AGILE on-board BKG rejection
description
Transcript of AGILE on-board BKG rejection
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GLAST Italian meetingFrancesco 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 AGILE on-board BKG rejectionrejection
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DETECTOR DESCRIPTIONDETECTOR DESCRIPTION
• Top AnticoincidenceTop Anticoincidence• Lateral AnticoincidencesLateral Anticoincidences• SuperAGILESuperAGILE • Silicon TrackerSilicon Tracker• Mini-CalorimeterMini-Calorimeter• Mechanical structure Mechanical structure (not shown in the figure)(not shown in the figure)
40 cm
5 cm
22 c
m15
cm
15 c
m
54 cm
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Expected particle/albedo-photon Expected particle/albedo-photon background for an Equatorial background for an Equatorial
OrbitOrbit
• Particle flux from SAS-2 and BeppoSAX data (~0.3 cm-2 s-1 for Ekin 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 (Ekin 7 GeV )
Albedo photons from the Earth (from SAS-2 data)
[Thompson et al. 1981]
Longo, Cocco & Tavani (2002)
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Albedo PhotonsAlbedo Photons
[Thompson et al. 1981]
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Event GenerationEvent Generation
• Particle/Albedo-photon Background
• Astrophysical point sources
Particle/photon tracks originating on a spherical surface
Montecarlo methods for the generation of the distribution functions
AGILE Payload
AGILE SatelliteLongo, Cocco & Tavani (2002)
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Trigger LevelsTrigger Levels
Level-1
Level-2
Hardware Implementation Information from Silicon Tracker and AC
panels Track topology at the ‘chip’ level
Software Implementation Analog Information on the released charge
in the Si-microstrips Track topology at the ‘cluster’ level 3D-reconstruction to reject albedo photons
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L1 - TRIGGERL1 - TRIGGER
R trigger concept
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L1- TRIGGERL1- TRIGGER
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Charge deposition Charge deposition
Optimal spatial resolution: ~40 mfor a broad range of incidence angles (0-50)
50 MeV gamma-ray, ~50
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Monte Carlo Simulations:
Simulated Gamma-Ray Simulated Gamma-Ray (E=100 MeV, (E=100 MeV, =30º)=30º)
Simulated background Simulated background proton event: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)
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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)
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• 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 SUMMARY OF ON-BOARD BACKGROUND REJECTIONBACKGROUND REJECTION
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Effective AreaEffective Area
Science with AGILE (2003)