[mcstas-users] McStas simulation of nested elliptical optic with many levels crashes

[Richard Wagner]

Dear all,

we had in the meantime a detailed look in the matter from our side and 
suspect know a problem with the OFF-file

If we use a mono planar version of the optic (see example in the 
attachment) we can increase the nested levels ad lib.
We are only limited by the fact that the spacing between the levels is 
becoming so small, that it makes no sense to continue.

A major difference between the single and double planar optic is that 
the double planar OFF-File has surfaces that intersect each other.

I don't know if this is "allowed" or if it can cause McStas to have 
problems during the simulation.
Until a certain level of complexity it worked fine.

What we are currently doing is to change the function (written in 
python), that generates the double planar OFF-file to generate 
additional vertexes and faces at the intersection of the surfaces. So we 
end up having a cleanly defined optic with no 'undefined intersections'.

I will report the outcome of this changes.

Best,

Richard




On 02/07/2021 09:35, Erik B Knudsen wrote:
> Dear Richard,
> Thank you for the thorough and detailed report. We will take a look at 
> your problem asap and report back.
> cheers
> Erik
>
> On 29/06/2021 18:31, Richard Wagner wrote:
>> Dear McStas experts,
>>
>> We are currently doing simulations with nested elliptical optics and 
>> so far things ran quiet smoothly.
>>
>> We generate the OFF file for the optic ourselves and use the 
>> Guide_anyshape component.
>>
>> We start with an outer layer and continue to add inner layers one at 
>> a time.
>> If we then get to optical components that have a high number of 
>> levels we run into the problem, that McStas crashes resp. aborts the 
>> simulation.
>>
>> Output in that case reads:
>>
>> # McStas 2.7 - Nov. 27, 2020: [pid 64818] Signal 11 detected SIGSEGV 
>> (Mem Error)
>> # Simulation: NNb (NNb.instr)
>> # Breakpoint: psd_monitor (Trace) 2.46 % (   24574.0/ 1000000.0)
>> # Date:      Tue Jun 29 17:44:13 2021
>> # Started:   Tue Jun 29 17:44:13 2021
>> # Last I/O Error: No such file or directory
>> # McStas 2.7 - Nov. 27, 2020: Simulation stop (abort).
>>
>> Or
>>
>> # McStas 2.7 - Nov. 27, 2020: [pid 66573] Signal 10 detected [proc 0] 
>> SIGBUS (Bus error)
>> # Simulation: NNb (NNb.instr)
>> # Breakpoint: nested (Trace) 85.56 % (  855555.0/ 1000000.0)
>> # Date:      Tue Jun 29 18:00:32 2021
>> # Started:   Tue Jun 29 18:00:28 2021
>> # Last I/O Error: No such file or directory
>>
>> There are many messages such as the following in the Mcstas Window, too:
>>
>> Guide_anyshape: nested: Warning: Reflectivity R=7.02318 > 1 lowered 
>> to R=1.
>> Guide_anyshape: nested: Warning: Reflectivity R=7.02365 > 1 lowered 
>> to R=1.
>> Guide_anyshape: nested: Warning: Reflectivity R=7.02412 > 1 lowered 
>> to R=1.
>> Guide_anyshape: nested: Warning: Reflectivity R=7.0246 > 1 lowered to 
>> R=1.
>>
>> I put an example of an instrument file (+OFF , +Source Component) of 
>> a failed run for a 1m optic in the attachment.
>>
>> The trace run for instrument visualization works.
>> We only run into the problem for short optics <=2 m, were a high 
>> number of nested levels is needed to completely cover the cross section.
>>
>> We run into the problem on Ubuntu 18.04 and MacOs Big Sur machines.
>>
>> Any ideas what's the problem? Are the spacing of the elliptical 
>> getting to narrow, perhaps?
>>
>> Thanks in advance,
>>
>> Richard
>>
>>
>> -- 
>> *Richard Wagner*
>> Research Engineer
>> Nuclear and Particle Physics Group
>> Institut Laue-Langevin - ILL
>> 71, avenue des Martyrs
>> CS 20156
>> 38042 Grenoble Cedex 9
>> France
>>
>> www.ill.eu <www.ill.eu>
>>
>>
>>
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>> mcstas-users at mcstas.org
>> https://mailman2.mcstas.org/mailman/listinfo/mcstas-users
>>
>
-- 
*Richard Wagner*
Research Engineer
Nuclear and Particle Physics Group
Institut Laue-Langevin - ILL
71, avenue des Martyrs
CS 20156
38042 Grenoble Cedex 9
France

www.ill.eu <www.ill.eu>


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