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FMCG/Operating procedure: Difference between revisions
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# If not done already, turn on the TEC and LD for the probe laser diode (the right-hand SRS LDC501 controller). We have historically and recently run at 170.00 mA of laser diode drive current on the probe. With this drive current, the D2 absorption line occurs at a "temperature" of roughly 7.05 kΩ and we generally do our magnetometry at a temperature of 8.5-9.5 kΩ.
# Now return to the rear of the rack and, after verifying the probe tapered amplifier TEC 2000 temperature controller is enabled, enable the probe tapered amplifier output by pressing the '''output''' button on the Newport Model 560B driver. The drive current on the TA sets the eventual light intensity on the detectors. Historically, we have worked with currents as high as 1200 mA, though recently we have worked at much lower values around 750 mA, which delivers ~500 μW of laser power through a hot cell to the detector.
# Once the TA is enabled and light is being sent to the detectors, adjust the gain settings on the I-V converters appropriately. 100-200 uA/V is usually appropriate for the laser powers mentioned above.
# At this point, the detector sum signals should be visible on the scope. The signals should be pretty constant over time. If you notice non-periodic "noise" on this signal, it's possible the alignment between the TA and the fiber input is poor. While monitoring the signal, go behind the rack and walk the beam using the two mirrors on the second shelf from the top.
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