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CBM-RICH: Photodetector developementH8500+nXyter+ROC readout

P.Koczoń, R.Karabowicz, R.Lalik, C.Schmidt, V.Kleipe, W.F.J.Müller

CBM March 2009 Piotr Koczoń,GSI

H8500+UV LED + nXyter readout Optical properties of pTer – résumé Outlook: WLS foils

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CBM March 2009 Piotr Koczoń,GSI

H8500

HV

PulseGeneratornXyter+ROC

Lighttight box

UV LED

gate signal

20 cm

H8500+nXyter+ROC - setup

Schematic view of themultiparameter measurementof WLS/H8500 properties Aperture mask

with pinholes

ChargeDivider

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CBM March 2009 Piotr Koczoń,GSI

H8500+nXyter+ROC - setup

ChargeDivider nXyter

ROC

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CBM March 2009 Piotr Koczoń,GSI

Charge divider

H8500 multiplication factor ~106 @ 800V biasing voltage but sensitivity

of nXyter input ~ 5 mips (125000 e) => an adapter is necessary!!

The charge divider (details in http://cbm-wiki.gsi.de/cgi-bin/viewauth/Rich/CbmRichMeeting031208 )

is a C/R circuit :PMT N-XYTER

We prepared several boards with different sets of R1, R2, C1, C2:

R1 R2 C2 C1

0 10 k 1 nF 10 pF

91 10 0 nF 2 pF

0 100 1 nF 10 pF

91 10 0 nF 10 pF

0 100 0 nF 10 pF

50 10 k 10 pF 470 pF

(Simone Bianco)

S3

S5

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CBM March 2009 Piotr Koczoń,GSI

Charge divider – 3rd try: not so bad

10 ns

1.6 V

15 ns

40 mV, S5

More advanced simulations by Tim Armbruster Uni HDresult in an attenuation factor of 48.71

Qin

Qout

Qin / Qout = attenuation factor

H.C. Soltveit (one of nXyter developers)claims that it should be possible to trimmthe chip such, that the charge dividerwill be obsolete.

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CBM March 2009 Piotr Koczoń,GSI

H8500 pinhole aperture

Aperture mask

Pin holes

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CBM March 2009 Piotr Koczoń,GSI

System noise

Channel #

Am

plitu

de [

ch]

nXyter has a very sensitive input, it is very noisy.Only by adjusting of global (and channel)offsets and thresholds can be done operational.

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CBM March 2009 Piotr Koczoń,GSI

H8500 signal readoutCh#1 …

… Ch#64Collected charge

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Col

lect

ed c

harg

e

CBM March 2009 Piotr Koczoń,GSI

H8500 – signal readout

Channel #

18 channel# 82 112

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CBM March 2009 Piotr Koczoń,GSI

H8500 readout

82

108

78

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CBM March 2009 Piotr Koczoń,GSI

H8500 readout

H8500 - rear side

Pixelnumber - Channel number - correspondence

112 -> P32

78,82 -> P29, P30

18 -> P4

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CBM March 2009 Piotr Koczoń,GSI

?

H8500 readout

There ist obviously a misaligment betw.the mask and the PM

P4 not understood

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CBM March 2009 Piotr Koczoń,GSI

WLS

Window (1mm)

PM structure

To do 1) H8500 cross-talk – future plans

Hamamatsu claims for H8500: cross talk < 3% (electronics)

WLS can add an additional cross-talk between neighbouring pixels when a photon undergoes absorption-reemision in the WLS layer or falls inclined on the PMs entrance window

Simulations (Paola Solevi, Det.Lab. CERN): σ=3mm(WLS layer)

Inclined photonPhoton transformed in WLS

Propagation in WLS

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CBM March 2009 Piotr Koczoń,GSI

To do 2) Single photon counting capability using H8500+CD+nXyter+ROC

Single photon?

Double hit?

Single Photon Counting capabilityhas been demonstrated (Dubna 2008) in a coincidence measurementwith 2“ Hamamatsu X2020 and Picoscope.

SPC has to be also proved for H8500with nXyter!

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CBM March 2009 Piotr Koczoń,GSI

Ad 2) Single photon counting capability using H8500+CD+nXyter+ROC

Channel #

delta

T[n

s]

Coincidence measurement using nXyter system

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CBM March 2009 Piotr Koczoń,GSI

Conclusions (Part 1)

- nXyter+ROC with CD seem to work with H8500- Further measurements of a) cross talk between pixels with and w/o WLS coating b) single photon counting capability with nXyter system are necessary

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CBM March 2009 Piotr Koczoń,GSI

WLS – summaryP.Koczoń, C.Höhne, A.Braem

C.Joram, M. van Stenis

- choice of the wavelength shifter material- silicon pads with WLS

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CBM March 2009 Piotr Koczoń,GSI

Choice of the WLS material

- Several WLS materials have been tested (TPB, pTerphenyl, YellowX)- Different coating methods (evaporation, spraying)- evaporated p-Terphenyl shows the highest gain- ageing in CO2 not (yet) observed- timing properties not studied

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CBM March 2009 Piotr Koczoń,GSI

Integrated QE of pTer and TPB as function of photon energy

pTerphenyl shows the highest integrated gain

extrapolation

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CBM March 2009 Piotr Koczoń,GSI

WLS embeded in silicon padsWLS - Si pad

PM structure

Window (1mm)

~0.3 mm

Advantages:1) Much easier production as compared to evap. procedure2) Can be prepared in advance in different thicknesses and WLS concentrations3) Can be changed on the PM at any time4) Can be easily exchanged in case of damage5) WLS material protected from chem. influences

? Does it work at all ??? Is thickness an issue ??

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CBM March 2009 Piotr Koczoń,GSI

Thank You !

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CBM March 2009 Piotr Koczoń,GSI

Cross-talks - setup

H8500

HV

PulseGeneratorDAQ

grey filter

Light guide bundle

Lighttight box

LED

gate

signal

XY-table