1

GLAST LAT OverviewGLAST LAT Overview

and Statusand Status

INPAC Meeting, BerkeleyINPAC Meeting, BerkeleyMay 5, 2007May 5, 2007

Robert Johnson

LAT Tracker Subsystem Manager

Physics Department and

Santa Cruz Institute for Particle Physics

University of California at Santa Cruz

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GLAST ObservatoryGLAST Observatory

Launch Vehicle Delta II – 2920-10H

Launch Location Kennedy Space Center

Orbit Altitude 575 Km

Orbit Inclination 28.5 degrees

Orbit Period 95 Minutes

Orientation +X to the Sun

Launch Date December 14, 2007

Large Area Telescope (LAT)~20 MeV and higher

Gamma Ray Burst Monitor (GBM)20 keV to 20 MeV

Spacecraft: General Dynamics

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GLAST Science OpportunitiesGLAST Science Opportunities

• Active Galactic Nuclei

• Extra-galactic Background Light (EBL)

• Isotropic Diffuse Background Radiation

• Endpoints of Stellar Evolution

– Neutron Stars/Pulsars

– Black Holes

• Cosmic Ray Production:

– Identify sites and mechanisms

• Gamma-Ray Bursts

• Solar Physics

• DISCOVERY!

– Identifying known sources

– New classes of !-ray sources?

– Dark Matter (WIMPs)?

– New cosmological relics?

– Dispersion in vacuum?

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Point-Source Flux SensitivityPoint-Source Flux Sensitivity

(credit: A. Morselli et al.)

• GLAST 1-year

survey

• 5" threshold

• Isolated source

• As much as 100

times improvement

on EGRET

• Very well matched

to the new ground-

based detectors, in

units of “Crabs”.

!100

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GLAST LAT CollaborationGLAST LAT CollaborationUnited States• California State University at Sonoma• University of California at Santa Cruz - Santa Cruz Institute for Particle

Physics• Goddard Space Flight Center – Laboratory for High Energy Astrophysics• Naval Research Laboratory• Ohio State University• Stanford University (SLAC and HEPL/Physics)• University of Washington• Washington University, St. Louis

France

• IN2P3, CEA/Saclay

Italy

• INFN, ASI

Japan• Hiroshima University

• ISAS, RIKEN

Sweden• Royal Institute of Technology (KTH)

• Stockholm University

PI: Peter MichelsonPI: Peter Michelson (Stanford & SLAC)

• LAT instrument fabrication and science

support managed at SLAC.

• GLAST mission managed by NASA GSFC.

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UCSC LAT ParticipationUCSC LAT Participation

• Experimental Faculty:

– Bill Atwood: original LAT conceptual design; simulation andreconstruction; background reduction; co-lead of calibration andand analysis working group

– Robert Johnson: led tracker subsystem design and fabrication;co-lead of dark matter science working group

– Hartmut Sadrozinski: instrumentation, especially SSDs

– Terry Schalk: flight software management

– David Smith: affiliated scientist; solar observations

– Steve Thorsett: GLAST interdisciplinary scientist and LATaffiliated scientist; pulsars, coordination of radio observations

• Theory Faculty

– Joel Primack: affiliated scientist; probing IBL; dark matter

– Stan Woosley: affiliated scientist; GRB & supernovae

– Enrico Ramirez-Ruiz: affiliated scientist; GRB and relativisticflows

– Stefano Profumo: starting July1; dark matter search

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The systems work together to identify and measure the flux ofThe systems work together to identify and measure the flux of

cosmic gamma rays with energy from ~20 MeV tocosmic gamma rays with energy from ~20 MeV to ~ ~300 GeV.300 GeV.

Components of the LATComponents of the LAT

e+ e–

!

ACD[surrounds4x4 arrayof TKRtowers]

Calorimeter

Tracker•• Precision Si-strip Tracker (TKR)Precision Si-strip Tracker (TKR)

18 XY tracking planes with tungsten foilconverters. Single-sided silicon stripdetectors (228 "m pitch, ~900k strips).Identifies the photons and measurestheir direction.

•• Hodoscopic Hodoscopic CsICsI Calorimeter (CAL) Calorimeter (CAL)Array of 1536 CsI(Tl) crystals in 8layers. Measures the photon energyand images the shower.

•• Segmented Anticoincidence DetectorSegmented Anticoincidence Detector(ACD)(ACD) 89 plastic scintillator tiles.Rejects background of charged cosmicrays; segmentation mitigates self-vetoeffects at high energy.

•• Electronics SystemElectronics System Includes a flexible,robust hardware trigger and softwarefilters.

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LAT Silicon Tracker

Team effort involving physicists and engineers from the

United States (UCSC & SLAC), Italy (INFN & ASI), and Japan

18 “towers”

342 “trays”

10,368 sensors

648 MCMs

16,848 ASICs

~106 channels

82 m2 Si surface

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GLAST Tracker PerformanceGLAST Tracker Performance

• Hit efficiency (in active area) >99.4%

• Overall Tracker active area fraction: 89.4%

• Noise occupancy <5!10#7

• (with small number of noisy channels masked)

• Power consumption 158 W (178 µW/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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Fully Assembled TrackerFully Assembled Tracker

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LAT CalorimeterLAT CalorimeterTeam effort involving physicists and engineers from the

United States (NRL), France (IN2P3 & CEA), and Sweden

1,728 CsI crystal

detector elements

18 modules

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Anti-Coincidence Detector (NASA GSFC)Anti-Coincidence Detector (NASA GSFC)

Scintillator & Wave-Shifting Fibers

Readout Electronics

GSFC & SLAC

Scintillator

Tiles

FibersComposite

Shell

Photomultiplier

Tubes &

Electronics

LAT Mechanical Structure

(SLAC)

Fermilab

Tile detector

assembly

(FNAL)

2 PMTs

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LAT Anti-Coincidence DetectorLAT Anti-Coincidence Detector

Team effort involving physicists and engineers from

Goddard Space Flight Center, SLAC, and Fermi Lab

ACD before installation of

Micrometeoroid Shield

ACD with Micrometeoroid Shield and

Multi-Layer Insulation (but without

Germanium Kapton outer layer)

NASA-GSFC

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Data Acquisition and Electronics (SLAC)Data Acquisition and Electronics (SLAC)

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Cross-LAT Plate (SLAC)Cross-LAT Plate (SLAC)

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The LAT at NRL, Following EnvironmentalThe LAT at NRL, Following Environmental

TestingTesting

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GLAST During IntegrationGLAST During Integration

Both the LAT and GBM are now

integrated to the Spacecraft at

General Dynamics in Phoenix,

Arizona.

This photo shows the LAT and the

NaI GBM modules mounted onto

the spacecraft.

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16 tower LAT

rate: ~ 500 Hz

Some Cosmic Ray Events in the Full LAT

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First integrated tower: A gamma-ray pair conversionFirst integrated tower: A gamma-ray pair conversion

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Trigger and Onboard

Filter (wrapped FSW)

Components of Simulation & AnalysisComponents of Simulation & Analysis

Particle Generation and Tracking

Instrument Response

(Digitization), Formatting

background fluxes

Event Classification

Performance

High-level

Science

Analysis

Detector

Calibration

Event Reconstruction

gamma-ray sky model

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GLAST LAT SimulationGLAST LAT Simulation

High energy ! interacts in LAT

Blue: Recon Tracks

Black: Charged Particles

White: Photons

• Geometry Detail

• > 500k Volumes

• Geant 4 Interaction Physics

• QED: based on original EGS

code

• Hadronic: based Geisha (can

use FLUKA a well as others)

• Propagation

• Full treatment of multiple

scattering

• Surface-to-surface ray tracing

• Connection to detector Response

• Energy deposits in Active

Volumes

• Parametric Detector response

based on energy and location

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LAT MC Derived PerformanceLAT MC Derived Performance

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Residual BackgroundResidual Background

(Proton + Blanket) $0 2!

(e+ + Blanket) 2!

Annihilation

Also we have e+ & e-

Bremstrahlung in the

Blanket

Large Angle $0

& Small Angle $0 (Hi energy tail)

These Events are Irreducible

a ! is produced outside the ACD within the FoV

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Residual BackgroundResidual Background

Spacecraft Interaction

with

Stopping Stub(s)

Proton + Spacecraft

Cal Shower

Stubs in Tracker

Electromagnetic showers

from below

Albedo !

Cal Shower

Stubs in Tracker

These Events are Reducible (could in principle be eliminated)

Irreducible: 63% Reducible: 37%

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TheThe CERN CERN BeamBeam Test Test CampaignCampaign - 2006 - 2006

• 4 weeks at PS/T9 area (26/7-23/8)

– Gammas @ 0-2.5 GeV

– Electrons @ 1,5 GeV

– Positrons @ 1 GeV (through MMS)

– Protons @ 6,10 GeV (w/ & w/o MMS)

• 11 days at SPS/H4 area (4/9-15/9)

– Electrons @ 10,20,50,100,200,280 GeV

– Protons @ 20,100 GeV

– Pions @ 20 GeV

• Data, data, data…

– 1700 runs, 94M processed events

– 330 configurations (particle, energy,angle, impact position)

– Mass simulation

• A dedicated team

– 60 people worked at CERN

– Whole collaboration represented

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Beam Test EventBeam Test Event

470 MeV

gamma-ray

conversion

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ComparisonsComparisons withwith MC Simulation MC Simulation

PSF 280 GeV electrons at 30 deg

ACD

Backsplash

PREL

IMIN

ARY

PREL

IMIN

ARY

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Mock Data ChallengesMock Data Challenges

• A progression of data challenges.

– DC1 in 2004: 1 simulated week all-sky survey simulation.

• Find the sources, including GRBs

• A few physics surprises

– DC2 in 2006: 55 simulated days all-sky survey.

• First catalog

• Source variability (AGN flares, pulsars) added. Lightcurves and

spectral studies. correlations with other wavelengths. Add

GBM. Study detection algorithms. Benchmark data processing.

Data challenges provideexcellent test-beds forscience analysissoftware.

Full observation,instrument, and dataprocessing simulation.

Team uses data and toolsto find the science. “MCTruth” revealed at theend.

DC2 sky

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LAT Science Working GroupsLAT Science Working Groups

• Blazars and other AGN

• Calibration and Analysis Methods

• Catalogs

• Dark Matter and New Physics

• Diffuse and Molecular Clouds

• Gamma-Ray Bursts

• Pulsars, Supernova Remnants, and Plerions

• Sources in the Solar System

• Unidentified Sources, Population Studies, and other

Galaxies

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Instrument Team ProjectsInstrument Team Projects

• From the original LAT proposal, the LAT team is committed to

the following, especially in Year-1:

– All sky survey:

• Source catalog

• All-sky maps

• Residual maps (source subtracted)

• Diffuse model

– GRBs and transients:

• GRB catalog

• Transient alerts

– In-depth analyses of selected sources

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Status & MilestonesStatus & Milestones

• April 2: Observatory Comprehensive Performance

Tests (CPT) completed for sides A and B

• April 3: LAT radiator dry fit & electrical tests

• April 11: Observatory Pre-Environmental Review

(PER) completed successfully

• Observatory environmental tests begin soon…

• June 1: LAT Flight Software Release 1-0-0

• 6 observatory End-to-End tests between now and

launch

• Complete LAT electronic and muon calibration to be

performed this spring before observatory T/V testing

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The Evolving Picture of theThe Evolving Picture of the

Gamma-Ray UniverseGamma-Ray Universe

OSO-III (>50 MeV)

EGRET (>100 MeV)Simulated LAT (>100 MeV, 1 yr)Simulated LAT (>1 GeV, 1 yr)

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ConclusionConclusion

• GLAST launch is currently

scheduled for December 14, 2007.

• Guest Investigator Program

– Proposals due September 9

– http://glast.gsfc.nasa.gov/ssc/proposa

ls/GI_Program_Background.html

• Getting involved with GLAST

workshop at UCLA, May 22

– http://gamma1.astro.ucla.edu/glast_20

07/

– See René Ong

SWIFT instrument launches

on the same type rocket

planned for GLAST