[RASMB] vacuum fluctuation

[QCZ]

This is a good suggestion. Thanks Tom. An intensity scan certainly would
help.

best,

Chin


On 10/20/08, Tom Laue <tml at cisunix.unh.edu> wrote:
>
> Hi Chin-
> This sounds like a "puff" of oil vapor being released during acceleration.
> The vapor is warmer than the rest of what the radiometer is viewing, so a
> rise in temperature is registered. The puff of oil vapor may indicate a
> problem in the seal between the drive and the chamber, but not necessarily
> so.
> Noisy data would result if there is oil getting on the optics lowering the
> signal level.
> I would suggest that you do a wavelength saving the data as intensities.
> Check that the 230 nm intensity peak is the highest. If not, the source and
> perhaps the detector need to be cleaned.
> Best wishes,
> Tom
>
> Walter Stafford wrote:
>
>> Hi Chin,
>>
>>   This could be caused by the switch from the thermistor to IR temp.
>> sensing mechanism. The switch occurs at 100 microns of pressure in the
>> chamber. You can avoid this usually by turning on the diffusion pump while
>> you are equlibrating the machine before the run. And to accomplish that you
>> must enter a speed of 0 (zero) and press "Start". If your rough pump is not
>> pulling the vacuum below 100 microns, the switch to the IR sensor will not
>> occur before you start and the diff pump heats up. I have seen this on both
>> my machines. It also sounds like your vacuum gauge calibration may be off. I
>> am surprised that this lead to so much extra noise, tho.
>>
>> Walter
>>
>> QCZ wrote:
>>
>>> Hi all,
>>> I have recently seen a vacuum jump from 9 microns to 45 microns during
>>> the acceleration to 50K rpm. At the same time, the temperature goes up to
>>> 20.4C from the set temp of 20.0C. It came back stepwise to 20C after 2
>>> minutes based on the temperature plot in sedfit.  My experience is that this
>>> cooling took too long. The data fit was really noisy with the rmsd of 0.015
>>> (total OD280=0.9) or above and the residual was bad for the first 45 scans.
>>> Is this a vacuum issue or the temperature control problem? Any input will be
>>> appreciated.  Thanks.
>>>    Chin
>>> ------------------------------------------------------------------------
>>>
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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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