Well, as I recall even in laser ablation of oxides materials in a hard
vacuum with a distribution of particles that went as (cos (theata))^10
and with an angle of 45 degrees between the laser beam and the normal of
the target I needed to clean the windows every six months. I don't think
the thursters have as sharp of distribution of particles as I had;
though, I could wrong on that point.
Ugh again. As project administration I'd definitely want
it checked out if for no other reason than CYA (for the next
Now I'm wondering how this has been avoided in previous
spacecraft design. Somebody's already done this work.
Mark L. Fergerson
Look sputtering Mo and the deposit of it on a surface can lead to many
different crystalline structures. These structures as you rightly point
out depends on temperature, sputtering rates, co-sputtering of the film,
the kinetic energy of the clusters and ions hitting the film, the
energy and type of ions used to sputter from the target, and the rate of
sputtering. The best way I believe to get accurate estimates of the
properties you desire is to just make the film in an environment as
close as you can to the space environment and then measure the DC
resistivity versus temperature and use that in your calculations. Also,
remember Mo may oxide over long periods in space do to atomic oxygen.
This will change the reflectivity of the film.
Measuring the DC resistivity only requires a closed cycle refrigerator,
a temperature controller, dc constant current source, a nanovoltmeter,
some connectors, a Si-thermometer. If you want it automated then you
need a 486 computer with an IEEE-488 card for controller and limited
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