Balloon flight experiment for GLAST

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Balloon flight experiment for GLAST
Uno S., Mizuno T. (Hiroshima Univ.), Kamae T.
(Hiroshima Univ./ SLAC), Hirano K., Mizushima H.,
Ogata S., Ohsugi T., Fukazawa Y.(Hiroshima
Univ.), Ozaki M. (ISAS), Thompson D., Ormes J.
(NASA/GSFC), Johnson N., Lovellette M.(NRA),
Godfrey G., Russel JJ. (SLAC), Williams S.,
Lauben D. (Stanford Univ.), Johnson R.(UCSC), and
other GLAST balloon team.
Balloon Flight for GLAST
GLAST (Gamma-ray Large Area Telescope)
GLAST (Gamma-ray Large Area Telescope, Figure 1)
is a gamma-ray satellite that will be launched
early in the New Century, 2005. GLAST is expected
to show sensitivity 50-100 times higher than that
of the previous gamma-ray satellite (Figure 2). A
main detector of GLAST is a LAT (Large Area
Telescope), consists of a pair-conversion type
gamma-ray Tracker using Silicon Strip Detector,
Calorimeter made of arrayed CsI crystals, and
Anti-Coincidence Detector (ACD) made of plastic
scintillator.
In order to validate the GLAST in a single-tower
level, a balloon experiment is planned in this
June at Palestine, Texas. Major objectives are to
examine its ability to deal with gamma-ray events
and to reject backgrounds. Most of the
instruments are based on that used for Beam Test
performed SLAC in 1999, whereas some new
components (such as External Target, see Figure
5) will be added. Balloon Flight Engineering
Model is now under integration at SLAC .
Figure 3 A balloon ready to be launched.
Instruments are in gondola that is shown in the
near side of this picture.
Figure 2 The number of Detected objects for
previous and future high-energy astronomical
satellites. GLAST is expected to observe more
than thousands gamma-ray objects.
External Target (XGT)
Figure 1. Schematic overview of GLAST. LAT
consists of 4416 modules called Tower.
Figure 5 Plastic scintillator with
photo-multiplier tube called External Target
(XGT), a new instruments on board balloon. When
cosmic-ray hit the target and generate pi0-meson,
it will immediately decayed into gamma-rays. By
introducing XGT, we can obtain tagged gamma-ray
events.
Pressure Vessel
Figure 8 A photo of the Pressure vessel (PV). The
whole detectors of Balloon Flight are housed in
the PV with a pressure of about 1 atom.
Figure 6 XGT are developed by Japanese GLAST
group. Left figure shows its response to
cosmic-ray muon and the right one shows the
obtained spectrum.
Figure 4 BFEM under integration at SLAC, with two
graduate students from Hiroshima University.
Tracker
Calorimeter
Figure 7 A Tracker used for the Beam Test in
1999, developed by UCSC. After being applied
applying some modification, it will be used for
Balloon Flight.
Figure 8 A Calorimeter utilized for BeamTest,
developed by NRL. Each layer of CsI crystals is
arranged alternatively in two perpendicular
directions in order to get the position
information.
Objective 1 gamma-ray event from XGT
Objective 2 Background on balloon.
In order to study the detector response and to
estimate the gamma-ray event rate on Balloon, we
developed Monte-Carlo simulator based on Geant 4.
We also constructed cosmic-ray generator by
referring the paper about previous measurements
and theoretical predictions (See poster 187).
During 8-hours flight, we will obtain about 500
tagged gamma-ray events generated at targets.
A Balloon Flight for GLAST also intend to measure
background spectrum in high altitude, and to
validate the detectors ability to reject them.
With cosmic-ray generators (poster 187) and
detector simulator, we study the background.
Figure 10 A sample of the background expected on
balloon flight. A cosmic-ray electron hit the
pressure vessel and gamma-ray generated via
bremsstrahlung hit the tracker.
Figure 9 A show-case event where pi-0 decayed
gamma-ray generated at target is converted at
Tracker and deposited most of its energy in
calorimeter.