The Silicon-Tungsten Tracker of the DAMPE Mission Philipp Azzarello, DPNC, University of Geneva for the DAMPE-STK collaboration 10th International Hiroshima Symposium on the Development and Application of Semiconductor Tracking Detectors
DAMPE (DArk Matter Particle Explorer) Plastic Scintillator Detector Silicon-Tungsten Tracker (STK) BGO Calorimeter Launch: Mid Dec. 2015 Detection of 5 GeV - 10 TeV e/γ, 100 GeV - 100 TeV Cosmic Rays Complementary to Fermi, AMS-02, CALET, ISS-CREAM Neutron Detector W converter + thick calorimeter (total 32 X 0 ) + precise tracking + charge measurement high energy γ-ray, electron and CR telescope Philipp Azzarello HSTD10 29.9.2015 2
The Silicon-Tungsten Tracker (STK) Main tasks: Track reconstruction Photon detection Charge measurement Detection area 76x76 cm 2 Outer envelope 1.12 m x 1.12 m x 25.2 cm Total weight: 154.8 kg Total power consumption: 85 W Philipp Azzarello HSTD10 29.9.2015 3
STK Layout and Structure 12 layers of silicon micro-strip detector mounted on 7 support trays Tray: carbon fiber face sheet with Al honeycomb core Tungsten plates (1mm thick) integrated in trays 2, 3, 4 (from the top) Total ~1 X 0 for photon conversion 8 readout boards on 4 sides (IHEP) Total 192 modules Philipp Azzarello HSTD10 29.9.2015 4
STK Silicon Sensors Single-sided Silicon strip detectors produced by Hamamatsu 9.5 x 9.5 cm 2, 768 strips, 121 µm pitch (AGILE geometry) 320 µm thick (AGILE: 410 µm) Resistivity 5-8 kω, V fd 10-80 V Total strip capacitance 2.1 pf/cm 150 SSDs for EQM (Engineering and Qualification Model) 865 SSDs for FM (Flight Model) Excellent quality <I leak > ~120 na @150V (spec: <900 na) V fd < 50 V Very few bad channels Cut precision: ~ few µm Philipp Azzarello HSTD10 29.9.2015 5
STK Readout Electronics Readout every other strip, readout pitch 242 µm ASIC: VA140 from IDEAS, updated version of VA64hdr of AMS-02 Low power (0.3 mw/channel) and large dynamic range (200 fc) Analog readout Charge measurement Better position resolution with charge sharing Tracker Front-end Hybrid (TFH) Thin bias circuit integrated with a PCB housing 6 ASICs, and a readout cable ( pigtail ) Support structure for the SSDs Vias and copper bands for heat transfer Philipp Azzarello HSTD10 29.9.2015 6
Silicon Ladder Assembly Precise jigs to assemble (align, glue and bond) 4 sensors to form a ladder Philipp Azzarello HSTD10 29.9.2015 7
Silicon Ladders Alignment precision required: 20 μm 97% of ladders < 10 μm Total leakage current for the 192 installed ladders is excellent Philipp Azzarello HSTD10 29.9.2015 8
Support Trays CFRP plate top Al honeycomb CFRP frame Tungsten plates CFRP plate Bottom 1 aluminum honeycomb core (37 kg/m 3 ) 2 CFRP plates of 0.6 mm (or 1 mm for trays with W plates) thick 4 L-Shape structures in T300 fiber to form the main outside frame. With stainless inserts to connect the TRB frames and the corner feet, and aluminum insert for tray staking Philipp Azzarello HSTD10 29.9.2015 9
Tracker Plane 16 ladders glued to each surface of the support trays (except top and bottom) Philipp Azzarello HSTD10 29.9.2015 10
Engineering and Qualification Model (EQM) An EQM has been constructed in 1 st half of 2014 full size model as the final Flight Model (FM), but only 26 ladders with real silicon sensors, the rest with dummy sensors EQM passed a series of space environmental qualification tests: vibration, acceleration, shock, thermal cycling, thermal vacuum Philipp Azzarello HSTD10 29.9.2015 11
Flight Model Assembly The Flight Model assembly has been completed in April 2015 Tested with cosmic rays before delivered to China Philipp Azzarello HSTD10 29.9.2015 12
Flight Model Status Since delivery to China: Passed acceptance level vibration and thermal vacuum tests Integrated into DAMPE final payload, then satellite integration Passed satellite thermal vacuum tests in orbit simulating vacuum chamber EMI tests STK remain stable through the process ~0.3% of channels with noise >5 ADC counts (bulk is ~3 ADC counts) Only 18 (<0.03%) channels out of the 74382 need to be masked Significance: charge/rms Philipp Azzarello HSTD10 29.9.2015 13
Ladder test beam Two STK ladders have been tested using 400 GeV proton beam at CERN Study the spatial resolution dependence with various angles of incidence. Optimize the charge measurements. Telescope of Geneva ATLAS group. Philipp Azzarello HSTD10 29.9.2015 14
Signal identification Seed threshold Cluster identification: high threshold 4*noise Low threshold 1.5*noise Philipp Azzarello HSTD10 29.9.2015 15
Charge collection Charge distribution for particles hitting perpendicularly the ladder Cluster size for different incidence angles For the particles passing close to the floating strip, the collected charge is about 70% of 1-strip clusters. Philipp Azzarello HSTD10 29.9.2015 16
Charge collection When the incidence angle increases, the charge is released among more strips and the two peaks shape becomes less evident. The cluster charge for different angles of incidence is compared with a Monte Carlo simulation Charge sharing simulation is based on a spice model Key parameters: inter-strip capacitance and second neighbor capacitance Philipp Azzarello HSTD10 29.9.2015 17
Charge collection angle = 0 angle = 30 angle = 60 Dependence of the collected charge as a function of the impact point as estimated from the telescope. The strip pitch is of 121 um. The cluster charge has to be corrected for both angle of incidence and impact position. Philipp Azzarello HSTD10 29.9.2015 18
Spatial resolution Thanks to the analog readout the spatial resolution is lower than 80 μm for angles below 60 Spatial resolution lower than 50 μm below 40 Philipp Azzarello HSTD10 29.9.2015 19
Summary The Silicon-Tungsten Tracker (STK) of the DAMPE mission is based on robust technology of single-sided silicon strip detectors with analog readout. It will play crucial roles in charge track reconstruction, gamma-ray detection, cosmic ray charge measurement, and overall particle identification. After 2 years of intensive design, prototyping, testing and production efforts Engineering and Qualification Model was space qualified and tested with particle beams STK Flight Model (FM) completed and passed acceptance and integration tests The quality of the STK is excellent and meets the design specifications Charge collection is studied in terms of impact point and angle of incidence Within the whole acceptance of STK the spatial resolution is below 80 μm and lower than 50 μm below 40 DAMPE will be launched in mid-december 2015 Philipp Azzarello HSTD10 29.9.2015 20