Q1 and Q2 field mapping

The Q1 and Q2 were mapped with a Hall probe (FW Bell STF-99-0402) attached to a field mapper which can scan the space in three dimensions (table 14).The Hall probe can be rotated by 90 degrees to measure $B_x$ or $B_y$.

表 14: Specification of the field mapper used for Q1 and Q2

Degrees of freedom	4 (x, y, z, $\theta$)
Position accuracy ($\mu$m)	30
Reproducibility ($\mu$m)	10
Accuracy of the measured field	$5 \times 10^{-5}$

The measured excitation curves for Q1 and Q2 were compared with TOSCA calculations. They are reasonably consistent (figure 30,31) and the required fields were obtained well below the maximum current.

The obtained field data are now being analyzed and converted to the field map. Figure 32 shows the B$_y$ field of the Q1 magnet along beamline (Z) at some points. The measured fields and TOSCA calculation are consistent to the first order.