Calibration data was taken in 11/2001 and 9/2003.

The calibration in 11/2001 was after the HH apparatus was moved to bldg 25.  The calibration in 11/2001 was not very good.
The Measured calibration divided by the geometrical calibration (which uses the measured current of the calibration coil) was

1.003875 (11/2001 measured/geometric)

this is in contrast to 9/2003 which was

1.000483 (9/2003 measured/geometric).

The 9/2003 calibration is more in line with the historical calibration numbers of the HH apparatus before 
it was moved to bldg 25.

The change in the calibration seems to be due to mechanical wear of the bearings for the HH apparatus.  
Basically the calibration measured/geometric ratio became good again after the bearings were replaced in the 
HH apparatus and the apparatus was put together such that the coupling between the table and the roulon 
bearing was resting on the ceramic spacer, with two teflon washers added, one in between the coupling and 
the spacer and one between the spacer and the bearing cup. 

Now it seems that the calibration change between 11/2001 and 9/2003 (and previous calibrations) was real.  
Data taken between 11/2001 and 9/2003 has to be reconciled. The ratio between each calibration period is the 
ratio of the Measured/Geometric Magnetic Moments at each date.

1.003391  ( Mag Mom/I for 11/2001  /  Mag Mom/I for 9/2003)

Thus data taken between 11/2001 and 9/2003 will appear 0.339 % larger than if measured after 9/2003.


On Mar 31, 2004 calibration done after bushings (bearings) were all changed.  The calibration is:

1.001532 (3/31/2004 measured/geometric).  

Also the angle was found to be off by 92.58 degrees, due to work done at some point.

On May 5-6, 2004 calibration done before NLC PM blocks measured.  The calibration is:

1.001822 (5/5/2004 measured/geometric).  

On June 3, 2004 calibration done before NLC PM blocks measured.  The calibration is:

1.001534 (6/3/2004 measured/geometric).  

On June 18, 2004 calibration done before NLC PM blocks measured.  The calibration is:

1.001705 (6/18/2004 measured/geometric).