QE-N2 Pole Tip Field Measurements

                                    Achim Weidemann   08-Feb-2006

This note reports the pole tip field measurements taken
on the QE-N2 Quadrupole magnet
by Jim Spencer and Achim Weidemann on February 7, 2006.

The field was measured using a Sypris 7010 Gauss/Teslameter
with the probe  FW Bell HTM71-0608-30-T  S.N. 0480178.  
The red dot on the probe pointing at a North pole gives a positive
reading.

The four coils are named by their view from the side of the trim
connectors    (not main coil correctors/cooling water) as
['upper' | 'lower']['left'|'right']

Numbering the 4 connectors on the connector blocks (on left bottom 
and left top) from bottom to top from 1 to 4, 
for the 'quadrupole trim' hookup, 
      the bottom left connector 1 is current in  (+)
      the top left    connector 1 is current out (-);
for the 'dipole trim' hookup, 
      the bottom left connector 3 is current in  (+)
      the top left    connector 3 is current out (-).


First measurement:
 
 Main coil current 0; 
 trim current connected for quadrupole trim (+ Polarity)

  Trim Current   'lower left'  'upper left' 'upper right' 'lower right'
    [A]             Gauss       
  -------        --------      -----------   --------      ------  
    0               4.5          -4.35          5.51        -5.3  

    6.107        -357          -358           360          -359        
  -------        --------      -----------   --------      ------  
 
Second Measurement:
 
Main coil current 0; trim current connected for dipole trim 

  Trim Current   'lower left'  'lower right' 'upper left' 'upper right' 
    [A]             Gauss       
  --------        --------      -----------   --------      -----------  
   -0.004           6.9           -7.85        -6.7           8.0

    6.107           254.           220.        -281.         -246.7
                                               -285.
  --------        --------      -----------   --------      -----------  
  

Third measurement:

Trim coil currents 0.
Standardization of main coil, 3 ramps to (120 A, 0 A).

Main Current   'lower left'  'lower right' 'upper left' 'upper right' 
    [A]             Gauss       
----------        --------     -----------   --------    -----------  
  -0.002            13.5         -14.6         -13           -14.3

  10.010           280.          -280.        -280.           279.

  40.055          1073.         -1078.       -1078.          1080.    

  60.076          1607.         -1619.       -1617.          1617.

 100.121          2680.         -2690.       -2672.          2680.   
----------        --------     -----------   --------    -----------  
 
Notice that the accuracy of these measurements is quite limited,
slight movements of the probe from the exact poletip center in the magnet
may change those in 
 the single Gauss range by ~<10%,
 the 100s of Gauss range by ~5%
 the kGauss range        by ~1%.



This note can be found on the web at
http://www-group.slac.stanford.edu/met/MagMeas/MAGDATA/E163/quad/QE-N2/QE-N2-PoletipFields.txt