1. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Liquid Xenon Detector and Related Topics Liquid Xenon Optical Properties (TN-020) PMT Test Facility TERAS Beam Test Preliminary Results Beam Test in Oct-Dec 03 at PSI Cryostat Schedule S.Mihara For Liquid Xenon Detector Group

2. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting LXe optical properties (MEG-TN020) The λ att, λ abs and n are not very well known properties for LXe in the VUV Contraddictory measurements  contaminations? Controlled measurements of epsilon, n exist in gas phase: CAN WE EXTRAPOLATE FROM THE GASEOUS TO THE LIQUID PHASE? 1.Yes we can extrapolate  give a prediction for n 2.Measurement of λ R (LP)  measurement of n

3. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Dielectric properties vs density In gaseous phase: Clausius-Mossotti (Lorentz-Lorenz) LINEAR IN !! At increasing density: non linear effects (virial expansion) 2 molecules 3 molecules …. Molar liquid density = 0.0229 cm -3  reasonable Xe is a non polar atom

4. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Check linearity at different wavelengths On the absorption lines the F LL function is only marginally valid but it can be considered an acceptable approximation still at the LXe emission line...

5. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting …near the absorption line? The Xe has the first absorption band at λ=146.9 nm (hν=8.4 eV) Wannier excitons It can test the linearity on ρ of the F LL function on a large range of density 4.49 10 -5 2.24 10 -2 Liquid Exciton Xe absorption Re εIm ε

6. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting A(ω) in VUV gas-liquid...as it can be seen directly from the results obtained. = experimental data dilute gas = extrapolated value (fit) A(ω)  n

7. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting n extrapolation We can extrapolate a value of n=1.69 ± 0.02 at 175 nm How this compares to published measurements? –Subtil et al. (1987) 1.71 –Chepel et al. (2002) 1.69 –Barkov et al. (1996)1.56 (180 nm) Pretty good agreement

8. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting A relation between n and λ R In gaseous phase: In liquid phase: fluctuations (Einstein equation) Hence: A measurement of λ R gives a hint on n λ R = (29 ± 2) cm *  n = (1.71 ± 0.015) ! * Ishida et al, NIM A384 (1997) 380 8 th power

9. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting PMT Test Facility

10. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting MEG – PMT cryogenic test facility: PURPOSES -SYSTEMATIC TEST OF THE PMT’s FOR MEG IN OPERATING CONDITIONS: immersed in liquid Xe -BUILD AN EVOLUTIVE CRYOSTAT: PHASE 1MANUAL OPERATION WITH LXe EMPTING/FILLING FOR EACH PMT PHASE 2MANUAL OPERATION WITHOUT LXe EMPTING PHASE 3TEST OF CARTRIDGE OF PMT’s WITHOUT LXe EMPTING -SETUP A CRYOGENIC LABORATORY AT INFN-PISA -GET EXPERIENCE IN HANDLING LXe -OTHER MEASUREMENTS ON LXe -TESTS ON OTHER PMT’s AND OTHER DEVICES (APD’s, …) FOR THE MOMENT … PHASE 1 

11. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting MEG – PMTct – Cryogenic/Vacuum Diagram Phase II

12. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting MEG – PMTct - Cryostat

13. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Cryostat delivered from CINEL: phase I… Almost all material delivered: –Cryostat –Pumping system –Leak detector –Feed-throughs Signal Xenon –Gases –Oxisorb –Material for phase 2/3 Waiting for… –Xe transportation tank (needed CE certification) –Clean pipes –Slow control –PMTs!

14. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting …and phase II: linear motion and gate valves In phase II/III Xe should be kept liquid: Gate valve The PMT can be extracted from the top of the cryostat: Cross Linear movement attuator

15. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Calibration source  and  (+LED)  -source that is stable in liquid Xenon: –3 kBq 241 Am deposited on a micro-etched surface –Ordered to Campoverde srl. Quotation from a Czech factory which provides gold-plated sources. Source and PMT holder under construction Reference PMT: – Hamamatsu R7400-9 25 mm

16. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting  -source TRIGGER PMT HAMAMATSU R7400U- 09 ,  SOURCE HOLDER Difference in α and β waveform in Xe

17. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting In parallel: PMT test at warm temperature Blue LED pulser (same as LP) to study the PMTs in controlled conditions Gain vs T Gain vs time… Waiting for VME LED pulser (this week) LED fiber filter PMT

18. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting PMT Test Facility Status The PMT test facilty is close to be operational Almost all material delivered also for phase II/III Sources in preparation In parallel: test at warm temperature.

19. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting TERAS BEAM TEST Overview of the test Energy measurement Position reconstruction Timing measurement

20. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting TERAS beam in April 03 Xenon liquefaction completed 10 days before the beam time. Purification of xenon in gas phase. Data acquisition –40MeV(main), 20MeV, 10MeV –Different incident positions –Different incident Angles –Materials in front of the detector –PMT high gain runs

21. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Gas Phase Purification System 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 Enomoto Micro Pump MX-808ST-S –25 liter/m –Teflon, SUS Gas return To purifier Circulation pump

22. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting TERAS  Beam Line Electron beam –Energy: 764MeV –Energy spread: 0.48%(sigma) –Divergence: <0.1mrad(sigma) –Beam size: 1.6mm(sigma) Laser photon –Energy: 1.17e-6x4 eV (for 40MeV) –Energy spread: 2x10-5 (FWHM) –Divergence: unknown –Beam size: unknown Compton Spectrum (E  -Ec/2) 2 +(Ec/2) 2 Collimator size

23. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting D: depth parameter MC simulation Data Previous Test This Test Short abs Long abs  D= D D D D D D: 20~100  0~25cm

24. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Effect of Material 5mmt, 10mmt, 15mmt Al 15mmt Al+4mmt Stainless Steel 5mmt Pb 2nd collimator Al, Stainless, Pb plates LP 5mm Al 0.053X 0 10mm Al 0.11X 0 15mm Al 0.16X 0 15mm Al + 4mm Stainless Stell 0.398X 0 5mmt Pb 0.89X 0 COBRA thickness: 0.197 X 0

25. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Position/Incident Angle Scan Incident Position –10 different positions for 40MeV  (blue and red) –2 different positions for 10MeV and 20MeV  (red) Incident Angle (40MeV) –0, 7.5, and 15 degree on the center –Not analyzed yet… LP  62mm

26. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Detector Operation Status No serious trouble during the test –Except one of two TDC modules was broken in the final run (PMT high gain run) Total amount of xenon used: ~120 liter Stable operation by the pulse-tube refrigerator/Liquid Nitrogen cooling pipe (only while circulation) PMT calibration as usual (LED/alpha/cold gas alpha)

27. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Energy Measurement

28. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Energy Spectrum Fitting Principle… EE N pe Response function Compton Spectrum Convolution of Compton Spectrum Response Function For understanding simply… Suppose Response function is an asymmetric Gaussian  left  right

29. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Energy Spectrum Fitting cont’d Require D(depth parameter)>45 –~34% of events in the range of 40MeV+/-4MeV are discarded by this requirement Suppose Compton Spectrum around the edge (E-Ec/2) 2 +Ec 2 /4 Detector Response Function –Gaussian with Exponential tail f(x) = Nexp{t/  2 (t/2-(x-x 0 )}, x<x 0 +t Nexp{-1/2((x-x 0 )/  ) 2 }, x>x 0 +t Convolution –Integration +/- 5  Fitting is done in two steps Determine the edge position Fix the edge in the 2 nd fitting for determining the other prams Detection efficiency (estimated by MC) : 74% within +/- 4% energy cut at 52.8 MeV (cf. Progress Report Jul 02) (16% of events are lost due to interaction with material in front of the active volume) 26 %

30. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Dependence on E  Very preliminary –Typical 10, 20, 40MeV data fit using the convolution function –Error estimation is not finalized. Conservatively 30% error for the energy resolution is supposed. –Resolution is shown in sigma.

31. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Energy Resolution vs. Depth Parameter Number of Photoelectrons D For  incident at the detector center D > 35, 45, 55….85 Resolution: < 2% in sigma except shallow events (D<45).

32. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Material Effect on the Resolution No apparent deterioration of the resolution Loss of efficiency COBRA Thickness Trigger Threshold Al 5mm Pb 5mm

33. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Position Dependence 1.85% in  1.83% in  1.80% in 

34. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Measurement with half the front PMT switched off To simulate the convex front geometry of the cryostat MC simulation (reported in the last review meeting) TERAS data –Switch off half of the PMTs in the front face Use 4x4 PMTs out of 6x6 PMTs –Switch off PMTs on the side walls 

35. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting VLP and Curved Detector Shape studies: Compare LiXe and a VLP (100 x 50 x 50 cm 3 ) to check the effects of a different geometry on position and energy resolution. no difference with the curved detector for position resolution (10.6 mm FWHM in both cases for a realistic situation); a 3% systematic correction is needed on both coordinates for VLP slight improvement in energy resolution (from 4% to 3.5%); however, more critical problems of energy containment a much larger volume (1.5 m 3 ) of Xenon would be needed (and PMTs!).

36. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting TERAS Data Only 4x4 PMTs on the front face Switching off half the front PMTs –Compton Edge shifts by 6.2% –Resolutions are almost same (1.84 to 1.85% in  ) before and after switching off. Switching off PMTs on the side wall(s) –1 plane off  2.05% in  –2 planes off  2.22% in  –3, 4 planes off  > 3% in  4 planes off 3 planes off 2 planes off 1 plane off 1/N pe 1/sqrt(N pe ) Number of Photoelectrons

37. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Switching off PMTs on side walls 1 plane off 3 planes off Deterioration of the energy resolution when switching off PMTs is not mainly caused by loss of N pe. PMTs on the side walls compensate 1 st conversion point dependence. Number of Photoelectrons D D

38. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Effect of a “faulty” PMT All PMTs on:  =1.8% Switching off one PMT on the front wall. –the nearest PMT   =2.3% –2 nd nearest PMT   =1.9% –3 rd nearest PMT   =1.9% 300 PMTs on the front face in the final detector –~4/300 = 1.3% loss of acceptance F30 off  =2.3% F22 off  =1.9% F28 off  =1.9%

39. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Position Reconstruction Simple weighted average –Using all PMTs on the front –Very fast, but not so good resolution and “bias” exits Localized weight method –Using only selected PMTs around the energy release points to reduce the shower fluctuation effect

40. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Simple Average Method Data and MC are in good agreement. Reconstruction “bias” exists. Depth

41. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Localized Weight Method Projection to x and y directions. Peak point and distribution spread Position reconstruction using the selected PMT

42. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Samples of Reconstruction 1mm

43. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Reconstruction “Bias”

44. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Position Reconstruction Resolution

45. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Timing Measurement 128 TDC channels for the PMTs around the front face. Leading-edge discriminator with threshold level at –12mV. Start timing of the TDCs is determined by the xenon detector itself. –Laser start timing  1  s jitter. –Electron tagging counter was placed in a TERAS Q-magnet. Difficult to achieve good resolution as a reference. Same method as in KSR electron beam test is employed for timing measurement. Detector is divided to left and right groups and arrival time difference was compared to evaluate the resolution.

46. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Timing Measurement Very Preliminary Result We observed that 1.Timing resolution improves as the PMT gain increases. 2.Timing resolution improves as N pe increases. –The best value (48.8 psec in sigma) was obtained for >160MeV synchrotron radiation light taken in a dedicated run Effect of shower fluctuation along the  incident direction is canceled, while the effect perpendicular to it is not.  Left Right

47. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Open Questions Compton Spectrum Shape –Broader than simulated shape –Detector effect ? Reflection or absorption on the PMT window? Rate Dependence

48. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Compton Spectrum Shape 1. Broad peak of the total photoelectrons. 2. Many low energy events. Maybe beam spectrum We have not a clear answer threshold

49. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Comparison with revised MC Compton  spectrum shape Electron beam spread at the collision point Collimator position Data MC

50. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Reflection or Absorption on the PMT window? (Qsum-Qfront)/Qsum Qsum D

51. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Discrepancy at Low Energy Side total photoelectrons 0<z<3 z<0 z: first conversion depth [cm], 0 means surface of LXe. Data MC

52. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Absorption in the Mn layer? window Mn layer Photocathode light 300um Al strip Reflection cannot explain simultaneously both gamma and alpha data. The previous model (in LP) uses a Mn layer to keep the surface conductivity of the PD at low temperature. The new model uses Al strip instead of the Mn layer. Compare responses for different incident angles of light. Previous New

53. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Rate Dependence Rate dependence –In case of high current in TERAS, SR light background is huge to decrease the effective gain of the PMTs. –Data with a 60 Co source in front of the entrance wall at different distance to simulate  background. Detailed analysis to interpret the measured dependence for the actual detector operating condition is not finished yet… LED 

54. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Oct-Dec 03 Beam Test at  E1

55. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting The elementary process  - (essentially) at rest captured on protons:  - p   0 n  - p  n   0    Photon spectrum 54.982.9 129MeV

56. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting CM and Lab frame M  /2  M  /2(1  cos  * ) ** E  =55 MeV   * = 

57. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Angular selection  ’s back to back in lab: 55 and 84 MeV  E  / E  < 1%    < 5 o This fixes the angular acceptance to 6  10 -4 /56 * = 1.07  10 -5 5 o = 87mrad = 8.7cm @1m * (83-55)/0.5   - 

58. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Experimental configuration NaI LXe Coincidence: C & !A & NaI (Offline: & LXe)  - - beam ACT Mod TARGET? Rate Background Thin/small (angle/X 0 ) Handling Previous use GH 2 (Panofsky….) LH 2 (PIBETA) CH 2 (MEGA) LiH (  e  at SIN)

59. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting CH 2 target(1) Easy to handle Active (scintillator) but... Capture rate on Carbon ~1300 capture rate on protons (s-wave capture  Z 4 )  rate suppression by factor 650 Range R  p 3  a few cm  R/R~(200 m e /m  ) 1/2 f(E/m  ) (Segre’, Ritson,Rossi) ~3.5%  OK Background?

60. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting CH 2 target(2) Capture on C: dominant Radiative  - capture  ok. Dominant BKG is gamma from radiative pion capture + nuclear (i.e. few MeV) de- excitation Danger from  - C   0 B E Threshold ~10 MeV: no  - at rest (p th ~ 55 MeV/c)  0 emitted in forward direction

61. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Fitzgerald et al. “fast”  - on (CH 2 ) N Comparable rate (incoherent capture,a factor of three expected) BKG measured with graphite target 14 MeV difference! C-ex on CarbonC-ex on H  0 kinetic energy

62. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Applied in MEGA A CH 2 calibration target was used in MEGA The BKG “from  - c-ex in flight is visible in the low energy tail” Could be measured (graphite target) and subtracted 3.3%FWHM 5.7%FWHM

63. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Possibility of CH 2 ? A clear peak is visible We can trigger on the target Need to measure BKG with Carbon target? RATE??

64. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Hydrogen target The most “natural” choice  = 0.071 g/cm 3 Range: p = 80 MeV/c  R  14 cm,  R  0.5 cm 110 MeV/c  R  41 cm,  R  1.4 cm LH 2 Already available  = 6.7  10 -3 g/cm 3 Range: p = 80 MeV/c  R  150 cm,  R  5.6 cm 110 MeV/c  R  450 cm,  R  15 cm GH 2

65. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Rate dp/p up to 0.8% FWHM  - flux ~ 8·10 5 /s at 1.6mA

66. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting 1999 measurement D=100 cm 10 x 10 window 9.5 hours no light in LYSO 60 cm (NaI) 75 cm (CsI) 11 x 13 window 10%FWHM

67. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Cryostat Design

68. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Cryostat Fabrizio Raffaelli has joined the design/construction group for the cryostat. All information can be found at http://meg.psi.chhttp://meg.psi.ch  subproject  calorimeter  Design and Construction…

69. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 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).

70. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Stress Distribution

71. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Deformation

72. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Strength Calculation for the G10 Support and the Brace

73. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 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.

74. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Metal gasket for the inner vessel flanges Flange Cover One possible manufacture (in Japan) is USUI. –Usage condition Pressure: 0 - 0.3 MPa Temperature: -110 ~ 100 degree C Fluid: Liquid xenon Flange and bolt: SUS316L –U-tight seal dimension Cross section: 5.5 mm diam Material: Aluminum(outer), Stainless(Inner), Spring(Inconel) Special Shape  We need a mold for casting.

75. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting T. Haruyama’s talk on Jul 2002 review meeting

76. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Operation Scheme T. Haruyama’s talk on Jul 2002 review meeting

77. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Some questions and remarks after seeing the Cryostat drawings by Fabrizio Raffaelli Which is the design pressure for the inner vessel ? Is the testing procedure has been already studied during the fabrication steps and which are the final acceptance tests? Is the safety has been already studied? The of safety relief devices are already implemented? For instance if there is a xenon leak into the vacuum the pressure on the outer vessel can increase more than 1 atm. Is the cold sealing has been already chosen and which are the specification for the groove accuracy ? Is the cold window has been already studied ? The pre-cooling system is already implemented in the inner vessel but its efficiency is already studied? Is an heating system has been considered to empty the inner vessel? Which are the envisaged mounting steps? Which adjustments are envisaged to position the Inner vessel in cold condition ? A lot of other questions will raise going in the drawing details.

78. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Remarks after seeing the drawings: by Fabrizio Raffaelli Covers: I see that the polished area of the sealing surface is not protected and it is not well localized from the point of view of machining operations and further hands polished operation. The inner vessel flange is quite slim (30 mm) and I am worry that after the welding with the I.V. body we are not able to guarantee the necessary flatness. I think we need to study the technological construction step and may be weld a long collar before machining the flange. Since the shape of the cover is not simple the oring especially the cold one should be custum made and I think will require a mold.

79. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Photon Detector 2002200320042005 Test Milestone AssemblyDesignManufactoring Large PrototypeBeam Test Vessel DesignAssembly & Test PMT Delivery + Testing RefrigeratorManufactoringAssembly Liq. Purification AssemblyTest Manufactoring Engineering runs

80. Satoshi Mihara ICEPP, Univ. of Tokyo July 2003 MEG Review Meeting Summary Liquid Xenon optical properties (TN-020). PMT test facility (Phase I) is close to be operational. TERAS beam test results –Energy Resolution at 40 MeV ~2% in sigma –Needs more careful analysis to treat shallow events Large Prototype beam test at  E1 in Oct-Dec 03. –CH 2, GH 2, LH 2 Cryostat design will be finalized in 2003.