How to use TrackSrim


I am currently trying to replace TrackHeed with TrackSrim and have some questions regarding the SetTargetClusterSize() and SetClustersMaximum() functions and some details of TrackSrim. Based on the user guide, I understand that the two functions do the followings:

SetTargetClusterSize(n) sets, on average, n number of electrons to a cluster, and

SetClustersMaximum(n) sets, on average, n/2 number of clusters on the track.

Based on the user guide, it seems like one is only supposed to use either one of the above functions and not both at once. Is this correct?

Also, the two tracks produced by the two functions can be somewhat different with the SetTarget method being more continuous while the SetCluster can have gaps in between. So, which one is more of an accurate picture for simulating a track left behind by a charged particle?

Lastly, does TrackSrim take into account the gas pressure that is set by Magboltz? Or more importantly, does pressure affect the number of electron-ion pairs that get created? For TrackHeed, the delta electrons are part of the charged-particle track, but is this also true for TrackSrim?

the logic (which is indeed not well document) is the following:

  • If the target cluster size is set, then TrackSrim will try to calculate the step size between clusters such that will be calculated such that one gets on average the requested number of electrons in a cluster.
  • If there is no target cluster size set (but the max. number of cluster is set), then TrackSrim will indeed choose the step such that the number of clusters is on average half the maximum one.
  • If neither target cluster size nor max. number of clusters are set, TrackSrim will aim to produce on average 100 clusters on a track.

If the max. number of clusters is reached, then the track stops (also in the case that a target cluster size is set).

Not sure which method is more “realistic”, both are ok I guess. If you are looking for a more accurate modeling of track-by-track fluctuations you could also try the TrackTrim interface.

By default, TrackSrim takes the mass density of the from the SRIM input file. You can override it using the method SetDensity.


Thank you for the clarification. In general, will TrackHeed and TrackSrim produce approximately the same amount of initial electron-ion pairs? After setting the density to match that of TrackHeed (I used the temp and pressure that I gave to magboltz to calculate the density using the ideal gas law), I found that TrackSrim produces about the same amount of electron-ion pairs. The only difference is that TrackSrim’s track is not a straight line whereas TrackHeed’s is.

Also, does TrackSrim take delta electrons into consideration? (i.e. can I turn on or off the delta electron for TrackSrim?)

No, I wouldn’t say that. TrackHeed and TrackSrim have complementary use cases. The model used by Heed is applicable for fast charged particles (“mips”) while SRIM is typically used for heavily-ionising particles (like alphas) that slow down in the gas. Now you can probably use SRIM also to compute the stopping power and straggling of a “mip”, and in this case I would expect the results to be consistent with what you get from Heed. It doesn’t work the other way though, Heed will not give reliable results for slow/low-energy projectiles.

No, delta electrons are not simulated explicitly by TrackSrim.

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