CERN Accelerating science

Hi, Marton, Thanks for the quick response. regards Suidong

This begs the question at what temperature is this outgassing rate happening. Is at the room temperature, maybe 0C (273.15K), or at the temperature of the facet? This will make a difference of the actually # of particles/sec coming off of the facet. Remeber PV = NkT, so in units of pressure x volume the actually #/s depends at what temperature you are using. Some simple testing showed that it is at the temperature of the facet. But unless you knew this you might not have the outgassing rate that you think you really want; ie if you kept the outgassing the same but changed the temperature the #/s actually has changed. If you want the same flux as at the older temperature you would need to adjust the outgassing rate. Personally, I would keep it fixed at whatever is considered the standard reference temperature for PV units, even thought the gas is actually comming of at the temperature of the facet as it should. I would also vote to include #/s and #/cm2s, which doesn't depend on the facet temperature, and doesn't cause any confusion. Lastly, I would add a note into the manual so you know at what temperature the PV units are used at.

The logic behind using the facet's temperature for #/s conversion is that the only way to control the initial speed of the molecules is by defining the source facet's temperature. Once we establish a pattern where the desorbing facet's temperature has an actual effect on the outgassing, it would be confusing to say that "the speed takes into account the facet temperature but the number of molecules assumes room temperature". But you're right, this should be clarified in the manual. I'll be honest: with the thesis submission nearing, I will make only critical bug fixes to the code in the coming months. Interface changes are always welcome but I'll work on them probably next year only.