Space Applications: Overview

September 15, 2006 R.P. Johnson 1

Space Applications: OverviewSpace Applications: Overview

Robert P. Johnson

Santa Cruz Institute for Particle Physics

Physics Department

University of California at Santa Cruz

September 15, 2006 R.P. Johnson 2

OutlineOutline• Tracking detectors

– Pamela

– AMS

– Agile

– GLAST

• Compton telescopes– MEGA

– ACT

– Si/CdTe concept (see earlier talk by Shin Watanabe)

• Focal-plane detectors—well covered later in this session and also in early sessions– Ground based (see talk by Richard Stover in this session)

– LSST (see talk by Steve Kahn in this session)

– JDEM/SNAP (see talk by Chris Bebek in this session)

– MAXI (see talk by Hiroshi Tsunemi in this session)

I will restrict this talk to the use of silicon-strip tracking systems in space. There are by now several examples of HEP-like experiments built for operation in orbit.

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PamelaPamela

Cosmic-ray spectrometer; antimatter search.

Permanent magnet: ~0.4 T

Measure antiprotons up to 190 GeV.

Silicon-strip tracker.

Launched earlier this summer from Baikonur.

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PamelaPamelaPamela completed its instrument checkout in early July and is now taking science data.

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Pamela Silicon-Strip TrackerPamela Silicon-Strip Tracker• Double-sided, double metal, AC-

coupled• 6 planes of 3 ladders each• 300 m thick; 7.0×5.3 cm2 area• 50 m readout pitch• 4 m resolution in bending plane,

15 m in the non-bending plane• 90% efficiency per plane for MIP

• VA1 chip used for readout

• 62 W power consumption

• ~ 3 mW/channel

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Alpha Magnetic SpectrometerAlpha Magnetic Spectrometer• Cosmic-ray

spectrometer.• Antimatter search.• Dark matter search.• Superconducting

magnet (0.97 T).• Silicon-strip tracker.

Complex particle physics detector for operation in orbit!

Destined for the completed space station, which makes its schedule very uncertain at this time.

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AMS Silicon-Strip TrackerAMS Silicon-Strip Tracker• Double-sided, 300 m thick silicon strip detectors.

• Arranged in 8 layers on 5 support planes; 192 ladders (6.45 m2 of Si).

• AC coupled to VA-hdr9a chips via capacitor chips (700 pF).

• (1284+384)×192=320,256 readout channels.

• 10 micron resolution in bending plane (30 micron out of plane).

• 734 W/320,256=2.3 mW of power per channel (~0.7 mW/ch in the VA chip).

• Active cooling with CO2.

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AMS Silicon-Strip TrackerAMS Silicon-Strip Tracker• Honeycomb support plane with ladders installed on the top side.

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AGILEAGILE• Gamma-ray (pair-conversion tracker), with about 4 m2 of Si strips

• Hard X-ray imaging (coded mask)

• To be launched on a PSLV rocket from the Sriharikota base in India – Currently held up by U.S. State Dept. (mindless ITAR issue)

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AGILE Tracker/ConverterAGILE Tracker/Converter• Single sided SSDs, AC coupled, 9.5×9.5 cm2, 410 m thick

• 121 m strip pitch; 242 m readout pitch; 38-cm long strips in ladders

• Analog readout by the 128-channel TAA1 chip (IDEAS)– 0.4 mW/channel in front end

• 36,864 readout channels in 24 layers (12 x,y pairs)

• Silicon ladders bonded to top and bottom of composite “trays”

• 0.7 X0 tungsten converter foils on the bottom surfaces of the top 10 trays

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Super AGILESuper AGILE• Hard x-rays (15 to 45 keV)• Silicon-strip plane placed 14-cm below a coded tungsten mask• 6 arc-minute angular resolution, from 121 m strip pitch• 19-cm long silicon strips read by XAA1.2 chips; 410 m thick• 6144 channels

Collimator

SSDs

Coded Mask

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Super AGILESuper AGILE• 30 pF channel• Sensitivity: ~0.01 Crab in a 14-hour exposure• Energy resolution ~5 keV FWHM • 300 cm2 effective area on axis (~20% of the geometric area)

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GLAST Large Area TelescopeGLAST Large Area TelescopeSi Strip Tracker/Converter

– 36 single-sided Si layers

• 228 m pitch; 400 m thick

• 8.95 cm square SSDs

• AC coupled

– 16 tungsten layers

– 884,736 channels

– 160 W

– Self triggering

Fairly large HEP detector to operate in orbit:• 3 ton mass (allocated)• ~ million channels• 3 detector subsystems• 5 computers• But only 650 Watts (allocated)!

• 74 m2 of Si in the flight instrument• About $8 per square centimeter

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GLAST SSD Tracker/Converter

Flex-Circuit Readout Cables

36 Multi-Chip Electronics Modules (MCM)

2 mm gap between x,y SSD layers

19 Carbon-Fiber Tray Panels

Titanium Flexure Mounts

Carbon-Fiber Sidewalls (Aluminum covered)

• Carbon-composite structure supports 18 x and 18 y layers of silicon-strip detectors and 16 layers of tungsten converter foils.

• 36 custom readout electronics boards, each with 1536 amplifier channels, mount on the sides of the panels to minimize inter-tower dead space.

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Tracker Mechanical Fabrication Challenges

Top view of 4 Tracker Modules

MCM

1 Tracker Tray

Right-angle interconnect

Very tight space for electronics

High precision carbon-composite structure to maintain 2.5 mm gaps between modules

X-section of tray edge

Tray

Sidewall

<18 mm from active Si to active Si!

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GLAST Tracker ElectronicsGLAST Tracker Electronics

ASIC based, for minimum power (180 W/ch).

Digitize on chip:

No coherent noise or pedestal variation!

Single threshold (0 or 1).

ToT on trigger OR.

Internal calibration system.

Threshold & Cal DACs.

Redundant 20 MHz serial control and readout paths.

4 event buffers at front end negligible deadtime (few s).

GTFE ASICGTRC ASIC

Direct descendent of the BaBar ATOM-based FE system (UCSC/LBNL/INFN).

0.5 m CMOS

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GLAST Tracker StatusGLAST Tracker Status16+2 towers completed.

Flight array fully integrated in completed LAT.

Environmental testing completed at NRL.

Delivery to General Dynamics this month.

Two spare towers in beam testing at CERN.

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GLAST Tracker Performance

• Hit efficiency (in active area) >99.4%

• Overall Tracker active area fraction: 89.4%

• Noise occupancy <5×107

• (with small number of noisy channels masked)

• Power consumption 158 W (178 W/ch)

• Time-over-threshold 43% FWHM

Muon time-over-threshold (OR of all channels per layer)

Threshold variation <9% rms in all modules

(5.2% on average)

Strip #, 1 to 1536Strip #, 1 to 1536

Hit efficiency from cosmic-ray muonsHit efficiency from cosmic-ray muons

1 example readout module1 example readout module

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Cosmic-Ray Gamma Conversions in 8 Towers

Launch in autumn 2007

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Compton TelescopesCompton Telescopes• Two general concepts have been competing for the next

generation detector, to improve upon Comptel:– Classic: measure energy loss, direction, and total energy– e tracking: add measurement of the electron direction

• Also capable of fully measuring pair conversions.– 3-Compton: measure 1 scattering angle and 2 energy losses

Classic:Comptel

3-Compton:ACT, NCT, LXeGRIT

e tracking:MEGA,TIGRE

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NRL Advanced Compton TelescopeNRL Advanced Compton Telescope• 7 mm thick Si (Li

drifted) detectors (alternative to Ge)

• ~300 V bias

• 1010 cm2 wafers

• 4×4 arrays, stacked 24 deep

• Cooled to 40C• 4 of these towers

are proposed for the complete instrument

• Improve on the Comptel sensitivity by factor of ~100

See also the talk in this conference by Mark Amman on the alternative Ge strip detectors.

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MEGAMEGA

Prototype:– 11 layers of 3×3 array of 6-cm square wafers, each 500 m thick.– 470 m strip pitch– 1 cm spacing between layers– calorimeters with 0.5-cm square CsI scintillators, 8-cm deep, with PIN diode

readout

Satellite concept:– 32 silicon layers– 6×6 array of 6-cm wafers in

each layer– calorimeter surrounding the

lower hemisphere, 8-cm thick on the bottom and 4-cm thick on the sides

– drift diode readout– Good sensitivity from 0.5 MeV

to ~100 MeV, using both Compton scattering and pair conversion.

See also the talk by Shin Watanabe (Si/CdTe Compton telescope concept) in this conference for another interesting example.

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ConclusionConclusion• We are starting to see HEP-like solid-state tracking detectors

put into orbit, with 105 to 106 channels.– AMS-1 (shuttle flight) and Pamela (in orbit)

– AGILE and GLAST are close to launch

• The detector systems and DAQ are relatively simple or small compared with state-of-the-art ground-based detector systems, but the environment (rocket ride, power, thermal, QA) is challenging.– Many lessons learned by these groups that could/should be applied

to future projects

• There is a lot of scientific and technical interest in a large Compton telescope, but unfortunately no major mission in sight at this time.