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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
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 %
slide18

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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