Caratterizzazione spaziale del Tracker di GLAST Silvia Rainò INFN - BARI Incontro Nazionale di...

Caratterizzazione spaziale del Tracker di GLAST

Silvia RainòINFN - BARI

Incontro Nazionale di Astrofisica delle Alte Energie – Roma, 15-16 maggio 2003

Roma, 15-16 Maggio 2003

Incontro Nazionale di Astrofisica delle Alte Energie 2

Overview

GLAST experiment

The Large Area Telescope: GLAST-Tracker

Space tests: results on Engineering Model

Conclusions



Gamma Ray Large Area Space Telescope

GLAST is an important part of the continuing quest to broaden our view of the universe.

explore Nature’s highest energy processes (10 keV – 300 GeV) observe, with unprecedented detail, cosmic phenomena of extreme violence

- LATLAT:: ~20 MeV - >300 GeV

-- GBM GBM:: correlative transient observations ~20 keV – 20 MeV



Glast observatory

Launch Vehicle Delta II – 2920-10HLaunch Location Kennedy Space CenterOrbit Altitude 575 KmOrbit Inclination 28.5 degreesOrbit Period 95 MinutesLaunch Date September 2006

Large Area Telescope (LAT)

Gamma Ray Burst Monitor (GBM)

Spacecraft



Large Area Telescope

4 x 4 modular array3000 kg, 650 W20 MeV – 300 GeVSi Tracker

pitch = 228 m8.8 105 channels18 x-y planes

ACDSegmented scintillator tiles

Gridmechanical backbone

CsI Calorimeterhodoscopic array (8 layers)6.1 104 channels

e+ e-



Large Area Telescope

e+ e-

Single Photon Angular Resolution3.5o @ 100 MeV0.15o @ 10 GeV

Wide Energy Range: 20 MeV - >300 GeV

Wide Field of View(> 2 sr)

Low dead time:< 100 s/event

Large Effective Area(Aeff)peak > 8,000 cm2

Good Energy ResolutionE/E ~ 10%; 100 MeV – 10 GeV ~ < 20%; 10 GeV – 300 GeV

Point Source Sensitivity:< 6 x 10-9 ph cm-2s-1

(est. performance: < 3 x 10-9 ph cm-2s-1)

Source Localization:0.3’ – 1’



Tracker Tower

11 thin-converter trays (3% X0)

4 thick-converter trays (18% X0)

2 no-converter trays

1 bottom tray (no-converter)

1 top tray (converter 3% X0)



Space tests

operate satisfactorily at the temperatures expected during the mission

Thermal tests

Dynamic tests withstand the mechanical solicitation during launch and first orbit phases

Tray Tower TKR

CAL

ACD

LAT



Work in progress

Space test activity now concentrated on the assembly and test of the Engineering Model Tower:

• Test plans have already been defined

• Dynamic test: 12 EM panels successfully tested

• Thermal test: 2 EM trays cycled w/out any damage to silicon

EM Tower Plan Schedule

July 8: EM tower assembled July 22: Vibration testing completed August 5: Thermal-vacuum testing completed



Dynamic test

Frequency range

20 2000 Hz

Sweep rate 2 oct/min

Target Amplitude

0.25 g0-pk

Test Sequence:

1. Modal survey: normal mode search

2. Random vibration

3. (Low frequency test + quasi static acceleration)

4. Modal survey: normal mode checkModal survey:

Low amplitude sine sweep test, performed at the beginning & end of the test sequence

Evaluates the transfer function of the item

Allows to find any structural damage occurred during the test



Dynamic test

Random Vibration:

Allows to study the structural response of the item when subjected to the launch environment

depends on the rocket used for launch

Frequency (Hz)

ASD Qualification Level (g2/Hz)

ASD Acceptance Level (g2/Hz)

20 0.026 0.013

20-50 +6 dB/oct +6 dB/oct

50-800 0.16 0.08

800-2000 -6 dB/oct -6 dB/oct

2000 0.026 0.013

Overall 14.0 grms 10.0 grms



Vib test: experimental set-up

accelerometers

Shake table LDS V864LT @ Centrotecnica s.a.s (MI)



Modal survey EM tray - thin converter type

(W=3%X0)

m 830 g1st resonant mode0 815 Hz

2nd resonant mode0 1860 Hz

ESPI Vibration TEST



Random vibration

EM Trays tested at successively higher excitation levels:

7 grms 10 grms 14 grms

White noise check among two successive random



Thermal tests

1 m3

Climatic chamber in INFN - PG site Terni, Dip. Ingegneria dei Materiali

Strain gauges positioned on the Si surface of the tray

Wheatstone bridge

configuration

Strain gauge on Si

Reference strain gauge on quartz (CTE 0 ppm/°C)

LabView based DAQ system



Thermal test on EM

4 cycles

-30°C ÷ +50 °C

dT/dt = 20 °C/hr

Plateau 5 hr



Thermal test results

ΔTCTEεε Sitransf

L

Lε

strainStrain vs time

= trasf· ESi , ESi= 13 GPa

max= 28 MPa (SF= 7.5)

Stress vs T

T=30°C: 200 12 MPa



Conclusions

Summary Test plans have been developed for all dynamic and thermal tests

on trays and towers and are in the release cycle now

Positive results for the tests on EM trays

Further work June-July 2003: assembly and test of EM tower:

Dynamic and thermal-vacuum in Alenia Globalstar, Rome Revise flight test plans with updated information resulting from EM

tests

Assembly & test of Flight items (October 2003 ):

Test on 342 trays

Cosmic rays test

Assembly & test of 18 towers (16 flight+ 1 qual + 1 spare)



Tracker Tray

SSD’s

Bias-Circuit

Structural Tray Panel

Converter Foils

TMCM

Bias-Circuit

SSD’s



Tray Test flow overview

Tray factory (panels)

Vibration test

Ladder factory

Tray assembly: ladders and MCMs on trays

Tray thermal cycles

Stacked cosmic rays

Electrical test

Tray functional test

Tower assembly

Electrical test before MCMs

encapsulation



Cosmic rays test

Tray stacked in single/double view



Tower Test Flow Overview

Tower functional test

Vib test sequence

Tower functional test

Thermal-vacuum & functional test

Tower assembly

Sine sweep

Random vib

Quasi static

Sine burst

Sine sweep



Tower vib levels

Frequency (Hz)

ASD AcceptanceLevel (g2/Hz)

ASD Qualification

Level (g2/Hz)

20 0.01 0.02

20-50 +5.9 dB/oct +5.9 dB/oct

50-800 0.06 0.12

800-2000 -5.9 dB/oct -5.9 dB/oct

2000 0.01 0.02

Overall 8.7 grms 12.3 grms

Duration 1 min/axis 2 min/axis

Frequencyrange

20 2000 Hz

Sweep rate 2 oct/min

Target Amplitude

0.25 g0-pk

Modal survey

Random vibration

Sinusoidal vibration

TKR Acceptance (g)

Qualification (g)

Lateral (X) 3.7 4.6

Lateral (Y) 3.7 4.6

Axial (Z) +6.8/-1.8 +8.5/-2.25

Sine burst

• 2 half level• 1 full level• 2 half level

5 sinusoidal cycles @ 25 Hz:



Tower thermal-vacuum cycles

Qualification Acceptance

Ranges -30°C 50°C -20°C 45°C

# of cycles 12 4

Temp. rate 20°C/hr 20°C/hr

Pressure 10-5 Torr 10-5 Torr

Duration @ plateau 12 hr 4 hr

Total Duration 384 hr + stabilization

58 hr + stabilization



Bottom tray

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