Recent THGEM investigations Recent THGEM investigations A. Breskin, - PowerPoint PPT Presentation

Recent THGEM investigations Recent THGEM investigations A. Breskin, V. Peskov, J. Miyamoto, A. Breskin, V. Peskov, J. Miyamoto, M. Cortesi, S. Cohen, R. Chechik Weizmann Institute Weizmann Institute - Gain: UV vs. X-rays G i UV X - Gain stability - What’s next? - What s next? THGEM cooperation also with: Coimbra, PTB, Soreq NRC, Milano univ, UTA… THGEM Recent review w refs: BRESKIN et al http://dx.doi.org/10.1016/j.nima.2008.08.062 RD51 Paris Oct 08

Among current applications: 2-phase LXe detectors 2 phase LXe detectors Medical: LXe Gamma camera Medical: LXe Gamma camera for rare events Also: Calorimetry LXe Gas photomultipliers N-detectors photons n elemental radiography Pos-sens n-dosimetry - BNCT Gy/h mm mm

THGEM Thick Gas Electron Multiplier (THGEM) THGEM 1 e - in 0.5mm holes E E holes drilled in thick G-10 10 4 - 10 5 e - s out SIMPLE, ROBUST, LARGE-AREA Double-THGEM: 10-100 higher gains � Intensive R&D � Many applications Robust Single-photon sensitivity Effective single-photon detection Effective single-photon detection 8ns RMS time resolution Sub-mm position resolution >MHz/mm2 rate capability >MHz/mm2 rate capability Cryogenic operation: OK

Gain: UV vs X-rays To clarify: “are WIS previous results of “higher gain with UV compared to x-rays” - OK? to x-rays - OK? Method: compare both UV and x rays with the Method: compare both UV and x-rays with the same detector in a single experiment

Single- & double-THGEM with UV (recall) Shalem et al NIM A558(2006)475 0.8mm thick 0.4mm thick 10 4 10 4 10 4 10 4 - Gain 2-THGEM / 1-THGEM ~100 - Gain 2-THGEM: function of E trans - 2-THGEM: lower V hole - 1-THGEM: low thickness-effect on gain: gain0.8mm/gain0.4mm ~2

Double-THGEM with 6 keV x-rays (recall) 10 4 Cortesi et al 2007 JINST 2 P09002

New measurements: Experimental set up pA Gas in pA TGEM -Vtop CsI To pump Am Gas out (for gain calibration) 2cm Mesh -Vdr Window THGEM geometry: Holes dia: 0.5 mm UV light Pitch: 1 mm 55Fe 55Fe Thickness: 0.8 mm Rim: 0.1mm Hg lamp

Single-THGEM : Ar+5%CH 4 g 4 Ar+5%CH4=1atm 1.00E+06 1.00E+04 10 4 UV WIS old Current-mode Current-mode UV light UV light pulse-mode l d Gain 1.00E+02 NEW X-rays 55 Fe NEW Pulse-mode 1.00E+00 ( (~1kHz) ) 0 0 500 500 1000 1000 1500 1500 2000 2000 2500 2500 1.00E-02 THGEM geometry: Voltage (V) Holes dia: 0.5 mm Pitch: 1 mm Pitch: 1 mm Thickness: 0.8 mm Rim: 0.1mm Cu X-ray gun, current-mode Cu X ray gun, current mode Maximal gains with UV are 100 times higher than with X-rays. For UV and x-ray gun: The current in the plateau region (500-750V) was the same: 0 1nA The current in the plateau region (500-750V) was the same: 0.1nA. The maximum current in gain measurements was always kept below 0.5nA

Single-THGEM: Ne Gain in Ne=1atm Gain in Ne=1atm 1.00E+07 1.00E+06 1.00E 06 1.00E+05 Fe old 10 4 UV, 1.00E+04 10 4 UV light (prtection current-mode 1.00E+03 box) box) Gain 1.00E+02 Fe new 55 Fe 1.00E+01 (no protection box) Pulse-mode 1.00E+00 550 THGEM geometry: 1.00E-01 50 150 250 350 450 1.00E-02 Holes dia: 0.5 mm 1.00E-03 Pitch: 1 mm Thi k Thickness: 0.8 mm 0 8 Voltage (V) Rim: 0.1mm The maximum gains with x-rays in Ne are higher than in Ar+5%CH 4 The maximum gains with x rays in Ne are higher than in Ar+5%CH 4 . In Ne breakdown voltages with UV and X-rays are closer.

Single-THGEM: Ne + CH 4 Gains in Ne+5%CH4 Gains in Ne+5%CH4 1.00E+06 1.00E+05 10 4 10 4 1.00E+04 1 00E+04 10 4 10 4 UV 55Fe Fe 1.00E+03 Gain Current-mode UV Pulse-mode 1.00E+02 1.00E+01 1 00E+00 1.00E+00 THGEM geometry: 0 200 400 600 800 1000 1200 1.00E-01 Holes dia: 0.5 mm Voltage (V) Pitch: 1 mm N +23%CH4 Ne+23%CH4 Thickness: 0.8 mm Rim: 0.1mm 1.00E+06 1.00E+05 UV UV 10 4 10 4 1 00E 04 1.00E+04 55Fe 10 4 Fe 1.00E+03 Current-mode Pulse-mode Gain 1.00E+02 1.00E+01 1.00E+00 0 500 1000 1500 2000 2500 1.00E-01 Voltage (V) S Same as with Ne: maximum gains with x-rays in Ne+CH 4 are higher C than in Ar+5%CH 4 and breakdown voltages with UV and X-rays are close.

A possible interpretation (Peskov) p p ( ) - Raether limit: established in large-gap avalanche detectors but valid for MPGDs (Ivanchenkov NIM A 1999), though may be different ( ) g y - A*n 0 =10 6 -10 7 electrons where A is the maximum achievable gain, n0-number of primary electrons deposited by the radiation in the drift region � X-rays: different gain compared to UV - In Ne/CH 4 Raether limit possibly differs from Ar/CH 4 due to ~ 5-fold In Ne/CH Raether limit possibly differs from Ar/CH due to ~ 5 fold longer range of 55 Fe photoelectrons (~1mm), resulting in lower ioinization density per “hole”. To verify with alphas, hadronic beams etc y p ,

GAIN STABILITY GAIN STABILITY

THGEM Long-term stability: recall R. Chechik SNIC2006, http://www.slac.stanford.edu/econf/C0604032/papers/0025.PDF Double THGEM 6 10 S ST PC PC 1mm 2x1500V ( increase 50 V only ) [3] 5 10 n Gain 2x1450V ( change by +100 -50V only ) [2] i 4 10 10 4 3 10 Insulator Charging up � 2x1400V i 0 =1pA [1] Hole&rim:few hours of stabilization Ar/5%CH4 (gain variation ~ factor 2 ) (gain variation factor 2.) 2 2 10 10 0 5 10 15 20 25 Stabilization time function of: hours • Total gain (potentials) otal ga n (potent als) UV, 5x10 5 e-/mm 2 • Counting rate (current) • Material & hole-geometry (dia., rim ) • Production method • Gas & purity (e.g. moisture)

Stability with UV: new data Single-THGEM geometry: geometry: Ar/5%CH Ar/5%CH 4 – flow mode flow mode Holes dia: 0.5 mm Charge-up: gain dependent Pitch: 1 mm Thickness: 0.8 mm Rim: 0.1mm Stability test measured with UV light during 3 Stabilty test in Ar+5%CH4=1atm with UV at days at gain 1000 in Ar 5%CH4 1atm days at gain 1000 in Ar+5%CH4=1atm gain 1 gain=1 0.5 Day1 0.4 Day Day3 nt (nA) 0.2 0.3 (nA) 0.15 0 1 0.1 Current ( 0.2 Curre 0.05 Night1 Nignt Light close Light close 0 0.1 0 50 100 150 200 0 Time (min) 0 20 40 60 Time (hours) Time (hours) Stabilty measured with UV in Stability studies at gain 10000 , UV light, 1atm Ar+5%CH4=1 atm at gain=10 Ar+CH4. In three occasions the light was blocked blocked 0.6 0 6 1.5 0.4 urrent (nA) rent (nA) Day1 1 Day2 0.2 0.5 Night 0 0 Curr Cu -0.2 0 10 20 30 40 50 -0.5 0 50 100 150 200 Times (hours) Time (min)

THGEM GAIN STABILITY – X-RAYS Vary the distance Mesh HGEM HGEM To change the rate esh Drift me 2nd TH 1 st TH Anode Fe-55 source collimated Fe 55 source collimated by a 3 mm dia hole 9.6 mm 1.6 mm 1.6 mm THGEM geometry M t Material FR-4 i l FR 4 E d ift E_drift = 100 V/cm 100 V/ Thickness 0.4 mm E_transfer 1 kV/cm Hole size 0.6 mm E_inducion= 4 kV/cm Pitch Pitch 1.0 mm 1 0 mm Rim size 0.1 mm

SETUP Heated Baraton Gauge Pure argon gas in for pressure monitoring for pressure monitoring (4Torr change in 24h) UHV vessel UHV vessel ThGEM Temperature sensor placed on th the chamber surface (0.8C in 48h) h b f Hamamatsu PMT for photon counting counting Collimated X-rays Anode Gas can: signal - Flow - Circulate via getter Gas out RGA 200 gas analyzer for purity check Charge Amp+Shaper+MCA for pulse height analysis for pulse height analysis Gain corrected for pressure-changes; T-changes negligible

GAIN VARIATION vs RATE I • For a very short-term scales (<1 hr) the drop in gain is faster for higher rates For a very short-term scales (<1 hr), the drop in gain is faster for higher rates • The magnitude of drop function of rate C harge up measurement for different rates (7, 30, 120, 300 Hz/mm2) 1 hour scale Sept 21 Vent Weak=7 Hz/mm2 Sept 21, Vent, Weak 7 Hz/mm2 Sept 22, Vent, Weak ~ 30 Hz/mm2 2200 Sept 23, Vent, Slightly strong ~ 120 Hz/mm2 7Hz/mm 2 Gain 2000 Gain 2000 Sept 24, Vent, Strong ~ 300 Hz/mm2 p , , g 2000 2000 1800 30Hz/mm 2 Gain 1600 G 1400 120Hz/mm 2 1200 300Hz/mm 2 1000 0 0.2 0.4 0.6 0.8 1 X-RAYS Tim e (hr) Argon, 770 Torr g ,

GAIN VARIATION vs RATE II Stability reached after ~ 5h for gains ~1400 for 7-300Hz/mm 2 C harge up measurement for different rates (7, 30, 120, 300 Hz/mm2) 10 hour scale Sept 21, Vent, Weak 7 Hz/mm2 Sept 21 Vent Weak=7 Hz/mm2 Sept 22, Vent, Weak ~ 30 Hz/mm2 2200 Sept 23, Vent, Slightly strong ~ 120 Hz/mm2 7Hz/mm 2 Gain 2000 Gain 2000 2000 000 Sept 24, Vent, Strong ~ 300 Hz/mm2 p g 1800 Data normalized to pressure=770 Torr Gain 1600 G 1400 1200 300Hz/mm 2 1000 0 2 4 6 8 10 Tim e (hr) X-RAYS Argon, 770 Torr g ,

GAIN VARIATION vs RATE – higher gain vs rate 1. At higher rate, after initial drop, the gain keeps rising while at lower rate the gain g p g p g g stabilizes at low value. 2. At higher rate the detector occasionally discharges, whereas at lower rate the detector is rather stable 3 3. Gain recovery after a discharge is faster at higher rates. Gain recovery after a discharge is faster at higher rates High Gain ~10,000, High (170 Hz/mm2) and Low (7 Hz/mm2) Rates 12000 Oct 2, High Rate (~ 170 Hz/mm2), HV=1290V Gain 10 000 Gain 10,000 10000 At high rate Oct 3, Low rate (~ 7 Hz/mm2), HV=1260V 8000 continuous sparks begin when Gain 6000 G the gain recovered th i d 4000 sufficiently 2000 0 0 2 4 6 8 10 12 14 Time (hr) Spark followed by slow Sparks followed by quick recovery (high rate) recovery (low rate)