Hi That pressure level pretty much rules out mechanical pumps for the operating mode. A roughing pump would still be needed to get things going. It also takes the level of machining on the fittings well beyond the reach of most machine shops. Some of the stuff has to be exact, close to a tolerance won't do the trick.
Bob On Sep 2, 2010, at 4:39 AM, Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote: > Bruce Griffiths wrote: >> Poul-Henning Kamp wrote: >>> In message<4c7f5918.7030...@xtra.co.nz>, Bruce Griffiths writes: >>> >>>> Indicates that the operating pressure at the hydrogen dissociator is >>>> likely to be a few Torr or so. >>> The pressure is basically: "As low as possible" in order to minimize >>> hydrogen collisions (other hydrogen, walls) as much as possible. >>> >> i.e. the mean free path of the atomic hydrogen needs to be somewhat larger >> than the dimensions of the (fused silica) gas containment bulb. >> >> The mean free path will be comparable to the bulb dimensions at a pressure >> of around 1 ubar (100 uPa) or so. >> >> Since the Hydrogen atom bounces of the fluoropolymer coated walls thousands >> of times before phase coherence is lost the mean free path needs to be >> several thousand times the containment bulb dimensions to avoid degrading >> the maser performance. This requires a pressure of around 1 nanobar (100nPa) >> or below within the storage bulb.. >> >> The (gas) conductance of the exit aperture of the dissociator is selected to >> achieve the required atomic hydrogen flux of at most around 3E-5 >> liter-Torr/sec or so for a typical hydrogen dissociator pressure of 50Torr >> or so. >> >> Bruce >> >> > Oops!, the pressures given in Pa above are out a few orders of magnitude. > Correct values are: > > The mean free path will be comparable to the bulb dimensions at a pressure of > around 1 ubar (0.1Pa) or so. > > Since the Hydrogen atom bounces of the fluoropolymer coated walls thousands > of times before phase coherence is lost the mean free path needs to be > several thousand times the containment bulb dimensions to avoid degrading the > maser performance. This requires a pressure of around 1 nanobar (100uPa) or > below within the storage bulb.. > > The (gas) conductance of the exit aperture of the dissociator is selected to > achieve the required atomic hydrogen flux of at most around 3E-5 > liter-Torr/sec or so for a typical hydrogen dissociator pressure of 50Torr or > so. > > Bruce > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
