Evaporative cooling settings

Our evaporation ramp to a 87RB BEC (16 February 2009)

Time (ms) Final Frequency (MHz) Power (Vcontrol)
50 18.3 2.0
150 11.0 2.0
225 7.0 2.0
250 4.80 2.0
300 2.80 2.0
300 1.80 2.0
1000 1.20 0.65 (lin. ramp)
2000 0.80 0.65
1000 0.743 0.65

Things to remember:

  • DDS likes to have continuous frequency ramps; make sure there are no jumps in frequency.
  • The atoms like to have a continuous power of rf. Park the DDS at a single power, usually "50%" and use the variable attenuator to control the power.
  • Check once in a while for spin mixtures. These are caused by too much or too little rf power near the end of the evaporation ramp. Find the happy medium.
  • After finishing evaporation, ramp frequency back up to some high value (like, 5 MHz), with continuous power, before shutting off DDS

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