Re: Laser Focus on Stream in Air

From: Howard Shapiro (hms@shapirolab.com)
Date: Fri Apr 27 2001 - 16:01:34 EST


Sam Witherspoon wrote-

>         For years I have been adjusting the beam *focus* on our sorter with
>help from a pulse width signal, in this case, FSC width.   The idea is that
>the smallest width represents the smallest beam spot.
>  *I use glut.-fixed chicken red blood cells on a FACStar Plus. (100u nozzle)
>with an elliptical spot.
>  *488nM laser at 60mW.
>  *The CV's I get on PI-stained CTN are 3% at 256 channel resolution, which I
>believe for this type of instrument is quite good.

As long as the shortest pulse width is associated with the biggest signal
and the lowest CV, you're OK.

The potential problem is moving the beam so the core is near the edge
rather than the center of the ellipse, which could potentially give you
shorter pulses, which would be of relatively low amplitude and high CV.

I hope to have some of the hands on Cytomutt stuff which was axed from the
3rd Edition on the Web site which will be set up for the 4th Edition.

-Howard



This archive was generated by hypermail 2b29 : Sun Jan 05 2003 - 19:01:16 EST