MEG

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MEG??????????????????? ??PMT???????????
???????60????? ????????????? 2005?3?24?
???? ???, ????, ????, ???, ?????, ????,
????, ???, ????, ???, ???,
???, ???? ?????? ???, ???, ????, ???? ???
????, ????, ???? ETH M.
Schneebeli INFN-Pisa A.Baldini, F.Cei,
S.Giurgola, M.Grassi, D.Nicolo, A.Papa,
G.Signorelli PSI P.-R. Kettle,
S.Ritt
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Contents
p- beam test was performed to estimate resolution
in signal and higher energy region. (55 MeV and
83 MeV)
Updates and comparison of p- beam test in 2003
and 2004.

• p- beam test
• Updates from previous beam test
• Analysis
• Energy resolution
• Time resolution
• Summary

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p beam test
LXe detector
NaI LYSO
LH2 target
??
83 MeV
p-p?p0n p0(28MeV/c) ? ? ? 54.9 MeV lt ?(?) lt
82.9 ?eV
170o
175o
Requiring ?gt170? FWHM 1.3 MeV Requiring ?
gt 175o FWHM 0.3 MeV
55 MeV
?
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Result of Run-2003
Energy resolution
Time resolution
FWHM 4.5 0.3 s(right) 1.60 0.07
stXenon 102 psec
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Updates from previous test

• Result of beam test 2003
• Energy 1.6 (right s)
• Time 102 psec
• Updates from previous beam test
• Improvement of PMT
• Newly installed calibration source
• Filled space in beam window to reduce
  inefficiency.
• High power refrigerator (189W_at_165K)
• Waveform digitizer
• New analysis softwares ( ROME )

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Improvement of PMT
24pWJ H,Natoris talk
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Newly installed a source

• 4 tungsten wires plated with Au (50 micron f)
• Po attached on the wires, 2 active points per
  wire
• Active points are coated with Au (200-400Å)
• Fixed on the wall with spring.

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Analysis of alpha
Alpha source are used for Q.E. estimation
purity monitor optimization of MC
Q.E. of PMTs
Output of a PMT
1st generation
with ? selection
2nd generation
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Energy Resolution
s 1.23
3cm
20cm
Energy ( of photons)
s 1.00
Depth ( arbitrary unit )

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Energy resolution analysis
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Intrinsic Time Resolution
L-R Analysis to ged rid of affection from
conversion depth reconstruction.
56 psec
Gain
43 psec
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Absolute Time Resolution
st(Xe-LYSO) contains resolution of LYSO gt
61psec effect from beam spot and target size.
60psec
110 psec
103 psec
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Absolute Time Resolution
st(Xe-LYSO) contains resolution of LYSO gt
61psec effect from beam spot and target size.
60psec
110 psec
103 psec
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Practical Time Resolution
Practical timing resolution of Xe
LYSO
target
Intrinsic
depth
110 ? 64 ? 61 65 56 ? 33 psec
103 ? 64 ? 61 53 43 ? 31 psec
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Comparison 20032004
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Summary of p beam test

• Many updates from previous test
• PMT, calibration source, refrigerator, reduction
  of material, waveform, software ...
• Energy resolution for 55 MeV gamma rays were
  improved from 1.6 to 1.2.
• Time resolution for 55 MeV gamma rays were
  improved from 100 psec to 50 psec.

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Summary of prototype tests
Prototype test is completed.

• Energyposition resolution for 10,20,40 MeV
  gammas _at_ TERAS
• Energytime resolution for 55,83 MeV gammas _at_ p-
  beam test
• Liquefaction and keep LXe only with refrigerator
• Attenuation length measurement and purification
  technique (pre-print physics/0407033)
• PMT development and test
• Calibration and reconstruction algorithms
• High speed purification with liquid pump (lt100
  l/hrs).

MEG signal
Final detector is under construction.
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Liquid phase purification
Liquid phase (high speed) purification was
successfully done.
Purifier
Teflon tube
Pump head