the silicon-tungsten tracker of the dampe mission...for both angle of incidence and impact position....

The Silicon-Tungsten Tracker

of the DAMPE MissionPhilipp 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)

Philipp Azzarello HSTD10 29.9.2015 2

Neutron Detector

Plastic Scintillator Detector

Silicon-Tungsten Tracker (STK)

BGO Calorimeter

Launch: Mid Dec. 2015

W converter + thick calorimeter (total 32 X0) + precise tracking + charge measurement ➠high energy γ-ray, electron and CR telescope

Detection of 5 GeV - 10 TeV e/γ, 100 GeV -100 TeV Cosmic Rays

Complementary to Fermi, AMS-02, CALET, ISS-CREAM

The Silicon-Tungsten Tracker (STK)

• Detection area 76x76 cm2

• Outer envelope 1.12 m x 1.12 m x 25.2 cm• Total weight: 154.8 kg• Total power consumption: 85 W


Main tasks:• Track reconstruction• Photon detection• Charge measurement

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 X0 for photon conversion• 8 readout boards on 4 sides (IHEP)• Total 192 modules


STK Silicon Sensors • Single-sided Silicon strip detectors produced by Hamamatsu

• 9.5 x 9.5 cm2, 768 strips, 121 µm pitch (AGILE geometry) • 320 µm thick (AGILE: 410 µm) • Resistivity 5-8 kΩ, Vfd 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• ~120 nA @150V (spec:

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


Silicon Ladder Assembly• Precise jigs to assemble (align, glue and bond) 4 sensors to form a ladder


Silicon Ladders


• Alignment precision required: 20 μm • 97% of ladders < 10 μm

Total leakage current for the 192 installed ladders is excellent

Support TraysCFRP plate top

Al honeycomb

CFRP frame

Tungsten plates

CFRP plate Bottom

2 CFRP plates of 0.6 mm (or 1 mm for trays with W plates) thick

4 L-Shape structures in T300 fiber toform the main outside frame.With stainless inserts to connect theTRB frames and the corner feet, andaluminum insert for tray staking

1 aluminum honeycomb core (37 kg/m3)


Tracker Plane• 16 ladders glued to each surface of the support trays (except top and bottom)


Engineering and Qualification Model (EQM)• An EQM has been constructed in 1st 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


Flight Model Assembly• The Flight Model assembly has been completed in April 2015

• Tested with cosmic rays before delivered to China


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 (

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.


Signal identification


Cluster identification: • high threshold 4*noise• Low threshold 1.5*noise

Seed threshold

Charge collection


Charge distribution for particles hitting perpendicularly the ladder

For the particles passing close to the floating strip, the collected charge is about 70% of 1-strip clusters.

Cluster size for different incidence angles

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


• 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.

Charge collectionangle = 0° angle = 30°

angle = 60°

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°

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


The Silicon-Tungsten Tracker �of the DAMPE MissionDAMPE (DArk Matter Particle Explorer)The Silicon-Tungsten Tracker (STK)STK Layout and StructureSTK Silicon Sensors STK Readout Electronics Silicon Ladder AssemblySilicon LaddersSupport TraysTracker PlaneEngineering and Qualification Model (EQM)Flight Model AssemblyFlight Model StatusLadder test beamSignal identificationCharge collectionCharge collectionCharge collectionSpatial resolutionSummary

the silicon-tungsten tracker of the dampe mission...for both angle of incidence and impact position....

Documents