Gamma-Ray detection in Space Gamma-Ray detection in Space
Instrumentation in Astroparticle Physics
Maja Llena Garde
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Outline Outline
● Gamma-Rays and Gamma-Ray sources
● Overview of experiments
– INTEGRAL, CGRO, AGILE, Fermi
● Fermi in more detail
● Some Fermi results
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Gamma-Rays Gamma-Rays
● High energy photons
● Energies above 100keV
(Frequencies above 10^19 Hz)
● Overlap soft
gamma-rays, hard
X-rays
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Gamma-Ray Sources Gamma-Ray Sources
● AGN & Blazars
● Pulsars
● Gamma-Ray bursts
● Diffuse Emission
● Dark Matter annihilation
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Gamma-Ray Sources Gamma-Ray Sources
● AGN & Blazars
● Pulsars
● Gamma-Ray bursts
● Diffuse Emission
● Dark Matter annihilation
Thermal processes
Inverse Compton scattering Accelerated charged particles De-excitation of atomic nuclei
Synchrotron and cyklotron radiation
Bremsstrahlung
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Gamma-Ray Sources Gamma-Ray Sources
● AGN & Blazars
● Pulsars
● Gamma-Ray bursts
● Diffuse Emission
● Dark Matter annihilation
Thermal processes
Inverse Compton scattering Accelerated charged particles De-excitation of atomic nuclei
Synchrotron and cyklotron radiation
Bremsstrahlung
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Gamma-Ray detection Gamma-Ray detection
● Gamma-rays can be detected through inonization processes
● Photoelectric effect
● Compton scattering
● Pair production
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Outline Outline
● Gamma-Rays and Gamma-Ray sources
● Overview of experiments
– INTEGRAL, CGRO, AGILE, Fermi
● Fermi in more detail
● Some Fermi results
10-11-14 Gamma-Ray detection in Space 9/29
CGRO (1991-2000) CGRO (1991-2000)
Compton Gamma-Ray Observatory Compton Gamma-Ray Observatory
●
4 Payloads:
●
The Burst and Transient Source Experiment (BATSE)
●
The Oriented Scintillation Spectrometer Experiment (OSSE)
●
The Compton Telescope (Comptel)
●
Energetic Gamma Ray Experiment Telescope (EGRET)
●
EGRET performed the very first all-sky survey above 50MeV!
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INTEGRAL (2000-) INTEGRAL (2000-)
INTErnational Gamma-Ray Astrophysics Laboratory INTErnational Gamma-Ray Astrophysics Laboratory
● Two gamma-ray instruments
●
SPI (SPectrometer on INTEGRAL)
●
IBIS (Imager on Board the INTEGRAL Satellite)
● Coded Mask Imaging
●
see Christoffers talk
Coded Mask
Veto
Germanium Detector Array
SPI
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AGILE AGILE
Astro-rivelatore Gamma a Immagini LEggero Astro-rivelatore Gamma a Immagini LEggero
● All Italian mission
● Tungsten absorber
● Silicon strip detector
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Fermi Gamma-Ray Space Telescope Fermi Gamma-Ray Space Telescope
● Launched on June 11, 2008
● Instruments:
●
LAT – Large Area Telescope
●
GBM - Glast Burst Monitor
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Outline Outline
● Gamma-Rays and Gamma-Ray sources
● Overview of experiments
– INTEGRAL, CGRO, AGILE, Fermi
● Fermi in more detail
● Some Fermi results
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Instruments onboard Instruments onboard
Fermi
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Glast Burst Monitor Glast Burst Monitor
● Two sets of detectors:
●
12 sodium iodide (NaI) scintillators (Low-energy detector)
●
2 cylindrical bismuth germanate scintillators (High-energy detector)
● Large FoV
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Fermi-LAT Fermi-LAT
● Pair-conversion telescope
● 16 modules containing
● Precision converter-tracker
● Calorimeter
● Anticoincidence detector
● Specs:
● FoV: 2.4 sr at 1GeV
● Energy range 30MeV - >300GeV
● 1,8m x 1,8m x 0,72m
1,8 m
0,72 m
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Precision converter-tracker Precision converter-tracker
● 18 tungsten
converter layers
● 16 dual silicon
tracker planes
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Recap. Semiconductor detector Recap. Semiconductor detector
● A particle passing through ionizates the semiconductor material, creating an
electron and a hole.
● Intrinsic, not doped
● N-doped, negative, extra electrons
● P-doped, positive, abundance of holes
● PN-junction
● PIN diod
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Why Tungsten - Silicon?
Why Tungsten - Silicon?
● Tungsten is a high-Z material converting γs to e+e- pairs
● Silicon is a semiconductor detector (n-doped here)
● Dual silicon traker planes:
strips with different
orientation (Silicon Strip Detector)
● Silicon strip detectors have a self triggering capability
● Structure material
photon
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Calorimeter Calorimeter
● 96 long narrow CsI scintillators stacked in 8 layers
● Scintillation blocks read out by PIN photodiods.
● The scintillators are alternating in orientation so the location and spread of the shower can be determined.
● The direction of the incoming
particle so it could work as a
tracker.
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Anticoincidence detektor Anticoincidence detektor
● Plastic scintillator
● Made of 89 individual sections to distinguish charged particles from the direction of the
incomming gamma and ignore others.
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DAQ and trigger DAQ and trigger
● DAQ = Data AcQuisition system
● Trigger (only if 3 xy-planes in a row are triggerd)
● Combines information from all the components to decide when a likely gamma-ray has been detected and to choose what information to send to the ground.
● Minimum instrumental dead-time / event readout is
26.5µs
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Background rejection Background rejection
● Anticoincidence detector
● Data cuts
● Earth albedo
● Rocking angle
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Quick comparasion Quick comparasion
Quantity LAT (Minimim Spec.)
EGRET
Energy Range 20 MeV - 300 GeV 20 MeV - 30 GeV
Peak Effective Area > 8000 cm 2 1500 cm 2
Field of View > 2 sr 0.5 sr
Angular Resolution < 3.5° (100 MeV)
< 0.15° (>10 GeV)
5.8° (100 MeV)
Energy Resolution < 10% 10%
Deadtime per Event < 100 µs 100 ms
Source Location
Determination < 0.5' 15'
Point Source Sensitivity < 6 x 10 -9 cm -2 s -1 ~ 10 -7 cm -2 s -1
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Outline Outline
● Gamma-Rays and Gamma-Ray sources
● Overview of experiments
– INTEGRAL, CGRO, AGILE, Fermi
● Fermi in more detail
● Some Fermi results
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Dark Matter Indirect detection with Dark Matter Indirect detection with
Fermi-LAT Fermi-LAT
● Very weak signal dominated by foreground.
● Galactic Center, Galactic Halo, Satellites, Spectral Lines, Galaxy clusters, Extragalactic diffuse emission...
● No detection yet.
2010, ApJ, 712, 147
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Fermi Bubbles – AGN activity? Bipolar Fermi Bubbles – AGN activity? Bipolar
galactic wind?
galactic wind?
arxiv:1005.5480, accepted for ApJ
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References References
● ”The Large Area Telescope in the Fermi Gamma-Ray Space Telescope Mission”, Astrophys.J. 697:1071-1102, 2009
(arXiv:0902.1089v1)
● http://www-glast.stanford.edu/
● http://fermi.gsfc.nasa.gov/
● http://agile.rm.iasf.cnr.it/
● http://heasarc.gsfc.nasa.gov/docs/cgro/index.html
● http://www.esa.int/esaMI/Integral/index.html
● Most pictures are from NASA or ESA
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Back-up slides
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INTEGRAL (2000-) INTEGRAL (2000-)
INTErnational Gamma-Ray Astrophysics Laboratory INTErnational Gamma-Ray Astrophysics Laboratory
● Two gamma-ray instruments
●
SPI (SPectrometer on INTEGRAL)
●
IBIS (Imager on Board the INTEGRAL Satellite)
● Coded Mask Imaging - Images
photon energies between E1 and E2
●
Coded mask - areas transparent or opaque to photons with energies between E1 and E2
●
Detector array – matched to the mask-pattern grid size
●
