Research On Magnetron-injected-gun Of Terahertz Gyrotron Applied To Enhanced Nuclear Magnetic Resonance

Nuclear magnetic resonance(NMR)plays an important role in many scientific fields,which is widely used as a detection method in the fields of biology,medicine,physics,chemistry,geology and materials science and so on.In the national development plan,China has proposed the development of high-performance medical devices such as superconducting magnetic resonance imaging systems,non-invasive ventilator and nuclear medical imaging equipment.It is enough to see that nuclear magnetic resonance has become an important development direction related to national economy and people's livelihood.The dynamic nuclear polarization nuclear magnetic resonance(DNP-NMR)technology based on terahertz(THz)gyrotron can increase the sensitivity of NMR spectrum to several orders of magnitude,which is of great significance for the development of new generation of medical technology.Terahertz gyrotron is a fast wave device,which is excited by cyclotron stimulated radiation of electron in the longitudinal magnetic field.The wavelength does not limit the size of the device.The electromagnetic wave output can achieve requirements of high power and high frequency,which is in line with the DNP-NMR system Source requirements.As a key part of the gyrotron,the performance of the magnetron-injected electron gun(MIG)directly determines the performance of the gyrotron.When the magnetron-injected electron gun produces a suitable speed ratio and low velocity speed electron injection,the output power and efficiency of the terahertz gyrotron can be improved.In order to study the electron gun system of the terahertz gyrotron and improve its performance,the main contents of this paper are as follows:1.By deriving and simplifying the Maxwell's equations of electromagnetic field,electrostatic field and static magnetic field,electron motion and trajectory equations,the theoretical knowledge and calculation methods of electro-optics are obtained.2.The basic theory of magnetron-injection electron gun is studied in detail.The design idea of magnetron electron gun and the design flowchart are summarized.According to the performance requirements of gyrotron,a 0.46 THz dual-anode magnetron injection gun is designed to study the working voltage and magnetic field of gyrotron.The effect of intensity on the performance of the electron gun.3.According to the performance requirement and mode selection of the MIG,the two magnetron injection guns with 0.42 THz and 0.263 THz terahertz gyrotrons were successfully designed by electron gun particle simulation software Magic and CST.4.Through studying control anode voltage,structure of electron gun and other factors,the speed ratio and velocity spread of electron gun to produce electron beam are analyzed.The analysis results and reasons lead to the methods and conclusions of improving electron gun design and improving electron gun performance.