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15 Jul 1998

Volume 84, Issue 2, pp. 663-1158

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High power radio frequency generation by relativistic beams in dielectric structures

P. Schoessow, M. E. Conde, W. Gai, R. Konecny, J. Power, and J. Simpson

J. Appl. Phys. 84, 663 (1998); http://dx.doi.org/10.1063/1.368119 (5 pages) | Cited 6 times

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We have studied the interaction of a high current electron beam with dielectric loaded waveguides as a source of electromagnetic radiation. A unique high current photoinjector-based electron linac was used to generate the drive beam for these experiments, and the fields generated were diagnosed using a trailing probe (witness) beam from a second photocathode gun. Traveling wave dielectric structures with luminal (vphase = c) frequencies of 15 and 20 GHz were used. The radio frequency power levels generated in these initial experiments were very large—up to 11 MW.
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41.75.Ht Relativistic electron and positron beams
29.20.-c Accelerators
07.77.Ka Charged-particle beam sources and detectors
29.27.Fh Beam characteristics

Measurement of sound velocity and thickness of thin samples by time-resolved acoustic microscopy

Volker Hänel

J. Appl. Phys. 84, 668 (1998); http://dx.doi.org/10.1063/1.368120 (3 pages) | Cited 10 times

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Simultaneous measurement of sound velocity and thickness of thin specimens is a well-known technique in time-resolved acoustic microscopy. However, the applicability is restricted, because a substrate in contact with the back of the sample is required. Furthermore, the substrate must have an uncoated area, because a reference signal from the substrate’s surface is needed. To overcome these performance limitations, a technique has been developed that focuses the lens on the front and afterwards on the back of the sample. An equation for the longitudinal sound velocity of thin samples has been analytically deduced using this approach. Having calculated the sound velocity, the thickness of the sample directly follows using known relations. Additionally, the developed method has been experimentally applied to thin polyvinylidene fluoride film. The results confirm the capability of the method. © 1998 American Institute of Physics.
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43.35.Yb Ultrasonic instrumentation and measurement techniques
43.58.Dj Sound velocity
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)

Paratellurite: Propagation of the slow shear wave in the (001) plane. New formulations for the acoustic velocity and divergence

J. C. Kastelik, M. Gharbi, and M. G. Gazalet

J. Appl. Phys. 84, 671 (1998); http://dx.doi.org/10.1063/1.368121 (4 pages) | Cited 3 times

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The propagation of the slow shear wave in paratellurite with an angular tilt θ from the [110] axis in the (001) plane is considered. Original formulations are given for the acoustic velocity, the power flow angle, and the acoustic divergence. For a small angular deviation, the acoustic spreading is greatly reduced. This configuration can be used for multichannel Bragg cells. In order to demonstrate the feasibility of such a device, a three-channel Bragg cell (θ = 5°) has been designed and successfully tested. © 1998 American Institute of Physics.
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62.65.+k Acoustical properties of solids
42.79.Jq Acousto-optical devices
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects

Reconstruction theory of thermal conductivity depth profiles by the modulated photoreflectance technique

M. H. Xu, J. C. Cheng, and S. Y. Zhang

J. Appl. Phys. 84, 675 (1998); http://dx.doi.org/10.1063/1.368122 (8 pages) | Cited 4 times

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A reconstruction theory of thermal conductivity depth profiles from modulated photoreflectance data has been reported. This theory is based on the pulsed spectrum technique and a regularization method. The performance of this approach is illustrated by numerical simulations. © 1998 American Institute of Physics.
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05.70.Ce Thermodynamic functions and equations of state
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
78.20.-e Optical properties of bulk materials and thin films

The influence of surface currents on pattern-dependent charging and notching

Gyeong S. Hwang and Konstantinos P. Giapis

J. Appl. Phys. 84, 683 (1998); http://dx.doi.org/10.1063/1.368123 (7 pages) | Cited 7 times

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Surface charge dissipation on insulator surfaces can reduce local charging potentials thereby preventing ion trajectory deflection at the bottom of trenches that leads to lateral sidewall etching (notching). We perform detailed Monte Carlo simulations of pattern-dependent charging during etching in high-density plasmas with the maximum sustainable surface electric field as a parameter. Significant notching occurs for a threshold electric field as low as 0.5 MV/cm or 50 V/μm, which is reasonable for the surface of good insulators. The results support pattern-dependent charging as the leading cause of notching and suggest that the problem will disappear as trench widths are reduced. © 1998 American Institute of Physics.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning
73.25.+i Surface conductivity and carrier phenomena
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