Different result of USRBIN and USRBDX

Dear experts,
I simulated a cylinder composed of mixed powders of lithium fluoride and zinc sulfide. The maximum photon flux density obtained by USRBIN statistics is about 25um(bin=1um), but when using USRBDX statistics, I found that the maximum number of photons obtained exceeds 200um. May I know what is the reason?

I know that they count spatial distribution and given surface respectively, but why are their trends different?

Dear @xiongbp,

Could you please clarify your question? Definitely, the number of photons isn’t measured in unit of length.

Also, I would recommend you to search in the forum for comparisons between USRBIN and USRBDX. There are already several threads on this subject.

Dear @amario ,
Here is my file.
mixtureH.flair (3.2 KB)
A cylinder composed of mixed powders of 6LiF and ZnS, I want to know at which thickness will the model give maximum photon fluence at exit surface, so I use USRBIN and USRBDX, the maximum thickness is about 20um with USRBIN, but exceed at 400um with USRBDX, I want to know the reason.

Dear Xiong,

I understand you want to find the thickness for which the number of optical photons traversing from the mixture to the BLANK region is maximized?

The USRBDX scorer would suffice. For your purpose, you should score the one-way current rather than the fluence like you do in your input (the scoring “type” should contain “I1”). After processing the cycles, the total number of photons is found in the sum.lis file.

The USRBIN card would not be suitable for your purpose as it scores the density of tracks. Hence, optical photons bouncing off the material surface could cross the same bin multiple times. As I understand it’s not directly what you aim to measure.

Dear @blefebvre
I am sorry for late,
Yes, that is my will, but using USRBDX can only get the number of photons passing through the interface under a specific length at a time, how can we get the number of photons passing through the interface under different lengths at the same time(At an interface, a curve of the number of photons varying with the thickness of the material)?

Dear Xiong,

I understand you want to obtain a map of the photon current density at the interface?

Or maybe a map of the photon current density at different positions z in the mixture?

Dear @blefebvre ,
Maybe I did not express my question clearly, please see the picture,


The “(2)” is what I want to get, if “x” is long enough, should I use USRBDX many times (for different value of “x”)?

Is x the physical length of the cylinder “mixture” or simply the position for scoring?

If the variable x corresponds to the length of the cylinder, you must run multiple independent simulations each with a different value of x. For each of those simulations, you score the total number of outcoming photons using USRBDX. Then, using your own plotting software, you plot the number of photons as a function of x (one point per simulation).

Dear @blefebvre ,
The “x” is the length of the cylinde, a variable, I have a question here.
If I use USRBIN, the thickness corresponding to the maximum photon flux is about 25um, but 300um by USRBDX , so I guess whether it is the photon flux obtained by USRBIN at a specific thickness is just generated here, not include the transmission from other thicknesses?

Dear @xiongbp,

The scorers USRBIN and USRBDX provide different information on the simulation. The first provides a map of the track density as a function of position, the latter the energy distribution of particles traversing an interface between two regions.

USRBIN will provide the track density of optical photons exiting the cylinder when looking a bins located outside of the cylinder.

Dear @blefebvre ,
I am sorry for late.
I have understand the difference between the two and thank you for your patience.