1. Photodetector developement
CBM October 2008
Piotr Koczoń,GSI
CBM-RICH:
Photodetector developement
P.Koczoń, C.Höhne, A.Braem
C.Joram, M. van Stenis

2. Photodetector for RICH
CBM October 2008
Piotr Koczoń,GSI
Photodetector for RICH
- Wavelength Shifter technologies
- Single photon capability of H8500
WLS on a H8500
- Outlook/Plans

3. Photodetector for RICH
CBM October 2008
Piotr Koczoń,GSI
Photodetector for RICH
- Array photomultiplier: H8500 (H9500?)
- Why wavelength shifter? And what type?
(Tetra Phenyl Butadiene = TPB,
meta-P-terphenyl = pTer,
pTer on teflon)
- WLS gain measured immediately after coating
and after 3 months in CO2 atmosphere
thickness studies 75/100/125 µg/cm2 for pTer
pTer/teflon WLS

4. H8500 8x8 pads 5.8 x 5.8 mm each 89% packing density U=1100 V but
CBM October 2008
Piotr Koczoń,GSI
H8500
8x8 pads
5.8 x 5.8 mm each
89% packing density
U=1100 V
but
borosilicate window
and low QE for UV

5. H8500: room for QE improvements
CBM October 2008
Piotr Koczoń,GSI
H8500: room for QE improvements
WLS coating: technology, measurements, results
absorbtion
emission

6. Monochromator Vacuum deep UV relative QE QE Test Bench (HPD) Air
CBM October 2008
Piotr Koczoń,GSI
Monochromator
Vacuum
deep UV
relative QE
QE Test Bench (HPD)
Air
200 nm cut off
abs. QE measurement

7. QE for XP3102 @ far UV with WLS
CBM may 2008
Piotr Koczoń,GSI
QE for far UV with WLS
for TPB
PM1 – X3102 number 1
235 ug/cm2 – coating thickness
For these tests a set of
Photonis XP3102 was
used.
for p-Ter

8. QE gain for XP3102 @ far UV with WLS
CBM may 2008
Piotr Koczoń,GSI
QE gain for far UV with WLS
for TPB
Gain:
for p-Ter
Gain:

9. after 3 months in CO2 normal pressure
CBM October 2008
Piotr Koczoń,GSI
QE of UV with p-Ter
after 3 months in CO2 normal pressure
F8 – measured in Feb 2008
J8 – measured in Juni 2008
Ageing almost not visible (within error bar)

10. Accuracy of QE measurement
CBM October 2008
Piotr Koczoń,GSI
Accuracy of QE measurement
After rebuilding of absolute QE monochromator
a new adjustment and callibration was needed

11. Gain factor for XP3102 @ UV with pTer
CBM October 2008
Piotr Koczoń,GSI
Gain factor for UV with pTer
Thickness study
for p-Ter

12. Gain dependency on p-Ter thickness
CBM October 2008
Piotr Koczoń,GSI
Gain dependency on p-Ter thickness
Results at exacltly
100μg/cm2
not quite understood
pTer thickness 90 – 125 μg/cm2 is an optimum

13. WLS results & conclusions
CBM October 2008
Piotr Koczoń,GSI
WLS results & conclusions
pTer layer can increase the quantum efficiency of an
photomultiplier considerably in far UV
TPB less suitable (other materials?)
Ageing of pTer in CO2 not visible after 3 months
90 to 125 μg/cm2 seems to be an optimal thickness
Other technologies (pTer spraying) not examined yet

14. pTer/teflon WLS made in RU
CBM October 2008
Piotr Koczoń,GSI
pTer/teflon WLS made in RU
250 µg/cm2 pTer on
50 µm thin teflon foil
Courtesy of V.Rykalin

15. pTer/teflon WLS made in RU
CBM October 2008
Piotr Koczoń,GSI
pTer/teflon WLS made in RU

16. CBM October 2008
Piotr Koczoń,GSI
pTer/teflon made in RU

17. pTer/teflon in Vacuum Gain of pTer on teflon in vacuum & ABS
CBM October 2008
Piotr Koczoń,GSI
pTer/teflon in Vacuum
Gain of pTer on teflon in vacuum & ABS
pTer on teflon
seems to be
mechanically
less stable than
directly evaporated
on the entrance
window of the PM

18. pTer on teflon Gain of pTer on teflon appreciably high
CBM October 2008
Piotr Koczoń,GSI
pTer on teflon
Gain of pTer on teflon appreciably high
Teflon foils are not flat (heat treatment?)
pTer on teflon mechanically unstable

19. pTer on H8500 100 µg/cm2 pTer evaporated directly on H8500 entrance
CBM October 2008
Piotr Koczoń,GSI
pTer on H8500
100 µg/cm2 pTer
evaporated directly
on H8500 entrance
window (50%)

20. pTer on H8500 in the vacuum monochromator
CBM October 2008
Piotr Koczoń,GSI
pTer on H8500 in the vacuum monochromator
8 x Signal HV
Air instead of Ar
introduces a cut off
at 190 nm

21. pTer on H8500 + coated * illuminated Anode current Wavelength [nm]
CBM October 2008
Piotr Koczoń,GSI
pTer on H8500
+ coated
* illuminated
Anode current
Wavelength [nm]

22. GAIN of pTer on H8500 + coated * illuminated
CBM October 2008
Piotr Koczoń,GSI
GAIN of pTer on H8500
+ coated
* illuminated
Only coated AND illuminated pixels
show enhanced gain (>1)

23. Conclusions – Part 1 WLS improves QE in UV region
CBM October 2008
Piotr Koczoń,GSI
Conclusions – Part 1
WLS improves QE in UV region
pTer is better WLS than TPB
100μg/cm2 of pTer is an optimum
ageing of pTer almost not visible (3 mon. in CO2)
WLS on teflon works astonishingly well
WLS on H8500 works as well

24. H8500 opto-electronical properties:
CBM October 2008
Piotr Koczoń,GSI
H8500 opto-electronical properties:
Single Photon Counting: measurements, results

25. Single photon counting capability (setup)
CBM October 2008
Piotr Koczoń,GSI
Single photon counting capability (setup) HV
Light guide bundle
LED PM
grey filters
Light
tight box
PulseGenerator
signal
Pico FADC
gate

26. Single photon counting capability (reality)
CBM October 2008
Piotr Koczoń,GSI
Single photon counting capability (reality)
Light guide
bundle
LED
Light
tight
box
grey filter HV
signal
Pulse
generator
(a bad one)

27. Single photon counting capability - results
CBM October 2008
Piotr Koczoń,GSI
Single photon counting capability - results
Using a PC+PicoScope
(2 channels, 1 GS 8 bit FADC)

28. Single photon counting capability - results
CBM October 2008
Piotr Koczoń,GSI
Single photon counting capability - results
X2020
Hamamatsu 2“ X2020
is known as a SPC PM
H8500
Thermal Electrons noise
Photons
SP = Photons „-“ noise
Encouraging!!!

29. Single photon counting capability - results
CBM October 2008
Piotr Koczoń,GSI
Single photon counting capability - results
Counts
Signal Width
Amplitude
Amplitude/Charge
Counts
Counts
Single Photons
Time [ns]
Amplitude/Charge
quite convincing

30. Single photon counting capability - results
CBM October 2008
Piotr Koczoń,GSI
Single photon counting capability - results
Pretty sure!

31. Single photon counting capability:
CBM October 2008
Piotr Koczoń,GSI
Single photon counting capability:
H8500 is able to register single photons

32. Newest results: WLS on H8500: measurement of a H8500
CBM October 2008
Piotr Koczoń,GSI
Newest results:
WLS on H8500:
measurement of a H8500
coated with 100μg/cm2 of pTer
using
PANDA/HADES/FAIR TRB
Data Acquisition System

33. WLS on H8500 (PANDA TRB DAQ) Schematic view of the HV
CBM October 2008
Piotr Koczoń,GSI
WLS on H8500
(PANDA TRB DAQ) HV
Schematic view of the
first multiparameter measurement
of WLS/H8500 properties
UV LED
H8500
20 cm
Light
tight box
PulseGenerator
signal
PANDA TRB DAQ
gate

34. PANDA TRB DAQ Courtesy of C.Sfienti & M.Traxler
CBM October 2008
Piotr Koczoń,GSI
PANDA TRB DAQ
A General Purpose Trigger and Readout Board for HADES and FAIR-Experiments
Frohlich, I.; Kajetanowicz, M.; Korcyl, K.; Krzemien, W.; Palka, M.; Salabura, P.; Schrader, C.; Skott, P.; Strobele, H.;
Stroth, J.; Tarantola, A.; Traxler, M.; Trebacz, R.; Yurevich, S.
Nuclear Science, IEEE Transactions on Volume 55, Issue 1, Feb Page(s):
Digital Object Identifier /TNS
Courtesy of C.Sfienti & M.Traxler

35. WLS on H8500 (PANDA TRB DAQ) High light intensity Piotr Koczoń,GSI
CBM October 2008
Piotr Koczoń,GSI
WLS on H8500
(PANDA TRB DAQ)
High light intensity

36. WLS on H8500 (PANDA TRB DAQ) low light intensity – single photons
CBM October 2008
Piotr Koczoń,GSI
WLS on H8500
(PANDA TRB DAQ)
low light intensity – single photons

37. WLS on H8500 (PANDA TRB DAQ) 100μg/cm2 pTer Multipin connectors
CBM October 2008
Piotr Koczoń,GSI
WLS on H8500
(PANDA TRB DAQ)
100μg/cm2 pTer
Multipin connectors
(only two sixteen-fold
cables were available)

38. PRELIMINARY WLS on H8500 (PANDA TRB DAQ) counts Time [ns]
CBM October 2008
Piotr Koczoń,GSI
WLS on H8500
(PANDA TRB DAQ)
PRELIMINARY
counts
Time [ns]
Channel number

39. PRELIMINARY WLS on H8500 (PANDA TRB DAQ) Counts Channel#->Pixel#
CBM October 2008
Piotr Koczoń,GSI
WLS on H8500
(PANDA TRB DAQ)
PRELIMINARY
Counts
Channel#->Pixel#

40. Cross-talks – future plans
CBM October 2008
Piotr Koczoń,GSI
Cross-talks – future plans
WLS can add an additional cross-talk between
neighbouring pixels when a photon falls inclined or undergoes absorbtion-reemision in the WLS layer
on PMs entrance window
Hamamatsu claims for H8500: cross talk < 3%
Photon transformed in WLS
Inclined photon
Propagation in WLS
WLS
Borosilicate
Window (1mm)
PM structure

41. Cross-talks - setup HV Light guide bundle LED grey filter Light
CBM October 2008
Piotr Koczoń,GSI
Cross-talks - setup HV
Light guide bundle
LED
H8500
grey filter
Light
tight box
XY-table
PulseGenerator
signal
DAQ TRB
gate

42. CBM October 2008
Piotr Koczoń,GSI
Cross-talks - setup

43. WLS on H8500 – no conclusions yet, but:
CBM October 2008
Piotr Koczoń,GSI
WLS on H8500 – no conclusions yet, but:
Using PANDA DAQ and 32 parameters
WLS gain effect on H8500 can be confirmed
cross-talk investigations possible/necessary
nXyter readout urgently needed!!!

44. CBM October 2008
Piotr Koczoń,GSI
Thank You !