https://www.febo.com/pipermail/time-nuts/2017-April/104600.html
We hooked up the oscilloscope directly to the electron multiplier in the beam tube with a 1 Meg termination. We were operating open loop and varying the fine crystal oscillator adjust for the different photos. Remember that higher beam current is downward in the photo. Currents listed in nA translate to beam current numbers on the HP5061B meter. First photo at http://gonascent.com/papers/hp/hp5061/waveform/centered.jpg is the frequency swept at a 137 cps rate around the peak of the cesium resonance. Ground is at the top of the screen and 5 mV (also 5 nA) per division. Horizonal is 4 ms per division.This corresponds to a peak beam current of -22 nA and a valley current of -17 nA. One valley current is below resonance and the other is above resonance. The waveform is 274 cps. Sequence is low to high and then high to low. No 137 cps is present. The fine frequency control was adjusted to produce a slight offset from center for the photo at http://gonascent.com/papers/hp/hp5061/waveform/smalloff.jpg . Note that the peak beam current is still -22 nA but two different valley currents exist. One is 17 nA and the other is -18 nA. Most of the signal is 274 cps but some asymmetry is present at 137 cps. One extreme of the sweep is slightly closer to center frequency than the other. Finally the frequency was adjusted to produce a severe offset with all of the sweep below resonance in the photo of http://gonascent.com/papers/hp/hp5061/waveform/largeoff.jpg . The peak is now slightly below resonance at -21 nA and the valley is far below resonance at 5 nA. The signal is all 137 cps with no 274 cps. See figures 4-43 and 4-44 on page 4-31 of the manual for further explanation. We will be finding out the effect on beam current of tests shortly on the Zeeman coil and LF coil. We think that the 55.53 kc Zeeman frequency introduces some AM into the beam frequency but no FM. What the LF coil has is unclear at this time. πθ°μΩω±√·Γλ WB0KVV _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.