General Introduction
Last update 2022/03/25

1

Development Team Members

T. Sato1, Y. Iwamoto1, S. Hashimoto1, T. Ogawa1, T. Furuta1, S. Abe1,T. Kai1, Y. Matsuya1, N. Matsuda1, Y. Hirata1, Lan Yao1,Pi-En Tsai1*,
H. Ratliff1**, H. Iwase2, Y. Sakaki2, N. Shigyo3, L. Sihver4, K. Niita5
1. Japan Atomic Energy Agency, JAEA, Japan
2. High Energy Accelerator Research Organization, KEK, Japan
3. Kyusyu University, Japan
4. Technische Universität Wien, Austria
5. Research Organization for Information Science and Technology, RIST, JapanCurrent affiliation: *LBL, USA; **HVL, Norway

2

Table of Contents
1. General Features of PHITS
2. Physics Models
3. Applications of PHITS
2.1 Design of radiation facilities
2.2 Radiation Therapy & Protection
2.3 Space Research
2.4 Other Applications

4. Summary3

What is PHITS?
Particle and Heavy Ion Transport code System

Capability
Transport and collision of nearly all particles over wide energy range
neutron, proton, ions,10-4 eV to 1 TeV/nusing Monte Carlo method
electron, photon etc

All-in-one-Package
All contents of PHITS (source files, binary, data libraries,graphic utility etc.) are fully integrated in one package
Available in free of charge by submitting application form via PHITS website

Applications

Accelerator Design

Radiation Therapy & Protection

Space & Geoscience4

What is Monte Carlo method?
Trace each particle motion using random number, andestimate their average behavior by iterating the simulation
Go outside

Material
Next history

Transport
Transport

Transport Collision
Next history

Stop

Transport
Collison
Secondary History
particle(Cross section & Stop
Transport
randomnumber)Transport

Go outside Behavior of each particle is highly stochastic issue
 Average behavior is getting closer to the realistic
 Monte Carlo method is time consuming, but accurate!
5

Example of PHITS Calculation

AirConcrete

Motion of 100,000 photons produced from 137Cs simulated by PHITS
Average of all particle behaviors → mean particle fluence → shielding ability
6Basic Features of PHITS Source code: Fortran (Intel Fortran, gfortran) Input file: PHITS original language in free-format text
You do not have to write Fortran program nor compile PHITS Geometry• General Geometry (GG) format• Graphic utilities• Support software:(ParaVIEW*, SuperMC**) Tally functions

ANGEL output (2D & 3D)

PHIG-3D (GUI)Particle fluence, absorbed dose, number of interaction, nuclide yield etc.

 Output Data
Text data, histograms, contour maps

 Platforms
Windows, Mac and Linux (MPI & OpenMP parallelization available)*Visualize PHITS geometry & tally results **Convert CAD geometry to PHITS input format

7

Table of Contents
1. General Features of PHITS
2. Physics Models
3. Applications of PHITS
2.1 Design of radiation facilities
2.2 Radiation Therapy & Protection
2.3 Space Research
2.4 Other Applications

4. Summary

8

Physical Processes
included in PHITS

Collision &decayprocesses

Transport
processDecay
Transport

Collision

Nuclearinteraction• High-energy spallation reaction• Photon and muon-induced reaction• Absorption, resonance, fission reaction

Atomicinteraction• Photo-electric, Compton, pair production• Møller/Bhabha scattering, Annihilation• Bremsstrahlung• Knock-out electron (δ-ray) production• Ionization/excitation （track structure mode)

Particledecay• Decay with lifetime (neutron, μ, π etc.)

Ionization/ excitation• Continuous slowing down approximation• Energy & angular struggling

External field/ reflection• Electric / magnetic field• Gravity• Reflection (super mirror etc.)
9Map of Models Recommended to Use in PHITS
Proton, Pion(other hadrons)

Neutron

NucleusLow ← Energy → High

1 TeV

Muon

e- / e+Photon
1 TeV

1 TeV/uIntra-nuclear cascade (JAM)+ Evaporation (GEM)

JAMQMD+ GEM

3.0 GeV

Intra-nuclear cascade (INCL4.6) d+t
Evaporation (GEM)
3He

20 MeV

Quantum
MolecularDynamics(JQMD)+ GEM

VirtualPhotoNuclear
JAM/JQMD+GEM
200 MeVEGS5EGS5oror
EPDL97
Trackstructure

αNuclear
10 MeV/uATIMA+
Data Library
1 MeV
Energy loss
Original(JENDL-4.0)
by ATIMA or track structure
1 keV
1 keV 1 keV+Muonic atom Track(EGM)+ Capture structure

0.01 meV

PhotoNuclear
JAM/
JQMD
+
GEM
+
JENDL
+
NRF

1 meV

Physics models of PHITS and their switching energies
Switching energies can be changed by input file of PHITS10JQMD (JAERI Quantum Molecular Dynamics) Model• JQMD can dynamically simulate the time evolution of nuclear reactions,considering the correlations between every combination of nucleons.
• Dedicated to simulation of ion-induced nuclear reactions
12C(NatC,n)@100MeV/n

Precisely reproduce
residual nuclide yields (↑)
and secondary neutronproductions (→)
K. Niita et al, Phys. Rev. C52 (1995) 2620,

56Fe 800 MeV/u on 208Pb

T. Ogawa et al., Phys. Rev. C92 (2015) 024614

11

Nuclear Data Library
Cross sections for low energy neutrons strongly depend on nuclear structure
Physics models are inadequate because they cannot consider the structure
Nuclear data library evaluated based on experimental data is necessary

112Cd

113Cd

Neutron reaction cross sections of 112Cd and 113Cd taken from JENDL-4.0
 JENDL-4.0: Neutron cross sections below 20 MeV for 407 isotopes
 JENDL-4.0/HE: Neutron and proton cross sections below 200 MeV for 25 isotopes
http://wwwndc.jaea.go.jp/jendl/j40/J40_J.html
https://rpg.jaea.go.jp/main/en/ACE-J40HE/index.htm

12Event Generator Mode
What is event generator mode (EGM)?
Original sampling method of secondary particles using nuclear data library
Difference between EGM and conventional method
EGM: Sample all secondary particles from 2D energy sampling space at once,
considering energy & momentum conservation in an event
Conventional method: Sample particle by particle from 1D energy distribution
JENDL-4.0
EGM ver.1
EGM ver.2

Energy sampling space

Secondary particle yields from 150Nd(n,2n)

Indispensable in some cases such as detector response simulation
T.Ogawa et al., NIM A, 763, 575-590 (2014)13

Track Structure (TS) Mode
Energy loss of charged particle in PHITS CSDA: combine a number of ionizations and excitations as an event TS mode: explicitly consider each ionization and excitation as an event

CSDATS mode

Trajectories of 5 MeV/n C ion simulated by CSDA and TS mode
Useful for applying PHITS to radiation biology such as DNA damage estimation
Y. Matsuya et al. Phys. Med. Biol. 66, 06NT02 (2021)
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Benchmarks
Comprehensive benchmark results are published in an Open-Access paper*

Shielding calculation

Fission yield

Particle therapy

Electron range

 All input files used for these benchmarks are included in /phits/sample/benchmark
 * https://www.tandfonline.com/doi/full/10.1080/00223131.2017.1297742
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Table of Contents
1. General Features of PHITS
2. Physics Models
3. Applications of PHITS
3.1 Design of radiation facilities
3.2 Radiation Therapy & Protection
3.3 Space Research
3.4 Other Applications

4. Summary16

Useful Functions for Facility DesignVariance reduction techniques Weight window generator
 Cell importance method

Electro-magnetic fields
 Dipole & quadrupole magnet
 Wobbler magnet
 Parallel electric field Complex field map in xyz or r-z coordinateOthers
 Direct calculation of operational and protection
quantities such as H*(10) & Effective dose

Quadrupole magnet
Protonbeam

 Sensitivity analysis based on ANOVA Estimation of time evolution of induced activity
considering decay chains of RI
 Phase space source based on RMS emittance Coupling with thermal analysis

PHITS + Ansys Fluent
17Design of J-PARC facilities
Japan Proton Accelerator Research Complex

 Constructed in Tokai-mura as the joint project between JAEA and KEK
 Consists of several proton accelerators with energies up to 30 GeV
 Used for various purposes such as particle physics and neutron generation
8 GeVproton

3D geometry view and flux distribution around COMET experimental facility
COMET searches for coherent neutrino-less conversion of a muon to an electron
Courtesy of COMET experiment team (https://comet.kek.jp/)18

Design of Neutron Beam Line
Material and Life science experimental Facility (MLF) in J-PARC
3 GeV protons on Hg target

2D & 3D geometry views and dose distribution around a neutron beam line

Special functions for neutron beam line design• Duct source option: Special variance reduction technique for long beam line
• Mechanical & optical devices: Multipole magnets, T0 chopper, Super mirror• Gravity: Cold neutrons gradually go down to the ground direction
https://j-parc.jp/c/en/facilities/mlf/index.html

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Design of RI Beam Factory
 Constructed by RIKEN for accelerating various unstable nuclides up to U Nihonium (Z=113) was discovered in this facility
Shielding design

Activation calculation

beam

Observed isotopes

Yield / 238U beamtargetProton number

10-7

10-9

Neutron number

Yields of RI generated by 238U beam
Dose distribution around BigRIPS**In-flight RI beam separator

Function to plot the yield
distribution on the nuclear chart

Tanaka et al. Progress in Nuclear
Science and Technology 4, 201 (2014)

Akashio et al. EPJ Web of Conferences
153, 01022 (2017)20

Design of Tokamak Fusion Device
Accurate prediction of heat, defect, and activation in complex
Tokamak fusion device geometry is indispensable for its design

3D view of JT-60

Neutron flux distributions in the vicinity of device
with / without considering shielding effect

A. Sukegawa et al. Prog. Nucl. Sci. Technol. 1, 36-39 (2011)21

Design of Other Facilities
Particle therapy

Diagnostics

Laser acceleratorPHITS + ParaVIEW

Fukui Prefectural Hospital
Proton Therapy Center

CT room in Kyushu
UniversityJ-KAREN laser system in
QST Kansai

Satoh et al. J. Nucl. Sci.
Technol. 49, 1097 (2012)

Fujibuchi et al. Japanese J.
Radio Tech 75, 1297 (2019)

Sakaki et al. Rev. Sci Instr.
85, 02A705 (2014)

Used for getting the permission from Nuclear Regulation Authority in Japan
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Table of Contents
1. General Features of PHITS
2. Physics Models
3. Applications of PHITS
3.1 Design of radiation facilities
3.2 Radiation Therapy & Protection
3.3 Space Research
3.4 Other Applications

4. Summary23

Useful Functions for Medical Application
RI source generation function
Reproduce the decay of any RI with or without
considering the contributions from its daughter
nuclides, based on ICRP 107

ICRP
110

ICRP
145

Voxel & mesh phantoms
 Represent fine structures of human body byvolume pixels (voxel) or tetrahedral meshes Special algorithm to reduce the computationaltime of particle transport in tetrahedral mesh*

Voxel & mesh phantoms

Microdosimetric function
Special tally named [t-sed] for calculating
microdosimetric quantities (y & z) without
performing track structure simulation**

Phase-space file converter (PSFC)
Automatically convert PS source informationcompiled by IAEA to PHITS source format for
simulating medical accelerator beams

Confidential
information

Sourcesurface

Simulation using PSFC

*Furuta et al. Phys. Med. Biol. 62, 4798 (2017) **Sato et al. Radiat. Prot. Dosim. 122, 41 (2006) 24

RT-PHITS (RadioTherapy package based on PHITS)
 Convert DICOM image (CT, PET, SPECT) and plan data to PHITS input
 Convert dose distribution calculated by PHITS to DICOM RT-Dose data
DICOM image & plan data

DICOM SoftwareROIDVHCT

PET/SPECT

RT-doseRT-plan

RT-PHITS (CT2PHITS, PET2PHITS, Plan2PHITS, PHITS2DICOM etc.)
PHITS input file

Voxel phantom

 RI-source with xyz
 Phase space file[source] section

PHITS output file
PHITS

phits/utility/RT-phits

Dose distribution
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Applications to Particle Therapy
1.5
Relative dose

RBE−weighted dose
Absorbed dose

10.5

Proton00

drawn byPHITS+SimpleGEO

51015
2
Depth in water phantom (g/cm )K. Takada et al. JRR 59, 91-99 (2018)
O. Ploc et al. IEEE Aerospace Conf. (2017)8Dose (Gy)RBE−weighted dose
6Absorbed
dose

4200Carbon
510152Depth in water phantom (g/cm )S. Yonai et al. Med Phys. 39, 5028-39 (2012)

T. Sato et al. Radiat. Res. 171, 107-117 (2009)

Secondary dose estimation

RBE-weighted dose estimation
26

Applications to BNCT
Treatment Planning System

BPA incytoplasm

BSH onmembrane

nucleusnucleuscytoplasm

cytoplasm

Dose analysis in cellular scale

Kumada et al. Appl. Radiat. Iso. 166, 109222 (2020)

Biological effectivenessTsukuba PlanExpCalBPA 250 ppm
BSH 125 ppm
no compound

42001020Absorbed dose (Gy)

NeuCureTM by S.H.I.

Estimation of therapeutic effectApproved by PMDA：30200BZX00083000

T. Sato et al. Sci. Rep. 8, 988 (2018)27

Applications to Nuclear Medicine
PHITS-based Application forRadionuclide Dosimetry In Meshes

Small target dosimetry
109

10μm-diameter cell

108
107
106

90Y

177Lu

212Pb

105
104
101

1cm-diameter tumor metastasis

10010-110-290Y

 Developed by MSKCC andopened to public for free Automatically generate PHITS
input file based on mesh phantoms
by supplying the concentration ofRI in each organ
https://www.paradim-dose.org/
Carter et al. J. Nucl. Med 60, 1802 (2019)

177Lu

212Pb

10-3

Dose distributions around 10-μm
cell and 1-cm tumor metastasis
 Doses are highly heterogeneousin microscopic scales in the caseof α or low-energy β emitters
 PHITS was used in calculating
S-values for cellular and tumormetastasis scale targets
Lee et al. Radiat. Res. 190, 236 (2018)28

Applications to Diagnostics
A Web-based CT dose calculator: WAZA-ARI
Calculated organ doseShooting range

Select type of CTmachine and phantom

Interface of WAZA-ARIExample of PHITS simulation
X-ray spectra of various CT machines are precisely reproduced andirradiated to Japanese voxel phantoms with different anatomies in PHITSApproximately 2,000 facilities have been used for calculating CT-patient doses
F. Takahashi et al. Health Phys. 109, 104 (2015), https://waza-ari.nirs.qst.go.jp/

29Applications to Radiological Protection
Dose conversion coefficient

Atomic-bomb survivor dose

10.0%
5.0%

-15.0%

UterusThyroid

Testes

StomachPancreas

Ovaries

Lungs

LiverColon

BreastBrain

Eye lens-10.0%

Urinary bladder-5.0%

Bone marrow

0.0%
Skeleton

ICRP
Publication
116, 123, 146

15.0%

Organ mean

ICRP reference phantoms（Dthis study / Dcurrent system）ー 1

20.0%

J45 series phantom-20.0%
Differences
between new & old systems

Used in evaluation by ICRP

To be used in epidemiological study

T. Sato et al. Phys. Med. Biol. 54, 1997 (2009)
D. Satoh et al. JNST 53, 69-81 (2015)

C. Paulbeck et al. Radiat. Res. 192, 538 (2019)
T. Sato et al. Radiat. Res. 194, 390 (2020) 30

Applications to DNA-damage EstimationTrack structure of 5 MeV/n C ion

RBE estimation of DSB yields

60 nm

NeutronIonization

Spatial pattern of ionization & excitation
Special user-defined tally Cluster of the events within 10
base pair of DNA to identify DSB
and cluster damage

Baiocco et al., Sci Rep 6, 34033 (2016)

X-ray

 Output the data in Standard DNA
Damage (SSD) format
Matsuya J. App. Phys. 126, 124701 (2019)

Nakano et al., BJR Open, 3, 1 (2021)
31

Table of Contents
1. General Features of PHITS
2. Physics Models
3. Applications of PHITS
3.1 Design of radiation facilities
3.2 Radiation Therapy & Protection
3.3 Space Research
3.4 Other Applications

4. Summary32

Useful Functions for Space Research
Comic-ray source mode
Applicable particle types
 Galactic cosmic ray (GCR) in space GCR in the atmosphere including
secondary particles
 Solar energetic particle (SEP) inspace for 5 historically large events
Input parameters
 Time (Year/Month/Day)
 location (latitude, longitude, altitude) Energy and angular ranges

Cosmic-ray fluxes at groundlevel in New York

Dose equivalent estimator Conversion coefficients for dose equivalent for adult male & female is implemented
 Direct calculation of dose equivalent by weighting Q(L) on dose is feasible
33

Astronaut Dose Estimation

Virtual Kibo Module

Dose (mGy/day)■Exp.
▼Cal. (Total)●Cal. (T.P)▲Cal. (GCR)

Position (mm)

MATROSHKA ProjectMeasure doses inside a humanphantom mounted on ISS

PHITS simulation results
Used in the verification ofexperimental results

L.Sihver et al. Radiat. Environ. Biophys. 49, 351 (2010); M.Puchalska et al., Adv. Space Res. (2012)34

Cosmic-ray fluxes in the AtmospherePurposes
 Estimate of the effects of cosmic-ray
exposure on human, devices, and the Earth
Altitude [km]

 Design of cosmogenic nuclide dating andmuon radiography

PHITS Simulation and Modelling Airshower simulation for various conditions
 The results were modeled to instantaneously
predict the cosmic-ray fluxes anytime andanywhere in the atmosphere

Outcomes
 PARMA: Implemented in PHITS as thegenerator of cosmic-ray source mode

Airshower simulation

 EXPACS: EXCEL version of PARMA
https://phits.jaea.go.jp/expacs

Used in various research fields including geosciences (e.g. cosmoclimatology)
T.Sato, PLOS ONE 10, e0144679 (2015); T.Sato, PLOS ONE 11, e0160390 (2016)

35

Estimate of Solar Flare Impact
Development of WASAVIES
WArning System for AVIation Exposure
to Solar energetic particles
 Determine cosmic-ray dose rates atflight altitudes during large solar flare

Impact of solar flare onplanetary habiltability
Inhabitable?

 PHITS was used for analyzing theairshower induced by solar particles

Radiation dose rate map at flight altitude
during solar flare on Jan. 2005
T. Sato et al. Space Weather 16, 924 (2018)https://wasavies.nict.go.jp/index_e.html

Maximum radiation doses in theexoplanetary atmosphere
YA Yamashiki et al. ApJ 881, 114 (2019) 36

Table of Contents
1. General Features of PHITS
2. Physics Models
3. Applications of PHITS
3.1 Design of radiation facilities
3.2 Radiation Therapy & Protection
3.3 Space Research
3.4 Other Applications

4. Summary37

Useful Functions for Detector DesignDetector resolution
 Gaussian distribution
with Fano factor
expwithSCINFUL-QMD* mode
 Widely-used response calculation
code for organic scintillators
 High precision n(C,x) database Conversion table from depositionenergy to light output

 User original function

Response function for complicatedgeometry and source definitions

Response of CdZnTe calculated withconsideration of the asymmetry effectResponse of a liquid organic scintillator
irradiated with 65 MeV neutron

Meleshenkovskii et al. NIM B467, 108 (2020)*Satoh et al. JAEA-Data/Code (2006)38

Applications to Detector Design
Microdosimetric d(z) Model

Ion beam imaging system

 Universally determine detector
responses for different radiation
qualities based on z instead of LET

 Precise estimation of SEB spectra isthe key issue

 Microdosimetric function in PHITS
plays an indispensable role

Surface

1.2
LiF:Mg,Ti
thermoluminescent detectors

Relative efficiency

10.8
0.6
0.4
0.2

Range

ion
model experiments
1H4
He
12C
16
O
20
Ne
28
Si
40
Ar
56
Fe
84
Kr
132
Xe

010-1

100101 δ-ray production and activation
calculation functions in PHITS play
important roles

Ion beam
Phantom

SecondaryElectronBremsstrahlung
(SEB)
102

103

104

Unrestricted LETF in water [keV/µm]

Response of TLD (LiF:Mg,Ti) forvarious ions as a function of LET
Parisi et al. Radiat. Meas. 123, 1 (2018)

PinholeX-raycameras

Schematic view of the imaging system
Yamaguchi et al. PMB 63, 045016 (2018) 39

Application to Material Science
Tally for scoring DPA
 DPA: Average number of Displaced atoms Per Atom of a material→ Index of radiation damage
 DPA tally in PHITS can score not only conventional index (NRT-DPA) but also
newly proposed index (arc-DPA), considering defect production efficiency

800 MeV proton
irradiation on W
Conventional DPA：NRT-DPA(w/o defect productionefficiency)arc-DPA
20

Examples of defect production efficiencies

DPA depth distribution in tungsten

Y. Iwamoto et al., Journal of Nuclear Materials, 538, 152261 (2020)

40

Application to Device Engineering
Estimate of soft error rate (SER) of semiconductor
 The information stored in semiconductor memory is flipped by incident
radiations through the energy deposition process Cosmic ray neutron is the dominant contributor to SER at ground level
Event generator and cosmic-ray source modes are indispensable
Investigation of shielding effectDevice simulator

5FMSV model
STI (SiO2)
Reg. A (Si)Reg. B (Si)32
FIT/MBit

PHITS-based SER estimators

1FCalculated SER in a concrete building

4.0

 Neutron-induced SER is dramaticallyreduced by concrete shielding

Accurate!

Fast!

Abe et al. J. Nucl. Sci. Technol. 53, 451 (2015)

 Muon contribution to total SER is not
negligible (up to 10% at 1st floor)
Abe et al. RADECS (2016)41

Applications to Severe Nuclear Accident
Decontamination
 JAEA developed software toevaluate decontamination
effect (CDE) PHITS was used to makedatabase of ambient doses incontaminated environment

Decommissioning of NPP Estimation of radiation dose distribution
inside NPP is indispensable.
 PHITS was used to predict mostprobable dose rates by fully reproducing
its geometry estimated based on theinternal investigation results

Decontaminated zone

Ambient dose estimated by CDE

Predicted dose rates inside Fukushima
Daiichi NPP at the end of 2021

http://nsed.jaea.go.jp/josen/

Okumura et al. JAEA-Conf 2018-001

42

Table of Contents
1. General Features of PHITS
2. Physics Models
3. Applications of PHITS
3.1 Design of radiation facilities
3.2 Radiation Therapy & Protection
3.3 Space Research
3.4 Other Applications

4. Summary43

Important Features of PHITS Capability of transporting nearly all particles
Over a wide energy range in any materials

 User-friendly interface and graphical output tools
ANGEL, PHIG-3D etc.

 Sophisticated reaction models and libraries
JQMD, JENDL with event generator mode, track structure mode etc.

 Useful functions and tools for various purposes
RI & cosmic-ray sources, RT-PHITS, microdosimetric function etc.

 PHITS has been used in more than 50 countries
 Number of registered users increases ~ 1,000 per year
https://phits.jaea.go.jp/usermap/PHITS_map_userbase.html
44

More Information
Official Website
 Major update & tutorial announcements
 Confidential questions and bug reports to PHITS office
http://phits.jaea.go.jp/Facebook

Press “like”
More frequently updated. Announcement of bug & tips
https://www.facebook.com/phitscommunity

User Forum

Recommended!
User communication site. Question & answer
https://meteor.nucl.kyushu-u.ac.jp/phitsforum/

YoutubePromotional video. Tutorial contents (in future)https://www.youtube.com/watch?v=G6-XTIctRgA
45