Transcript Xenon Detector Status

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
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Neutron BG measurement  Previous talk
Cryostat/PMT holder design
Calibration/Monitoring
Another CEX beam test at pE5
Schedule
PMT R&D
Photocathode
 New breeder circuit with zener diodes
 Test under the COBRA magnetic field

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
Al Strip Pattern
Low surface resistance
Add more Al Strip
R9288 ZA series
Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004
R6041Q
(Rb-Sc-Sb w/o Al strip used in LP)
3
ratio
ratio(LED)
2.5
2
1.5
1
83MeV g
0.5
0
0
50
100
150
200
250
Serial #
Lab test
55MeV g
Test LED with crowing LED (0.8 microA)
Only base current
shortage effect
Beam on
-105oC
25oC
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
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

Is operating stabily and allows to test PMTs in Lxe with
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Alpha sources (QE)
LEDs (high rate test)
Laser light through fiber (stability)
Compare each PMT to a reference PMT
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Reference PMT fixed. Change test PMT.
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PMT fast change mode successfully
tested
Linear motion to “dip” PMTs
Gate valve to isolate N2/Xe
 Allows to test several PMTs/day (5)
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Alpha-source signal
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Anticorrelation in liquid not seen in gas
 Purity of Xe? checking
Lower
Upper
SUM
High rate tests
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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
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ZA1985
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ZA1980
Crowding
ON
OFF
Plateau/Peak
New 9288 (ZA1980 and ZA1985)
compared to TB604 (in Ar gas and LXe)
I=4 A
TB604
ZA1980
ZA1985
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(241Am )
LED
LED
PMT
Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004
Condition & Procedure
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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
ZA1984 Rate Dependence @Liq.Xe

Gain 1*106
Background:
ZA1984
2.16µA
1.26*107p.e./sec
Time dependence?
 = 4.45 *104sec
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
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
Final Design of Bleeder Circuit
Provide Voltage regulation with Zener Diode
NEC RD68S
NEC RD82S
Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004
Zener Diode NEC RD Series
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Low noise zener recommended by HPK
Plastic package
Electrical Characteristic (T=25oC)
Zener Volt.[V]Max
Temp. Coeff.[mV/oC]
RD68S 64.00
72.00
~70
RD82S 77.00
87.00
~83
Type

Zener Volt.[V] Min
Data sheet:
http://www.necel.com/nesdis/image/D11444EJ5V0DS00.pdf
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. N2
Set up:
NEC RD68S, 82S.
2 samples for each were tested
in liq. N2.
Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004
Electrical Characteristic @Low temp.
RD68S
Current
[µA]
Zener voltage [V]
RD82S
Room Temp.
Liq.N2
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.)
Measured by Hiroaki NATORI
Yasuko HISAMATSU MEG VRVS Meeting @PSI June 2004
Conclusion
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Stable output from R9288 ZA series under the
background up to 4A in PISA PMT test facility
Stable output up to 2A (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 LED
COBRA full excitation Isc : 360A, Inc : 320A
gain:(1.32±0.03)x106 (750V) : TB0585
: (1.73±0.03)x106 (750V) : TB0473
LED
PMT
TB0585
○ 90°(weak)
× 0°(normal)
▲ mag. field
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Inner Face
Outer Face
Side Face
Front Face
Magnetic field around LXe position was reduced
successfully by compensation coil, less than 40G.
TB0473
○ 90°(weak)
× 0°(normal)
▲ mag. field
Inner Face
Outer Face
Side Face
Front Face
Gain&Eff.QE under mag. field of 62G
Gain curve
Effective QE
No magnetic field
62G data
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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).
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 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
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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 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.
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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
Assembling
Main support frames
1
2
3
Support for the front

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
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Feedthrough
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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
Cryogenic System Design
Xenon strage/1000 L Dewar/Purifier
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Storage tanks ready at PSI
1000 L dewar design completed
Purifier on the way to PSI
(16/June)
PMT Calibrations
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Alpha-on-a-wire
 Simulation
of a wire in the Large Prototype
 Simulation of the final calorimeter
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Neutron generators (AB’s talk in last meeting)
 Selective
activation (Ni)
 Acquiring information on availability/price
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Photons-from-the-back(AB’s talk in last
meeting)
 Feasibility study in progress
Large prototype: how many sources?
z
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3 sources placed along x (0,±10cm)
1 Wire 50 m thick
Search for a no time consuming source ID
x
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Front face average (usual fast method)
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2 opposite faces weighted average (the shadow effect
is compensated) 
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Wire shadow: 1.5 MeV “lost”
5 sources in LP
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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
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We checked the effect of the
wire presence on energy
resolution at 52.8 MeV
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Linear fit training with no wire
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Xe layer in front of the front
face PMTs as in the last test
C-shape calorimeter
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3 wires with 5 sources each (15 sources total)
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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
Full reconstruction alpha
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No problem with full
reconstruction (MC!!)
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LP: three or five sources
easily distinguishible

Final calorimeter: some
more work is needed to
distinguish all 15 sources.
photons
Front face fit
Another CEX beam test at pE5
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DAQ using almost final electronics/software
 Wave-form
digitizer
 Software framework
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Investigate Al-grid PMT performance
Gain experience for using p- beam at pE5 (and
hydrogen target)
Schedule
2002
2003
2004
2005
Crane problem
Large Prototype
Beam Test
Beam Test
Engineering runs
Cryostat Vessel
PMT
Test
Assembly
Refrigerator
Liq. Purification
Neutron background measurement
Base circuit design must be finalized
Heater replaced
Neutron
Shield?
Design
Manufacturing
Assembly
Test
Milestone
Schedule in 2004
Jun/2004
LPT
Full
Calor
imete
r
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
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Sep/2004
Oct/2004
Pi- Beam
Test
PM + Src
Inst
Nov/2004
Dec/2004
Liq.
Purif.
Construction
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

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Neutr.
BG
Aug/2004
Neutron background measurement using LP in June, July
Two Problems during start-up in June
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Jul/2004
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
Jan
PMT testing + calibration
Full
Calorimeter
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
Cryo.
Installation
C
r
a
n
e
+
T
e
n
t
T
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