Download G-APD camera: FACT

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
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
[email protected]
FACT
ICRC 2011, Aug 17, Beijing
2
Prototype Results (2009)
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FACT
ICRC 2011, Aug 17, Beijing
DRS-2 with known cross-talk problems
two additional PMT in +/-7m distance
3
Prototype Results (2009)
Final proof that self-triggered
measurements of Cherenkovshowers feasible with G-APD
Next step: build real telescope
[email protected]
FACT
ICRC 2011, Aug 17, Beijing
4
Refurbished HEGRA-CT3 Telescope at La Palma:
- new mirrors installed (refurbished from CT1)
- new drive system installed
- new container as 'counting house'
- awaiting camera ….
Aug 17,2Beijing
9.2m2 [email protected]
mirror area (next toFACT
MAGIC ICRC
with2011,
2x 236m
mirror…)
5
FACT Camera
Tests at ETH Zurich
integrated
~40cm
~200kg
~1kW
1440Pixels
[email protected]
FACT
electronics
ICRC 2011, Aug 17, Beijing
6
The FACT Project
Poster T.Bretz 1132
Main Components:
- Refurbished HEGRA CT3 telescope at LaPalma
(9.2m2 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
[email protected]
FACT
ICRC 2011, Aug 17, Beijing
7
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 µm2 better PDE
50x 50 µm2 better NSB
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FACT
ICRC 2011, Aug 17, Beijing
3x3mm8 2
Why Solid Light Concentrators
Liouville theorem: can not shrink phase-space
Area <----> Angular Distribution
FACT:
~80mm2
9.0mm2
(7.8mm2)
==> Solid cones allow higher area-concentration!
(important for small photosensors with high cost/mm2)
[email protected]
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)
[email protected]
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 inpuritiesFACT
destroyICRC
UV
transmission
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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 …
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FACT
ICRC 2011, Aug 17, Beijing
12
Recent Test Results
Random-Trigger ==> Dark Counts
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FACT
ICRC 2011, Aug 17, Beijing
x 0.5ns
13
Recent Test Results
Random-Trigger ==> Dark Counts
1 cell == 1 photo-electron (~10mV)
[email protected]
FACT
ICRC 2011, Aug 17, Beijing
x 0.5ns
14
Recent Test Results
Random-Trigger ==> Dark Counts
2 cells == 2 photo-electrons
-> cross-talk
1 cell == 1 photo-electron (~10mV)
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FACT
ICRC 2011, Aug 17, Beijing
x 0.5ns
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)
==>
all pix. very similar
3 p.e.
4 p.e.
~5MHz dark counts
<10% cross-talk
Sum of 1435 Pixels without (ADC) calibration!!
[email protected]
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.
<0.5ns (rms) !!!
(without calibration !!!!)
[email protected]
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-CT3 at
La Palma this year
- Gain experience with G-APDs under CT
conditions
[email protected]
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
Will next generation G-APDs be better
than PMTs (price, performance, …) ????
[email protected]
FACT
ICRC 2011, Aug 17, Beijing
19