The Minicalorimeter of the AGILE Satellite

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The Minicalorimeter of the AGILE Satellite

• C. Labantia, M. Marisaldia, F. Fuschinoa, M.
  Gallia, A. Arganb, A.Bulgarellia,
• F. Gianottia, M. Tavanib, M. Trifoglioa
• a IASF Bologna, via Gobetti 101, 40129 Bologna,
  Italy
• b IASF Roma, via Fosso del Cavaliere 100, 00133
  Roma, Italy
• Astrofisica gamma dallo spazio in Italia
• AGILE e GLAST
• Frascati July 2-3 2007

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Outline

• AGILE and its Minicalorimeter
• MCAL design and construction
• On-ground calibration and qualification tests
• Performance
• Preliminary in-flight results

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The AGILE Payload
SuperAGILE (SA) - IASF Roma silicon-strip
coded mask instrument 15 45 keV range
Anticoincidence Shield (AC) - IASF
Milano plastic scintillator PMT readout
Silicon Tracker (ST) - INFN Trieste tungsten /
silicon-strip detector 12 trays 30 MeV 50 GeV
range
MiniCALorimeter (MCAL) IASF Bologna and Thales
Alenia Space Italia, Milano CsI(Tl) scintillating
bars with PD readout
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MCAL Design
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MCAL Assembly
(during integration in Thales Alenia Space
Vimodrone, Italia)
top view
bottom view
upper plane detectors

• MCAL facts
• about 20 kg CsI(Tl)
• 1.5 radiation length on axis
• 60 readout channels, readout noise lt 1000 e- rms
• lt 6 W power consumption

acquisition board
preamplifier boards
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MCAL Bars Detectors

• 30 CsI(Tl) scintillating bars arranged in two
  orthogonal layers
• each bar is 375x23x15 mm with custom PIN PD
  glued at the bar's ends
• PD 256 mm2 active area, 130 pF capacitance, 1.5
  nA leakage current _at_ 20C (gtgt 950 e- rms noise)
• all bars wrapped with reflective coating and
  housed in a carbon fibre structure
• all bars characterized independently before
  integration

• collected signal well described by an
  exponential law
• U(x) EU0e-ax
• U0 signal output at PD
• a light attenuation coefficient
• E inciden energy, x incident position

a 0.028 0.002 cm-1
U0 21 1 e-/keV
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Energy and Position Reconstruction
g
x
PD-B
PD-A
0
UA signal output from PD A (ADC channels) UB
signal output from PD B (ADC channels) OA chain
A offset (channels) OB chain B offset
(channels) u0,A side A gain (channels/MeV)
u0,B side B gain (channels/MeV) aA side A
attenuation coefficient (cm-1) aB side B
attenuation coefficient (cm-1)
parameters derived from calibration
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Stand-alone Calibrations
source collimator
MCAL

• Performed on MCAL before payload integration
• About 400 measurements with a collimated 22Na
  source and an automatic tool for collimator motion

programmable positioning system
Exponential fit on points on each bar for
estraction of parameters aA, aB, u0,A, u0,B
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Operative Modes

• GRID mode MCAL slave to the Tracker. After a
  trigger, all bars above a threshold are acquired.
  Range 1 150 MeV
• Objective contribution to GRID events energy
  reconstruction.
• BURST mode MCAL works as an independent
  detector. After a dedicated logic has triggered a
  significant count rate increase, all MCAL data
  are saved in photon-by-photon mode. Range .3 -50
  MeV
• Objective GRB and intense transients high
  energy spectral coverage
• Scientific Ratemeters Self triggered events
  (Burst mode branch) fill two 11 bands energy
  spectra (one per detection plane) and sent to
  telemetry every second. Range .3 1000 MeV
• Objective gamma-ray background monitoring

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BURST ModeEnergy and Position Resolution
2.61 MeV 208Bi photopeak (232Th serie)
1.46 MeV 40K photopeak
10 MeV muon peak (single bar crossed)
DE/E 13 FWHM at 1.275 keV
20 MeV muon peak (whole MCAL crossed)
sx 1.8 cm at 1.275 keV
Background MCAL spectrum obtained in Tortona,
Italy, at Integrated Payload level
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GRID ModeEnergy and Position Resolution
Gain and energy calibration obtained by muons
Landau fit
3D Quick Look view
Position resolution obtained extrapolating the
muons tracks onto MCAL and computing the
deviation of MCAL position with extrapolated one
sx 0.7 cm at 11 MeV
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Burst Search Logic Test

• MCAL Burst Search logic
• 1ms, 16ms, 64ms, 256ms, 1.024s, 8.192s Search
  Integration Time (SIT)
• 4 spatial zones and 3 energy ranges (lt700 keV,
  700-1400 keV, gt1400 keV)
• static and dinamic thresholds for start and stop
  generation
• dedicated look-up tables to accept/reject
  triggers
• very flexible more than 2000 parameters for
  full configuration

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Burst Search Logic Test
MCAL Response to 1.9 s 22Na burst
HE Egt1.4 MeV
ME 0.7 lt E lt1.4 MeV
64 ms 256 ms 1.024 s 8.192 s
LE Elt0.7 MeV
Z9-Z15
X1-X8
X9-X15
Z1-Z8
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Burst Search Logic Test
MCAL bars X9-X15, low energy, response to a 400
ms 22Na burst. Trigger on the 256 ms SIT
Bkg 10 s threshold
Estimated background
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Burst Search Logic Test
Solar panel side
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Background Measurements on Earth...
Background count spectra measured by MCAL in four
different locations Tortona (Italy), Munchen
(Germany), SHAR (India) in the clean room, SHAR
(India) after integration on launcher. The blue
curve is the last MCAL spectrum taken on Earth...
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Background Measurements in Space!
AGILE and MCAL in Commissioning
PRELIMINARY!
Scientific Ratemeters count spectra for both MCAL
planes with and without Anticoincidence. Obtained
values are quite in good agreement with
simulations (in progress)
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The First g-transient seen by AGILE!
AGILE (MCAL, SA and AC) detection of a probable
GRB on June 22 07, 225 UTC
PRELIMINARY!
From IBAS SPI ACS website
MCAL scientific ratemeters light curves
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The First g-transient seen by AGILE!
AGILE MCAL detection of a probable GRB on June 22
07, 225 UTC
PRELIMINARY!
Time in sec x 106
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The First g-transient seen by AGILE!
AGILE MCAL detection of a probable GRB on June 22
07, 225 UTC
PRELIMINARY
PRELIMINARY!
First 5 sec of GRB count spectra X plane