1. Setting of various source Part II
PHITS
Multi-Purpose Particle and Heavy Ion Transport code System
Setting of various source
Part II
PHITS講習会　入門実習
Sep revised
Title 1

2. Goal of this lecture Transport simulation using dump data as sources
Simulation of radiation shielding using dump data, which were information on particles from a 60Co source and were recorded at z=20cm.
Purpose 2

3. sourceB.inp Basic setup Geometry Projectile: Geometry: Tally:
1.173 and 1.333MeV photons (from 60Co)
Water cylinder (10cm radius and 20cm thickness)
[t-track] fluence distribution
[t-cross] photon energy spectrum coming into water
Water
60Co
Geometry
track_xz.eps
cross_eng.eps
Check Input File 3

4. Table of contents Source with dump data Summary Making dump data file
Transport simulation using dump data
Summary
PHITS講習会　入門実習
Table of Contents 4

5. Source with dump data
PHITS can perform two-step calculation using information on particles coming into specified regions.
For example,
to study shielding effect changing thickness of lead block.
In the 1st step,
information on photons coming into the lead is recorded.
Sources in the 2nd step.
You can perform calculations of the 2nd step many times changing the thickness of the lead block.
60Co
Water
Lead
Dump data 5

6. How to use
In the [t-cross], [t-product], or [t-time] tally, set dump parameters.
Execute PHITS calculation of the 1st step.
A data file named as ******_dmp.out is made (****** is specified by “file=“). This file contains information on the tallied particles.
In the [source] section, set s-type=17 with dump parameters.
The old [source] section and old tally, which were used in the 1st step, should be invalid by “off”.
Execute PHITS calculation of the 2nd step.
[source] section with dump parameters (2nd step)
dump parameters (1st step)
[ T - C r o s s ]
・ ・ ・ ・ ・ ・
file = ******.out
dump = -11
[ S o u r c e ]
s-type = 17
file = ******_dmp.out
dump = -11
same format
The number of the data item.
(If positive, the data file is made as binary. If negative, the file is made as ASCII data.)
Dump data 6

7. ID number of dump data Dump data 7
Using dump parameters, you can set the data item and their order to output in the dump data file.
dump = -11
You can change this order ID
physical quantities 1
kf: kind of particle 11
c1: value of counter 1 2
x: x-coordinate 12
c2: value of counter 2 3
y: y-coordinate 13
c3: value of counter 3 4
z: z-coordinate 14
sx: x-component of spin 5
u: x-component of velocity 15
sy: y-component of spin 6
v: y-component of velocity 16
sz: z-component of spin 7
w: z-component of velocity 17
name: collision number 8
e: energy 18
nocas: history number 9
wt: weight 19
nobch: batch number 10
time: time 20
no: cascade ID
Dump data 7

8. Two modes to use dump data
idmpmode=1: Consider correlations between particle in 1st step (New*)
nocas & nobch info are required (default if they exist)
Recommended
*From PHITS2.80
idmpmode=0: Assume independence of initial particle in 2nd step (Old)
Automatically selected if nocas or nobch does not exist
Should be use only when many particles are produced and particle correlation can be ignored in 1st step (e.g. x-ray generation by bombarding electrons on target)
Other cautions to use dump data
(1st step) set the dump region as void in order to avoid a double-count of particles passing through the region.
(1st step) tally the energy spectrum of the dump data and check whether the data are statistically sufficient to be used as source.
(2nd step) The result of the 1st step is not included in the 2nd step. If you want total, you have to use “sum tally” to add 1st & 2nd step results.
Dump data 8

9. Exercise 1
To record information on particles passing through the water as dump data, set outer void behind the water (positive side of z-axis).
Set a cylindrical region (cell number is 102) with 10cm radius and 5cm thickness as outer void behind the water (positive side of z-axis).
In the [cell] section, outer void is defined by setting its material number = -1 (density is not needed).
Check the geometry by setting icntl=8.
Dump region
(defined as outer void)
Dump data 9

10. Answer 1
To record information on particles passing through the water as dump data, set outer void behind the water (positive side of z-axis).
SourceB.inp
The white region denotes the outer void.
[ Parameters ]
icntl = 8
・・・ ・・・ ・・・ ・・・
[ S u r f a c e ]
10 so
11 cz
12 pz
13 pz
14 pz
[ C e l l ]
#101 #102
track_xz.eps
Dump data 10

11. Exercise 2
Record information on photons from the 60Co source, passing through the water as dump data.
By copying the [t-cross] section, make the 2nd [t-cross] section. (The 1st one is used to make dump data, and the 2nd one is used to check the energy spectrum of the dump data.)
Add dump parameters (from 1 to 9, 18, and 19) to the 1st [t-cross].
In the 1st [t-cross], change cell numbers so that this tally counts the number of photons moving from cell 101 to 102. Furthermore, set “file= cross_photon.out” and “epsout=0”
In the 2nd [t-cross], add one condition to count the number of photons moving from cell 101 to 102 (set its area to be p102).
Execute PHITS with icntl=0 in [parameters].
Dump region
(cell 102)
Water
(cell 101)
Record photons moving from 101 to 102.
Dump data 11

12. Answer 2
Record information on photons from the 60Co source, passing through the water as dump data.
SourceB.inp
[ T - C r o s s ]
・ ・ ・ ・ ・ ・
ne =
unit = 1
axis = eng
file = cross_photon.out
output = flux
part = photon
epsout = 0
dump = -11
reg = 2
non r-from r-to area
[ Parameters ]
icntl = 0
・・・ ・・・ ・・・ ・・・
cross_eng.eps (2nd page)
The data are not enough to be used as sources, because this result should be continuum spectrum.
Dump data 12

13. Exercise 3 Make large dump data can be used as source. Dump data 13
Increase “maxcas” to obtain large data.
Result with maxcas=1000
Result with maxcas=10000
cross_eng.eps(2nd page)
not enough
Dump data 13

14. Answer 3 Make large dump data can be used as source. Dump data 14
Result with maxcas=100000
cross_eng.eps(2nd page)
The result becomes continuum spectrum. This can be used as source.
(Note that the relative errors are %)
Dump data 14

15. Table of contents Source with dump data Summary Making dump data file
Transport simulation using dump data
Summary
PHITS講習会　入門実習
Table of Contents 15

16. Exercise 4 Perform the transport simulation using dump data. Dump data
Create the new [source] section with s-type=17. (Set the old [source] section to be invalid by “off”.)
Set cell 102 to be void (its material number is 0)
Set the [t-cross] section with dump parameters to be invalid by “off”.
[source] section with dump parameters (2nd step)
[ S o u r c e ]
s-type = 17
file = cross_photon_dmp.out
dump = -11
Both two files,
cross_photon_dmp.out and
cross_photon.out, are needed.*
*When the dump ID 18 and 19 are included in the dump data, “maxcas” and “maxbch” of the 1st step written in “cross_photon.out” are used. (“maxcas” and “maxbch” in the input file of the 2nd step are ignored.)
Dump data 16

17. Answer 4 Perform the transport simulation using dump data. Dump data
SourceB.inp
[ S o u r c e ] off
totfact = 2.0
・ ・ ・ ・ ・ ・
[ S o u r c e ]
s-type = 17
file = cross_photon_dmp.out
dump = -11
[ T - C r o s s ] off
・ ・ ・ ・ ・ ・
dump = -11
Particles included in dump data are generated behind the water.
[ C e l l ]
#101 #102
track_xz.eps
Dump data 17

18. Exercise 5 Put a lead block behind the water. Dump data 18
Change the material of cell 102 to lead with the isotope ratio (see the right table) and the density of 11.34g/cm3. (Change some parameters in [material] and [cell].)
In order to study an effect of the shielding, define a new cell 103 (a cylindrical region with 10cm radius and 1cm thickness).
In the 2nd [t-cross], add one condition to count the number of photons moving from cell 102 to 103 (set its area to be p102).
Element symbol of lead: Pb
1cm
cell 103 (void)
cell 101 (water)
cell 102 (lead)
Dump data 18

19. Answer 5 Put a lead block behind the water. Dump data 19 SourceB.inp
[ T - C r o s s ]
・ ・ ・ ・ ・ ・
reg = 3
non r-from r-to area
[ M a t e r i a l ]
mat[1] H 2 O 1
mat[2] Pb 1.0
[ S u r f a c e ]
・ ・ ・ ・ ・ ・
13 pz
14 pz
15 pz
[ C e l l ]
#101 #102 #103
The particle fluence is reduced in the lead region.
track_xz.eps
Dump data 19

20. Answer 5 Put a lead block behind the water. Dump data 20
Energy spectrum of photons coming into the lead region
cross_eng.eps(3rd page)
The lead block reduces the strength of and 1.333MeV photons to 1/10.
(Investigate the thickness of the lead so that the strength becomes 1/100.)
Dump data 20

21. Table of contents Source with dump data Summary Making dump data file
Transport simulation using dump data
Summary
PHITS講習会　入門実習
Table of Contents 21

22. Summary Summary 22 We can perform two step simulation using dump data.
A correct statistical process using “idmpmode=1” can be applied by recording dump ID 18 and 19. (From PHITS2.80)
Notes about idmpmode=1
“totfact” is compulsory reflected the setting of “totfact” in the 1st step (at the time of making dump data) in the calculation of the 2nd step using dump data.
The option “idmpmode=1” is incompatible with multi-source. (Use sumtally option)
In the 2nd step, “istdev<0” (restart calculation) or “dumpall=1” in [parameters] cannot be used.
If you use the old statistical process of PHITS, set “idmpmode=0”.
With idmpmode=1, the option “dmpmulti” controls the number of re-use of the dump file. (dmpmulti=2.0 is 2 times)
《休憩はさむ》
まとめ
Acknowledgement
The option “idmpmode=1” and re-used calculation using the option “dmpmulti” were introduced by referring to the presentation “Estimation of uncertainty in multi-step Monte Carlo calculation”(N50) by Dr. Y. Namito et al. at the 2015 annual meeting of AESJ (Hitachi, Japan).
Summary 22