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1
Gamma ray Large Area Space Telescope - GLAST
Eγ = 20 MeV - 300 GeV
Explore most powerful sources of acceleration in the universe
GLAST Ambassadors
July 18, 2002
Gary Godfrey - SLAC
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Gamma Rays• Energy = h * frequency (h=4.1 x 10-15 eV-sec)
Radio 10-9 - 10-8 eVTV 10-7 eVInfrared .1 - 1 eVVisable 2 - 5 eVXrays 103 - 105 eVGamma Rays >106 eV
Gamma Rays can’t be reflected by mirrorsWavelength << interatomic distances
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Why do we need a satellite ?
2005 GLAST
2001 GLASTBalloon Flight
~103
g cm
-2
~30
km
Atmosphere:γ
For Eγ < ~ O(100) GeV, must detect above atmosphere (balloons, satellites, rockets)
For Eγ > ~ O(100) GeV, information from showers penetrates to the ground (Cerenkov)
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How are gamma rays generated ?
Accelerated particles interact with matter, magnetic field or photon fields
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16 towers arranged in a 4 x 4 configuration
GLASTGLAST
1 out of 16 towers
LAT
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GLAST Collaboration
a University of California, Santa Cruz, Department of Physics, Santa Cruz, California .b University of Chicago, Department of Physics, Chicago, Illinoisc Commissariat a l’energie atomique (CEA), Saclay, Francee Ecole Polytechnique, Laboratoire de Physique Nucleaire des Hautes Energies
(LPNHE), Palaiseau, France f Hiroshima University, Department of Physics, Hiroshima, Japang The Institute of Physical and Chemical Research, Saitama, Japanh The Institute of Space and Astronautical Science, Sagamihara, Japan i Kanagawa University, Institute of Physics, Kanagawa, Japan j Lockheed-Martin Solar and Astrophysics Laboratory, Lockheed-Martin Advanced
Technology Center, Palo Alto, California k University of Massachusetts at Amherst, Amherst, Massl Max-Planck-Institut für extraterrestrische Physik (MPE), Garching, Germany m NASA Ames Research Center, Mountain View, Californian The NASA/Goddard Space Flight Center, Greenbelt, Marylando The Naval Research Laboratory, Washington, D.C.
p University of Rome, Department of Physics and Instituto Nazionale di Fisica Nucleare, Tor Vergata, Rome, Italy
q Royal Institute of Technology, Stockholm, Swedenr Shibaura Institute of Technology, Department of Electronic Information Systems, Faculty of
Systems Engineering, Shibaura, Japan s Sonoma State University, Department of Physics and Astronomy, Rohnert Park, Californiat Stanford University, Department of Physics; Hansen Experimental Physics Laboratory; Stanford
Linear Accelerator Center, Stanford, Californiau Stockholm University, Stockholm, Sweden v University of Tokyo, Department of Physics, Institute for Cosmic Ray Research, Tokyo, Japan w University of Trieste, Department of Physics, Instituto Nazionale di Fisica Nucleare and Scuola
Internazionale Superiore di Studi Avanzati, Trieste, Italyx University of Turin, Department of Physics, Osservatorio Astronomico, Turin, Italyy University of Washington, Department of Physics, Seattle, Washin gton z University of Wisconsin, Department of Physics, Madison, Wisconsinα Instituto di Fisica Cosmica e Tecnologie Relative, CNR, Milano, Italyβ Boston University, Boston, Massachusettsγ University of Udine, INFN, Italy
>100 Collaborators
>30 Institutions
R. Arnold k
W. Atwood G Barbiellini w
L. Bergstromu
D. Bertsch n
V. Bidoli p
E. Bloomt
J. Bonnelln
P. Bosted kU. Bravar w
T. Burnett y
P. Caraveo αP. Carlson q
A. Celotti w
D. Chenette j
L. Cominsky s
C. Covault b
J. Danzigew
A. de Angelis γ
A. Djannati-Atai e
S. Digel n
B. Dingus z
E. do Couto e Silvat
D. Dorfan a
R. Dubois t
A. Ferrari x
P. Fleury e
T. Francke q
Y. Fukazawa v
N. Gehrelsn
B. Giebels t
M. Gliozzi xG. Godfrey t
I. Grenier c
J. Grove o
H. Gursky o
R. Hartman n
T. Handa t
J. Hernando aM. Hirayama b
S. Hunter n
R. Johnson a
W. Johnson o
T. Kamae t,v
K. Kasahara r
N. Kawai g
T. Kifune v
W. Kroeger a
H. Kubo g
P. Nolan t
J. Norris n
A. Odiant
T. Ohsugi f
R. Ong b
M. Oreglia b
J. Ormes n
J. Paul c
A. Perrino pB. Phlips o
P. Picozza p
P. Ray o
E. Reali p
S. Ritz,n
S. Rock kJ.J. Russell t
H. Sadrozinski a
J. Scargle m
P. Schiavon w
S. Severoni p
G. Share o
J. Skibo o
D. Suson o
Z. Szalata k
T. Takahashi h
T. Tamura i
M. Tavani α
D. Thompson n
S. Torii i
A. Vacchi w
M. Villata x
K. Wood o
A. Yoshida g
K. Yoshida i
P. Kunz t
Y. Lin t
M. Lovellette o
G. Madejski t
J. Mattox βH. Mayer-
Hasselwander l
P. Michelson t
A. Moiseev n
M. Mori v
A. Morselli p
G. Nakano jG. Navarra x
HEAHEP
+ new French and Italian collaborators
Incomplete list
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Si -Pb Tracker
CsI Calorimeter
Large Area Telescope2560 kg, 600 W, 1.73² × 1.06 m
Anti-Coincidence Detector
Delta II
7920 H
Gamma-ray Burst Monitor
International Collaboration
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γ
e+ e- calorimeter (energy measurement)
particle tracking detectors
conversion foils
whenever 3 planes in a row are hit, then read out the event and store its information
Gamma Converts in Tungsten Foil
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• A charge particle interacts with the ACD scintillator and produces light.
• A γ usually goes through the ACD without making any signal.
γ
e+ e- calorimeter (energy measurement)
particle tracking detectors
conversion foils
charged particle anticoincidence shield
ACD (plastic scintillator) for background rejection
ACD Rejects Charged Cosmic Rays
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Strip-shapedPN diode
200 micron wide
400 micron thick high purity silicon
VLSI amplifier
γ
e+e-
Silicon Strip Detector
9 cm
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XGT
ACD
TKRCAL
Pressure Vessel
Support Structure
Balloon Flight Engineering Module
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Charged particle photon
Since there are at least 3 hits in a row, the event is triggered
Problem: In the GLAST orbit there are ~105
times more cosmic rays than photons !
Real data from particle beams produced at SLAC
Beam Test Engineering Module
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• Active Galactic Nuclei (AGN)• Gamma Ray Bursts (GRB)• Diffuse Galactic γ-ray background• Dark Matter (or its absence “MOND”) • Diffuse Extragalactic γ-ray background (relics from the Big Bang)• Pulsars• Cosmic rays•Solar flares
Physics Motivation for GLAST
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Up to 104 times the luminosity of typical galaxy in a volume of one cubic parsec ! (1 pc = 3.1 x 1018 cm ~ 3 light years) (assuming isotropic emission)
Changes in Luminosity in a fraction of a day !
Radiation is emitted at all frequencies !
Active Galactic Nuclei
EGRET
GLAST Energy and timeresolved spectra
Possibility to study flares
Study mechanisms of acceleration and cooling
EGRET
GLAST
γ rays
X rays
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We already know that they occur at cosmological distances, implying energies up to 1054 ergs during burst emission (if we assume isotropic model)
Gamma Ray Bursts
long
short
Time of duration of a burst
16S. G. Djorgovski and S. R. Kulkarni / W. M. Keck Observatory
2 days after burst 2 months after burst
GRB 971214 –12 billion light years away (z =3.42) !(about 5.9 trillion miles for light to travel)
Optical Afterglow
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271 sources169 unidentified
EGRET Sky map
Pointsources
EGRET Gamma Ray Emissions > 100 MeV
Cosmic background…What is the point source contribution ?
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WIMP annihilations could produce such structure.
10-5 ph cm-2 sec-1 sr-1 for Eg > 1 GeV
Search for Dark Matter
Contours of photon intensity after subtraction of “best estimate” of Galactic diffuse model. Data suggests presence of a galactic halo (Dixon et al. 1998).
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Halo WIMP annihilations
Although calculation for γ-rays is less uncertain than for other signals (multi-GeV antiprotons, positrons) a null result will not likely constrain SUSY parameter space.
If SUSY uncovered at accelerators, GLAST may be able to determine its cosmological significance quickly.
If true, there may well beobservable halo annihilations
q
qγγ or Zγ
lines
X
X
Example: X is χ0 from Standard SUSY, annihilations to jets, producingan extra component of multi-GeV γ flux that follows halo density (not isotropic) peaking at ~ 0.1 M χ0
or lines at M χ0. Background is galactic γ ray diffuse.
~
Good particle physics candidate for galactic halo dark matter is the LSP in R-parity conserving SUSY
~~
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Indications for Dark Matter
1) Rotation curves of spiral galaxies go to a constant tangential velocity v at large radii.
v2/r = GMgalaxy/r2 when all galaxy mass is within the radius r. So v should decrease with r, but it doesn’t !! Hence maybe there is invisable Dark Matter.
2) Particle Physicists like looking for Dark Matter. Maybe Dark Matter is SUSY Wimps (neutralinos), or Axions. Theoretically predicted particles that would have been made in the Big Bang.
21
MOND“Modified Orbital Newtonian Dynamics” (Sci Am August, 2002)
But is it Dark Matter or Modified Newton ? http://www.astro.umd.edu/~ssm/mond/
Change Newtonian acceleration when the acceleration is very small:
Acceleration = GM/r2 -> sqrt( GM/r2 * a0) when Acceleration < a0
v2/r = sqrt( GMgalaxy/r2 * a0 v4 = GMgalaxy * a0
1) Galaxys’ tangential velocity is now a constant at large radii.
2) If we assume Mgalaxy/Lummeasured ~ 2, then a0~ 2 x 10-8 cm/sec2 seems to be the same number for all spiral galaxies looked at !
3) An experimental regularity called “Tully Fisher” V4 α Lum is explained.
4) The Hubble Constant = 7 x 10-8 cm/sec2 (is ~a0 just a coincidence?)
GLAST will set limits (or see the it!) on how much of certain forms of Dark Matter can be trapped in our Galaxy. If no Dark Matter, maybe MOND ?
22
http://octopus.gma.org/surfing/satellites/about.html
Low Earth Orbit (LEO) 200-500 miles (320–800 km)
Which orbit ?
Geostationary Orbit (GEO)
~22000 miles (~35000 km)
(must travel fast)
(higher background)
Communicationsatellite
GLAST
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flux is 20-30 times higher (low energy)
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•1997 Test Beam validation of measurement principles and technology choices. W.B. Atwood et al SLAC-PUB-8166 (1999), NIM A 446, (2000), 444.
•1999/2000 Test Beamfull engineering model including compact front end electronicsE. do Couto e Silva et al SLAC-PUB-8682 (2000), accepted for publication in NIM A
•2001 Balloon FlightNext step in full flight software development and improvements based upon 1999/2000 test beam experience
•2003/2004 Calibration Beam testsFull calibration of instrument and response matrices
•2006 March, Launch
GLAST timeline
25
271 sources including 169 unidentified sources 5 Gamma Ray Bursts6 pulsars
~70 AGN
EGRET (1991) 20 MeV - 30 GeV
Spark Chamber
~25 sources 1 extragalactic source (3C273)
COS-B (1975) 50 MeV – 5 GeV
Spark Chamber
Galactic diffuse emission~10 Galactic sources
SAS-2 (1972) 30 MeV - 0.2 GeV
Spark Chamber
Hint of Galactic diffuse emission
OSO-III (1967) 50 MeV - 0.5 GeV
Proportional Counter
Gamma Ray Astronomy in Space
26
EGRET
GLAST
27
EGRET
20 MeV - 30 GeV
1500 cm²
0.5 sr
~ 10-7 γ cm-2 s-1
15 ’
100 ms
LAT (min) Improvement
20 MeV - 300 GeV
> 8000 cm² > 6
> 2.0 sr > 4
< 6 10-9 γ cm-2 s-1 > 20
< 0.5 ’ > 30
< 100 µs > 100
Energy
Surface
Field of view
Sensitivity (1yr)
Localization
Deadtime
From EGRET to LAT…
•Large area•Low instrumental background
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GLAST Performance
30
EGRET 95%l¡
5σ LAT source r = 7 ’5σ LAT source r = 7 ’
0.5°
Rosat or Einstein X-ray source
! 1.4 GHz VLA radiosource
LAT 95%3EG1911-2000r = 0.3 ’
Identification of Sources
31
LAT Science capabilities - sensitivity
200 γ bursts per year prompt 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 day3EG limit
0.01
0.001LAT 1 yr2.3 10-9
cm-2s-1
large field-of-view
Scan mode during 1st year