1 / 26

Thick GEM-like multipliers: a simple solution for large area UV-RICH detectors

Thick GEM-like multipliers: a simple solution for large area UV-RICH detectors R. Chechik, A. Breskin and C. Shalem Dept. of Particle Physics, The Weizmann Institute of Science, 76100 Rehovot, Israel. 30 years of “Hole-multiplication” history:.

marcel
Download Presentation

Thick GEM-like multipliers: a simple solution for large area UV-RICH detectors

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Thick GEM-like multipliers: a simple solution for large area UV-RICH detectors R. Chechik, A. Breskin and C. Shalem Dept. of Particle Physics, The Weizmann Institute of Science, 76100 Rehovot, Israel

  2. 30 years of “Hole-multiplication” history: •Breskin, Charpak NIM108(1973)427 discharge in glass capillaries •Lum et al. IEEE NS27(1980)157, Del Guerra et al. NIMA257(1987)609 Avalanches in holes •Bartol, Lemonnier et al. J.Phys.III France 6(1996)337 CAT •Sakurai et al. NIMA374(1996)341, Peskov et al. NIMA433(1999)492 Glass Capillary Plates •Sauli NIMA386(1997)531GEM •Ostling, Peskov et al, IEEE NS50(2003)809G-10 “Capillary plates”

  3. • 1-2 holes/mm2 • PCB tech. of etching + drilling • Simple and robust  • Sub-mm to mm spatial resolution • VTGEM~2KV (at atm. pressure) • 105 gain in single-TGEM, 107gain in double-TGEM • Fast (few ns)  • Low pressure (<1 Torr) gain 104  • 50 holes/mm2 • Microlithography + etching • High Spatial resolution (tens of microns) • VGEM~400V • >103 gain in single GEM • 106 gain in cascaded GEMs • Fast (ns) • Low pressure – gain~30 1mm Expanding the standard GEM… Standard GEM TGEM Geometry: similar to “Optimized GEM” [Peskov] But: etched rim

  4. Expanding the standard GEM ? • What scales up? • The GEM geometry • and what does not? • Electric fields • Electron diffusion • Electron transport • Gain • Timing properties • Rate capability • Ions transport -> it is a new device that has to be studied from scratch !

  5. The TGEMs: A TGEM costs ~4$ /unit. With minimum order of 400$  ~120 TGEMs. >10 times cheaper than standard GEM from CERN.

  6. 3cm Cu G-10 Various TGEMs studied at WIS Manufactured by standard PCB techniques of precise drilling in G-10 (+ other materials) and Cu etching. TypicalAtm.pressure geometry Low pressure geometry Hole diameter d=0.3mm Distance between holes a=0.7mm Thickness t=0.4mm Hole diameter d=1mm Distance between holes a=1.5mm Thickness t=1.6mm 0.1mm rim to prevent discharges Important for high gains! 0.1mm

  7. multiplication E~4 (KV/cm) Hole length E~25 (KV/cm) Electric field & e- transport calculations: Maxwell / Garfield • Field values on electrode surfaces • Field value inside the holes • Field direction->focusing into the holes • Dependence on the hole parameters  Operated at VTGEM~2KV

  8. Operation principle Multiplication inside holes -> reduces secondary effects Each hole acts as an individual multiplier Edrift ETGEM Etrans Garfield simulation of electron multiplication in Ar/CO2 (70:30)

  9. TGEM as a Photon detector • Considerations: • High field on the pc surface, to minimize back scattering. • 2. Good e- focusing into the holes, to maximize effective QE. • Low sensitivity for ionizing background radiation. • Solution: a reflective pc on top of the TGEM. • Slightly reversed Edrift(~50V/cm) • good photoelectron collection! • Low sensitivity to MIPS

  10. TGEM as a Photon detector (‘cont) 0.4mm thick 0.3mm holes 0.7mm pitch • For typical operation voltages: Surface field > 5kV/cm  • Full photoelectron extraction • High effective QE • TGEMs studied so far are • more optically transparent • than standard GEM. • Cu: 40-50% area

  11. Reflective pc Semitransparent pc PC PC GEM GEM i i • measured gain in current mode is an effective gain: • Effective gain = true gain in X efficiency to focus • the holes the e- into the holes. • QE in the detector is an effective QE: • Eff. QE = true QE X efficiency to X efficiency to • of the pc extract the ph.e. detect the ph.e. Effective gain and effective QE

  12. Single-TGEM: Gain Gain 104-105 Single-photon detection no photon feedback Rise time < 10ns Example: TGEMwith reflective CsI photocathode (Similar results with semitransparent pc) 105 10ns

  13. e- Etrans= 3kv/cm 5 mm Double-TGEM: Gain Example: TGEMwith a semitransparent CsI photocathode (similar results with reflective pc) • Important for double • TGEM: • high Etrans • Large transfer gap 107 • Higher total gain (106-107) • >103 higher gain at same VTGEM • Better stability

  14. Operation in CF4 • Problem: • Requires high TGEM voltage. • Damage due to sparks is fatal: after a spark the TGEM deteriorates continuously. (We suspect effects of etching to the SiO2 fibers). • Fatal spark damage was also observed in standard GEMs operating in CF4, due to the high operating voltages. • Solutions: • Segment the TGEM • Cascade several TGEMs. • Test other materials: Kevlar, Teflon, etc. R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico

  15. Compared to standard GEM, very high fields are reached at the TGEM surface already at low VTGEM .Good e- extraction in all gases. F f Transfer efficiency 0.4mm thick 0.3mm holes 0.7mm pitch Electron transfer efficiency TGEM with a reflective pc (Edrift=0)  eaffects energy resolution, detection efficiency, effective QE

  16. 0.4mm thick 0.3mm holes 0.7mm pitch Electron transfer efficiency TGEM with a semitransparent pc   is important also for double TGEM operation • (more complex measurement) • Double-sided pc • Double normalization • Single e- pulse counting as before Full efficiency already at low gains gains 10-100 !

  17. ETGEM/Edrfit > 1 e- focused to hole ETGEM/Edrfit < 1 e- collected on GEM top Electron transfer efficiency  -cont’TGEM with a semitransparent pc - dependence on Edrift/VTGEM With typical TGEM operation voltage: full eff. up to Edrift = 4kv/cm 0.4mm thick 0.3mm holes 0.7mm pitch

  18. FWHM=~20% Energy resolution: 6 keV x-rays 6 keV x-rays E resolution similar to standard GEM

  19. Counting rate capability • Reflective CsI pc • UV photons (185nm) 0.4mm thick 0.3mm holes 0.7mm pitch Total current limit 4*10-7 [Amp/mm2]

  20. s.t. pc Ion back flow Affects pc longevity and secondary effectsTGEM with a semitransparent pc IBF = ipc/iTGEM 0.4mm thick 0.3mm holes 0.7mm pitch 12% Start amplification With high VTGEM most of the ions are collected on the top of the TGEM.

  21. Reflective pc Ion back flow Affects pc longevity and secondary effects TGEM with a reflective pc IBF = ipc/iTGEM With a reflective photocathode, most of the ions are collected on the top of the TGEM (like in a GEM).

  22. Summary • G-10 TGEMs tested with several gases. • Gains:105with a single TGEM; 107 with cascaded double TGEM • Fast signals: r.t. <10 ns. • The e- transfer efficiency (into the holes) is well understood. • Counting rate capability: ~ 106avalnches/sec x mm2@ gain 4x104 • Ion backflow: study in course • In TPC-like conditions: IBF with a single TGEM is 12%. • In GPM/reflective pc:IBF with a single TGEM is 98%. • A cascade + other “tricks” (see GEM/MHSP) should reduce IBF . • 8. TGEMs of different materials (e.g. Kevlar, Teflon…) for CF4 ?. • 9. Will study TGEM of lower optical transparency (higher eff. QE)

  23. The end

  24. TGEM: Low pressure operation • low pressure isobutane • semi-transparent CsI photocathode Single TGEM 10 Torr Isobutane Gain~105; Rise time~5ns

  25. TGEM: Low pressure operation • low pressure isobutane • semi-transparent CsI photocathode

  26. Electron transfer efficiencythe efficiency to focus an electron into the TGEM • Pulse counting measurement: • A way to separate the true gain from the effective gain. • Based on single e- pulses • same pc, lamp, gain and electronics, different e- path. • Comparing counting rate provides the fraction of single e events • reaching TGEM bottom. (1) normalization (2) efficiency measurment Example: ref pc

More Related