1. 1 GLAST Italian meeting Francesco Longo & Carlotta Pittori Udine 11 marzo 2004 V. Cocco, A.Giuliani, P.Lipari, A. Pellizzoni, M.Prest, M.Tavani. E.Vallazza AGILE on-board BKG rejection

2. 2 DETECTOR DESCRIPTION Top AnticoincidenceTop Anticoincidence Lateral AnticoincidencesLateral Anticoincidences SuperAGILESuperAGILE Silicon TrackerSilicon Tracker Mini-CalorimeterMini-Calorimeter Mechanical structureMechanical structure (not shown in the figure) (not shown in the figure) 40 cm 5 cm 22 cm 15 cm 54 cm

3. 3 Expected particle/albedo-photon background for an Equatorial Orbit Particle flux from SAS-2 and BeppoSAX data (~0.3 cm -2 s -1 for E kin  1 MeV ) 3 main components: e +, e -, p Spectral data from AMS and Marya Assumptions: 1) isotropic distribution for e +, e -, and low energy protons 2) sky-incidence for high energy p (E kin  7 GeV ) lAlbedo photons from the Earth (from SAS-2 data) [Thompson et al. 1981] Longo, Cocco & Tavani (2002)

4. 4 Albedo Photons [Thompson et al. 1981]

5. 5 Event Generation Particle/Albedo-photon Background Astrophysical point sources lParticle/photon tracks originating on a spherical surface lMontecarlo methods for the generation of the distribution functions AGILE Payload AGILE Satellite Longo, Cocco & Tavani (2002)

6. 6 Trigger Levels Level-1 Level-2 Hardware Implementation Information from Silicon Tracker and AC panels Track topology at the ‘chip’ level n Software Implementation n Analog Information on the released charge in the Si-microstrips n Track topology at the ‘cluster’ level n 3D-reconstruction to reject albedo photons

7. 7 L1 - TRIGGER R trigger concept

8. 8 L1- TRIGGER

9. 9 Charge deposition Optimal spatial resolution: ~40  m for a broad range of incidence angles (0  -50  ) 50 MeV gamma-ray, ~50 

10. 10 Monte Carlo Simulations: Simulated Gamma-Ray (E=100 MeV,  =30 º ) Simulated background proton event: It can be rejected by the on-board trigger because of the crucial use of the analog signal from the Si-microstrips providing information on cluster charges.  direction from 3-D AGILE REconstruction Method (AREM) integrated with Kalman filter algorithms (Pittori-Tavani NIM 2002)

11. 11 On-board GRID Background Rejection: Particle background rates : - e+/e-: reduced by a factor ~ 100 - Protons: reduced by a factor ~ 1000 - Earth albedo  -ray flux : reduced by a factor ~ 30 The GRID on-board background rejection is quite efficient, reducing the total charged-particle rate from ~ 2000 Hz to ~ 20 Hz. Cocco, Longo & Tavani (2002)

12. 12 Expected total rate of particle/albedo-photon entering into the Tracker volume 2-3 KHz Level-1Trigger cut  100 Hz Level-2 processing cut 20-30 Hz On-board Background Rejection : ~10 -2 SUMMARY OF ON-BOARD BACKGROUND REJECTION

13. 13 Effective Area Science with AGILE (2003)