hbd gas and qe monitoring craig woody bnl hbd working group meeting october 19, 2005
TRANSCRIPT
HBD Gas and QE Monitoring
Craig Woody BNL
HBD Working Group Meeting
October 19, 2005
C.Woody, HBD Working Group Meeting, 10/19/05 2
HBD Gas System
Single pass system for Run 6
Input
Output
Not initially instrumented
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Gas Monitoring
McPherson 234/302 VUV spectrometer Uses pure argon as reference gas (no vacuum)
• H20• O2
• VUV transmission
Gas monitoring near detector (under stairs by labyrinth)
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Oxygen and Water Sensors
GE Infrastructure Sensing (GE Panametrics)MIS1 system
6 dual channel inputsOne moisture, one oxygen (aux input) per channel
Control unit in hand, sensors ordered
M2LR moisture probeO2X1 oxygen sensor
Will monitor H2O and O2 on common gas input and
separately on east and west detector outputs
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Gas Transmission Monitoring
Based on McPherson 234/304 VUV monochrometer
Use high intensity D2 lamp to provide sufficient current for CsI PMTs operated in photodiode mode
Constant monitor of lamp intensity
Measure common gas input and east and west gas outputs separately using motorized translatable mirror.
D2 Lamp
Monochromator
Focusing elements
Beam Splitter
ReferenceCsI PMT
CsIPMTs
MgF2 Window
Gas CellsCommon input
East OutputWest output
MgF2 Window
Motor control
Movable Mirror
LC switch
pA
pA
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System Throughput
12 mm
Beam spot at end of 50 cm gas cell(12 mm collimator)
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McPherson System in HBD Lab
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Photocathode currents
D2 Lamp
Upper Beam
Light Coll. Box
Lower Beam
Slits
Monochromater
CrossBeam Splitter
Flux and PMT current measured at three locations:• Output of the light collection box• Top flange of cross• Lower flange of cross
PMT Current from Upper and Lower VUV Beam
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
1100 1200 1300 1400 1500 1600 1700 1800 1900
Wavelength [Angstroms]
PMT
Curr
ent [
nA] Upper
Lower
SUM
SLIT(ent./ext.) = 1.0/.1.0
Peak currents are ~ 260 pA@ 160 nm with a 30 W D2 lamp
Currents are < 10 pA below 120 nm
Probably will want to use 150 W D2 lamp (water cooled), but must check efficiency
B.Azmoun
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Keithley Current Measuring System
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Quantum Efficiency Monitoring
Two possible methods:
DC UV lamp and measure current• Measure current from mesh • Cannot easily measure using HV module (100 nA resolution)• Could use current switch and series picoammeter, but this complicates the HV distribution system
Pulsed UV lamp and use FEM readout
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Grounding System
HV Supply
LV Supply
FEM
PreampBoard
GEMDetector
HVDistribution
Box
+6.5 V-7.0 V
MVD Rack
return
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Xenon Flash Lamps
• Size ~ 20-30 mm diameter• Power: 10-20 W• Energy per pulse: 0.15-0.5 Joules ~ 2 x 1016 photons per pulse in wavelength range 100-200 nm• Time jitter ~ 100-200 ns• Frequency up to 300 Hz
Properties
• Time jitter requires external trigger• trigger from PPG (like EMCAL laser)• monitor with photodiode ( timing signal)
• Must provide large attenuation • Possible problem with RF noise
Possible Problems
Can test this with full scale prototype
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Mounting
Install 1” MgF2 windows