GLAST LAT Overview and Status

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1 GLAST LAT Overview and Status INPAC Meeting, Berkeley May 5, 2007 Robert Johnson LAT Tracker Subsystem Manager Physics Department and Santa Cruz Institute for Particle Physics University of California at Santa Cruz 1

2 GLAST Observatory Gamma Ray Burst Monitor (GBM) 20 kev to 20 MeV Large Area Telescope (LAT) ~20 MeV and higher Spacecraft: General Dynamics Launch Vehicle Delta II H 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,

3 GLAST 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? 3

4 Point-Source Flux Sensitivity GLAST 1-year survey 5" threshold Isolated source!100 As much as 100 times improvement on EGRET Very well matched to the new groundbased detectors, in units of Crabs. (credit: A. Morselli et al.) 4

5 GLAST LAT Collaboration United 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 Michelson (Stanford & SLAC) LAT instrument fabrication and science support managed at SLAC. GLAST mission managed by NASA GSFC. 5

6 UCSC LAT Participation Experimental Faculty: Bill Atwood: original LAT conceptual design; simulation and reconstruction; background reduction; co-lead of calibration and and 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 LAT affiliated 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 relativistic flows Stefano Profumo: starting July1; dark matter search 6

7 Components of the LAT Precision Si-strip Tracker (TKR) 18 XY tracking planes with tungsten foil converters. Single-sided silicon strip detectors (228 "m pitch, ~900k strips). Identifies the photons and measures their direction. Hodoscopic CsI Calorimeter (CAL) Array of 1536 CsI(Tl) crystals in 8 layers. Measures the photon energy and images the shower. Segmented Anticoincidence Detector (ACD) 89 plastic scintillator tiles. Rejects background of charged cosmic rays; segmentation mitigates self-veto effects at high energy. Electronics System Includes a flexible, robust hardware trigger and software filters. ACD [surrounds 4x4 array of TKR towers]! e + e Tracker Calorimeter The systems work together to identify and measure the flux of cosmic gamma rays with energy from ~20 MeV to ~300 GeV. 7

8 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 ~10 6 channels 82 m 2 Si surface 8

9 GLAST Tracker Performance 1 example readout module Hit efficiency from cosmic-ray muons Threshold variation <9% rms in all modules (5.2% on average) Strip #, 1 to 1536 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-overthreshold (OR of all channels per layer) 9

10 Fully Assembled Tracker 10

11 LAT Calorimeter Team effort involving physicists and engineers from the United States (NRL), France (IN2P3 & CEA), and Sweden 1,728 CsI crystal detector elements 18 modules 11

12 Anti-Coincidence Detector (NASA GSFC) Scintillator Tiles Scintillator & Wave-Shifting Fibers Fibers Composite Shell Photomultiplier Tubes & Electronics Tile detector assembly (FNAL) Fermilab 2 PMTs Readout Electronics GSFC & SLAC LAT Mechanical Structure (SLAC) 12

13 LAT Anti-Coincidence Detector Team effort involving physicists and engineers from Goddard Space Flight Center, SLAC, and Fermi Lab ACD before installation of Micrometeoroid Shield NASA-GSFC ACD with Micrometeoroid Shield and Multi-Layer Insulation (but without Germanium Kapton outer layer) 13

14 Data Acquisition and Electronics (SLAC) 14

15 Cross-LAT Plate (SLAC) 15

16 The LAT at NRL, Following Environmental Testing 16

17 GLAST 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. 17

18 Some Cosmic Ray Events in the Full LAT 16 tower LAT rate: ~ 500 Hz 18

19 First integrated tower: A gamma-ray pair conversion 19

20 Components of Simulation & Analysis gamma-ray sky model background fluxes Particle Generation and Tracking Instrument Response (Digitization), Formatting Trigger and Onboard Filter (wrapped FSW) Detector Calibration Event Reconstruction Event Classification Performance High-level Science Analysis 20

21 GLAST LAT Simulation 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 High energy! interacts in LAT Blue: Recon Tracks Black: Charged Particles White: Photons 21

22 LAT MC Derived Performance 22

23 Residual Background (Proton + Blanket) $ 0 2! Large Angle $ 0 & Small Angle $ 0 (Hi energy tail) (e + + Blanket) 2! Annihilation Also we have e + & e - Bremstrahlung in the Blanket These Events are Irreducible a! is produced outside the ACD within the FoV 23

24 Residual Background Spacecraft Interaction with Stopping Stub(s) Proton + Spacecraft Cal Shower Stubs in Tracker Electromagnetic showers from below Irreducible: 63% Reducible: 37% Albedo! Cal Shower Stubs in Tracker These Events are Reducible (could in principle be eliminated) 24

25 The CERN Beam Test Campaign weeks at PS/T9 area (26/7-23/8) GeV 1,5 GeV 1 GeV (through MMS) 6,10 GeV (w/ & w/o MMS) 11 days at SPS/H4 area (4/9-15/9) 10,20,50,100,200,280 GeV 20,100 GeV 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 25

26 Beam Test Event 470 MeV gamma-ray conversion 26

27 Comparisons with MC Simulation PSF 280 GeV electrons at 30 deg PRELIMINARY ACD Backsplash 27

28 Mock Data Challenges DC2 sky Data challenges provide excellent test-beds for science analysis software. Full observation, instrument, and data processing simulation. Team uses data and tools to find the science. MC Truth revealed at the end. 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. 28

29 LAT 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 29

30 Instrument 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 30

31 Status & 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 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 31

32 The Evolving Picture of the Gamma-Ray Universe EGRET (>100 MeV) Simulated LAT (>100 MeV, 1 yr) Simulated LAT (>1 GeV, 1 yr) OSO-III (>50 MeV) 32

33 Conclusion GLAST launch is currently scheduled for December 14, Guest Investigator Program Proposals due September 9 ls/gi_program_background.html Getting involved with GLAST workshop at UCLA, May / See René Ong SWIFT instrument launches on the same type rocket planned for GLAST 33