GLAST Proposal Review - Welcome to SCIPPscipp.ucsc.edu/outreach/hartmut/Pubs/F2k_GLAST_Rad_T.pdf ·...

F2k : GLAST Hartmut F.-W. Sadrozinski , SCIPP, UC Santa Cruz

RadiationIssues inGLAST Si

ScienceDesign of ChallengesRadiation Issues

Hartmut F.-W. SadrozinskiSanta Cruz Institute for Particle Physics (SCIPP)


GLAST Gamma-Ray Large Area Space TelescopeAn Astro-Particle Physics Partnership Exploring the High-Energy Universe

• Precision Si-strip Tracker (TKR)• Hodoscopic CsI Calorimeter (CAL)• Segmented Anticoincidence Detector (ACD)• Advantages of modular design• NASA, DoE, DoD, INFN/ASI, Japan, CEA, IN2P3, Sweden

Challenges of Science in Space

• Launch

• Limited Resources• Space Environment

4 x 4 Arrayof Towers

AnticoincidenceShield

CalorimeterModule

Grid

TrackerModule

GammaRay

Resolving the γ-ray sky

Design Optimized for Key Science Objectives

• Understand particle acceleration in AGN, Pulsars, & SNRs• Resolve the γ-ray sky: unidentified sources & diffuse emission• Determine the high-energy behavior of GRBs & Transients

Proven technologies and 7 years of design, development and demonstration efforts


GLAST Detector Concept: Pair Conversion Telescope

γ

e+ e- calorimeter (energy measurement)

particle tracking detectors

conversion foils

charged particle anticoincidence shield

1x10-6

1x10-5

1x10-4

1x10-3

1x10-2

1x10-1

1x100

1x101

1x10-3 1x10-2 1x10-1 1x100 1x101 1x102 1x103 1x104 1x105

phot

on a

ttenu

atio

n le

ngth

(cm

)

Energy (MeV)

photoelectric Compton pair-conversion

Photon attenuation in lead

1

2


Science capabilities - sensitivity

200 γ bursts per yearprompt emission sampled to > 20 µs

AGN flares > 2 mntime profile +∆E/E ⇒ physics of jets and acceleration

γ bursts delayed emission

all 3EG sources + 80 new in 2 days

⇒ periodicity searches (pulsars & X-ray binaries)⇒ pulsar beam & emission vs. luminosity, age, B

104 sources in 1-yr survey⇒ AGN: logN-logS, duty cycle,

emission vs. type, redshift, aspect angle⇒ extragalactic background light (γ + IR-opt)⇒ new γ sources (µQSO, external galaxies, clusters)

1 yr

100 s

1 orbit

1 day

3EG limit

0.01

0.001

LAT 1 yr2.3 10-9

cm-2s-1

large field-of-view


Science: High-Energy Behavior of GRBsImportant GLAST properties for achieving science objectives:

• Large area• Low instrument deadtime (20 µs)• Energy range to >300 GeV• Large FOV

Expected Numbers of GRBs and Delayed Emission in GLAST

GLAST will probe the time structure of GRB’s to the µs time scaleSpectral and temporal information might allow observation of quantum gravity effects.

Time between detection of photons


Science: Acceleration in AGN, Pulsars, & SNRsMulti-wavelength Observations are crucial for the understanding of Pulsars and AGN’s. Flares are largest at high energy.

Overlap of GLAST with ACT’s provides Needed energy calibration.

Crab

Mk 501

Synchrotron Radiation Inverse Compton

Flares


Instrument Performance

(Single Source F.o.M ~ Aeff /[σ(68%)]2)

FOV: 2.4 srSRD: 2.0 sr


Optimization of Converter Thickness t

0

500

1000

1500

2000

2500

0 5 10 15

Effective Area vs. Conversion Plane

Graded Converter (2.5%, 25%)Uniform Converter (3.5%)

x-y Plane

0.01

0.1

1

10

0.01 0.1 1 10 100

Gamma Angular Resolution PSF(68)

68% Front68% Back

Gamma Energy [GeV]

Aeff ~ t

PSF(68) ~ √t

For Background limited Sources:(Significance) = Aeff / PSF(68) 2

is independent of Converter Thickness

For High Latitude Sources:Number of detected gamma’s count.

0.9038%26%4Back

0.3938%3.8%12Front

PSF(68)@1GeV

[o]

γConversion

X0 per Layer

# of Layers


Overview of TKR Baseline Design

• 16 towers, each with 37 cm × 37 cm of Si (78m2 in all)

• 18 x,y planes per tower– 19 “tray” structures

• 12 with 2.5% Pb on bottom• 4 with 25% Pb on bottom• 2 with no converter

– Every other tray rotated by 90°, so each Pb foil is followed immediately by an x,yplane

• 2mm gap between x and y• Electronics on the sides of trays

– Minimize gap between towers– 9 readout modules on each of 4 sides

• Trays stack and align at their corners• The bottom tray has a flange to mount on

the grid• Carbon-fiber walls provide stiffness and

the thermal pathway to the grid

One Tracker Tower Module

Electronics flex cables

Carbon thermal

panel


Silicon-Strip Detectors

• 400 µm thick, single sided• 8.95 cm × 8.95 cm (6” wafers)• Strip pitch: 228 µm• AC coupled with polysilicon bias

(~60MΩ)• Qualify Prototypes from HPK

• GLAST Needs:• ~10k detectors from 6” wafers

• ~ 1M readout channels

• > 5M bonds

DC Pads80 x 80

AC Pads80 x 150

BiasResistors

Pads for BypassAl Traces80x150

Guard RingBias Ring

Pitch194

Bypass strip

Schematic layout of the detector. • Bypass strips will not be used.• DC pads will increase in size.• A second AC pad will be added on

each strip, for probing and for a second chance at wire bonding.

F2k : GLAST Hartmut F.-W. Sadrozinski , SCIPP, UC Santa CruzTracker of the Beam Test Engineering Module

End of one readout hybrid.

BTEM Tracker Module with side panels removed.

Single BTEM Tray

The BTEM Tracker, (~1/16 of the flight instrument) for the SLAC test beam (11/99 – 1/00)

- 2.7m2 silicon, ~500 detectors, 42k channels- all detectors are in 32 cm long ladders.

Si Detectors

HPK 296 (4”), 251 (6”)

Micron 5 (6” ) Leakage I: 300 nA/detector (HPK)

Bad strips: about 1 in 5000


Assembly of BTEM Tracker at SCIPP

4 trays, 10 eyes & 10 hands

17 trays!

2 delicate hands

2 trays and 2 observers

All done and all smiles.


Challenge #1 : Space Environment and Launch

BTEM TKR tray undergoing random vibration testing at GSFC.

Vibration Testing of a live tray up to 14g.Leakage current before and after shaking identical

Space Qualification:Assembly Methods

MaterialsTests

Aluminum and carbon-fiber mechanical model

of 10 stacked tracker trays, used by Hytec,

Inc. to validate the design in vibration tests.

FEM analysis of (a) TKR tray deflections and (b) of a complete TKR module. Fundamental frequencies are above 550 Hz for the tray and 300 Hz for the module, clamped only at its base.


Challenge #2: On Board Cosmic Ray Rejection

Diffuse High Latitude gamma-ray flux

C.R. Rejection needed 105 : 1 segmented ACD segmented CAL segmented TRK

Radiation Levels: 1krad in a 5year missionIssue: SEE from Heavy Ions (SEU & Latch-up)See below

LVL1 : 5kHzDownlink: 30Hz


Challenge # 3: 1M channels, 250W Power See Takanobu Handa’s Poster

Boss for mechanical and thermal attachment to the wall.

28 Amplifier chips

TermResis4 layers of 1/2 oz coppTEM

needs shielding around cable.

Digital Analog

Cross-over into the side arms

Bias + Analog 3.3VAnalog GroundAnalog 1.5V

Digital 3.3VDigital GroundLVDS Signals

Kapton Cable down the Tower Walls

Redundant, ultra-low power, low-noise FEE

Hybrid:

Electrical & mechanical Challenge

Digital readout controller chip at each end

25-pin Nanonics connector


0 200 400 600 800 1000 1200 1400

10-5

Strip Number

Layer 6x

Occ

upan

cyChallenge #4: Tracker Noise and Efficiency

• Noise occupancy determines the noise rate of the LVL1 trigger, a coincidence of 6 OR’dlayers.

• Noise RMS σ = 130 + 21*C/pF [e-] , τ =1.3µs• Hit efficiency was measured using single

electron tracks and cosmic muons.• The requirements were met: 99% efficiency

with <<10−4 noise occupancy.0 200 400 600 800 1000 1200 1400

Threshold (mV)

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

Effi

cien

cy

Layer 10 xLayer 10 y

1 2 3 4 5Detector Ladder

95

96

97

98

99

100

101

Hit

Effi

cien

cy

Layer 6xCosmic RaysElectron Beam

Noise occupancy and hit efficiency for Layer 6x, using in both cases a threshold of 170 mV. Nochannels were masked.

Hit efficiency versus threshold for 5 GeV positrons.

100,000 triggers


Space Environment: RadiationGLAST is in a Low-Earth Orbit (550km):

Shielding of Atmosphere and magnetic Field Avoid (most!) of the radiation belts

Orbit co-determined by Re-entry > 10 Years, < 30years.

USA on ARGOS

Radiation Belts: - High LatitudeSouth Atlantic Anomaly (SAA)-Trapped electrons and protons

responsible for Total Dosecause huge trigger rate(Detectors will be switched off)

Outside radiation Belts:Charged Cosmic Ray Background (p, e, heavy ions) Responsible for Single Event Effects (SEE)


Long-term Radiation Damage:

Entirely given by electron and proton flux trapped in the SAA

Extremely soft spectrum: Self shielding of Instrument:Blanket, ACD, walls: 2.50g/cm2

Cut-off at 80MeV protons

Radiation: Total Dose & Displacement

0

5

10

15

20

25

30

0 5 10 15 20 25 30

GLAST Silicon Tracker End-of-Mission Signal-to-Noise

S/N E-o-M 1x

S/N E-o-M 5x

Temperature [deg C]

Total Dose 1kRad (5 yrs) -NASA safety factor: 5x-Leakage current increase 50% surface, 50% bulk(same temperature dependence).

Increase in shot noise due to radiation constrains operating temperature to below 25oC.

1

10

100

1000

10000

100000

0.01 0.1 1 10

ElectronsBremsstrahlungProtonsTotal

Full dose - Spherical shield550 km 28° circular orbit

5-year mission - Solar Minimum

Depth (g/cm2 Al)


Heavy Ion Radiation: Temporal Effects (SEE)Linear Energy Transfer LET governs Single Event Effects: SEU, SEL, Punch Through LET is dE/dx: LET (Min ion) ≈ 1.3*10-3 MeV/(mg/cm2), LET ~ Z2 : LET (Fe) ≈ 1-2 MeV/(mg/cm2).

Fe

GLAST IRD

Update from AMS


Heavy Ion Radiation: Single Event Upset

Credit: http://www.aero.org


Silicon Detectors in High Radiation Fields

Past Problems— beam loss LEP (CERN) ALEPH/Babar detector shorted out due

to beam loss; unexpected large voltageacross coupling capacitance

Future (?) Problems—High Luminosity colliders (BaBar, ATLAS)

prepare for large ionization in Siliconmicrostrip detectors either from beamloss or minimum bias particles

Detectors in Space(?) (GLAST)

heavy ions (Fe) will have ionization power of 1000’s of minimum ionizing particles

• Beam loss is measured in fluence [MIPs / cm2] or total absorbed dose(Si) [Rad]

• In 300µm thickness 1 Rad = 106 MIPs/ cm2

• Detectors are designed for MIP signal: 1MIP = 4fC = 24,000 electron-holes pairs

• Detectors might not be optimized for high radiation field


GLAST Challenges from Radiation

Total Dose and Displacement requirements are modest, but shot noise increase is noticeable due to detector length and long shaping time.Limit on operating temperature.

SEE is more demanding and need careful testing. Tests with lasers and heavy ion beams needed to make sure that SEE is not a problem.

Choice of CMOS technology helps: either SoI or HP 0.5um are attractive.SEU hardened design and SEL resistant design are fallback.

SEU: Frequent refreshing of registers advisable.

Detectors are susceptible to breakdown for large LET.Specify coupling capacitors for full operating voltage.


GLAST Development Process and Status

Date Activity Program

93-98 Conceptual study NASA SR&DDetector R&D DoE R&D

(Beam Test 1998)98 DoE Review SAGENAP

Endorsement98-00 Technology NASA ATD

Development (BTEMFull Size ModulesManufact. ProcessASIC’s, DAQ)

Fall 99 Instrument Proposal NASA AO GLAST Base LIne(Si TKR, CsI CAL, ACD)Endorsements, MoA

Feb 25, 00 Decision on AO GLAST-LAT selected

Sept 2005 Launch on Delta 2

What New Worlds are we going to see?

GLAST Proposal Review - Welcome to SCIPPscipp.ucsc.edu/outreach/hartmut/Pubs/F2k_GLAST_Rad_T.pdf ·...

Documents

Transcript of GLAST Proposal Review - Welcome to SCIPPscipp.ucsc.edu/outreach/hartmut/Pubs/F2k_GLAST_Rad_T.pdf ·...