Recent results on galactic cosmic rays with the DAMPE experiment Xin Wu Department of Nuclear and Particle Physics University of Geneva, Switzerland XSCRC2019, CERN 14 November, 2019 Outline • Introduction to the DAMPE experiment • Description and performance of the detector • Recent cosmic ray results Xin Wu XSCRC2019, 14/11/2019 2 DAMPE Launched ~4 years ago (17/12/2015) High energy particle physics experiment in space Xin Wu XSCRC2019, 14/11/2019 3 The Detector Plastic Scintillator Detector (PSD) Silicon-Tungsten Tracker (STK) BGO Calorimeter (BGO) Neutron Detector (NUD) ü Charge measurements (PSD and STK) ü Precise tracking with Si strip detectors (STK) high energy g-ray, ü Tungsten photon converters in tracker (STK) electron and cosmic ray ü Thick imaging calorimeter (BGO of 32 X0, 1.6 l) nuclei telescope ü Extra hadron rejection (NUD) Xin Wu XSCRC2019, 14/11/2019 4 The Collaboration • China – Purple Mountain Observatory, CAS, Nanjing – Institute of High Energy Physics, CAS, Beijing – National Space Science Center, CAS, Beijing – University of Science and Technology of China, Hefei – Institute of Modern Physics, CAS, Lanzhou • Switzerland – University of Geneva, Switzerland • Italy – INFN Perugia and University of Perugia – INFN Bari and University of Bari – INFN Lecce and University of Salento – INFN LNGS and Gran Sasso Science Institute Xin Wu XSCRC2019, 14/11/2019 5 The DAMPE Satellite EQM, Oct. 2014, CERN Integrated satellite, Sept. 2015, Shanghai Weight : 1450/1850 kg (payload/satellite) Power: 300/500 W (payload/satellite) Readout channels: 75,916 (STK 73,728) Size: 1.2m x 1.2 m x 1.0 m Xin Wu XSCRC2019, 14/11/2019 6 The Orbit • Altitude: 500 km • Inclination: 97.4065 • Period: 95 minutes • Orbit: sun-synchronous Launched Dec. 17 2015 • Dec. 20: all detectors powered on, except the HV for PMTs • Dec. 24: HV on! • Dec. 30: stable trigger condition Xin Wu XSCRC2019,• Very 14/11/2019 smooth operation since! 7 Particle hit counts vs orbit • 15 orbits/day, 96 minutes/orbit • ~50 Hz average trigger rate, ~5 M events/day – Main high energy trigger and prescaled low energy and MIP triggers Xin Wu XSCRC2019, 14/11/2019 8 Plastic Scintillator Detector (PSD) 2 layers (x, y) of strips 1 cm thick, 2.8 cm wide and 88.4 cm long Sensitive area 82.5 cm x 82.5 cm, no dead zone • Strip staggered by 0.8 cm Readout both ends with PMT, each uses 2 dynode signals (factor ~40) to extend the Xin Wu XSCRC2019,dynamic 14/11/2019 range to cover Z = 1, 26 9 Silicon-Tungsten Tracker (STK) • Outer envelop 1.12m x 1.12m x 25.2 cm • Detection area 76 x 76 cm2 • ~7 m2 of silicon • Total weight: 154.8 Kg • Total power consumption: ~85W Xin Wu XSCRC2019, 14/11/2019 10 The STK structure • 12 layers (6x, 6y) of single-sided Si strip detector mounted on 7 support trays • Tungsten plates (1mm thick) integrated in trays 2, 3, 4 (from the top) – Total 0.85 X 0 for photon conversion 192 ladders 768 silicon sensors 95 x 95 x 0.32 mm3 1,152 ASICs 73,728 channels Xin Wu XSCRC2019, 14/11/2019 11 BGO Calorimeter (BGO) • 14-layer BGO, 7 x-layers + 7 y-layers – BGO bar 2.5 cm2.5 cm x 60 cm, readout both ends with PMT • Use 3 dynode (2, 5, 8) signals to extend the dynamic range – Charge readout/Trigger: ASIC with dynamic range up to 12 pC Detection area 60cm60cm X Layer (22 BGO bars) Y Layer 14 Layers Xin Wu XSCRC2019, 14/11/2019 Total thickness 32 X0/1.6 l 12 Neutron Detector (NUD) • 4 large area boron-doped plastic scintillators ( 30 cm30 cm1 cm) – Detect the delayed thermal neutron capture signal to help e/h separation – Gating circuit to detect delayed signal with a settable delay (0-20µs) after the trigger from the BGO n + 10B → α + 7Li + g Xin Wu XSCRC2019, 14/11/2019 13 On-ground calibration • Several weeks at CERN PS and SPS beams from Oct. 2012 – Nov. 2015 (EQM) – Plus many cosmic muon data (FM) Nov. 2014 Oct. 2012 Nov. 2015 XinMarcH Wu 2015 XSCRC2019, 14/11/2019 14 Electron energy linearity and resolution 1-20 GeV 50-243 GeV Linearity DE/E < 1.5% for > 100 GeV Good linearity and resolution, good agreement between test beam and simulation Xin Wu Energy correction:XSCRC2019, ~6-7% 14/11/2019 for 100 GeV – 1 TeV 15 Proton energy resolution Good agreement between test beam and simulation Proton energy cannot be easily corrected. Need unfolding! Xin Wu XSCRC2019, 14/11/2019 16 BGO in-flight MIP calibration • “MIP” calibration: ADC → MeV and equalization, use events near the equator, 20 MIP spectrum of a BGO bar Geomagnetic MIP MPV shift % cut-off effect MPV of a BGO bar After “temperature correction” MeV ADC BGO Helium MIP Xin WuProton “MIP” MPV vs temperatureXSCRC2019, (time) 14/11/2019Helium “MIP” mean vs time, stable17 <1% Absolute energy scale validation • Overall energy scale can be checked with geomagnetic cut-off effects – Charge particles detected in a geomagnetic zone have specific cut-off in the flux (deflection by the magnetic shield) • Use L in 1 – 1.14, cut-off ~ 13 GeV • Measured cut-off compared to MC simulation with IGRF-12 model and back-tracing code Cdata/Cpred = 1.0120.017(stat.) 0.013(sys.) McIlwain L shells Energy scale agrees with expectation within 2% Stable with time (small decrease in cut-off due to solar modulation) Xin Wu XSCRC2019, 14/11/2019 18 PSD in-orbit charge measurement Astropart. Phys., 105, 31 (2019) Element sZ H 0.07 He 0.10 Li 0.14 Be 0.21 B 0.17 C 0.18 N 0.21 O 0.20 Excellent for cosmic-ray measurements Xin Wu XSCRC2019, 14/11/2019 19 STK noise very stable since launch 1 year Average noise 2.84-2.88 ADC Very small temperature variation Xin Wu ~4 year in orbit, >99.5%XSCRC2019, channels 14/11/2019 are still working perfectly! 20 STK in-flight alignment • Good thermal stability guaranteed a good short term mechanical stability 300 x2 x1 Re-align every 2 weeks to x3 x6 200 x4 y1 correct for long term shift x5 y6 y2 aligned m) y3 non-aligned µ y4 y5 100 90 80 70 60 Outside layers with larger extrapolation errors Effective resolution ( 50 40 Intrinsic position resolution 40 -50 µm 30 10 20 30 40 50 θx(θy) (deg) Unbiased hit residual of 12 layers before/after (re)alignment, as function of incidence angle Xin Wu XSCRC2019, 14/11/2019 21 X Residual width variation: aligned 1.6 0° < Q < 10° 1.6 10° < Q < 20° 1.5 x x1 x2 1.5 x 1.4 x3 x4 1.4 1.3 1.3 1.2 x5 x6 1.2 1.1 1.1 1 1 2015 2016 2016 2017 2017 2018 2018 2019 2015 2016 2016 2017 2017 2018 2018 2019 1.6 Dec-3120°Jul-01 < QDec-31 < 30Jul-01° Dec-31 Jul-02 Dec-31 Jul-02 1.6 Dec-3130° Jul-01< Q Dec-31 < 40Jul-01° Dec-31 Jul-02 Dec-31 Jul-02 1.5 x 1.5 x 1.4 1.4 (January,1st) 1.3 1.3 1 1.2 1.2 s 1.1 1.1 / 1 1 1 s 2015 2016 2016 2017 2017 2018 2018 2019 2015 2016 2016 2017 2017 2018 2018 2019 1.6 Dec-31 Jul-01 Dec-31 Jul-01 Dec-31 Jul-02 Dec-31 Jul-02 1.6 Dec-31 Jul-01 Dec-31 Jul-01 Dec-31 Jul-02 Dec-31 Jul-02 40° < Q < 50° Q > 50° 1.5 x 1.5 x 1.4 1.4 1.3 1.3 1.2 1.2 1.1 1.1 1 1 2015 2016 2016 2017 2017 2018 2018 2019 2015 2016 2016 2017 2017 2018 2018 2019 Xin Wu Dec-31 Jul-01 Dec-31 Jul-01 Dec-31 Jul-02 9thDec-31 DAMPEJul-02 Workshop,Dec-31 15/06/2019Jul-01 Dec-31 Jul-01 Dec-31 Jul-02 Dec-31 Jul-02 22 X Residual width variation: not aligned 1.6 0° < Q < 10° 1.6 10° < Q < 20° 1.5 y y1 y2 1.5 y 1.4 y3 y4 1.4 1.3 1.3 1.2 y5 y6 1.2 1.1 1.1 1 1 2015 2016 2016 2017 2017 2018 2018 2019 2015 2016 2016 2017 2017 2018 2018 2019 1.6 Dec-3120°Jul-01 < QDec-31 < 30Jul-01° Dec-31 Jul-02 Dec-31 Jul-02 1.6 Dec-3130° Jul-01< Q Dec-31 < 40Jul-01° Dec-31 Jul-02 Dec-31 Jul-02 1.5 y 1.5 y 1.4 1.4 (January,1st) 1.3 1.3 1 1.2 1.2 s 1.1 1.1 / 1 1 1 s 2015 2016 2016 2017 2017 2018 2018 2019 2015 2016 2016 2017 2017 2018 2018 2019 1.6 Dec-31 Jul-01 Dec-31 Jul-01 Dec-31 Jul-02 Dec-31 Jul-02 1.6 Dec-31 Jul-01 Dec-31 Jul-01 Dec-31 Jul-02 Dec-31 Jul-02 40° < Q < 50° Q > 50° 1.5 y 1.5 y 1.4 1.4 1.3 1.3 1.2 1.2 1.1 1.1 1 1 2015 2016 2016 2017 2017 2018 2018 2019 2015 2016 2016 2017 2017 2018 2018 2019 Xin Wu Dec-31 Jul-01 Dec-31 Jul-01 Dec-31 Jul-02 9thDec-31 DAMPEJul-02 Workshop,Dec-31 15/06/2019Jul-01 Dec-31 Jul-01 Dec-31 Jul-02 Dec-31 Jul-02 23 Very stable operation • Basically no important down time for 46 months and counting … Energy bins DAC calibration STK threshold update HV reset ~5.2 M events recoded per day More than 7 billion events collected Skimmed datasets: number of events per energy interval very stable Xin Wu XSCRC2019, 14/11/2019 24 Proton flux • Published in 17 September 2019 in Science Advances (Sci.