Submitted by Chao LI on
Body

 

Hi Marton,

 

Page 191 in

 

Ref: Lucas, C. B. (2013). Atomic and molecular beams: production and collimation. CRC press.

 

At the end of section 8.3.4, it seems that Monte Carlo simulations are unfavorable under certain circumstances because of its statistical error, while alternative analytical solutions exist.

 

My question appears to be quite general, because I couldn't be specific due to less of expertise in numerical calculations and the machinery behind Molflow+.  

 

Any comments for that section?

 

Thanks,

 

Chao

Submitted by Marton Ady 4 years ago

Hello Chao,

Unfortuantely I don't have the book you referenced, so I can't have a look.

All simulation methods have pros and cons. Monte Carlo simulations can have high statistical errors, especially if several orders of magnitude need to be modeled, although there are mitigation techniques (series of simulations at each pressure drop, see section 1.2.4.3 and Fig. 1.35 of my thesis).

Analytic methods provide exact results, in exchange apart from simple geometries (tubes) they are very hard to apply for real-life structures.

In CERN we use both, even at the same time (conductance calculation of parts by Monte Carlo then analytic solution by electric circuit solvers)