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The Minicalorimeter of the AGILE Satellite

C. Labanti a , M. Marisaldi a , F. Fuschino a , M. Galli a , A. Argan b , A.Bulgarelli a , F. Gianotti a , M. Tavani b , M. Trifoglio a 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

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The Minicalorimeter of the AGILE Satellite

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  1. 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 eGLAST Frascati – July 2-3 2007 The Minicalorimeter of the AGILE Satellite

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

  3. 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

  4. MCAL Design

  5. 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 < 1000 e- rms • < 6 W power consumption acquisition board preamplifier boards

  6. 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 @ 20°C (>> 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

  7. 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

  8. 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

  9. 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

  10. BURST Mode:Energy 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

  11. GRID Mode:Energy 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

  12. BURST SIMULATOR 45 cm SOLAR PANELS AC-4 G1 (X9-X15) G3 (Z9-Z15) G2 (Z1-Z8) AC-1 AC-3 G0 (X1-X8) AC-2 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 (<700 keV, 700-1400 keV, >1400 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

  13. Burst Search Logic Test MCAL Response to 1.9 s 22Na burst HE E>1.4 MeV ME 0.7 < E <1.4 MeV 64 ms 256 ms 1.024 s 8.192 s LE E<0.7 MeV Z9-Z15 Z1-Z8 X1-X8 X9-X15

  14. 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

  15. Burst Search Logic Test Solar panel side

  16. 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...

  17. 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)

  18. The First g-transient seen by AGILE! AGILE (MCAL, SA and AC) detection of a probable GRB on June 22 ’07, 2:25 UTC PRELIMINARY! From IBAS SPI ACS website MCAL scientific ratemeters light curves

  19. The First g-transient seen by AGILE! AGILE MCAL detection of a probable GRB on June 22 ’07, 2:25 UTC PRELIMINARY! Time in sec x 106

  20. The First g-transient seen by AGILE! AGILE MCAL detection of a probable GRB on June 22 ’07, 2:25 UTC PRELIMINARY PRELIMINARY! First 5 sec of GRB count spectra X plane

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