Xenon Detector HardwareXenon Detector Hardware

Liquid Xenon Group

2

OutlineOutline

• Detector in 2008

• Operation in 2008

• Hardware Upgrade and Schedule

• Summary

DetectorDetector

4

PMTs installationPMTs installation• All PMTs were taken away for

check and reinstalled in the cryostat

– New LED on the outer side for better calib. of inner PMTs

– Wire alpha sources are at staggered positions

• Better PMT calibration– Alpha sources (all) on walls were

removed

25mm

31mm

5

New LEDsNew LEDs

• Higher voltage with attenuation by coating LEDS

• Stable against instability of the input voltage

6

Problem in 2007 OperationProblem in 2007 Operation

Production procedure

•Fix pins in the holes and fill with silica

•Bake in argon atmosphere

•Cool down

Metal body

Glass insulator

Air

Xe

Wataru’s Design – Solution for 2007 run

No need to change connector

Replacement can be done quickly

Body made of insulator (not metal)

7

HV Feedthru ModificationHV Feedthru Modification

• Test of new feedthru– 1000 V applied on all

pins (48x6x4 pins)– One feedthru (48

pins) was tested at 1500V

• Successfully installed

welding

ceramic

Kyocera Ultra High Vacuum Feedthrough

New HV feedthru

8

New LN2 feedthru InstallationNew LN2 feedthru Installation• Pressure was slowly increasing under

normal operating condition in 2007 runs• 6 new LN2 feedthru have been installed

– Stainless steel pipes instead of Cu pipes– Pipes are precisely and strongly

centered in order not to touch the wall– Bellows connection for the cooling pipes

on the covers• 30-40W reduction of heat load was

achieved• But … still pressure is slowly

increasing….!!!!!!!!!!

PMTCableChimneyRadiationSupportCu pipe?

?

Pipes

PMTs

Cables

•Refrigerator cooling power: 200W

9

Liquid circulation (Original Design)Liquid circulation (Original Design)• Circulate xenon in liquid phase

– Circulation pump• 100liter/h@3175rpm, p = 0.2MPa

– Molecular sieves• >24 g water absorption

• Used in 2007 run

Temperature Sensor

Purifier Cartridge

Molecular sieves, 13X 25g water

Freq. InverterOMRON

PT

10

Electronegative Impurity RemovalElectronegative Impurity Removal(Update in 2008 Run)(Update in 2008 Run)

• O2 getter cartridge– Developed for LAr use at CERN– Mounted at the exit MEG liquid-

phase purifier with by-pass valves

11

Liquid-phase Purifier ModificationLiquid-phase Purifier Modification

• New purifier cartridge to remove water– Oxidization-reduction of Cu– Outside of the purifier cryostat

• MS is replaced to new pellet– Particle filter has been installed

12

Modification of Splitter-DRS Connections/CablesModification of Splitter-DRS Connections/Cables• GND line from splitter floating grounding on

DRS board• Copper tape + black tape

DRS pedestal distribution before/after modification

13

175ns

97ns

NaI Electronics UpdateNaI Electronics Update

charge amp.charge amp. gn0261 gn0261 (hiroshima-(hiroshima-univ.)univ.)

inverting inverting amp.amp.and timing and timing filterfilter

APD

Light guide

9 amplifiers prepared, installed all on 17/Jun and checked all signal before connecting to splitter

rising time97ns for fast trigger

225ns (in 2007) ->175ns

replaced only amplifiers

energy outputby new setup

500ns

DRS

output for trigger

• output for energy measurement is also faster than that in 2007

14

New Scintillation CountersNew Scintillation Counters

• Used for time calibration of LXe– Scintillator x 2

• 70mm x 70mm x 7.4mm– Fine mesh PMT x 4

• Hamamatsu H6152-70– Pb converter

CO

BR

ANaI

OperationOperation

16

Gas/liquid systemGas/liquid system

Gas-phase purifier

Liquid-phase purifier

Detector1000L dewar

High pressureStorage

Gas line

Liquid line

17

Scintillation Light YieldScintillation Light Yield

• In 2007 operation, there was an energy scale discrepancy btw alpha and gamma– Too small light yield from events (

< 1/2)

• Purity seemed to be good because we observed– Improvement and plateau of light yield

of both gammas and alphas

• but <Q/A> / <Q/A> was found to be smaller than expectation and LP data

2007 Data

18

triplet= 22 ns

recomb= 45 ns

Waveforms (Shown in 2008 Review)Waveforms (Shown in 2008 Review)

= 21 ns

= 34 ns

! Careful treatment of electronics time constant is necessary

Xe

Xe X

e

Xe

Xe

Xe X

e

Xe

ee

ee

ee

A

Q

Q/A

Before purification 02.025.1/

/

AQ

AQ

was 1.93+/-0.02 in LP test

Electronegative impurity?

Oxygen??

2007 Data

19

Scintillation Light in 2008 RunScintillation Light in 2008 Run

• Rapid increase at the beginning thanks to the liquid-phase purification

– Removal of water/oxygen– LN2 cooling was necessary to help limited

cooling power during purification• Increase (~14%) in summer by gaseous

purification, however this was not significant• Large increase (46%!) in Oct-Dec after

replacing the diaphragm of the gas-circulating pump

205 h

2/Dec

180 h

23/Nov

70 h

14/Nov

2007

20

Why did it change in such way?Why did it change in such way?

• LN2 cooling pipe– In the cryostat– On the inner vessel wall and

covers

• Diaphragm– found to be broken in September

21

LED Light as a MonitorLED Light as a Monitor

• It is found that our LED system has very good stability.– Much more stable than our calibration precision– We can monitor the stability by a number of PMTs.

22

PMT Gain ShiftPMT Gain Shift

• Gain decrease in pi0 runs• PMT gain shift was found with muon beam on ( 2~3% )

– Time constant : short and long– CR peak during MEG run– LED run with normal muon beam– LED constant intensity with open/close beam blocker

Beam on

Beam off

23

Hamamatsu InvestigationHamamatsu Investigation

R9869 Gain Shift vs SKB

0.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

19 120

223

359

475

545

636

714

793

867

943

1032

1112

1258

1341

1436

1501

1634

1719

1783

1851

1902

1948

Serial No.

Gai

n Sh

ift

2

3

4

5

6

7

8

SKB

GainShift

SKB

Too much alkali ?????

24

Yet Another Way to Monitor the LightYet Another Way to Monitor the Light

• (Cosmic ray)

• Am-Be alpha source

Hardware UpgradeHardware Upgradeand Scheduleand Schedule

26

Work during the shutdownWork during the shutdown• PMT/Cryostat

– Open the downstream cryostat cover– Visual inspection of the cryostat– Take a few PMT to be sent back to

Hamamatsu for further investigation of gain change

– Installation of a new chimney cover with steel cooling pipe (previous one was made of Cu)

• Replacement of the 1000L dewar heater– Recovery of xenon to the storage in Feb– Replacement of the heater and warm up

frozen xenon in Mar– Liquefaction in April

• Installation of new getter in March on the top of the cryostat

• Installation of new Liquid Pump/Purifier in April

– 1000 L/hour circulation expected– No electric noise

27

Liquid filling scheduleLiquid filling schedule

• Detector– 6-19/April

• Evacuation

– 20-22/April• pre-cooling

– 23-24/April• cold gas alpha DAQ

– 25-26/April• Liquid transfer

– 27/April-10/May• Electronics test• Purifier test

– 11/May-• Purification and test

• 1000L dewar– 26/Jan-27/Feb

• Recovery of xenon to the storage

– 2/Mar-6/Mar• Recovery of the gas in the

dewar

– 9/Mar-13/Mar• Repair work of the heater

– 14/Mar-1/April• Evacuation

– 2/April-22/April• Liquefaction

– Complete removal of impurities

Summary

• Successful running in 2008– Remaining problems

• Scintillation light yield (30% less than LP data)• Cooling power

• Hardware upgrade/repair– New Getter purifier– New liquid pump– Replacement of the top chimney cover

• LN2 cooling pipe: Cu Stainless Steel– Replacement of the heater in the 1000L dewar

• PMT gain shift investigation is in progress by Hamamatsu

• Detector will be ready in the middle of May