[RASMB] Lamp Diagnostics

[Borries Demeler]

> 
> Borris,
> I believe it's because there is a windowless cell. Often I run the holimum oxide cell which has a 3krpm speed limit.
> Then I do a wavelength scan on the holimum oxide cell.
> Also you would have to wait for a 50u vacuum, and wait until it gets to 60k to do the test. 
> You can do the 3k test without a 50u vacuum. It takes only a few minutes.
> So actually you get done faster @3k.
> John Gunther

We usually don't scan any cells, just an empty hole. You still need the counterbalance
and an assembled cell as counter weight. I see your point about waiting for the vacuum.

A couple other points I'd like to make: 
I think it is useful to do a wavelength intensity scan at 3 different positions in the 
cell, say 5.9, 6.5, and 7.1, and also an intensity radial scan across the entire cell.

The intensity radial scan will tell you if you have dirt in the optics (PM tube window,
slit assembly, for example), the overlays of the wavelength intensity scans at 3 points
will tell you if there is a variation of intensity just in some wavelength regions, and
it will tell you if the monochromator will report the same peaks every time you scan.
I have seen some poor monochromators that have large variations from scan to scan, you
would never pick this up unless you did multiple wavelength intensity scans. It is one 
thing if the monochromator doesn't go to the position you are asking it to, but it is
quite another if it reports the wrong wavelength. See attachment - that example has a 
lot of problems. How can one fix the lambda shift between the channels?

-b.
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