rich status report claudia höhne, gsi for the cbm rich group gsi, germany bergische universität...

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)

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


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


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


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


• 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


LED measurements August 2009

LED

PM

MAPMT

lense

Lower half coveredWavelength shifter p-terphenyl


Attenuator board

n-XYTER

Front End Board(FEB)

Read Out Controller (ROC)


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)


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)


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


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


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)


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)


[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)


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)


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)


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)


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)


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)


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)


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

• ….


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


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)


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


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


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


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


Thickness dependence

• no systematic dependence beyond uncertainties observed (see shaded box)

±10%

SEM measurements: J. Kraut, HS Esslingen


Thickness dependence (II)

• no systematic dependence beyond uncertainties observed (see shaded box)

±10%


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


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


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


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


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


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.


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.


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.


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.


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.


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


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!


Epilogue

After all cuts applied

ρρ ee++ee--

ee++ee--

φφ ee++ee--

All eAll e++ee--

CBCB

T. Galatyuk, Univ. Frankfurt


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 (?)


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

rich status report claudia höhne, gsi for the cbm rich group gsi, germany bergische universität...

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