Issue with Particle Emission in SPRRZnrc Using IAEA Phase Space Files

[yamane89]

Hello,
I conducted a simulation of stopping-power ratio (SPR) using SPRRZnrc with the Varian_9MeV phase space file downloaded from IAEA. However, the results differed significantly from the SPR calculated manually. Upon investigation, I found that when using an IAEA-format phase space file as the source in SPRRZnrc, even if the particle type is set to "all," only photons are being emitted.

To verify this, I used Beamnrc with the same settings and generated two types of phase space files: one in egsphsp1 format and the other in IAEA format (IAEAphsp). Then, I performed the same calculations using SPRRZnrc with these two phase space files.
To use EGS_window, I set IWATCH to "graph" and set the source particle type to "all."
(Since setting IWATCH to "graph" in SPRRZnrc does not generate a .egsgeom file, I created my own .egsgeom file.)

The images are as follows:
① IAEAphsp
② IAEAphsp with photons hidden in EGS_window
③ egsphsp1
④ egsphsp1 with photons hidden in EGS_window

Color representation in the images:

Yellow: Photons
Blue: Electrons
Red: Positrons
The beam is incident from right to left.

Do you have any solutions for this issue?

Additionally, I have encountered frequent errors when using IAEA-format phase space files.
Is there a way to convert an IAEA-format phase space file to egsphsp1 format?

Thank you!

Operating system

• [*] Linux
• Windows
• macOS
• Other:

EGSnrc version
2025ver

[rtownson]

The first place to check is in the .IAEAheader file. Are there any electrons saved in the file, and they're just not being read? There should be a section in the header that tells you how many particles of each type there are.

Take a look in the output from the SPRRZnrc simulation, and see if you can find where it prints out information about the phase-space. Does it say that it's reading all types of particles from the file (I don't recall off hand if it prints this, you can copy/paste the output here if you like).

[yamane89]

Thank you very much.
Below is the IAEA header file. The phase space file I used is the Varian_9MeV_10*10 provided by the IAEA.
https://www-nds.iaea.org/phsp/electron1/

---

$IAEA_INDEX:
603 // IAEA website: www-nds.iaea.org/phsp/electron/

$TITLE:
Varian Clinac 2100CD, 9MeV, 10x10

$FILE_TYPE:
0

$CHECKSUM:
2147483647

$RECORD_CONTENTS:
1 // X is stored ?
1 // Y is stored ?
1 // Z is stored ?
1 // U is stored ?
1 // V is stored ?
1 // W is stored ?
1 // Weight is stored ?
0 // Extra floats stored ?
2 // Extra longs stored ?
1 // Incremental history number stored in the extralong array [ 0]
3 // ILB PENELOPE variable stored in the extralong array [ 1]

$RECORD_CONSTANT:

$RECORD_LENGTH:
37

$BYTE_ORDER:
1234

$ORIG_HISTORIES:
415667127

$PARTICLES:
56197810

$PHOTONS:
24189154

$ELECTRONS:
31999608

$POSITRONS:
9048

$TRANSPORT_PARAMETERS:
C1 = C2 = 0.1
WCC = 100 keV and WCR = 20 keV

$MACHINE_TYPE:
VARIAN CLINAC 2100 C/D

$MONTE_CARLO_CODE_VERSION:
PENELOPE 2008
penEasyLinac 2009-12-01
penEasy 2009-11-04

$GLOBAL_PHOTON_ENERGY_CUTOFF:
20 keV
$GLOBAL_PARTICLE_ENERGY_CUTOFF:
100 keV
$COORDINATE_SYSTEM_DESCRIPTION:
Cartesian right-handed
Origin: z = 0, upstream face of the target, x = y = 0 central position of the target
z axis parallel to beam direction, pointing downstream
y along the direction of movement of the upper jaws, pointing towards the accesory holder when seen from its aperture
x axis along the direction of movement of the lower jaws

// OPTIONAL INFORMATION

$BEAM_NAME:
9 MeV ELECTRON BEAM

$FIELD_SIZE:
10X10 cm2

$NOMINAL_SSD:
100 cm

$MC_INPUT_FILENAME:

$VARIANCE_REDUCTION_TECHNIQUES:
Movable skins applied to the primary collimator and the jaws
Rotational splitting applied on a plane located below the ionisation chamber and above the secondary collimator

$INITIAL_SOURCE_DESCRIPTION:
Electron point source at x = y = z = 0
Monodirectional beam vx = vy = 0, vz = 1
Monoenergetic, E = 10.21 MeV

$PUBLISHED_REFERENCE:
L Brualla, R Palanco-Zamora, A Wittig, J Sempau and W Sauerwein
Comparison between PENELOPE and electron Monte Carlo simulations of electron fields used in the treatment of the conjunctival lymphoma
Phys. Med. Biol. 54 (2009) 5469-5481.
PHSP available online at http://www-nds.iaea.org/phsp/, IAEA, Vienna

$AUTHORS:
L. Brualla, R. Palanco-Zamora, MA. Duch, J. Sempau

$INSTITUTION:
Universit�tsklinikum Essen (Germany), Karolinska University Hospital (Sweden), Universitat Politecnica de Catalunya (Spain)

$LINK_VALIDATION:
VarianClinac_2100CD-readme.PDF. Available online at http://www-nds.iaea.org/phsp/electron , IAEA, Vienna

$ADDITIONAL_NOTES:
This is IAEA header as defined in the technical
report IAEA(NDS)-0484, Vienna, 2006

$STATISTICAL_INFORMATION_PARTICLES:
// Weight Wmin Wmax Emin Emax Particle
2.41892E+07 1 1 1.091 0.02 10.19 PHOTONS
3.19996E+07 1 1 8.73 0.1 9.962 ELECTRONS
9048 1 1 2.071 0.1003 8.393 POSITRONS

$STATISTICAL_INFORMATION_GEOMETRY:
-4.90659 4.90659
-4.90659 4.90659
78.45 78.5

[yamane89]

The egslst file is quite long, so I will include only the source section.

---

---

                         SOURCE PARAMETERS

---

              Full phase space input for each incident particle. 
 Source data file: /home/yamane/Desktop/IAEAsource/Varian_Clinac_2100CD_9MeV_10x10
                    Source incident on plane        21.5500 cm from the point of rotation
                     Angle with respect to z-axis         0.0000 degrees.
                     z-position of point of rotation         0.0000
                     X offset of phsp (before rotation)        0.0000 cm
                     Y offset of phsp (before rotation)        0.0000 cm
                     # of particles read from ph-sp file =    1.000E+08.
           Total number of particles in file      :  56197810
           Total number of photons                :  24189154
           (the rest are electrons and positrons)

           Maximum kinetic energy of the particles:    10.190 MeV
           Minimum kinetic energy of the electrons:     0.000 MeV
           # particles incident when phase space created :  415667127.

Particles will be recycled 1 times before moving on to next one.

\f

                                                  Tue Feb 18 12:09:12 2025

[yamane89]

This is the input file used in the SPRRZnrc simulation.

---

TITLE= sprrznrc_template

##########################
:start I/O control:

IWATCH= off
STORE INITIAL RANDOM NUMBERS= no
IRESTART= first
STORE DATA ARRAYS= yes
SPR OUTPUT= slabs/cylinders
SPR IN CYLINDER IX= 1
SPR IN SLAB IZ= 0

:stop I/O control:
#########################

##########################
:start Monte Carlo inputs:

NUMBER OF HISTORIES= 100000000
INITIAL RANDOM NO. SEEDS= 1, 3
MAX CPU HOURS ALLOWED= 999
IFULL= dose and stoppers
STATISTICAL ACCURACY SOUGHT= 0.0000
PHOTON REGENERATION= no

:stop Monte Carlo inputs:
#########################

##########################
:start geometrical inputs:

METHOD OF INPUT= groups
Z OF FRONT FACE= -100
NSLAB= 1, 90, 1, 1
SLAB THICKNESS= 100, 0.1, 32, 59
RADII= 0.6, 16, 100
MEDIA= H2O521ICRU,
AIR521ICRU;

DESCRIPTION BY= planes
MEDNUM= 1, 2, 2, 2
START ZSLAB= 2, 1, 2, 93
STOP ZSLAB= 92, 1, 92, 93
START RING= 1, 1, 3, 1
STOP RING= 2, 3, 3, 3

:stop geometrical inputs:
#########################

##########################
:start source inputs:

INCIDENT PARTICLE= all
SOURCE NUMBER= 22
SOURCE OPTIONS= 0, 21.55, 0, 0, 0, 0, 0
FILSPC= /home/yamane/Desktop/IAEAsource/Varian_Clinac_2100CD_9MeV_10x10.IAEAphsp

:stop source inputs:
#########################

##########################
:start MC transport parameter:

Global ECUT= 0.521
Global PCUT= 0.01
Global SMAX= 1e10
ESTEPE= 0.25
XImax= 0.5
Skin depth for BCA= 3
Boundary crossing algorithm= EXACT
Electron-step algorithm= PRESTA-II
Spin effects= on
Brems angular sampling= KM
Brems cross sections= BH
Photon cross sections= si
Electron Impact Ionization= Off
Photon cross-sections output= off
Bound Compton scattering= Off
Pair angular sampling= Simple
Photoelectron angular sampling= On
Rayleigh scattering= Off
Atomic relaxations= On
Set PCUT= 0
Set PCUT start region= 1
Set PCUT stop region= 1
Set ECUT= 0
Set ECUT start region= 1
Set ECUT stop region= 1
Set SMAX= 0
Set SMAX start region= 1
Set SMAX stop region= 1

:stop MC transport parameter:
#########################

##########################
:start media definition:

:stop media definition:
#########################

##########################
:start variance reduction:

ELECTRON RANGE REJECTION= off
ESAVEIN= 0.0
RUSSIAN ROULETTE DEPTH= 0.0000
RUSSIAN ROULETTE FRACTION= 0.0000
EXPONENTIAL TRANSFORM C= 0.0000
PHOTON FORCING= off
START FORCING= 1
STOP FORCING AFTER= 1

:stop variance reduction:
#########################

[yamane89]

It seems that electrons might not be irradiated in this simulation.
Could you please let me know if you have any suggestions or solutions for this issue?

[rtownson]

Please give my fix #1256 a try and let me know if it solves the issue for you. Thanks for reporting this!

[yamane89]

Thank you very much for the fix!
I ran the simulation again, and the stopping-power ratio values seem to be generally reasonable.
I really appreciate it!