Xenon Detector Status Liquid Xenon Detector Group Contents

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Xenon Detector Status Liquid Xenon Detector Group

Xenon Detector Status Liquid Xenon Detector Group

Contents n PMT R&D ¨ New PMT with double Al strip ¨ New base

Contents n PMT R&D ¨ New PMT with double Al strip ¨ New base design with zener diodes ¨ PMT response under the COBRA field n n n Neutron BG measurement Previous talk Cryostat/PMT holder design Calibration/Monitoring Another CEX beam test at p. E 5 Schedule

PMT R&D Photocathode n New breeder circuit with zener diodes n Test under the

PMT R&D Photocathode n New breeder circuit with zener diodes n Test under the COBRA magnetic field n

Motivation ØUnder high rate background, PMT output (old Type PMT, R 6041 Q) reduced

Motivation ØUnder high rate background, PMT output (old Type PMT, R 6041 Q) reduced by 10 -20%. ØThis output deterioration has a time constant (order of 10 min. ): Related to the characteristics of photocathode whose surface resistance increases at low temperature. ØRb-Sc-Sb + Mn layer used in R 6041 Q ØNot easy to obtain “high” gain. Need more alkali for higher gain. ØLarger fraction of alkali changes the characteristic of PC at low temp. So, New Type PMTs, R 9288 (TB series) were tested under high rate background environment. ØK-Sc-Sb + Al strip used in R 9288 ØAl strip, instead of Mn layer, to fit with the dynode pattern Confirmed stable output. ( Reported in last BVR) But slight reduction of output in very high rate BG Al Strip Pattern ØLow surface resistance Add more Al Strip R 9288 ZA series Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004

R 6041 Q (Rb-Sc-Sb w/o Al strip used in LP) 83 Me. V g

R 6041 Q (Rb-Sc-Sb w/o Al strip used in LP) 83 Me. V g Serial # Lab test 55 Me. V g Test LED with crowing LED (0. 8 micro. A) Only base current shortage effect Beam on -105 o. C 25 o. C

Works on Design of PMT Two Issues to be solved: 1. Output deterioration caused

Works on Design of PMT Two Issues to be solved: 1. Output deterioration caused by high rate background. 2. (Effects of ambient temperature on Photocathode ) 3. Ans. Reduce Surface Resistance by adding Aluminum Strip Pattern Delivered from HPK in April Rate Dependence Test @ Liq. Xe 2. Shortage of Bleeder Circuit Current Ans. Improve Design of the Circuit by adding Zener Diode HPK has started to work on new bleeder circuit design Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004

PMT test facility in Pisa n Is operating stabily and allows to test PMTs

PMT test facility in Pisa n Is operating stabily and allows to test PMTs in Lxe with ¨ ¨ ¨ n Alpha sources (QE) LEDs (high rate test) Laser light through fiber (stability) Compare each PMT to a reference PMT ¨ Reference PMT fixed. Change test PMT.

n PMT fast change mode successfully tested ¨ ¨ ¨ n Linear motion to

n PMT fast change mode successfully tested ¨ ¨ ¨ n Linear motion to “dip” PMTs Gate valve to isolate N 2/Xe Allows to test several PMTs/day (5) Alpha-source signal ¨ ¨ Anticorrelation in liquid not seen in gas Purity of Xe? checking Lower Upper SUM

High rate tests n n n In parallel with -source/purity tests Check on Double-Al-Grid

High rate tests n n n In parallel with -source/purity tests Check on Double-Al-Grid PMTs (unfortunately only 2 samples) NO effect seen at 4 A anodic current at -109°C (1 Atm) ¨ Note: usually Xe kept at -105, 1. 3 Atm n ZA 1985 n ZA 1980 Crowding ON OFF

Plateau/Peak New 9288 (ZA 1980 and ZA 1985) compared to TB 604 (in Ar

Plateau/Peak New 9288 (ZA 1980 and ZA 1985) compared to TB 604 (in Ar gas and LXe) I=4 A TB 604 ZA 1980 ZA 1985

PMT Rate Dependence Test in Tokyo Purification system Xe tank Liq. Xe chamber PMT

PMT Rate Dependence Test in Tokyo Purification system Xe tank Liq. Xe chamber PMT Test facility @Univ. of Tokyo Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004

Set up Chamber Inside Liq. Xe alpha source Alpha source(241 Am ) LED PMT

Set up Chamber Inside Liq. Xe alpha source Alpha source(241 Am ) LED PMT Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004

Condition & Procedure n n alpha source : ~200 Hz, LED pulse height: 4000

Condition & Procedure n n alpha source : ~200 Hz, LED pulse height: 4000 p. e. ~ 7200 p. e. /event pulse shape: ~10 nsec rate: 500 Hz ~ 10 KHz Trigger: alpha self trigger (veto by LED driver pulse) • Procedure • Pedestal Run & Gain calibration using LED Alpha Run @ LED OFF Alpha Run @ LED ON (LED : high rate background) -Change LED Pulse height, rate and PMT gain Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004

ZA 1984 Rate Dependence @Liq. Xe n Gain 1*106 Background: ZA 1984 2. 16µA

ZA 1984 Rate Dependence @Liq. Xe n Gain 1*106 Background: ZA 1984 2. 16µA 1. 26*107 p. e. /sec Time dependence? = 4. 45 *104 sec 6. 91µA 4. 05*107 p. e. /sec Stable output up to 2. 16µA is confirmed. Slight deterioration(? ) of output was observed under very severe background. Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004

ZA 1984 Rate Dependence @Liq. Xe alpha peak (@LED ON) / alpha peak (@LED

ZA 1984 Rate Dependence @Liq. Xe alpha peak (@LED ON) / alpha peak (@LED OFF) This instability is caused not by photocathode but by the bleeder circuit; Shortage of bleeder current Improved design of the bleeder Circuit; adding Zener Diode Current of Crowding LED [ µA] Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004

Final Design of Bleeder Circuit Provide Voltage regulation with Zener Diode NEC RD 68

Final Design of Bleeder Circuit Provide Voltage regulation with Zener Diode NEC RD 68 S NEC RD 82 S Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004

Zener Diode NEC RD Series n n n Low noise zener recommended by HPK

Zener Diode NEC RD Series n n n Low noise zener recommended by HPK Plastic package Electrical Characteristic (T=25 o. C) Type Zener Volt. [V] Min Zener Volt. [V]Max Temp. Coeff. [m. V/o. C] RD 68 S 64. 00 72. 00 ~70 RD 82 S 77. 00 87. 00 ~83 n Data sheet: http: //www. necel. com/nesdis/image/D 11444 EJ 5 V 0 DS 00. pdf So tiny. . Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004

Electrical Characteristic @Low temp. ØElectrical Characteristics of NEC Zener Diode were measured at room

Electrical Characteristic @Low temp. ØElectrical Characteristics of NEC Zener Diode were measured at room temperature and in liq. N 2 ØSet up: NEC RD 68 S, 82 S. 2 samples for each were tested in liq. N 2. Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004

Electrical Characteristic @Low temp. RD 68 S Current [µA] Zener voltage [V] RD 82

Electrical Characteristic @Low temp. RD 68 S Current [µA] Zener voltage [V] RD 82 S Room Temp. Liq. N 2 ØNo damage to the package Can be used in liq. Xe ØSharp voltage drop at zener volt. also at low temp. generate good reference volt. ØZener Voltage decreased by ~13 V Reasonable (Temp. Coeff. ) Measured by Hiroaki NATORI Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004

Conclusion n n n Stable output from R 9288 ZA series under the background

Conclusion n n n Stable output from R 9288 ZA series under the background up to 4 A in PISA PMT test facility Stable output up to 2 A (1. 3 *107 p. e. /sec) was confirmed also in Tokyo PMT test facility Electrical characteristics of Zener diode at low temperature were measured. Confirmed that zener diode can be safely used at low temperature. Start drawing final design of PMT bleeder circuit at HPK Waiting for final PMT prototype from HPK! Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004

PMT test under the magnetic field n Gain, effective QE of 2 PMTs were

PMT test under the magnetic field n Gain, effective QE of 2 PMTs were measured under the magnetic field. Geometry definition

Setting PMT test box with a PMT and a blue LED COBRA full excitation

Setting PMT test box with a PMT and a blue LED COBRA full excitation Isc : 360 A, Inc : 320 A gain: (1. 32± 0. 03)x 106 (750 V) : TB 0585 : (1. 73± 0. 03)x 106 (750 V) : TB 0473 LED PMT

TB 0585 ○ 90°(weak) × 0°(normal) ▲ mag. field n Inner Face Outer Face

TB 0585 ○ 90°(weak) × 0°(normal) ▲ mag. field n Inner Face Outer Face Side Face Front Face Magnetic field around LXe position was reduced successfully by compensation coil, less than 40 G.

TB 0473 ○ 90°(weak) × 0°(normal) ▲ mag. field Inner Face Outer Face Side

TB 0473 ○ 90°(weak) × 0°(normal) ▲ mag. field Inner Face Outer Face Side Face Front Face

Gain&Eff. QE under mag. field of 62 G Gain curve Effective QE No magnetic

Gain&Eff. QE under mag. field of 62 G Gain curve Effective QE No magnetic field 62 G data n n n Gain can be recovered with higher HV. Effective QE (measured with LED light) is not recovered even when HV changed. The magnetic field in the LXe region is well below 40 G (20% loss of effective QE at max).

Summary PMT test under the COBRA mag. field ¨Response of the two sample PMTs

Summary PMT test under the COBRA mag. field ¨Response of the two sample PMTs was tested under the COBRA magnetic field. ¨The magnetic field at realistic position of LXe is successfully compensated, less than 40 G at all positions, and decrease of PMT output is found to be less than 40%. ¨Gain can be recovered with higher HV setting.

Cryostat/PMT holder design Cryostat construction n PMT holder design n Cryogenics system design n

Cryostat/PMT holder design Cryostat construction n PMT holder design n Cryogenics system design n

Cryostat Design Delivery in Summer 2005 after all tests in a manufacturer Summary: This

Cryostat Design Delivery in Summer 2005 after all tests in a manufacturer Summary: This document is the specification reference for the builder of the MEG cryostat and it is organized in three main sections: General: 1. 1 Introduction. 1. 2 Project description. 1. 3 Scope of work. Technical Requirements: 2. 1 General technical requirements. 2. 4 Recommendations for storage. 2. 7 Recommendations for cleaning. 2. 8 Packing and transportation. 2. 9 Mechanical and leakage tests 2. 10 Inspection, test and quality control plan. Management Requirements 3. 1 Fabrication and control plan. 3. 2 List of certificates and documentation required. 3. 3 Schedule for construction, test and shipment. 3. 4 List of drawing

PMT support structure 768 PMTs If we get more, we can put more on

PMT support structure 768 PMTs If we get more, we can put more on the outer side. n Front (up) Basic ideas PMTs are inserted in slabs (inner, side, outer) and plates (front) in a clean condition. ¨ The slabs and plates are assembled into a shape in the cryostat. ¨ Supporting frames for the slabs and plates will be fixed to the cryostat with screws. ¨ Some other equipments will be attached on the supporting frames. ¨ n n n Patch panel Temperature sensor Level meter Inner Side Front (low) Outer

Structure of slab/plate Side Outer Front Possible to divide into 6 slabs Inner

Structure of slab/plate Side Outer Front Possible to divide into 6 slabs Inner

Assembling 1 Main support frames 2 3 Support for the front n 4 5

Assembling 1 Main support frames 2 3 Support for the front n 4 5 Several technical issues Easy maintenance ¨ Assembling w/o crane in clean environment ¨ Relative position ¨ Mating parts between the support and slab Through screw holes

Patch Panel n Feedthrough ¨ High density due to limited space on the chimneys.

Patch Panel n Feedthrough ¨ High density due to limited space on the chimneys. A bundle of cables will be connected to one feedthrough connector. n Cabling (grouping of PMTs) are limited due to the slab structure. n Grouping of PMTs can be arranged between the patch panel and feedthrough connector. Patch Panel feedthrough Cold Vessel Warm Vessel

Cryogenic System Design

Cryogenic System Design

Xenon strage/1000 L Dewar/Purifier n n n Storage tanks ready at PSI 1000 L

Xenon strage/1000 L Dewar/Purifier n n n Storage tanks ready at PSI 1000 L dewar design completed Purifier on the way to PSI (16/June)

PMT Calibrations n Alpha-on-a-wire ¨ Simulation of a wire in the Large Prototype ¨

PMT Calibrations n Alpha-on-a-wire ¨ Simulation of a wire in the Large Prototype ¨ Simulation of the final calorimeter n Neutron generators (AB’s talk in last meeting) ¨ Selective activation (Ni) ¨ Acquiring information on availability/price n Photons-from-the-back(AB’s talk in last meeting) ¨ Feasibility study in progress

Large prototype: how many sources? n n n 3 sources placed along x (0,

Large prototype: how many sources? n n n 3 sources placed along x (0, ± 10 cm) 1 Wire 50 m thick Search for a no time consuming source ID z x Front face average (usual fast method) ¨ 2 opposite faces weighted average (the shadow effect is compensated) ¨ Wire shadow: 1. 5 Me. V “lost” ¨

5 sources in LP n n 5 sources make a more symmetrical situation (same

5 sources in LP n n 5 sources make a more symmetrical situation (same spacing as PMTs) Identification still possible at more than 3 but worse than 3 sources

No effect on energy resolution n We checked the effect of the wire presence

No effect on energy resolution n We checked the effect of the wire presence on energy resolution at 52. 8 Me. V n Linear fit training with no wire n Xe layer in front of the front face PMTs as in the last test

C-shape calorimeter n 3 wires with 5 sources each (15 sources total) ¨ ¨

C-shape calorimeter n 3 wires with 5 sources each (15 sources total) ¨ ¨ ¨ n n 50 m wires 2 mm wide alpha deposit on the wires (0, 7. 5, 15 cm) from lateral face to lateral face Half radial depth = (0, 35 ) >15 p. e. for d(pmt)<35 cm (5% QE) Easy to identify the wire, a bit more difficult to identify the source (even in MC!!) Fast ID: front face averages ¨ Exploitation of the linear fit is in progress ¨

Front face averages

Front face averages

Alpha/gamma ID Full reconstruction alpha n No problem with full reconstruction (MC!!) n LP:

Alpha/gamma ID Full reconstruction alpha n No problem with full reconstruction (MC!!) n LP: three or five sources easily distinguishible n Final calorimeter: some more work is needed to distinguish all 15 sources. photons Front face fit

Another CEX beam test at p. E 5 n DAQ using almost final electronics/software

Another CEX beam test at p. E 5 n DAQ using almost final electronics/software ¨ Wave-form digitizer ¨ Software framework n n Investigate Al-grid PMT performance Gain experience for using p- beam at p. E 5 (and hydrogen target)

Schedule 2002 2003 2004 2005 Crane problem Large Prototype Beam Test Engineering runs Cryostat

Schedule 2002 2003 2004 2005 Crane problem Large Prototype Beam Test Engineering runs Cryostat Vessel PMT Test Assembly Refrigerator Neutron background measurement Liq. Purification Base circuit design must be finalized Heater replaced Neutron Shield? Design Manufacturing Assembly Test Milestone

Schedule in 2004 Jun/2004 LP T Neutr. BG Jul/2004 Aug/2004 PM + Src Inst

Schedule in 2004 Jun/2004 LP T Neutr. BG Jul/2004 Aug/2004 PM + Src Inst Sep/2004 Pi- Beam Test Oct/2004 Nov/2004 Dec/2004 Liq. Purif. Full Cal ori met er Neutron background measurement using LP in June, July Construction n n Two Problems during start-up in June ¨ ¨ n n PMT replacement and installation of a calibration wire (several active spots on a 100 um wire. ) is planned in Aug. Another CEX beam test is planned in Sep/Oct ¨ n n Getter (xenon purifier) problem (triac error) control board must be changed refrigerator problem (He leakage) Replaced to the final refrigerator which will be ready soon. Wave-form digitizer and new PMTs (at least on the front face) Liquid phase purifier test on LP will be performed in Nov/Dec In 2005 LP chamber will be used for PMT test/calibration

Schedule in 2005 Jan-Mar LPT Apr May Jun Jul Aug Sep Oct Nov Dec

Schedule in 2005 Jan-Mar LPT Apr May Jun Jul Aug Sep Oct Nov Dec Jan PMT testing + calibration Full Calorimeter n n n Cryo. Installation C r a n e + T e n t Test Assembly Studies (Wed + remote) Jan-Mar/2005 Equipment installation (cryogenics, xe strage tank…) Aug-Sep/2005 PMT assembly in the cryostat Oct-Dec/2005 Operation test under the magnetic field will continue