Study of GEM-like detectors

Transcription

1 Study of GEM-like detectors with resistive electrodes for RICH applications A.G. Agocs 1, A. Di Mauro 2, A. Ben David 3, B. Clark 4, P. Martinengo 2, E. Nappi 2,5, V. Peskov 2,6, 1 Eötvös ö University, it Budapest, Hungary 2 CERN, Switzerland 3 Tel Aviv University, Israel 4 North Carolina State University, USA 5 Bari University 6 Ecole Superior des Mines, St Etienne, France 1

2 Recent results from RHIC as well as numerous theoretical predictions indicate that a very high momentum particle identification (VHMPID) may be needed in the future ALICE experiments. In connection to this the ALICE-HMPID collaboration is studying the possibility to make a new detector to identify charged particles with momentum p > 5 10 GeV/c VHMPID (Very High Momentum Particle Identification Detector). t t ) Several Cherenkov detector designs were preliminary considered and simulated by the ALICE VHMPID collaboration : a threshold type as well as a RICH type (see G. Volpe talk at this Conference). 2

3 One of the complication- there is a very limited space available for VHMPID So only compact and simple VHMPID designs can be considered 3

4 Focusing setup The focusing properties of a spherical mirror of radius R = 240 cm, are exploited. The photons emitted in the radiator are focused in a plane that is located at R/2 from the mirror center, where the photon detector is placed. Charged particle 100 cm 100 cm Photon detector CaF 2 window 120 cm Gas C 5 F 12 volume Mirror (from G. Volpe talk at this Conference). 4

5 One of the promising photodetector element in this RICH design could be GEM-like detectors combined with CsI photocathodes Advantages : They are compact Can operate at higher gains and in badly quenched gases including inflammable gases Can be used in the same gas as a radiator Have high QE Have potential for higher special resolution 5

6 For the last several years we were focused on developing more robust GEM-like detectors for RICH application 6

7 First attempt- Optimized /Thick GEM Further development of this detector was performed by Breskin group- see R. Chechik presentation 7

8 Photo of one of the optimized or thick GEM developed by us earlier L. Periale et al., NIM A478,2002,377 J. Ostling et al., IEEE Nucl. Sci 50,2003,809 TGEM is manufactured by standard PCB techniques of precise drilling in G-10 (+ other materials) and Cu etching. 8

9 We would like present today a new promising direction- resistive electrodes TGEMs 9

10 The main advantage of these detectors t is that t they are fully spark-protected protected 10

11 Thick GEM with resistive electrodes (RETGEM)- a fully spark protected detector A. Di Mauro et al, Presented at the Vienna Conf. on Instrum; to be published in NIM Principle of operation Geometrical and electrical characteristics: Holes diameter mm, pitch mm, 30mm thickness mm. Resitivity: kΩ/ or Kapton type: 100XC10E 70mm 11

12 F u l l y s p a r k - p r o t e c t e Summary of the main preliminary results obtained with kapton RETGEMs 1 mm thick Gain 1.00E E+05 nar 1.00E+04 Ne 1.00E E Voltage (V) Ar+CO 2 Energy resolution ~30%FWHM for 6 kev Discovery: kapton can be coated with CsI and have after high QE Filled symbols-single RETGEM, open symbols double RETGEMs Stars-gain measurements with double RETGEM coated with CsI layer. 15 min continues discharge harm ether the detector or the electronics e am plitude (m V ) Puls E E E E E+08 Rate (Hz/cm 2 ) QE~30% at λ=120nm With increase of the rate the amplitude drop, but now discharges d 12

13 Confirmation of high QE (QE measurements at 185 nm) 13

14 QE calibration TMAE filled single-wire gas counter Hg lamp Windows Monochromator Lens CsI Q CsI =Q TMAE N CsI /N TMAE Double-step RETGEMS with CsI photocathode 14

15 Photo of the experimental set up Hg lamp Lens Monochromator Gas chamber with RETGEM coated with CsI 15

16 Experimental set up for studies RETGEM with CsI photocathodes UV light Window HV feedthrough Drift mesh Top RETGEM CsI (0.35μm) -V dr V 1 top V 2 top Gas out Bottom RETGEM Gas in Charge sensitive or current amplifier 16

17 Counting plateau TMAE detector Counting Rate (Hz) Fe before Fe after Fe UV light TMAE detector Voltage (V) Double RETGEM 17

18 Hg lamp spectra, measured with TMAE (a) () detector and RETGEM () (b) TMAE QE vs. wavelength (c) a) c) b) Q CsI =33%N CsI /N TMAE ~ 14.5% (assuming that TMAE is clean enough) 18

19 Measurements of the stability of the RETGEM, using Hg as a source, at 185nm. The light is concentrated on a small slit. About 30min without light have passed between each run. 19

20 Stability measurements of photosensitive RETGEM 20

21 Very low single photoelectron counting rate Double K- RETGEM with CsI pc Counting rate Time (min) Gas gain~

22 Single electron (CsI pc) counting rate at a constant threshold Gas gain~ 10 6 This behavior is similar to RPC 22

23 Long term stability of CsI pcs measures at low counting rate K-TGEM, CsI pc#1 QE (%) Time (days) K-TGEM, CsI pc#2 QE (% %) Time (days) 23

24 Unexpected problem-very difficult to get the resistive kapton from the US Dear Mr. Peshkov, I'm in charge of sales and marketing of Kapton polyimide film in Europe. As explained in attached notes Kapton 100XC10E5 is subject to an ITAR license to be exported from the US and this is indeed quite a complex procedure to go through. Suggest you call me at in order to discuss how we can proceed. My best regards, Giulio Cecchetelli High Performance Films DuPont de Nemours (Luxembourg) S.à r.l. Société à responsabilité limitée au capital de Euro Rue Général Patton L-2984 Luxembourg R.C.S. Luxembourg B

25 Very new (preliminary) results: RETGEMs manufactured by screen printing technology For more details see: B. Clark et al., Preprint/Physics/ , Aug

26 26

27 Screen printing is widely used in microelectronics to produce patterns of different shape and resistivity. Therefore, RETGEM technology produced with screen printing techniques offers a convenient and widely available alternative to RETGEMs made of Kapton. Advantages of the screen printing technology: Offers cost-effectiveness, convenience, and easy optimization RETGEMs resistivity and geometry. It is also important to mention that large -area RETGEMs can be produced by this technology. 27

28 Consequent steps in RETGEM manufacturing in by screen printing technique (Oliveira Workshop): a) DE-156, an Isola product, is used as the base material. b) Excess copper is removed from the top and bottom, thereby creating a copper border. c) A resistive paste (Encre MINICO ) is applied to the top and bottom surfaces using screen printing techniques and technology. The paste is cured in air at 200 C for one hour. After the curing process is complete, the resistive layer is 15μmthick thick. d) Drill consistently tl sized holes at even intervals in the region enclosed by the copper border. 28

29 Two types of RETGEM were manufactured by screen printing technology and tested RETGEM type- 1 Geometrical and Resistive Characteristics Thickness = 1mm Hole Diameter = 0.5mm Pitch = 0.8mm Active Area = 30mm x 30mm Resistive Layer Thickness = 15μm Resistivity = 1 MΩ/ or 0.5 MΩ/ RETGEM type -2 Geometrical and Resistive Characteristics Thickness = 0.5mm Hole Diameter = 0.3mm Pitch = 0.7mm Active Area = 30mm x 30mm Resistive Layer Thickness = 15μm Resistivity = 0.5 MΩ/ 29

30 Photo of holes at various magnifications: a) medium magnification b) higher magnification 30

31 Experimental set up for studies RETGEM manufactured by screen printing technology Radioactive source Drift mesh Window HV feedthrough -V dr Gas out RETGEM Gas in Charge sensitive amplifier 31

32 Experimental set up for studies RETGEM manufactured by screen printing technology Radioactive source Drift mesh Window HV feedthrough -V dr Top RETGEM V 1 top V 2 top Gas out Bottom RETGEM Gas in Charge sensitive amplifier 32

33 Results of measurements in Ne (SP-RETGEM type 1) Signal (V) B A Alpha particles Voltage (V) Gain curve measured with single SP-RETGEM ( 55 Fe). Gain 1.00E E E E E E E Voltage (V) 1.00E+06 Gain 1.00E E+04 Breakdownn Gain curve measured with double SP-RETGEM operating in Ne ( 55 Fe). 100E E Voltage across RETGEM-2 33

34 Results obtained in Ar (SP-RETGEM type1) gain Fe-55 Single step SP-RETGEM 1 gain 1 alpha GEM voltage (V) V 2300V 2100V Double SP-RETGEM gain GEM bottom2 (V) 34

35 Results obtained in Ar+CO 2 (type1) 1000 gain Single step GEM bottom plate voltage (V) V 2700V 2500V 2400V gain 1000 Double SP-RETGEM GEM bottom2 (V) 35

36 Low resistivity (0.5MΩ/ ) it )1mm thick double step in Ne (preliminary!) Double SP-RETGEM, low resistivity in Ne 1.00E E E V gain 1.00E E V 300V 1.00E E Voltage on bottom RETGEM 36

37 The maximum achievable gain with a 0.5 mm thick SP- RETGEM was the same as in the case of the 1 mm thick, however there voltages were considerably smaller Gain of RETGEM type 2 Gain 1.00E E E+01 Alphas 1.00E Fe 1.00E Voltage (V) Some samples had excess of high amplitude spurious pulses 37

38 Preliminary tests of photosensitive RETGEM manufactured by a screen printing technology 38

39 Experimental set up for studies RETGEM with CsI photocathodes manufactured by screen printing technology Hg lamp Monochromator Window Filter HV feedthrough Drift mesh -V dr Top RETGEM CsI V 1 top V 2 top Gas out Bottom RETGEM Gas in Charge sensitive amplifier 39

40 Hg lamp spectra, measured with TMAE (a) () detector and RETGEM () (b) TMAE QE vs. wavelength (c) a) c) SP-RETGEM b) C ounting rate (H z) Wavelength (nm) Gas gain 3x10 5 Q CsI =33%N CsI /N TMAE ~ 12.2% - for SP-RETGEM 40

41 Long-term stability SP-RETGEM QE (%) Time (days) 41

42 Can ~12-14% QE be sufficient for VHMPID? 1 C 5 F 12 transmittance CaF 2 transmittance mirror reflectivity 0.4 CsI quantum efficiency 12% 0.2 (40%-are holes) total convolution photon energy (ev) 185 nm Volpe talk at this Conference Yes, it looks O K OK 42

43 Preliminary comparison of K- RETGEMs with SP-RETGEMs In all gases tested K-RETGEMs allow to achieve at least 10 times higher gains than SP-RETGEMs Some samples of SP-RETGEM exhibit high amplitude spurious pulses (it is not the case for K-TGEMs!) Both detectors are spark-protected, however after 10 min of continuous glow discharge a low resistivity SP-RETGEM can be damage (it is not the case of K-RETGEM!)-the counting rate of spurious pulses increased Energy resolution in the case of SP-TGEM was worse Photosensitive K-RETGEMS and SP RETGEMS have almost the same QE at 185 nm: % at 185 nm -and these values remained stable at least in a month scale 43

44 Conclusions: RETGEM detectors are fully spark protected (the energy released in sparks is at least 100 times less than in the case of metallic TGEMs) At low rate they behave like GEM ( and the gas gain is stable with time) and at high rates and high gains RETGEMs are more resembling RPCs ( gain reduces with rate) Being coated by a CsI layer RETGEMs operate stable at high gains and low rates and their QE is % at 185nm Long term (few months) stability of RETGEMs with CsI pc was demonstrated We believe that RETGEMs can be good candidates for the VHPMID and some other RICH detectors 44

45 Future tasks: In contrast to K-TGEMs, the SP-RETGEMs require more tuning up: optimization its resistivity and geometry, understanding some detail in operation, tests in C 5 H 12 gas 5 12 g Final evaluation and conclusions can be drowned only after a beam test 45

46 Plans for future beam test Proto-4 Pad plain Should be manufactured 5 RETGEMs 40 mm New, exists 4 CsI Drift mesh Should be modified 3 Old, exist 2 Old, exist 1 Liquid radiator 46

47 The photodetectors to be tested : GEM TGEM RETGEM The beam test will allow to select the best one 47

48 Spairs

49 Wire chamber with CaF 2 window approach is not excluded yet!

50 Optimization of the RPC electrodes resistivity for high rate applications P. Fonte et al., NIM A413,1999,154

51 TMAE detector cross checks

52 Counting rate measurements from TMAE detector as function of radius Efficiency i scan ing rate H z) Count (H Distance from the center (mm)

53 Ionization chamber check (with a 185 nm filter)

54 Current measurements: Hg lamp Filter Window HV feedthrough Drift mesh A CsI -V Gas out RETGEM Gas in Charge sensitive amplifier

55 Ionization chamber check (with a 185 nm filter) Current (p pico A) TMAE detector RETGEM, Ne Voltage (V)

56 Backdiffusion

57 Ne Series1 Series2 Ar+25%CO2 my Kethley Series1 Series2 CO Series1 Series2

58 Active area r Π(1+3)r 2 /πr 2 = =0.25/0.64=40% R

59 Giacomo related slides

60 6th International Workshop on Ring Imaging gcherenkov Counters October, Trieste Gas Cherenkov detectors for high momentum charged particle identification in the ALICE experiment at LHC G. Volpe, D. Di Bari, E. Garcia, A. Di Mauro, E. Nappi, P. Martinengo, V. Peskov, G. Paic, K. A. Shileev, N. Smirnov A talk presented by G. Volpe yesterday

61 EMCal High energy γ TRD Electron ID, Tracking TPC Main Tracking, PID with de/dx ALICE experiment HMPID RICH, high p T pioni RICH ALICE is designed to study the physics of strongly interacting matter TOFand the quark- gluon plasma (QGP) in PID i t l di t collisions at the LHC. The p-p physics will be study as well as reference data for the nucleus-nucleus analysis. intermediate p T ITS Vertexing, low p t tracking and PID with de/dx MUON μ-id PHOS γ,π 0 -ID pioni i + L3 Magnet B= T T0,V0, PMD,FMD and ZDC Forward rapidity region

62 ALICE RICH How it was designed How it is looked just before the installation ALICE RICH is installed inside the magnet and is in a commissioning phase now. We are looking forward for the first physics results!

63 ~ 2m ALICE Club - May 2, 2005 Paolo Martinengo

64 Example of a single radiator threshold imaging Cherenkov A. Braem, C.W. Fabjan et al., NIM A409, 1998, 426

65 Another idea AeroGel, 10cm UV Mirror, spherical shape in ZY 50 cm Double sided read-out plane: planar detectors with CsI CF 4 gas CaF 2 Window 50 cm C 4 F 10 gas Z X Y R position: 500 cm. Bz: 0.5 T Particle track & UV photons Nikolai Smirnov, Yale University

66 Blob diameter for C 4 F 10, pad size = 0.8x0.8 cm 2 Diameter (cm) Pions Kaons 10 8 Protons Momentum (GeV/c)

67 VHMPID volumes

68

69

70 Radiator gas options: VHMPID CF 4 (n , γ th 31.6) has the drawback to produce scintillation photons (N ph 1200/MeV), that increase the background. C 4 F 10 (n , γ th 18.9) is no more commercially available. C 5 F 12 (n 1.002, γ th 15.84) has been chosen. Photon detector options: Pad-segmented CsI photocathode is combined with a MWPC with the same structure and characteristic of that used in the HMPID detector. The gas used is CH 4 4, the pads size is cm 2 (wire pitch 4.2 mm), and the single electron pulse height is of 34 ADC channels. The chamber is separated from the radiator by a CaF 2 window (4 mm of thickness). The other option for the photon detector could be a GEM-like detector combined with a CsI photocathode (higher gain, photons feedback suppression). (see G. Volpe talk at this Conference)

71 Study of the detector response for the focusing setup In the case of focusing setup the determination of emission Cherenkov angle is possible. Pattern recognition algorithm is needed to retrieve the emission angle. A back-tracing algorithm has been implemented to retrieve the Cherenkov emission angle. It calculates the angle starting from the photon hit point coordinates, on the photon detector. Radiator vessel Photodetector Charged particle Mirror (from G. Volpe talk at this Conference). 120 cm

72 ) Simulation results: Cherenkov angle angle(rad) π K Cherenkov angle ring p The points and the bars in the plot correspond to mean and RMS of a sample of 100 events, respectively Momentum (GeV/c) Momentum π < 2.5 GeV/c 2.5< Kp < 8 GeV/c p 2.5 < p < 8 GeV/c 8 < p < 15 GeV/c C 5 F Particle Id.? π K, p π, K 8 < p < 15 GeV/c 0 p from G. Volpe talk at this Conference 15 < p < 30 GeV/c 1 p