high pressure electroluminescent tpc studies @ ciemat/ifae

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High Pressure Electroluminescent TPC studies

@ CIEMAT/IFAE

Roberto SantorelliOn behalf of

I. Gil-Botella, E. Calvo, S. Jimenez Cabre, C. Palomares, A. Verdugo (CIEMAT-MADRID)

O. Ballester, A. Garica-Soto, J. Illa, A. Lostao-Viñolas, T.Lux, F. Sanchez (IFAE-Barcelona)

Advances in Neutrino Technology 2013, May 9-12 Lake Tahoe

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• Electroluminescence (EL) detectors have a wide range of applications

• Several gas TPCs (both Ar and Xe researches) have been developed in a joint R&D activity by CIEMAT (Madrid) and IFAE (Barcelona)

(Ar and Xe scintillation studies…)

• Main research line: medium size (110x200 mm) High-Pressure Gas Xe TPC with 25 APDs

• Combined energy resolution and tracking studies

General concept

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Example I: simple setup for QE studies (GXe)

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241Am

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EL signal

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Example II: small EL-TPC for spectroscopy studies (GAr)

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VIS1 VIS2

UV1

UV2

VUV1

VUV

UV

VIS

IR

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EPL, 91 (2010) 62002

GArLAr

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Va=1.5 kV , Vk=0 Va=2.5 kV , Vk=0

Va=3.0 kV , Vk=0 Va=3.0 kV , Vk=3.0 kV

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EL signals

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• Excellent performances of the gas TPCs in respect of energy resolution have been proved

• Limited knowledge about their tracking capabilities on larger scale

• Study of an APD readout for EL detectors

• Goal: Good energy resolution and investigation of possible tracking capabilities at the same time

Main R&D activity

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Experimental Setup

HP TPC (30 cm long, 30 diameter)

Preamp, ADC, APD power supply

Xenon recovery system

PMT power supply

HV power supplies (20 and 35 kV)

Cosmic ray trigger

Getter

Vacuum pump system

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“CIFA” chamber

7 mm

200 mm

110 mm

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Readout array

Array of 5x5 S8664-SPL APDs from Hamamatsu (5x5 mm2) powered independently

Pitch 15 mm 2 PMTs for t0 measurements 3 custom made preamp/shaper boards V1740 CAEN ADC for digitization DAQ based on Midas

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Previous Studies

Small HP chamber with 5 APDs All APDs at the same voltage Allowed to develop readout electronics Excellent energy resolution achieved

(8.2 ± 0.1)% FWHMxenon

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J.Phys.Conf.Ser.309,pp. 012008.2011

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Vertex Distribution

• Am-241 X-ray source (installed at the center of the cathode)

• Pressure: 2 bar• Drift field: 200 V/cm/bar

• EL field: 4.5 kV/cm/bar

• Likelihood fit using light profile model for energy and position reconstruction

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First Results: Energy Resolution

8.7 FWHM @ 59.5 keV

A.U.

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Maximum signal in one of the 9 APDs in the centerSignal summed over 24 APDsNo correction yet for drift/diffusion, attachment…etc

Room for improvement

59.5 keV

26.4+30 keV

13.9+17.8+20.8 keV

First Results: Energy Resolution

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A.U.

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8.2 FWHM @ 59.5 keV

Maximum signal in the central APD

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INTERCALIBRATION

• Problems:– APDs gain very sensitive to the temperature and the voltage.– The set up makes challenging to calibrate the APDs one by one.

• Solution:– Intercalibration based on the position simmetry

• Key point Use symmetry in light deposition around the maximum:

– It quantify the difference of energy between APDi and APDj when the maximum signal is in the one between them.

• 59.5 keV X-ray peak of 241Am used.

Aij E i E j

E i E j

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• For events where the energy deposition in the middle APD is maximum, Aij should be 0 (assuming a symmetric EL shower).

• Due to different APD gains this Aij≠0.

• Correct these Ei and Ej using a calibration factor to avoid this problem.

where

After calibration:

• This αij should tend to one and A’ij to zero after calibration is done.

Aij (Emax ) A'E 'i E ' jE 'iE ' j

0 E 'i 1 A'ij1 A'ij

E 'i

E i(Emax ) E 'i

E 'ical E ' j

cal aE 'i bE ' j 0ba

1 A'ij1 A'ij

ij

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Assymetry before calibration: Assymetry after calibration:

Behavior of some of the alpha coeficients during calibration steps:

Clear tendency of α to 1

A’ij tends to zero.

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INTERCALIBRATION: Preliminary results

242Am spectrum (when the energy deposition is maximum in one of the 9 central APDs):

No calibration: Calibration (1st iteration): Calibration (2nd iteration):

RE=13.12% RE=9.35% RE=9.04%

The intercalibration process improves the resolution as we expected.

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First Results: Parameter Scan

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First Results: Tracking

• Cosmic rays trigger• Very primitive

cluster finder

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First Results: T0

Sum of all waveforms over all events

PMT UP

PMT DOWN

Sum APDs

t [s]

Possible to vary drift distance

t between external trigger and signal arrival allows to estimate drift velocity

vd= ~0.17 cm/us (theory: 0.1 cm/us)

Probably N2 impurity Clear peak in both PMTs

at t≈0

Peak in the sum of all APDs

Can we see this on event by event basis???

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Summary and Outlook

• Different EL-TPCs built in collaboration between CIEMAT and IFAE

• EL-TPC with 25 APDs for high pressure XE-gas studies in operation

• Energy resolution 8.2% @ 60 keV (room for improvements)

• Preliminary track reconstruction proved

• Study for t0 detection on going

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CIEMAT LAr lab• 450 liters liquid nitrogen dewar.• 2 cryostats of 70 liters each, high vacuum graded, for liquid argon.• Turbomolecular pump for high vacuum.

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Pe/25

Vis1Vis2

UV1

UV2

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