RE: Right angle scatter with UV laser line?
kukuruga%kasle1.dnet@rocdec.roc.wayne.edu
Thu, 12 Oct 1995 11:20:04 -0400
Several things to consider on the 90 SCR with the FACS 440 bench...
1) The 90 SCR reflective mirror is only a 5% reflect -- not much signal
to begin with, and even less with the typically lower ower used in the UV.
Therefore, you probably ned to increase PMT voltage ( I usually with from
~350V while using 488nm excitation, to ~450V whith UV exc.).
2) Be sure of the filter you're using in the path of the PMT. A UV bandpass
filter works great in the Forward SCR path, particularily if you're running a
secondd "green" laser...but, usually it's unneccessary in the 90 SCR path.
It's also possible, iff you are using some selective filter in the 90 SCR
path, that you're eliminating the signal completely.
3) The 90 SCR PMT on the 440 bench is a "green" optimized tube...works best
with wavelengths starting in the UV and progressing to the green-orange
region. It's usually the same as your PMT1 tube, unlike the PMT2 tube,
whicch is more "red" sensitive. No... the tube is probably not the problem
(that's assuming its asctually working?). I'd look to 1) or 2) for an answer.
Mark KuKuruga
K.C.I.