[RASMB] noisy interference data

[Dmitry Veprintsev]

Dear Mark,
on several instruments I had laser duration of 0.6 deg would be too long and
would result in completely saturated interference image.
0.1 or 0.2 were usual settings in my case.

The cell width is about 2 deg. If the pulse width is comparable to this
width, any small error  in the timing would result in hitting the side of
the cell.
Please correct me if I am wrong.
best regards, Dmitry

On Thu, Feb 24, 2011 at 2:50 PM, Mark Agacan <M.Agacan at dundee.ac.uk> wrote:

>  I checked the laser settings as advised and found:
>
>
>
> cell
> laser delay
> laser duration
> exposure time 2 157.1 deg
>
> 1.7 deg 6.30 uS
>  4
> 67.1 deg
> 0.6 deg
> 2.22 uS
>  6
> 337.6 deg
> 1.7 deg
> 6.3 uS
>
> I also found this in the rasmb archives:
>
> "The main "gotcha" about setting the duration is that if you go too high
> you
> will end up with the superposition of a single-slit interference pattern
> upon the
> double-slit interference pattern.  As long as you use the typical *0.5 -
> 0.8
> degrees for the duration* (assuming that you are NOT using the old style
> interference
> window holders) you will be fine."
>
> So  I'm thinking to bring the laser duration for cell2 and cell6 down to
> the value of cell4.  Any further advice is greatly appreciated.
>
> Many Thanks,
>
> Mark
>
>
>
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Dr Mark Agacan, Scientific Officer for the Division of Biological Chemistry
> and Drug Discovery,
> Wellcome Trust Biocentre, College of Life Sciences, University of Dundee,
> Dundee, DD1 5EH
> Tel: +44 1382 386095    Fax: +44 1382 345764    Mobile: 07525 451 117
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>  ************************************************************
>  Please consider the environment. Do you really need to print this email?
>
>
> >>> Tom Laue <Tom.Laue at unh.edu> 2/24/2011 13:05 >>>
> Hi Mark-
> The interference system requires the use of sapphire windows, except at
> very low rotor speeds.
> Modern synthetic sapphire windows may be used to 230 nm. The old
> sapphire windows were not clear much past 280 nm, but that is no longer
> an issue.
> I know that some labs have switched to using only sapphire window since
> they almost never break, and may be used with all three optical systems.
> Best wishes,
> Tom
>
> On 2/24/2011 4:37 AM, Mark Agacan wrote:
> > Hello,
>
> > I have attached a jpeg image showing recent SV interference data plots
> > taken from sedfit.
> > All data was collected with quartz windows as I was primarily
> > interested in the absorbance @ 280 nm signal.
> > IP2 and IP6 are very noisy but IP4 looks fine.
> > Is this a calibration problem or is this related to damaged windows /
> > centerpieces (there are no visible defects or scratches on any of the
> > components).
> > Many Thanks,
> > Mark
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > Dr Mark Agacan, Scientific Officer for the Division of Biological
> > Chemistry and Drug Discovery,
> > Wellcome Trust Biocentre, College of Life Sciences, University of
> > Dundee, Dundee, DD1 5EH
> > Tel: +44 1382 386095    Fax: +44 1382 345764    Mobile: 07525 451 117
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > ************************************************************
> > Please consider the environment. Do you really need to print this email?
> >
> > The University of Dundee is a registered Scottish charity, No: SC015096
>
> >
> >
> > _______________________________________________
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>
> --
> Department of Biochemistry and Molecular Biology
> University of New Hampshire
> Durham, NH 03824-3544
> Phone: 603-862-2459
> FAX:   603-862-0031
> E-mail: Tom.Laue at unh.edu
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>
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>
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-- 
Dr. Dmitry Veprintsev
Biomolecular Research Laboratory, OFLC/103
Paul Scherrer Institut
5232 Villigen PSI
Switzerland
Tel +41 (0) 56 310 5246; Fax +41 (0)56 310 5288
dmitry.veprintsev at psi.ch
http://www.psi.ch/~veprintsev_d
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