Xenon Detector Status

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Xenon Detector Status

• Liquid Xenon Detector Group

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Contents

• PMT RD
• 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

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PMT RD

• Photocathode
• New breeder circuit with zener diodes
• Test under the COBRA magnetic field

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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 _at_PSI June 2004
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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
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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 _at_ Liq.Xe
HPK has started to work on new bleeder circuit
design
Yasuko HISAMATSU MEG VRVS Meeting _at_PSI June 2004
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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

Gas
Liquid
Lower
Upper
SUM
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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 -109C
  (1 Atm)
• Note usually Xe kept at -105, 1.3 Atm
• ZA1985
• ZA1980

Crowding ON OFF
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New 9288 (ZA1980 and ZA1985) compared to TB604
(in Ar gas and LXe)
I4 ?A
Plateau/Peak
TB604
ZA1980
ZA1985
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PMT Rate Dependence Test in Tokyo
Purification system
Liq.Xe chamber
PMT Test facility _at_Univ. of Tokyo
Xe tank
Yasuko HISAMATSU MEG VRVS Meeting _at_PSI June 2004
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Set up
Chamber Inside
Liq. Xe
alpha source
Alpha source(241Am ) LED
LED
PMT
Yasuko HISAMATSU MEG VRVS Meeting _at_PSI June 2004
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Condition Procedure

• alpha source 200Hz,
• LED pulse height4000p.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 _at_ LED OFF
• Alpha Run _at_ LED ON (LED high rate
  background)
• -Change LED Pulse height, rate and PMT
  gain

Yasuko HISAMATSU MEG VRVS Meeting _at_PSI June 2004
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ZA1984 Rate Dependence _at_Liq.Xe
Time dependence? ? 4.45 104sec

• Gain 1106

ZA1984
Background
2.16µA 1.26107p.e./sec
6.91µA 4.05107p.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 _at_PSI June 2004
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ZA1984 Rate Dependence _at_Liq.Xe
alpha peak (_at_LED ON) / alpha peak (_at_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 _at_PSI June 2004
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Final Design of Bleeder Circuit
Provide Voltage regulation with Zener Diode
NEC RD68S
NEC RD82S
Yasuko HISAMATSU MEG VRVS Meeting _at_PSI June 2004
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Zener Diode NEC RD Series

• Low noise zener recommended by HPK
• Plastic package
• Electrical Characteristic (T25oC)
• Data sheet
• http//www.necel.com/nesdis/image/D11444EJ5V0DS00.
  pdf

Type Zener Volt.V Min Zener Volt.VMax Temp. Coeff.mV/oC
RD68S 64.00 72.00 70
RD82S 77.00 87.00 83
So tiny..
Yasuko HISAMATSU MEG VRVS Meeting _at_PSI June 2004
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Electrical Characteristic _at_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 _at_PSI June 2004
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Electrical Characteristic _at_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 _at_PSI June 2004
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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 _at_PSI June 2004
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(No Transcript)
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PMT test under the magnetic field

• Gain, effective QE of 2 PMTs were measured under
  the magnetic field.

Geometry definition
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Setting
PMT test box with a PMT and a blue LED COBRA
full excitation Isc 360A, Inc
320A gain(1.320.03)x106 (750V) TB0585
(1.730.03)x106 (750V) TB0473
LED
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TB0585
Inner Face
Outer Face
? 90(weak) 0(normal) ? mag. field
Side Face
Front Face

• Magnetic field around LXe position was reduced
  successfully by compensation coil, less than 40G.

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TB0473
? 90(weak) 0(normal) ? mag. field
Outer Face
Inner Face
Front Face
Side Face
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GainEff.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).

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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.

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Cryostat/PMT holder design

• Cryostat construction
• PMT holder design
• Cryogenics system design

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Cryostat Design

• 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

Delivery in Summer 2005 after all tests in a
manufacturer
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PMT support structure
768 PMTs If we get more, we can put more on the
outer side.
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.
• Patch panel
• Temperature sensor
• Level meter

Inner
Side
Front (low)
Outer
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Structure of slab/plate
Side
Outer
Front
Inner
Possible to divide into 6 slabs
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Assembling
Main support frames
1
2
3
Support for the front

• Several technical issues
• Easy maintenance
• Assembling w/o crane in clean environment
• Relative position
• Mating parts between the support and slab
• Through screw holes

4
5
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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.

Patch Panel
feedthrough
Cold Vessel
Warm Vessel
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Cryogenic System Design
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Xenon strage/1000 L Dewar/Purifier

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

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PMT Calibrations

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

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Large prototype how many sources?
z

• 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

x
Simple average
"Opposite" average
Full reconstruction
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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
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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

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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?)
• gt15 p.e. for d(pmt)lt35 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

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Front face averages
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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
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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)

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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?
Test
Milestone
Assembly
Design
Manufacturing
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Schedule in 2004
Jun/2004
Jul/2004
Aug/2004
Sep/2004
Oct/2004
Nov/2004
Dec/2004
LPT Neutr. BG Neutr. BG Neutr. BG Neutr. BG Neutr. BG Neutr. BG PM Src Inst PM Src Inst PM Src Inst PM Src Inst Pi- Beam Test Pi- Beam Test Pi- Beam Test Pi- Beam Test Pi- Beam Test Pi- Beam Test Pi- Beam Test Pi- Beam Test Liq. Purif. Liq. Purif. Liq. Purif. Liq. Purif.
Full Calorimeter
Construction

• 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

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Schedule in 2005
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Jan-Mar
Apr
LPT PMT testing calibration PMT testing calibration PMT testing calibration PMT testing calibration PMT testing calibration PMT testing calibration PMT testing calibration PMT testing calibration PMT testing calibration PMT testing calibration PMT testing calibration PMT testing calibration PMT testing calibration PMT testing calibration PMT testing calibration
Full Calorimeter Cryo. Installation Crane Tent Assembly Assembly Assembly Assembly Assembly Assembly Assembly Studies (Wed remote) Studies (Wed remote) Studies (Wed remote) Studies (Wed remote) Studies (Wed remote) Studies (Wed remote) Studies (Wed remote) Studies (Wed remote) Studies (Wed remote) Studies (Wed remote) Studies (Wed remote) Test Test Test Test

• 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