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Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Liquid Xenon Detector and Related Topics
• CEX beam test at piE1 Oct-Dec/03
• Detector calibration
• Other related topics– PMT R&D
– Refrigerator
– Liquid phase purification
– Cryostat
Liquid Xenon Detector Group
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
CEX beam test at piE1
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Elementary process
- (essentially) at rest captured on protons:
- p 0 n - p n
0
Photon spectrum
54.9 82.9 129MeV
M/2
M/2(1cos*)
M/2
*
E=55 MeV * =
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Angular selection -p0n
0(28MeV/c) MeV
eV
• Requiring
FWHM = 1.3 MeV
• Requiring > 175o
FWHM = 0.3 MeV
170o
175o
0
54.9MeV 82.9MeV
1.3MeV for >170o
0.3MeV for >175o
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
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 t
he target– S1 counter (40x40x5mm3) to defin
e the beam
• Area layout– The Electronics barrack placed in th
e 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 beamTarget
ASY51
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Setup
Carbon degrader
Lead Collimator at the beam line exit
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
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
NaI detector
• For tagging at the opposite side of LP 8x8 NaI crystals– 40.6x6.3x6.3cm3
• Located 110cm from the target
• Signal processor and Trigger Box (QUAD module) to provide trigger signal
A
B
C
D
E
F
G
H
8 7 6 5 4 3 2 1
For trigger
For trigger
Base Line
Stabilizer
Attenuator
x10
x10
ADC
Trigger
Box
TDC
Crystal Array
HV
Trigger module
Differential input stage
Differentiator, Attenuator and base line stabilizer
Output stage
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
NaICalibration
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
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
NaIEnergy 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)
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
NaIEnergy Resolution
• 55 MeV 7.0+/-0.13 %
• 83 MeV 6.5+/-0.14%
• 129 MeV 6.1+/-0.04%
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
NaIVertex 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 2.7cmy 1.6cm
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
LPNaI S1
TCtLP - tTC
Pb
!
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Timing Counterefficiency 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
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Xenon Large Prototypeoperating condition
• Gain/QE calibration– LED and as usual
• PMT gain 106, 5x106
• 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
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.
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) i
n front of NaI
Preamplifier Module
Av = 1
-In
+In
300
15050
CLC449
Av = +1
300
300
CLC44950
50
Av = -10
Discrete transistors
50
Av = +1
AD8001
32 Channels
8 units
Full-bandwidth Outs
Full-bandwidth Outs
Low range (x8 amplification)
Middle range
High range (20dB attenuation)
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 < 180o
– 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
123
4
5
6
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 @ 1800A
• Electron contamination in the beam– Negligible in triggered events
targetx=12mm
y=12mm
e/
~8nsec
TOF separation
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
0 signal example
LP ADC
NaI
AD
C
LP 83 MeV
NaI 55 MeV
LP 55 MeV
NaI 83 MeV
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 1.5x106 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
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Analysis
Energy Resolution
Time Resolution
Response to Neutrons
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Analysis Procedure
1. Start Counter• Selection of - beam
2. NaI Detector– Selecting 55MeV or 83MeV – For 129MeV no event selection applied on NaI
3. Xenon Large Prototype• Position reconstruction
• Weighted mean for x and y, and depth parameter• MINUIT fitting for 3D position finding
– Cut-base analysis– Linear-Fit analysis
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Position Reconstruction• Position:Position:
MINUIT fitMINUIT fit on the on the PMT distributionPMT distribution in the in the
entrance faceentrance face;;
Energy vs depthEnergy vs depth (X,Y) coordinates (X,Y) coordinates
CollimatorCollimator
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Nfpmt(0.5)• Another depth parameter: Nfpmt(0.5)
– Sort front-face PMTs in the order of the distance to the x-y weighted mean position.
– Sum up PMT output in that order.
– Stop summing when the sum exceeds the half of Qsum[Front].
Number of PMTs used in the SUM.
1.0
0.5
QPMT
NPMT
deep shallow Better resolution for
shallow events
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Energy Resolution
Cut-base AnalysisLinear Fit Analysis
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Energy Resolutioncut-base analysis
1. Remove pedestal events.
2. Select 0 events
3. Position selection in x-y, R<1.5cm
4. Reject shallow and too deep events
5. Rejection of z<0 events (resolution does not change effect of material)
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Energy Resolution cut-base analysis
• Correction of the depth dependence (10% improvement of the resolution)– Linear function
•FWHM = 4.5 ± 0.3 (left:2.7 + right:1.8) % ( of the right part: 1.53%)
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Linear Fit• A vector of parameters {pi} = E, , , z…
• A vector of observables {qj} = PMT charges
{qj} {pi}
All in a linearised way fast
Linearisation
Here are the formulas:
Generate a sample of MC events and find the best hyper-plane:
Minimize (analytically) the deviation between the linear approximation and the true pi values (ONCE AND FOR ALL)
ijjiji cqqwp )( 0
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Energy resolution @55 MeVEnergy resolution @55 MeV
No selectionsNo selections >2.5 cm from the >2.5 cm from the wallwall
13.5k events13.5k events
FWHM = 7.4 %FWHM = 7.4 %9.4k events (69 %)9.4k events (69 %)
FWHM = 6.5 %FWHM = 6.5 %
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Energy resolution @83 MeVEnergy resolution @83 MeV
No selectionsNo selections >2.5 cm from the >2.5 cm from the wallwall
FWHM = 6.9 %FWHM = 6.9 % FWHM = 6.9 %FWHM = 6.9 %
No effect (deeper No effect (deeper events)events)
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
MC predictions (MC predictions (absabs = 3 m) = 3 m)
55 MeV55 MeVFWHM 4.0 %FWHM 4.0 %
83 MeV83 MeVFWHM 3.8 %FWHM 3.8 %
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
LinearityLinearity
With the same set of coefficientsWith the same set of coefficients::
55 MeV55 MeV 83 MeV 4.4 MeV (Am/Be) 83 MeV 4.4 MeV (Am/Be)
EErecrec = 55.3 MeV = 55.3 MeVEErecrec = 83.7 MeV = 83.7 MeVEErecrec = 55.3 MeV = 55.3 MeV EErecrec = 4.2 MeV = 4.2 MeV
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Possible improvements - IPossible improvements - I
• Q.E.Q.E. Green: MCGreen: MCRed: dataRed: data with with Q.E. in gasQ.E. in gas
Charge distribution for data Charge distribution for data is is not so symmetricnot so symmetric as it as it should be …should be …
Q.E. Q.E. could be could be measured measured individuallyindividually in the in the Pisa Pisa cryogenic test facilitycryogenic test facility..
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
The The quality of the linear fitquality of the linear fit depends depends
very stronglyvery strongly on the on the MC/data agreementMC/data agreement ! !
MC refinementsMC refinements
- light collection/transport algorithms;- light collection/transport algorithms;
- Fresnel and/or total reflection;- Fresnel and/or total reflection;
- LXe scintillation light spectrum, - LXe scintillation light spectrum, absabs …. ….
Possible improvements - IIPossible improvements - II
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
The best that one can do …The best that one can do …
• Assume that the MC is correct Assume that the MC is correct
- determine a determine a “Q.E. set”“Q.E. set” comparing the comparing the expected expected and measured chargeand measured charge PMT by PMT; PMT by PMT;
- apply apply position cutsposition cuts to select the signal in a to select the signal in a restricted region. restricted region.
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
And this is the result …And this is the result …
Best result:Best result:
4.7 % FWHM4.7 % FWHM with: with: R < 1.5 cmR < 1.5 cmD from wall > 2.5 cmD from wall > 2.5 cm
No cutsNo cuts R < 3cmR < 3cm R < 3cm && D > 2.5 cmR < 3cm && D > 2.5 cm
R < 1.5 cmR < 1.5 cm
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Comparison between cut based (CB) and Comparison between cut based (CB) and linear fit (LF) analyseslinear fit (LF) analyses
( ) = QSUM > 25000( ) = QSUM > 25000
Step Number of Selection FWHM Cuts efficiencyevents (%) after step 2
55 MeV1 CB 82K (34K) 8.5 ± 0.31 LF 18106 6.9 ± 0.2
r < 1.5 cm2 CB 7160 (4223) 7.9 ± 0.9 1002 LF 2204 5.9 ± 0.3 100
Depth cut3 CB 3077 (2059) 4.9 ± 0.4 43 (48.8)3 LF 1235 4.8 ± 0.2 56
z<0 & depthcorrection
4 CB 2001 (1993) 4.5 ± 0.3 27.9 (47.2)4 LF 1235 4.8 ± 0.2 56
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Depth Cut Dependence(cut-base analysis)
• Events near the wall can be used with a bit poorer resolution: So the overall efficiency should be much higher.
No selection using depth
Nfpmt(0.5)>4
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Position Dependence of Resolution
4.3±1.0 4.8±0.4 4.6±0.7
4.5±0.6 4.5±0.3 4.5±0.6
4.1±0.9 5.0±0.5 5.0±1.6
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Masking Effect• Some PMTs are masked to simulate the curved shape of the final
detector.
without masking
edge of front
edge of front top,bottom
edge of front,top, bottom, right, and left
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Ongoing Analysis
• Energy Resolution for 83 and 129 MeV (including alpha and TERAS results).
• Other masking to simulate in case that we have only 600 PMTs.– 1/2 on back, top, and bottom planes.– 1/4 on left and right planes.
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Time Resolution(very preliminary)
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Time Resolution I(right – left)
• TDC correction for time-walk (no position correction)
• TL, TR by weighted average of Ti
• <T> = (TL-TR)/2
PMT
i
iii Ni
Q
ctT ,1 ,
/1
/
,
,
1
2,
1
2,,
,
RL
RL
N
iRiL
N
iRiLRiL
RL
TT
i=r.m.s. of Ti
cut on Qi> 5 peApplied cuts:
• r < 1cm (T40ps)
•52<S1TDC<53 ns, 70<RFTDC<76 ns
•Qsum>30000 ( E>50 MeV)
only 1000 events retained
= 86 ps
Analysis still going on …
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Time Resolution II(Xe – TC)
• Time walk correction for TC.– 60 psec () resolution
• Need correction for xenon– Time walk– Position (depth)
= 113psec at 5x106 gain• Beam profile: 1.2cm in 4cm diam. cyl
inder– 59 psec contribution () to tTC-tXe
96 psec in sigma
• Need to improve z (depth) resolution for improving time resolution
• And more …
LPNaI S1
TCtLP - tTC
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Response to Neutrons
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Neutron in the Large Prototyperecent measurement
γ energy spectrum
ADC
ADC
Without moderator (paraffin)
With moderator
Peak at 9.3 MeV
The neutron source is Am/Be (2 KBq) + diffused thermal neutron background in the experimental hall ( (?) note TN022 )
It can be improved: test with source on the calorimeter back and thicker moderator
γ energy spectrum
12216 scmn
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Trigger condition : S1 * NaI4 Gain:5e6, FSH52: 125
E(NaI)>100MeV, Qsum<20000
- + p + n data
Neutron delay ~ 30ns(120cm/0.14c)
No bias data for Xe
Require S1TDC, RFTDC data
n
Qsu
m
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Possible Detector Calibration Methods
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
The motivations
a frequent and precise check of the calorimeter stabilityeven during the normal data acquisition
An energy resolution of
Causes for gain instabilities:
• Beam intensity variations• Variable background rates (photons and neutrons in the experimental hall)• Effects of the temperature T variation on the photocathode Q.E. and resistivity• Effects due to the capacitive coupling• Possible hysteresis phenomena as a function of T
4%E/E (FWHM) means:
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Thermal neutron capturePossible source:
Pulsed neutron generator (commercialy produced)
Am/Be (~10 KBq)
• Continuous n spectrum
Moderator: ~10-20 cm of the polyethylene
γ shield:• 40% thermalized n•10% n captured in moderator~ 3 cm of the tungsten
• Neutron lines: 4.5 or 14 MeV (d-d or d-t reaction respectively) • Typical intensity is 106 n/s or 108 n/s• Typical pulse rate and pulse width 10Hz and 1μs •Price ~ 10000 $
Counts
0 10 MeV
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Precise calibration rarely performed
• γ‘s from decay (E(γ) ~ 54.9 MeV):
use of a liquid hydrogen target
• Optional calorimeter calibration over range of γ energies:γ‘s from a tagged electron beam (small magnet + MWPC’s)
θ (d
egre
es)
E (MeV)
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Calibrations to be frequently performed (A)
Thermal neutron in Xe• Absorption length ~ 3 cm• Capture close to calorimeter walls• Multi γ, Σ E(γ) = 9.3 MeV• Possible spill-out
Capture on Ni plate on calorimeter wall • Single γ emission highly probable 52.7%• E(γ) = 9.0 MeV (used in SK)
52.7% 25.6% 4.65% 1.28%
9.0 9.0 8.534 8.122 7.698 MeV
0
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Calibration to be frequently performed (B)
Other possibility (less recommanded):
Isotope activation far from detector with neutron generator and energetic neutron sources
• E(γ) = 6.13 MeV• Decay constant τ = 7.2 s
Possible reaction: or
Nitrogen laser UV: emission line at ~ 300 nm; use of the optical fibre and a small diffusor
• Gain and relative QE measurements
is PMT independent?
• No neutron on calorimeter (apart from hall background)
)175(
)330(
nmQE
nmQE
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
PMT Responseat high rates
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
A Problem with “Old” PMTs found:Dependence of PMT outputs on beam intensity
UV
BLUE
Beam on
Beam on onoff
83MeV
55MeV
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
The phenomenon reproduced by LED light simulating crowding (50 KHz of 5 MeV pulses) due to beam background
6 minutes
Neutrons rate during normal runs
Ia 0.6 A, Ib 70 A
Start crowd. Stop
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Beam on/Beam off
• PMT output for & LED– Compare and LED peak position between beam off and on.
0
0.5
1
1.5
2
2.5
3
0 50 100 150 200 250
ratioratio(LED)
Serial #
rati
o
s
ourc
esso
urc
es
LEDLED
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Cryogenics test facility at Pisa
• PMT tested in Ar gas at several temperatures (30 -120°C)
• Test LED (blue) pulse usually at 10-50 Hz, 300 mV, 20 ns wide
• Crowding LED (blue) 300 mV, 10-40 KHz, 20 ns wide (Ia=1,10 A)
• Crowding turned on and then off after some time
• One “old” PMT (6041) tested and the phenomenon reproduced
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
OLD (6041) PMT at –105 °C tested in Pisa facility
6020 120 Time (s)
3010 50 Time (s)
I crowding= 0.8 A
= 66 sec
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
PMT Test @ Univ. of Tokyo
PMT
PMT
Alpha source(241Am )
LED
Liq. Xe
5.5MeV alpha peak
PMT (Al Strip Type)
TB0094 TB0102 TB0286 TB0302
(now being analized…)
TB0284 TB0568
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
New PMT (9288)
• The prototype uses only “old” PMTs(6041).– New PMTs expected to behave better…
• Tests using new PMTs at low temperature are ongoing both in Pisa and Tokyo.
• Results will be reported at the review meeting.
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Crowding considerations in the LP + final detector
• From the measured thermal neutron rate in the exp. Hall (TN022) one can estimate I 0.5 A in the LP and 5-6 times bigger in the final detector
• If this current has to be lower than 1% of the base current (70 A) we have to screen the final detector from thermal neutrons
• The corresponding current from low energy photons from the muon radiative decy turns out to be lower than for neutrons: I 04 A in the final detector Taken from the photonis PMTs handbook
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Pulse Tube Refrigerator
1. Heat load and PT cryocooler 2. Further test and schedule
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
- Heat Load -
Heat LoadW@165K
Phase LXe(L)
PMT
Static PMT Cable
Total(W)
L.Proto 120 250 24 16 10 50Final 800 1000 20 65 45 130
-Based on the KEK-original PT cryocooler, Cryocooler with higher cooling power has been developed for the final calorimeter
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Technology transfered to
Iwatani Co., Ltd
Designed:
150 W @165K
Large Power Pulse Tube Cryocooler
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Large Power Pulse Tube Cryocooler
One for Columbia University
For Dark Matter SearchDesigned:
90 W@165K
3kWcompressor
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
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Large Power PT Cryocooler-Cooling power at 6.7kW compressor-
PT150 Cooling Power
0
50
100
150
200
250
60 80 100 120 140 160 180 200
Temperature (K)
Cool
ing
Pow
er (
W)
Q150 (W)
Qkek(W)
KEK originalfor Large Proto
For final calorimeter6.7kW, 4Hz
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
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Liquid Phase Purification
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
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
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
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Purification systemin the final detector
LXe CalorimeterLiquid 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
Gas phase purification
Liquid Phase purification
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
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Cryostat Construction
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.
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
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).
Walls/Cover Material DimensionPressureDirection
Design PressureMPa
Design Tempdegree C
ThicknessCalculation (mm)
Thickness Actual(mm)
Inner Vessel Inner Wall SUS316L R623 x L1086 Outer 0.3 -108~40 5.4 7.0Inner Vessel Outer Wall SUS316L R1116 x L1086 Inner 0.3 -108~40 3.0 7.0
Inner Vessel Front Wall SUS316L min504 x max1086 Inner 0.3 -108~40 23.0 24.0Inner Vessel Cover SUS316L R1148 x R588 Inner 0.3 -108~40 22.7 24.0
Outer Vessel Inner Wall SUS316L R550 x L1260 Inner 0.1 40.0 0.5 0.5Outer Vessel Outer Wall SUS316L R1200 x L1270 Outer 0.1 40.0 7.5 8.0Outer Vessel Front Wall SUS316L min650 x max1270 Outer 0.1 40.0 16.7 20.0Outer Vessel Cover SUS316L R1200 x R540 Outer 0.1 40.0 15.4 20.0
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
Heat load calcluation for the xenon photon detector vessel
UnitRadiation Outer Vessel -> Inner Vessel (30 Mylar layers) 3.1 WConduction Nozzle (N1-N3) via xenon gas 0.2 WConduction Nozzle (N1-N3) via belows 4.6 WConduction Support (brace and supporting pipe) 6.3 WHeat generation PMT (65mW/PMT) 52 WConduction PMT HV and Signal Cables 50 Wtotal 116.2 W
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Several modifications from the previous design
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Photon Detector
2002 2003 2004 2005
Test MilestoneAssemblyDesign Manufactoring
Large Prototype Beam Test Beam Test
Vessel Design Assembly & Test
PMT Delivery + Testing
Refrigerator Manufactoring Assembly
Liq. Purification
Assembly Test
Manufactoring
Engineering runs
Liquid Xenon Photon Detector Feb. 2004 MEG Review Meeting
Summary
• CEX beam test was carried out at E1 area.– Energy Resolution– Time Resolution
• PMT response at high rates is investigated.• Possible Calibration Method in consideration.• 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.
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