The AGILE Gamma Ray Imaging Detector (GRID): a novel ...

The AGILE Gamma Ray Imaging Detector (GRID): a novel application
of silicon tracker for astrophysics high energy photons detection
Andrea Rappoldi – INFN Pavia (on behalf of AGILE collaboration)
AGILE is a space mission of ASI (Italian Space Agency) which goal is to detect astrophysics
photons in the energy ranges of 18 ÷ 60 keV and 30 MeV ÷ 50 GeV with imaging capability
The space environment requires:
• Lightness
• Compactness
• Low power consumption
• Operation in hostile environment
To detect γ-rays a silicon telescope is used.
The γ-ray produces an e + e - pair
The precise reconstruction (12 planes with 40 μm
resolution) of the e + e - tracks allows to determine
the γ direction and energy with great accuracy
Field Of View (FOV) ~ 120°
Point Spread Function (PSF) ~ 2.5° @ 500 MeV
These goals are achieved using silicon detectors

GRID calibration (on ground)
To calibrate GRID, a tagged photon beam was used.
It was realised at Frascati INFN Laboratory, Beam Test Facility (BTF)
The BTF beam electrons interact with an
active Si target, and loose energy producing
bremsstrahlung photons
The reduced momentum electrons are bended
more than the BTF beam and impact on the
Si tagging detector
The impact position depends on the electron
momentum, and allows to determine the γ energy
The GRID calibration at BTF allowed to obtain
a precise determination of PSF as a function
of photon direction (θ, φ) and energy
γ
Si tagging detector
Si target
e -