Query on He-Cd Laser for FS
Howard Shapiro (HPANDA@HARVARDA.HARVARD.EDU)
Tue, 31 May 94 20:06:40 EST
Michal Bochenek reports problems using the Omnichrome HeCd laser for
forward scatter. This laser is multimode and unpolarized; its divergence
characteristics are such that there isn't any way to place a blocker bar
to block the beam without blocking the scatter signals, at least in my
experience. The laser is also very noisy. The best scatter signals I
ever managed to get with a multimode HeCd laser in a Cytomutt were so bad
I just gave up. There can also be a problem with scatter at 325 nm from
TEM00 HeCd beams because the scatter optics in at least some systems won't
transmit 325 nm. In the Elite, the best solution might be to use a low
power He-Ne collinear with the HeCd and a red filter in front of the
scatter detector.
I'd be interested to know if anybody has had better luck with multimode
He-Cd lasers for forward scatter.
-- Howard Shapiro
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