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Xenon Detector Status

Explore advancements in PMT R&D with zener diode base design to reduce output deterioration caused by high-rate background. Learn about the development of new PMT types like the R9288 for stable performance in varying conditions.

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Xenon Detector Status

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  1. Xenon Detector Status Liquid Xenon Detector Group

  2. Contents • PMT R&D • New PMT with double Al strip • New base design with zener diodes • PMT response under the COBRA field • Neutron BG measurement  Previous talk • Cryostat/PMT holder design • Calibration/Monitoring • Another CEX beam test at pE5 • Schedule

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

  4. Motivation • Under high rate background, PMT output (old Type PMT, R6041Q) reduced by 10-20%. • This output deterioration has a time constant (order of 10min.): Related to the characteristics of photocathode whose surface resistance increases at low temperature. • Rb-Sc-Sb + Mn layer used in R6041Q • Not easy to obtain “high” gain. Need more alkali for higher gain. • Larger fraction of alkali changes the characteristic of PC at low temp. So, New Type PMTs, R9288 (TB series) were tested under high rate background environment. • K-Sc-Sb + Al strip used in R9288 • Al 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 Add more Al Strip Al Strip Pattern • Low surface resistance R9288 ZA series Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004

  5. R6041Q (Rb-Sc-Sb w/o Al strip used in LP) 83MeV g Serial # Lab test Test LED with crowing LED (0.8 microA) 55MeV g Only base current shortage effect Beam on -105oC 25oC

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

  7. PMT test facility in Pisa • Is operating stabily and allows to test PMTs in Lxe with • 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.

  8. PMT fast change mode successfully tested • Linear motion to “dip” PMTs • Gate valve to isolate N2/Xe • Allows to test several PMTs/day (5) • Alpha-source signal • Anticorrelation in liquid not seen in gas • Purity of Xe? checking Liquid Gas Lower Upper SUM

  9. High rate tests • 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 • ZA1985 • ZA1980 Crowding ON OFF

  10. New 9288 (ZA1980 and ZA1985) compared to TB604(in Ar gas and LXe) I=4 A Plateau/Peak TB604 ZA1980 ZA1985

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

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

  13. Condition & Procedure • alpha source : ~200Hz, • LED pulse height:4000p.e. ~ 7200 p.e./event pulse shape: ~10nsec rate: 500Hz ~ 10KHz • 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

  14. ZA1984 Rate Dependence @Liq.Xe Time dependence?  = 4.45 *104sec ZA1984 • Gain 1*106 Background: 2.16µA 1.26*107p.e./sec 6.91µA 4.05*107p.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

  15. ZA1984 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

  16. Final Design of Bleeder Circuit Provide Voltage regulation with Zener Diode NEC RD68S NEC RD82S Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004

  17. Zener Diode NEC RD Series • Low noise zener recommended by HPK • Plastic package • Electrical Characteristic (T=25oC) • Data sheet: http://www.necel.com/nesdis/image/D11444EJ5V0DS00.pdf So tiny.. Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004

  18. Electrical Characteristic @Low temp. • Electrical Characteristics of NEC Zener Diode were measured at room temperature and in liq. N2 • Set up: NEC RD68S, 82S. 2 samples for each were tested in liq. N2. Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004

  19. Electrical Characteristic @Low temp. • No damage to the package • Can be used in • liq.Xe • Sharp voltage drop at zener volt. also at low temp. generate good reference volt. • Zener Voltage decreased by ~13V Reasonable (Temp.Coeff.) RD68S Current [µA] Zener voltage [V] RD82S Room Temp. Liq.N2 Measured by Hiroaki NATORI Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004

  20. Conclusion • Stable output from R9288 ZA series under the background up to 4mA in PISA PMT test facility • Stable output up to 2mA (1.3 *107p.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

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

  22. PMT Setting PMT test box with a PMT and a blue LED COBRA full excitation Isc : 360A, Inc : 320A gain:(1.32±0.03)x106 (750V) : TB0585 : (1.73±0.03)x106 (750V) : TB0473 LED

  23. TB0585 ○90°(weak) ×0°(normal) ▲ mag. field Inner Face Outer Face • Magnetic field around LXe position was reduced successfully by compensation coil, less than 40G. Side Face Front Face

  24. TB0473 ○90°(weak) ×0°(normal) ▲ mag. field Outer Face Inner Face Front Face Side Face

  25. Gain curve Effective QE No magnetic field 62G data Gain&Eff.QE under mag. field of 62G • 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 40G (20% loss of effective QE at max).

  26. SummaryPMT 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 40G at all positions, and decrease of PMT output is found to be less than 40%. • Gain can be recovered with higher HV setting.

  27. Cryostat/PMT holder design • Cryostat construction • PMT holder design • Cryogenics system design

  28. 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 Cryostat Design Delivery in Summer 2005 after all tests in a manufacturer

  29. 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. Patch panel Temperature sensor Level meter PMT support structure 768 PMTs If we get more, we can put more on the outer side. Front (up) Inner Side Front (low) Outer

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

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

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

  33. Cryogenic System Design

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

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

  36. Large prototype: how many sources? z x • 3 sources placed along x (0,±10cm) • 1 Wire 50 m thick • Search for a no time consuming source ID • Front face average (usual fast method)  • 2 opposite faces weighted average (the shadow effect is compensated)  • Wire shadow: 1.5 MeV “lost” Simple average "Opposite" average Full reconstruction

  37. 5 sources in LP • 5 sources make a more symmetrical situation (same spacing as PMTs) • Identification still possible at more than 3 but worse than 3 sources "Opposite" average Full reconstruction

  38. No effect on energy resolution • We checked the effect of the wire presence on energy resolution at 52.8 MeV • Linear fit training with no wire • Xe layer in front of the front face PMTs as in the last test

  39. C-shape calorimeter • 3 wires with 5 sources each (15 sources total) • 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

  40. Front face averages

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

  42. Another CEX beam test at pE5 • DAQ using almost final electronics/software • Wave-form digitizer • Software framework • Investigate Al-grid PMT performance • Gain experience for using p- beam at pE5 (and hydrogen target)

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

  44. Neutron background measurement using LP in June, July Two Problems during start-up in June 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. PMT replacement and installation of a calibration wire (several active spots on a 100um wire.) is planned in Aug. Another CEX beam test is planned in Sep/Oct 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 2004 Jun/2004 Jul/2004 Aug/2004 Sep/2004 Oct/2004 Nov/2004 Dec/2004 Construction

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

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