Performance of the SoLid Reactor Neutrino Detector - PPNS 2018 - Maja Verstraeten on behalf of the SoLid collaboration
Overview The sterile neutrino The SoLid neutrino detector @ the BR2 reactor Construction and QA Commisioning and callibration 2
Overview The sterile neutrino The SoLid neutrino detector @ the BR2 reactor Construction and QA Commisioning and callibration 3
The sterile neutrino hypothesis Reactor -and Gallium anomalies can be measured predicted rate explained by an additional mass state Small correction to 3x3 neutrino mixing can explain unexpected active neutrino / oscillation data Sterile neutrino not detectable through weak interaction. Only indirect measurement possible 4
Sensitivity to a new neutral state Oscillation dictated by properties of sterile neutrino Oscillation apparent over distance and energy Best fit gives Δm² ~ 1.73 eV² and sin²(2θ) ~ 0.1 Coverage in L/E requires a good position -and energy resolution Indication of research space 5
Reactor spectrum distortions Energy spectrum distortions seen by all three reactor experiments with high significance (dubbed “the bump”) Amplitude of effect correlated with reactor power 6
Overview The sterile neutrino The SoLid neutrino detector @ the BR2 reactor Construction and QA Commissioning and callibration 7
Challenges at VSBL Detector Oscillation search demands high spatial -and energy resolution Effective background rejection required, while facing low overburden and reactor radiation Reactor VSBL search demands compact reactor core with well understood fuel composition Reactor site poses safety -and security implications 8
Challenges at VSBL SoLid solutions SoLid detector Detector High segmentation gives 3D spatial Oscillation search demands high information spatial -and energy resolution Suitable photo detectors give energy Effective background rejection resolution required, while facing low Active and passive shielding overburden and reactor radiation BR2 Research reactor Reactor Belgian Reactor 2 (BR2) at SCK-CEN VSBL search demands compact Twisted design of fuel matrix gives reactor core with well compact core understood fuel composition High enriched uranium fuel Reactor site poses safety -and Access ports for experiments, on axis security implications with reactor core 9
BR2 nuclear site Compact research reactor Low background site ⌀ 50 cm and heigth 90 cm Low neutron and gamma fluxes Fuel 93.5% 235 U No surrounding Thermal power 50-80 MW experiments Duty cycle 150 days/year Overburden 10 m.w.e. (~1month cycles) SoLid at baseline 6-9 m 10
SoLid Phase 1 detector 5cm cubes give resolution on 3D topological information 16x16 cubes stacked in planes Planes grouped per 10 in 5 modules, Modules installed on movable rail system 1.6t fiducial mass 11
SoLid Phase 1 detector Target sensitivity Container 2.4x2.6x3.8 m³ Cooled to 10°C to reduce MPPC dark Energy resolution count rate (~1/10) IBD efficiency 30% Shielding Signal to background 3:1 Water walls: 50cm thick, 3.4m high, 28t Polyethylene ceiling: 50cm thick, 6t Cadmium sheets → Full Geant4 simulation 12
SoLid detection principle Anti-electron-neutrinos detected through inverse beta decay (IBD) in the composite scintillator element Prompt positron signal Positron energy contained in PVT cube Allows localisation of interaction Gives the anti-neutrino’s energy Delayed neutron signal Neutron captured in 6 LiF:ZnS close to interaction 13
SoLid signal Example of prompt and delayed coincidence First reactor cycle in december 2017 First prompt delayed candidates Δt = 40µs 14
Trigger sheme Data-rate of digitised MPPCs of ~3 Tb/s total T riggers and sophisticated online data reduction to handle data rate Counting peaks over threshold in local timewindow Dedicated PSD algorithm developed for neutron signals: ~80% effjcient. Large bufger around neutron delayed signal (700µs and 7 planes) to collect prompt signal 15
SoLid signal identification Prototype results Positron (EM) and neutron signals discriminated based on pulse shape (peaks over threshold) IBD signal identified by Δt = t delayed – t prompt Δr = |r delayed – r prompt | Prompt energy Others include multiplicity, directionality and fiducial layer Simple cut based analysis shows significat reduction in backgrounds 16
Overview The sterile neutrino The SoLid neutrino detector @ the BR2 reactor Construction and QA Commisioning and callibration 17
Plane construction ~13 000 cubes manually washed, weighted, wrapped, stacked,... All cube components product information stored in database PVT mass Li mass Total mass Fiducial mass Frame 18
Plane qualification Each cube scanned with at ‘Calipso’ automated robot least two sources: for X Y scanning of planes Gamma source to test cube & with calibration sources channel light yield. Practice run with SoLid Neutron source to test cube electronics and software neutron effjciency. 19
Plane qualification – gamma source Measuring the compton edge of 1270 keV gammas from 22Na demonstrates Light yield > 60PA/MeV. LY~30% higher than expectations. Homogeneous response 20
Plane qualification – neutron source Neutron source demonstrates high and homogeneous neutron reconstruction effjciency (trigger + ID) Comparison with MC indicate reconstruction effjciency > 60% (GEANT4 simulation) Identifjcation and correction of issues before plane installation in module 21
Plane qualification Difgerent source show high linearity combined with 235 U this gives a strong handle on 5 MeV distortion 22
Overview The sterile neutrino hypothesis The SoLid neutrino detector @ the BR2 reactor Construction and QA Commisioning and callibration 23
Commissioning at BR2 reactor Commissioning of the full detector completed begin of February 2018 Expected ~150 reactor on data in 2018 24
MPPC equalisation 99% channels operational Amplitude response calibrated to high quality, spread ~1% Voltage scans used to calibrate individual MPPC breakdown voltages and amplifjcation responses Equalise for gain response (i.e 1 PA amplitude) of 32.0 ADC/PA - equivalent to 1.8 V over-voltage SoLid preliminary 25
Calibration at BR2 reactor Second calibration robot in situ: CROSS Sits above detector planes. Mechanically open gap between sets of ten planes Source free to move in gap 26
Calibration at BR2 reactor – gamma Global data Per plane Preliminary results in 96% of ~Homogeneous response cubes ( Average of plane is used for Row with low LY identifjes non calibrated cubes) coupling from fjber to MPPC Clear attenuation pattern - will be or mirror with problems corrected 27
Calibration at BR2 reactor – neutron Clear neutron identifjcation after neutron trigger Absolute neutron reconstruction effjciency over all detector cells (T rigger + ID) Neutron reconstruction effjciency during commissioning > 75%. Statistical error per cube wih mean value of 2.5% and max of 6% 28
Calibration at BR2 reactor Excellent agreement between calibration at 1.27 MeV and 4.4 MeV Good indication of linearity in energy response Need to validate with more sources 29
Calibration with muons SoLid prototype 30
Physics data taking Stable data taking since february Recons ZnS rate Highly stable for both reactor on and ofg Online, live, remote detector monitoring Online event reconstructjon for subsample of data Physics variables available online 31
Conclusion Constructjon and installatjon of SoLid detector completed in December 2017 Commissioning of SoLid detector at BR2 research reactor fjnished early 2018 Channel response amplitude calibrated to ~1% First calibratjon results indicate a good uniformity and linearity of the signal Trigger effjciency and light yield are higher than expected Physics data taking and fjrst analysis ongoing 32
Thank you for your attention 33
Recommend
More recommend
