MCNPX - Question in SDEF card about AXS and EXT

My code version is 2.7

I have a disk source of R=0.3 cm, 60 cm above in z axis. I want set limits for the x and y axis, but, I can only put one command "axs" and "ext". How can i define two limits with one command?

my code it is like this
SDEF pos=0 0 60 rad=d1 axs=1 0 0 ext=d2 PAR=2 ERG=0.018 VEC=0 0 1 DIR=-1
SI1 0 0.3
SP1 -21 1
SI2 -1 9
SP2 0 1

i want define x to -1 to 9, and y to 9 to 9.

Like this

Help me in the question, please.


for my part I will simplified with a rectagular parallel beam:
sdef par=P pos 0 0 -60 axs 0 0 1 ext 0 vec 0 0 1 dir 1 erg 1 &
X=d1 y=d2 Z=0
Si1 -1 9
sp1 0 1
Si2 -9 9
sp2 0 1
In YX plan it gives :



Hi, i'm using the same model as yours. do you know if there is any difference in results the cone model, for this?

very thanks.
The difference must be low because the angle is less than 10 deg and the Energy is very low (18 keV)

Want to reply to this thread?

"MCNPX - Question in SDEF card about AXS and EXT" You must log in or register to reply here.

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving