Superconductive Solenoid Design

A literature review on the current state of design is presented to define the proposed design and material limits to be assessed.
In 1911, the Dutch physicist H. Kamerlingh Onnes discovered the phenomenon of superconductivity, the vanishing of electrical resistance in some metals at very low (<10 K) temperatures. The discovery inspired Kamerlingh Onnes to propose a 100,000 Gauss (10 T) solenoid two years later based on a superconducting coil cooled with liquid helium, yet it took more than 50 years to realize this design in practice [61]. In 1989 Motokawa et al at Tohoku University built the first of a series of a new class of resistive magnet that were referred to as repeating pulsed magnet [43] which provided pulsed fields of a few millisecond duration as high as 25 T once every 2 second [8]. These repetitively pulsed magnets were first built in a solenoid configuration [44, 8, 21] Today, pioneering research is being conducted by several high magnetic field centres [13, 19] around the world which are achieving >100T strength fields and long pulse lengths.
Particle accelerators have used superconductive components for many years to achieve the required energy densities in size constrained tunnels underground [1, 31]. The superconductors allow current densities orders of magnitude greater than regular resistance conductive materials like copper [51]. Initially, small accelerators used strings of permanently active electromagnets to create a controlled turning path for particle beams but with developments in high energy pulsed electromagnetics across the past two decades this has changed [31, 51]. Development of high energy pulsed solenoids (HEPS) has allowed a series of timely pulses to turn the particle beams direction, reducing accelerator energy costs and rapidly advancing electromagnetic design and research [27, 31, 50, 51]. The progress in pulsed high magnetic field research in the last two decades was driven by the transition to multicoil superconductive solenoid designs [22] and capacitor power systems [18, 21, 24].
The addition of multiple concentric coils each pulsing as the successive outer coils are energised is the key [23] to reaching 100T fields and beyond [54]. The design improvements and high energy density components required to achieve such a field enables high quality, high power solenoids scaled to a small satellites capacitor system power output. A field of >100T is likely not required in the proposed contex. Magnet designers frequently trial improvements on 0.5m to 2m test coils [14, 41, 62] and a review of papers on small bore coils [13, 40] shows that high field pulses are achievable in a satellite deployable package. [8, 12] By using the highest current densities achievable, the solenoids pulsewave induces the strongest current in the object above and the induced field repulsion force is maximised as shown in Section IV.
As research has optimised NbTi cables almost to their material limits, Nb3Sn has seen increased development as the next generation substitute due to its higher temperature, field strength & current density capabilities [27]. Nb3Sn is superconductive below 18.1K with a maximum critical field strength of 25T, if the material exceeds either of these limits then a quench occurs where superconductivity is lost and the pulsed power must be diverted. Later research has refined the thermodynamic field strength surface that bounds the material’s superconductive state and the field penetration depth as the effect is lost in a quench. The critical surface of Nb3Sn is shown in Figure 2 with a reference density of 3000 A/mm2 across the SC area selected [27, 53].