Yuanzineng kexue jishu (Sep 2023)
Simulation of Electromagnetic Performance of Pick-up Coil Based on Metallic Magnetic Calorimetry
Abstract
Metallic magnetic calorimetry holds significant promise in critical defense applications such as nuclear proliferation prevention, radionuclide classification, nuclear safety and anti-terrorism. Metallic magnetic calorimetry realizes energy resolution in the order of a few electron Volts by utilizing the significant contribution of heat capacity of a magnetic origin at milli-Kelvin temperatures in rare-earth doped Au films. For detecting gamma-ray photons with an energy of around 100 keV, the energy resolution is better than 0.1%, 10 times better than the high-purity germanium (HPGe) gamma spectrometer with the highest energy resolution. The metallic magnetic calorimeter can detect other radiation types than gamma rays such as alpha and beta emissions. Metallic magnetic calorimetry can also be used for precise measurement of astrophysical phenomena, cosmic rays and other high-energy physics phenomena. As an critical part of the metallic magnetic calorimeter, the pick-up coil plays a dual role in the sensor unit. It is not only responsible for converting magnetic flux changes into electrical signals, which is subsequently picked up by the SQUID chip, but also responsible for generating persistent excitation magnetic field and magnetizing the rare-earth doped sensor thin-film. The design configuration and electromagnetic parameters of pick-up coil can directly influence the energy resolution of the sensor. In the paper the influences of various parameters (e.g., number of turns of soil, duty ratio) on the electromagnetic characteristics using the finite element method was calculated. The actual pick-up coil size is in the order of micrometers. As direct measurement of such tiny devices is extremely difficult with conventional means and such measurements suffer high errors, in this paper scaled-up samples were measured, and the validity of the simulation model and parameters through comparison with measurement results was verified to provide a reliable foundation for design work of pick-up coils. The calculation results show that the influence of turn number of pick-up meander coil on inductance is more significant than other parameters such as duty ratio and loop pitch. With the increase of the duty ratio, the inductance shows a monotonic decrease trend. When the duty ratio increases from 30% to 70%, the inductance decreases by about 76.4%. On the other hand, with the increase of the turn number, the inductance shows an obvious increasing trend. When the turn number increases from 15 to 75, the inductance increases by about 253%. The simulation result also reveals the magnetic field distribution inside the metal magnetic calorimeter sensor pick-up coil, which provides critical information for the design of the sensor thin film.
