1. GLAST Simulations Theodore E. Hierath Louisiana State University August 20, 2001

2. Topics What is GLAST? The Orbital Radiation Environment Why simulate everything? Test Program - Root Plot Adding New Particle Sources Scientific Goals

3. About GLAST Launch Date: 2006 Instruments –Large Area Telescope 2.5 steradian FOV 0.5 arc minute resolution 20 MeV – 300 GeV Sensitivity: 1.6 x 10 -9 photons cm -2 s -1 (at energies > 100 MeV) –Gamma-ray Burst Monitor

4. The Large Area Telescope Modular 4x4 Array of Towers Silicon Strip Trackers –Measures direction of incidence CsI Calorimeters –Measures particle energies Segmented Anticoincidence Detector –Segmentation reduces self-veto problem at higher energies

6. The Cosmic Ray Spectrum Flux particles/(m 2 sr s GeV) Kinetic Energy (eV) GLAST

7. Why simulate everything? To determine the expected rate of events –The average downlink frequency is ~50 Hz –The average event rate is ~4 kHz To find out what would happen if… To know what to look for –The incoming gamma ray flux is ~O(10,000) times less than the cosmic ray flux proton gamma ray

8. Root Plot Test Program Interfaces with Simulation and ROOT Multiple graphing modes Orbit Averaging Capabilities

9. Root Plot Graphs

10. Effects of Solar Modulation

11. FILE Spectrum Allows new spectra to be specified using files created by Root Plot Sources specified in XML File format is df/dE vs. E

12. New Orbit-avg Fluxes Integrates to ~4.2 kHz/m 2

13. Scientific Goals Active Galactic Nuclei Origin of the Diffuse Gamma-ray Background Origin of Cosmic Rays Endpoints of Stellar Evolution Unidentified Gamma-ray Sources Dark Matter Solar Physics Gamma-Ray Bursts

14. Thanks to Toby Burnett Sean Robinson The University of Washington The National Science Foundation NASA