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User name mack
Log entry time 00:36:46 on June 20,1998
Entry number 5788
keyword=more bcm progress
Woody from AES loaned me a better RF source which I used to check the linearity of the modified rms-dc converters in the bcm electronics. Yesterday's measurements had problems. The slope changes less than a few percent over the range 50 nA to 200 nA which is adequate for this experiment even if there are (uncorrected) helicity correlated intensity variations of order a percent. (We need 10-4 in the Q+/Q- ratio.)
The beam was cranked up to roughly 2 microA so I could have more stable beam to roughly adjust the central frequency of the tight filter in the rms-DC converters. The higher current also enabled me to measure the frequency out of the downconverters: 101.15 and 102.9 KHz. With a signal generator I should be able to do an excellent centering of the filter without beam.
For my own reference, the gains for bcm1 and bcm2 at the output of the rms-DC converter are 11.6 mV/nA and 11.9 mV/nA, respectively. The fundamental assumption is that 100 nA thru the cavity downstairs yields -63.4 dBm upstairs and that the RF source is good to a few percent. The cavity+long cable calibration constant of -63.4 dBm needs to be remeasured. Loss in the 1 meter long cable (1dB?) between the RF source and the downconverter has not been taken into account.