pmt absolute calibration using the rayleigh scattering in nitrogen air pmt absolute calibration...
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PMT absolute calibration PMT absolute calibration using the Rayleigh scattering using the Rayleigh scattering
in Nitrogen airin Nitrogen air S. Yoshida, Chiba UniversityS. Yoshida, Chiba University
MotivationMotivation
• Absolute calibration : Laser energy can be measured by energy
meter preciously.Rayleigh scattering is well understood.
Scattered Laser beam provides a well-calibrated
Single p.e. source!
ComponentsComponents
• Light source(Laser Science VSL-337ND-S)
N2 laser lambda = 337.1nmEmax=300uJPulse width<4nsec
• Si energy probe(Laser Probe RjP-465)
500fJ-250nJDetection area:1.0cm2
Accuracy=+-5%
• PMT(H7195PX)Size of photo cathode = 60mm phiHPK provides their calibration data. (Only 25 mm phi @center)( Both of the errors of HPK Q.E. and C.E. are 10%.)
Q.E. C.E.
Ch1 25.96% 74%
Ch2 25.78% 77%
Scattering regionScattering region
• Pure N2 gas (99.9995%) is introduced.
• Flow rate is 5 – 10 litter/minutes
• Temperature and pressure is monitored
by environmental data logger.
• 1 hour after of N2 flow start, calibration is
started.
Rayleigh scatteringRayleigh scattering
)cos1(16
3
)2(
)1(24 22224
223
kFnN
n
d
d
n : refractive index(1.0002936 for stp N2)λ : wavelength (337.1nm)Fk : Correction factor for anisotropy of non-spherical molecules(1.03679 for N2)
• For stp N2,
( H.Naus and W.Ubachs, Opt lett, 25 5 347 2000 )
)(cm108179.3 226 total
Calculation of # of photon in PMTCalculation of # of photon in PMT
• Npulse: # of photon in each laser pulse– When 1.0uJ, 1.697x1012photon
• Nmol : # density of molecule
• A : Acceptance of PMT (include dir. dependence)
• l: Length of scattering region
AlNNN moltotalpulsephoton
Polarization of laser beamPolarization of laser beam
The angle of polarizer is changed and then laser energy is measured.
Within +-5%
Laser energy cross checkLaser energy cross checkglasslaser Pyro (Accuracy = +-5% )
Si (Accuracy = +-5% )%.ΔE
REE
EE
Si
FresnelPyroSi
SiPyro
76
)nJ(525.6)calc(
)nJ(959.6),μJ(7.234
Calculation of # of photo-electron Calculation of # of photo-electron
• N0 : # of events below
threshold
• N : # of events above threshold
• μ: average of # of P.E.
Peak
Threshold=(1/3)xPeak
ADC distribution
n
i
i
all
all
iNN
NN
1
0
!
exp
exp
Absolute calibration of PMT1Absolute calibration of PMT1
# of photon from Si det.
Nphoton=0.50±0.03
# of P.E. from PMT.
Npe=0.093±0.01
Q.E.×C.E=0.18±0.02
(Data provided by HPK :Q.E.×C.E.=0.19±0.03)
Our Concept works out!!
New CRAY ChamberNew CRAY ChamberMonitoring N2
Scattering by
The calibrated tubes
Aperture Limiter
The IceCube PMT
•Photon beam with 50 mm diameter scans the cathode
Beam
PMT Box
Chamber
Calibration PMTs
N2 laser
Rotation Bed
Attachment for the IceCube PMAttachment for the IceCube PMTT
SummarySummary
• PMT absolute calibration method using Rayleigh scattering by pure gas has been developed.
• The measured Q.E.xC.E. is consistent with HPK result.
• A new chamber is now being designed and built.• Absolute calibration of the IceCube PMT is sche
duled to start in this coming February.• Watch out our report in the next collaboration me
eting.
Things to ConsiderThings to Consider
• The photon wavelength from N2 laser is 337 nm, which may be too short for the DOM pressure glass.
• On the other hand, we can MEASURE the DOM sphere absorption coefficient at 337 nm.
• The wavelength changeable laser is available but needs more $$.
Absolute calibration of PMT2Absolute calibration of PMT2
# of photon from Si det.
Nphoton=0.50 ±0.03
# of P.E. from PMT.
Npe=0.11±0.01
Q.E.×C.E=0.21±0.02
(Data provided by HPK:
Q.E.×C.E.=0.21±0.03)
Error estimation (very preliminary)Error estimation (very preliminary)
• Calibration of energy meter : ±5%• Polarization of beam : ±0.5%• Acceptance calculation : ±2%• Scattering calculation : ±3%• Reflection inside of box : ±2% ?• Geomagnetic field : ±5% ?• Reproducibility of 1 p.e. : ±10%
# of Photon
# of P.E.
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