THGEM short results collectionDecember 2008 @ CERN

Gabriele Giacomini, Jarda Polak, Elena Rocco

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How to read this summary:

Since Jarda already presented all data about the photocurrent meas. during the GDD meeting 32, the latest preliminary and partial results are here reported.

In the next slide you’ll see the setup use for the three different measurements and then the most representative results.

REMARK: some of them should be understood and/or redone.

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Same setup, several & different purposes

Gas mixer

Avantes – UV lamp

picoammeters

55Fe

Double THGEM C7

Leszek’s chamber Dummy/dummy

Quartz window of the double THGEM chamber (type C7)

Oriel Lamp

Three positions of the shutter: 1.completly open, 2.closed (some internal reflections),3.Open + filter 3.0 OD

N2 inlet

Hidden N2 exhaust

Setup for photocurrent measurements and optimization of performance for the double

THGEM structure with the iron source

Setu

p fo

r U

V li

ght

mea

s. w

ith

the

doub

le T

HG

EM s

truc

ture

Filter 0.5 OD

Narrow Filter

Filter 3.0 OD

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Iron Source: drift scan ΔV1= Δ V2=1.36 kV

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0-350

-300

-250

-200

-150

-100

-50

0

50

100

150

200

250

V1=1.36 kV, V2=1.36 kV, E induction=3 kV/ cm, E drift=0.67 kV/ cm;Atm pressure Ar/ CO2 70/ 30; source 55Fe big collimator.

Curr

ent (

pA)

Drift field (kV/ cm)

Anode Current Bottom 2 Current Top 2 Current Bottom 1 Current Drift Current Top 1 projection Current

THGEM: C7d=0.4 mmpitch =0.8 mmt=0.4 mmrim=0.01 mm

drift = wires

THGEM 2THGEM 1

anode

d=4.5 mmd=1.6 mmd=1.6 mm

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Light: drift scans with ΔV=1kV & ΔV=0.9 kV

-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8

-680

-660

-640

-620

-600

-580

-560

-540

-520

-500

-480V=1 kV, atm pressure Ar/ CO2 70/ 30; Oriel + 0.5 OD+ narrow filter

Curr

ent (

pA)

Drift Field (kV/ cm)

V=1 kV V=0.9 kV

THGEM: C7d=0.4 mmpitch =0.8 mmt=0.4 mmrim=0.01 mm

drift = wires

THGEM 2THGEM 1

anode

d=4.5 mmd=1.6 mmd=1.6 mm

-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6

-420

-400

-380

-360

-340

-320

-300Atmospheric pressure; Oriel lamp narrow filter + 3 OD;Ar/ CO2 70/ 30; double THGEM (C7 type).

Anod

ic C

urre

nt (

pA)

Drift Field (V)

Anodic current

High voltage applied to the THGEMs gain

Measurement to be redone!

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Light: drift scan measurementTHGEM: C7d=0.4 mmpitch =0.8 mmt=0.4 mmrim=0.01 mm

drift = wires

THGEM 2THGEM 1

anode

d=4.5 mmd=1.6 mmd=1.6 mm

0 1000 2000 3000 4000 5000 6000

0

200

400

600

800

1000

1200

The measurements labelled "dummy" and "wires" havebeen performed with the Avantes lamp in the Leszek'schamber flushing the gas through, while the "double"consists in the double THGEM with the a depositof CsI on the top of the THGEM closer to the cathodeand performed with the Oriel lamp, always flushing the gas.The electrical configuration too is the samesince that the top and the bottom THGEM are connectedand read out togheter by the Kethley. Cu

rren

t on

CsI (

pA)

V (V)

double dummy wires

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Light: delta V scan (½)

0 200 400 600 800 1000 1200-200

0

200

400

600

800

1000

1200

1400

1600 0 Drift Field; double THGEM (type C7) used as a single structure;Oriel lamp + 0.5 OD + narrow filter;Atm pressure Ar/ CO2 70/ 30.

Curr

ent (

pA)

V (V)

Transfer field = 160V Transfer field = 480V

THGEM: C7d=0.4 mmpitch =0.8 mmt=0.4 mmrim=0.01 mm

drift = wires

THGEM 2THGEM 1

anode

d=4.5 mmd=1.6 mmd=1.6 mm

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Light: Delta V scan (2/2)

0 200 400 600 800 1000 1200-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

5000

0 Drift Field; E induction=3 kV/ cm; double THGEM (type C7) used as a single structure; Oriel lamp + 0.5 OD + narrow filter; atm pressure Ar/ CO2 70/ 30.

Curr

ent (

pA)

V (V)

Anodic Current Bottom 1 Current Top 1 Current Drift Current

0 200 400 600 800 1000 1200

-1500

-1000

-500

0

500

1000

1500

2000

2500

0 Drift Field; E induction=3 kV/ cm; double THGEM (type C7) used as a single structure; Oriel lamp + 0.5 OD + narrow filter; atm pressure Ar/ CO2 70/ 30.

Curr

ent (

pA)

V (V)

Anodic Current Bottom 1 Current Top 1 Current Drift Current

THGEM: C7d=0.4 mmpitch =0.8 mmt=0.4 mmrim=0.01 mm

drift = wires

THGEM 2THGEM 1

anode

d=4.5 mmd=1.6 mmd=1.6 mm

All currents monitored!!!The sum of the total currents is not zero. There’s some systematic , but the behaviour should be not affected since the larger deviation is for higher current so for the highest field.

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Single photon spectrumTHGEM: C7d=0.4 mmpitch =0.8 mmt=0.4 mmrim=0.01 mm

drift = wires

THGEM 2THGEM 1

anode

d=4.5 mmd=1.6 mmd=1.6 mm

200 400 600 800 1000 1200 1400 1600

0

1000

2000

3000Data: CK122_BModel: Exp2PMod1 Chi^2/DoF = 1461.68412R^2 = 0.99289 a 2793.52937 ±9.03815b -0.00231 ±6.9399E-6

Coun

ts

ADC channels

Energy Spectrum

Exponential fit! With the

assumption to be in the single photon, the estimated rate from the current is 40 kHz!!!

Shutter closed!!!internal reflections.