[RASMB] Cell Leak

[Peter Schuck]

Hi all,

We've also seen a few times breakage of the center divider in the charcoal 
filled epon centerpieces from single-sector leaks.  I agree that using 
centerpieces that are rated higher is in principle a good idea.  However, 
we found that not really essential so far.

Since we regularly have to sediment at 60,000 rpm, we've implemented a 
protocol where we check the cells for leakage by sedimenting them briefly 
at a lower rotor speed, first, maybe 10,000 or 20,000 rpm.  After verifying 
that there's no leak (if there was it wouldn't destroy the cell at the low 
speed), we take the rotor out, shake it up, and start with the temperature 
equilibration at 0 rpm, followed by starting the run and acceleration to 
60,000 rpm.  In principle, that would not completely eliminate the 
possibility of leakage starting to develop at the high rotor speed, but at 
least we have not seen that happening so far.

This procedure is a bit cumbersome, and we don't always do it that 
way.  Alternatively, when using the interference optics it is usually 
possible to observe the status of all the cells during the time the rotor 
accelerates, which gives a chance to abort the run before it gets to a too 
high speed.  One can recognize one-sided leaks by diagonal fringe pattern, 
moving meniscii, or simply from the lack fringes due to scattering on 
deposits on the window.

So far that gave good results.

Peter