Programme stuck in superposed field maps

[shliu]

Dear Didier,

TraceWin got stuck in superposed field maps. I have attached the project file.

tst4field.rar

(114.99 MiB) Downloaded 307 times

I tried to run separate fields and it works, so I'm wondering if it's the problem of the input beam distribution.

Could you please help me to check it?

OS: Win11
Version: 2.33.4.2

Kinds,
shliu

[Didier]

Dear Shilu,

For the moment, I haven't found out why the code got stuck, but clearly it's linked to your initial distribution. Energy dispersion is the cause of the problem. Some particles can't get through the simulation planes because their energy is probably too close to 0.
I'm still looking and I'll let you know if I find anything.

Regards,

Didier

[shliu]

Dear Didier,

Thanks for the reply!

It works well if there's only one field map in the lattice:

DRIFT 0 250 0 0 0
FIELD_MAP 70 1600 0 250 325.509 0 0 0 Solb 0

or

DRIFT 0 250 0 0 0
FIELD_MAP 70 2635 0 250 -0.255442 0 0 0 Dipb 0

In the superposed field maps, the second field begins from 450 mm, but it stucks at 269 mm, which means that it doesn't reach the edge of the second field map.

I also tried beam initial distribution with narrow energy spread(εz/10 and βz*10) and it works.

I'm sure it is the problem with the low-energy particles in the input distribution, but the reason why it just stucks before the second field map is still unknown.

BTW, the "low-energy" particles are still at about 0.9 MeV, which is not so "low", when compared with the beam coming out from the iron source.

Kinds,
shliu

[shliu]

Dear Didier,

How's it going about the stuck?

Kinds,
shliu

[Didier]

Dear Shliu,

I haven't forgotten you, but for the moment the person in charge of this specific development is not here, but I'm keeping this problem open.

Regards,

Didier

[shliu]

Dear Didier,

How about it now?

Kinds,
shliu

[Didier]

Dear Shliu,

Sorry, I'd honestly forgotten about your post.
Well, we spent hours on it yesterday and so far we haven't managed to figure out why the transport is blocking. It's incomprehensible at the moment and unfortunately this part of the code is almost impossible to debug step by step like other parts that allow it.
What I can advise you to do for the moment to temporarily solve the problem, and it's not satisfactory at the moment, is to reduce the aperture of the first field map from 250 to 140 mm. That's fine, but we've yet to understand why.
I'm not giving up trying to understand, but this week I haven't got the time. Next week certainly.

Regards,

Didier

[shliu]

Dear Didier,

Thank you for your effort to solve the problem. I'll continue to follow it up and hope there would be a solution next week.

Kinds,
shliu

[Didier]

Dear Shliu,

Well, it was complicated, but I think we've solved the problem. Finally, I hope and I'm so sorry for the long wait, but your case is a little exotic compared to the usual simulations.
So, first you need to upgrade your code, then in "Main" page -> "Simulation options" select "Losses in FIELD_MAP" option.

Regards,

Didier

[shliu]

Dear Didier,

Thank you for the upgration and it works now with the option "Losses in FIELD_MAP" checked.

I tried another input distribution (

dst_input_2.rar

(15.38 MiB) Downloaded 32 times

) with larger divergence and an error comes out saying that "Part of the beam distribution never reaches the end of the field map!"