Design considerations for the gyro-peniotron oscillator

The gyro-peniotron shows great promise as a source of microwave radiation. In this paper we investigate the stability and the non-linear saturated efficiency of a gyropeniotron oscillatro with an axis encircling beam operating at the TE₂₁₁ and the TE₃₁₁ cylindrical cavity modes. Beam and cavity parameters for stable high efficiency operation are presented from a linear theory analysis of the start-oscillation condition. Using design parameters taken from the linear analysis, the strong field non-linear emission efficiencies are studied numerically. The sensitivity of the saturated efficiency to beam axial velocity and guiding center spread is also considered. The results of our modeling indicate that high efficiency (70–90%) operation of the gyro-peniotron oscillator is possible, even with large guiding center and large axial velocity spread.This work was supported by the University of California at Los Angeles under Contract 400093 through the U.S. Army Research Office Contract ARO-DAAG 29-82-K-0004.     

Development of IR-FEL facility for energy science in Kyoto University

A mid-infrared free electron laser (FEL) has been constructed for energy science in the Institute of Advanced Energy, Kyoto University. The FEL system consists of a compact S-band Linac and an undulator to generate 4–13 μm coherent mid-infrared radiations. The Linac consists of a 4.5 cell rf gun with a thermionic cathode and a 3-m traveling-wave-type accelerator tube fed by 10 MW and 20 MW rf power, respectively. We have succeeded to produce 40 MeV, 40 mA and 3 μs electron beams. Last December, the 9.2 μm spontaneous emission from the undulator generated by 29.5 MeV electron beams was observed for the first time. Further optimization parameters of both the electron beam and the optical cavity are being pursued for an FEL lasing in the near future.     

混合型波荡器的3维优化

以波荡器辐射波和共振电子能及混合型波荡器的解析计算为基础,通过3维磁场的有限元计算,在欧洲光源横向优化基础上,给出了同步辐射和自由电子激光用混合型波荡器纵向优化参数,进而给出了用于DUV FEL混合型波荡器的设计计算参数。加侧位和顶部永磁块后,峰值磁场分别提高到0.722T和0.773T,辅助以1μm量级分辨率的磁间隙调节机械系统,磁场分辨率好于10-4T量级。     

混合型波荡器的3维优化

 以波荡器辐射波和共振电子能及混合型波荡器的解析计算为基础，通过3维磁场的有限元计算，在欧洲光源横向优化基础上，给出了同步辐射和自由电子激光用混合型波荡器纵向优化参数，进而给出了用于DUV FEL混合型波荡器的设计计算参数。加侧位和顶部永磁块后，峰值磁场分别提高到0.722T和0.773T，辅助以1μm量级分辨率的磁间隙调节机械系统，磁场分辨率好于10^-4T量级。     

Efficient design considerations for end-pumped solid-state-lasers

The temperature distribution in the gain medium and key design parameters for an ideal-four level end-pumped solid-state laser have been analyzed depending on the crystal's length, absorption coefficient, and pump beam M² factor. The optimum key design parameters and thermal focal lens are obtained by minimizing the root mean square of pump beam radius in the laser crystal. It is found that the focal thermal lens and key design parameters are dependent on the gain medium characteristics and pump beam properties as well. By considering the Poisson equation in cylindrical coordinate and Top-Hat pumping profile, an analytical formula has been derived to introduce the thermal focal length in the end-pumped lasers. A formula is also presented to relate the requirements of pump source to the gain medium properties for working laser at the design point.     

PKU-FEL设计的初步考虑

北京大学在其超导加速器装置PKU-SCAF的基础上将建成一个红外自由电子激光实验平台PKU-FEL。它可以提供高稳定度、高平均功率、高谱纯度、ps脉冲的自由电子激光。给出了PKU-FEL的初步设计方案。     

PKU-FEL设计的初步考虑

 北京大学在其超导加速器装置PKU-SCAF的基础上将建成一个红外自由电子激光实验平台PKU-FEL。它可以提供高稳定度、高平均功率、高谱纯度、ps脉冲的自由电子激光。给出了PKU-FEL的初步设计方案。     

Diagonal vibrational matrix elements for an anharmonic oscillator

General expressions for the diagonal rotationless matrix elements of any power of the internuclear displacement from equilibrium are obtained for ¹Σ-state diatomic molecule using an iterative relation. These expressions, including contributions arising from terms of the ninth power in the Dunham potential, are obtained in analytical form. As an application, sixth- and seventh-order contributions to the matrix element 〈0?x¹?〉 are calculated for the first eight powers of the displacement.     

On perturbation theory for an asymmetric anharmonic oscillator

A modified perturbation theory is formulated for an asymmetric anharmonic oscillator based on a choice of the main approximation constructed by analogy with the self-consistent field model. This perturbation theory has a much wider range of application in comparison with the standard approach and considers a finite number of energy levels in the potential well already in the main approximation. This approach is used for the construction of a two-atomic model of a quantum crystal. A quantum analog of the Lindeman criterion is obtained. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 30–40, January, 2009.     

On the Wigner distribution function for an oscillator

We present two new derivations of the Wigner distribution function for a simple harmonic oscillator Hamiltonian. Both methods are facilitated using a formula which expresses the Wigner function as a simple trace. The first method of derivation then utilizes a modification of a theorem due to Messiah. An alternative procedure makes use of the coherent state representation of an oscillator. The Wigner distribution function gives a semiclassical joint probability for finding the system with given coordinates and momenta, and the joint probability is factorable for the special case of an oscillator. An important application of this result occurs in the theory of nuclear fission for calculating the probability distributions for the masses, kinetic energies, and vibrational energies of the fission fragments at infinite separation.     

磁绝缘线振荡器的自动优化设计

为克服全电磁粒子模拟(PIC)程序不利于优化设计的弱点, 提高高功率微波器件的优化设计水平, 将遗传算法与全电磁粒子模拟算法有机融合, 研制出二维全电磁粒子模拟并行优化程序。据此对高功率微波源器件两个波段的磁绝缘线振荡器（MILO）：C-MILO和L-MILO进行优化设计。在输入功率不变的条件下, 原C-MILO效率为10.8%, 经优化后效率为15.4%; 原L-MILO效率为12.6%, 经优化后效率为17.7%。由此得出, 两类MILO模型经优化后在输入功率基本不变的情况下输出功率和效率都有很大程度的提高, 且模型几何参数合理, 物理图像正确。     

磁绝缘线振荡器的自动优化设计

为克服全电磁粒子模拟(PIC)程序不利于优化设计的弱点,提高高功率微波器件的优化设计水平,将遗传算法与全电磁粒子模拟算法有机融合,研制出二维全电磁粒子模拟并行优化程序。据此对高功率微波源器件——两个波段的磁绝缘线振荡器(MILO):C-MILO和L-MILO进行优化设计。在输入功率不变的条件下,原C-MILO效率为10.8%,经优化后效率为15.4%;原L-MILO效率为12.6%,经优化后效率为17.7%。由此得出,两类MILO模型经优化后在输入功率基本不变的情况下输出功率和效率都有很大程度的提高,且模型几何参数合理,物理图像正确。     

Picosecond laser oscillator with a cavity design for stable CW mode-locking operation

A detailed design of a picosecond laser oscillator is made by using optical resonance theory and semiconductor saturable absorber mirror continuous wave mode-locked technology. Mode parameters in the optical resonance including beam sizes on the laser crystal and mode locker are calculated. By theoretical calculations, 3.7 W output power is obtained at a pump power of 11 W and the optical to optical efficiency is 34% in the designed model of picosecond laser. Based on the detailed design, an experiment is proceeded and a picosecond laser oscillator of about 3.5 W output power with 10.6 W pump power is fabricated. The optical to optical efficiency of the laser is 33%, the pulse duration is about 20 ps, and the repetition rate is about 80.3 MHz. The oscillator presents long-term stability in the experiment.     

A proposal for an X-ray free-electron laser oscillator with an energy-recovery linac

We show that a free-electron laser oscillator generating x rays with wavelengths of about 1 A is feasible using ultralow emittance electron beams of a multi-GeV energy-recovery linac, combined with a low-loss crystal cavity. The device will produce x-ray pulses with 10{9} photons at a repetition rate of 1-100 MHz. The pulses are temporarily and transversely coherent, with a rms bandwidth of about 2 meV, and rms pulse length of about 1 ps.     

Statistical thermodynamics of an anharmonic oscillator

In the present study we investigate the statistical thermodynamics of the anharmonic oscillator, whose energies are characterized by the potential 1/2x ²+x ⁴. Employing the energies recently obtained by Hioe and Montroll, we compute the partition function and the thermodynamic quantities for the anharmonic and quartic oscillators. Low- and high-temperature formulas are presented for the thermodynamic quantities of the oscillators.     

Dynamics of an exciton-polariton parametric oscillator

The dynamics of an exciton-polariton parametric oscillator has been investigated. A system of nonlinear differential equations has been obtained for describing the time evolution of the densities of pump polaritons and polaritons of the signal mode. It has been demonstrated that, depending on the system parameters, the time evolution of the density of polaritons can occur in the periodic and aperiodic regimes, as well as at rest. The possibility of exercising phase control of the time evolution of the system has been proved.     

Stable periodic vibroimpacts of an oscillator

The asymptotically stable vibrations of a loaded oscillator colliding periodically with a rigid mass are described. Comparison of the numerical results with the few existing examples is encouraging but inconclusive. Better overall agreement is demonstrated with fairly comprehensive measurements from a specially built experimental rig. Impact motions are shown to be very sensitive to small fluctuations in the clearance between masses and the stiffness and loading of the oscillator near its linear, or collisionless, resonant frequency. The rigid mass is quite an effective damper at or just above this frequency condition.     

Periodic solution finder for an impact oscillator with a drift

In this paper, an efficient semi-analytical method is developed to compute periodic solutions for a new model of an impact oscillator with a drift, which explains the progression mechanism in vibro-impact systems and can be used to optimize their performance. The method constructs a periodic response assuming that each period is comprised of a sequence of distinct phases for which analytical solutions are known. For example, a period may consist of the following sequential phases: (I) contact with progression, (II) contact without progression, (III) no contact and (IV) contact without progression. Using this information, a system of four piecewise linear first order differential equations is transformed to a system of non-linear algebraic equations. The method allows one to accurately predict a range of control parameters for which the best progression rates are obtained.