First Results from the First G-APD Cherenkov Telescope

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 biland@phys. ethz. ch FACT ICRC 2011, Aug 17, Beijing

The FACT Project Key Question: can newly developed Si-based photosensors [G-APD, Si. PM, 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 biland@phys. ethz. ch FACT ICRC 2011, Aug 17, Beijing 2

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

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

Refurbished HEGRA-CT 3 Telescope at La Palma: - new mirrors installed (refurbished from CT 1) - new drive system installed - new container as 'counting house' - awaiting camera …. FACT 9. 2 m 2 biland@phys. ethz. ch (next to MAGIC ICRC 2011, 236 m 2 Beijing mirror area with 2 x Aug 17, mirror…) 5

FACT Camera Tests at ETH Zurich integrated ~40 cm ~200 kg ~1 k. W 1440 Pixels biland@phys. ethz. ch FACT electronics ICRC 2011, Aug 17, Beijing 6

The FACT Project Poster T. Bretz 1132 Main Components: - Refurbished HEGRA CT 3 telescope at La. Palma (9. 2 m 2 mirror area, f/d = 1. 4, new drive system) Camera: - G-APDs (HAMAMATSU MPPC S 10362 -33 -050 C) - Solid Light-Concentrators Poster B. Huber 0136 - Electronics (DRS-4 based) in camera Talks P. Vogler 0389, T. Kraehenbuehl 0529 - readout using standard ethernet biland@phys. ethz. ch FACT ICRC 2011, Aug 17, Beijing 7

G-APD Basics Geiger-mode Avalanche Photodiode: (also called: Si. PM, 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: 100 x 100 µm 2 better PDE 50 x 50 µm 2 better NSB biland@phys. ethz. ch FACT ICRC 2011, Aug 17, Beijing 8 3 x 3 mm 2

Why Solid Light Concentrators Liouville theorem: can not shrink phase-space Area <----> Angular Distribution FACT: ~80 mm 2 9. 0 mm 2 (7. 8 mm 2) ==> Solid cones allow higher area-concentration! (important for small photosensors with high cost/mm 2) biland@phys. ethz. ch FACT ICRC 2011, Aug 17, Beijing 9

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

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 biland@phys. ethz. ch FACT ICRC 2011, Aug 17, Beijing 11

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

Recent Test Results Random-Trigger ==> Dark Counts biland@phys. ethz. ch FACT ICRC 2011, Aug 17, Beijing x 0. 5 ns 13

Recent Test Results Random-Trigger ==> Dark Counts 1 cell == 1 photo-electron (~10 m. V) biland@phys. ethz. ch FACT ICRC 2011, Aug 17, Beijing x 0. 5 ns 14

Recent Test Results Random-Trigger ==> Dark Counts 2 cells == 2 photo-electrons -> cross-talk 1 cell == 1 photo-electron (~10 m. V) biland@phys. ethz. ch FACT ICRC 2011, Aug 17, Beijing x 0. 5 ns 15

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

Recent Test Results Illuminating camera with test-pulse: ==> All pix. very similar (without (ADC) calibration) Arrival-time distrib. <0. 5 ns (rms) !!! (without calibration !!!!) biland@phys. ethz. ch FACT ICRC 2011, Aug 17, Beijing 17

Summary and Outlook - FACT camera assembled, first system tests look very promising - Will be installed in refurbished HEGRA-CT 3 at La Palma this year - Gain experience with G-APDs under CT conditions 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-CT 3 at La Palma this year - Gain experience with G-APDs under CT conditions Will next generation G-APDs be better than PMTs (price, performance, …) ? ? biland@phys. ethz. ch FACT ICRC 2011, Aug 17, Beijing 19