1 / 13

Study of PoGO background dependence on the collimator material/slow scintillator threshold

This study explores the influence of collimator material and slow scintillator threshold on the background of PoGO. Simulations were conducted using Geant4 ver5.1 to analyze the expected background levels for different gamma energies.

stommie
Download Presentation

Study of PoGO background dependence on the collimator material/slow scintillator threshold

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Study of PoGO background dependence on the collimator material/slow scintillator threshold April 21, 2004 Tsunefumi Mizuno mizuno@SLAC.Stanford.EDU History of changes; updated on April 15, 2004 modified on April 21, 2004 PoGO_collimator_2004-04-21.ppt

  2. Simulated Geometry • Thickness of fast scint. = 2.63cm • (D = 2.23cm) • W (thickness of slow scint.) = 0.2cm • L1 (slow scint. length) = 60cm • L2 (fast scint. length) = 20cm • Thickness of W collimator = 25um • Thickness of Sn collimator = 100um • Thickness of btm BGO = 2.68cm • Length of btm BGO = 3cm • (not tapered in simulator for simplicity) • Gap between BGOs = 0.5cm • (including BaSo4 eflector) • Thickness of side Anti BGO = 3cm • Length of side Anti BGO = 60cm • # of units = 217 (geometrical area of fast scint. not covered by slow scint. = 934.4 cm2) PoGO_collimator_2004-04-21.ppt

  3. Simulation Condition • The same Crab spectrum as that used in Hiro’s EGS4 simulation was simulated here. That is, • E-2.1 spectrum with 100mCrab intensity, 20-200keV (300.8 c/s/m2) • 100% polarized, 6h exposure • Attenuation by air of 4g/cm2 (atmospheric depth in zenith direction is ~3g/cm2 and that in line-of-sight direction is 4g/cm2) • Atmospheric downward/upward gamma spectra for GLAST BFEM simulation were used as background. • Use Geant4 ver5.1. Possible minor bug of polarization vector after Compton scattering was fixed by user (found by Y. Fukazawa @ Hiroshima Univ.). PoGO_collimator_2004-04-21.ppt

  4. Detector Resopnses • The same detector responses as those used in Hiro’s EGS4 simulation • If there is a hit in slow/anti/btm scintillators, event is rejected. (Threshold is 3 keV for anti/btm BGO and 10, 30, 100, 300, and 1000 keV for slow scintillator. Note that the position dependence has not taken into account yet.). Energy smearing and poisson fluctuation are not taken into account yet for veto scintillators. • Assumed detector resposes: • 0.5 photo-electron/keV • fluctuated by poisson distribution • smeared by gaussian of sigma=0.5 keV (PMT energy resolution) • minimum hit threshold after three steps above is 3 keV PoGO_collimator_2004-04-21.ppt

  5. Event Analysis • The same as those of Hiro’s EGS4 Simulation • Use events in which two or three fast scintillators detected a hit. • The largest energy deposit is considered to be photo absorption • The second largest energy deposit is considered to be Compton scattering. • Smallest energy deposit (in case of three scintillators with hit) is ignored. • Smear azimuth angle distribution with Hiro’s resolution function. • No event selection on compton kinematics PoGO_collimator_2004-04-21.ppt

  6. Expected Background (1) atmospheric downward gamma, W collimator of 25um 100mCrab (incident) 100mCrab (detected) Flux(c/s/cm2/keV) Background due to atmospheric gamma Eth=10keV, 30keV, 100keV,300keV and 1MeV 20 100 gamma energy (keV) If we can reduce the slow scint. threshold below 100 keV, PoGO will have sensitivity up to ~90 keV. PoGO_collimator_2004-04-21.ppt

  7. Expected Background (2) atmospheric downward gamma, Sn collimator of 100um 100mCrab (incident) 100mCrab (detected) Flux(c/s/cm2/keV) Background due to atmospheric gamma Eth=10keV, 30keV, 100keV,300keV and 1MeV 20 100 gamma energy (keV) BG level of Sn 100 um due to atmospheric downward gamma is ~1.5 x (BG level of W 25um; see page 6.). PoGO will have sensitivity up to ~80 keV for slow scint. treshold of 100 keV. PoGO_collimator_2004-04-21.ppt

  8. Expected Background (3) atmospheric upward gamma, W collimator of 25um 100mCrab (incident) 100mCrab (detected) Flux(c/s/cm2/keV) Background due to atmospheric gamma Eth=10keV, 30keV, 100keV,300keV and 1MeV 20 100 gamma energy (keV) If we can reduce the slow scint. threshold below 100 keV, PoGO will have sensitivity up to ~90 keV. PoGO_collimator_2004-04-21.ppt

  9. Expected Background (4) atmospheric upward gamma, Sn collimator of 100um 100mCrab (incident) 100mCrab (detected) Flux(c/s/cm2/keV) Background due to atmospheric gamma Eth=10keV, 30keV, 100keV,300keV and 1MeV 20 100 gamma energy (keV) BG level of Sn 100 um due to atmospheric downward gamma is ~1.5 x (BG level of W 25um; see page 8.). PoGO will have sensitivity up to ~80 keV for slow scint. treshold of 100 keV. PoGO_collimator_2004-04-21.ppt

  10. Expected Background (5) atmospheric downward gamma, W collimator of 25um, lowE process 100mCrab (incident) 100mCrab (detected) Flux(c/s/cm2/keV) Background due to atmospheric gamma Eth=10keV, 30keV, 100keV,300keV and 1MeV 20 100 gamma energy (keV) If we take into account the fluorescent X-rays, BG level below 100 keV increases by a factor of ~2 (see page 6). PoGO_collimator_2004-04-21.ppt

  11. Expected Background (6) atmospheric downward gamma, Sn collimator of 100um, lowE process 100mCrab (incident) 100mCrab (detected) Flux(c/s/cm2/keV) Background due to atmospheric gamma Eth=10keV, 30keV, 100keV,300keV and 1MeV 20 100 gamma energy (keV) Even if we take into account the fluorescent X-rays, BG level below 100 keV does not change very much (see page 7). PoGO_collimator_2004-04-21.ppt

  12. Expected Background (7) atmospheric upward gamma, W collimator of 25um, lowE process 100mCrab (incident) 100mCrab (detected) Flux(c/s/cm2/keV) Background due to atmospheric gamma Eth=10keV, 30keV, 100keV,300keV and 1MeV 20 100 gamma energy (keV) If we take into account the fluorescent X-rays, BG level below 100 keV increases by a factor of ~2 (see page 8). PoGO_collimator_2004-04-21.ppt

  13. Expected Background (8) atmospheric upward gamma, Sn collimator of 100um, lowE process 100mCrab (incident) 100mCrab (detected) Flux(c/s/cm2/keV) Background due to atmospheric gamma Eth=10keV, 30keV, 100keV,300keV and 1MeV 20 100 gamma energy (keV) If we take into account the fluorescent X-rays, BG level below 30 keV increases by a factor of 2. BG level in 30-100 keV does not change very much (see page 8). PoGO_collimator_2004-04-21.ppt

More Related