stabilizer Output stage

11. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting NaI Calibration High voltage value for each PMT is adjusted by using cosmic ray events. Pedestal subtraction & Gain correction are done in the offline analysis. Energy and Vertex reconstruction are performed by using corrected charge information  next slides. Cosmic ray events HV adjust & Gain Correction

12. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting NaI Energy Estimation Search for the NaI crystal with maximum charge Charge sum in the surrounding NaI’s. The Calibration parameter is determined by using 129MeV  data. (  37MeV/cosmic peak ) Raw Sum NaI with MaxQ Reconstructed Energy 55MeV 83MeV threshold 129MeV  - p   0 n  0    (E  = 55, 83MeV)  - p  n  (E  = 129MeV)

13. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting NaI Energy Resolution 55 MeV 7.0+/-0.13 % 83 MeV 6.5+/-0.14% 129 MeV 6.1+/-0.04%

14. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting NaI Vertex Reconstruction Search for the NaI with maximum charge Fit the charge distribution of the raw or column (8 NaIs in each) that include NaI with maximum charge using a gaussian function. 4cm diam. collimator. NaI with MaxQ  x 2.7cm  y 1.6cm

15. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting  - stopping distribution in the target must be considered in subtraction Timing Counter 2 layers of –5cm x 5cm x 1cm BC404 –Hamamatsu R5505 at both ends –3mm t Pb plate Time resolution can be estimated internally by TC1-TC2 5cm x 5cm x 1cm t BC404  R5505 Viewed from the target 100mm  Lead collimator TC LP NaI  S1 TC t LP - t TC  Pb !

16. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Timing Counter efficiency and resolution ~40% efficiency for 83MeV  (> 1MeV deposit in the scinti.) 60 psec time resolution in sigma 55MeV 83MeV 129MeV GEANT simulation Ratio of events with > 1MeV deposit in the scintillator (TC1-TC2)/2

17. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Xenon Large Prototype operating condition Gain/QE calibration –LED and  as usual PMT gain 10 6, 5x10 6 Absorption length after 2 weeks purification abs > 140cm (90% C.L.) (central value ~2.7m) Xenon extracted from the chamber is purified by passing through the getter. Purified xenon is returned to the chamber and liquefied again. Circulation speed 5-6cc/minute

18. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting QE Calibration The peak position is well reproduced by this MC code. Gas xenon data had been used for calibration because the absorption can be ignored in gas. –W-values are equivalent in gas and liquid? Established purification scheme provided very pure xenon. –Possible to evaluate PMT QE’s using the  event.

19. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Data Acquisition Hardware setup –ADC 3 ranges for front-face PMTs 2 ranges for the others –TDC for all PMTs –PMT amplifier (x10) BINP Lecce Software –Online MIDAS –Slow control (MSCB+LabView) Refrigerator control, Temp., Pressure Monitor Data set –Collimators in front of LP and NaI (  back to back) –Timing Counter (Pb+Scintillator) in front of NaI Low range (x8 amplification) Middle range High range (20dB attenuation)

20. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Trigger back-to-back  data –NaI : sum signal of the central 4 crystals –LP: sum signal of 8 PMTs on the front face & 4 PMTs on the back face  data with opening angle < 180 o –NaI : QUAD module Very low threshold trigger for LP –One or two hit(s) in any one of 8 clusters , LED, cosmic-ray, pedestal triggers for calibration 1 2 3 4 5 6 

21. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Beam Condition p(  - )=107MeV/c –Almost maximum separation (8nsec) of arrival time to the target between  and , and between  and e. Beam intensity –Up to 2.6 MHz @ 1800  A Electron contamination in the beam –Negligible in triggered events target  x=12mm  y=12mm  e/  ~8nsec TOF separation

22. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting  0 signal example LP ADC NaI ADC LP 83 MeV  NaI 55 MeV  LP 55 MeV  NaI 83 MeV 

23. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Background Condition Background events –most probably caused by beam-related neutrons, –Energy deposit up to 9-10MeV, –Corresponding to 1.5x10 6 p.e./sec Beam on/off –PMT output for  events changes, reduced to 70% of normal values at full intensity beam rate (less reduction at lower intensity) Not due to bleeder current shortage but due to photocathode saturation because we observed the same effect even with lower PMT gain.  events/ beam off  events/ beam on Thermal neutron in Xe Absorption length ~ 3 cm Capture close to calorimeter walls Multi γ, ΣE(γ) = 9.3 MeV PMTs used in LP do not have Al strip

24. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Pulse Tube Refrigerator 1. Heat load and PT cryocooler 2. Further test and schedule

25. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting - Heat Load - -Based on the KEK-original PT cryocooler, Cryocooler with higher cooling power has been developed for the final calorimeter

26. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Technology transfered to Iwatani Co., Ltd Designed: 150 W @165K Large Power Pulse Tube Cryocooler

27. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Large Power Pulse Tube Cryocooler One for Columbia University For Dark Matter Search Designed: 90 W@165K 3kWcompressor

28. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Large Power Pulse Tube Cryocooler Technology transfered to Iwatani Co., Ltd. Two for MEG Designed: 150 W @165K using 6.7kW compressor

29. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Large Power PT Cryocooler -Cooling power at 6.7kW compressor- KEK original for Large Proto For final calorimeter 6.7kW, 4Hz

30. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Results and Further Tests -Achieved cooling power of 190W at 165K (6.7kW compressor) -Orientation dependence test... Horizontal layout for the case of two cold head -Another phase shift configuration (Double Inlet) test... To increase cooling power Schedule -January 2004:Final parameter fixed -February 2004:Fabrication will start -March 2004:Will be delivered (two sets) -Can be installed for the LXe liquid purification test

31. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Liquid Phase Purification

32. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Liquid phase purification test Pump and purifier in the Large Prototype chamber –Very simple –No worry about heat load

33. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Implementation in the final detector Xenon from the bottom bypass the wall to the pump/purifier Easy maintenance Possible heat load to the bottom  Next slide

34. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Realization of the system Verification of liquid phase purification –Large Prototype is the best to show the purification performance Long term operation in the final detector –Heat load to the bottom must be minimized

35. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Purification system in the final detector Gas phase purification Liquid Phase purification

36. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Status Fluid pump was delivered to a Japanese manufacturer. Assembling the pump and purifier cartridge for verification. The system will be tested using the LP. motor Outside of the cryostat (room temp.) Inside of the cryostat (low temp.) Impeller Pump isolator

37. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Cryostat Construction

38. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Design goals: -Design goals: -Independent test of the inner vessel and outer vessel during construction. -Implementation of a draining system. -A simplification of the supporting system (three legs.) and a limiting displacement system -Adding a pre-cooling system on the inner vessel covers. -Adding a safety valve on the outer vessel for positive pressure. -Adding a rohacell sheet between the outer thin window and the magnet structure for positive pressure.

39. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting -Problem with high strength austenitic stainless steel. -To obtain high yield we need a stress hardening process that causes a slight ferromagnetic characteristic that can be removed by a special heat treatment. -Size of the sheet can be another problem. -The austenitic ss with the nitrogen should have a better strength and a better magnetic characteristic. Windows material

40. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Thickness of the Walls/Covers Suppose the pressure tolerance of 0.3MPa for the inner vessel and 0.1MPa for the outer vessel (vacuum insulation layer).

41. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Heat Load Calculation See also T. Haruyama’s talk on Jul 2002 review meeting. Main contribution is from PMT and cables. One pulse tube refrigerator can compensate the load. Possibility of mounting two refrigerator is now investigated

42. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Several modifications from the previous design

43. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting

44. Photon Detector 2002200320042005 Test Milestone AssemblyDesignManufactoring Large PrototypeBeam Test Vessel DesignAssembly & Test PMT Delivery + Testing RefrigeratorManufactoringAssembly Liq. Purification AssemblyTest Manufactoring Engineering runs

45. Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting Summary CEX beam test was carried out at  E1 area. –Analysis Results  A. Baldini’s presentation Liquid Phase Purification test will be done in 2004. Refrigerator will be assembled and delivered soon. Cryostat design renewal. Plan in 2004 –LP operation in  E5 to see background condition and COBRA magnetic field effect.