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FACT First GAPD Cherenkov Telescope

FACT First GAPD Cherenkov Telescope. LHC Days in Split 4-9 October 2010, Split, Croatia W. Lustermann, ETH Zurich on behalf of the FACT collaboration. Detection of Air Cherenkov Showers. Signal amplitude: 200 photons / m 2 (1 TeV γ -ray) Spectrum: (300 – 600) nm

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FACT First GAPD Cherenkov Telescope

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  1. FACT First GAPD Cherenkov Telescope LHC Days in Split 4-9 October 2010, Split, Croatia W. Lustermann, ETH Zurich on behalf of the FACT collaboration

  2. Detection of Air Cherenkov Showers Signal amplitude: 200 photons / m2 (1 TeVγ-ray) Spectrum: (300 – 600) nm Duration: few ns Night sky: up to several GHz Optical imaging system (causes losses) Mirror  light concentrators  photo-detectors Cherenkov spectrum 2.2 km altitude Cut off ~320 nm

  3. FACT Project Former HEGRA CT3 telescope La Palma, Canary Islands

  4. Mirrors

  5. Light Concentrator (Winston Cones) Height: 19.939 mm IN: Hexagon: 9.5 mm OUT: Square: 2.8 mm Concentration: 7.48 Solid cones  use total internal reflection simulation • ideal cone • realistic cone Thanks for the support of University of Zurich. Data sheet of raw material for injection molding: Cut off ~320 nm

  6. Light Concentrator (Winston Cones) Distribution of exit angles Important for photo-detectors simulation • ideal cone • realistic cone Output light distribution (simulation) IMOS using ZEMAX ray tracing program Output light distribution (simulation FACT)  We can trust our simulation

  7. Photo Detectors (G-APDs)

  8. Photo Detection (Cone + GAPD) Observed spectrum based on simulation, measured Cherenkov light spectrum, G-APD and cone properties HeNe laser light injection image measured Input Cherenkov spectrum folded with G-APD acceptance • ideal cone • realistic cone efficiency • 80.7 % • 75.6 %

  9. Camera Mechanics

  10. FACT Camera and Telescope

  11. Camera Mechanics Window Mount to telescope Shutter Crates The construction must be water tight (following IP67) specifications: This concerns the housing as well as connectors on the patch panel Ethernet switches Connectors Sensor compartment

  12. Sensor Compartment Details G-APDs with Winston cones 2 x GAPD bias Front baffle plate Cable adapters /bias feed 9 G-APDs trigger patch Co-axial signal cables, 50 ohm, ~35 cm

  13. Electronics Systems Overview 2 GHz FLV: low voltage conversion FSC slow control (Temp., rel Humidity, voltages) FLP light pulser FDC drive calibration

  14. Single Photon Spectrum

  15. FACT DAQ – LED pulses 2 GHz 500 ns Pre-amplifier board (FPA) and analog pipeline (DRS4) & digitization board (FAD) connected via the mid plane (FMP) distributing power and slow control signals LED flashes registered by an MPPC connected to the FACT readout system

  16. Trigger system & HV Feedback • Trigger unit (FTU) – 40 pieces • Uses 4 sums of 9 pixels for a majority decision • Mezzanine card on the FPA • Trigger master (FTM) – 1 piece • Provides trigger decision upon 40 FTU inputs • Provides CLOCK, TRIGGER and RESET signals Measured light pulse response Feedback OFF Feedback ON • 32 channel GAPD bias card • Computer controlled (USB) • Counting hut • Active bias supply feedback • Light pulses of 9 LEDs (FLP) are triggered by the FTM and read out • Deviations from nominal values are converted into GAPD bias corrections and applied.

  17. GAPD bias supply system • HV crate: 320 channels • 1 crate controller with USB interface • 10 HV mother boards • power conversion /distribution and control bus wired in the back of the crate • Single channel board • HV operational amplifier OPA454 • controlled by a 12 bit serial DAC (DA8034U) • output voltage adjustable (0 – 90) V • calibration using trim potentiometer • voltage set precision 22 mV • High side current monitor (HV7800) • Over current protection, limit (1-5)mA 32 channel HV mother boards

  18. First Measurements Nightof 2.-3. June on theroofof ETH physicsbuilding PA48 SP16 CP144

  19. Event 21 Run 201 • 25mV singlepixelthreshold (4 p.e.) • Majority 4 out of 16 • 100 kHz trigger rate per pixel • 0.1 Hz total rate • 2 GHz sampl. freq. Horizontal: 0 ... 512 ns, Vertical: -50 ... 850mV

  20. Summary / Outlook

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