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RICH Status Report
Claudia Höhne, GSI for the CBM RICH group
GSI, GermanyBergische Universität Wuppertal (BUW), GermanyHochschule Esslingen (HSE), GermanyPNPI Gatchina, St. Petersburg, RussiaPusan Natl. University (PNU), Korea(IHEP Protvino, Russia)
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2 14th CBM collaboration meeting, Split, October 2009 C. Höhne
RICH working group
RICH Workgroup
Tuesday, October 6, 2009
Presentation Speaker
11:00 – 11:30 Coffee
11:30 – 11:50 Introduction of Wuppertal group and R&D Plans K.-H. Kampert/ J. Rautenberg (Univ. Wuppertal)
11:50 – 12:10 Status report on Mini RICH I.K. Yoo (Natl. Univ. Pusan) (EVO)
12:10 – 12:30 Status report on mechanical design E.Vznuzdaev (PNPI)
12:30 – 13:00 Results with n-XYTER readout of MAPMT in Lab and Testbeam
J. Eschke (GSI)
13:00 – 15:00 Lunch
15:00 – 15:20 WLS studies (+ brief information on status of mirrors) C. Höhne (GSI)/ M. Dürr (HSE)
15:20 – 15:40 MAPMT and WLS studies P. Koczon (GSI)
15:40 – 16:00 Discussion on RICH R&D (probably to be extended during lunch (and dinner(s))):- status and next steps (→ complete RICH prototype)- coordination of activities - path towards IMoU and TDR - preparation of Technical Board meeting on Thursday, Oct.8
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3 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Outline
• Design
• Photodetector
• MAPMT readout with n-XYter
• testbeam results at GSI, Sep’09
• WLS studies
• Mirror
• prototype, mirror mount design, test bench
• Prototype
• Summary & Plans
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4 14th CBM collaboration meeting, Split, October 2009 C. Höhne
RICH detector for CBM
aim: electron identification for momenta below 8-10 GeV/c
→ high efficiency, large acceptance, 104 combined -suppr. with TRD
.... maybe use also for additional -suppression in K-id at higher p
concept: gaseous RICH detector: stable, robust, fast, econonic costs
rely to a large exetend on components from industry
limited R&D efforts, reduce complications (radiator gas, lenses, 2 mirrors,...)
photomultipliers, e.g. MAPMT H8500
glass mirrors
radiator: CO2
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5 14th CBM collaboration meeting, Split, October 2009 C. Höhne
RICH detector for CBM
e
• electrons: Cherenkov radiation, projected into rings
• pions: Cherenkov threshold pth = 4.65 GeV/c
T.
Gal
atyu
k, U
niv.
Fra
nkfu
rt
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6 14th CBM collaboration meeting, Split, October 2009 C. Höhne
• MAPMT H8500 (8x8 pixel)
•use n-XYTER chip for readout of H8500
• problem: typical gain of H8500 1-2∙106 but dynamical range of n-XYTER 120000 e-
• attenuator board (factor 50) prepared
n-XYTER FEBdesigned as general pupose board
Photodetector
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7 14th CBM collaboration meeting, Split, October 2009 C. Höhne
LED measurements August 2009
LED
PM
MAPMT
lense
Lower half coveredWavelength shifter p-terphenyl
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8 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Attenuator board
n-XYTER
Front End Board(FEB)
Read Out Controller (ROC)
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9 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Before subtracting pedestals(y-log scale)
ADC spectra
channel number ←
J. E
schk
e, G
SI
and
K.
Tod
orok
i (su
mm
er s
tude
nt)
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10 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Entry number Mean value
n-XYter readout of MAPMT
Wavelength shifter p-terphenyl
J. E
schk
e, G
SI
and
K.
Tod
orok
i (su
mm
er s
tude
nt)
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11 14th CBM collaboration meeting, Split, October 2009 C. Höhne
First attempt towards gain uniformity study
WLS coverage
J. E
schk
e, G
SI
and
K.
Tod
orok
i (su
mm
er s
tude
nt)
: each half normalized separately
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12 14th CBM collaboration meeting, Split, October 2009 C. Höhne
STSSTSGEMGEMRICHRICH
DABC + Go4, Slow Control DABC + Go4, Slow Control
TriggerTrigger S3+S4S3+S4
CBM Beam Test @ GSI – 28.8.-8.9.2009CBM Beam Test @ GSI – 28.8.-8.9.2009
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13 14th CBM collaboration meeting, Split, October 2009 C. Höhne
momentum:2.78 GeV/c
45°=44.9°proton
Hamamatsu H8500
~6
cm
“RICH” testbeam setup: MAPMT + readout within CBM setup
• proton beam
• Cherenkov photons generated in plexiglass
• proximity focussing setup (plexiglass tilted in order to avoid total internal reflection)
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14 14th CBM collaboration meeting, Split, October 2009 C. Höhne
raw adc spectra self trigger 8 mm plexiglas
Raw ADC spectra
channel number ←
J. E
schk
e, G
SI
and
K.
Tod
orok
i (su
mm
er s
tude
nt)
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15 14th CBM collaboration meeting, Split, October 2009 C. Höhne
[ns]
Beam
• require coincidence with beam particle
• very low noise rate!
time difference of beam coincidence and signal in MAPMT (selftriggered readout)
?
J. E
schk
e, G
SI
and
K.
Tod
orok
i (su
mm
er s
tude
nt)
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16 14th CBM collaboration meeting, Split, October 2009 C. Höhne
channel number ←
ADC spectra in coincidence with beam
adc spectra with beam trigger 8 mm plexiglas
J. E
schk
e, G
SI
and
K.
Tod
orok
i (su
mm
er s
tude
nt)
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17 14th CBM collaboration meeting, Split, October 2009 C. Höhne
beam
¼ Cherenkov ring – 8mm plexiglass
2D distribution of hits
coincidence with beam
8mm plexiglass
3.5 hits/events
→ single photon counting with self triggered readout!
J. E
schk
e, G
SI
and
K.
Tod
orok
i (su
mm
er s
tude
nt)
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18 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Cherenkov light spectrum
235,92sin221800
3902
c
nm
nm
zLdN
• number of photons produced for a particle with charge ze, a radiator of length L and refraction index n() , Cherenkov angle θc
with L=8 mm, n= 1.49, θc= 44,9o, z=1
c
zL
n
zL
d
dN
2
2
2
222
2
sin2
)(
11
2
≈ 236 Cherenkov Photons are produced J. E
schk
e, G
SI
and
K.
Tod
orok
i (su
mm
er s
tude
nt)
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19 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Estimate (prel.) of Efficiencies
• Geometry: number of photons produced in "quarter segment" / 4
and *64/100 (quarter ring not fully captured)
• Quantum efficiency weighted with yield of produced photons per ∆Eν ~15%
• photon collection efficiency of H8500 ~ 80%
• transmission in plexiglas ~ 80%
Nphotons detected = 236 *0.25*0.64*0.8*0.15*0.8 = 3.62 J. E
schk
e, G
SI
and
K.
Tod
orok
i (su
mm
er s
tude
nt)
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20 14th CBM collaboration meeting, Split, October 2009 C. Höhne
¼ Cherenkov ring – 4mm plexiglass
2D distribution of hits
coincidence with beam
4mm plexiglassbeam
1.3 hits/event
J. E
schk
e, G
SI
and
K.
Tod
orok
i (su
mm
er s
tude
nt)
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21 14th CBM collaboration meeting, Split, October 2009 C. Höhne
ADC channel:47 beam
Halo of proton beam
• in some pixels well separated contribution at very large ADC values (overflow) seen
• generated by protons directly crossing MAPMT?
• (possibility to reduce background from charged hadrons?)
J. E
schk
e, G
SI
and
K.
Tod
orok
i (su
mm
er s
tude
nt)
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22 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Photodetector
• stable operation of n-XYter readout of MAPMT with attenuator board
→ promising path to go for RICH readout electronics!
• low noise level
• successful participation in GSI testbeam, selftriggered readout running together with other participating detectors, online monitoring
→ quantitative analysis: performance of MAPMT? (indirect access to collection efficiency), compare to simulations
→ understand and improve readout electronics (attenuator!)
continue with Lab tests (LED setup)
• crosstalk (in particular with WLS film) ↔ simulation (how much smearing is tolerable?)
• gain uniformity
• ….
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23 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Cross talk = Ncentral/Σnside
First steps towards a crosstalk measurement
• lab setup with LED: cover all pixels but one (or 5 as shown here)
• first results: 3% crosstalk without WLS film (agree to Hamamatsu specifications) 10% with WLS film (simulation: RMS 3mm)
• test loss in ring resolution in simulations!
P.
Koc
zon,
GS
I
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24 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Quantum efficiency of photodetector
• quantum efficiency of photodetector limited by photocathode, window material
• so far used (in lab and simulations) H8500-03 with UV window (>250 nm)
• increase by usage of
• super bialkali cathodes (to be tested in Wuppertal)
• usage of wavelength-shifting films
• (quartz window)
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25 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Wavelength shifting films – principle and application
• Organic molecules absorbing in the short (UV) wavelength region• Strong fluorescence in visible region• Application via evaporation, spin coating/ dip coating
absorptionfluorescence
Example: p-Terphenyl
http://omlc.ogi.edu/spectra/PhotochemCAD/html/p-terphenyl.html
WLS films
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26 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Status and Open questions
Open questions• quantification of gain (reference?)• thickness dependence • combination of absolute and relative q.e. measurements ( > 150 nm)? • uncertainties?
±10%• understanding of plateau?
abso
lute
q.e
.
wavelength [nm]
• P. Koczon (GSI): investigations done in cooperation with CERN (A. Braem, M. v. Stenis, C. Joram)
• Photonis XP3102 used (borosilicate window)
• strong effect seen for < 300 nm
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27 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Gain using wls films
• for the number of measured photoelectrons detector efficiencies (i.e. quantum efficiency) have to be considered:
2
1
2
1
).(.det..
E
E E
ep dEEeqconstdEdE
dNN
E
• the gain of using wls films can be quantified by comparing the integrals with and without their usage
• normalize integral without wls-film to 1
• normalize integral with wls film to integral without
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28 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Gain factor in photoelectrons
• appr. factor 2 in gain compared to uncovered PMT (600 nm < < 150 nm)!
• absorption edge for CO2 ~ 175 nm
• mirror reflectivity drops at ~ 180 nm (prototype from FLABEG)
be careful: … factor 2 compared to PMT with borosilicate glass!
… more like 30% only for UV glass
200 nm
CBM RICH
180 nm → 6.9 eV 180 nm
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29 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Thickness dependence
• no systematic dependence beyond uncertainties observed (see shaded box)
±10%
SEM measurements: J. Kraut, HS Esslingen
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30 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Thickness dependence (II)
• no systematic dependence beyond uncertainties observed (see shaded box)
±10%
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31 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Thickness dependence – Fluorescence measurements
• fluorescence measurements with excitation at 230 nm and 280 nm: some thickness dependence seen!
• enhanced intensity for thicker films (results at 280 nm similar), almost all UV photons are absorbed for films > 100 g/cm2
sample preparation M. v. Stenis (CERN)
M.
Dür
r, H
S E
sslin
gen
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32 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Summary – WLS film studies
• gain of factor 2 in photoelectrons measured with p–Terphenyl coverage of PMT window (borosilicate) for < 150 (180) nm
• …~30% only(?!) with UV window
• no significant thickness dependence observed for wls films > 63 g/cm2 (~0.5 m layer thickness) although expected from fluorescence measurements
• next steps
• fluorescence decay time?
• application techniques, mechanical stability
• long term stability (re-measure stored PMTs)
• crosstalk on MAPMT H8500Si pads
dip coating
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33 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Mirror development
• promising glass prototype (3mm thickness, Al+MgF2 coverage) produced by Compas, Czech Republic
• ordered, waiting for delivery
PNPI Gatchina, St. Petersburg:
• concept developed for mirror mount of thin mirrors
E. Vznuzdaev et al, PNPI Gatchina
M. Dürr, HS Esslingen
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34 14th CBM collaboration meeting, Split, October 2009 C. Höhne
FEM calculations: gravitational deformation
• FEM calculations on gravitational deformation done in
• vertical position: ~ 0.2 microns
• mirrors tilted by ± 20°: < 2 microns
E.
Vzn
uzda
ev e
t al
, P
NP
I G
atch
ina
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35 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Test bench for optical measurements
setup prepared for the measurement of optical quality of mirror+mount
• distortions by mount?
• long term stability
• study adjustment procedure
E.
Vzn
uzda
ev e
t al
, P
NP
I G
atch
ina
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36 14th CBM collaboration meeting, Split, October 2009 C. Höhne
RICH prototype at Pusan
• small RICH prototype at Natl. University Pusan prepared for test of components, test of requirements of gas system and verification of simulations
I.K
Yoo
, J.
G.
Yi e
t al
, P
usan
Nat
l. U
niv.
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37 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Assembly of RICH prototype at Pusan
gas vessel
MAPMTH8500, 1 piece
mirrorFLABEG, 20x20 cm2
I.K
Yoo
, J.
G.
Yi e
t al
, P
usan
Nat
l. U
niv.
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38 14th CBM collaboration meeting, Split, October 2009 C. Höhne
RICH prototype at Pusan (II)
setup at Pohang accelerator lab (electron beam)
I.K
Yoo
, J.
G.
Yi e
t al
, P
usan
Nat
l. U
niv.
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39 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Setup at Pohang accelerator
• 60 MeV electron beam, 1nA
• Wide beam spot (5 cm …. 22 cm)
→ beam quality to be improved: collimation/ absorption – modification of LINAC (see Rossendorf, discussion started)
I.K
Yoo
, J.
G.
Yi e
t al
, P
usan
Nat
l. U
niv.
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40 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Testbeam Summer 2009
• setup brought into operation!
• so far only one H8500 used (¼ ring, ~ 10 photons /ring expected)
• no ring image seen
• to unstable beam conditions for ¼ ring in event average?
• too few photons for e-b-e ¼ ring
• mirror prototype with rather large surface inhomogenity used
next steps:
• add 1(-3) H8500-03 (UV window)
• improve beam quality
• use better mirror prototype
• simulations
I.K
Yoo
, J.
G.
Yi e
t al
, P
usan
Nat
l. U
niv.
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41 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Summary & Plans
• Photodetector:
• MAPMT readout with n-XYter brought into stable operation (testbeam at GSI Sep09, lab setup): quantitative analysis becoming available
→ continue characterization of H8500 in lab, improve readout electronics, new lab being set up at Wuppertal
• Mirror
• concept for mirror mount developed: to be tested with new thin mirror prototype, optical test bench has been prepared
• RICH prototype at Pusan
• assembled, first tests done, continue and improve
• Next (big) steps:
• interim MoU
• complete RICH prototype (Europe) → TDR 2011/2012
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42 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Next big step → prepare complete prototype!
MAPMT readout with n-XYter chip successfully shown in testbeam Sep ’09
→ prepare 4x4 MAPMT plane
first mirror prototype with mount in the near future
→ design prototype with gas system!
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43 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Epilogue
After all cuts applied
ρρ ee++ee--
ee++ee--
φφ ee++ee--
All eAll e++ee--
CBCB
T. Galatyuk, Univ. Frankfurt
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44 14th CBM collaboration meeting, Split, October 2009 C. Höhne
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45 14th CBM collaboration meeting, Split, October 2009 C. Höhne
Timelines/ Milestones
• prototypes of subsystems (photodetector, mirror + support) – Spring/Summer 2010
• complete RICH prototype and tests in testbeam - Spring/Summer 2011
• RICH design simulations of limiting factors - end of 2010
• RICH engineering design - Autumn 2011
• TDR - End of 2011
• be able to apply for funding for construction money in 2011/2012
• finish RICH construction until 2016 (?)
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46 14th CBM collaboration meeting, Split, October 2009 C. Höhne
RICH layout
Reminder:
new – more compact layout developed based on CO2 as gas radiator this way keeping the number of hits/ring
Large Compact
radiator gas N2 CO2
reflective index 1.000298 1.00045
pth [GeV/c] 5.6 4.65
radiator length [m] 2.5 1.5
full length [m] 2.9 1.8
mirror radius [m] 4.5 3
mirror size [m2] 22.8 11.8
photodetector size [m2] 9 2.4
No. of channels 200k 55k
E. Belolaptikova, S. Lebedev, GSI