pogolitemc_2007-01-30.ppt 1 updated mc study of pogolite trigger rate/bg january 30, 2007...

PoGOLiteMC_2007-01-30.ppt

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Updated MC Study of PoGOLite Trigger Rate/BG

January 30, 2007Tsunefumi Mizuno (Hiroshima Univ.)

[email protected]

mailto:[email protected]


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Objective of This MemoObjective of This Memo

• Trigger rate is crucial for DAQ design (data size, speed of data transfer, etc.). So does the residual background for performance evaluation and observation planning.•The expected trigger rates and residual background are studied here by MC with the latest detector geometry and cosmic-ray flux model. This memo is intended to be used for future reference.


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GeometryGeometry

Segmented side BGOs with Al housing and dual layer collimator

•DimensionsantiThickness = 3 cmbottomWidth = 2.85 cmfastWidth/slowWidth = 2.775/2.770 cmAl Case for side BGO, antiGap = 0.075 cmAl Case for bottom BGO, bottomGap = 0.15 cmNo passive shield

antiThicknessbottomWidth

bottomGap

antiGap

SAS in Al Case

Slow scintillator and collimator

Pb 50um(55cm)Sn 50um(60cm)

Pb/Sn dual layer collimator


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CR model: charged particlesCR model: charged particles

e-/e+

protons

-/+

•Cosmic-ray BG flux model for GLAST BFEM (Palestine, Texas). See Mizuno et al 2004 (ApJ 614, 1113) for more detail.


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CR model: gammasCR model: gammas

CXBAtmospheric downward

Atmospheric upward


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Summary of CR spectra (above 10 MeV)Summary of CR spectra (above 10 MeV)

e-/e+

protons

-/+

CXB

Atmospheric downward

Atmospheric upward


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Section1: Trigger RateSection1: Trigger Rate


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Anti Trigger RateAnti Trigger Rate

protone-/e+gamma

CXB

Atmospheric downward

Atmospheric upward

total

•Rate of events where any one of 54 units have a hit •Rate of each unite


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Bottom Trigger RateBottom Trigger Rate



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Fast Scintillator Trigger RateFast Scintillator Trigger Rate



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Slow Scintillator Trigger RateSlow Scintillator Trigger Rate



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Section2: BackgroundSection2: Background


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Simulation ConditionSimulation Condition

•Source Spectra•E-2.1 spectrum with 100mCrab intensity, 20-200keV (300.8 c/s/m2)•100% polarized, 6h exposure .Attenuation by air of 4g/cm2

•Detector Response (veto scintillators)•Reject events with hit in slow/anti/btm scintillators. Eth=30 keV. No energy smearing taken into account yet.

•Detector Response (fast scintillator)•0.5 photo-electron/keV. Eth=2 keV•fluctuated by poisson distribution, smeared by gaussian of sigma=0.5 keV (PMT energy resolution)

•Event Selection•Two or three fast scintillators detected a hit.•The largest energy deposit is considered to be photo absorption and the second largest energy deposit to be Compton scattering. (ignore the smallest energy deposit in 3 hits events.)•Smear azimuth angle distribution with Hiro’s resolution function.•No event selection on Compton kinematics


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Source and Expected BG SpectraSource and Expected BG Spectra

100 mCrab

BG (total)

CXB/downward/upward

•Signal exceed the BG up to 80 keV for 100 mCrab source and up to 140 keV for Crab Nebula.

20 keV

1 Crab


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Dependence on Bottom BGO/Slow Scintillator Dependence on Bottom BGO/Slow Scintillator Threshold (1)Threshold (1)

• Threshold of 30 keV is good enough to reduce the BG down to minimum level.

100 mCrab1 Crab

btmTh/slowTh =10keV, 30keV, 100keV, 300keV and 1MeV


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Dependence on Bottom BGO/Slow Scintillator Dependence on Bottom BGO/Slow Scintillator Threshold (2)Threshold (2)

• Threshold of 10 keV(bottom BGO)/30 keV (slow scinti.) is good enough to reduce the BG down to minimum level. Threshold of 33 keV/100 keV is acceptable.

100 mCrab1 Crab

btmTh/slowTh =3.3/10keV, 10/30keV, 33/100keV, 100/300keV

and 0.33/1MeV


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Appendix: Standard Process vs. Low Energy Appendix: Standard Process vs. Low Energy ExtentionExtention

• No significant difference between simulations with low energy extention and standard process. Fluorescent X-rays from Pb are well suppressed by Sn foil.

100 mCrab1 Crab

BG (total) with Low Energy Extention/Standard Process

pogolitemc_2007-01-30.ppt 1 updated mc study of pogolite trigger rate/bg january 30, 2007...

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