SUPERCONDUCTING MAGNET TECHNOLOGY

Superconducting magnet technology deals with the design, manufacture, and operation of superconducting magnets. A superconducting magnet is a highly stressed device: it requires the best that engineering has to offer to ensure that it operates successfully, is reliable, and at the same time is economically viable. A typical 10-tesla magnet is subjected to an equivalent magnetic pressure of 40MPa (nearly 400 atm), whether it operates superconductively at 4.2K (liquid helium) or 77K (liquid nitrogen), or resistively at room temperature. Superconducting magnet technology is interdisciplinary in that it requires knowledge and training in many fields of engineering mechanical, electrical, cryogenic, and materials

Table 1.1 lists “first” events relevant to superconducting magnet technology. Particularly noteworthy events since the discovery of superconductivity in 1911 by Kamerlingh Onnes, who was also first to liquefy helium in 1908, are as follows:

• 1. Water-cooled 10-T electromagnets: Francis Bitter, the 1930s;

• 2. Large-scale helium liquefiers: Collins, the late 1940s;

• 3. Magnet-grade superconductors: Kunzler, et al., the early 1960s;

• 4. Cryostability of magnets: Stekly, the mid 1960s;

• 5. High-temperature superconductivity (HTS): Müller and Bednorz, 1986.

Although “Bitter” electromagnets, resistive and water-cooled, operate at room temperature, we may safely state that Bitter initiated modern magnet technology. Soon after the availability of Collins liquefiers, liquid helium-until then a highly prized research commodity available only in a few research centers-became widely available and helped to propel the rapidly growing field of low temperature physics. Many important superconductors were discovered in the 1950s, leading to the development in the 1960s of magnet-grade superconductors that continues today.

The formulation of design principles for cryostable magnets by Stekly and others by the mid 1960s was perhaps the single most important step in the early stage of superconducting magnet technology. It definitely helped transform superconductivity from a scientific curiosity to a realistic engineering option. Advances in superconducting magnet technology since then have succeeded in developing “highperformance” (“adiabatic,” i.e., non-cryostable) magnets that now dominate most “marketplace” superconducting magnets.