A Single-Ridged Coaxial Hybrid TE011 Coupler with High Mode Purity

We design a single-ridged coaxial hybrid coupler which excites a TE₀₁₁ mode of high mode content in a cylindrical cavity, resonating at 28.2GHz. The coupler consists of a WR-28 rectangular waveguide, a coaxial TE_n11 cavity, and a cylindrical TE₀₁₁ cavity. Both TE₃₁₁ coaxial cavity and TE₄₁₁ single-ridged coaxial cavity are analyzed to examine the TE₀₁₁ mode purity in the central cavity. Mode purity analysis is performed by a field expansion method using Fourier-Bessel orthonormal basis functions. Numerical calculations predict that the TE₄₁₁ single-ridged coaxial cavity excites the TE₀₁₁ mode with mode purity of 98.6%, which is improved by 3% higher compared with the TE₃₁₁ coaxial cavity. Measurements on the single-ridged coaxial coupler show a resonant frequency at 28.078GHz and ohmic and external Qs of 1560, 473 respectively, which are in good agreement with the simulated results of a 3-D finite element electromagnetic code.     

Experimental Study of a Slot Antenna Excited by a TE011 Mode Coaxial Cavity

A slot antenna is developed to excite the high harmonic waveguide mode for generating large-area plasmas. This antenna consists of a TE₀₁₁ mode coaxial cavity with the axial slots positioned on equal interval on the inner wall. The waves radiated from those slots can excite the high harmonic mode in the central area. With the azimuthal symmetric wave field of the TE₀₁₁ mode, the number of the slots can be chosen to match the field pattern of the high harmonic mode. In this report, the dispersion relation of the coaxial waveguide, the coupling scheme and the mode competition of the cavity are studied. A method has been successfully developed to suppress the TE₁₂₁ mode which is the most competing mode to the TE₀₁₁ mode.     

Mode selective directional couplers for overmoded waveguide systems

Two types of directional couplers for transverse electric (TE) modes are described: short and multihole couplers, respectively. They selectively pick one mode out of a mode mixture in an overmoded circular waveguide system. Unwanted modes are either statistically kept at low level or are suppressed by destructive interference in the coupling waveguide. Mode selectivity and directivity in multihole couplers oscillate up and down with an increasing number of holes, finally reaching a minimum of approximately 20 dB, unless there are competing modes with rational fractions of the beat wavelength. A multihole coupler for the TE₀₂ mode (28 GHz, 63.4 mm waveguide diameter, 41 holes) and a length of 1.6 m shows a calculated directivity of 68 dB and suppresses the unwanted modes TE₀₁ with 34 dB (24 dB), TE₂₂ with 37 dB (45 dB), and further modes TE_m (<5, m<6) with 17 dB to 34 dB in forward direction (figures in parentheses are for unwanted modes propagating in backward direction).A short directional coupler for the TE₀₁ mode (28 GHz, 63.4 mm waveguide diameter) with 16 holes and a length of 230 mm shows a directivity of 55 to 100 dB between 27.9 and 28.1 GHz, suppressing the TE₀₂ mode with 35 to 80 dB, the TE₀₃ mode with 30 to 65 dB, and the TE₂₂ mode with 30 to 70 dB.     

矩形波导与圆柱波导或圆柱谐振腔间的小孔耦合

本文讨论了三种不同系统的小孔耦合的近似解法:矩形波导与圆柱波导的同轴耦合,矩形波导中的TE₁₀型波与圆柱谐振腔中的TM₁₂₀型波间的耦合和矩形波导中的TE₁₀型波与圆柱波导中的TM_mn型波间的耦合。通过这几个问题的解法,我们希望读者可以看到处理复杂微波元件问题时所需的从物理概念出发的灵活应用已有方法的必要性。这里提供的几个公式有着广泛的应用范围而是在现有文献中探讨得不够的。这里介绍的方法可以应用到其他新的微波网络问题中去。     

Ultra-compact multimode interference InGaAsP multiple quantum well modulator

We propose a new structure for an ultra-compact multimode interference (MMI) InGaAsP multiple quantum well modulator. The operating principle is based on restricting the coupling of the self-image produced by the MMI region into a single mode output waveguide. The key is to excite only the even modes within the MMI region, and this is achieved by operating the MMI waveguide under the condition of restricted symmetric interference. By asymmetrically inducing a phase change of along a selected area within the MMI region, mode conversion of all the even modes to odd modes is achieved. Since only the fundamental mode can be coupled to the output waveguide, neither an individual mode, nor any combination of the modes will be coupled, and therefore the injected light is fully attenuated. The modulation characteristics are analyzed using the finite-difference beam propagation method. Extinction ratios as low as –37 dB are demonstrated without electro-absorption effects. For the case of low electro-absorption, which corresponds to a more realistic situation, this value is only increased to –35 dB.     

A dielectric rod waveguide coupled with metal rectangular waveguide

Measurements have been done in the millimeter wave region on a composite waveguide which comprises a dielectric rod waveguide connecting two metal rectangular waveguides. Such a waveguide has been used by us in a Josephson harmonic mixer installed in a small metal cryostat, to prevent the thermal invasion from outside environment and to transmit both signal and LO waves with small losses. The measured transmission loss, that is caused mainly by the coupling loss between metal rectangular waveguides (TE₁₀ mode) and a dielectric rod waveguide (HE₁₁ mode), has been less than 2dB in the frequency range of 52–104 GHz.     

Measurement of the πmeson polarizabilities via the γp → γπ+n reaction

An experiment on the radiative ^{+}-meson photoproduction from the proton ( p ^{+}n) was carried out at the Mainz Microtron MAMI in the kinematic region 537MeV < E < 817MeV, 140^° 180^°. The ^{+}-meson polarizabilities have been determined from a comparison of the data with the predictions of two different theoretical models, the first one being based on an effective pole model with pseudoscalar coupling while the second one is based on diagrams describing both resonant and nonresonant contributions. The validity of the models has been verified by comparing the predictions with the present experimental data in the kinematic region where the pion polarizability contribution is negligible ( s₁ < 5m²) and where the difference between the predictions of the two models does not exceed 3%. In the region, where the pion polarizability contribution is substantial ( 5 < s₁/m² < 15, -12 < t/m² < - 2), the difference of the electric () and the magnetic () polarizabilities has been determined. As a result we find . This result is at variance with recent calculations in the framework of chiral perturbation theory.     

Hadronic coupling constants in lattice QCD

We calculate the hadronic coupling constantsg _NN andg in QCD, including dynamical quarks in the framework of staggered fermions in the lattice approach. For the nucleon-pion coupling we obtaing _NN =13.8±5.8, to be compared with the experimental value 13.13±0.07 [1]. The coupling has been analysed for two different sets of operators with the averaged resultg =4.2±1.9 which is to be compared with the experimental value 6.06±0.01 [2].     

The formation of pseudoscalar mesons in neutrino-lepton interactions

The paper considers the processes of formation of pseudoscalar mesons by the interaction of an antineutrino with a leptonv _ll K, , K.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 139–143, August, 1974.     

双微波源共轴辐射馈线结构的设计

设计了一种将两个不同波段微波源输出微波馈向同一个馈源喇叭的双波段馈线结构。该结构不仅对两个微波源输出的TM01模进行了有效的模式转换,而且实现了两个波段的微波共用辐射天线。采用双弯曲圆波导模式转换器实现高频段微波源输出微波的模式转换和轴线的定量平移;采用中间模式为矩形波导TE10模的圆波导TM01模-同轴波导TE11模的模式转换器,实现低频段微波源输出微波的模式转换及与高频段微波源输出微波的共轴输出。数值仿真结果验证了设计思路的正确性。     

On the sign of cos θ at the branch points of a partial wave amplitude in thes-plane

The sign of the cosine of the scattering angle, cos, at the branch points of a relativistic two-body partial wave amplitude with arbitrary masses in the complexs-plane is determined. The results yield that as to the tops-sheet, (i) the sign of cos is the same at the complex conjugated branch points which lie off the reals-axis, and (ii) cos changes sign at the (direct channel) thresholds. The difference between the elastic and inelastic cases is emphasized. It is pointed out that in certain physical energy ranges, for some collisions (e.g. + N + N), the directions near the backward direction can be considered as the most important ones, while for several other collisions (e.g. + N + N) the directions into the forward hemisphere have the strongest influence.The author would like to thank Professor G. Höhler for his kind hospitality at the Institut für theoretische Kernphysik, University of Karlsruhe. He is grateful to him and to the members of that Institute for valuable discussions. Correspondence with Dr. Jens Lyng Petersen, which gave rise to the present investigation, is also acknowledged.     

高功率微波在等离子体填充波导中的谐波产生

采用等离子体流体理论，研究了高功率微波在等离子体填充波导中的谐波产生，导出了非线性波动方程. 对二次谐波产生进行了数值计算与分析. 理论分析和数值计算表明，高功率微波将在等离子体填充波导中激发起谐波，TE_0n模式与TM_0n模式的基波都将激发起TM类型的谐波. 关键词： 高功率微波 谐波产生 等离子体填充波导     

Simultaneous two wavelength operation of an optically pumped HCOOH laser on orthogonally polarized modes

Simultaneous laser operation in orthogonally polarized EH₁₁ and TE₀₁ waveguide modes is reported for pairs of cascade lines from an optically pumped formic acid vapour laser incorporating a strip grating output coupler. Observations were made for the 394 m/406 m and 433 m/446 m cascade sequences, the resonator length being adjusted so that the laser was simultaneously resonant on a mode of the primary transition polarized perpendicular to the strips of the output coupler and the same transverse mode of the secondary transition polarized parallel to the coupler strips. Power measurements showed that for the laser configuration used in this study the power of the primary transition was increased only slightly when the cascade lines were simultaneously resonant, whereas the secondary line could only lase under these conditions.     

Uniform Field Re-entrant Cylindrical TE$$_{01\text {U}}$$ Cavity for Pulse Electron Paramagnetic Resonance Spectroscopy at Q-band

Uniform field (UF) resonators create a region-of-interest, where the sample volume receives a homogeneous microwave magnetic field (\(B_1\)) excitation. However, as the region-of-interest is increased, resonator efficiency is reduced. In this work, a new class of uniform field resonators is introduced: the uniform field re-entrant cylindrical TE\(_{\text {01U}}\) cavity. Here, a UF cylindrical TE\(_{\text {01U}}\) cavity is designed with re-entrant fins to increase the overall resonator efficiency to match the resonator efficiency maximum of a typical cylindrical TE\(_{011}\) cavity. The new UF re-entrant cylindrical TE\(_{\text {01U}}\) cavity is designed for Q-band (34 GHz) and is calculated to have the same electron paramagnetic resonance (EPR) signal intensity as a TE\(_{011}\) cavity, a 60% increase in average resonator efficiency \(\Lambda _\mathrm{ave}\) over the sample, and has a \(B_1\) profile that is 79.8% uniform over the entire sample volume (98% uniform over the region-of-interest). A new H-type T-junction waveguide coupler with inductive obstacles is introduced that increases the dynamic range of a movable short coupler while reducing the frequency shift by 43% during over-coupling. The resonator assembly is fabricated and tested both on the bench and with EPR experiments. This resonator provides a template to improve EPR spectroscopy for pulse experiments at high frequencies.     

Mode competition, suppression, and efficiency enhancement in overmoded gyrotron oscillators

Gyrotron oscillators are of great interest as sources of high power mm wave radiation for electron cyclotron resonance heating and current drive in magnetic fusion research devices. Gyrotrons capable of efficiently generating cw power 1 megawatt will be required in future magnetic fusion studies. However, as gyrotron power approaches the megawatt level, a very large, overmoded cavity must be employed in order to keep ohmic power losses in the cavity at an acceptable level, and the problem of mode overpopulation becomes severe. Also, it becomes increasingly important to optimize gyrotron efficiency for a number of important reasons including minimizing the problem of collecting the electron beam energy. In the present paper, a detailed experimental and theoretical study of mode competition and mode locking in an overmoded gyrotron is presented. Efficiency enhancement (to 60%) and high peak power (430 kW) were achieved in the TE_2,4,1 mode using magnetostatic profiling in the cavity. With selective mode suppression, peak power of 475 kW was generated in the TE_0,4,1 mode.This work was performed at the Naval Research Laboratory. Some of the authors have affiliations with other institutions, as indicated:     

A Mode Converter with Multi-waveguide Output from the TE01 Circular Waveguide Mode to the TE10 Rectangular Mode for Millimeter Wave Gyro-device Applications

A mode converter with multi-waveguide output for millimeter wave gyro-device applications is proposed in this article, which is used to convert the TE₀₁ circular waveguide mode into the TE₁₀ rectangular waveguide mode. Computer simulations with Ansoft HFSS code show that the energy transmission coefficient of larger than 95.96% may be reached in the frequency range from 34.094 GHz to 35.8 GHz (a bandwidth of 1.706 GHz) at a VSWR of lower than 1.5 for the input operating mode.     

Quantum correlations and three body decays at a ϕ factory

The decays of neutral kaons produced in decay, K _L K _S , exhibit interesting quantum mechanical interference. The effects of this phenomenon on searches for CP violation have been previously been worked out for two body decays where the decay amplitude is a simple constant. For three body modes where the matrix element varies across the kinematically allowed region, the quantum correlations with enhance or cancel certain terms in the decay distribution. We work out the results for two interesting modes ()() and (3)(3). In the former case, the quantum correlation allows the isolation of the direct emission component of the decay, while in the latter case the intensity asymmetry can uniquely pick out the direct CP violating amplitude.Research supported in part by the National Science Foundation     

Description of πp→Δ(1232)π and πp→Δ(1232)ρ(770) reaction proceeding via baryon exchange mechanism

We analyze the available experimental data on the backward production processes N and N in the framework of the strong-cut Reggeized absorption model, which is based on the exchange of the baryon Regge trajectoriesN and with the associated cuts. The model describes rather well the data on the differential cross sections at incident momenta ranging from 2.15 to 20 GeV/c. An essential contribution of exchange even at small energies (E _lab of the order of a few GeV) is found. A model-independent analysis of data confirms this fenomena.     

Intensity distribution in the rotational structure of the electron-vibrational bands of nitrogen

The intensity distribution was measured for the rotational lines of the N₂ molecule in the radiation of a glow discharge in the pure gas, at pressure 0.1–5 torr, or with argon, at a total pressure of 2 torr, at a current of 40 mA. The distribution found lags behind a Boltzmann distribution in the 0–3 band (corresponding to the C³-B³ transition; the second positive system) over the pressure range 0.1–2 torr and in the 1–4 band (the C³-B³ transition; second positive system) at a pressure of 0.1 torr. In the N₂ + Ar mixture there is selective amplification of the J=25, 26 rotational lines.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 17–21, September, 1970.     

Backward production of mesons associated withΔ ++(1232) inπ + p interactions at 20 GeV/c

We have analyzed backward meson production in ⁺ p reactions at 20GeV/c, which were measured in the CERN spectrometer triggered by a fast proton (p _f ), in experiment WA56. Production via baryon exchange of quasi-two-body final states ⁺⁺ (1232) ⁰ (770), ⁺⁺ (1232)f ₂ (1270), and ⁺⁺ (1232) ₃ ⁰ (1690) is clearly identified. The density matrix elements of meson resonances and of ⁺⁺ (1232) are analyzed. We have observed also the reactions ⁺ p ⁺⁺ (1232) ⁰ and ⁺ p ⁺⁺ (1232) in thep _f ^{+ 0} andp _f ^{+ + – 0} final states.