GLAST Rate Calculations Toby Burnett 12 Jan 00

12 Jan 2000T. Burnett GLAST rate calculations2 Components used to measure rates Source model –Geomagnetic latitude –Spectrum –zenith angle Instrument geometry Detector response –ACD, tracker, CAL Trigger model

12 Jan 2000T. Burnett GLAST rate calculations3 How it is done: overview The Target sphere: 6 m 2 cross section, (24 m 2 surface area) R=1.38 m. GLAST: active box dimen x 1.69 x 0.90 Spacecraft: 1000 kg Al hexagon Solar panels: not included Incoming particle, choose: Flux (if multiple) E  intersection with disk zenith  horizon: 24 0 below horizontal cos 

12 Jan 2000T. Burnett GLAST rate calculations4 A flux example: “muons” Entry in the file source_library.xml : Rate: (100 s -1 m -2 sr -1 )x(6 m -2 )x (1.4x 2  sr) = 5278 Hz Rate intercepting top surface: F A  x (1.76) 2 x  Hz (or 18%, also as measured)

12 Jan 2000T. Burnett GLAST rate calculations5 The background sources The backgndmix source: composite name Standard proton spectrum Albedo from horizon Electron Protons below cutoff

12 Jan 2000T. Burnett GLAST rate calculations6 Previous Results The trigger: no ACDACD L15.47 kHz (9.06) 2.08 kHz (3.39) L21.86 kHz (3.13) 0.96 kHz (1.72)

12 Jan 2000T. Burnett GLAST rate calculations7 Future needs Good model for proton albedo based on AMS Implement heavy component –flux –interactions