GLAST Large Area Telescope:

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1 Gamma-ray Large Area Space Telescope GLAST Large Area Telescope: LAT Project and the calorimeter Per Carlson KTH Stockholm for the GLAST Collaboration SCINT2001, Chamonix September 2001

2 GLAST Gamma-Ray Large Area Space Telescope GLAST

3 International Collaboration ~ 100 collaborators from 28 institutions Organizations with LAT Hardware Involvement TKR CAL ACD CAL TKR TKR CAL Stanford University & Stanford Linear Linear Accelerator Center Center NASA NASA Goddard Space Space Flight Flight Center Center Naval Naval Research Laboratory University of of California at at Santa Santa Cruz Cruz University of of Washington Commissariat a l Energie Atomique, Departement d Astrophysique (CEA) (CEA) Institut InstitutNational de de Physique Nuclearie et et de de Physique des des Particules (IN2P3): Ecole EcolePolytechnique, College de de France, CENBG (Bordeaux) Hiroshima University Institute of of Space Space and and Astronautical Science, Tokyo Tokyo RIKEN RIKEN Tokyo Tokyo Institute of of Technology Instituto Nazionale di difisica FisicaNucleare (INFN): (INFN): Pisa, Pisa, Trieste, Bari, Bari, Udine, Udine, Perugia, Roma Roma Royal CAL Royal Institute of of Technology (KTH), (KTH), Stockholm

4 Structure and Evolution of Universe Quests Extremes of Energy & Matter Beyond the Big Bang The Lives of Stars Black Holes

5 Gamma rays carry a wealth of information: γ -rays do not interact much at their source: they offer a direct view into Nature s largest accelerators. similarly, the Universe is mainly transparent to γ rays: can probe cosmological volumes conversely, γ -rays readily interact in detectors, with a clear signature γ rays are neutral: no complications due to magnetic fields. Point directly back to sources

6 Energy versus time for X and Gamma ray detectors Energy 1 TeV 100 GeV WHIPPLE CAT HEGRA CANGAROO GRANITE MILAGRO ARGO HESS CELESTE, STACEE, Solar Two MAGIC Super Cangaroo VERITAS GLAST 10 GeV 1 GeV EGRET AGILE 100 MeV 10 MeV COMPTEL HESSI 1 MeV INTEGRAL 100 KeV 10 KeV BATSE OSSE SIGMA RXTE ASCA BeppoSAX HETE 2 Super AGILE Constellation-X 1 KeV ROSAT Chandra XMM Swift XEUS Aldo Morselli 01/01 Year Aldo Morselli 6/9/99

7 GLAST Science Topics Active Galactic Nuclei Isotropic Diffuse Background Radiation Cosmic Ray Production: Identify sites and mechanisms Endpoints of Stellar Evolution Neutron Stars/Pulsars Black Holes Unidentified Gamma-ray Sources Dark Matter Solar Physics Gamma-Ray Bursts DISCOVERY!

8 Scientific Heritage: CGRO- EGRET (E > 100 MeV) Cygnus Region 3C279 Vela Geming a Cosmic Ray Interactio ns With ISM PSR B LM PKS C 512 Cra PKS b

9 3 rd EGRET Source Catalog 271 sources 172 sources are unidentified

10 Diffuse Extra-galactic Background Radiation Is it really isotropic (e.g., produced at an early epoch in intergalactic space) or an integrated flux from a large number of yet unresolved sources? GLAST has higher sensitivity to weak sources, with better angular resolution. GLAST will bring alive the gamma-ray sky! The origin of the diffuse extragalactic gamma-ray flux is a mystery. Either sources are there for GLAST to resolve (and study!), OR there is a truly diffuse flux from the very early universe.

11 Active Galactic Nuclei (AGN) Active galaxies produce vast amounts of energy from a very compact central volume. Prevailing idea: powered by accretion onto super-massive black holes ( solar masses). Different phenomenology primarily due to the orientation with respect to us. HST Image of M87 (1994) Models include energetic (multi-tev), highly-collimated, relativistic particle jets. High energy γ-rays emitted within a few degrees of jet axis. Mechanisms are speculative; γ-rays offer a direct probe.

12 From Jungman et al, Phys. Rep. 267(1996)195. Dark matter Rotational curve Dar matter halo The dark matter halo is is necessary in in order to to explain the the rotational curve!

13 Dark matter X-rays from a hot gas in a galaxy cluster An An X-ray image (purple) that that shows hot hot gas gas superimposed on on a visible light light image. The The gas gas is is so so hot hot so so that that the the visible mass mass in in the the galaxy cluster is is not not sufficient to to keep keep it. it. Dark matter!

14 Candidates for Galactic Dark Matter Massive Compact Halo Objects (MACHOs) Low (sub- solar) mass stars. Standard baryonic composition. Use gravity microlensing to study. Could possibly account for 25% to 50% of Galactic Dark Matter. Neutrinos Small contribution if atmospheric neutrino results are correct, since m ν < 1eV. Large scale galactic structure hard to reconcile with neutrino dominated dark mat Weakly Interacting Massive Particles ( WIMPs) Non- Standard Model particles, ie: supersymmetric neutralinos Heavy (> 10GeV) neutrinos from extended gauge theories.

15 WIMP Dark Matter Annihilations? Extensions to the Standard Model of Particle Physics also provide good candidates for galactic halo dark matter. This would be a totally new form of matter. If true, there may well be observable halo annihilations into monoenergetic gamma rays. X X q q or γγ or Zγ lines? Energy (GeV) Just an example of what might be waiting for us to find! Number of counts Simulated response to 50 GeV side-entering γ s

16 Total photon spectrum from the galactic center from χχ ann. Two-year scanning mode (6 S ) Infinite energy resolution γ lines 50 GeV 300 GeV With finite energy resolution Bergstrom et al.

17 Diffuse gamma ray flux from cosmological χχ ann. In this case broader line due to redshift. EGRET extragalactic diffuse data m χ = 86 GeV m χ =166 GeV Bergstrom et. al. astro-ph/

18 Best EGRET GRB GRB

19 GRB Missions CGRO Beppo SAX HETE - II Swift AGILE GLAST EXIST

20 EGRET(Spark Chamber) VS. GLAST(Silicon Strip Detector) EGRET on Compton GRO ( ) GLAST Large Area Telescope ( )

21 Instrument Large Area Telescope (LAT) 16 towers modularity height/width = 0.4 large field-of-view Tracker Si-strip detectors: total of ~10 6 ch. Design Overview γ Calorimeter hodoscopic CsI crystal array cosmic-ray rejection shower leakage correction shower max contained < 100 GeV Anticoincidence Detector Shield segmented plastic scintillator minimize self-veto e + e Flight Hardware & Spares 16 Tracker Flight Modules + 2 spares 16 Calorimeter Modules + 2 spares 1 Flight Anticoincidence Detector Data Acquisition Electronics + Flight Software 3000 kg, 650 W (allocation) 1.75 m 1.75 m 1.0 m 20 MeV 300 GeV

22 Calorimeter structure and design Side panel AFEE PEM Closeout plate

23 CAL structure and design Corner aluminum Carbon Fiber cells in compact geometry Bottom plate : alveolar structure aluminum attached to the Grid. Insert to attach Closeout Plate, AFEE, Side Panel

24 Crystal Detector Element (Wrapped) Mylar tape Composite cell Dual PIN diode 3M film strip Kapton cable Elastomer cord

25 CsI(Tl) ingot at AMCRYS

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28 Light yield as function of position Left PMT, right PMT and average.

29 Light yield measurements June 2001

30 Performance Plots (after all background rejection cuts, being updated) FOV w/ energy measurement due to favorable aspect ratio Effects of longitudinal shower profiling Derived performance parameter: high-latitude point source sensitivity (E>100 MeV), 2 year all-sky survey: 1.6x10-9 cm -2 s -1, a factor > 50 better than EGRET s

31 LAT Capabilities Low deadtime <100 μs/event - LAT 110 ms/event - EGRET Large area >8000 cm 2 -LAT 1500 cm 2 -EGRET Large FOV for detecting rare events >2 sr - LAT 0.5 sr - EGRET

32 Expected LAT Performance GRBs detected per year Localization of 1-10 arcmin Afterglows ~25 afterglows/year > 30 MeV ~ 4 afterglows/year > 100 MeV 75% of afterglows will persist for 2000 sec

33 Integral flux (photons cm -2 s -1 ) Sensitivity of γ-ray detectors GLAST MAGIC Aldo Morselli 01/01 EGRET ARGO Whipple VERITAS Crab Nebula Large field of View experiments Cerenkov detectors in operation Past experiments Future experiments 5 sigma, 50 hours, > 10 events AGILE HEGRA CELESTE, STACEE MILAGRO HESS Photon Energy (GeV) All sensitivities are at 5σ. Cerenkov telescopes sensitivities (Veritas, MAGIC, Whipple, Hess, Celeste, Stacee, Hegra) are for 50 hours of observations. Large field of view detectors sensitivities (AGILE, GLAST, Milagro,ARGO are for 1 year of observation. MAGIC sensitivity based on the availability of high efficiency PMT s

34 Sky coverage of all sky and Cerenkov telescopes in 2002 HEGRA Magic CAT Milagro Whipple AGILE Cerenkov telescope all sky monitors

35 Conclusions GLAST will be an important step in gamma ray astronomy ( ~ sources compared to ~ 200 of EGRET) A partnership between High Energy Physics and γ ray Astrophysics Beam test and software development well on the way Wide range of possible answers/discoveries, including possible dark matter detection Gold era for multiwavelenght studies Be prepared, 2006 is near!

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