On December 18, 2023, the local helicity injection system for the Honghuang 70 high-temperature superconducting tokamak device was tested successfully. The local helicity injection system, also known as an electron gun, is a type of vacuum electronic device that operates by applying a high voltage between the anode and cathode to ionize the gas and generate electrons, which are then focused into a beam and injected into the tokamak device.
In the Honghuang 70 device, the electron gun's primary function is to pre-ionize the gas to assist in gas breakdown. Additionally, it can inject helical magnetic flux into the plasma through the electron beam to excite a higher plasma current for the purpose of current drive. Compared to traditional thermionic emission electron guns, the Honghuang 70 electron gun features a cold cathode design, which is more compact and conducive to focusing electrons and increasing the extracted current. It also avoids impurity issues associated with heating filaments.
The electron gun was designed and developed by Energy Singularity and incorporates innovative structural design. It is only the size of a shoebox, with all key components being detachable. It can achieve a maximum extracted current of 1000A and a breakdown voltage of 8kV, and has been granted invention patent authorization.