Microwave power coupling with electron cyclotron resonance plasma using Langmuir probe

Electron cyclotron resonance (ECR) plasma was produced at 2.45 GHz using 200–750 W microwave power. The plasma was produced from argon gas at a pressure of 2 × 10^???4 mbar. Three water-cooled solenoid coils were used to satisfy the ECR resonant conditions inside the plasma chamber. The basic parameters of plasma, such as electron density, electron temperature, floating potential, and plasma potential, were evaluated using the current–voltage curve using a Langmuir probe. The effect of microwave power coupling to the plasma was studied by varying the microwave power. It was observed that the optimum coupling to the plasma was obtained for ~ 600 W microwave power with an average electron density of ~ 6 × 10¹¹ cm^???3 and average electron temperature of ~ 9 eV.     

高工作比热阴极微波电子枪调试出束

 报导了一种采用新型结构热阴极4+1/2腔微波电子枪的设计思想、束流动力学计算和调试结果。在微波功率3.2MW时,获得宏脉冲电流1A,电子束脉宽5μs,重复频率200Hz,平均束流功率1~ 2kW,束流稳定,工作比高达10^-3。     

On Transient Time Reduction of a 2.4 GHz Relativistic Traveling Wave Oscillator with a Hollow Slow Wave System

The decrease in the transient time in a relativistic microwave traveling wave oscillator, in which the interaction is carried out between the relativistic electron beam and the fundamental harmonic of the forward-traveling electromagnetic wave slowed down to the speed of light in the hollow slow wave system system, has been numerically and experimentally demonstrated. It is shown that in this mode a high beam-to-wave coupling impedance up to ≈10 Ω is achieved, which ensures reduction of the transient time. In the experiment, a microwave peak power of 210 ± 30 MW at a frequency of 2.45 GHz in a guiding magnetic field of 0.16 T was obtained. The efficiency of the oscillator to convert the power of the electron beam into microwave power was 17 ± 3%. At the beam current pulse duration of about 50 ns the microwave pulse duration was about 20 ns and the transient time was about 22 ns.

     

一种非连续微波探询信号的实现

铷原子频标（RAFS）的微波探询信号可用于激励铷原子产生基态能级之间的跃迁,从而实现共振探测.目前常用的微波产生方案都存在电路结构复杂、功耗大、不便于集成的缺点.本文提出了一种利用锁相环（PLL）技术产生非连续微波探询信号的设计方案,这种方案以10 MHz信号作为参考频率,在单片机的合理配置下可直接得到（6 834.687 5 MHz±f_M）信号（f_M表示最大频偏）.该方案具有电路结构简单、功耗低、数字化程度高等优点,利用该方案实现的整机稳定度优于1.5E-11/√τ（1 s≤τ≤100 s）,性能指标均可满足小型商业铷原子钟要求.     

Thermoacoustic Method for Detection of Powerful Microwave Pulses

We propose a method for detection of the envelope of a microwave nanosecond pulse, which is based on the effect of generation of sound pulses resulting from absorption of electromagnetic waves. We show that to reproduce exactly the envelope shape of a short microwave pulse, it is necessary that the wave be absorbed in a layer of thickness much less than the product of the sound speed and the pulse duration. In searching for conditions ensuring this, we study the process of thermoacoustic generation in thin metal films deposited on quartz substrates. Measurements performed at a wavelength of 8 mm show that the absorption coefficient is maximum if the aluminum-film thickness is 22–25 Å. The maximum absorption coefficient amounts to 49% if the wave is incident from the quartz-substrate side. It is important that in this case, the wave reflection coefficient does not exceed 44%, whereas an aluminum plate reflects almost completely (99.8%) the incident-wave power. The phenomena observed in thin metal films are explained theoretically in terms of the anomalous skin effect. An experimental setup for a study of generation of ultrasonic signals by powerful microwave pulses is described.     

Optimal Microwave Radiation Field Parameters for Mercury Ion Microwave Frequency Standards

We propose a method to determine the optimal power of the microwave resonance transition that simultaneously improves the signal-to-noise ratio and reduces line width based on saturation broadening theory and experiment.Saturation broadening spectra of the ground state hyperfine transition of trapped ~(199)Hg~+ ions are measured and analyzed.The value of the optimal microwave power is obtained by using the proposed method and is verified.Rabi oscillations decay spectra of trapped ~(199)Hg~+ ions are observed and the optimal microwave irradiation time for the maximum transition signal intensity is determined.This work will help to improve the short-term frequency stability of the mercury ion microwave frequency standard.     

锥形慢波结构波导谐振腔微波发生器

 利用二维半的PIC等离子体物理程序设计了一种新的结构简单、体积小、重量轻、频率稳定的高功率、高效率的微波器件。此器件采用了锥形慢波结构波导谐振腔,不用外加引导磁场。微波频率可以设计为f=1.6 ~12GHz,功率P_out可达GW。     

Microwave generation by a self-sustained current oscillation in an InGaAs/InAlAs superlattice

We observed a self-sustained current oscillation in an InGaAs/InAlAs superlattice at room temperature. The oscillation gave rise to microwave generation at a fundamental frequency around 2 GHz and higher harmonics. The power at the first harmonic was 0.1 mW, corresponding to an efficiency (i.e. ratio of microwave power to dc power) of 3.5%. We attribute the current oscillation to travelling dipole domains.     

Relativistic backward-wave tube with mechanically tunable generation frequency over a 14% range

A tunable-frequency low-magnetic-field relativistic microwave oscillator is realized experimentally based on a relativistic backward-wave tube with a modulating resonance reflector. The generated frequency is tuned mechanically by moving the oscillator slow-wave structure relative to the reflector. At fixed parameters of the corrugations and of the electron bunch, a frequency tuning range of about 14% measured between −3-dB (relative to the maximum peak generated microwave power) points is realized. The maximum pulse power of 3.4 ± 0.7 GW was obtained at a carrier frequency of 3.65 GHz in a magnetic field of 0.44 T.     

Microwave spectrum of nitroxyl

The microwave spectrum of HNO has been observed and analyzed. Both a-type and b-type transitions have been measured. The rotational constants obtained are A = 553903.0 ± 2.7 MHz, B = 42308.52 ± 0.10 MHz, and C = 39169.46 ± 0.10 MHz. In the analysis of the spectrum, centrifugal distortion corrections are tentatively taken into account by using the centrifugal distortion constants determined by Dalby. The quadrupole coupling constants for nitrogen in HNO are determined to be χ_aa = 0.36 ± 0.56 MHz, χ_bb = ? 5.46 ± 0.30 MHz, and χ_cc = 5.10 ± 0.26 MHz. The dipole moment and its components determined from the Stark effect measurement are μ_total = 1.67 ± 0.03 D, μ_a = 1.03 ± 0.01 D, and μ_b = 1.31 ± 0.02 D. The microwave spectrum of DNO has been reanalyzed by taking into account the centrifugal distortion effect. The inertia defects for HNO and DNO have been calculated. The results are limited in precision by the lack of reliable force constants.     

Microwave oscillator based on Bloch oscillations of electrons in a semiconductor superlattice

We report on a microwave oscillator based on Bloch oscillations of electrons in a semiconductor superlattice. Our GaAs/AlAs superlattice, at room temperature, was coupled electromagnetically by an antenna to a rectangular cavity resonator, and was operated at a current-voltage state of negative differential conductance. We observed generation of microwave radiation at frequencies, depending on the resonator length, between 7 and 30 GHz. Electronic tuning by several percent was possible; the ratio of linewidth to frequency was of the order of 10^?4. A radiation power up to 1 μW (at 10 GHz) was obtained, corresponding to a generator efficiency of the order of 10^?3 for the conversion of electrical power to microwave radiation.     

基于可调光延迟线的光子学微波频率测量

提出了一种基于可调光延迟线的光子学微波频率测量方法.经同一微波信号调制的两个不同波长光载波在经过一段可调色散介质传输后,解调输出两路具有不同相位的微波信号,得到的相干微波功率随着色散量的改变出现周期性变化,由此周期可得到输入微波频率值.采用由8个磁光开关和1.6 km单模光纤构成的7-bit光纤延迟线实现色散量的调节....     

Microwave spectrum and dipole moment of pentafluorobenzene

With the idea of evaluating the dipole moment of pentafluorobenzene from a lowJ transition, its microwave spectrum was investigated in the frequency region of 8,000 to 12,400 MHz. The spectrum had been earlier observed by the authors in the 12,400 to 18,000 MHz region which needs reassignment in the light of present investigations. The rotational constants areA=1480·856±0·003 MHz,B=1030·066±0·003 MHz andC=607·496±0·002 MHz. The dipole moment is 1·44±0·05 D.     

Microwave spectrum of tropone

The microwave spectrum of tropone (2,4,6-cycloheptatriene-1-one) has been obtained and assigned. The observation of a statistical weight intensity alternation indicates that the molecule has C_2v symmetry. Relative intensity measurements show the molecule to possess a low wavenumber vibration whose 1-0 interval is 60 ± 20 cm^?1. The dipole moment is found to be 4.1 ± 0.3 D by the “rate-of-growth” method.     

Microwave generation using a superluminal source

The power produced by existing sources of microwave radiation falls off with decreasing wavelength. To solve this problem a new concept is proposed for generating microwave radiation, based on the use of a superluminal source formed when electrons are emitted into vacuum from a medium and the emission front propagates along the surface with a speed greater than that of light. Such generators are shown to have a number of completely unique properties: they radiate extremely short pulses (as short as picoseconds); their power exceeds that of existing sources by orders of magnitude; and unlike existing sources, it increases as the wavelength is reduced. Zh. éksp. Teor. Fiz. 115, 1689–1707 (May 1999)     

Microwave spectrum of gauche-isopropylphosphine

The microwave spectra of isopropylphosphine has been recorded in the region 12.4–40.0 GHz. Both a- and b-type transitions were observed and assigned. The rigid rotor rotational constants were determined to be A = 7633.34 ± 0.09, B = 4243.36 ± 0.02, and C = 3045.84 ± 0.02 MHz for (CH₃)₂CHPH₂ and A = 7226.47 ± 0.05, B = 4041.06 ± 0.02, and C = 2946.85 ± 0.02 MHz for (CH₃)₂CHPD₂. Dipole moment components of |μ_a| = 1.15 ± 0.01, |μ_b| = 0.43 ± 0.01, |μ_c| = 0.03 ± 0.02 and |μ_t| = 1.23 ± 0.01 were determined from the Stark effect. From the microwave spectra, the Stark effect and the experimental rotational constants, the assigned spectrum has been identified to result from the gauche form and this conformer is believed to be more stable than the other form which is present at room temperature.     

Microwave spectrum and substitution structure of methylene chloride

The microwave spectrum of methylene chloride has been reinvestigated in order to obtain a complete substitution (r_s) structure of well-defined precision. Measurements on the ¹³CH₂Cl₂ species have yielded the following rigid-rotor rotational constants: A = 30746.20 ± 0.10 MHz, B = 3320.63 ± 0.11 MHz, and C = 3053.44 ± 0.10 MHz. These data, combined with revised values reported earlier for other isotopic species, yields the following r_s structural parameters: CCl = 1.767 ± 0.002 Å, CH = 1.085 ± 0.002 Å, ∠HCH = 112.1 ± 0.2°, and ∠ClCCl = 112.2 ± 0.1°.     

Harmonic Generation of High-Power Microwave in Plasma Filled Waveguide

The harmonic generation of high power microwave in plasma filled waveguide is studied and the analytical theory is presented, and the numerical calculation and analysis of second harmonic are done in this paper. The theoretical and numerical analysis show that high power microwave can generate harmonic in the plasma filled waveguide.     

第四代ECR离子源的主要概念(摘要)

To go beyond the present and planned third generation ECR ion sources operating at microwave frequencies between 20 and 30GHz to a fourth generation of sources operating above 50GHz offers new oppor- tunities and challenges.Based on the experimentally demonstrated frequency scaling,a doubling in operating frequency could provide more intense high charge state beams with higher charge states.The technical chal- lenges include the development of magnetic structures capable of producing 8T solenoid field and 4T sextupole fields,production and coupling of high power microwave power to heat the plasma,extraction of intense mul- tiple charge ion beams from a region of strong magnetic field and shielding of bremstrahlung from the hot electrons.In this paper,the status of high field superconducting magnets now under development for acceler- ator applications,gyrotrons for microwave power and other technical aspects that would be incorporated into a fourth generation ECR ion source are explored and applied to a conceptual design.     

Microwave spectrum of dimethyldichlorosilane

The microwave spectrum of dimethyldichlorosilane has been observed and the rotational constants and centrifugal distortion constants have been determined for ³⁵Cl₂ and ³⁵Cl³⁷Cl species. From these constants, the molecular structure is determined as $\text{r(}\text{SiCl}\text{) = 2.055 ± 0.003}\text{A}\text{?}$, $\text{r(}\text{SiC}\text{) = 1.845 ± 0.005}\text{A}\text{?}$, ∠ClSiCl = 107.2 ± 0.3°, ∠CSiC = 114.7 ± 0.3°. An analysis of the ³⁵Cl₂ quadrupole splittings leads to quadrupole coupling constants of χ_aa = ?19.6 ± 0.3 MHz, χ_bb = ?3.7 ± 1.4 MHz, χ_cc = 23.3 ± 1.4 MHz, χ_bond = ?38.0 ± 1.6 MHz, and η_bond = 0.22 ± 0.08.