Letting Rb Cell temp equillibrate is important to getting a stable signal from the PD.  Can take up to 20 min.

Start by turning Horizontal and vertical fields all the way down.

Sweep at 1s.

First thing is to adjust sweep field and recorder offset to obtain full +/- 14V sweep amplitude to ensure starting with largest possible range.  I was able to get +/- 14.2V

Next adjust vertical field to minimize dip width.  Then adjust apparatus orientation to minimize dip width.  Infinite persistence is helpful here.

At PD resistance 333k, amp gain = 5, 1ms TC.  I get average peak amplitude 0.80 V with FWHM = 7.2ms.

Start with FN Gen ~50kHz and 700mVpp on 50ohm output term.

Measure Isotope separation and amplitudes.

Big peak amplitude is 616mV at sweep voltage -10.2V.

Small peak Amp = 232mV at sweep voltage -8.4V.

Measuring Earths B.

Horizontal mag field = 0.  No RF.

For Horizontal Field use technique of zeroing in on center dip by narrowing sweep ramp until it is almost costant.  Then put sweep time high to measure vertical current at low and high point of sweep with minimum of dip close to center.

Low = 278.5 mA.

Hi = 281.3mA.

For Vertical Field just measure current that minimized width of the peak.

253.1mA.

Nominal Values for Earths field.

Bx = 18.7

By = -0.8

Bz = 52.9

B = 56.1