A time-dependent analysis of crossed-field interaction has been formulated for computer calculation. The computer program has achieved, for the first time, accurate and complete simulation of the magnetron oscillator, magnetron amplifier, and smooth-bore magnetron. We believe that crossed-field interaction of the distributed-emission type is finally predictable. The computer results are reliable enough to serve as design information. They also indicate that the nature of the interaction is turbulent in the sense that the operation of these devices borders between order and disorder under certain conditions. The techniques used in this analysis are applicable to a wide range of problems dealing with other types of electron—wave interaction, and to plasmas.
Metastable noble gas atomic beam is widely used in atomic and molecular physics studies.Using radio-frequency discharge and transverse laser cooling, we produced a well-collimated intense meta-stable Krypton beam.Numerical simulation is also used to analyze the trajectories of atoms in an optic field produced by transverse cooling laser beams.The charactersisticl of the atomic beam are determined by measuring the laser induced fluorescence.The atomic beam flux measured at 230 cm downstream is 1.61016 atoms/(s*sr), which is enhanced by two orders of magnitude.The Kr atoms are finally trapped in a magneto-optic trap.A total of 1.31010 meta-stable 84Kr atoms can be simultaneously trapped with a loading rate of 3.01011 atoms/s.The same setup is also successfully used to obtain a bright metastable atomic argon beam and trap.
With the development of vacuum technology, subject to the influence of directional flow and uneven temperature, the thermodynamic equilibrium state is destroyed. In this case, the pressure reference is not suitable for characterizing the vacuum state. To ensure the long-term stability and reproducibility of the measurement system, vacuum metrology will be characterized by gas density. The precisive measurement of gas refractive index based on a Fabry-Perot cavity can be used to derive the gas density. This kind of an optical measurement of vacuum links macroscopic dielectric constants of gases with microscopic polarization parameters of atoms and molecules. It replaces the physical standard based on the mercury pressure gauge with the quantum standard. In this paper, we discuss the reverse process from refractive index to gas pressure, and use the laser-locked Fabry-Perot cavity method to measure the refractive index of argon gas. The contribution of related parameters to the uncertainty of determined gas pressure is analyzed. The influences of material parameters and experimental parameters such as gas molar susceptibility, molar susceptibility, dielectric second Virial coefficient and temperature on gas pressure accuracy are analyzed. The result shows that the uncertainty in our measurement of argon within 1 atm is <inline-formula><tex-math id="M2">\begin{document}$u = \sqrt {{{(6\;{\rm{mPa}})}^2} + {{(73 \times {{10}^{ - 6}}p)}^2}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20200706_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20200706_M2.png"/></alternatives></inline-formula>. Currently, the uncertainty mainly comes from the measurement deviation of gas temperature inside the cavity. After repeating the measurement a few times, the results show that the statistical uncertainty of refractive index is within 100 ppm, which is limited by the accuracy of the pressure gauge used here. In addition, we compare the dipole calculated by the <i>ab initio</i> method with that by the DOSD method. The results show that the dynamic polarizability obtained by the <i>ab initio</i> method is consistent with our experimental results. In conclusion, these experimental results show that the measurement of gas pressure based on the gas refractive index has high repeatability and accuracy. If the temperature control and corresponding measurement accuracy of the gas are further improved, this method can also be used to obtain high-precision microscopic parameters such as the polarizabilities of atoms and molecules. In the future work, we will focus on improving the temperature control and the design of the cavity to reduce cavity leakage and deflation. It is possible that the measurement accuracy of the gas pressure will be increased to 10 ppm level, which is the same level as the current standard pressure gauge and will become a new standard for pressure measurement in the future.
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