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


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.


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.


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


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


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.


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.


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


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)


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


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


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)


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


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.


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!


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


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.


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


Cosmic-Ray Gamma Conversions in 8 Towers

Launch in autumn 2007


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


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.


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.


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.

space applications: overview

Documents

kevsiliconstrip plane

strip pitch19

thick silicon strip

use of silicon

strip tracking systems

long silicon strips

earlier talk

readout channels