Recently, a joint project between HFCIM and the Institute of Plasma Physics, Chinese Academy of Sciences achieved a successful test of a 90-degree superconducting dipole magnet, marking the first large-scale saddle-shaped superconducting dipole magnet in China to utilize supercritical helium external cooling. The project team innovatively designed a low-temperature system using supercritical helium forced one-way circulation for external cooling, laying the foundation for the development of small-scale low-temperature helium gas circulation independent systems. This ensures the low-temperature stability of the superconducting dipole magnet during rotation, achieving fast cooling under high vacuum, cost-effective rotation, and rapid and versatile excitation functions.

fig.1 Superconducting Dipole Magnet Low-Temperature Test Data

The supercritical helium forced one-way circulation external cooling low-temperature system exhibits significant advantages by ensuring there is no helium accumulation in the cooling channels. Additionally, the choice of operating temperature is not restricted by the helium boiling point. This design prevents the generation of large amounts of helium during magnet quenching, eliminating the pressure safety hazards associated with a significant increase in internal pressure within the coil box during the rotation of a liquid helium-immersed superconducting magnet. As a result, the operational stability of the superconducting dipole magnet is greatly enhanced.

fig2. (a)Testing Site (b)Superconducting Coil

fig.3 3-D Diagram of Superconducting Rotational Gantry System 

Currently, the 90-degree superconducting dipole magnet is used in the rotation gantry system of proton therapy devices. Its successful development enables a 46% reduction in the overall weight of the rotation gantry and a 40% reduction in the overall external dimensions. This achievement plays a significant role in promoting the lightweight and miniaturization of the rotation gantry system, and the successful experience gained can be applied not only to the development of proton medical devices but also holds crucial application value in areas such as synchrotrons.

Based upon the successful development of the 90-degree superconducting dipole magnet, HFCIM team will further advance the engineering technology of superconducting dipole magnets. This progress aims to pave the way for capturing the international market in high-end medical devices and promoting the industrial development of advanced and compact proton therapy devices, thereby accumulating the necessary technological foundation for the future.