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Calibration of the SoLid detector
David Henaff
To cite this version:
David Henaff. Calibration of the SoLid detector. NuPhys2018: Prospects in Neutrino Physics, Dec 2018, Londres, France. �hal-02458192�
LATEX TikZposter
Calibration of the SoLid detector
David HENAFF on behalf of the SoLid Collaboration
SUBATECH, CNRS/IN2P3, Universit´e de Nantes, IMT Atlantique, Nantes, France
(henaff@subatech.in2p3.fr)
Calibration of the SoLid detector
David HENAFF on behalf of the SoLid Collaboration
SUBATECH, CNRS/IN2P3, Universit´e de Nantes, IMT Atlantique, Nantes, France
(henaff@subatech.in2p3.fr)
Physics motivations: Two outstanding issues in neutrino physics:
1.
Recent short baseline neutrino
ex-periments revealed anomalies:
– Gallium Anomaly (GA): ∼ 10% deficit mea-sured neutrino flux from sources calibrating solar radiochemical experiments. [1]
– Reactor Antineutrino Anomaly (RAA): ∼ 6% (3 sigmas) deficit in measured antineutrino flux wrt updated predictions. [2]
Could sign the presence of new neutrino state: sterile neutrino !
2. Distortion (”5 MeV bump”):
• Observed in the antineutrino energy spectrum by ex-periments that measured θ13. [3]
• Reactor prediction or experimental problem?
The SoLid experiment
In a nutshell:
Measurement of reactor νe flux and spectrum. • At very short baseline Sensible to sterile oscillation.• BR2 research reactor at SCK·CEN Highly enriched in
235U constraints flux and spectrum predictions.
• Novel technology: PVT + ZnS scintillators Different energy response than for liquid scintillators: Contraints detection effects in sterile and distortion study.
Challenges:
• Close to a reactor and on surface Huge reactor and cosmic backgrounds (n,γ,µ).
• Oscillation to be resolved in a few meters Highly seg-mented detector.
The SoLid detector:
• Detection principle: Inverse Beta Decay (IBD): νe + p −→ e+ + n
• 3D reconstruction of interactions
– 50 planes of (16 × 16) 5 × 5 × 5 cm3 cubes.
– cube wrapped with 6LiF:ZnS sheets for neutron capture: n +6 Li →3 H + α
– Scintillation photons captured by network of wavelength shift-ing fibres and read-out by 3200 SiPMs.
– PSD discrimination between Electromagnetic Signal (ES) and Neutron Signal (NS).
A challenging calibration
Unprecedented calibration:
• 12800 cubes read-out by 3200 channels have to be calibrated individually with a 2% precision for the energy scale to correct inhomogeneity.
• 2 types of calibration performed γ and n: Measure the response of PVT and ZnS scintillators.
• Tiny size of cube: Implies no photo-peak the calibration is based on Compton edges.
• Need fast calibration to maximize physics data taking: High activity sources and specific DAQ configuration.
Typical calibration configuration:
• Dedicated in-situ robot for calibration purposes called CROSS.
– Allows us to place the source between all modules that composed the detector. 9 positions per gap and 6 gaps. Neutron calibration:
Source AmBe 252Cf Activity [n/s] 1794 ± 35 3763 ± 44 Emean [MeV] 4.2 2.1
– Neutron activity have been cali-brated by the National Physical Laboratory (UK). Reduce uncer-tainty on neutron reconstruction ef-ficiency.
– Full scan of the detector with one source in 3 days.
Gamma calibration:
Source: 22Na 137Cs 60Co 22Na 207Bi AmBe Energy of CE [MeV]: 0.341 0.477 1.04 1.054 0.858 + 1.547 4.2 – 22Na principal source, full scan in 1 day each reactor off.
– Read-out only ± 5 planes around the source to avoid dead time.
– Use a threshold trigger for source with a energy above 1 MeV. Random trigger for others.
– Two different methods to control systematic uncertainties, agreement at 2%. – Muons are used to monitoring the light yield, see Giel’s poster (E29).
Neutron reconstruction efficiency measurement:
Neutron reconstruction:
• Efficiency to reconstruct the neutron taking into account of trigger and offline particle identification:
– Neutron trigger based on Peak over Threshold (PoT).
– Distinction between NS and ES is based on signal amplitude versus the Integral over amplitude.
Results:
• Can measure neutron reconstruction efficiency cube per cube
• Neutron reconstruction efficiency of 75 %.
• Mean Statistical error 2.5%.
Light yield and resolution measurement
Kolmogorov method:
• Simulation of calibration runs using Geant4.
• Smeared the true energy spectrum of each cube for several resolution σE and several light yield LY values.
• Compute Kolmogorov test between data and simulated histograms.
Analytical method:
• Gamma interacts by Compton scattering so the cross-section is given by the Klein-Nishina formula.
• We compute the convolution of this cross-section and a Gaus-sian with an energy dependent resolution.
Results:
• Light yield has been measured in all cube with 4 channels, average: 77 PA/MeV with a resolution of 14% at 1 MeV.
• The agreement between 22Na and AmBe results prove the linearity of PVT.
• Good detector homogeneity.
Conclusion
• Full detector calibrated:
7→ Good precision on energy scale and linearity has been checked above 1 MeV.
7→ High neutron reconstruction efficiency. Agreement between the sources at 3%.
• Ongoing work:
7→ Partial scan of the detector with all γ sources has been completed. Analysis ongoing.
7→ Statistical uncertainty on neutron reconstruction efficiency will be reduced with further calibration campaign.
References
[1] Carlo Giunti and Marco Laveder. “Statistical significance of the gallium anomaly”. In: Phys. Rev. C 83 (6 2011), p. 065504.
[2] G. Mention et al. “Reactor antineutrino anomaly”. In: Phys. Rev. D 83 (7 2011), p. 073006.
[3] Y. Abe et al. “Improved measurements of the neutrino mixing angle θ13 with the Double Chooz
