Log entry time 04:03:16 on March 8,2006

Entry number 165721

March 7, 2006



Two NMR/EPR/NMR calibrations were attempted.  The first one using the

Rb-87 frequency failed.  One hour later, the second one using the

Rb-85 frequency was a success.



NMR/EPR calibration parameters:



target magnet box current = 4.68 A

BigBite = 710.0 A

Oven Set = 250 deg. C

Oven Air flow = 211 units

heater temp = 365.5 deg. C

RTD left = 27.9 deg. C

RTD right = 27.7 deg. C

target position = polarized 3He

Lasers: all 4 lasers ON

Photodiode signal = -110 mV DC



EPR start lock-in phase = 112.3 degrees

EPR FG = 7.00 dBm



FM Sweep summary:



A series of FM sweeps were conducted for the various alkali's: RB-85,

Rb-87 and K-39.  Signals were found for each, but the K signals were

tiny (more on this in a forthcoming halog).  The Rb-87 signal

appeared artifically broadened by a background signal and the Rb-85

signal was very clean but asymmetric due to background.  

Jaideep tried to adjust the EPR lock-in phase to make the Rb-85

signal symmetric but was unsuccessful.  



Measurement summary:

22:24 NMR measurement.  P = 46.1%.

Xup = -104.0 mV, Xdown = -102.8 mV, Yup = -6.415 mV, Ydown = -5.501 mV



Locking was attempted at the Rb-85 frequency, but was aborted before

the spin flip because the lock did not look good.  Switched to Rb-87

which had a more symmetric but artificially broadened lineshape.

We've done this in the past with success, but this time a total of 4

AFP spin flips failed.

 

These EPR measurements at 22:28 and 22:35 apparently failed due to

insufficient gain.  This is not unsurprising since it is hard to

measure a precise feedback slope for a small noisy signal.



10:43 NMR measurement. P = 45.3%.

Xup = -102.4 mV, Xdown = -101.1 mV, Yup = -6.053 mV, Ydown = -5.218 mV



Gordon and Jaideep decide to try NMR/EPR/NMR again, but this time

using the Rb-85 signal.   The Rb-85 FM sweep before the first NMR

looked very clean, but was still asymmetric.  They feared that the

lock point was too near the turnover due to the asymmetric lineshape,

therefore, they devised a contingency plan to lock "manually" if the

lock was lost.  Note that after the first NMR measurement, the Rb-85

FM sweep resulted in a lineshape that was about twice as small.  They

waited a few minutes and tried again, but obtained the same results.

The gains were adjusted appropriately to compensate for this before

the EPR measurement.



Target RTD left = 27.2 deg. C

Target RTD right = 27.2 deg. C



11:43 NMR measurement. P = 44.5%.

Xup = -99.98 mV, Xdown = -99.61 mV, Yup = -6.167 mV, Ydown = -5.343 mV



11:55 EPR measurement. 

First flip = 43.5%, second flip = 43.0%.

During the measurement, the lock followed the first AFP spin flip but

was lost just before/during the second spin flip.  Subsequently,

Jaideep manually locked after the second AFP spin flip.



March 8, 2006

00:10 EPR measurement.

First flip = 43.0%, second flip = 42.8%.

During this measurement, under Gordon's direction, the wait time in

the opposite spin state was increased to 90 sec from 30 sec.  Before

the first flip, the signal was manually locked.  During the first AFP

spin flip, the signal was stayed locked.  The lock was then purposely

broken and relocked manually.  The lock was then lost once again

during the second AFP spin flip and then relocked manually.



00:17 NMR measurement.  P = 43.7%.

Xup = -98.31 mV, Xdown = -97.91 mV, Yup = -5.76 mV, Ydown = -5.019 mV



The EPR-NMR calibration constants from the last two EPR measurements

were consistent with each other and with the most recent previous

EPR/NMR calibration.