OBSERVATORY Future application of SiPMs for the fluorescence detection of extensive air showers Lukas Middendorf Physics Institute IIIA Digital Counting Photosensors for Extreme Low Light Levels Lisbon, 20.4.2012 Lukas Middendorf SiPMs for fluorescence detection of EAS 1
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OBSERVATORY
Future application of SiPMs for the fluorescence detectionof extensive air showers
Lukas Middendorf
Physics Institute IIIA
Digital Counting Photosensors for Extreme Low Light LevelsLisbon, 20.4.2012
Lukas Middendorf SiPMs for fluorescence detection of EAS 1
Outline
1 Extensive Air Showers
2 The Pierre Auger Observatory
3 FAMOUS – SiPM based fluorescence telescopeDesignExpected Performance
4 Summary & Outlook
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Lukas Middendorf SiPMs for fluorescence detection of EAS 2
Cosmic ray induced extensive air showers (EAS)
Earth atmosphere is constantly hit by cosmic ray particles with energiesup to several 1020 eVvery low flux⇒ no direct detection possible⇒ use earth atmosphere as calorimeter with large ground based detectorinteraction of particles with air produces multiple secondary particles⇒ extensive air showers down to the ground level
Lukas Middendorf SiPMs for fluorescence detection of EAS 3
Fluorescence detection of extensive air showers
edge of atmosphere
ground
X1
number of p
articles,
N
Xm
axslant
depth
θ
path of shower
fluorescence light
Xtelescope
FOVfluorescence lig
ht
air emits fluorescence light isotropicallywhen excited by shower particles (UV)light ∝ number of particles ∝ energymeasure longitudinal air showerdevelopmentdetermine energy and Xmax
Lukas Middendorf SiPMs for fluorescence detection of EAS 7
SiPMs for
much higher possible photon detection efficiency (∼ 70%) compared tocurrently used PMTs (∼ 30%)demonstrated in prototypes (not currently available for purchase)better angular resolution possible
Build now to learn by manufacturing and demonstrate feasibility
Use Hamamatsu S10985-100C 2× 2 array with 100µm pitch (6× 6mm2
total size), ≈ 30% PDE in UV range
3.0 3.0
ch1 ch4
ch2 ch3
0.4
3.0
3.0
9.0±0.15
8.2 ± 0.15
Lukas Middendorf SiPMs for fluorescence detection of EAS 8
Basic telescope design
Fresnel lens Tube Camera pixels
510 m
m
107 m
m
OA
Focal plane
510 mm
simple refractive design
Lukas Middendorf SiPMs for fluorescence detection of EAS 9
1.5 field of view per pixel
Fresnel lens
remove thick “dead material” of lens⇒ concentric annular sections (“grooves”)approximate curved surface with linearslopeskeeps refraction power of original lens
reduced weightreduced absorptioncheap
compromise in image quality(bigger spot size)
small f /D possible⇒ much light per solid angle⇒ big field of view
Cut thick parts
groove
groove depth
Lukas Middendorf SiPMs for fluorescence detection of EAS 10
Fresnel lens
D = 510mmf = 510mmUV-transparentplastic (PMMA)
Lukas Middendorf SiPMs for fluorescence detection of EAS 11
Point spread function
Distribution of photons in focal plane
x / mm
6 4 2 0 2 4 6
y /
mm
6
4
2
0
2
4
6
rela
tiv
e i
nte
ns
ity
0
5
10
15
20
25
310×
= 1.6 mm90
R
° = 0 in
θ
Optical System
Object Plane Focal Plane
LightLightSpotSpot
90% of light included inred circle R90: 1.6mm≈ 100% included in pixel(green)
simulation with Geant4
point size sufficient for 1.5 field of view per pixel
Lukas Middendorf SiPMs for fluorescence detection of EAS 12
Focal planemodular designhexagonal arrangement of pixelsone pixel: Winston cone (light concentrator) and 6× 6mm2 SiPM arrayUG-11 UV-pass filter64 pixels plannedmanufacturing test with 7 pixels
SiPMs
Light
Lukas Middendorf SiPMs for fluorescence detection of EAS 13