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First Results from the First G-APD Cherenkov Telescope Adrian Biland, ETH Zurich for the FACT Collaboration: TU Dortmund, U Geneva, EPF Lausanne, U Wuerzburg.

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Presentation on theme: "First Results from the First G-APD Cherenkov Telescope Adrian Biland, ETH Zurich for the FACT Collaboration: TU Dortmund, U Geneva, EPF Lausanne, U Wuerzburg."— Presentation transcript:

1 First Results from the First G-APD Cherenkov Telescope Adrian Biland, ETH Zurich for the FACT Collaboration: TU Dortmund, U Geneva, EPF Lausanne, U Wuerzburg ETH Zurich Adrian Biland, ETH Zurich for the FACT Collaboration: TU Dortmund, U Geneva, EPF Lausanne, U Wuerzburg ETH Zurich

2 biland@phys.ethz.ch FACT ICRC 2011, Aug 17, Beijing 2 The FACT Project Key Question: can newly developed Si-based photosensors [G-APD, SiPM, MPPC,…] be used in Cherenkov Telescopes ? - reduction of operation complexity (less fragile, no HV) - stable remote operation - eventually lower cost and higher efficiency by profiting from development for large market for Si-based technology Main Problem: PMTs and G-APD have rather different features ==> 'difficult' to compare datasheets Solution: Build a CT using these new photosensors and try ==> First G-APD Cherenkov Telescope

3 biland@phys.ethz.ch FACT ICRC 2011, Aug 17, Beijing 3 Prototype Results (2009) two additional PMT in +/-7m distance DRS-2 with known cross-talk problems

4 biland@phys.ethz.ch FACT ICRC 2011, Aug 17, Beijing 4 Prototype Results (2009) Final proof that self-triggered measurements of Cherenkov- showers feasible with G-APD Next step: build real telescope

5 biland@phys.ethz.ch FACT ICRC 2011, Aug 17, Beijing 5 Refurbished HEGRA-CT3 Telescope at La Palma: - new mirrors installed (refurbished from CT1) - new drive system installed - new container as 'counting house' - awaiting camera …. Refurbished HEGRA-CT3 Telescope at La Palma: - new mirrors installed (refurbished from CT1) - new drive system installed - new container as 'counting house' - awaiting camera …. 9.2m 2 mirror area (next to MAGIC with 2x 236m 2 mirror…)

6 biland@phys.ethz.ch FACT ICRC 2011, Aug 17, Beijing 6 ~40cm ~40cm ~200kg ~200kg ~1kW ~1kW1440Pixels FACT Camera Tests at ETH Zurich integrated electronics

7 biland@phys.ethz.ch FACT ICRC 2011, Aug 17, Beijing 7 The FACT Project Poster T.Bretz 1132 Main Components: - Refurbished HEGRA CT3 telescope at LaPalma (9.2m 2 mirror area, f/d = 1.4, new drive system) Camera: - G-APDs (HAMAMATSU MPPC S10362-33-050C) - Solid Light-Concentrators Poster B. Huber 0136 - Electronics (DRS-4 based) in camera Talks P. Vogler 0389, T. Kraehenbuehl 0529 - readout using standard ethernet

8 biland@phys.ethz.ch FACT ICRC 2011, Aug 17, Beijing 8 G-APD Basics Geiger-mode Avalanche Photodiode: (also called: SiPM, MPPC, PPD, …) Pixelized Si-based photosensor: a (single) photon hiting a cell has some probability to create a 'breakdown' -> always same signal Many small cells ==> total signal analogue sum of the isochronous single-cell signals cell-sizes: 100x100 µm 2 better PDE 50x 50 µm 2 better NSB 3x3mm 2

9 biland@phys.ethz.ch FACT ICRC 2011, Aug 17, Beijing 9 Liouville theorem: can not shrink phase-space Area Angular Distribution ==> Solid cones allow higher area-concentration! (important for small photosensors with high cost/mm 2 ) Why Solid Light Concentrators FACT: ~80mm 2 9.0mm 2 (7.8mm 2 )

10 biland@phys.ethz.ch FACT ICRC 2011, Aug 17, Beijing 10 Why Solid Light Concentrators In case of sealed camera: less Fresnel reflection but: absorption ==> do not want too large G-APD area Can use inexpensive casting (UV transparent PMMA) Complicated shapes possible (FACT: square -> hexagon) needs 'perfect' optical coupling ==> glue

11 biland@phys.ethz.ch FACT ICRC 2011, Aug 17, Beijing 11 Solid Cone Problems Too high pressure during casting reduces overall transmission (also micro-bubbles) Tedious and time consuming glueing minor PMMA inpurities destroy UV transmission

12 biland@phys.ethz.ch FACT ICRC 2011, Aug 17, Beijing 12 FACT Status -Telescope: Ready -Camera: - Hardware: Ready (1435 Pixel ok, 2 dead, 3 strange) - Firmware: operational - Control Software: operational Tests of full camera going on …

13 biland@phys.ethz.ch FACT ICRC 2011, Aug 17, Beijing 13 Recent Test Results Random-Trigger ==> Dark Counts x 0.5ns

14 biland@phys.ethz.ch FACT ICRC 2011, Aug 17, Beijing 14 Recent Test Results Random-Trigger ==> Dark Counts 1 cell == 1 photo-electron (~10mV) x 0.5ns

15 biland@phys.ethz.ch FACT ICRC 2011, Aug 17, Beijing 15 Recent Test Results Random-Trigger ==> Dark Counts 1 cell == 1 photo-electron (~10mV) x 0.5ns 2 cells == 2 photo-electrons -> cross-talk

16 biland@phys.ethz.ch FACT ICRC 2011, Aug 17, Beijing 16 Recent Test Results very simple pulse extraction (not taking into account e.g. known pulse shape) ==> all pix. very similar ~5MHz dark counts <10% cross-talk 1 p.e. 2 p.e. 3 p.e. 4 p.e. Sum of 1435 Pixels without (ADC) calibration!! @ room temp.

17 biland@phys.ethz.ch FACT ICRC 2011, Aug 17, Beijing 17 Recent Test Results Illuminating camera with test-pulse: ==> All pix. very similar (without (ADC) calibration) Arrival-time distrib. <0.5ns (rms) !!! (without calibration !!!!)

18 biland@phys.ethz.ch FACT ICRC 2011, Aug 17, Beijing 18 Summary and Outlook -FACT camera assembled, first system tests look very promising -Will be installed in refurbished HEGRA-CT3 at La Palma this year -Gain experience with G-APDs under CT conditions

19 biland@phys.ethz.ch FACT ICRC 2011, Aug 17, Beijing 19 Summary and Outlook -FACT camera assembled, first system tests look very promising -Will be installed in refurbished HEGRA-CT3 at La Palma this year -Gain experience with G-APDs under CT conditions Will next generation G-APDs be better than PMTs (price, performance, …) ????


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