Transcript PowerPoint

GLAST Burst Monitor
The calibration of the GLAST Burst Monitor
NaI- and BGO-detectors
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by Andreas von Kienlin , Julia Wagner1, Helmut Steinle1, Narayana Bhat2, Michael S. Briggs2, Roland Diehl1, Gerald J.
Fishman3, Jochen Greiner1, R. Marc Kippen4, Chryssa Kouveliotou5, Giselher G. Lichti1, Charles A. Meegan3, William
S. Paciesas2, Robert D. Preece2, Robert B. Wilson2
[1] Max-Planck-Institut für extraterrestrische Physik (MPE); [2] University of Alabama (UAH); [3] NASA/Marshall Space-Flight Center (MSFC), [4] Los Alamos National Laboratory (LANL), [5] USRA
Introduction:
The GBM-BGO Detectors (2 x):
The GBM-NaI(Tl) Detectors (12 x):
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Calibration Results:
List of Calibration Sources:
Purpose of Calibration:
The figures below summarize the main measurements performed with the flight
detectors. All detectors of the same type showed nearly the same performance
and all fulfilled the specified requirements.
- provide performance verification of the GBM detectors.
- provide benchmark data to compare with calculated detector
response data.
- provide accurate, well-characterized data for subsequent scientific
analysis.
GBM-NaI detector
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GBM-BGO detector
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Channel-Energy Relation (parabola)
Channel-Energy Relation (line)
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Energy [keV]
The Calibration Setup:
- allowes the acquisition of spectra at different angles of incidence.
- high accuracy due to laser adjustment.
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Energy [keV]
The next large NASA mission in the field of gamma-ray astronomy,
GLAST, is scheduled for launch in September 2007. Aside from the
main instrument LAT, a gamma-ray telescope for the energy range
between ~20 MeV and ~300 GeV, a secondary instrument, the
GLAST burst monitor (GBM), is foreseen. Its task is to increase the
detection rate of gamma-ray bursts for the LAT and to extend the
energy range of the main instrument to lower energies (from ~10
keV to ~30 MeV). The GBM consists of 12 thin NaI-plates, which
allow the determination of the angle of incidence of the gamma
radiation. These crystals are sensitive in the energy range between
~10 keV and ~1 MeV. Two additional BGO detectors, which are
able to detect gamma-rays in the energy range between ~150 keV
and ~30 MeV, are responsible for the overlap in energy
measurement with the LAT main instrument and the NaI detectors.
All flight detectors were already delivered to NASA. This poster
gives an overview of the calibration measurements performed by
MPE at the detector level before delivery.
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Channel
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Residuals [keV]
Residual [keV]
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Channel Number
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Typical Spectra:
GBM-NaI detector
GBM-NaI detector
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Background-subtracted NaI- and BGO-spectra, recorded at
an angle where the detector effective area is maximal (0º).
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Linearity of the Channel-Energy Relation
- deviation from parabolic relation
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GBM-NaI detector
 Energy [%]
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Co: 122.06 keV (85.6%) + 136.47 keV (10.7%)
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Counts/Channel
Counts/Channel
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GBM-BGO detector
Cs: 661.66 keV
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 Energy [%]
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Linearity of the Channel-Energy Relation
- deviation from linear relation
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Co: 14.41 keV (9.2 %)
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Energy [keV]
Energy [keV]
Channels
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GBM-NaI detector
GBM-BGO detector
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The installation of an 0.7 mm thick silicon pad between the
Beryllium entrance window and the crystal was necessary so that
the brittle NaI crystal is able to survive the environmental
conditions during launch. This additional silicon layer caused
unfortunately a degradation of the transmissivity at low energies
(at 10 keV ~ 30%).
Hg: 279.2 keV
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Na: 1274.54 keV
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Tl-L 11.1 keV
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Realtive Energy Resolution (FWHM)
Arrows: Requirements
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GBM-BGO detector
GBM-NaI detector
Irradiation with
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Channels
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Channels
The effect of magnetic fields on the shielded NaI-EQM
module was tested from -2 G to + 2 G in 0.5 G steps at the
IABG’s MFSA facility. Result: The GBM response will not
be affected by the magnetic torquers of the GLAST S/C
Performed at the BESSY synchrotron in Berlin with 4 FM-NaIs:
Determination of absolute efficiency at low energies (8- 60 keV) and
test of response around Iodine K-Edge
GBM-NaI detector
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Bessy: 40 keV
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GBM-NaI detector
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Effective Area [cm ]
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Cs Peak
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Position of
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Location of
PMT A
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Relative Response as a
Function of the Off-Axis Angle
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Source Angle [deg]
Iodine Escape Peaks:
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Channels
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Energy [keV]
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Source Angle [deg]
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Location of
PMT B
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Location of
PMT + FEE
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GBM-BGO detector
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NaI Low Energy Calibration:
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Relative Response as a
Function of the Off-Axis Angle
Detector Magnetic Susceptibility:
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Energy [keV]
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Photon Energy [eV]
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Am/ Be: 4.430 MeV
FWHM:
Cs: 661.66 keV
Channel: 2749
FWHM: 10.1 %
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C
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Energy [keV]
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Integrated Counts of Photopeak
Be: 200 m
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Silicone Pad: 700 m
NaI: Sum
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Integrated Counts of Photopeak
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Counts/Channel
Counts/Channel
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Am/ Be source:
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The Be(,n) C reaction produces the first excited state of
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C* ->  (4.43 MeV) + C (ground state)
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Relative Energy Resolution (FWHM)
Arrows: Requirements
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Cs: 32.89 keV
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Channels
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Transmission
Na: 511 keV
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Counts/Channel
X-ray Transmission of the NaI Entrance Window:
Counts/Channel
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FWHM [ E/E in %]
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FWHM [ E/E in %]
Tl-SumK 72.11 keV
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Angle
For further information, please contact: [email protected]
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