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it sounds like you might have some "satellite" drops, these are the tiny
droplets that you can see through the telescope between the main droplets.
You should be able to lose them or merge them with the main streams by
changing the phase and/or frequency of the drive.
If you've got a B-D FACS, the easiest way to get rid of the streamlets is
to put the machine into test mode, open the two doors, remove the tube
holder, and examine the streams as low down as you can (below where the
tube bottoms would be) using the groovy flexible light, adjust the phase
until you get just one stream on either side. If you can't get single
streams that way, try shortening the charge envelopes, eg sorting 1-2
droplets, rather than three, this gives more uniform charging, and
therefore more uniform streams. If you do lower the number of drops, you'll
have to check that your break-off point is right, since fewer drops is less
forgiving of timing errors. Once you've found the phase that gives you the
best streams, take a look at the break off point and memorise the shape of
the last droplet still attached.
In short, I'd carry on as before, (I normally use the default nozzle
frequency), and adjust the drive amplitude to keep the break-off point
still, but adjust the phase so that the last droplet looks like it did when
you set up using test mode. On my machine I tend to get the best streams
when the last droplet is connected to the sheath by a pronounced neck, and
either has a round front, or a "nipple" with a pronounced neck immediately
below it. Often I can get the break-off point back in place using the phase
only.
The above would be easier to get across using diagrams, if you don't get
any joy from trying to implement what I suggest, or if you don't get any
better answers, let me know and I'll put some sketches on my web site
Good luck
Ray
At 3:20 pm +0100 19/6/97, Vincent Falco wrote:
>My problem is this:During some sorts I get ,what I will call a spurious extra
>drop. To explain more,there are times I sort to polycarb filters.When all is
>well I get a single spot which contains the desired cell population.When all
>is supposed not well I get my desired single spot with cells and just about a
>quarter of inch from the desired spot I observe a spurious spot,which does
>not contain the desired cells.I maintain the nozzle on a strict PM cleaning
>schedule and watch for clogs etc.during times of sorting.The drive frequency
>remains constant during a sort and is generally consistent day to day.The
>amplitude level requires adjustment during a sort run.Should I be suspect
>that the amplitude level is giving the problem? Can anyone suggest other
>potential problem areas.Can anyone give rules/guidelines they follow when
>establishing drop drive frequency and amplitude level?Thanks.
Ray Hicks
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CD-ROM Vol 3 was produced by Monica M. Shively and other staff at the
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