摘要:

The three‐dimensional eddy current transient field problem is formulated using theu‐vmethod. This method breaks the vector Helmholtz equation into two scalar Helmholtz equations. Null field integral equations and the appropriate boundary conditions are used to set up an identification matrix which is independent of null field point locations. Embedded in the identification matrix are the unknown eigenvalues of the problem representing its impulse response in time. These eigenvalues are found by equating the determinant of the identification matrix to zero. When the initial transient forcing function is Fourier decomposed into its spatial harmonics, each Fourier component can be associated with a unique eigenvalue by this technique. The true transient solution comes through a convolution of the impulse response, so obtained with the particular external field decay governing the problem at hand. The technique is applied to the FELIX (fusion electromagnetic induction experiments) medium cylinder experiment; computed results are compared with data. A pseudoanalytic confirmation of the eigenvalues so obtained is formulated to validate the procedure.

ISSN:0021-8979    

DOI:10.1063/1.339998

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The electron beam in a linear induction accelerator is generally susceptible to growth of the transverse beam breakup instability. In this paper we analyze a new technique for reducing the transverse coupling between the beam and the accelerating cavities, thereby reducing beam breakup growth. The basic idea is that the most worrisome cavity modes can be cutoff by a short section of coaxial transmission line inserted between the cavity structure and the accelerating gap region. We have used the three‐dimensional simulation codeSOSto analyze this problem. In brief, we find that the technique works, provided that the lowest TE mode cutoff frequency in the coaxial line is greater than the frequency of the most worrisome TM mode of the accelerating cavity.

ISSN:0021-8979    

DOI:10.1063/1.341136

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A one‐dimensional thermal model is presented for calculating the maximum output power from InGaAsP/InP (&lgr;=1.3 &mgr;m) buried heterostructure lasers, whose output power is limited by thermal considerations. The effect of Auger recombination and ohmic resistance, which play significant roles in these lasers at high temperatures, is included. We have also incorporated the temperature dependence of efficiency from first principles using experimentally available data for Auger and radiative recombination coefficients. Calculations made on InGaAsP/InP lasers show that a maximum cw power of 57 mW/facet (diamond heat sink) and a maximum operating temperature of up to 132 °C for a geometry similar to the double‐channel buried heterostructure laser can be achieved. In addition, the model has been used to determine the maximum achievable power as a function of device geometry (active layer thickness, width, and length of the device). We find that by increasing the length of the laser from 300 to 700 &mgr;m we can increase the output power of the laser by 79%. The results obtained agree reasonably well with experiment.

ISSN:0021-8979    

DOI:10.1063/1.339999

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Recent theoretical studies of liquid/solid impact, in particular the geometric wave theory of Lesser and Field, have emphasized the importance of the detailed geometry in the contact area. In parallel with the theoretical work, we have developed a two‐dimensional technique using gels for impact and shock studies. A combination of high‐speed photography and schlieren optics allows the shocks in the liquid and solid, if it is transparent, to be visualized, as well as important processes, such as jetting, to be recorded. This paper describes the gel technique and gives results for a range of surface geometries for collision velocities of a few hundred meters per second. The relevance to damage initiation in liquid/solid impact problems, such as rain erosion, steam turbine blade erosion, and cavitation, are discussed.

ISSN:0021-8979    

DOI:10.1063/1.340000

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A radio‐frequency discharge characteristics model for the dc self‐bias current densityJsbversus the dc self‐bias voltageVsband the gas pressurepis developed. The model considers positive ions and electrons only and is consistent with a previously developed model for dc sputtering discharge characteristics. Two different concepts for the cathode fall distance are established:Li, for the ions, which is time independent, andLe, for the electrons, which is a time‐averaged length. A relationship between the cathode fall distanceLand the discharge efficiencynis developed. The area ratio power law for the voltage distribution between the electrodes is theoretically analyzed and the resulting quadratic power law is experimentally confirmed. The predicted pressure dependence ofVsbis rather complicated, and its mathematical expression has been left with an adjustable exponential parameter to be determined by the best fit to experimental data.

ISSN:0021-8979    

DOI:10.1063/1.340001

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

He‐implanted samples of LiNbO3have been analyzed by 24‐MeV28Si elastic recoil detection. For 50‐keV He implants, the Li and H profiles show a depletion of Li from the sample near‐surface region which coincides with a gain of H. The Li loss is seen to increase with increasing ion fluence and implantation temperature.

ISSN:0021-8979    

DOI:10.1063/1.340002

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Experiments were performed that examined the behavior of overlapping populations of two triplet combinations of implanted dopants in silicon: arsenic‐argon‐boron and boron‐argon‐phosphorus. It was found that the chemical profile and electrical activity of arsenic could be adjusted practically at will. Anomalous behavior was observed with boron. Similar control was displayed with boron and phosphorus when argon was present. The experimental results are both consistent with and supportive of calculations on a model silicon lattice that predict complex formation; arrangements of these triplets in close proximity are more stable energetically than when they are sufficiently separated that interactions are minimal.

ISSN:0021-8979    

DOI:10.1063/1.340003

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A model of multiple processes is used to simulate the behavior of reaction in detonation of heterogeneous high explosives. The features of the model are (1) the partition of the explosive medium into hot spots and the region exclusive of hot spots and (2) the separation of the mechanical‐thermal process and chemical process. For each process, a characteristic time is assigned and is defined by a phenomenological relation. With assumptions, some fast processes are ignored in the governing equations. This investigation indicates the necessity of including a slow process near the end of the reaction. Comparisons with experiments using a Fabry–Perot velocimeter are presented for triaminotrinitrobenzene.

ISSN:0021-8979    

DOI:10.1063/1.340004

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Interdiffusion and structural change on annealing of sputter‐deposited Mo/Si and Mo(N)/Si(N) multilayer thin films have been investigated over the temperature range from 674 to 1027 K. X‐ray diffractometry shows that in the as‐deposited Mo/Si multilayers the Mo is bcc with the stacking of (110) plane parallel to the substrate, and the Si is amorphous, while in the as‐deposited Mo(N)/Si(N) multilayers, both Mo and Si nitrides are amorphous. The interdiffusivities have been determined from the decay rate of satellite peak intensity around (000). The activation energies for the interdiffusion in Mo/Si and Mo(N)/Si(N) multilayers are 105±5 and 351±88 kJ mol−1, respectively. A drastic decrease in the satellite peak intensity on annealing is observed in the Mo/Si multilayer films, which is interpreted to be due to interdiffusion and structural relaxation. On the other hand, a remarkable increase in the satellite intensity is found for the nitride multilayer films, which is explained by crystallization into &bgr;‐Mo2N/&agr;‐Si3N4. The modulation wavelength decreases by 8%–12% after anneal. The decrease in the thickness of annealed Mo/Si multilayer films is also found by a depth profilometer.

ISSN:0021-8979    

DOI:10.1063/1.340005

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We have characterized the diffusion of Zn into GaAs from the organometallic sources diethylzinc and trimethylarsenic. This method produces surface hole concentrations in excess of 1020cm−3with good control of junction depths as shallow as 0.1 &mgr;m. Smooth surface morphology is retained. The profile shape is much more complex than the accepted interstitial‐substitutional Zn‐diffusion model would predict. To explain the observed profiles, a new model for Zn diffusion is proposed and implemented in a computer simulation.

ISSN:0021-8979    

DOI:10.1063/1.340006

出版商:AIP    

年代:1988

数据来源: AIP