Satoshi KODAIRA,

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Elemental distribution of ultra-heavy nuclei in
cosmic-rays from TIGER experiment

• Satoshi KODAIRA,
• Advanced Research Institute for Science and
  Engineering, Waseda University
• (one-year masters degree student at
  Hasebe-laboratory)

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Whats TIGER ?
Trans-Iron Galactic Element Recorder (TIGER)

• Balloon Experiment at Antarctic Pole
• First observation of trans-iron nuclei (Z gt 30)
  in cosmic-ray with high resolution
• Washington University, CALTECH GSFC

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Observation of Cosmic-Ray
Nuclear Component
Nucleosynthesis in the Star Supernovae,
Wolf-Rayet star, AGB star Injection of
Cosmic-Ray nuclei FIP or Volatility ?? (ISM
materials and/or SN ejecta) Acceleration of
Cosmic-Rays Where, When, How?? Propagation of
Cosmic-Rays Path-length, nuclear transformation,
modulation Observation of Cosmic-Rays around or
in the Earth
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TIGER Instrument

• Scintillation Counter D E
• Hodoscope Trajectory
• Cherenkov Counter b

C0 Aerogel (n1.04) C1Acrylic (n1.5)
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Detector signals

• Cherernkov light signal,

Z nuclear charge, b ? n/c, nreflection index

• Scintillation light signal,

Using these signals, we can determine the nuclear
charge and energy of a particle.
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Data sets
Energy of Charged particle is determination from
Cherenkov Thresh Hold Energy information.

• Above C0 E ? 2.5 GeV/n
• b is almost constant.
• both C1(Acrylic) and C0(Aerogel) respond.
• ? Possible to identify the nuclear charge Z from
  only C1 and C0 signals.
• Below C0 320 MeV/n ? E ? 2.5 GeV/n
• b shifts.
• Only C1(Acrylic) respond.
• ? Using C1 and S signals, identify the nuclear
  charge Z.

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Flight data in 2001

• December,2001 Antarctica 31.8days
• (We analyzed the data of 40.75 hours. )
• Average altitude about 36km (118000 ft)
• Average depth about 5 g/cm2 (4.05 g/cm2 for this
  analysis.)

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Antarctica Pole in Summer

• Wind blows around Pole.
• Sun does not set.
• Height difference is very small,
  because the temperature variation is
  very small.
• Useable the solar battery.

Long Flight

• Geomagnetic cut-off rigidity is very small.
• 0.2 GV on average, because of the latitude
  of 80?

About 2 rounds
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Zenith angle of the incident ions
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E ? 2.5 GeV/n (C0 v.s. S1?S2)
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320 MeV/n ? E ? 2.5 GeV/n (C1 v.s. S1?S2)
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Charge identification (E ? 2.5 GeV/n)
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Charge distribution for E ? 2.5 GeV/n
counts
Charge Z
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Charge identification (320 MeV/n ? E ? 2.5
GeV/n)
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Charge distribution for 320 MeV/n ? E ? 2.5 GeV/n
counts
Charge Z
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Nuclear interaction mean free path
At the first, we calculated the m.f.p of Fe
nuclei.
Abundant of trans-iron nuclei is very small.
? Not produced Fe nuclei from the
fragmentation.
Fe events are decreasing with atmospheric depth
? Flux of Fe nuclei is a function of
atmospheric depth.
From atmospheric depth (g/cm2) whose events
are to be 1/e, we calculate the interaction mean
free path for Fe nuclei.
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Zenith angle and atmospheric depth
TIGER
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Geometric Factor
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Zenith angle for all Fe nuclei
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Interaction mean free path for Fe (all)
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Result

• Nuclear Interaction Mean Free Path
• (Atmospheric depth 4.050.40 g/cm2)
• All
• 13.1 ? 1.31 g/cm2
• Above (E ? 2.5GeV/n)
• 13.3 ? 2.98 g/cm2
• Below (320MeV/n ? E ? 2.5GeV/n)
• 11.9 ? 2.53 g/cm2

• Comparison of the previous experiment
• 13.1 ? 1.31 (all) lt 15.2 ? 0.5 (Crane et
  al.,1983)
  lt 13.2 ? 1.1 (Israel et al.,1979)

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problems
This calculation is not considered the chamber
efficiency. Since the slanting incidence is easy
to collide with the instrument, we must consider
the collision events with the thickness of the
detectors. It is necessary to calculate the
interaction mean free path of sub-Fe nuclei as
well as Fe nuclei.
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Problems for propagation of CR
Solution for propagation of CR ?
Path-length of CR in the galaxy.
(Leaky Box Model )
Energy spectrum for sub-Fe/Fe ratio.
Coefficient index is relative to R-a,
a 0.6
a 1/3
e.g.
Energy spectrum for sub-Fe/Fe ratio is very
important to understand the propagation mechanism
and model.
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Below data (320 MeV/n ? E ? 2.5 GeV/n )
I fitted the charge histogram with the gaussian.
counts
Charge Z
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Energy spectrum for sub-Fe/Fe ratio
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Problems
This calculation is not considered the
contamination of fragments interacted with the
air. Since we do not know the energies of the
individual particles, we cannot separate some
energy regions. (We want to know each energy of
the particle ! )
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Rough estimation of the contamination
Production rate and sampling data in
SANRIKU-experiment of RUNJOB. From this data,
contamination of sub-Fe nuclei at about 4 g/cm2
is calculated roughly 20 . Therefore, the ratio
of TIGER data point in spectrum will be down
about 20 .
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Result
The preliminary ratio of sub-Fe/Fe at the
energy of 320 MeV/n ? E ? 2.5 GeV/n from TIGER,
0.391 ? 0.007 In consideration of roughly
estimated contamination, the ratio will be down
about 20 . We will calculate exactly the
contamination rates. Since we want to separate
over about 3 regions in Below energy region, we
want to know each energy of the
particle. Future, we want to analyze more data
and to study the Cosmic-Rays physics.