Some questions for molfow particles in setting

General discussion
1

I am a new learner for Molflow, below are some questions:

  1. in one tutorial, Particles in for steel stainless is cosine and outg/area 1e-12 mbar*L/s/cm2， why use cosine?
  2. if I want to add Particles in for some CF 50 flanges, can I choose uniform and outgassing 1e-10 mbarL/s? I checked that the CF flanges leakage is about 1e-8 PaL/s.
  3. if I want to add Particles in for steel stainless bellows, can I set it similar with CF flanges or not? I didn’t find the data of bellows leakage.
2

Sorry Angel, I will need a bit more time to reply, I’ll get back to you.

3

Sorry for the late answer, many of the team are on holiday.

  1. Cosine is the default directional distribution in ultra high vacuum systems. See slides:
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    image1372×781 240 KB

From source: https://uspas.fnal.gov/materials/19NewMexico/Vacuum/USPAS%202019%20Vacuum%20Session%206_1%20System%20Engineering.pdf

For your further questions, are you sure you don’t mix the term “leakage” (unwanted behavior due to incorrect sealing) and “outgassing” (gas load coming from a surface)? If you refer to outgassing, usually we express it as surface-specific outgassing (for example in mbar.l/s/cm2).

This value you can apply directly in Molflow:
image
Note that I selected the second text field.

For bellows, it depends how you represent them in Molflow, if you model them as a simple circle, you have to increase their specific outgassing to take into account the unodeled surface (the bends).

4

Hi, Maarton,

Thanks a lot for your explanation.

Yes, I mixed the leakage with outgassing.

So for all of tube, CF flange and bellows, I should choose “cosine” and “outg/area（mbar*l/s/cm2）”: 1e-12 for tube, 1e-8 for flange and bellows. I drew some inner waves for bellow.
image

A more question: for one surface, I need a pump speed, such as 100L/s, can I remain its outgasing data? or delete it?
image

if there are some reports for different materials outgassing data, such as copper, ceramic or steel with high temp?

thanks again.
Angel

5

Yes, you can use sticking and outgassing at the same time: facets will create particles and if they come back to the facet at a later time, they will stick.

I can’t help with reports about material outgassing - as it depends on many parameters (cleaning, surface history etc.) literature research is required.

6

Thanks a lot. I will try some models.