RADIOPROTEZIONE DEGLI
ASTRONAUTI DA
RADIAZIONE COSMICA
Gianfranco Grossi
Dipartimento di Scienze Fisiche
Università di Napoli Federico II
INFN - Sezione di Napoli
The places we will go
if radiation doesn’t hold us back
The Earth’s
Neighborhood
Earth and
LEO
EarthMoon L1
The
Moon
Accessible
Planetary Surfaces
SunEarth L2
Mars
Up to 180 days
Outer
Planets
Asteroids
or Other
Targets...
L1
Risk of cancer lethality
(4  8) x 10-2 per Sv
L2
Up to 100 days
Dose - rate: 1 mSv/d
500 to 1000 days
2 mSv/d
> 2000 days
3 mSv/d
The problem
Long-term interplanetary missions are planned in
the XXI century
Crews will be exposed to significant doses
delivered by high-energy charged particles, in
extreme conditions (stress, microgravity,..)
Uncertainties on radiation risk estimates in deep
space are between 400% and 1500%
Uncertainty must be reduced for safe
human colonization of the solar system
“Best” shielding materials
Projectile interactions per unit target mass:
• Ionization ~ Z/A
• Fragmentation ~ A-1/3
HZE shielding
• Shielding of heavy ions is
complicated by nuclear
fragmentation
• Projectile fragmentation
produces swift light ions
and neutrons
• Target fragmentation
produces slow, densely
ionizing ions
• Fragments have different
Q than primary ions
GCR shielding - calculation by HZETRN
Max GCR dose
reduction
Aluminum ~ 30%
Polyethylene ~ 50%
Liquid hydrogen ~ 90%
The SHIELD experiment
• SHIELD started in 1999: 4 Italian research Institutes,
NASA JSC, BNL, and NIRS (Japan)
• Goal: study of biological effects of heavy ions with
shielding
• Results of experimental studies can be used to
benchmark the codes
• Different biological endpoints (CA, SV, DNA DSB)
shield materials (LDPE, PMMA, C, Al, Pb) and
thickness (2 - 30 g/cm2), ion (H, C, Fe, Si, Ti) charge
and energy (0.3 - 5 GeV/n)
• Results presented here are relative to the induction
of chromosomal aberrations in human lymphocytes
exposed to 56Fe projectiles with different shields
Chromosomal aberrations measured by
FISH in PCC from human lymphocytes
Translocations involving chromosome 4 (left) and
 2 (right). In light green chromosome 1, in red
chromosome and in dark green chromosome 4
Nuclear fragmentation
56
of AGS-BNL Fe beams
5 GeV/n 56Fe
5 GeV/n 56Fe + 25 cm PMMA
CR39 nuclear plastic detector
CA / 1 GeV/n 56Fe-particle
vs. shield thickness
Effectiveness per Fe-particle incident on the shield is
dependent on beam fragmentation, and is determined by
combination of dose/particle and RBE-LET relationship
In-flight shielding test
• Best candidate shielding materials from acceleratorbased research should eventually be tested onboard
against the whole spectrum of trapped and galactic
radiation
• ESA has recently approved two experiments to study
shielding in orbit using the detectors ALTEINO and
MATROSHKA on International Space Station
• Two experiments (ESCHILO and RADIS) will flight in
2006-07 to test the shielding effectiveness of new
composite materials and, for comparison,
polyethylene.
Shielding on ISS
Sleep station outfitted with polyethylene and water
Thin, flat panels are polyethylene shields
Stowage water packaging above the sleep station
ESCHILO
(Esperimento di Schermatura in Low Orbit)
• Measurements of
shielding on ISS (INFN,
University Tor Vergata,
Alenia Spazio,
University Federico II)
• PI: Marco Casolino
• Detector: ALTEINO on
ISS
• Shield: two multimaterial
tiles divided into 4
sections
RADIS (Radiation Distribution)
• Large (23 Institutes, led by
DLR, Germany) scientific
collaboration to use
MATROSHKA inside the ISS
(from May 2005)
• University Federico II is
supposed to provide
shielding materials to cover
MATROSHKA and measure
the changes in dose, flux,
radiation quality, etc. at
various depths in the
phantom.
Marco Durante
Giancarlo Gialanella
Gianfranco Grossi
Lorenzo Manti
Mariagabriella Pugliese
Paola Scampoli