1. Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009 The THGEM: a THick robust Gaseous Electron Multiplier for radiation detectors A.Breskin, M. Cortesi, R. Alon, J. Miyamoto, V. Peskov, G.Bartesaghi, R. Chechik Weizmann Institute of Science, Rehovot, Israel V. Dangendorf PTB, Braunschweig, Germany J. Maia and J.M.F. dos Santos University of Coimbra, Portugal MOTIVATION: Robust, economic, large-area radiation imaging detectors FAST, HIGH-RATE, MODERATE LOCALIZATION RESOLUTION

2. Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009 THGEM – a family of hole gas multipliers: ECONOMIC & ROBUST ! Avalanche “confined” inside a hole in an insulating plate -> Reduced secondary effects, independent holes h=0.1 mm rim: prevents discharges  high gains ! Cu G-10 1mm Typical dimensions: Hole diameter d = 0.3 - 1mm Pitch a = 0.7- 7mm Thickness t = 0.4 - 3mm Manufactured by standard PCB techniques of precise drilling in G-10 (and other materials) and Cu etching. Other groups independently developed similar structures: Optimized GEM: L. Periale et al., NIM A478 (2002) 377. LEM: P. Jeanneret, PhD thesis, 2001. P.S.Barbeau et al, IEEE NS50 (2003) 1285. First publication: R.Chechik et al. NIM A535 (2004) 303 Recent review: A.Breskin et al. NIM A598 (2009) 107

3. Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009 THGEM – Operation principle (like GEM, similar voltages and fields) Advantages of large hole dimensions: Hole dimensions >> mean free path  High gains within the hole Hole dimensions >> e - diffusion  Easy electron transport into and out of the holes Efficient cascading of elements: 10-100 times higher gain E~40kV/cm Upon application of voltage across the plate (V=400-1200V function of gas and thickness): dipole field a dipole field in the holes focuses  focuses e - into the holes defocuses defocuses e - out the hole 1 e - in 10 4 - 10 5 e - out

4. Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009 THGEM – Operation principle Multiplication of e - induced by radiation in gas or from solid converters (e.g. a photocathode) Detector properties governed by: e - transport (e.g. efficiency to single e - ) multiplication charge induction on readout electrodes ion-backflow Reflective photocathode Semi- transparent photocathode focused e- focused into the holes by the hole dipole field

5. Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009 THGEM production methods No mask, Weizmann Drill + etch under the Cu Small and zero rim Surface damaged Cu RIM Cu Nice edge RIM With mask, Weizmann Etch w mask + drill Large rim displacement With mask, Eltos, Italy Drill +etch w mask Large rim No displacement Detached Cu CERN, Zero rim: drill + short etching to remove sharp edges from drilling.

6. Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009 3x3 cm: basic studies, many geometries 10x10 cm: 2D imaging 30x30 cm: n detector All produced with mask Rim=0.1mm The THGEMsat Weizmann The THGEMs at Weizmann 2003 2008

7. THGEM efficiency for single photoelectrons Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009 Hole dimensions >> e - diffusion  efficient transport from the conversion gap e - focused into the holes by the dipole field Full efficiency: at THGEM gain = 10-30 !! E drift = 1kV/cm V HOLE [Volt] Gain=100 Semitransparent photocathode e - extraction requires E drift >0.5kV/cm E drift =0 Reflective photocathode e - extraction optimal @ E drift =0kV/cm In GEM: 500-1000 Full efficiency: at THGEM gain = 30-100 !! Under study in Ne and Ne/CH 4 mixtures

8. Single THGEM gain x100 higher gain compared to single GEM Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009 Very high gain in 100% Ne and Ne mixtures At very low voltages !! 100% Ne: Gain 10 5 @ <500V Voltage increases w increased CH 4 % General: Gain limit (x-ray) << Gain limit (UV) (charge density!) in Ne mixtures on x3 lower (diffusion) 10 4 -10 5 10 5 -10 6 With single photoelectrons

9. Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009 double THGEM gain Hole dimensions >> e - diffusion  efficient transport in the transfer gap  efficient cascading of THGEMs  Much higher gain at lower voltages >10 6 Ar mixtures, single photoelectrons E trans =3kV/cm Very high gain even with x-ray At very low voltages !! 100% Ne: Gain 10 6 @ ~300V >10 6 E drift =0.2kV/cm E trans =3kV/cm Ne mixtures, x-rays Efficient cascading  Total gain = Gain1 x gain2

10. Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009 THGEM - rim effect and stabilization time From: Trieste group (RD51): larger rim -> longer stabilization time Old data : Chechik et al. Proceedings of SNIC2006, eConf C0604032, 0025 (2006) Larger rim  Insulator Charging up  few hours of stabilization gain variation ~ x2. Stabilization time depends on: voltages, currents, gas type and purity, materials, geometry, production method Rim=0.12mm Further R&D in progress @ CERN-RD51 gain = 10 4, UV light, e - flux ≈ 10 4 Hz/mm 2 Larger rim  higher voltages  Higher gains >10 4 THGEMs produced by chemical etching (no mask) @ PE, Israel Single THGEM, 6 keV x-rays

11. Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009 THGEM counting rate and pulses Rate capability = 10MHz/mm 2 @ GAIN ~10 4 Ar/CH 4 (1 atm) single photoelectrons Fast signals in atm. pressure Ar/30%CO 2 Double THGEM ( t=1.6 d=1, a=1.5 mm) gain=~10 6 rise time < 10 ns 9 keV x-rays 100% Ne ~X10 slower gas More CH 4  faster pulses, Higher voltages 75 ns 30 ns

12. Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009 THGEM timing (UV photons and  particles) Similar resolution with semitransparent PC Compatible with e - transport *Breskin et al NIM A483 (2002) 670 pulsed UV lamp Reflective CsI PC 0.3 mm 0.4 mm 0.7 mm MIPS Double-THGEM:  particles & cosmics:  =10-13 ns Triple-GEM (same setup):  7-9 ns Multi-GEM: 5-12 ns depending on gas -faster with Ar/CF 4 -slower with Ar/CO 2 mixtures) * UV photons

13. E Hole E Trans E Ind E Drift Induced-signal width matched to readout-pixel size. 8 keV X-Ray 10x10cm 2 THGEMs t=0.4, d=0.5, a=1 mm C-paint Resistive anode (match induced signal size) 2-sided pad-string readout 2mm pitch Delay-line readout (SMD) 2D imaging-detector w/economic readout Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009

14. Gain uniformity FWHM ± 10% 55 Fe Gain ~ 6x10 3 21% 1 mm pitch THGEM + 2 mm pitch Readout + DL interpolation --> 2D imaging: results with 6-8 keV x-ray Ar/CH 4 (95/5) Ar/CH 4 (95/5) Localization Resolution ~0.7 mm FWHM Mask: Raw Data 10 lp/cm From edge analysis

15. Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009 2D imaging: results with 5-9 keV x-ray Ne/5%CH 4 Ne/5%CH 4 preliminary x-rays < 5keV Flat-field illumination: hole pattern is visible/ Resolution ~0.3mm FWHM The THGEM electrode The 2D image

16. Recently numerous proposed solutions to charge and light detection in the gas phase of noble liquids “TWO-PHASE DETECTORS” Possible applications of noble liquids: - Noble liquid ionization calorimeters - Liquid argon TPC (solar neutrinos) - Scintillation detectors and two-phase emission detectors  exotic particles searches (WIMP …) - Development of γ -cameras for nuclear medicine imaging  e.g. PET, Compton… cathode WIMP Gas Liquid e-e- E Ar/Xe Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009 THGEM Operation in Noble gases: Ar, Xe for LARGE-VOLUME Noble-gas detectors for rare events and others. Advantages for THGEM vs. GEM: reduced effect of condensation on surfaces

17. Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009 THGEM Operation in Noble gases Avalanche confinement in holes is not not hermetic -> Field extends out by ~hole diameter -> Photon secondary effects might be important depending on geometry and gas. Avalanche & photons Outside the hole. Ne, Ar have energetic photons Need to optimize sizes and fields according to the gas. E

18. THGEM in Ar, Xe Ar/Xe =Penning mixt.  x20 higher gain, lower voltages. The lower gain in “purified” Ar  secondary effects due to “energetic” UV-photon feedback  Under investigations 6keV x-rays R. Alon et al. 2008_JINST_3_P01005 10 5 Not purified Purified gases Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009

19. THGEM in Xe,Ar/Xe R. Alon et al. 2008_JINST_3_P01005 THGEM: t=0.4mm, d=0.3mm, a=1mm, rim=0.1mmDouble-THGEM, t=0.4mm, d=0.5mm, a=0.9mm Ar/Xe (95/5) Penning mixture, Good energy resolution Gain > 10 4 Gain > 10 4 at all pressures Low voltages Xe Ar/Xe (95/5)

20. THGEM in liquid-Ar temperatures Stable operation in two-phase Ar, T=84K Double-THGEM Gains: 8x10 3 Experimental setup BINP/Weizmann: Bondar et al, 2008 JINST 3 P07001 2-THGEM G-10 1-THGEM G-10 2-THGEM KEVLAR 3-GEM GOOD PROSPECTS FOR CRYOGENIC-PHOTOMULTIPLIER OPERATION IN THE LXe-CAMERA

21. Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009 Radio-clean THGEM for rare-event physics Motivation: need charge and scintillation-light readout elements for noble-liquid detectors with very low natural radioactivity. E.g. Cirlex (a polyimide like Kapton) is 30 times radio-cleaner compared to PMT-glass Cirlex-THGEM preliminary tests: M. Gai et al. arXiv:0706.1106 The Cirlex-THGEM WIMP interaction LXe e-e- THGEM photon Detector Photon e-e- CsI Photo-Cathode EGEG ELEL The 2-phase THGEM LXe Dark-Matter detector concept (M.Gai-UCONN / D.McKinsey-YALE / A.Breskin-WEIZMANN)

22. THGEM Segmented Anode MgF 2 window LXe conversion volume CsI photocathode  THGEM-GPM for LXe Gamma Camera Subatech-Nantes/Weizmann Gas photomultiplier Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009

23. Photon detectors for RICH: reflective CsI PC deposited on the THGEM Photon detectors for RICH: reflective CsI PC deposited on the THGEM photoelectron extraction into gas, surface electric field by the hole dipole RICH RICH Requires: High field on the PC surface (for high QE). Good e - focusing into the holes (for high detection efficiency). Low sensitivity for MIPS background radiation (e.g. in RICH). Immediate interest: COMPASS & ALICE, R&D in RD51 efficient photoelectron extraction over the entire PC area: pitch 0.7mm, d=0.3mm: any voltage > 400V  any gas, including Ne, Ne/CH 4 pitch 1mm, d=0.5mm: similar results Distance = 0 Min. field Efficient Extraction From PC e-e- Ref PC

24. Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009 Maximum efficiency at E drift =0. Slightly reversed E drift (50-100V/cm) => good photoelectron collection & low sensitivity to MIPS (~5-10%) ! Relative Photon detectors for RICH: Photon detectors for RICH: reflective CsI PC deposited on the THGEM Photoelectron collection into the holes by the dipole field Currently R&D for upgrade of COMPASS & ALICE RICH Reduced sensitivity to MIPS proved with multi-GEM detectors of PHENIX e MIP E E E=0 E drift Ref. PC

25. New concept: Digital sampling calorimetry for ILC with A. White New concept: Digital sampling calorimetry for ILC with A. White Univ. Texas Arlington/Weizmann Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009 Sampling the jet + advanced pattern recognition algorithms -> Very high precision jet energy measurement. Simulated event with 2 hadronic jets Reconstructed jet: Simulated energy resolution General scheme of a detector HCal 2 sampling layers with THGEM-based elements

26. Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009 Fast-neutron Imaging-detector neutrons scatter on H in plastic-radiator foil, p escape the foil. p induce electrons in gaseous conversion gap. electrons are multiplied and localized in cascaded-THGEMs imaging detector. require high gain and large dynamic range (p spectrum) efficiency 1 layer: 0.1-0.2% High multiplication factors High stability w Ne mixtures: high gain and dynamic range. Weizmann/PTB/Soreq THGEM 1 THGEM 2 gas B, Li, Gd…converter: thermal neutron detector e.g. position sensitive n-dosimetry for BNCT (with Univ.& INFN, Milano) Double THGEMs:

27. Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009 Operation principle: n energy selected by TOF Image “on” ad “off” resonance Ratio of images => element selection Fast Neutron Resonant Radiography (FNRR) for element-resolved radiography Detector requirements area: >30x30 cm 2 detection eff. @ 2-10 MeV : ~ 5-10% Insensitivity to gamma counting rate : > MHz cm -2 Time Resolution ~ few ns Position resolution: ~ 0.5 mm THGEM will reduce cost 25-50 layers. => THGEM will reduce cost Weizmann/PTB/Soreq Dangendorf et al. NIM A542(2005)197 C rods Triple-GEM 10 x 10 cm 2 AllSteel C only Be target pulsed, white neutron beam Neutron imaging detector with fast timing capability ! nsec-pulsed broad energy deuteron beam neutron source: sample

28. Single-photon Single-photon imaging. e.g. Ring Imaging Cherenkov (RICH) detectors. Particle Fast Particle tracking at moderate (sub-mm) resolutions + high rates. Moderate-resolution TPC (Time Projection Chamber) readout elements. Sampling elements in calorimetry. Ionization & scintillation recording from Noble-Liquid & High-pressure detectors, including 2-phase detectors (Dark-Matter, neutrino, double-beta decay, Gamma Cam…) X-ray n Moderate-resolution (sub-mm), fast (ns) X-ray and n imaging. Possible low-pressure operation: Nuclear Physics applications Possible low-pressure operation: Nuclear Physics applications Summary Robust, economic, large-area radiation imaging detectors HIGH-GAIN, FAST, HIGH-RATE, MODERATE 2D- RESOLUTION Rachel Chechik Weizmann Institute TIIPP09 Tsukuba March 2009

29. Weizmann Group THGEM papers: R.Chechik et al. NIM A535 (2004) 303 (first idea) R.Chechik et al. NIM A553 (2005) 35 (application to photon detectors) C.Shalem et al. NIM A558 (2006) 475 & NIM A558 (2006) 468 (atm. And low-p) M.Cortesi et al. 2007_JINST_2_P09002 (imaging) M.Cortesi et al. NIM A572 (2007) 175 (2D imaging) R.Alon et al. 2008_JINST_3_P01005 (Ar, Xe) R.Alon et al. 2008 JINST 3 P11001 (timing) R.Chechik and A.Breskin NIM A595 (2008) 116 (application to photon detectors) A.Breskin et al. NIM A598 (2009) 107 (a concise review) R.Chechik,et al. /http://www.slac.stanford.edu/econf/C0604032/papers/ 0025.PDFS. (including long term stability) C. Shalem MSc 2005 JINST TH 001 R. Alon MSc 2008 JINST TH 001