University of Wisconsin-Madison Physical Sciences Lab

Learn More: NIST Upgrade

PSL was responsible for the following areas in the upgrade of SURF2 to SURF3:

Magnetic simulation and redesign of magnet iron.
The orbit of the electrons, and the shape of the pole pieces is circular.
The return path is rectangular. The difference in shapes will produce some nonuniformity of the magnetic field. Verification of the field quality by simulation was necessary before committing to construction of the 4.9 meter (15 foot) by 2.7 meter (8.3 foot) steel core. ANSYS ® was used to verify the 0.02% field uniformity required as an electron travels around the orbit. The pole pieces include an accurately machined alignment shoulder.

[NIST SURF3 magnet section view]

General contractor for a complete magnet replacement.
To achieve the desired field, total replacement of the existing iron was needed. PSL subcontracted and supervised construction and assembly of the large steel sections required.

Design and construction of main field coils and trim coils.
Replacement of the magnet coils was also needed. PSL designed and constructed two main field coils, which each have a cross section of 18 by 18 cm (7 by 7 inches), a diameter of 2.4 meters (8 feet), and a weight of 1.5 tons. There are also 4 field trimming coils, each with mass about 34 kg (75 pounds).

Design and construction of field mapper.
The mapper can be thought of as a slender 2-axis robot for transporting a magnetic field
strength transducer to known locations in the symmetry plane of the magnetic gap. It consists of a drive package that mounts to the magnet iron from beneath, a radial arm which rotates in the gap (supported on its outer end by wheels that ride on the alignment shoulder in the lower pole piece), and a cart that travels on the arm. PSL designed, built and used the mapper.

[NIST SURF3 magnet mapper line drawing]

Mapping accuracy is 0.2mm in position and 0.003% in field strength. Results of the mapping can be seen in this paper on the conversion of SURF II to SURF III and include azimuthal variations of less than ± 0.01% under some operating conditions.

Design and construction of control system upgrade.
The design takes advantage of the rapid advances in digital controls that have occurred over the past 30 years.

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