From: Les Hicks <hicks@gpu.srv.ualberta.ca>
  To  : RASMB@BBRI.HARVARD.EDU
  Date: Fri, 28 Feb 1997 10:08:29 -0700

Sapphire Window Blurring

Hi John,

        Sorry it's taken me so long to get back to you.  I've been away from
work for a few days dealing with water problems at my house (but don't get
me started on that!).  I'm glad you wrote about the windows, because I had
planned to post a notice about them on the bulletin board,  but things have
been so hectic  around here, I guess it got forgotten in the shuffle.
Regarding the windows,  after receiving the replacement windows, and playing
around with different cell assemblies, I came to the realization that the
problem wasn't with the windows after all.  It was the cell assemblies.
When I  installed the windows that had previously been blurring in different
cell assemblies, the blurring cleared up.  There is no noticeable difference
(warping or distortion)  between the components of the problem assembly and
assemblies that work okay.  I ended up just mixing and matching components
until I had good sets to use.   This is a problem that I have never come
across before so I'm not sure which component (outer ring, centerpiece,
window holder) is causing the blurring.  I'm quite sure it's not the window
liners or gaskets, as I regularly replace them as a matter of course. 
        It was nice to hear from you.  I met you a couple years ago at
Wyatt Technology's Laser Light Scattering User's Forum.   I could sure use
some of that California sunshine right now.

Cheers,

Les Hicks
Dept. of Biochemistry
University of Alberta

P.S.   In regards to discerning between "good" versus "bad",  the blurring
is very noticeable when it occurs.  It usually appears in the bottom region
of the cell, to the extent that the fringes become so blurred that you can't
resolve one fringe from another so that it is impossible to make any
measurements.  I'm not familiar with the optics in the XLI, but I assume the
camera would display the same phenomena on the monitor if the blurring was
occurring.




>Les,
>
>Did you ever get a resolution to your November query about blurring of
>the fringes?  Did replacement windows work any better?  
>
>I think it would be useful to many people if you could post further info
>about this to the RASMB list, especially since there are many new XL-I
>users who, like myself, may not be entirely sure what "good" versus
>"bad" ones look like.
>
>John Philo, Amgen
>
>