[RASMB] Laser delay jump

[Zhenli_Luo]

Dear RASMBers:
Recently a strange behavior occurred on our XL-I, described as follows:
Whilom, when using interference system in experiment, to obtain clear fringe
display, a laser delay was set to 180˚ for cell I at 3000rpm and adjusted to
about 180.5˚ at maximum speed on a 4-hole rotor, similar for other two cells.
But now it should be set to 180˚ at 3000rpm and about 177˚ at 60k rpm.
(The values tend to get smaller). This situation came suddenly since an experiment
conducted several days ago. A rotor speed at 60k rpm, 20 degree C, both UV-Vis and
interference detectors were used to collect data at a time interval of 2mins, the
data collected were alright at the first hundred scans, then very curious data
appeared, it seemed that there were no signal since then, only noise was contained
in data detected by both detectors, as shown in attachment. I regreted that I was
absent at that moment so no more detail can be provided.
I sought help from Beckman coulter engineer. Possible reasons such as overspeed
disk nick or tach module (which senses the magnets in the overspeed disk)
misalignment or mirror #3 shift were suspected, but these suspicion were all
eliminated by checking the collar offset value after a radial calibration and
pixels of inner and outer radius of counterbalance.
Does any AUC user encounter such problem? I beg your suggestion.
Any word will be greatly thanked.

Best regards.

Zhenli Luo
8th, May


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