High resolution scintillation detectors for dbd
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High resolution scintillation detectors for DBD. Jean-stephane Ricol CENBG – CNRS - France. ILIAS July 1-5, 2007 Blaubeuren. Outline . SuperNemo R&D : very promising results using liquid scintillator : Motivations for using LS Measurements made in CENBG – Bordeaux

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High resolution scintillation detectors for dbd

High resolution scintillation detectors for DBD

Jean-stephane Ricol

CENBG – CNRS - France

ILIAS

July 1-5, 2007 Blaubeuren


Outline

Outline

  • SuperNemo R&D : very promising results using liquid scintillator :

    • Motivations for using LS

    • Measurements made in CENBG – Bordeaux

    • Measurements made in INR - Kiev

  • Prospects and improvements :

    • Large size detector

    • High QE PMTs

    • Optimization of surface for light collection


Motivation and goal

Motivation and goal


Solid liquid scintillator

Solid / Liquid scintillator

  • Same light yield

  • Different attenuation length

Liquid : Latt > 10-25 m

Expect high resolution even

for large size detector

~ 20cm x 20 cm x 20 cm

Solid : Latt ~ 3 m

h = 2 cm FWHM = 7-8%

h = 10 cm FWHM = 9-10%

My talk is focused on LS results


Measurements in bordeaux

Measurements in Bordeaux

Choice of LS : LAB

  • Linear AlkylBenzene

  • High light yield (50% ant.)

  • Good transparency (Latt > 10 m)

  • High flash point (130°C)

  • Very low toxicity

(literature data)

Few measurements with liquid Bicron BC 531 (light yield 59% ant., latt = 3.5 m) for comparison


Lab emission spectra

LAB emission spectra

Made and measured in Dubna

Need absorption spectrum measurement


Medium size container

Teflon

Delrin

10 cm

LS

Teflon

5 cm

LS

Medium-size container

PMT = Photonis 3” XP5312b QE ~ 33%

LS active height = 5 or 10 cm

(from bottom to PMT photocathode)

7 cm

PMT is in the LS = direct light transmission


Medium size container1

Simulation

Medium-size container

  • Entry face in Kapton :

  • Very good breaking strength

  • with 25 µm thickness

60 times lower than breaking point

  • Very good chemical strength LS doesn’t damage it

  • After 6 months Kapton foil didn’t sweat any LS leak

  • Kapton is yellow and transparent -> need reflector : Al deposit


Aluminium deposit on kapton

Aluminium deposit on Kapton

Kapton foil

Reference quartz

Al sample in a smelter heated by 30 A currant (Tevaporation = 800 °C)

Evaporation projects Al in 4pi, it stops

when quartz measures ~ 100 nm deposit

We obtain a good mirror

All is inside a vacuum vessel (10-6 atm)


The test bench

The test bench

CENBG test bench

Black box :

LAB container

+ PMT (3” XP5312b Photonis)

Electron source

Spectrometer

90Sr source, 370 MBq

E/E ~ 1%

Range 0.4 – 2 MeV

XY table

DAQ electronics


Results light emission and propagation

Results : light emission and propagation

BC-531 : light yield 59% ant., Latt = 3.5 m (data sheet)

Dubna LS = LAB : light yield ~50% ant., Latt > 10 m (SNO+ values)

LAB LS is much better than BC531

=> Attenuation is more important than light yield

Must compare emission+attenuation (l) measurements


Results light collection

Results : light collection

LAB LS

  • Delrin vs Teflon : same values within the errors

  • Diffusing medium is better than reflecting medium on sides for this geometry (7 cm diameter, 5 cm high)


Results position effect

FWHM @ 1 MeV (%)

Beam position (cm)

Results : position effect

No effect on resolution, light is emitted and collected independently of the interaction position


Results size effect

Results : size effect

No effect as expected from large Latt

  • Comparison with plastic scintillators (same PMT as LS)

  • PS1 = 7.5 cm x 2 cm : 8.0%

  • PS2 = 7.5 cm x 10 cm : 9.8%

Strong attenuation with solid

 liquid is a much better candidate for large size detector


Prospects in bordeaux

Prospects in Bordeaux

  • First of all we must prove the same promising results can be reached with large size container + 8” PMT

    • New container in construction, we will first test Kapton resistance (simulation of mechanical strengths claim it should be ok)

  • O2 purge by N2 bubbling should increase the detected number of photons by 10-20%


Measurements in kiev

Measurements in Kiev

Similar container

84×92 mm

Different LS :

Toluene + pTP 5 g/l + POPOP 0.1 g/l

PETF film

0.5 mg/cm3

Add AlMyl

teflon

Pipe for O2 purging

(pure argon)

Similar QE PMT (Photonis 3” XP2412 QE ~ 33%)

from A. Danevich et al


Results

207Bi

Results

FWHM = 7.4% @ 976 keV

from A. Danevich et al

  • Resolution better than with LAB (7.4 vs 8.2 %) :

  • LS light yield or Latt higher ? need spectra measurement

  • O2 purge ? 15% more light collection : 8.2  7.6 %


High resolution scintillation detectors for dbd

Large container

Mylar film 1.7 mg/cm2

23 cm

Teflon container:volume 6.3 dm3 window area 3.5 dm2

5 ” PMT EMI 9390 Unfortunately the PMT is not of so good quality QE≈24%

A.A.Adadurov et al.


Results for large container

207Bi BG-subtractedspectrum

Teflon tape 5.6 mg/cm2 +Aluminized Mylar 0.6 mg/cm2

207Bi

Pileup of signals

FWHM = 11 %

(for 33% QE : FWHM  9.6%)

Results for large container

Resolution is not good (8% expected)

Bad PMT ? High counting rate (18 kHz) ?

A.A.Adadurov et al


Uniformity of light collection

Uniformity of light collection

●100(1)%

●100(1)%

●100(1)%

●100(1)%

●100(1)%

Uniformity tested by moving the 207Bi source by 2cm step

No difference was observed within 1% accuracy

A.A.Adadurov et al


Prospects in kiev

Prospects in Kiev

  • PMT with QE≈30%

  • Measurements in a shield to suppress BG counting rate

  • Lower activity 207Bi source


Light collection simulation

Light collection simulation

Very promising results in both labs but still need to be improved : light simulation can help us to optimize photon collection and improve the resolution

Geant4 : detector + particle interaction + light simulation

Need detailed spectra : preliminary results simulated with PS data

Simulation of PS block F20cmx20cm


Light collection simulation1

Plot from E. Chauveau

Refl.

Diff.

Refl %

Refl.

Refl.

Diff.

Diff.

Light collection simulation

Effect of light collection on side : reflection vs diffusion

There is an optimization of the surface !!

We can win 0.3-0.5% on the resolution

Must try several layers and check it experimentally

2 layers


Super super pmts

Super super PMTs

New PMTs : super super bialkali Photocathode

CENBG test Photonis PMTs and UCL test Hamamatsu PMTs

QE : 32% -> 42 % => resolution : 8 (7) % -> 7 (6) %

we are very optimistic for the 7% goal !!!


Conclusions

Conclusions

  • Very good results obtained from 2 teams on medium size container : LS is very promising

  • First results on large size container showed unexpected bad resolution,incoming new measurements (in both Kiev and Bordeaux)

  • Very good uniformity of light emission/collection measured in both labs

  • Experimental and simulation work on the optimization of light collection on sides : geometry, diffusion/reflection … in order to improve resolution

  • High QE PMTs will do a large part of the work

  • We are thinking about the container design for SuperNemo


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