Re: 100 mW argon laser 'double spot' on sample stream?

Hi Ray, 
First thing I would do is align the laser though the forward scatter channel, when you look at the laser beam image	is it a single round spot? How are your signals on beads? Its probably just a reflection off something maybe the window though which the forward scatter signal goes. Try covering that with a bit of paper or tape and see if the other laser spot goes away. Is the second spot intense enough for you to see beads fluoresing in the stream below the nozzle?  You can check the beam coming out of the front of the laser by expanding the beam with a lens onto a bit of paper, how does that look? You could then follow the beam though all the  optics to the flow chamber to find out where the second beam comes from but its probably just a reflection and nothing to worry about. 
 
Simon 
 

Simon Monard
Trudeau Institute
154 Algonqin Ave
Saranac Lake
New York
12983
Ph 518 891 3080

>>>Ray Hester <rhester@jaguar1.usouthal.edu> 04/28/05 9:40 am >>> 
 
Hi, 
 
 
We have a Spectra Physics 100 mW (SP model 277-GA01) argon laser on our 
 
Vantage - installed in August of this past year. 
 
Sometimes when we turn the laser on, a double spot appears on the sample 
 
stream.  Other times, e.g., the next day, there is only a very nice, 
 
tight single spot.  When the double spot appears, we check to make sure 
 
there are no air bubbles in the sheath fluid tubing.  Also, we take off 
 
the nozzle and check to make sure there's nothing in the opening.  No 
 
matter how the laser spot is focused using the beam focus knob or any of 
 
the other adjustments - X, Y, Z - the double spot won't go way.  And 
 
they aren't vertically aligned.  That is if you adjust the Y control 
 
knob, the two spots appear and disappear at different points - close but 
 
not one on top of the other.  And this occurs when none of the other 
 
lasers are turned on. 
 
 
Has anyone else with this laser experienced something similar? 
 
 
Thanks. 
 
 
Ray Hester 
 
Univ. of South Alabama 
 
rhester@jaguar1.usouthal.edu