Zerguerras T. – IPNO – RDD – 14/06/2013 RD51 Collaboration Meeting July, Zaragoza 5-6th 20131/12

New results on gas gain fluctuations in a Micromegas

detector

Unité mixte de recherche

CNRS-IN2P3Université Paris-Sud

91406 Orsay cedexTél. : +33 1 69 15 73 40Fax : +33 1 69 15 64 70http://ipnweb.in2p3.fr

T. Zerguerras, B. Genolini, M. Imré, M. Josselin, A. Maroni, T. Nguyen Trung, J. Pouthas, E. Rindel, P. Rosier, L. Séminor, D. Suzuki, C. Théneau

Zerguerras T. – IPNO – RDD – 14/06/2013 2/12 RD51 Collaboration Meeting , Zaragoza , 5-6th July 2013

A Laser test bench for MPGD study

- MPGD characterization with a point-like electron source ( <100 µm) of variable intensity produced by a 337nm UV laser.- Study performed with a prototype for the ACTAR (ACTive TARget) project

Laser

Conversion gap (1.6 mm)

Amplification gap (160 µm)

X Photon

Quartz lamina with a 0.5nm-thick Ni-Crlayer

Micromegas

Ni mesh

Anode

Micromegas

PMT

Laser optics

Optical fiber

Energy resolution

following the number of

primary electrons N0

a :laser intrinsic constant

Flas: N0 fluctuations from f and (f+Flas)

Single Electron Response Relative gain

variance :f = 0.30 ± 0.01

Gain= 6.0 104

0 e-

1 e-

1) 2)

Electronic: Gassiplex (2 000 e- rms)

T. Zerguerras et al., NIM A 608 (2009) 397

Ne 95% iC4H10 5%

Zerguerras T. – IPNO – RDD – 14/06/2013 3/12 RD51 Collaboration Meeting , Zaragoza , 5-6th July 2013

Improvements in 2013

Simplified geometry : - Complex anode pad plane geometry - Position of the 55Fe source

Lower noise level: - Lower limit of gain at ~ 3. 104 for SER measurements - Only for high-gain gas mixtures (ex: Ne:iC4H10 95:5)

Redesigned detector

Simplification of the anode plane segmentation

Change Front-End Electronics

Adapt the electronics chain

Lower pressure:

Pressure regulation and control system for studies at lowerpressure.

2009

2013

2009

2013

2013

Zerguerras T. – IPNO – RDD – 14/06/2013 4/12 RD51 Collaboration Meeting , Zaragoza , 5-6th July 2013

Detector improved

Conversion gap: 3,2mmAmplification gap: 160µm

Mesh: Buckbee Myers© 333 lpi nickel electroformed micromesh

5mm

10mm

Anode:3 pads

Change of the mechanics and simplification of the anode pad plane geometry

Improvement of electronics S/N ratio

Cremat CR-110 PAC

Gain: 1.4V/pCNoise : 200 e- RMS (table) 380 e- RMS (detector)

+CAEN N568B

Spectroscopy Amplifier(CG, FG fixed, SH=3µs, PZ fixed, Offset fixed)

Pressure control system

Calibration through a high-precision 1pF capacitance at the channel test-input

Zerguerras T. – IPNO – RDD – 14/06/2013 5/12 RD51 Collaboration Meeting , Zaragoza , 5-6th July 2013

Measurement with a 55Fe source

Ar 95% iC4H10 5%, 750 torrs,Vd= 738V Vmesh = 450V, CG 5 FWHM @5.9keV: 21%

Ne 95% iC4H10 5%, 750 torrs,Vd= 718V Vmesh = 430V, CG 2

FWHM @5.9keV: 14%

Zerguerras T. – IPNO – RDD – 14/06/2013 6/12 RD51 Collaboration Meeting , Zaragoza , 5-6th July 2013

Method for Single-Electron Response (SER) measurement

- The laser is focused on the drift electrode in front of the central pad

- A light-attenuator of factor 100 is put at the output of the laser box.

- Trigger: XP2282B anode signal

- Proportion of non-zero events (outside pedestal) is < 5%

- The anode charge is measured to monitor the laser light intensity(variation < 4%)

- The CG of the N568B Spectroscopy Amplifier is adjusted depending on the mesh voltage, all the other parameters being fixed

- The drift field is of 900V/cm

- Gas mixtures: Ar 95% iC4H10 5%, Ne 95% iC4H10 5%, He 95% iC4H10 5% @ 750 torrs

- To avoid any damage on the CR-110 chips, the maximum voltage applied on the mesh was 10V below the sparking limit voltage

Zerguerras T. – IPNO – RDD – 14/06/2013 7/12 RD51 Collaboration Meeting , Zaragoza , 5-6th July 2013

Single-Electron Response

Gain < 104

G = 5.5 103

q = 0.8 ± 0.1f = 0.56 ± 0.03

Ar 95% iC4H10 5%, Vmesh =450V, CG 7

G = 5.4 103

q = 2.0 ± 0.1f = 0.33 ± 0.01

Ne 95% iC4H10 5%, Vmesh= 390V, CG 6

He 95% iC4H10 5%, Vmesh = 420V, CG 7

G = 5.7 103

q = 1.7 ± 0.3f = 0.37 ± 0.03

Gain: GRelative gain variance: f =1/1+q

Sum of a Polya distribution:

and a Gaussian (pedestal) fitted on data

Zerguerras T. – IPNO – RDD – 14/06/2013 8/12 RD51 Collaboration Meeting , Zaragoza , 5-6th July 2013

Single-Electron Response

104 < Gain < 105 G = 5.9 104

q = 2.0 ± 0.1f = 0.33 ± 0.01

Ne 95% iC4H10 5%, Vmesh = 470V, CG 4 Ar 95% iC4H10 5%, Vmesh = 490V, CG 6

G = 2.0 104

q = 0.7 ± 0.1f = 0.59 ± 0.03

Polya distribution fittedon data

Gain: GRelative gain variance: f =1/1+q G = 5.3 104

q = 1.9 ± 0.2f = 0.34 ± 0.02

He 95% iC4H10 5%, Vmesh = 500V, CG 4

Maximum achievable gain before sparking

Zerguerras T. – IPNO – RDD – 14/06/2013 9/12 RD51 Collaboration Meeting , Zaragoza , 5-6th July 2013

Single-Electron Response

Gain > 105

G = 2.6 105

q = 1.7 ± 0.1f = 0.37 ± 0.01

Ne 95% iC4H10 5%, Vmesh= 520V, CG 2

G = 2.1 105

q = 1.6 ± 0.2f = 0.38 ± 0.03

He 95% iC4H10 5%, Vmesh= 550V, CG 2

Maximum achievable gain for both gas mixtures.

Zerguerras T. – IPNO – RDD – 14/06/2013 10/12 RD51 Collaboration Meeting , Zaragoza , 5-6th July 2013

Gain comparison

The maximum achievable gain is 10 times higher in Ne 95% iC4H10 5% than in Ar 95% iC4H10 5% .

For a given mesh voltage, the gain is about 7 (resp. 2) times higher in Ne 95% iC4H10 5% than in Ar 95% iC4H10 5% (resp. He 95% iC4H10 5% ).

Zerguerras T. – IPNO – RDD – 14/06/2013 11/12 RD51 Collaboration Meeting , Zaragoza , 5-6th July 2013

Relative gain variances

- In the measurement range, the relative gain variance f is rather independent of the gain.- For the same gain value, f is almost twice higher in Ar 95% iC4H10 5% than in the two other mixtures.- As a consequence of their higher ionization yields, lighter gases have a lower value of f (H. Schindler, S.F. Biagi and R. Veenhof, NIM A 624 (2010) 78-84).- In the present study, gas mixtures with lower relative gain variance have higher sparking limits.

Lower limit of 2009 study: ~ 3.7 104

Zerguerras T. – IPNO – RDD – 14/06/2013 12/12 RD51 Collaboration Meeting , Zaragoza , 5-6th July 2013

Conclusions

After the test-bench improvements, Single-Electron Response (SER) can be measured down to gains of ~ 5.103

Relative gain variances of three binary gas mixtures (Ar, Ne, He + 5% iC4H10 @ 750 torrs ) are deduced from the SER of a Micromegas detector.

For a given gain, the relative gain variance is almost twice higher in the Ar-based mixture

The maximum achievable gain in the Ar-based mixture (~2. 104) is ten times lower than in the Ne and He-based mixtures

Comparisons with calculations are needed (discussion with WG4) and could helpquantifying Penning effect in the three tested mixtures.

Other parameters are worth of interest for further measurements: nature and proportion of quencher, pressure, type of mesh, amplification gap thickness …

Zerguerras T. – IPNO – RDD – 14/06/2013 13/12 RD51 Collaboration Meeting , Zaragoza , 5-6th July 2013

Backup Slides

Zerguerras T. – IPNO – RDD – 14/06/2013 14/12 RD51 Collaboration Meeting , Zaragoza , 5-6th July 2013

Relative gain variance calculations

H. Schindler, S.F. Biagi and R. Veenhof, NIM A 624 (2010) 78.

Zerguerras T. – IPNO – RDD – 14/06/2013 15/12 RD51 Collaboration Meeting , Zaragoza , 5-6th July 2013

Ionization yield calculations for pure rare gases

H. Schindler, S.F. Biagi and R. Veenhof, NIM A 624 (2010) 78.

Zerguerras T. – IPNO – RDD – 14/06/2013 16/12 RD51 Collaboration Meeting , Zaragoza , 5-6th July 2013

Neon

Electron scattering cross-sections

Argon

H. Schindler, S.F. Biagi and R. Veenhof, NIM A 624 (2010) 78.

Zerguerras T. – IPNO – RDD – 14/06/2013 17/12 RD51 Collaboration Meeting , Zaragoza , 5-6th July 2013

Log(G)= d/l x exp(-Ie/ l Eamp)

Ne 95% iC4H10 5% : l = 4.22 +/- 0.03 µm Ie = 15.3 +/- 0.1 eV

Pure Neon: Ie = 21.6eV

Ar 95% iC4H10 5% : l = 3.24 +/- 0.15 µm Ie = 16.0 +/- 1.2 eV

Pure Ar: Ie = 15.8eV

d: amplification gap: l electron mean-free path:

Ie: energy ionisation thresholdEamp: amplification field

following F.J. Iguaz et al., 2012 JINST 7 P04007

He 95% iC4H10 5% : l = 4.16 +/- 0.04 µm Ie = 16.4 +/- 0.3 eV

Pure Helium: Ie = 24.6eV

Rose-Korff parameterisation

Zerguerras T. – IPNO – RDD – 14/06/2013 18/12 RD51 Collaboration Meeting , Zaragoza , 5-6th July 2013

Photon-absorption cross-sections

O. Sahin et al., 2010 JINST 5 P05002

Zerguerras T. – IPNO – RDD – 14/06/2013 19/12 RD51 Collaboration Meeting , Zaragoza , 5-6th July 2013

Measurements @ different CG values

G = 7.7 104

q = 2.3 ± 0.1f = 0.30 ± 0.01

Ne 95% iC4H10 5%, Vmesh= 480V, 750 torrs

CG 2 CG 3

G = 7.3 104

q = 2.2 ± 0.1f = 0.31 ± 0.01

CG 4G = 7.7 104

q = 2.0 ± 0.1f = 0.33 ± 0.01

CG 5G = 8.1 104

q = 2.2 ± 0.1f = 0.31 ± 0.01

Zerguerras T. – IPNO – RDD – 14/06/2013 20/12 RD51 Collaboration Meeting , Zaragoza , 5-6th July 2013

A pulse signal is injected on the test input of the central pad (Pad_C) through a 1pF capacitance

0 200 400 600 800 1000 1200 1400 1600 1800 20000

200400600800

100012001400

f(x) = 0.689982218839184 xR² = 0.999990785296003

Pad_C calibration: CG 2, FG 0, SH 2, PZ 66, Offset 120

Pad_C calibration

ADC-Ped (ch)

Q (

fC)

0 200 400 600 800 1000 1200 1400 1600 1800 20000

100200300400500600700

f(x) = 0.340938807924509 xR² = 0.999997614348142

Pad_C calibration: CG 3, FG 0, SH 2, PZ 66, Offset 120

Pad_C calibration Linear (Pad_C calibration)

ADC-Ped (ch)

Q (

fC)

0 200 400 600 800 1000 1200 1400 1600 1800 20000

50100150200250300350

f(x) = 0.174515347907191 xR² = 0.999999224255887

Pad_C calibration: CG 4, FG 0, SH 2, PZ 66, Offset 120

Pad_C calibration

ADC-Ped (ch)

Q (

fC)

Electronic chain calibration

Zerguerras T. – IPNO – RDD – 14/06/2013 21/12 RD51 Collaboration Meeting , Zaragoza , 5-6th July 2013

Electronic chain calibration

0 200 400 600 800 1000 1200 1400 1600 1800 20000

50

100

150

200

f(x) = 0.0904585213902026 xR² = 0.999995480388914

Pad_C calibration: CG 5, FG 0, SH 2, PZ 66, Offset 120

Pad_C calibration

ADC-Ped (ch)

Q (

fC)

0 500 1000 1500 2000 25000

20

40

60

80

100

f(x) = 0.0416294400431916 xR² = 0.99998228429958

Channel Pad_C Calib : CG 6, FG 0, SH 2 (3µs) , PZ 66, Offset 120

Channel Pad_C Calib : CG 6, FG 0, SH 2 (3µs) , PZ 66, Offset 120Linear (Channel Pad_C Calib : CG 6, FG 0, SH 2 (3µs) , PZ 66, Offset 120)

ADC-Ped (ch)

Q (f

C)

0 200 400 600 800 1000 1200 1400 1600 1800 20000

10

20

30

40

50

f(x) = 0.0214649663674108 xR² = 0.999993483118898

Channel Pad_C Calib : CG 7, FG 0, SH 2 (3µs) , PZ 66, Offset 120

Channel Pad_C Calib : CG 7, FG 0, SH 2 (3µs) , PZ 66, Offset 120Linear (Channel Pad_C Calib : CG 7, FG 0, SH 2 (3µs) , PZ 66, Offset 120)

ADC-Ped (ch)

Q (f

C)