RADIOPROTEZIONE DEGLI RADIOPROTEZIONE DEGLI ASTRONAUTI DA ASTRONAUTI DA

RADIAZIONE COSMICARADIAZIONE COSMICA

Gianfranco GrossiDipartimento di Scienze Fisiche

Università di Napoli Federico II

INFN - Sezione di Napoli

Mars TheMoon

Earth-Moon L1

Asteroids or Other Targets...

Earth and LEO

The Earth’s Neighborhood

Accessible Planetary Surfaces

Outer Planets

Sun-Earth L2

LL11

LL22

Up to 180 days

500 to 1000 days > 2000 daysUp to 100 days

Dose - rate: 1 mSv/d 2 mSv/d 3 mSv/d

The places we will goif radiation doesn’t hold us back

Risk of cancer lethality(4 8) x 10-2 per Sv

The problem

Long-term interplanetary missions are planned in Long-term interplanetary missions are planned in the XXI centurythe XXI century

Crews will be exposed to significant doses Crews will be exposed to significant doses delivered by high-energy charged particles, in delivered by high-energy charged particles, in extreme conditions (stress, microgravity,..)extreme conditions (stress, microgravity,..)

Uncertainties on radiation risk estimates in deep Uncertainties on radiation risk estimates in deep space are between 400% and 1500%space are between 400% and 1500%

Uncertainty must be reduced for safehuman colonization of the solar system

““Best” shielding materialsBest” shielding materials

Projectile interactions per unit target mass:• Ionization ~ Z/A• Fragmentation ~ A-1/3

HZE shieldingHZE 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 HZETRNGCR shielding - calculation by HZETRN

Aluminum ~ 30%

Polyethylene ~ 50%

Liquid hydrogen ~ 90%

Max GCR dose reduction

The SHIELD experimentThe 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 Chromosomal aberrations measured by FISH in PCC from human lymphocytesFISH 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 Nuclear fragmentation

of AGS-BNL of AGS-BNL 5656FeFe beams beams

5 GeV/n 56Fe

5 GeV/n 56Fe + 25 cm PMMA

CR39 nuclear plastic detector

CA / 1 GeV/n1 GeV/n 5656FeFe-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 testIn-flight shielding test

• Best candidate shielding materials from accelerator-based 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 ISSShielding on ISS

Sleep station outfitted with polyethylene and waterThin, flat panels are polyethylene shieldsStowage water packaging above the sleep station

ESCHILOESCHILO((EEsperimento di sperimento di SchSchermatura ermatura iin n LLow ow OOrbit)rbit)

• 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 (RADIS (RaRadiation diation DisDistribution)tribution)• 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 DuranteGiancarlo GialanellaGianfranco GrossiLorenzo MantiMariagabriella PugliesePaola Scampoli