1. RICH Status Report Claudia Höhne, GSI for the CBM RICH group GSI, Germany Bergische Universität Wuppertal (BUW), Germany Hochschule Esslingen (HSE), Germany PNPI Gatchina, St. Petersburg, Russia Pusan Natl. University (PNU), Korea (IHEP Protvino, Russia)

2. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 2 RICH working group RICH Workgroup Tuesday, October 6, 2009 PresentationSpeaker 11:00 – 11:30Coffee 11:30 – 11:50Introduction of Wuppertal group and R&D PlansK.-H. Kampert/ J. Rautenberg (Univ. Wuppertal) 11:50 – 12:10Status report on Mini RICHI.K. Yoo (Natl. Univ. Pusan) (EVO) 12:10 – 12:30Status report on mechanical designE.Vznuzdaev (PNPI) 12:30 – 13:00Results with n-XYTER readout of MAPMT in Lab and TestbeamJ. Eschke (GSI) 13:00 – 15:00Lunch 15:00 – 15:20WLS studies (+ brief information on status of mirrors)C. Höhne (GSI)/ M. Dürr (HSE) 15:20 – 15:40MAPMT and WLS studiesP. Koczon (GSI) 15:40 – 16:00Discussion 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

3. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 3 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

4. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 4 RICH detector for CBM aim: electron identification for momenta below 8-10 GeV/c → high efficiency, large acceptance, 10 4 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: CO 2

5. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 5 RICH detector for CBM e  electrons: Cherenkov radiation, projected into rings pions: Cherenkov threshold p th = 4.65 GeV/c T. Galatyuk, Univ. Frankfurt

6. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 6 MAPMT H8500 (8x8 pixel) use n-XYTER chip for readout of H8500 problem: typical gain of H8500 1-2∙10 6 but dynamical range of n-XYTER 120000 e- attenuator board (factor 50) prepared n-XYTER FEB designed as general pupose board Photodetector

7. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 7 LED measurements August 2009 LED PM MAPMT lense Lower half covered Wavelength shifter p-terphenyl

8. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 8 Attenuator board n-XYTER Front End Board(FEB) Read Out Controller (ROC)

9. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 9 Before subtracting pedestals (y-log scale) ADC spectra channel number ← J. Eschke, GSI and K. Todoroki (summer student)

10. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 10 Entry numberMean value n-XYter readout of MAPMT Wavelength shifter p-terphenyl J. Eschke, GSI and K. Todoroki (summer student)

11. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 11 First attempt towards gain uniformity study WLS coverage J. Eschke, GSI and K. Todoroki (summer student) : each half normalized separately

12. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 12 STS GEM RICH DABC + Go4, Slow Control Trigger S3+S4 CBM Beam Test @ GSI – 28.8.-8.9.2009

13. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 13 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)

14. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 14 raw adc spectra self trigger 8 mm plexiglas Raw ADC spectra channel number ← J. Eschke, GSI and K. Todoroki (summer student)

15. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 15 [ns] Beam require coincidence with beam particle very low noise rate! time difference of beam coincidence and signal in MAPMT (selftriggered readout) ? J. Eschke, GSI and K. Todoroki (summer student)

16. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 16 channel number ← ADC spectra in coincidence with beam adc spectra with beam trigger 8 mm plexiglas J. Eschke, GSI and K. Todoroki (summer student)

17. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 17 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. Eschke, GSI and K. Todoroki (summer student)

18. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 18 Cherenkov light spectrum number of photons produced for a particle with charge ze, a radiator of length L and refraction index n( ), Cherenkov angle θ c with L=8 mm, n= 1.49, θ c = 44,9 o, z=1 ≈ 236 Cherenkov Photons are produced J. Eschke, GSI and K. Todoroki (summer student)

19. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 19 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% N photons detected = 236 *0.25*0.64*0.8*0.15*0.8 = 3.62 J. Eschke, GSI and K. Todoroki (summer student)

20. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 20 ¼ Cherenkov ring – 4mm plexiglass 2D distribution of hits coincidence with beam 4mm plexiglass beam 1.3 hits/event J. Eschke, GSI and K. Todoroki (summer student)

21. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 21 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. Eschke, GSI and K. Todoroki (summer student)

22. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 22 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 ….

23. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 23 Cross talk = N central /Σn side 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. Koczon, GSI

24. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 24 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)

25. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 25 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 absorption fluorescence Example: p-Terphenyl http://omlc.ogi.edu/spectra/PhotochemCAD/html/p-terphenyl.html WLS films

26. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 26 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?  absolute 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

27. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 27 Gain using wls films for the number of measured photoelectrons detector efficiencies (i.e. quantum efficiency) have to be considered: 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

28. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 28 Gain factor in photoelectrons appr. factor 2 in gain compared to uncovered PMT (600 nm < < 150 nm)! absorption edge for CO 2 ~ 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

29. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 29 Thickness dependence no systematic dependence beyond uncertainties observed (see shaded box) ±10% SEM measurements: J. Kraut, HS Esslingen

30. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 30 Thickness dependence (II) no systematic dependence beyond uncertainties observed (see shaded box) ±10%

31. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 31 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/cm 2 sample preparation M. v. Stenis (CERN) M. Dürr, HS Esslingen

32. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 32 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/cm 2 (~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 H8500 Si pads dip coating

33. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 33 Mirror development promising glass prototype (3mm thickness, Al+MgF 2 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

34. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 34 FEM calculations: gravitational deformation FEM calculations on gravitational deformation done in vertical position: ~ 0.2 microns mirrors tilted by ± 20°: < 2 microns E. Vznuzdaev et al, PNPI Gatchina

35. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 35 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. Vznuzdaev et al, PNPI Gatchina

36. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 36 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 et al, Pusan Natl. Univ.

37. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 37 Assembly of RICH prototype at Pusan gas vessel MAPMT H8500, 1 piece mirror FLABEG, 20x20 cm 2 I.K Yoo, J.G. Yi et al, Pusan Natl. Univ.

38. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 38 RICH prototype at Pusan (II) setup at Pohang accelerator lab (electron beam) I.K Yoo, J.G. Yi et al, Pusan Natl. Univ.

39. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 39 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 et al, Pusan Natl. Univ.

40. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 40 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 et al, Pusan Natl. Univ.

41. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 41 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

42. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 42 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!

43. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 43 Epilogue After all cuts applied ρ  e+e-  e+e-φ  e+e-ρ  e+e-  e+e-φ  e+e-ρ  e+e-  e+e-φ  e+e-ρ  e+e-  e+e-φ  e+e- All e + e - CB T. Galatyuk, Univ. Frankfurt

44. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 44

45. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 45 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 (?)

46. 14th CBM collaboration meeting, Split, October 2009 C. Höhne 46 RICH layout Reminder: new – more compact layout developed based on CO 2 as gas radiator this way keeping the number of hits/ring LargeCompact radiator gasN2N2CO2 reflective index1.0002981.00045 p th [GeV/c]5.64.65 radiator length [m]2.51.5 full length [m]2.91.8 mirror radius [m]4.53 mirror size [m 2 ]22.811.8 photodetector size [m 2 ]92.42.4 No. of channels200k55k E. Belolaptikova, S. Lebedev, GSI