2. When distance a = R the coils can be joined together with
the spacers.
a) Measure Bz (z, r) as shown in Fig. 4. Set the r-coordinate
by moving the probe and the z-coordinate by moving the
coils. Check: the flux density must have its maximum
value at point (z = 0, r = 0).
b) Turn the pair of coils through 90° (Fig. 5). Check the
probe: in the plane z = 0, Bz must = 0.
3. Short-circuit first one coil, then the other. Measure the radial
components of the individual fields at z = 0.