GLAST Italian meeting

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AGILE on-board BKG rejection

• 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

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DETECTOR DESCRIPTION

• Top Anticoincidence
• Lateral Anticoincidences
• SuperAGILE
• Silicon Tracker
• Mini-Calorimeter
• Mechanical structure
• (not shown in the figure)

54 cm
15 cm
22 cm
5 cm
40 cm
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Expected particle/albedo-photon background for an
Equatorial Orbit

• 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 Photons

• Thompson et al. 1981

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Event 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
Longo, Cocco Tavani (2002)
AGILE Satellite
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Trigger Levels

• 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

• Level-1
• Level-2

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L1 - TRIGGER
R trigger concept
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L1- TRIGGER
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Charge deposition
Optimal spatial resolution 40 ?m for a broad
range of incidence angles (0?-50?)
50 MeV gamma-ray, ? 50?
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Monte Carlo Simulations
Simulated background proton event
Simulated Gamma-Ray (E100 MeV, ?30º)
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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SUMMARY OF ON-BOARD BACKGROUND REJECTION

• 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

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Effective Area
Science with AGILE (2003)