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PMT absolute calibration using the Rayleigh scattering in Nitrogen air

PMT absolute calibration using the Rayleigh scattering in Nitrogen air. ICRR N.Sakurai , M.Fukushima Utah University L.Wiencke. Motivation. Absolute calibration 　：　 Laser energy can be measured by energy meter preciously. Rayleigh scattering is well understood.

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PMT absolute calibration using the Rayleigh scattering in Nitrogen air

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  1. PMT absolute calibration using the Rayleigh scattering in Nitrogen air ICRR N.Sakurai, M.Fukushima Utah University L.Wiencke

  2. Motivation • Absolute calibration　：　 Laser energy can be measured by energy meter preciously. Rayleigh scattering is well understood. So, we can obtain the precious number of scattering photons by Rayleigh scattering and it can be used for PMT Q.E.xC.E. calibration.

  3. Absolute calibration using N2 laser (CRAY)

  4. System overview

  5. Components • Light source (Laser Science VSL-337ND-S) N2 laser lambda＝337.1nm Emax=300uJ Pulse width<4nsec • Si energy probe (Laser Probe RjP-465) 500fJ-250nJ Detection area:1.0cm2 Accuracy=+-5%

  6. PMT(H7195PX) Size of photo cathode＝60mm phi HPK provides their calibration data. (Only 25ｍｍ phi @center) （Both of the errors of HPK Q.E. and C.E. are 10%.)

  7. Scattering 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.

  8. Rayleigh scattering 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) （H.Naus and W.Ubachs, Opt lett, 25 5 347 2000） For stp N2,

  9. Calculation 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

  10. Polarization of laser beam The angle of polarizer is changed and then laser energy is measured. Within +-5%

  11. Laser energy cross check Pyro (Accuracy = +-5% ) laser glass Si (Accuracy = +-5% )

  12. ADC distribution Threshold=(1/3)xPeak Peak Calculation of # of photo-electron • N0 : # of events below threshold • N : # of events above threshold • μ: average of # of P.E.

  13. Absolute 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)

  14. Absolute 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)

  15. 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.

  16. Summary • PMT absolute calibration method using Rayleigh scattering by pure gas is developing. (obtained almost same result as HPK) • Energy of laser is measured by two calibrated energy probes (Pyro-electric and Si), and two are consistent with 7%. • The measured Q.E.xC.E. is consistent with HPK result. • This system will be useful to measure Air fluorescence yield by well calibrated PMT. (Difference is only electron or photon.)

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