Xenon Detector Status Liquid Xenon Group Outline Detector

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Xenon Detector Status Liquid Xenon Group

Xenon Detector Status Liquid Xenon Group

Outline • Detector Setup • Operation • Performance • Problems and solutions 1

Outline • Detector Setup • Operation • Performance • Problems and solutions 1

Detector Setup

Detector Setup

PMT installation completed • All PMT successfully installed in Aug 2007 together with –

PMT installation completed • All PMT successfully installed in Aug 2007 together with – – – LEDs Alpha sources (plates and wires) PT 100 temperature sensors Laser fibers Surface level meter • < 200~300 um gap btw inner slab and wall g xenon 3

Sensors, LEDs, and alpha sources Capacitor-type surface level meter Pt 100 Temp sensor 22

Sensors, LEDs, and alpha sources Capacitor-type surface level meter Pt 100 Temp sensor 22 sensors in LXe 21 sensors on the wall Two type of a sources • Plate 20 pieces • Wire 5 x 5 wires LED 3 different attenuation x 10 4

Cabling and Al filler installation 7. 5 l 4. 5 l • Filler volume

Cabling and Al filler installation 7. 5 l 4. 5 l • Filler volume – Lateral 7. 5 lx 6 x 2 + 4. 5 lx 2 x 2 = 108 l (design) 108 – 7. 5(US) – 4. 5(DS) = 96 l (reality) – Bottom 49 l (design) 49 – 10 = 39 l (reality) 5

We were ready to close but… • The shape of the newly delivered sealing

We were ready to close but… • The shape of the newly delivered sealing (metal gasket) was wrong ! – Does not fit the groove? ! – Radii were correct but they made a mistake in bending – Sent back to Garlok and repaired • While waiting repair work, old gaskets were recycled with indium foil around the corner – Vacuum test OK – But leak of the order of 10 -4 mbarl/sec with ~1 bar xenon in the cold vessel outgas ~1 bar xenon vacuum Warm vessel vacuum Xe leak Mass spectrometer 6

RGA of leaking xenon • Doubly charged 132 Xe (Xe++) is used to evaluate

RGA of leaking xenon • Doubly charged 132 Xe (Xe++) is used to evaluate amount of xenon in the warm vessel • Production cross section with 110 ke. V electron is ~40% of Xe+ production • Used as reference data for later use 10 -4 mbarl/sec leak 7

Closing the covers • Gaskets replaced with newly delivered ones on 5/Sep • Super-insulator

Closing the covers • Gaskets replaced with newly delivered ones on 5/Sep • Super-insulator on the cold vessel • 240 Nmm torque 8

Pressure/leak test • • • Xenon gas (liquid) in the cold vessel Mass spectrometer

Pressure/leak test • • • Xenon gas (liquid) in the cold vessel Mass spectrometer on the warm vessel RGA data with recycled gasket used as a reference 10 -4 mbarl/sec leak – Doubly charged 132 Xe (Xe++) is used to evaluate amount of xenon in the warm vessel – Production cross section with 110 ke. V electron is ~40% of Xe+ production 9

Estimation of xenon leak rate Recycled gasket 10 -4 mbarl/sec leak Room temperature xenon

Estimation of xenon leak rate Recycled gasket 10 -4 mbarl/sec leak Room temperature xenon gas New gasket Room temperature xenon gas Better at low temperature 10

Operation

Operation

Gas/liquid system Gas-phase purifier Gas line Liquid line Detector 1000 L dewar Liquidphase purifier

Gas/liquid system Gas-phase purifier Gas line Liquid line Detector 1000 L dewar Liquidphase purifier High pressur e Storage 12

Evacuation and liquefaction • Evacuation started on 5/Sep – Thanks to cryo pump (AISIN)

Evacuation and liquefaction • Evacuation started on 5/Sep – Thanks to cryo pump (AISIN) – 6. 9 x 10 -3 Pa in 3 days Cryo pump • Cooling started on 10/Sep • Liquefaction started on 15/Sep 0. 133 MPa Xenon gas 0. 11 MPa • Surface level was monitored with – Temperature sensors – Level meter (long and short) 13

Liquid transfer • Liquid transfer by pressure difference between two cryostats through a vacuum

Liquid transfer • Liquid transfer by pressure difference between two cryostats through a vacuum insulated pipe • Started on 17/Sep and completed on 20/Sep – 10 liter/hour transfer speed • Xenon filling was done in 15 days after starting evacuation Xenon liquid ~3 m 0. 25 MPa 0. 11 MPa 14

End of xenon filling temperature Level meter • Additional 10 liter was transferred for

End of xenon filling temperature Level meter • Additional 10 liter was transferred for assurance 15

How many liters of liquid xenon? • Cryostat volume 1200 liter • PMT and

How many liters of liquid xenon? • Cryostat volume 1200 liter • PMT and support 142 + 43 = 185 liter • Filler 135 liter – Lateral – Bottom • Cable 96 liter 39 liter 20~30 liter • Additionally transferred amount of xenon ~10 liter • 1200 – 185 – 135 – 25 + 10 = 865 liter • Consistent with remaining amount of xenon in the dewar 16

Labview Slow Control megon 00 PC in barrack MEG Central DAQ System For shift

Labview Slow Control megon 00 PC in barrack MEG Central DAQ System For shift crew use Labview (SCFE) XEC PC 2 XEC dedicated SCFE Node cooperation Alarm to experts XEC PC 1 For expert use Important controls are implemented in SCS nodes Detector, storage, dewar, purifiers 17

Liquid circulation • Circulate xenon in liquid phase – Circulation pump • 100 liter/h@3175

Liquid circulation • Circulate xenon in liquid phase – Circulation pump • 100 liter/[email protected] rpm, Dp = 0. 2 MPa – Molecular sieves Purifier Cartridge Molecular sieves, 13 X 25 g water PT Freq. Inverter OMRON • >24 g water absorption Temperature Sensor 18

Succeeded! Circulation period 50. 63 Hz ! Circulation speed evaluation • change of the

Succeeded! Circulation period 50. 63 Hz ! Circulation speed evaluation • change of the surface level after closing the inlet valve • 3. 6% / 30 sec ~ 432% / h • 1% corresponds to 0. 165 liter 0. 165 x 432%/h = 71 liter /hour 19

Liquid-phase purification • • Light yield for 17. 6 Me. V g saturated around

Liquid-phase purification • • Light yield for 17. 6 Me. V g saturated around 23/Nov (180 h purification time) Necessary to continue longer than we expected – 5 hours purification was enough in the LP test (100 L LXe) – Probably due to • slower circulation speed (100 L/h 70 L/h) • Worse initial condition compared to the LP • • Needed longer time to prepare monitoring tools due to PMT HV feedthru problem (reported later) Noise from the pump (freq. inverter? ) affected other detectors C-W run 17. 6 Me. V gamma 180 h 205 h 23/Nov 2/Dec 70 h 14/Nov 20

Absorption Length l > 3 m @95 % C. L. • Ratio Data/MC vs

Absorption Length l > 3 m @95 % C. L. • Ratio Data/MC vs distance fitted with an exponential curve. • Inner and Outer face PMTs • Cosine of incidence angle < -0. 2 • Slope compatible with zero (no absorption). After 50 h purification, 4/Nov Alpha source PMT 21

2 D display, charge/time 2 D hist, charge: PMT# 3 D reconstructed position Performance

2 D display, charge/time 2 D hist, charge: PMT# 3 D reconstructed position Performance Waveform 1 D histograms Charge: event#

PMT Calibration • PMT calibration – LED • PMT gain – Flushing LEDs at

PMT Calibration • PMT calibration – LED • PMT gain – Flushing LEDs at different intensities – Npe~1/s 2 • Time offset calibration – Viewing one LED flushing with many PMTs simultaneously – Alpha • QE and absorption length evaluation • Liquid and cold gas 23

Time offset determination • • Possible method only in non-segmented detector like ours c’

Time offset determination • • Possible method only in non-segmented detector like ours c’ is obtained by using all data Different LEDs viewed by one PMT Measured Flashing Time Of Speed of LED light Offset of j-th PMT i-th LED Tj RD run (ultra low) ti –ti-1 1/c’ li, j-li-1, j txe - t. TC 24

C-W run • Li at 14. 6, 17. 6 Me. V • B at

C-W run • Li at 14. 6, 17. 6 Me. V • B at 4. 4, 11. 7 and 16. 1 Me. V • Details in Giovanni’s presentation 25

CEX run - Pi 0 calibration • Eg CEX process – 170 o •

CEX run - Pi 0 calibration • Eg CEX process – 170 o • p 0(28 Me. V/c) g g • 54. 9 Me. V < E(g) < 82. 9 Me. V q Eg • 54. 9 Me. V p-p p 0 n LH 2 target p 0 1. 3 Me. V for q>170 o 175 o 0. 3 Me. V for q>175 o Eg q • 82. 9 Me. V Eg Na. I tagging counter – 3 x 3 crystals, APD readout g • Pb collimator panel in front of the Xe detector 26

LH 2 Target • Pressure test of cell 4. 5 bar (abs) • Time

LH 2 Target • Pressure test of cell 4. 5 bar (abs) • Time to liquefy – 80 min from start of LHe flow • Liquid stability – 1. 2 bar operating pressure (96% cell full) – 1. 3% RMS, 6% max excursion • Liquid Helium consumption – 2. 4%/h – 42 h auto 27

(+/ bea +/- m ax is 21 - 0. 07) deg. Na. I Detector

(+/ bea +/- m ax is 21 - 0. 07) deg. Na. I Detector Up/down +/- 60 (+/- 0. 005) deg. 28

CEX run data analysis, preliminary • • • Position cut – Cut shallow events

CEX run data analysis, preliminary • • • Position cut – Cut shallow events (< 2 cm) – Select only center events ( |u|, |v| < 5 cm) Position correction Pile-up rejection by light distribution Select center event on Na. I detector Not applied QE correction – If applied worsen resolution. Pedestal has 2% spread – Needs better baseline evaluation – Check hardware for 2008 run 55 Me. V gamma pedestal sup = 2. 4% FWHM = 6. 5% 29

Time Measurement • Using only 12 PMTs around the center Intrinsic resolution by T-B

Time Measurement • Using only 12 PMTs around the center Intrinsic resolution by T-B analsysis 115 ps Practical resolution by t. Xe – tsci 280 ps T : weighted mean of inner PMT timing after subtracting photon propagation time Effective velocity 10 cm/ns 30

Position Measurement • Using collimator run data, 31

Position Measurement • Using collimator run data, 31

Physics run • RD run gamma energy – Data : Xe self trigger threshold=3.

Physics run • RD run gamma energy – Data : Xe self trigger threshold=3. 5 V – MC : RD event generation + event overlaps + trigger simulation • Vertical scale is scaled assuming, – Mu stop = 5 e 6 – Calorimeter acceptance = 0. 1 – Calorimeter detection efficiency = 0. 6 32

Problems found in 2007 and solutions for 2008 run

Problems found in 2007 and solutions for 2008 run

Feedthru • We could not apply required voltage on all PMTs at the beginning

Feedthru • We could not apply required voltage on all PMTs at the beginning • We found that this had been caused by spark in the feedthru • Needed to prepare “new ones” for 2007 run – Commercial products or hand made? 34

How did we make new ones? Wataru’s Design Air Metal body Glass insulator Xe

How did we make new ones? Wataru’s Design Air Metal body Glass insulator Xe Production procedure • Fix pins in the holes and fill with silica • Bake in argon atmosphere • Cool down No need to change connector Replacement can be done quickly Body made of insulator (not metal) 35

Installation • Oct. 10 -12: LXe recovery to 1000 L Dewar • Oct. 13

Installation • Oct. 10 -12: LXe recovery to 1000 L Dewar • Oct. 13 -14: GXe recovery • Oct. 15 -16: Mounting new flanges & testing – With flushing dry nitrogen gas in the cryostat • Oct 17 -19: evacuation • Gas filling ~0. 13 MPa – Successfully took gas alpha data at 800, 900, 1000 V – LED data • Liquid transfer started at almost same time – Until the detector is cooled we continued LED and alpha DAQ – 21, 22, 23/Oct transfer speed 15~20 liter/hour – Completed early morning of 24/Oct • 2 weeks interruption of DAQ 36

PMT status after replacing feedthru • Stable operation after replacing feedthru • LED intensity

PMT status after replacing feedthru • Stable operation after replacing feedthru • LED intensity optimization – Better gain evaluation than before 37

As a bonus… • Xenon recovered through purifier – Practice to transfer the liquid

As a bonus… • Xenon recovered through purifier – Practice to transfer the liquid to the dewar – Water contamination suppressed • Cryostat was warmed up to ~220 K – 1 st experience of temperature cycle – Test of the gasket – RGA: I = 3. 8 x 10 -13 A 5. 7 x 10 -7 mbarl/sec 132 Xe++ 38

Future plan (currently ongoing) • Replacement during winter shutdown – 48 pin x 6

Future plan (currently ongoing) • Replacement during winter shutdown – 48 pin x 6 x 4 – Need to change connectors – Used in the small prototype and PMT test chamber ceramic Kyocera Ultra High Vacuum Feedthrough welding 39

Heat load • • • Pressure is slowly increasing under normal operating condition. Refrigerator

Heat load • • • Pressure is slowly increasing under normal operating condition. Refrigerator cooling power: 200 W Expected redundant cooling power: ~100 W – – – Calculation based on LP modeling PMT: 37 W (Vmean = 775 V) Conduction: 64 W • • Cable (50), Chimney (4. 8), SI(3. 1), Support(6. 3) Cables Heat income through Cu cooling pipes was not taken into account – Cu heat conduction: 390 W/m/K • • • ? PMTs 10 mm diam 1 mmt pipe, 20 cm 390 x 135 (K) x 2. 83 x 10 -5/0. 2 (m) = 7. 4 W 6 pipes 44. 4 W Cf. Steel heat conduction ~20 W/m/K Pipes There seems to be other heat leak… – – Larger than 50 W Super-insulator? 40

LN 2 cooling pipe • Cu pipe feedthru SUS pipe feedthru 41

LN 2 cooling pipe • Cu pipe feedthru SUS pipe feedthru 41

Cooling Power 42

Cooling Power 42

Blow up of low temperature valve • Low temperature valves blew up – A

Blow up of low temperature valve • Low temperature valves blew up – A few liters of liquid xenon was lost • Purifier cryostat was opened – Misleading valve design – No documentation on the manual • Piping was modified and no valve is in use now Wilson Seal Air Wilson Seal xenon Plug or shaft PT Cup nut collar bellows O-ring Liquid xenon 43

PMT Signal Splitter • Spark in feedthru’s destroyed protection zener diodes on PMT splitter

PMT Signal Splitter • Spark in feedthru’s destroyed protection zener diodes on PMT splitter boards – base-line shift at splitter output – Signal was out of range of WFD • Fixed by replacing all zener diodes splitter DRS PMT Trigger 44

Light Yield Discrepancy between a and g data • Energy scale discrepancy btw alpha

Light Yield Discrepancy between a and g data • Energy scale discrepancy btw alpha and gamma – Too small light yield from g events (~1/2) – Not due to magnetic field • Confirmed by taking C-W data w/o COBRA field • Purity seems good Improvement and plateau of light yield of both gammas and alphas • Have a look on WF a 45

Waveforms • triplet= 22 ns • recomb= 45 ns g = 34 ns a

Waveforms • triplet= 22 ns • recomb= 45 ns g = 34 ns a = 21 ns g Xe Xe a e ! Careful treatment of electronics time constant is necessary e Xe Before purification Q/A was 1. 93+/-0. 02 in LP test A Q Electronegative impurity? Oxygen? ? 46

Electronegative Impurity Removal • O 2 getter cartridge – Developed for LAr use at

Electronegative Impurity Removal • O 2 getter cartridge – Developed for LAr use at CERN – be mounted at the exit MEG liquid-phase purifier with by-pass valves – Preparing an oxygen purity monitor also – will be ready at an early stage of 2008 run 47

Current Status and Schedule • Xenon recovered to the 1000 liter dewar – Gas

Current Status and Schedule • Xenon recovered to the 1000 liter dewar – Gas analysis will be done on site • Cryostat is opened now – All PMTs and cables are checked – Replacing feedthru is in progress – LN 2 cooling pipe modification • Cryostat will be moved back to Pi. E 5 at the end of March – Evacuation, liquid transfer, purification – Ready on 19/April – Schedule at http: //meg. web. psi. ch/subprojects/install/xenon. html 48