Transcript J. Zalesak: Optical system for HCAL calibration

Optical System for
HCAL calibration

Notched fiber prototype
 Optical X-talk
 Distance Tile-Fiber
Jaroslav Zalesak
Institute of Physics, Prague
J. Zalesak
CALICE, Manchester Sep 9, 2008
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We consider 2 scenarios of calibration
system for technical prototype of
AHCAL
QR driver + LED
1. Fiber emmiting light
for one row of tiles,
QRLed driver sitting
outside of module
(endcap) 
development of the
light distribution system
2. QRLed driver is sitting
at HBU above the
scintillator
J. Zalesak
24*3cm² area
needed at the
main PCB
CALICE, Manchester Sep 9, 2008
24 fibers
Each for
~ 70tiles
2
Ampl [MIP]
Light distribution
system
Side-emitting fiber
14.0
12.0
10.0
a) Side-emitting fibres
Thin fibres (~1mm) needed, unknown
parameters, not common → FiberTech
(SLS600 series)
b) ’Notched’ fibres
8.0
6.0
4.0
2.0
Making notches on fibres requires a
specialized firm → Safibra comp.
c) Focusing LED light into fibre →
0.0
0
20
40
60
80
100
120
Distance [cm]
Light Int. = 2
Light Int. = 3
Light Int. = 4
Light Int. = 5
Optical lab of the CU Prague
Notched fibres appear
promissing:
 Response over 2.2m length drops
linearly by 40%, RMS ~ 14%
 Light output from notched fibers
> ~ 3 times higher
J. Zalesak
CALICE, Manchester Sep 9, 2008
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Notched fiber prototype #3
 Light output from fiber via notches uniform over all 70 points
 Approaching ±20% proposed limit of light variation
 New (better) notched fiber is expected soon
J. Zalesak
CALICE, Manchester Sep 9, 2008
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Optical X-talk on MIP
β-source
with fiber
Β spectrum
• Sr beta source to SiPM1
• triggered by coinc. w/PM
• notched fiber SiPM 1→2
• at length of 9 cm
• ½ MIP on position 135
w/o fiber
➢ Normalized spectra w/ and w/o fiber are same
 NO optical X-talk visible for MIP beta spectra
J. Zalesak
CALICE, Manchester Sep 9, 2008
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Optical X-talk on LED light
• Much more light to tile (up to 25 Mips)
• not particle but tunable amplitude
• better triggering
2 MIPs
10 MIPs
25 MIPs
J. Zalesak
• LED light to SiPM1
• notched fiber SiPM 1→2
• at length of 9 cm
• ½ MIP on position 135
CALICE, Manchester Sep 9, 2008
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Optical X-talk on LED light
results
Noise
2 MIPs
10 MIPs
25 MIPs
½ MIP detail
 No differences in response from various amplitudes
 NO optical X-talk visible for large amount of light in tile
 no dependence on chosen pair of notches
and light input direction
J. Zalesak
CALICE, Manchester Sep 9, 2008
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Distance Fiber-Tile
• variable sheet width in space of coupling (air)
of fiber notch and tile
• two intensities of input led light from LED driver
• one tile w/ SiPM direct coupling
→ monitoring of stability (yellow and green)
• second measure amplitude (blue and red)
Preliminary results:
 not so good reproducibility (10%)
 significant drop in response
 decrease with bigger distance (30%)
 visible even on small widths
 some additional reflections in case
direct coupling wrt. some materials?
 better geometrical setup?
J. Zalesak
CALICE, Manchester Sep 9, 2008
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Conclusion
 we have got and measured promising fiber with notches
wait for new prototype w/ uniformed light distribution within ranges ± 20%
 we do not expect (or less 1-2%) optical X-talk between
tiles from notch coupling even on high light intensity
 we observed significant drop in response from tiles
with not directly coupled fibers
→ need more precise measurement, better couplings and geometry setup
Btw: in 1 week new designed PCBs for QR-Led driver go to production
J. Zalesak
CALICE, Manchester Sep 9, 2008
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