Xenon Detector Status
Liquid Xenon Detector Group
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 E5 Schedule
PMT R&D
Photocathode New breeder circuit with zener diodes Test under the COBRA magnetic field
MotivationUnder 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 R6041QNot 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 testedunder high rate background environment.
K-Sc-Sb + Al strip used in R9288Al 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 PatternLow surface resistance
R9288 ZA series
Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004
R6041Q (Rb-Sc-Sb w/o Al strip used in LP)
0
0.5
1
1.5
2
2.5
3
0 50 100 150 200 250
ratioratio(LED)
Serial #
Beam on
83MeV
55MeV
Lab test
Test LED with crowing LED (0.8 microA)
-105oC 25oC
Only base currentshortage effect
Works on Design of PMT
Two Issues to be solved:1. 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 CurrentAns. 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
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.
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
Upper
Lower
SUM
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
I=4 A
TB604
ZA1985
ZA1980
Pla
teau
/Pea
k
New 9288 (ZA1980 and ZA1985) compared to TB604 (in Ar gas and LXe)
PMT Rate Dependence Test in Tokyo
Xe tankLiq.Xe chamber
Purification system
PMT Test facility @Univ. of Tokyo
Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004
Set up
alpha source
LED
Chamber Inside
PMT
Alpha source(241Am )
LED
Liq. Xe
Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004
Condition & Procedure
alpha source : ~200Hz, LED pulse height:4000p.e. ~ 7200 p.e./event
pulse shape: ~10nsecrate: 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
ZA1984 Rate Dependence @Liq.Xe Gain 1*106
Background: 2.16µA1.26*107p.e./sec
6.91µA4.05*107p.e./sec
ZA1984Time dependence? = 4.45 *104sec
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
ZA1984 Rate Dependence @Liq.Xe
Current of Crowding LED [ µA]
alpha peak (@LED ON) / alpha peak (@LED OFF)
This instability is caused not by photocathodebut by the bleeder circuit;Shortage of bleeder current
Improved design of the bleeder Circuit;adding Zener Diode
Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004
Final Design of Bleeder Circuit
NEC RD68S
NEC RD82S
Provide Voltage regulation with Zener Diode
Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004
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
Type Zener Volt.[V] Min Zener Volt.[V]Max Temp. Coeff.[mV/oC]
RD68S 64.00 72.00 ~70
RD82S 77.00 87.00 ~83
So tiny..
Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004
Electrical Characteristic @Low temp.
Electrical Characteristics of NEC Zener Diode were measured at room temperature and in liq. N2Set up:
NEC RD68S, 82S.2 samples for each were testedin liq. N2.
Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004
Electrical Characteristic @Low temp.
Current [µA]
Zener voltage [V]
Room Temp. Liq.N2
RD68S
RD82S
No damage to the package Can be used in liq.XeSharp voltage drop at zener volt. also at low temp. generate good reference volt.Zener Voltage decreased by ~13V Reasonable (Temp.Coeff.)
Measured by Hiroaki NATORI
Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004
Conclusion Stable output from R9288 ZA series under the
background up to 4A in PISA PMT test facility Stable output up to 2A (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
PMT test under the magnetic field Gain, effective QE of 2 PMTs were
measured under the magnetic field.
Geometry definition
Setting
PMT test box with a PMT and a blue LEDCOBRA full excitation Isc : 360A, Inc : 320A
gain:(1.32±0.03)x106 (750V) : TB0585 : (1.73±0.03)x106 (750V) : TB0473
PMT
LED
TB0585
Magnetic field around LXe position was reduced successfully by compensation coil, less than 40G.
Inner Face Outer Face
Side Face Front Face
○ 90°(weak)× 0°(normal)▲ mag. field
TB0473○ 90°(weak)× 0°(normal)▲ mag. field
Inner Face Outer Face
Side Face Front Face
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).
Gain curve Effective QE
No magnetic field62G data
SummaryPMT test under the COBRA mag.
fieldResponse 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.
Cryostat/PMT holder design
Cryostat construction PMT holder design Cryogenics system design
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 Requirements3.1 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
PMT support structure
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
Outer
Side
Front (up)
Front (low)
768 PMTsIf we get more, we can put moreon the outer side.
Structure of slab/plateSide Outer
Front
InnerPossible to divide into 6 slabs
Assembling
Several technical issues Easy maintenance Assembling w/o crane
in clean environment Relative position
Mating parts between the support and slab
Through screw holes
1 2 3
4 5
Main support frames
Support for the front
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.
Cold Vessel
Patch Panel
feedthrough
Warm Vessel
Cryogenic System Design
Xenon strage/1000 L Dewar/Purifier Storage tanks ready at PSI 1000 L dewar design completed Purifier on the way to PSI
(16/June)
PMT Calibrations
Alpha-on-a-wireSimulation of a wire in the Large PrototypeSimulation 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
z
x
Large prototype: how many sources? 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”
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
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
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
Front face averages
Alpha/gamma ID
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
Full reconstruction alpha
Front face fit
Another CEX beam test at E5
DAQ using almost final electronics/software Wave-form digitizer Software framework
Investigate Al-grid PMT performance Gain experience for using - beam at E5 (and
hydrogen target)
Schedule2002 2003 2004 2005
Test MilestoneAssemblyDesign Manufacturing
Large Prototype Beam Test Beam Test
Cryostat Vessel
PMT
Refrigerator
Liq. Purification
AssemblyTest
Engineering runs
Heater replaced
Neutron background measurement
Base circuit design must be finalized
Crane problem
NeutronShield?
Schedule in 2004
LPTNeutr.
BGPM + Src Inst
Pi- Beam
Test
Liq.
Purif.
Full Calorimete
r
Jun/2004 Jul/2004 Aug/2004 Sep/2004 Oct/2004 Nov/2004 Dec/2004
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
Construction
Schedule in 2005
LPT
PMT testing + calibration
Full
Calorimeter
Cryo.
Installation
Crane+
Tent
AssemblyStudies
(Wed + remote)
Test
Jan-Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan
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
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