New spark-protected GEMlike detectors with resistive electrodes

Transcription

1 New spark-protected GEMlike detectors with resistive electrodes V. Peskov Behalf of ALICE HMPID, ICARUS research group and TS/DEM/PMT Workshop CERN

2 The talk today will be about breakthrough in developments of GEM-like detectors

3 GEM-gas electron multiplier It belongs to a new generation of gaseous detectors called micropattern gaseous detectors

4 The main designs of micropattern gaseous detectors μm Microstrip gaseous detectors μm Microdot gaseous detectors 25μm 140μm MICROMEGAS GEM

5 Gas Electron Multiplier (GEM) 70 µm 140 µm F. Sauli, NIM A386,1997, µm

6 The main feature is that the multiplication occurs not near the strips and tips or in parallel gap as in other micropattern detector (as well as in classical detectorswire type and parallel plate type) but in holes Avalanche _ + Field lines focusing effect V/cm

7 Electrostatic lens in electronic optics + Electrons _

8 There were earlier attempts to exploit a filed line focusing effect in holes for gas multiplication

9 Capillary plates MCP A. Del Guerra et al.,nim A , 609

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11 Avalanche multiplication in capillary plate Primary electrons Field focusing effect A. Del Guerra et al.,nim A , 609

12 Avalanche multiplication in capillary plate Field focusing effect A. Del Guerra et al.,nim A , 609

13 Avalanche multiplication in capillary plate Gas gain Avalanche A. Del Guerra et al.,nim A , 609

14 CAT- Compteur a trou F. Bartol et al., J. Phys IIII. 6,1996,337

15 Field lines focusing effect Gas gain Avalanche F. Bartol et al., J. Phys IIII. 6,1996,337

16 Another good ideas from M. Lemonier GEM Cylindrical hole-type structure M. Lemonier, Patent ,1994

17 Microchannel plates Avalanche Hamamatsu capillary plate. These MCP operate not in a vacuum, but in a gas atmosphere Sakurai et al., NIM, A374, 1996, 341

18 Gas gain of MCPs

19 GEM - F. Sauli, NIM A386, 1997, cm Compass Totem NA49-future

20 Gas avalanches in GEM:

21 Features of hole-type detectors: Can operate noble gases. Can be combined with other devices of the same kind to operate in a cascade mode. Avalanche Avalanche Geometrical shielding of the avalanche light Cascaded mode

22 DISCHARGE STUDIES WITH MULTI-GEM DETECTORS Systematic measurement confirm that in multiple GEM structures higher gains can be sustained before discharges in presence of heavily ionizing background. Both gain and sustainable gain are increased by about one order of magnitude at each addition of a GEM. The discharge probability depends on the experiment-dependent source of background, and has to be verified in realistic running conditions. For systematic studies in the laboratory, the gain is measured with soft X-rays sources or X-ray generators, while the heavily ionizing background is emulated with an 241Am alpha source; very convenient also the use of an alpha emitter, Radon 220 (generated by natural Thorium), introduced in the gas flow

23 The main problem comes from the fact that the capacitance of the GEM is large and as a results the sparks in GEM could be as violent as in PPAC with metallic electrodes

24 R Energy of sparks Cu V GEM Current restriction resistors R Maximum energy: E=V 2 C/2 C~ε/d V Cu PPAC In reality the spark energy depends also on a gas and electrode s material

25 Discharge Protection Circuit Protection Circuit APV VFAT APV chip COMPASS TOTEM L. Ropelewski, Report at Vienne Conference, February, 2007

26 Multi-GEM Detectors Discharge Probability on Exposure to 5 MeV Alphas Multiple structures provide equal gain at lower voltage. Discharge probability on exposure to α particles is strongly reduced. S. Bachmann et al Nucl. Instr. and Meth. A479(2002)294 Raether limits increases in the case of the cascaded GEM L. Ropelewski, Report at Vienne Conference, February, 2007

27 Measures to minimize the destruction by sparking: current restriction resistors, power suppliers with fast current cut, segmentation, cascaded GEM, spark protected front- end electronics

28 Reasons for sparking Raethrer limit: An o > electrons. Sharp edges and imperfections. Surface streamers.

29 GEM Foil Defects Helsinki TOTEM Group L. Ropelewski, Report at Vienne Conference, February, 2007

30 Reasons for sparking Raethrer limit: An o > electrons. Sharp edges and imperfections. Surface streamers.

31 Raether limit for micropattern gaseous detectors The Raether limit increases with the GEM thickness V. Peskov et al., IEEE Nucl. Sci. 48,2001,1070

32 Thick GEM-like multipliers: THGEM L. Periale at al., NIM,A478,2002,377; J. Ostling et al.,ieee Nicl Sci.,50,2003,809 Manufactured by standard PCB techniques of precise drilling in G-10 (+other materials) and Cu etching. ECONOMIC & ROBUST! Hole diameter d= mm Dist. Bet. holes a= mm Plate thickness t= mm A small THGEM costs ~3$ /unit. With minimum order of 400$ ~120 THGEMs. ~10 times cheaper than standard GEM. TGEM was further developed by Breskin group : R. Chechik et al. NIM A535, 2004,

33 Thick GEM-TGEM GEM TGEM 2 mm thick J. Ostling et al., IEEE Nucl. Sci., 50, 2003, 809

34 Resistive Electrode GEM- RETGEM

35 High resistivity layer Holes +V -V Dielectric - Resistive Electrode GEM-RETGEM +

36 RETGEM E=V 2 c/2 c~ε/d; c<c RPC

37 CNC drilling Glue PCB a) mm Cu foil Resistive kapton 50 μm b) Contact wires Diameter of holes: mm, pitch mm Active area 30x30 and 70x70 mm 2 Important feature: for the first time the resistive electrodes have not any metallic substrate Surface resistivity kω/ (100XC10E5)

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41 Hg lamp Radioactive source PMs for monitoring discharges Window A RETGEMs GEMs Charge- sensitive or current amplifiers

42 Ne, 1 atm Gain 1.00E E E E E E E-01 GEM Voltage (V) RETGEM, 1mm

43 Ar, 1 atm Gain 1.00E E E E E E+00 GEM Voltage (V) RETGEM, 1mm

44 Ar+CO 2 Gain 1.00E E E E E E+00 GEM RETGEM, 1mm Voltage (V)

45 Energy resolution of ~33% FWHM was achieved for uncollimated 55 Fe at gains of At higher gains the detector may lose the proportionality and sometimes even works in Geiger mode

46 Measurements of relative energies of sparks

47 Measurements relative sparks energies with a current to voltage converter Metallic TGEM 1mm thick, 100 Ω feedback resistor Conclusions: 1) In Ar spark current in kapton RETGEM is almost 1000 times less 2) In kapton RETGEM initial sparks / streamers with further increase of the voltage may transit to glow discharge 3) Either sparks or streamers damage the detector or electronics Kapton RETGEM 1 mm thick, I kω feedback resistor

48 Signals from PM detecting light from sparks The best CrO coated TGEM (presented at ALICE Club in 2006) Regular res. kapton RETGEM

49 A photo of a continuous discharge in RETGEM In several cases, we initiated continuous glow discharges in the RETGEM for a total duration of 10 minutes. After the discharge was stopped (by reducing the voltage on the detector s electrodes), the RETGEMs continued to operate without any change in their characteristics, including that of the maximum achievable gain.

50 Double RETGEMs

51 Gains of single (solid symbols) and double (open symbols) kapton RETGEMs Kapton RETGEM 0. 4 mm thick 1.00E+08 Gain 1.00E E E E+00 Ne Ar Ar+CO Holes 0.3 mm in diameter on a 0.7 mm pitch. Voltage (V) Kapton RETGEM 1 mm thick Gain 1.00E E E+02 Ne A Ar+CO Holes 0.8 mm in diameter with a 1.2 mm pitch Voltage (V) With double RETGEMs Raether limit for macroscopic detectors was reached : An 0 ~10 8 electrons

52 0.4 mm thick RETGEN can be easily bended as requers for some application, for example NA for some Photos of bended GEM for NA49 Future

53 Photosensitive RETGEMs

54 For the first time the resistive coating was covered by CsI photocathode (reflective photocathode) Window Drift mesh CsI Double RETGEMs The CsI quantum efficiency was as high as in the case of metallic substrate (~30% at 120 nm)

55 Gain 1.00E E E E E+02 Ar Ne Ar+CO Voltage (V) High gains were achieved with RETGEM coated with a CsI layer

56 Rate characteristics Pulse amplitude (mv) E E E E E+08 Rate (Hz/cm 2 ) Open symbols-tgem Filled symbols-retgem Stars -discharges

57 With rate RETGEMs behave as RPCs or MWPCs and can replace these detectors in some applications

58 Optimization of the RPC electrodes resistivity P. Fonte et al., NIM A413,1999,154

59 RETGEM may compete with GEM in many applications that do not require very fine position resolution Possible applications: Muon detection Calorimetry RICH

60 Possible application of LEM in classical RICH CsI Radiator The main idea: to replace wire chamber by RETGEM Drift mesh ΔV +V Advantages: simpler design, possibility to be insensitive to charge particles (at ΔV=0) New idea: radiator and the detector are placed in the same gas volume CF 4 or Ar Advantages: simpler design, More light, possibility to be insensitive to charge particles (at ΔV=0) Gas chamber Mesh CsI

61 Exotic applications RETGEM RETGEN can operate not only in pure noble gases, but also in air containing mixtures. This may open new fields of applications

62 Three examples of possible exotic applications

63 Flame detection

64 Detector of flames and sparks sealed single-wire UV counter with CsI photocathodes Developed in collaboration between CERN and Oxford Instr. Detects small flames from matches or cigarette lighter on a distance of >30m in fully illuminated rooms. Orders of magnitude more sensitive than commercially available UV flame detectors. E.g more sensitive than Hamamatsu gas-r2868 flame detector. GAIN in Ar/10%CO 2 :~ with CsI photocathode L. Periale et al., NIM, A572,207,189 V. Peskov, Report at ALICE Club, 2006

65 Next generation of the flame detector? (developments in progress)

66 Hg lamp Window Drift mesh A CsI V top TGEM A

67 Ar Current (na) Voltage (V) Air Current (na) Voltage (V) Sparks in air very violent, so only with RETGEM one can afford a safe operation in air

68 UV flame detector prototype Pulsed D 2 lamp Drift mesh Cascaded RETGEM Readout electronics

69 Gains of CsI coated single and double RETGEMs in air Gain 1.00E E E Voltage on the bottom RETGEM

70 Preliminary results: double RETGEM with a CsI coating is 10 time more sensitive than commercial UV sensor, for example Hamamatsu UVtron R2868 Long term stability still should be demonstrated!

71 Dosimetry?

72 Gas vessel Alpha source Ar -Vdr 4 cm Alpha tracks -V1 -V2 Double RETGEMs

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74 Efficiency close to 95% was achieved in air in this geometry Alpha source Air -Vdr 4 cm Alpha tracks -V1 -V2 Double RETGEMs

75 Efficiency close to 90% was achieved in air in this geometry Alpha source -Vdr 4 cm Alpha tracks 2 cm -V1 -V2 Our G-10 detectors +V

76 Dangerous gases detection

77 Commercial photoionization detector Sensitivity: up to 100 ppb Gases: benzene, tolyene and others

78 Photoionization detectors are very cheap and are widely used in practice

79 Drift electrode Photoelectrons UV lamp G-10 detectors A Gas chamber Townsend avalanches Preliminary results: sensitivity 100 times higher than with commercial detectors was achieved for some gases

80 Conclusions: We have developed and successfully tested GEM-like detectors with resistive electrodes Resistive electrodes make detectors spark- protected and thus very robust and reliable in operation We discovered that resistive kapton used in these studies being coated with photosensitive layers, such as CsI, can be used as efficient photocathodes for detectors operating in a pulse counting mode. Arising from our results, we believe that GEMs with resistive electrodes will open new avenues in future developments and applications.

81 Spairs

82 T. Francke et al., NIM A508, 2003,83 Sparks quenching region

83 Hg lamp Radioactive source PMs for monitoring discharges Window A RETGEMs CsI GEMs Charge- sensitive or current amplifiers

84 Alpha source 1MΩ -V Alpha tracks 4 cm 1MΩ 10MΩ 2-5 mm 15 MΩ Resistive electrode hole-type detectors +V 1MΩ 5MΩ

85 A possible design of the detector for Po monitoring Surface containing Po 2-3 cm -Vdr 4 cm Alpha tracks from Po -V1 -V2 Shielding box +V Our G-10 detectors

86 December 19, 2006 The New York Times OP-ED CONTRIBUTOR The Smoky Bomb Threat By PETER D. ZIMMERMAN

87 Primary electron Entering a hole type structure -V The light from the avalanche cannot reach the cathode and thus do not create secondary electrons a) b) +V Electric field Avalanche c) d) Electrons from avalanches Ions remaining in the hole after the avalanche Move to the cathode They charge up the cathode, the electric field inside the hole drops and secondary electrons, even if appear do not cause secondary avalanches

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89 Lens Window Drift electrode Photoelectrons RETGEMs Gas chamber Readout plate Strips Amplifiers

90 Lens Window Drift electrode Photoelectrons G-10 detectors Gas chamber Readout plate Strips Amplifiers

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