Radioprotection in space

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Radioprotection in space

Vincenzo Patera - Rome University “La Sapienza”

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Summary

• Radiation in space ( not only…)

• Radiation damage to human cells

• Radiation risks in space mission

• Shielding

• Radiation in atmosphere

• Conclusions

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• Radiation is the main hindrance to safe human space exploration

• OVERALL OBJECTIVE

– To allow exploration and colonization of the Solar system with acceptable risk from space radiation exposure

Cosmic Radiation Risks for Human Exploration of the Solar System

Beyond radiation protection:

Astrobiology

Plant breeding in space

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What do we need to know in space radiation for interplanetaryspaceflight?

§ Risk estimation for humans in space Ø

Acute effect

Ø Late effects

ü CNS damage ü cataracts

ü cancer

§ Radiation effects on

non-biological material Ø

Shielding

Ø Radiation hardening Ø Single even upsets in electronic devices

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Cosmic Rays

• We are embedded in a continuous bath of particles

coming from Sun, galactic sources, extragalactic sources.

• The energy associated to this kind of radiation adds up to 1/3 of the estimated “normal” energy ( non dark energy) of the universe

• The source are cosmic objects like active galactic nuclei, supernovae plus other space “monsters”

• The relevant part of CR for radioprotection in space is the charged component originating the Sun and from our

Galaxy

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From very very far … right to us

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Watch out: we are X-ed by 100 charged particles from

CR per second!!!

NB: deflected by the magnetic field in the

galaxy

Flux of the CR (source:

Sven Lafebre)

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High energy (extragalactic) CR

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Cosmic ray flux and energy scales Cosmic ray flux and energy scales

Impressive.. But few

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Ultra-high energy: 10

²⁰

eV

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Need accelerator of size of Mercury´s orbit to reach 10²⁰ eV with current technology

Large Hadron Collider (LHC), 27 km circumference,

superconducting magnets

Ultra High Energy Cosmic Rays - Accelerators

!

need ILC (35 MV/m)

L= diameter of Saturn orbit

!

alternatively built LHC around Mercury orbit

!

astrophysical shock

acceleration less efficient...

(M. Unger, 2006)

Acceleration time for LHC: 815 years

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spectrum: 87% protons, 12% He ions and 1% heavier ions (in fluence) with peaks at 1 GeV/n

flux: ~4 particles/(cm² s) at solar min.

spectrum: 90% protons, 10% heavier ions with energy mainly below ~200 MeV flux: up to ~10¹⁰ particles/cm² in some hrs.

dose: order of Sv, strongly dependent on shielding and organ

Galactic Cosmic Rays

NASA pub. 1998 NASA pub. 1998

Solar Particle Events

dose:

~1 mSv/day

Relevant Radiation sources in space

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Acute Radiation Syndrom

10 Source: "Radiation

Exposure and Contamination".

Merck Manuals.

From WIKIPEDIA, not accurate, but fair

“take home message”

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Radiation field in Space

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Trapped radiation: Van Allen belts (electrons, protons up to 600 MeV)

l

Solar radiation: about 90% protons, E<1 GeV, seldom but potentially dangerous (high dose) events SPE

l

Galactic Cosmic Radiation (GCR):

Ø

2% electrons and positrons

Ø

98% particles :

Ø

87% protons

Ø

12% a particles

Ø

1% heavier ions (

HZE particles

)

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0 1 2 3 4 5 6 7

÷÷ ø çç ö

è

æ -

×

=

- g b h

b

r I

c m z

A k Z dx

dE

² ² _e ²

2

2 * log

Ionization energy loss (Bethe-Bloch formula)

56Fe, 300 MeV/n in water

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GCR contribution from different particles

Dose eq. on Earth: 10 µSv/d Dose eq. on Mars: 100-200 µSv/d

Dose eq. on Moon: 300-400 µSv/d

Dose eq. Mission to Mars (9 monthes): 1.2 Sv

*Francis A. Cucinotta (NASA, Lyndon B. Johnson Space Center), private communication

Dose (physical) D

D= DE/Dm [Gy]=[J]/[kg]

Equivanet Dose = QD [Sv]

The Q constant takes care of

the fact that not all particles

give the same contribution

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ESA UNCLASSIFIED – For Official Use | slide 14

RadioTherapy Side Effects

Courtesy of M.Durante

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Few meters of DNA packed in the 5-10 µm radius of the cell nucleus

Ionizing radiation and DNA damage

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Microscopic distribution of the X-rays dose

7 μm e- range = 15 mm

X ray = 4 MeV γ

LET = ΔE/ Δx expressed in keV/μm = eV/nm

ΔE Δx

150 ionizations/cell

d = 40 eV / LET_eV/nm= 130 nm

electron 0.3 keV/μm

SSB=

Single Strand Break

Courtesy U.Amaldi

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d=130 nm

Protons: 1. more favorable dose 2. same ‘indirect effects’

30 cm

Beam of 200 MeV protons X-rays beam

d=50 nm

d= 15 nm d=90 nm

Protons are SPARSELY IONIZING as X-rays Courtesy U.Amaldi

Different bullet, different effects

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d=130 nm

Carbon ions: 1. more favorable dose 2. ‘direct effects’

30 cm

Beam of 200 MeV protons X-rays beam

Carbon ions are DENSELY IONIZING (higher biological effectiveness)

Beam of 4800 MeV carbon ions

d= 4 nm

d= 2 nm

d= 0.3 nm

Courtesy U.Amaldi

Different bullet, different effects

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CELL SURVIVAL, DOSE, PROJECTILE AND ALL THAT..

Due to the high LET (Linear Energy Transfer ~ De/Dx), the ions are much better at killing the tumour cells with respect to the X rays for a

given dose released èhigh

RBE

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ESA UNCLASSIFIED – For Official Use | slide 21 Radiation Biophysics

SS2011 21

RBE

LET [keV/micron]

Protoni

Ioni carbonio Ioni neon

Ioni Carbonio: efficacia biologica

10 – 20 keV/ m = 100 – 200 MeV/cm = 20 – 40 eV/(2 nm)

(M. Belli et al.)

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Charged particles

g-rays

silicon

iron Cucinotta and Durante, Lancet Oncol. 2006

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GFP-NSBS1

Live cell imaging of heavy ion traversals in euchromatin and heterochromatin

Jakob et al., Proc. Natl. Acad. Sci. USA 2009; Nucl. Acids Res. 2011

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Chromosomal aberrations induced by heavy ions

3 Gy g-rays 0.3 Gy Fe-

ions

Durante et al., Radiation Research 2002

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An Analogy for Structured Energy Deposition and its Consequences

Low LET radiation produces isotropic damage to organized targets.

High LET radiation produces correlated damage to organized targets.

Low LET radiation deposits energy in a uniform pattern 1 Dose Unit

High LET radiation deposits energy in a non-uniform pattern

1 Dose Unit

LET: Linear Energy Transfer

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0.01 0.1 1 10 100 1000 10000

Dose (mSv)

1 day 1 year

Max. annual dose for rad.

workers

Dose to the tumor

1 year CT-WB

1 day

Fukushima liquidators

Guarapari beach 1 year

RADIATION DOSES Radiation effects depends on the DOSE

Dose is an energy per unit mass and is measured in Sievert = Joule/kg

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B1: RADIATION ENVIRONMENT - ISS

DOSIS 3D (2012 – ongoing): Variation of absorbed dose over ISS orbit (active radiation detectors)

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B2: PERSONAL DOSIMETRY

© NASA

Personal dosimetry: Surveillance of the radiation exposure of astro – and cosmonauts (passive)

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Radiation dose during the travel to Mars and on the planet’s surface measured by

RAD on MSL

Launch date: 26.11.2011 Landing date: 06.08.2012

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Dose summary for Mars & ISS

Radiation Biophysics seminar 2014 30

Durante, Life Sci. Space Res. 2014

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REFERENCE

o http://www.theseus-eu.org/

o Radiation risks:

o 1. Cancer

o 2. Tissue degenerative effects

• 2.1 CNS

• 2.2 Cardiovascular

• 2.3 Cataracts

o 3. Acute syndromes (SPE) o 4. Hereditary effects

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Durante & Cucinotta, Nature Rev. Cancer (2008)

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MARS RISK PROJECTIONS AT 95% CONFIDENCE LEVEL

Cancer

Acute- EVA Cancer Heart

Disease CNS Acute – IVA

CNS Acute

Heart Disease

CNS

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>10%

3-10%

1-3%

<1%

During Mission Early Post- mission

<5 years

Post-Mission 5 to 20 years

Late

>20 years

Probability

Risks at Different Times

CNS= Central Nervous System

damage IVA-EVA= Intra/Extra

Vehicular Activity

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NASA ASTRONAUTS’ CAUSE-SPECIFIC MORTALITY

Cancer Heart CNS Work Related Accidents

Other

Accidents Other causes

11 4 1 18 5 5

Total Frequency Death Frequency

Total 339 45

Male 269 41

Female 40 4

Astronaut 316 44

Payload Specialist 23 1

Astronauts excluding Flight Tragedies

Age, y

30 40 50 60 70 80 90 100

Survival

0.0 0.2 0.4 0.6 0.8 1.0

US Males NS Males Astronauts Lower 95% CI Upper 95% CI

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ability to discriminate novelty from previous situations involving either 35

similar or dissimilar objects placed at familiar or novel locations Mice: 6 weeks after being exposed to ¹⁶O or ⁴⁸Ti particles

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Dose & Dose-Rate Effectiveness factor,

DDREF

Radiation Quality (Q/RBE)

Space particle spectra, F(L=LET) Human epidemiology

data (age/gender)

Focus?

Double Detriment Life Table (US Population – age/gender)

Mission/Astronaut Specific Cancer Risk

Uncertainties

No. Studied by NCI, BEIR, etc.

Smallest uncertainty Yes, 2^nd Largest uncertainty Yes, Largest uncertainty

From Dose to Risk??

NASA radiation risk model

Tissue Specific Cancer Rate (Mortality/Incidence)

Tissue specific risk transfer, n

Yes, 3rd Largest uncertainty

Excess Relative or Additive Risk (ERR/EAR)

Assumption:

Heavy ion effects can be scaled to Gamma-rays?

Assumption:

Risk is linear &

additive over mixed high-

& low-LET env.?

Assumptions:

Sensitivity to radiation does not change in Ave. US Population and does not vary

with radiation quality?

http://spaceradiation.usra.edu/irModels/

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NASA radiation risk model

For a homogeneous population receiving an effective dose E, at age aE, the probability of

dying in the age-interval from a to a+1 is described by the background mortality-rate

for all causes of death, M(a), and the radiation cancer mortality rate, m(E,aE,a), as

The survival probability to live to age, a, following an exposure, E, at age, aE, is

The risk of radiation-induced death (REID) is the lifetime risk that an individual in the population will die from a cancer caused by

his or her radiation exposure

ERR=E/C and EAR=(E-C) (in Sv^-1) are derived from A-bomb survivors, M is the gender- and age- specific cancer mortality rate in USA; n=1/2 for solid cancer (mixture model) and n=0 for leukemia (radiation acts independently of the leukemia background risk)

Cardiovascular risk now added

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REID distribution for a mission to Mars (spiral 4, 600 days)

Durante & Cucinotta, Rev. Mod. Phys. 2011

REID= risk of exposure induced death

REID depends on the

astronauth environment->

shieldings, spacecraft

materials

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REID: gender/age dependence

REID: sex dependence

REID is larger for females than for males and decreasing with age

30% difference@30 years

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Risk of ischemic heart disease in 2168

Scandinavian women after radiotherapy for breast cancer

Darby et al., N. Eng. J.Med. 2013

Mean heart dose 4.9 Gy (0.03-27.7 Gy)

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NASA uses the risk model and set the astronauts‘ carreer limits to 3% REID within 95% CI

Dose limits

Dose limits in Sv – for NASA, the numbers are for ISS excluding cardiovascular risk

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Estimates of cancer mortality risk and 95% CI for different space mission

scenarios and terrestrial exposures.

Durante & Cucinotta, Nuclear Physics News 2014

Mars Design Reference Mission ("DRM")

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Towards a European radiation risk model

Use a different radiation transport model (Geant4, TRiP98) Use of radiobiological models for cancer risk (LEM)

New analysis of A-bomb survivors (organ doses, neutron RBE) and cardiovascular disease risk and RBE

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0 1 2 3 4 5 6 7

÷÷ ø çç ö

è

æ -

×

=

- g b h

b

r I

c m z

A k Z dx

dE

² ² _e ²

2

2 * log

Ionization energy loss (Bethe-Bloch formula)

56Fe, 300 MeV/n in water

But is not enough!

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Nuclear fragmentation

(

¹^/³ ¹^/³

)

²

2

0

A A b

r

_p

+

_T

-

= p s

Abrasion-ablation model

Geometrical approximation (Bradt-Peters formula) Energy

dependence

(

¹²

C on

graphite)

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Bragg curve + fragmentation

0 0,2 0,4 0,6 0,8 1 1,2

0 5 10 15 20 25 30 35 40 45 50

56Fe, 1 GeV/n in water

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Computing dose in Spacecraft

MC code

GCR and SPE spectra

Quality factors Yields of “Complex Lesions”

Dose

Dose Equivalent

“Biological Dose”

“voxel” phantom (Zankl et al.)

Mostly used MC code:

FLUKA GEANT4

Spacecraft material and

geometry

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Aug. 1972 SPE - calculated skin doses

Absorbed Dose (cGy)

0 1 2 3 4 5 6 7 8 9

1 2 5 10 20

Al thickness (g/cm²)

Totale Protoni primari Adroni secondari

Dose Equivalent (cSv)

0 2 4 6 8 10 12 14

1 2 5 10 20

Total Protoni primari Adroni secondari

• dose decrease with increasing shielding (i.e. from 13.3 to 0.62 Sv in the range 1-10 g/cm²)

• major contribution from primary protons (the role of nuclear reaction products is not negligible only for equivalent and “biological”

dose)

• A 1 m² slab of 10 g/cm² thickness of aluminum has a mass~ 35 kg: to shield a room of 5x5x3 m3 you need ~4 tons of material

dose (Gy) dose equivalent (Sv)

Al shield thickness (g/cm²) Al shield thickness (g/cm²)

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Aug. 1972 SPE - skin vs. internal organs

0 2 4 6 8 10 12 14

1 2 5 10 20

Total Primary Protons Secondary Hadrons

• much lower doses to liver than to skin (e.g. 1.0 vs. 13.3 Sv behind 1 g/cm² Al )

• larger relative contribution of nuclear reaction products for liver than for skin (e.g. 14% vs. 7% behind 1 g/cm² Al)

0 0.2 0.4 0.6 0.8 1 1.2

1 2 5 10 20

Total Primary Protons Secondary Hadrons

dose equivalent to skin (Sv) dose equivalent to liver (Sv)

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GCR solar min. - skin vs. internal organs

with respect to skin, internal organs have: 1) similar dose but smaller dose equivalent (~ 1.3 vs. 1.7 mSv/day); 2) larger relative contributions from nuclear interaction products

skin liver

0 0.1 0.2 0.3 0.4 0.5 0.6

0.3 1 2 3 5

Al thickness (g*cm^-2)

mGy*d-1

Total Primary Ions Secondary Hadrons Electromagnetic

0 0.1 0.2 0.3 0.4 0.5 0.6

0.3 1 2 3 5

mGy*d-1

0 0.5 1 1.5 2

0.3 1 2 3 5

mSv*d-1

0 0.5 1 1.5 2

0.3 1 2 3 5

mSv*d-1

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GCR at solar min. - annual effective dose

0.3 0.47 0.43 1 0.47 0.44

2 0.46 0.41 3 0.43 0.41 5 0.42 0.42

Al (g/cm²)

male dose (Sv)

fem. dose (Sv)

the “effective dose” E is a sum over different organ doses,

weighted by “tissue weighting factors”

gonads: 0.20

bone marrow, colon, lung, stomach: 0.12

bladder, breast, liver, esophagous, thyroid: 0.05 skin, bone surface: 0.01

others: 0.05

ICRP 60, 1990

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“Best” shielding materials

Projectile interactions per unit target mass:

Ionization ~ Z/A (Bethe-Bloch formula)

Fragmentation ~ A

^-1/3

(Bradt-Peters formula)

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Is shielding a solution?

Aluminum ~ 30%

Polyethylene ~ 50%

Liquid hydrogen ~ 90%

Max GCR dose

reduction

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Shielding on ISS

• Sleep station outfitted with PE and water

• Thin, flat panels are PE shields

• Stowage water packaging above the sleep station

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ROSSINI experiment

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Bragg curves measured at NSRL using Fe 1 GeV/n

0,0 0,2 0,4 0,6 0,8 1,0 1,2

0 5 10 15 20 25 30 35 40

Areal density (g/cm²)

Normalized dose

Polyethylene Kevlar

Nextel Aluminum

Radiation Biophysics SS2011 60

% dose reduction is proportional to shielding

thickness

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Percent Dose Reduction per Unit Areal Density for Single Materials Fe56 962.8 MeV/n - NSRL/BNL Brookhaven 23/06/2012

0 1 2 3 4 5 6

Cella Energy B Cella Energy A Polyethylene HDPE

Kevlar Moon Regolith Aluminum Mars Regolith Moon Concrete Nextel

% Dose reduction cm^2 g^-1

Shielding test results, ROSSINI-1, 2012-14

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Active shielding

• Earth’s magnetic field is effective in shielding SPE and GCR

• Unconfined magnetic fields

represent an attractive possibility for space radiation shielding

• SPE are highly directional:

superconducting magnetic lenses

• Toroidal or solenoidal?

• Effective for GCR?

• High-temperature superconductors

may provide a large impact in this

field

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Radiation Biophysics SS2011 63

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“Pumpkin”

structure Burger et al. Front. Oncol. 2016

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Radioprotection & space.. Not only humans

The Single Upset Event can cause mis-functioning of semiconductors via a “spin flip” of logic memories. But usually the memories has parity check to detect this kind of problems:

1 0 1 1 1

4 bits P bit

1 0 0 1 1

SEU

Heavy ions fragmentations on shield can cause Double Upset Event -> spin-flips cannot be easily detected by parity check

1 0 1 1 1

4 bits P bit

1 0 0 0 1

DEU

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Not only in space….. also in the air!

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Cosmic ray interactions Cosmic ray interactions

low- and low- and

medium energy:

inclusive flux inclusive flux of secondary of secondary particles

particles

high energy:

extensive air extensive air

shower shower

Typical energies in Typical energies in atmosphere:

atmosphere:

ch.πch.π's: ~150 GeV's: ~150 GeV kaons: ~600 GeVkaons: ~600 GeV neu.neu.ππ's: ~10's: ~10⁹⁹ GeV GeV

CR in

atmosphere:

EAS

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Characterization of extensive air showers Characterization of extensive air showers

Shower particles:

mainly e mainly e^±^±,γ,γ

80 – 95% of primary 80 – 95% of primary energy converted to energy converted to ionization energy ionization energy Up to 10

Up to 10¹¹¹¹ charged charged particles

particles

∫

h

∞

l  dl= X h

Atmospheric depth:

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Shower particle tracks: proton

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Particle tracks: different viewing Particle tracks: different viewing

angles angles

Proton.gif

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Dosimetry Applications

Ambient dose equivalent from neutrons at solar maximum on

commercial flights from Seattle to Hamburg and from Frankfurt to Johannesburg.

Solid lines: FLUKA simulation

Roesler et al.,

Rad. Prot. Dosim.

98, 367 (2002)

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