satoshi mihara icepp, univ. of tokyo july 2003 meg review meeting liquid xenon detector and related...

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.MiharaFor Liquid Xenon Detector Group


LXe optical properties (MEG-TN020)

• The λatt, λabs 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 λR (LP) measurement of n


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


Check linearity at different wavelengths

On the absorption lines the FLL function is only marginally valid butit can be considered an acceptable approximation still at the LXe

emission line...


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


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


A relation between n and λR

• In gaseous phase:

• In liquid phase: fluctuations (Einstein equation)

• Hence:

• A measurement of λR gives a hint on n

• λR = (29 ± 2) cm* n = (1.71 ± 0.015) !

* Ishida et al, NIM A384 (1997) 380

8th power


PMT Test Facility


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 1 MANUAL OPERATION WITH LXe EMPTING/FILLING FOR EACH PMTPHASE 2 MANUAL OPERATION WITHOUT LXe EMPTINGPHASE 3 TEST 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


MEG – PMTct – Cryogenic/Vacuum Diagram

Phase II


MEG – PMTct - Cryostat


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!


…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


Calibration source and (+LED)

-source that is stable in liquid Xenon:– 3 kBq 241Am 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


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.


TERAS BEAM TEST

• Overview of the test• Energy measurement• Position reconstruction• Timing measurement


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


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


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


• D: depth parameter MC simulation Data

Previous Test

This Test

Short abs

Long abs

D=

D

DD

DD

D: 20~100 0~25cm


Effect of Material

• 5mmt, 10mmt, 15mmt Al

• 15mmt Al+4mmt Stainless Steel

• 5mmt Pb

2nd collimator

Al, Stainless, Pb plates

LP5mm Al 0.053X0

10mm Al 0.11X0

15mm Al 0.16X0

15mm Al + 4mm Stainless Stell 0.398X0

5mmt Pb 0.89X0

COBRA thickness: 0.197 X0


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


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)


Energy Measurement


Energy Spectrum Fitting

• Principle…

E Npe

Response functionCompton Spectrum

Convolution of

Compton Spectrum

Response Function

•For understanding simply…•Suppose Response function is an asymmetric Gaussian

left

right


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+Ec2/4

• Detector Response Function– Gaussian with Exponential tailf(x) = Nexp{t/2(t/2-(x-x0)}, x<x0+t

Nexp{-1/2((x-x0)/)2}, x>x0+t

• Convolution– Integration +/- 5 Fitting is done in two steps

•Determine the edge position

•Fix the edge in the 2nd 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%


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.

0

5000

10000

15000

20000

25000

30000

35000

0 10 20 30 40 50 60

Egamma(MeV)

Qsu

m

0

1

2

3

4

5

0 10 20 30 40 50

Egamma(MeV)

Res

olut

ion

(%)


Energy Resolution vs. Depth Parameter

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

30 40 50 60 70 80 90

Sigma2 threshold

Res

olut

ion

(%)

Number of Photoelectrons

D

• For incident at the detector center

• D > 35, 45, 55….85

• Resolution: < 2% in sigma except shallow events (D<45).


Material Effect on the Resolution

• No apparent deterioration of the resolution

• Loss of efficiency

0

0.5

1

1.5

2

2.5

3

0 0.2 0.4 0.6 0.8 1

Length in X0

Res

olut

ion(

%)

COBRA Thickness

Trigger Threshold

Al 5mm Pb 5mm


Position Dependence

1.85% in

1.83% in

1.80% in


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


VLP and Curved DetectorShape studies:Compare LiXe and a VLP (100 x 50 x 50 cm3) 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 m3) of Xenon would be needed (and PMTs!).


TERAS DataOnly 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/Npe

1/sqrt(Npe)



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 Npe.

• PMTs on the side walls compensate 1st conversion point dependence.



D D


Effect of a “faulty” PMT

• All PMTs on: =1.8%

• Switching off one PMT on the front wall.

– the nearest PMT =2.3%

– 2nd nearest PMT =1.9%

– 3rd 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%


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


Simple Average Method

• Data and MC are in good agreement.

• Reconstruction “bias” exists.Depth Depth

Depth


Localized Weight Method

• Projection to x and y directions.

• Peak point and distribution spread

•Position reconstruction using the selected PMT


Samples of Reconstruction

1mm


Reconstruction “Bias”


Position ReconstructionResolution


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 1s 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.


Timing MeasurementVery Preliminary Result

We observed that

1. Timing resolution improves as the PMT gain increases.

2. Timing resolution improves as Npe 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


Open Questions

• Compton Spectrum Shape– Broader than simulated shape– Detector effect ?

• Reflection or absorption on the PMT window?

• Rate Dependence


Compton Spectrum Shape1. Broad peak of the total photoelectrons.

2. Many low energy events.

Maybe beam spectrum

We have not a clear answer

threshold


Comparison with revised MCCompton spectrum shape

• Electron beam spread at the collision point• Collimator position

Data

Data MC

MC


Reflection or Absorption on the PMT window?

(Qsum-Qfront)/Qsum

Qsum

D


Discrepancy at Low Energy Side

total photoelectrons total photoelectrons

0<z<3

z<0

z: first conversion depth [cm] , 0 means surface of LXe.

Data

Data MC

MC


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 60Co 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


Oct-Dec 03 Beam Test at E1


The elementary process

- (essentially) at rest captured on protons:

- p 0 n - p n

0

Photon spectrum

54.9 82.9 129 MeV


CM and Lab frame

M/2

M/2

M/2(1cos*)*

E=55 MeV * =


Angular selection

’s back to back in lab: 55 and 84 MeV

E/ E < 1% < 5o

•This fixes the angular acceptance to

610-4 /56* = 1.07 10-5

5o = 87mrad = 8.7cm @1m

*(83-55)/0.5

-


Experimental configuration

NaI

LXeCoincidence:

C & !A & NaI

(Offline: & LXe)

-- beam

AC T Mod

TARGET?•Rate

•Background

•Thin/small (angle/X0)

•Handling

Previous use

•GH2 (Panofsky….)

•LH2 (PIBETA)

•CH2 (MEGA)

•LiH (e at SIN)


CH2 target(1)

•Easy to handle

•Active (scintillator) but ...

•Capture rate on Carbon ~1300 capture rate on protons (s-wave capture Z4) rate suppression by factor 650

•Range R p3 a few cm

R/R~(200 me /m)1/2 f(E/m) (Segre’, Ritson,Rossi)

~3.5% OK

•Background?


Applied in MEGA•A CH2 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


Hydrogen target

•The most “natural” choice

= 0.071 g/cm3

•Range: p = 80 MeV/c R 14 cm, R 0.5 cm

110 MeV/c R 41 cm, R 1.4 cm

LH2

•Already available

= 6.710-3 g/cm3

•Range: p = 80 MeV/c R 150 cm, R 5.6 cm

110 MeV/c R 450 cm, R 15 cm

GH2


Rate

• dp/p up to 0.8% FWHM

- flux ~ 8·105/s at 1.6mA


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


Cryostat Design


Cryostat• Fabrizio Raffaelli has joined the design/construction group for the cry

ostat.

• All information can be found at http://meg.psi.chsubproject calorimeter Design and Construction…


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


Stress Distribution


Deformation


Strength Calculation forthe G10 Support and the Brace

Strength Calculation for the G10 support Unit Formula ValueW1 Inner Vessel weight kg 1200W2 Liquid xenon weight kg 2400W3 PMT weight kg 400W total weight kg W1+W2+W3 4000n number of support 2w weight/support kg W/n 2000d1 outer diameter of the support mm 115d2 inner diameter of the support mm 95s allowed strenght of G10 kg/mm2 10A cross section mm2 pi/4(d1^2-d2^2) 3298.6723Wr allowed weight s*A 32986.723Wr-w never negative kg Wr-W 30986.723

Strength Calculation for the brace Unit Formula ValueW1 Inner Vessel weight kg 1200W2 Liquid xenon weight kg 2400W3 PMT weight kg 400W total weight kg W1+W2+W3 4000n 6W weight/brace kg W/n 666.66667d1 outer diameter of the support mm 12d2 inner diameter of the support mm 0s allowed strenght of SUS kg/mm2 11.3A cross section mm2 pi/4(d1^2-d2^2) 113.09734Wr allowed weight s*A 1277.9999Wr-W never negative kg Wr-W 611.33322


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.

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


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(Inn

er), Spring(Inconel)

Special Shape

We need a mold for casting.


T. Haruyama’s talk on Jul 2002 review meeting


Operation SchemeDAY STEP MAN/

AUTOACTION EMERGENCY

- PUMPING/GAS CHARGE

MAN -OUTER VACUUM PUMPING-INNER VESSEL PUMPING-COLD TRAP ACTIVE

-POWER SHUT

3 BAKING MAN -HOT GAS TEMP. CONTROL -POWER SHUT4 PRECOOL AUTO -VESSEL PRESSURE CONTROL (LN2) -POWER SHUT

-LN2 EMPTY7 LIQUEFY AUTO -VESSEL PRESSURE CONTROL (LN2)

-TANK VALVE CHANGE CONTROL-PURIFIER ACTIVE

-POWER SHUT-LN2 EMPTY-VACUUM

7 CIRCULATION AUTO - PURIFICATION BY LIQUID PUMPOUT

-

-POWER SHUT-LN2 EMPTY-VACUUM

- STEADY AUTO - VESSEL PRESSURE CONTROL (REFRIG.+LN2 BACK-UP)

-POWER SHUT-REF. SHUT-LN2 EMPTY-VACUUM

7 RECOVERY SEMI -TANK UNIT COOLING-LN2 LEVELCONTROL-XE FLOW CONTROL TO TANKS

-LN2 EMPTY

5 WARM UP SEMI -HEATER CONTROL-VACUUM BREAK

T. Haruyama’s talk on Jul 2002 review meeting


Some questions and remarks after seeing the Cryostat drawingsby 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 x

enon 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 efficie

ncy 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.


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.


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


Summary

• Liquid Xenon optical properties (TN-020).• PMT test facility (Phase I) is close to be operation

al.• 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.– CH2, GH2, LH2

• Cryostat design will be finalized in 2003.

satoshi mihara icepp, univ. of tokyo july 2003 meg review meeting liquid xenon detector and related...

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