1 Li Liquid xenon de detector wi with VU VUV-se sensi sitive MP MPPCs for ME fo MEG II experi riment SHINJI OGAWA ON BEHALF OF THE MEG II COLLABORATION "LIQUID XENON DETECTOR WITH VUV-SENSITIVE MPPCS FOR MEG II EXPERIMENT", SHINJI OGAWA, TIPP 2017, BEIJING, CHINA
2 Table of contents 1. LXe γ-ray detector in MEG II experiment 2. R&D for LXe detector 3. Detector construction 4. Summary "LIQUID XENON DETECTOR WITH VUV-SENSITIVE MPPCS FOR MEG II EXPERIMENT", SHINJI OGAWA, TIPP 2017, BEIJING, CHINA
3 MEG II experiment Liquid Xe γ-ray detector Searches for a cLFV decay of muon, μ→e+γ. Gradient Clear evidence of BSM. magnetic l Radiative field Detectable branching ratio (O(10 -12 ~ 10 -15 )) γ μ + decay l is predicted by some BSM models. counter Upgrade of MEG experiment Doubled μ + beam intensity e + e + drift chamber l e + timing counter Doubled detection efficiency l Resolutions of all detectors will become half l Radiative decay counter : R.Iwai (talk in Wed) e+ timing counter : M.Nakao (talk in Thu) Expected sensitivity of MEG II: 4 × 10 -14 l l MEG final result: Br(μ→e+γ) < 4.2 × 10 -13 (90% C.L.) Liquid Xe γ-ray detector To detect monochromatic 52.8 MeV γ-ray from μ→e+γ. l Measuring the hit position, energy, and timing of γ-ray with good resolution l is important to efficiently suppress the accidental background. "LIQUID XENON DETECTOR WITH VUV-SENSITIVE MPPCS FOR MEG II EXPERIMENT", SHINJI OGAWA, TIPP 2017, BEIJING, CHINA
MEG LXe γ-ray detector 4 LXe γ-ray detector was successfully operated in the MEG experiment. l 900 ℓ LXe. l Scintillation light readout by 846 PMTs Advantages of LXe l High light yield (~75% of NaI) γ l Fast (τ decay = 45ns for γ-ray) l High stopping power (X 0 =2.8cm) l Uniform (liquid) Disadvantages of LXe Hamamatsu R9869 l VUV (Vacuum Ultraviolet) scintillation light (λ=175nm) 2-inches l High purity is needed l Low temperature (165K) is required 16% QE for λ=175nm "LIQUID XENON DETECTOR WITH VUV-SENSITIVE MPPCS FOR MEG II EXPERIMENT", SHINJI OGAWA, TIPP 2017, BEIJING, CHINA
LXe detector upgrade 5 We are upgrading LXe detector for MEG II to MEG significantly improve the performance. We have replaced 216 2-inch PMTs on the γ γ-entrance face with 4092 12 × 12 mm 2 MPPCs. l Better position resolution 2 inch from higher granularity. PMT l Improved energy resolution from better uniformity of scintillation readout. l Better timing resolution from TOF estimation with better accuracy MEG II and larger statistics from larger sensitive area. l Increased detection efficiency γ from reduced material of the γ-entrance face. PMT 12 × 12 mm 2 MPPC MPPC ~1 m 2 is covered by MPPC ! "LIQUID XENON DETECTOR WITH VUV-SENSITIVE MPPCS FOR MEG II EXPERIMENT", SHINJI OGAWA, TIPP 2017, BEIJING, CHINA
6 Expected performance MEG Significant improvement is expected for resolutions and efficiency. Detector performance for signal γ-ray MEG MEG II (measured) (simulated) improve by σ (position) ~5 mm ~2.5 mm a factor of 2 ! log scale σ (energy) ~2% 0.7 - 1.5% Imaging σ (timing) 67 ps 50 - 70 ps power Efficiency 65% 70% improves MEG II Position resolution (horizontal) Reconstructed Energy 10 2 Position resolution [mm] MEG I 9 1.8 MEG I 8 MEG II 1.6 MEG II 7 1.4 6 1.2 5 1 4 0.8 3 0.6 2 0.4 1 0.2 0 0 0 2 4 6 8 10 12 14 16 18 20 48 49 50 51 52 53 54 55 56 57 58 log scale Conversion depth [cm] Energy (MeV) "LIQUID XENON DETECTOR WITH VUV-SENSITIVE MPPCS FOR MEG II EXPERIMENT", SHINJI OGAWA, TIPP 2017, BEIJING, CHINA
7 LXe detector status R & D R&D ü VUV-sensitive large area MPPC ü Signal transmission system Production ü MPPC mass production Production ü MPPC mass test ü Signal transmission system ü Cable, PCB, feedthrough ü Modified PMT holders ü Refrigerator Assembly Assembly ü MPPC & PMT installation ü Sensor position survey ü Cabling & connection check Commissioning ü Calibration source installation "LIQUID XENON DETECTOR WITH VUV-SENSITIVE MPPCS FOR MEG II EXPERIMENT", SHINJI OGAWA, TIPP 2017, BEIJING, CHINA
8 1. LXe γ-ray detector in MEG II experiment 2. R&D for LXe detector 3. Detector construction 4. Summary "LIQUID XENON DETECTOR WITH VUV-SENSITIVE MPPCS FOR MEG II EXPERIMENT", SHINJI OGAWA, TIPP 2017, BEIJING, CHINA
9 VUV-sensitive large area MPPC Hamamatsu S10943-4372 MPPC for MEG II LXe detector has been developed in collaboration with Hamamatsu Photonics K.K. VUV-sensitive (PDE (λ=175nm) > 15% ) l Scintillation light of Xe is in VUV range l Realized byremoving the protection layer of resin, optimizing optical - 50 μm pitch pixel - quartz window matching b/w LXe and sensor surface, - crosstalk and for protection and thinning contact layer. afterpulse suppression (VUV-transparent) - metal quench resister - ceramic package Large sensitive area (12 × 12 mm 2 ) l To keep the number of readout channels manageable l Discrete array of four 6 × 6 mm 2 chips l Four chips connected in series at readout PCB to reduce long time constant. "LIQUID XENON DETECTOR WITH VUV-SENSITIVE MPPCS FOR MEG II EXPERIMENT", SHINJI OGAWA, TIPP 2017, BEIJING, CHINA
Performance test of our MPPC 10 We have tested MPPC in LXe, and an excellent performance has been confirmed. l Sufficiently short timing constant has been achieved by series connection. l Single p.e. peak is clearly resolved for large sensitive area. l Gain: 8.0 × 10 5 (@ Vover=7V, series connection) l Low crosstalk & after pulse probability (~15% each@ Vover = 7V) No segmentation Charge distribution using LED Measured waveform -charge[3] {baseline[3]>-0.0005} 0p.e. 450 1p.e. 400 Vover = 7V 350 300 at LXe temp. 100ns No segmentation 250 200 4 segmentations in series 150 100 50 0 0 0.1 0.2 0.3 charge 4 segmentations 100ns in series "LIQUID XENON DETECTOR WITH VUV-SENSITIVE MPPCS FOR MEG II EXPERIMENT", SHINJI OGAWA, TIPP 2017, BEIJING, CHINA
Performance test of our MPPC 11 We have tested MPPC in LXe, and an excellent performance has been confirmed. l Sufficient PDE (>15%) for Xe scintillation light l Good energy resolution down to O(1%) (@10 4 p.e. , α scintillation light) l Good timing resolution down to 40ps (@2000 p.e. , α scintillation light) Energy resolution vs. Photoelectron statistics PDE vs Over Voltage Energy Resolution vs Photon Statistics 0.35 PDE − 1 4 10 × Energy Resolution − 1 3 10 × 0.3 1 2 10 − × 0.25 1 10 − 0.2 0.15 p − 2 1 / (# of p.e.) 4 × 10 0.1 − 2 3 10 × − 2 2 10 × 0.05 0 − 2 10 0 1 2 3 4 5 6 7 3 3 2 2 4 30 10 2 10 10 2 10 10 × × Over Voltage (V) Number of p.e. "LIQUID XENON DETECTOR WITH VUV-SENSITIVE MPPCS FOR MEG II EXPERIMENT", SHINJI OGAWA, TIPP 2017, BEIJING, CHINA
12 Signal transmission system “Coaxial-like structure” PCB l We have developed signal transmission system. l It can transmit ~5000 ch signals. l Long cable (~12m) before signal amplification. l PCB has coaxial-like structure for impedance matching (50Ω), good shielding from external noise, high bandwidth, and low crosstalk. l Feedthrough is based on PCB to realize high density transmission. l This system has been tested in LXe for 600 ch, and confirmed to work properly. PCB-based feedthrough coaxial cable (2.5 – 4.9m) MPPC mounted on PCB coaxial DAQ system cable (8.5m) "LIQUID XENON DETECTOR WITH VUV-SENSITIVE MPPCS FOR MEG II EXPERIMENT", SHINJI OGAWA, TIPP 2017, BEIJING, CHINA
13 1. LXe γ-ray detector in MEG II experiment 2. R&D for LXe detector 3. Detector construction 4. Summary "LIQUID XENON DETECTOR WITH VUV-SENSITIVE MPPCS FOR MEG II EXPERIMENT", SHINJI OGAWA, TIPP 2017, BEIJING, CHINA
14 Mass production/test of MPPCs l Production of 4200 MPPCs was completed. l All of them were tested at room temperature to reject bad MPPC. l I-V curve and breakdown voltage were checked. l Waveform from LED light was checked. l We found only 0.2% bad chips (31 out of 4180 × 4 chips). Waveforms of all 4180 MPPCs with LED light • Waveform from all MPPC looks OK. • Difference of waveform shape between MPPCs looks small. MPPC prod. batch A, B, C, D mV "LIQUID XENON DETECTOR WITH VUV-SENSITIVE MPPCS FOR MEG II EXPERIMENT", SHINJI OGAWA, TIPP 2017, BEIJING, CHINA
15 MPPC installation to the cryostat l MPPCs are mounted on PCBs. MPPC l for signal readout and alignment. のせてる様子 Spacer l PCBs are fixed on CFRP support structure which is attached on cryostat. PCB l These support are designed to Spacer minimize the material. CFRP l Thin support structure with low mass material l Spacers to reduce LXe. "LIQUID XENON DETECTOR WITH VUV-SENSITIVE MPPCS FOR MEG II EXPERIMENT", SHINJI OGAWA, TIPP 2017, BEIJING, CHINA
16 Detector assembly Photo-sensor installation l Detector assembly has been completed. l Photo-sensor installation l Cabling l Connection check for all sensors. l Sensor position measurement by 3D Laser scanner (FARO) l Calibration source (LED, α source) installation. →Detector construction: Finished (Apr.2017). Position measurement by 3D Calibration source (α , 241 Am) laser scanner α source on tungsten wire Precision: < 0.15 ~ 0.5mm "LIQUID XENON DETECTOR WITH VUV-SENSITIVE MPPCS FOR MEG II EXPERIMENT", SHINJI OGAWA, TIPP 2017, BEIJING, CHINA
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