C.D.R. Azevedo, M. Cortesi, A.V. Lyashenko, A. Breskin, R. Chechik, J. Miyamoto, V. Peskov, J. Escada, J.F.C.A. Veloso and J.M.F. dos Santos

Physics Department – University of Aveiro

Physics Department – University of Coimbra

Weizmann Institute of Science

Photoelectron extraction and collection efficiency studies in CsI-THGEM for Ne based mixtures

Motivation

• THGEM in Ne mixtures• High gain @ low voltages

reduced discharge probability discharge energy charging-up effects

• Single photoelectron detection capability• Collection and extraction efficiency• Effective photon detection efficiency

Gain

0 200 400 600 800 1000 120010-2

10-1

100

101

102

103

104

105

106

107

E

ffect

ive

Gai

n

VTHGEM

(V)

Ne/5% CF4 Ne/10% CF4 Ne/5% CH4 Ne/10% CH4 Ne/23% CH4

Single THGEM (t = 0.4 mm, d = 0.3 mm, a = 0.7 mm, h = 0.1 mm)

Atm. pressureGas flow mode

Extraction efficiency (εextr)

vac

gasextr I

I

0 2 4 6 8 10 120.4

0.8

1.2

1.6

2.0

2.4

2.8

Ivac Igas(Ne/10% CF4)

I(nA

)

EDrift

(kV/cm)

Extraction efficiency (εextr)

0.0 0.5 1.0 1.5 2.0 2.5 3.00.4

0.5

0.6

0.7

0.8

0.9

1.0Atm. pressureGas flow mode

E

xtra

ctio

n ef

ficie

ncy

EDrift

(kV/cm)

CH4 CF4 Ne/10% CF4 Ne/5% CF4 Ne/10% CH4 Ne/5% CH4 Ar/5% CH4

Photocathode Electric Field

-0.3 -0.2 -0.1 0.0 0.1 0.2 0.30

1

2

3

4

5E

lect

ric F

iled

(kV

/cm

)

Distance from center between holes (mm)

VTHGEM

= 500 V V

THGEM = 700 V

VTHGEM

= 900 V

Collection efficiency (εcoll)

Collection efficiency (εcoll)

ref

THGEMcoll N

N

0 5 10 15 20 25 30 35 40100

101

102

103

104

105

Cou

nts

Channel

ROI

Reference detector

Investigated detector

Collection efficiency (εcoll)

200 300 400 500 600 700 800 900 10000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2Atm. pressureGas flow mode

Single THGEM (t = 0.4 mm, d = 0.3 mm, a = 0.7 mm, h = 0.1 mm)

C

olle

ctio

n ef

ficie

ncy

VTHGEM

(V)

G=220 G=25 G=103 G=210 G=103

Ne/5% CF4 Ne/5% CH4 Ne/10% CF4 Ne/10% CH4 Ne/23% CH4

Effective photon detection efficiency (εeffph)collextreffeffph AQE

Gas ∆VTHGEM(V) Gain QE 170nm Aeff εextr εcoll Εeffph

Ne/CH4(95/5) 800 5.4E4 0.3 0.54 0.73 1 0.12

Ne/CH4(90/10) 900 1.3E5 0.3 0.54 0.79 1 0.13

Ne/CF4(95/5) 750 6.0E5 0.3 0.54 0.76 1 0.12

Ne/CF4(90/10) 850 1.2E6 0.3 0.54 0.83 1 0.14

Gas ∆VTHGEM(V) Gain QE170nm Aeff εextr εcoll Εeffph

Ne/CH4(95/5) 800 5.4E4 0.3 0.91 0.73 1 0.20

Ne/CH4(90/10) 900 1.3E5 0.3 0.91 0.79 1 0.22

Ne/CF4(95/5) 750 6.0E5 0.3 0.91 0.76 1 0.21

Ne/CF4(90/10) 850 1.2E6 0.3 0.91 0.83 1 0.23

This geometry: t = 0.4 mm, a = 0.7 mm, d = 0.3 mm, h = 0.1 mm

Perspectives for optimized geometry: t = 0.4 mm, a = 1 mm, d = 0.3 mm, h = 0.01 mm

Conclusions Gain > 105 were reached in all mixtures

106 in Ne/10%CF4

Extraction efficiency (εextr) > 72% @ 1.5 kV/cm83% @ 2 kV/cm in Ne/10%CF4

Full collection efficiency (εcoll) @ realistic operation conditions Effective photon detection efficiency 12 < εeffph < 14%

20% < εeffph < 23% with optimized geometry83% @ 2 kV/cm in Ne/10%CF4

Thanks for your attention

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