Evaluation of Various Material Properties to Shield from Cosmic Radiation Using FLUKA Transport Code Roman Savinov GRADUATE SEMINAR CAL POLY April 7, 2016
Presentation Outline Thesis Statement Background Fluka Thesis Goals Work Done Remaining Work
Thesis Statement The purpose of this thesis is to: use a transport code in order to model various space radiation conditions study shielding effectiveness of certain materials determine if combination of various materials together affects overall shielding effectiveness.
Background Definition of Units Electron Volt (ev) Common unit of energy in physics 1 ev = 1.6 10 19 joules Absorbed Dose: gray (Gy) Unit of ionizing radiation used as a measure of absorbed dose 1 Gy = 1 J/kg Dose Equivalent: sievert (Sv) measure of health effect Sv = [quality factor]*[gy]
Background Radiation Effect on Humans and Shielding From It Phase Radiation is especially important for manned missions Only Apollo missions operated outside Earth magnetic field Cruise to Mars exceed limit for 30 years old astronaut What was proposed: hydrogen rich materials (polymers) use waste for shielding Duration (yr) MSL Data (csv/yr) Resultant Career Effective Dose (csv) Enroute (both way) 1 67.2 67.2 On surface 1.5 23.36 35.0 Age at Exposure (yr) Permissible Limits (Career Effective Dose) E(cSv) for a 3% REID Males Females 30 62 47 35 72 55 40 80 62 45 95 75 50 115 92 55 147 112
Background GCR Galactic Cosmic Rays SPE Solar Particle Event Source of Radiation Type of Radiation Composition Energy Range Comment Supernova explosion neutron stars pulsars GCR Protons 90% 9% nuclei of heavier elements α particles approach 3 10 20 ev Constantly present Coming from all directions Major threat Changes with solar activity Sun SPEs Solar Wind Mostly protons Electrons Protons α particles approach 100 MeV 1.5 and 10 kev Unpredictable Most frequent during high solar activity Constantly present Low energy
FLUKA Transport Code Transport Code software package for simulating particle interactions FLUKA (FLUktuierende KAskade) Monte Carlo simulation package for the interaction and transport of particles and nuclei in matter Used by European Organization for Nuclear Research (CERN) Calculates probability distributions to describe particle matter interaction
Thesis Goals Learn FLUKA to be able to - input various types of radiation source (SPE and GCR) - use measuring tools available in FLUKA (fluence and dose) - obtain a normalization factor (manually or using reported Fluka results) - input materials not available in FLUKA such as compounds, alloys, porous materials, etc. Validation of FLUKA results - obtain a good match between the radiation source spectrum and the measured fluence spectrum (SPE and GCR) - obtain results that would be in a good agreement with the results of a published paper Compare Different Materials for their Shielding Effectiveness Find a material (combination of materials) that have highest radiation shielding efficiency
Modeling an Experiment Two models of the target: spherical cylindrical Two models of a radiation source: Solar Particle Event (SPE) monodirectional pencil beam protons only different solar events Galactic Cosmic Rays (GCR) Spherical Protons, heavy element nuclei (He, C, Fe)
Validation of FLUKA Results Make sure the source and measured spectrums are in good agreement (SPE source) source
Validation of FLUKA Results Make sure the source and measured spectrums are in good agreement (SPE source) source detector
Validation of FLUKA Results Make sure the source and measured spectrums are in good agreement (SPE source) target source detector
Validation of FLUKA Results Make sure the source and measured spectrums are in good agreement (SPE source) target source detector
Validation of FLUKA results Make sure the source and measured spectrums are in good agreement (GCR source) Protons 90% 9% nuclei of heavier elements α particles
Validation of FLUKA Results Dose distribution inside target (published vs FLUKA) SPE is a source compared with other transport codes two solar events were considered both FLUKA output fit OLTARIS result
Compare Different Materials For Their Shielding Effectiveness to make sure I correctly define a compound manually area density of target: 35 g/cm 2
Compare Different Materials For Their Shielding Effectiveness FLUKA from paper air * Hydrogen D. Rapp, Radiation effects and shielding requirements in human missions to the moon and Mars, Mars, vol. 2, pp. 46 71, Sep. 2006. * gases are at NTP
Remaining Work Learn how to obtain a normalization factor any FLUKA output is given per primary particle Reason: to eliminate the dependence on an arbitrary parameters chosen for an experiment (such as energy bin size) need to find a normalization factor to get rid of that primary Find a material (combination of materials) with highest radiation shielding efficiency - porous material filled with hydrogen? - test hydrogen rich materials Finish thesis paper
QUESTIONS?