Silicon Tracker and Space Mission Heritage of DPNC
Xin Wu
Département de Physique Nucléaire et Corpusculaire University of Geneva
ASTROGAM Workshop, 9-10 December, Rome
2 Xin Wu
• Leading institute in many large area silicon trackers
– L3 SMD (DSSD, ~1993)
– AMS-01 (DSSD, ~1996), AMS-02 (DSSD, ~2006)
– ATLAS-SCT (SSSD, ~2005)
– LOFT (SDD, ~2013, pre-study)
– ATLAS-IBL (PIXEL, 2014)
– DAMPE-STK (SSSD, 2014-2015)
• Expertise cover almost all aspects of silicon tracker
– Sensor characterization: probe station, cosmic test stand, CERN test beams
– Front-end hybrid: design of rigid+flex for the analogue readout chain
– Readout electronics: FE control, digitization, data compression, trigger
– Module/ladder: design, assembly (gluing and bonding)
– Light support structure: design, FEA study, production
– Tracker integration: design of gigs and procedure, final integration
– Space qualification: vibration, thermal, thermal-vacuum
– Simulation and commissioning
– Not specialized: front-end ASIC design and sensor fabrication
Long Tradition in Si Trackers
3 Xin Wu
• 100 m2 class 10’000 clean room
• 100 m2 class 100’000 clean room
• Automatic probe station
• Mitutoyo 3D measuring machine for large components
• Wire bonding machine and wire bond pull tester
• Flip chip and bump-bonding machine (June 2015)
• Humidity-controlled thermal chamber
• CNC machines
• Qualified and trained personnel
– Centralized mechanical and electronic groups and clean room crew
• Very broad knowledge base
– Experienced in international collaboration and space projects
DPNC Infrastructure
5 Xin Wu
• Complex ladder structure due to double-sided readout
AMS-02 Ladder
Collaboration with INFN Perugia
The DAMPE Detector
7
Plastic Scintillator Detector
Silicon-Tungsten Tracker
BGO Calorimeter
Neutron Detector
Xin Wu
W converter + thick calorimeter (total 32 X0)
+ precise tracking + charge measurement ➠
high energy g-ray, electron and CR telescope
STK
• 12 layers of silicon micro-strip detector mounted on 7 support trays
– Tray: carbon fiber face sheet with Al honeycomb core
• Tungsten plates integrated in trays 2, 3, 4 (from the top)
– Total ~1 X0 for photon conversion
• 8 readout boards (TRB) on 4 sides
8 Xin Wu
Detection area 76 x 76 cm2
DPNC, Perugia, IHEP, Bari
Proposed and led by DPNC
• Weight: ~ 160 Kg
• Total power consumption: ~85W
Si Layer and Ladders CFRP plate Top
Al honeycomb
CFRP frame
Tungsten plates
CFRP plate bottom
Silicon detectors
VA140 (front end chip)
12 layers, 6-x and 6-y
192 TFHs
and Ladders
768 silicon
strip detector
Total ~7m2 Si
1152 ASICs (VA) Xin Wu 9 73728 channels (>500k wire-bonds)!
Wire bonding
• Precise jigs to assemble (align, glue and bond) 4 sensors to a ladder
– 20 µm alignment precision and planarity
Xin Wu 11
15 Xin Wu
• DPNC plays leading roles in several major space missions
– With a healthy pipeline of projects in different stages
• AMS-02: in operation since 2011, continue to at least 2020
– General purpose detector with magnetic spectrometer
• POLAR: in construction, launch in 2015
– First measurement of polarization of gamma ray bursts
• DAMPE: in construction, launch in 2015
– Thick calorimeter with tracker/converter: precise measurements of electron/gamma up to 10 TeV and cosmic rays up to 100 TeV
– DM search, CR physics and gamma-ray astronomy
• LOFT
– Front end module assembly. To be resubmitted to M4
• HERD: in design, launch expected ~2020
– Next generation large detector, up to PeV for CR, also DM search and
gamma-ray astronomy
• PANGU: proposal for the ESA-CAS joint small mission
– g-ray telescope with unprecedented angular resolution in sub-GeV range
DPNC Participation in Space Missions
A High Resolution Gamma-Ray Space Telescope Xin Wu1 (European PI) and Jin Chang2* (Chinese PI)
for the PANGU Collaboration 1DPNC, University of Geneva, Switzerland
2Purple Mountain Observatory, CAS, China
PANGU 盤古
Second Workshop on a CAS-ESA Joint Scientific Space Mission 23-24 Sept. 2014, Copenhagen
1°
Limit due to nuclear recoil
arXiv:1311.2059 [astro-ph.IM]
Co
mp
ton
do
mai
n
Angular resolution of pair telescopes
17 X. Wu/J. Chang
PANGU: both tracks in spectrometer
PANGU: both tracks in target
• Geant4 simulation with 150 µm thick single-sided Si detector, 242 µm pitch
⟹ position resolution ~70 µm
• Results are very preliminary
Very limited energy measurement if no tracks in spectrometer • indication of energy with opening
angle and dE/dx in tracker
PANGU Detector Concept
18 X. Wu/J. Chang
• PANGU: dedicated pair telescope with thin tracking layers and no converter
– Push the “thinness” to the limit for best PSF!
• Silicon SSD of 150µm, or ribbon of 3-4 layers of f=250µm fiber
70 cm
30
cm
PANGU ~100 kg
The Target-Tracker
19 X. Wu/J. Chang
• Possible layout
– x-y double layers with 6mm inter-distance, 50 double layers
• Tracking layer with ~0.3% X0 total (requirement)
– Silicon: 2 single sided SSD of 150 µm each
– SciFi: 2 layers of ~0.65 mm each (Polystyrene equivalent), each layer formed by a stack of 3 layers of ø=250 µm fibers, readout by SiPM
• Total tracker active material
– Silicon: ~17kg (silicon density ~2.33 g/cm3)
– Fiber: ~25kg (polystyrene density ~0.9 g/cm3)
• Both need support substrate
– Probably more for Si: biasing, bonding, more fragile
• Baseline: ~50kg for fiber/silicon, support structure, FE electronics
– Plus: 30 kg for magnet, 20 kg for the rest (ACD, DAQ, …)
⟹ total weight ~100 kg
CAS-ESA workshop, 23-24/09/14
20 X. Wu/J. Chang
PSF Comparison with Fermi
PANGU: both tracks in spectrometer
PANGU: both tracks in target
CAS-ESA workshop, 23-24/09/14
Energy [MeV]
10 2103
10
sr]
2A
cce
pta
nce
[cm
210
310
410
Both tracks in target
At least 1 track in spectrometer
Both tracks in spectrometer
Half-sphere downward isotropic incidence
21 X. Wu/J. Chang
Acceptance Compared to Fermi
Fermi
CAS-ESA workshop, 23-24/09/14
Polarisation Measurement
22 X. Wu/J. Chang
• Azimuthal angle distribution in the plane perpendicular to the g direction
– Pg: degree of polarisation; fpol: polarisation direction
– A: Analyzing power, ~0.2 for pair production but kinematic dependent
ds dj = 2ps 0 1+Pg × A×cos(2j -2jpol )( )
• Keys to the measurement
– Azimuthal angular resolution
• transverse track length and multiple scattering
– Intrinsic modulation of the detector!
[Deg]electron
f
-150 -100 -50 0 50 100 150
Fra
ctio
n
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07true reco
true reco
true reco
true reco
Unpolarised input
° = 0qincidence angle
Photon energy (MeV)
50
100
400
600
Detector Intrinsic Modulation
23 CAS-ESA workshop, 23-24/09/14 X. Wu/J. Chang
• Detector intrinsic modulation because of bad f resolution when particle goes in parallel to the strip direction
Intrinsic modulation energy dependent!
More important for higher energy because of smaller
opening angle ⟹ shorter transverse track length
Intrinsic modulation is a function of photon direction Best with normal incidence!
[Deg]lead
f
-150 -100 -50 0 50 100 150
Fra
ctio
n
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07true reco
true reco
true reco
true reco
Unpolarised input
° = 0qincidence angle
Photon energy (MeV)
50
100
400
600
Intrinsic Modulation, Leading Track
24 CAS-ESA workshop, 23-24/09/14 X. Wu/J. Chang
• Electron cannot be identified If no tracks reached spectrometer
– Use leading track
Variable and selection for optimal
PgA should be further studied
[Deg]electron
f
-150 -100 -50 0 50 100 150
Fra
ctio
n
0
0.01
0.02
0.03
0.04
0.05
0.06
unpolarisedA = 0.1gP
A = 0.2gP
A = 0.5gP
Modulated input
° = 0pol
q
° = 0q100 MeV, incidence angle
Input Modulation, Electron
25 CAS-ESA workshop, 23-24/09/14 X. Wu/J. Chang
• Possibility to detect input modulation
– Important to model intrinsic modulation!
– Need reliable simulation code for polarised pair production
Input f distribution modulated with fixed PgA
[Deg]lead
f
-150 -100 -50 0 50 100 150
Fra
ctio
n
0
0.01
0.02
0.03
0.04
0.05
0.06
unpolarisedA = 0.1gP
A = 0.2gP
A = 0.5gP
Modulated input
° = 0pol
q
° = 0q100 MeV, incidence angle
Input Modulation, Leading Track
26 CAS-ESA workshop, 23-24/09/14 X. Wu/J. Chang
Input f distribution modulated with fixed PgA
• Possibility to detect input modulation
– Important to model intrinsic modulation!
– Need reliable simulation code for polarised pair production