Optical Part of the CMB for AHCAL-CALICE Jaroslav Zalesak Institute of Physics, Prague.

Optical Part of the CMB for AHCAL-CALICE

Jaroslav ZalesakInstitute of Physics, Prague

Jaroslav Zalesak ECFA 2008 - Jun 10, 2008 - Warsaw, Poland

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Present system: one tile – one optical fibrecomplicated systemIdea: use one fibre for more tiles, ideally one row of tiles – one fibre

How to do it? a) Side-emitting fibres Problems: search thin (~1mm) fibres, unknown parameters, cost → FiberTech (SLS600 series)

b) ’Notched’ fibres Making notches on fibres (manually) → Safibra company (PoF) Non-uniformity of emitting light → measurement

c) Focusing enough LED light into fibre → in progress


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3-meter-long setup to have straight line fiber position (avoid twisting)

CMB + UV LED pulsing light - PMT R647 Hammatsu – Scope Readout

Measurement setup I


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Side – emitting fiber (FiberTech)

Running differential of attenuation of side-emitting light at length of 50, 100, 150 and 200 cmaveraged of 75%, 55%, 40% and 30%

(Exponential decrease expectation softly violated)

Side emitting light intensity decreases along fiber (position in cm from the UV LED source)

Dependence of signal amplitude [mV] on position of PMT

Differential of Attenuation of side emitting light

Δ = 50

100

150200 cm

Fiber 1

Fiber 2


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Conclusion I

All found and measured side-emitting fibers show same results within systematic uncertainties

Side-emitting light intensity decreases along the fiber going from UV LED light source to the free end of fiber down to 20-30% at position > 2.5 m from source

Attenuation of side-emitting light at length of 1m and 2m are approx. at level of 55% and 25%, resp.

not fully sufficient fibers for calibration system due to non-uniformity in response and absolute int.


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Measurement setup II- Notched fibers Prototype of 5m long notched fiber delivered two groups of notches in the middle and tail one (~1mm long) cut per position of 6 or 12 cm int. (optical department of SAFIBRA company)

QR LED driver, T- and V-calib UV LED fiber with notches scintillating tile 3x3cm w/ WLS fiber going to SiPM fiber fixed in middle of top plane PS for SiPM Ubias preamp (gain of 10) R/O scope and ADC (VME) LabView DAQ


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SiPM response to MIP

Cosmics Sr90

MIP from cosmics ~ 7 pixelsMIP from Sr90 ~ 8 pixels


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Results IRepeated measurement of side-emitting fiber with SiPM response in 3 different position for four UV LEDlight intensities (5 = maximum LED light from driver)

55% decrease of response in 75 cm within light intensities of more then 1 order

Side-emitting fiber

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

0 20 40 60 80 100 120

Distance [cm]

Am

pl [

MIP

]

Light Int. = 2 Light Int. = 3 Light Int. = 4 Light Int. = 5


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Safibra fiber w/ cuts

0.0

5.0

10.0

15.0

20.0

25.0

30.0

200 250 300 350 400 450 500 550

Distance [cm]

Am

pl [

MIP

]

Tail Middle

Safibra fiber w/ cuts

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2.00

5 7 9 11 13 15 17 19 21Point #

Re

l. A

mp

l

Tail Middle

Amplitude measuredin MIPs along the fiber 5 points every 12 cm 9 points every 6 cm (points = one 1mm cut) in average:Tail 17.2 MIPsMiddle 18.6 MIPs

Normalized amplitude over14 measured points dividedto 2 groups acc. to positionalong fiber: middle part (~2.5m) tail part (~5m)

SiPM response on LED light varies -40 to 30 % RMS = 22% does not depend on distance from light source

Results II


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At highest light intensities the notched fiber shows much bigger SiPM response going from 55% to 170% with increasing distance from light source (up to 1m vs 5m)

3 position of side-emitting fiber 1 position (tail of 5m) notched fiber

Results III

Side-emitting x fibres w/cut

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

1 1.5 2 2.5 3 3.5 4 4.5 5 5.5

Light intensity

Am

pl [

MIP

]

25 cm 50 cm 75 cm Tail_10 (5m)


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Conclusion II

First fiber prototype with test notches measured Response over 5m length varies with RMS of 22% Any visible change in uniformity Light output from notched fiber > 2.7times higher

than from side-emitting fiber

we need still more light intensity from fiberI. bigger notches on fiber or multiplying themII. focusing enough LED light into one fiber

Both direction will be further investigated in June

Optical Part of the CMB for AHCAL-CALICE Jaroslav Zalesak Institute of Physics, Prague.

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