MARS detector technology and the SOLiD experiment A. Vacheret, A. Weber, Y. Shitov, P . Scovell University of Oxford
Talk overview • Introduction to the MARS technology • MARS neutron portal project • MARS antineutrino detector system • Search for Oscillation with Lithium-6 detector : The SOLiD experiment 2
Introduction to the MARS project • MARS technology is being developed as an alternative for neutron and antineutrino detection • high performance replacement to Helium-3 tubes used in various applications (border security, nonproliferation, Science, dosimetry, etc...) • Novelty in how (old and new) components are combined to give better capability • handheld to very large area of detector surface • MARS IP is protected : patent GB2012052097 (PCT phase) • One of main goals is also applications of antineutrino detection at reactors • Develop whole solution with electronics and data processing • technology can be extended with new materials and components (choice of neutron absorber, progress in organic and inorganic scintillators, photosensors, electronics etc...) 3
Where it all started • Confidence in technology come from successful large scale use of plastic scintillator based detectors with embedded WLS fibre read out by solid state photosensors • design, construction and assembly is simplified and system has very good uniformity. System is reliable and requires low maintenance. • Combined high performance required by Science with easier operation (strong point for applications). • Long experience in calibration and operation accumulated in MINOS and T2K experiments MINOS detector plane Construction of T2K calorimeter module (~ 3000 channels) 2.54 cm Fe Extruded PS scint. 4.1 x 1 cm PS planes WLS fiber 4m 0.5m U V planes MPPC Clear Fiber cables Multi-anode 4 PMT
Photosensors: compact readout solution Multi-Pixel Photon counters MPPC 50 μ m 1.3mm 50 um pixel pitch 60-65% active area 1.3 mm x 1.3 mm (T2K device) 667 pixels (50um pitch) Connector design for P0D/ECAL/MRD Nominal gain : 7.5x10E5 WLS Fibre Ferrule PDE (500 nm) ~ 30% MPPC Timing resolution ~ 200-600 ps spring foam Noise 1 MHz/mm 2 at 25ºC connector Cross-talk and after-pulsing ~ 15% PCB board 70 V operation voltage Larger area possible Shroud Recent improvement on noise level and crosstalk 5
MPPC characterisation and model development Characterization of the 1.3 mm x 1.3 mm MPPC for the T2K near detectors. A. Vacheret et al. NIM.A, doi:10.1016/j.nima.2010.02.195 70.59 V @ T=22C • Characterisation of MPPC response • Use data from measurements to predict behaviour Response to photon signal 70.81 V @ T=22C 71.06 V @ T=22C 6
Electronics development for T2K The front end readout system for the T2K-ND280 detectors Vacheret, A.; Greenwood, S.; Noy, M.; Raymond, M.; Weber, A. LV POWER HV MINIATURE COAX CALIBRATION CHARGE doi:10.1109/NSSMIC.2007.4436543 REGULATORS SWITCH CONNECTORS INJECTION SWITCHES MPPC connection and channel 5V division MPPC Bias voltage ~ 70 V EXTERNAL Channel cal. I 2 C DATA test pulse ADC 3.3V 9 cm ADC POWER TRIG 2.5v 1.2V Voltage trim +5V range 16 cm High Voltage trim GAIN SPLITTING COMPONENTS PROM DACs (8 altogether) • 64 Hi/Lo gain ADC channel timestamping TEMPERATURE AND VOLTAGE MONITORING Trip-t Trip-t • Individual MPPC HV trim (8 bit, 5V range) Xilinx Spartan 3 FPGA • On board charge injection circuit Trip-t Trip-t • Temperature sensors 7
MARS neutron portal project
MARS technology : neutron portal project • Large scale neutron portal system based on solid scintillator technology • Active element : transparent bars with embedded WLS fibres with 6 LiF:ZnS layers • 6 months project completed this summer • Develop optimised and compact system with in-house electronics front-end data readout to digitiser active detector stack with 16 bars HV, LV in electronics electronics 1600.0 mm boards 1 boards 2 1700.0 mm 2000.0 mm 9
Neutron detector construction • Easy construction and assembly 10
MARS neutron system performance • We demonstrated cost-effective replacement of 3He tubes in portal • validated performance at NPL • > 70% neutron detection efficiency • Meet security industry standards • gamma rejection better than 1:1,000,000 level MIX - PSD comparison MIX - PSD comparison • efficiency of neutron not Entries affected by large gamma flux 5 10 7 Neutron Loss (%) Loss in Effn (%) 6 5 4 10 • First neutron detector based on read 4 3 60 Co out with solid state photosensors 2 3 10 1 (publication in preparation) 0 -7 -6 -5 -4 -3 -2 -1 10 10 10 10 10 10 10 1 10 10 -6 Discrimination 2 10 • Development of other type of neutron system under investigation 10 252 Cf 1 0 50 100 150 200 250 300 350 400 Integrated Signal (PE) 11
MARS antineutrino detector
MARS antineutrino detector • Based on requirement to develop compact and low maintenance detector system for reactor monitoring • rate and spectral measurement towards use in safeguards applications • robust to backgrounds by design • Clear signature for neutron : Use of 6 LiF:ZnS(Ag) • good level of segmentation for accurate determination of interaction point • fully active : target detector used as veto • flexible and scalable design • compact system with photosensor read out 13
MARS antineutrino detector element X read out 5 cm 5 cm Y read out Cast scintillator cubes (PVT EJ-200) cosmics muon light yield in 5cm cube htot htot Entries Entries Entries 1000 1000 • large scintillator signal to increase sensitivity Mean Mean 34.18 34.18 200 RMS RMS 15.46 15.46 2 2 and good energy resolution χ χ / ndf / ndf 2.901 / 1 2.901 / 1 180 Constant Constant 199.1 199.1 ± ± 11.6 11.6 Mean Mean 29.77 29.77 ± ± 0.55 0.55 Sigma Sigma 8.575 8.575 ± ± 1.007 1.007 160 ~ 60 PE (both ends) • threshold energy down to around 100 keV 140 120 Ethres 150 keV 100 • σ (E)/E ~ 0.25 @ 2 MeV Eres 0.13 80 60 • Easy to manufacture in large quantity 40 20 LiF:Zns(Ag) 0 0 20 40 60 80 100 120 NPE • 6 Li has large cross-section on thermal neutrons 14
Principle of antineutrino detection × 10 e+ Energy / MeV MC 0.4 9 8 0.35 7 0.3 6 0.25 5 e + 0.2 4 0.15 3 0.1 2 n 0.05 1 0 0 0 5 10 15 20 25 30 35 40 45 50 e+ track length / mm × 0.1 Tn / MeV 0.09 MC 1 0.08 0.07 0.8 0.06 0.6 0.05 0.04 0.4 0.03 Detect antineutrino via well known 0.02 0.2 0.01 inverse neutron decay 0 0 0 50 100 150 200 250 300 350 n track length /mm ν e + p → e + + n ¯ MC Detect neutron via reaction on Lithium-6 n + 6 Li → 3 H + α + 4 . 78 MeV e + n Time coincidence and 3D localisation of interaction 15 Δ t ~ 1-150 us
Detector layout ν e ν e ν e Y view ν e Detector active stack : 1m x 1m x 1m Active volume stack • 1 ton fiducial mass • 20 x 20 cells per plane ~ 10k cells and 2k read out channels • 3D position reconstruction using X and Y coordinates Detector footprint ~ 1.5m 16
17 Neutron detection AmBe X channel Y channel High capture efficiency on Lithium-6 • signal detection efficiency > 70% • comparable to Helium-3 • localised signal Very high discrimination between neutron and γ Integrated Charge - All events + Neutron events Integrated Charge - All events + Neutron events 30 Number Of Peaks AmBe 4 10 # Entries 3 • simple charge cut and pulse properties 25 10 neutron signal 3 10 • very good handle on background γ 20 ε γ < 10 -4 2 10 2 15 10 • Use neutron signal to trigger detector read out (simple charge trigger or via 10 digital pulse processing) 10 10 EM signal 5 1 0 20 40 60 80 100 120 140 0 Summed Integrated Charge (NPE) 1 0 50 100 150 200 250 300 350 400 450 500 Summed Integrated Charge (NPE)
Samples 18
Electronics development 10-20 us signal out LV HV Main features Digitiser Board • signal sampling : 80MS/s 12 ADC bit cADC • dead-timeless • on board digital processing : pedestal suppression, readout threshold, PSD etc.. FPGA • 32 Channels per board virtec 6 • charge injection system • MPPC HV fine control per channel • Use neutron signal features to trigger on IBD event 19
Development of digital pulse processing methods • Use current Mars neutron system to study various methods to be implemented in front-end electronics • first studies made by student • charge based • template matching (Normalised cross- correlation) • Development and validation to be done • robustness and reliability is key 20
21 Positron imaging capability Positron - Face 1 Positron - Face 2 14 14 Cubes Y Cubes Y MC MC 13 13 γ 5 γ 2 12 12 e+ 2 1 11 11 e+ 78 37 1 γ 10 10 1 9 9 1 2 8 8 7 7 5 6 7 8 9 10 11 12 13 14 15 16 5 6 7 8 9 10 11 12 13 14 15 16 Cubes X Cubes X Large E deposit with additional activity from annihilation γ s • signal within 15 cm around high hit • topology cut to increase selection purity
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