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Electric propulsion is seen as a potential solution for reducing greenhouse gas emissions from the aircraft industry. However, electrical machines must achieve high power to mass ratios (PtM) to meet aviation requirements. Superconducting technologies are a promising option for creating compact and efficient machines. Indeed, superconductors make it possible to generate large magnetic fields while reducing the need for ferromagnetic materials. In previous works, a 50 kW partially superconducting flux modulation machine has been realised. The flux modulation machine is an unconventional topology where the inductor is composed by a large static superconducting coil and rotating superconducting bulks acting as magnetic field shields. This topology allows controlling the inductor excitation while being brushless. In this paper, we design a 500 kW flux modulation machine considering the results of the 50 kW prototype and the constraints due to the structure change of scale. The presented machine aims to reach a power-to-mass ratio of 10 kW/kg.

Absolut System has built a 30 K and a 10 K remote Helium cooling loops used as a vibration free cooling source, respectively for IR detectors electro-optical characterization test bench and two-stage optical cryostat. The circulation loops are based on a by-passed flowrate from either a two-stage Gifford-McMahon cryocooler or a two-stage Pulse Tube cryocooler. Dedicated compact and high efficiency tubes & shell heat exchangers have been designed and produced for the recuperators. The paper describes the design and the performances of the vibration free cooling system produced. The current work towards a 4 K low vibration cooling source will be introduced as well.

Fabrum Solutions, in collaboration with Absolut System and Callaghan Innovation, produce a range of large pulse tube cryocoolers based on metal diaphragm pressure wave generator technology (DPWG). The largest cryocooler consists of three in-line pulse tubes working in parallel on a 1000 cm3 swept volume DPWG. It has demonstrated 1280 W of refrigeration at 77 K, from 24 kW of input power and was subsequently incorporated into a liquefaction plant to produce liquid nitrogen for an industrial customer. The pulse tubes on the large cryocooler each produced 426 W of refrigeration at 77 K. However, pulse tubes can produce more refrigeration with higher efficiency at higher temperatures. This paper presents the results from experiments to increase overall liquefaction throughput by operating one or more pulse tubes at a higher temperature to pre-cool the incoming gas. The experiments showed that the effective cooling increased to 1500 W resulting in an increase in liquefaction rate from 13 to 16 l/hour.

Fabrum Solutions in collaboration with Callaghan Innovation has been developing large pulse tube cryocoolers based on Callaghan Innovation's diaphragm pressure wave generators (DPWG). The pulse tube's lack of moving parts in combination with the DPWG's metal diaphragms produces a cost-effective, long life and robust cryocooler. The DPWG has had 10 years of development, resulting in a series of DPWGs ranging in input powers from 0.5 kW to 30 kW that have been coupled to a variety of in-line and coaxial pulse tubes. Two DPWGs have had in excess of 7000 hours running to date. The PTC330 cryocooler is based on a new 330 cc DPWG and has produced 480 W of cooling at 77 K during testing. The PTC1000 combines three such pulse tubes on a single 1000 cc DPWG to produce 1270 W at 77 K. This paper details the development of the PTC330 and PTC1000 cryocoolers from initial lab prototypes through to commercial products, integrated into liquefiers and ready for use in applications such as: Nitrogen liquefaction, re-liquefaction of boil-off from storage tanks, or cooling of cryostats for High Temperature Superconductor applications.

Fabrum Solutions in association with Callaghan Innovation and Absolut System has developed a 330 W pulse tube cryocooler based on Callaghan Innovation's novel diaphragm pressure wave generators (DPWG). A cost-effective, long life and robust cryocooler has been achieved due to the pulse tube's lack of moving parts and the DPWG's metal diaphragms separating the working gas from the oil lubricated drive mechanism. A 330 cc DPWG was designed and manufactured to run with an inline pulse tube. Absolut System carried out the pulse tube design; manufacture was by Fabrum Solutions, with integration and testing by Callaghan Innovation. The 330 W pulse tubes were run as cryocoolers mounted to 330 cc DPWG's. 480 W of cooling power at 77 K was achieved (target was 330 W at 77 K) from 7kW PV power and 12 kW of electrical input power. An endurance cryocooler was assembled with the left over parts from the optimization exercise. The endurance cryocooler was assembled to run as a liquefier. Calculation showed that 1 litre per hour of liquid nitrogen production was possible from 91 W of cooling power at 83 K. 1 litre per hour of liquid nitrogen was successfully produced for every 100 W of cooling power at 83 K, in a commercial application. Three more 330 W pulse tubes have been mounted to a single 1000 cc DPWG to produce > 1 kW of cooling power at 77 K. The commercialisation of the 1000 W cryocooler is the topic of another paper presented at this conference. Details of the design, development, testing and integration of the 330 W cryocooler are presented in this paper.