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 G i UV X

• Gain: UV vs. X-rays
• Gain stability
• What’s next?
• What s next?

THGEM Recent review w refs: BRESKIN et al THGEM cooperation also with: Coimbra, PTB, Soreq NRC, Milano univ, UTA… RD51 Paris Oct 08 http://dx.doi.org/10.1016/j.nima.2008.08.062

Among current applications:

Medical: LXe Gamma camera 2-phase LXe detectors Medical: LXe Gamma camera 2 phase LXe detectors for rare events LXe Also: Calorimetry photons N-detectors n elemental radiography Gas photomultipliers

Gy/h

Pos-sens n-dosimetry - BNCT

mm mm

THGEM

Thick Gas Electron Multiplier (THGEM)

1e- in THGEM 0.5mm holes

E

holes drilled in thick G-10 104- 105e-s out

E

SIMPLE, ROBUST, LARGE-AREA Intensive R&D Double-THGEM: 10-100 higher gains 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

104 104

0.4mm thick

104 104

• Gain 2-THGEM / 1-THGEM ~100
• Gain 2-THGEM: function of Etrans
• 2-THGEM: lower Vhole
• 1-THGEM: low thickness-effect on gain:

gain0.8mm/gain0.4mm ~2

Double-THGEM with 6 keV x-rays (recall)

104 Cortesi et al 2007 JINST 2 P09002

New measurements: Experimental set up

pA pA Gas in TGEM

• Vtop

CsI Am

(for gain calibration)

2cm To pump Gas out

• Vdr

Mesh Window 55Fe UV light

THGEM geometry: Holes dia: 0.5 mm Pitch: 1 mm

Hg lamp 55Fe

Thickness: 0.8 mm Rim: 0.1mm

Single-THGEM : Ar+5%CH4

Ar+5%CH4=1atm

g

4

1.00E+04 1.00E+06 UV light

WIS old l d

UV Current-mode

104

1.00E+00 1.00E+02 500 1000 1500 2000 2500 Gain UV light X-rays

55Fe NEW

Pulse-mode (~1kHz)

pulse-mode

Current-mode NEW

1.00E-02 500 1000 1500 2000 2500 Voltage (V)

( )

THGEM geometry: Holes dia: 0.5 mm Pitch: 1 mm

Cu X-ray gun, current-mode

Pitch: 1 mm Thickness: 0.8 mm Rim: 0.1mm 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

Cu X ray gun, current mode

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+06 1.00E+07 1.00E+03 1.00E+04 1.00E+05 1.00E 06 UV light Fe old (prtection box)

UV, current-mode 104 104

1.00E+00 1.00E+01 1.00E+02 Gain box) Fe new (no protection box)

55Fe

Pulse-mode

1.00E-03 1.00E-02 1.00E-01 50 150 250 350 450 550 THGEM geometry:

Holes dia: 0.5 mm Pitch: 1 mm Thi k 0 8

Voltage (V)

The maximum gains with x-rays in Ne are higher than in Ar+5%CH4

Thickness: 0.8 mm Rim: 0.1mm

The maximum gains with x rays in Ne are higher than in Ar+5%CH4. In Ne breakdown voltages with UV and X-rays are closer.

Single-THGEM: Ne + CH4

Gains in Ne+5%CH4 Gains in Ne+5%CH4

1 00E+04 1.00E+05 1.00E+06

104

104

1 00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04 Gain UV Fe

55Fe Pulse-mode UV Current-mode

104

104

1.00E-01 1.00E+00 200 400 600 800 1000 1200 Voltage (V)

N +23%CH4

THGEM geometry: Holes dia: 0.5 mm Pitch: 1 mm

Ne+23%CH4

1 00E 04 1.00E+05 1.00E+06

UV Thickness: 0.8 mm Rim: 0.1mm

104

1.00E+01 1.00E+02 1.00E+03 1.00E+04 Gain Fe

55Fe Pulse-mode UV Current-mode

104

104

1.00E-01 1.00E+00 500 1000 1500 2000 2500 Voltage (V)

S C Same as with Ne: maximum gains with x-rays in Ne+CH4 are higher than in Ar+5%CH4 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*n0=106-107 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 Raether limit possibly differs from Ar/CH due to ~ 5 fold

• In Ne/CH4 Raether limit possibly differs from Ar/CH4 due to ~ 5-fold

longer range of 55Fe 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

ST PC

1mm

10

6

Double THGEM

S PC

10

5

2x1500V (increase 50 V only) [3]

n

i 10

4

2x1450V (change by +100 -50V only) [2]

Gain

104

Insulator Charging up Hole&rim:few hours of stabilization (gain variation ~ factor 2 )

10

2

10

3

2x1400V i0=1pA [1]

Ar/5%CH4

(gain variation factor 2.) Stabilization time function of:

• Total gain (potentials)

5 10 15 20 25

10

2

hours

• tal ga n (potent als)
• Counting rate (current)
• Material & hole-geometry (dia., rim)
• Production method

UV, 5x105 e-/mm2

• Gas & purity (e.g. moisture)

Stability with UV: new data

Single-THGEM geometry: Ar/5%CH flow mode geometry: Holes dia: 0.5 mm Pitch: 1 mm Thickness: 0.8 mm Charge-up: gain dependent Ar/5%CH4 – flow mode

Stability test measured with UV light during 3 days at gain 1000 in Ar+5%CH4=1atm

Rim: 0.1mm

Stabilty test in Ar+5%CH4=1atm with UV at gain 1 0.3 0.4 0.5

(nA)

days at gain 1000 in Ar 5%CH4 1atm Day1 Day Day3

0 1 0.15 0.2 nt (nA)

gain=1 0.1 0.2 20 40 60

Current ( Time (hours)

Night1 Nignt

0.05 0.1 50 100 150 200 Curre Time (min)

Light close Light close

Time (hours)

0 6

Stability studies at gain 10000, UV light, 1atm Ar+CH4. In three occasions the light was blocked

Stabilty measured with UV in Ar+5%CH4=1 atm at gain=10

0.2 0.4 0.6 rent (nA)

blocked

Day1 Night Day2 0.5 1 1.5 urrent (nA)

• 0.2 0

10 20 30 40 50 Curr Times (hours)

• 0.5 0

50 100 150 200 Time (min) Cu

THGEM GAIN STABILITY – X-RAYS

Mesh HGEM HGEM esh Vary the distance To change the rate Fe-55 source collimated Anode 2nd TH 1st TH Drift me Fe 55 source collimated by a 3 mm dia hole

9.6 mm 1.6 mm 1.6 mm

THGEM geometry M t i l FR 4 E d ift 100 V/ Material FR-4 Thickness 0.4 mm Hole size 0.6 mm Pitch 1 0 mm E_drift = 100 V/cm E_transfer 1 kV/cm E_inducion= 4 kV/cm Pitch 1.0 mm Rim size 0.1 mm

SETUP

Pure argon gas in Heated Baraton Gauge for pressure monitoring for pressure monitoring

(4Torr change in 24h)

UHV vessel ThGEM Temperature sensor placed on th h b f UHV vessel the chamber surface (0.8C in 48h) Hamamatsu PMT for photon counting Collimated X-rays counting

Anode signal

Gas can:

• Flow

Gas out

• Circulate via getter

Charge Amp+Shaper+MCA for pulse height analysis RGA 200 gas analyzer for purity check for pulse height analysis Gain corrected for pressure-changes; T-changes negligible

• For a very short-term scales (<1 hr) the drop in gain is faster for higher rates

GAIN VARIATION vs RATE I

For a very short-term scales (<1 hr), the drop in gain is faster for higher rates

• The magnitude of drop function of rate

Charge up measurement for different rates (7, 30, 120, 300

Hz/mm2) 1 hour scale

Sept 21 Vent Weak=7 Hz/mm2

2000 2200

Sept 21, Vent, Weak 7 Hz/mm2 Sept 22, Vent, Weak ~ 30 Hz/mm2 Sept 23, Vent, Slightly strong ~ 120 Hz/mm2 Sept 24, Vent, Strong ~ 300 Hz/mm2

7Hz/mm2

Gain 2000

1600 1800 2000

Gain p , , g

30Hz/mm2

Gain 2000

1200 1400

G

120Hz/mm2 300Hz/mm2 1000 0.2 0.4 0.6 0.8 1

Tim e (hr)

Argon, 770 Torr X-RAYS g ,

GAIN VARIATION vs RATE II

Stability reached after ~ 5h for gains ~1400 for 7-300Hz/mm2

Charge up measurement for different rates (7, 30, 120, 300

Hz/mm2) 10 hour scale

Sept 21 Vent Weak=7 Hz/mm2

2000 2200

Sept 21, Vent, Weak 7 Hz/mm2 Sept 22, Vent, Weak ~ 30 Hz/mm2 Sept 23, Vent, Slightly strong ~ 120 Hz/mm2 Sept 24, Vent, Strong ~ 300 Hz/mm2

Gain 2000

7Hz/mm2

1600 1800 000

Gain p g

Data normalized to pressure=770 Torr Gain 2000

1200 1400

G

300Hz/mm2

1000 2 4 6 8 10

Tim e (hr)

X-RAYS Argon, 770 Torr g ,

1. At higher rate, after initial drop, the gain keeps rising while at lower rate the gain

GAIN VARIATION vs RATE – higher gain vs rate

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 Gain recovery after a discharge is faster at higher rates

• 3. Gain recovery after a discharge is faster at higher rates.

High Gain ~10,000, High (170 Hz/mm2) and Low (7 Hz/mm2) Rates

10000 12000 Oct 2, High Rate (~ 170 Hz/mm2), HV=1290V

Gain 10 000

6000 8000

Gain

Oct 3, Low rate (~ 7 Hz/mm2), HV=1260V

At high rate continuous sparks begin when th i d Gain 10,000

2000 4000

G

the gain recovered sufficiently

2 4 6 8 10 12 14

Time (hr)

Sparks followed by quick recovery (high rate) Spark followed by slow recovery (low rate)

Lower gain: rates 7 Hz/mm2 & 70 Hz/mm2

GAIN VARIATION vs RATE – lower gain vs rate

g

• 1. At higher rate, the initial drop is shaper
• 2. At higher rate, after the sharp drop the gain tends to reach faster

the stability observed for the lower rate. the stability observed for the lower rate.

• 3. The stabilization time is longer for low gain & higher rates.

Low gain, High rate ~ 70 Hz/mm2, Low rate ~ 7 Hz/mm2

600 Oct5 Low rate (~ 7 Hz/mm2), 770 Torr 400 500

n

Oct 5 High rate ( ~ 70 Hz/mm2), 770 Torr

Gain 500

200 300

Gai

100 5 10 15 20

Time (hr)

Summary of charge up in pure Ar

• 1. At low rates: gain drops to a certain level and remains constant regardless of

initial gain (500-10,000)

• 2. At higher rates: gain sharply drops to its minimum. The magnitude of the drop

is the largest at high gain. After reaching minimum, the gain tends to recover to the value reached at low-rates The recovery is faster at the higher gains to the value reached at low-rates. The recovery is faster at the higher gains.

• 3. At high rate and high gain the gain recovery did not reach stable level –

discharges due probably Raether limit in Ar discharges due probably Raether limit in Ar.

GAIN STABILITY: rim/no-rim TRIESTE RESULTS

RIM: 0.1 mm

Long time GAIN variation

RIM: 0

Single THGEM, th. 0.4, Ø 0.4, p. 0.8 Single THGEM, th. 0.4, Ø 0.4, p. 0.8

Short time GAIN i ti

TRIESTE Results

variation

RIM: 0 RIM: 0.1 mm irradiation after ~10 hour at nominal voltage without irradiation irradiation at HV switch on ( ft 1 d ith irradiation

Remark: Comparison at diff gains

Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news (after ~1 day with no voltage)

Remark: Comparison at diff gains

Gain variation studies in different conditions

TRIESTE lt TRIESTE results

For first series of “Eltos” pieces (with th. 0.4, diam. 0.4, pitch 0.8), Ar/CO2 70/30 and 55Fe source (~ 600 Hz), in Trieste, first 12 h: 100 μm chem. rim increase of ~ 400%

?

• 50 μm mech. rim still to be processed: large decrease

25 μm chem. rim decrease of ~ 70%

?

10 μm chem. rim decrease of ~ 50% (“global etching”) no rim decrease of < 30% Th ti t h t bili ti i h t f ll i The time to reach stabilization is shorter for smaller rims CsI deposited on pieces with 100 μm rim and with no rim: gain variations with photons ~ similar to those seen with X rays gain variations with photons ~ similar to those seen with X rays

Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news

THGEM-GPM for LXe Gamma Camera

Subatech-Nantes/Weizmann THGEM CsI photocathode LXe conversion volume Segmented Anode MgF2 window

IN CONSTRUCTION LXe/GPM Tests: Jan 09

300x300mm2 THGEM! 300x300mm2 THGEM!

300x300 THGEM

THGEM geometry: Hole dia.: 0.5 mm Pitch: 1 mm Thickness: 0.4 mm (Cu~ 35 mic) Rim: 0.05 mm (can be smaller) Chemical etching/no mask Ni/Au plating Producer: Print Electronics www.print-e.co.il

SUMMARY

• In Ar+5%CH4 the maximum achievable gains measured with UV-light (~106)
• In Ar+5%CH4 the maximum achievable gains measured with UV light ( 10 )

are ~100-fold higher than with 55Fe (~104)

• Probable explanation is the Raether limit
• In Ne and Ne-CH4 (5-23%) mixtures, under gas flushing, the maximum gains

In Ne and Ne CH4 (5 23%) mixtures, under gas flushing, the maximum gains with UV and 55Fe are closer (105 - 106)

• Possible explanation: 55Fe photoelectron-tracks are longer in Ne and its

mixtures lower density of ionization per hole lower max. gain-difference y p g caused by charge-density effects.

• In pure Ne scintillation prevents high gains & “masks” p.e. extraction quencher
• For RICH: optimal would be Ne–based mixtures

Q f ff

• Quencher additives to be optimized – for high gain and efficient p.e. extraction.
• Preliminary results indicate upon ~70% extraction efficiency in Ne/23%CH4

similar to Ar/5%CH4.

• Charge-up: geometry (rim), gain and rate dependent.

g p g y ( ) g p

• It seems that rimless holes are advantageous, but need to establish detectors’

parameters (eff QE, e-transfer photon detection efficiency) with the right conditions and gas

• Need to compare stability of LARGE-AREA rim/rimless THGEMs with UV

p y photons

• Tests in RICH mode? Who? When? – Trieste ordered 60x60 cm THGEMs.
• 30x30cm THGEM tests: tested end 2008 at WIS
• Expected results in Cryo-THGEMs Gas Photomultipliers/LXe: early 2009.

Expected results in Cryo THGEMs Gas Photomultipliers/LXe: early 2009.