摘要:

This article reviews the state-of-the-art in high-power microwave source research. It begins with a discussion of the concepts involved in coherent microwave generation. The main varieties of microwave tubes are classified into three groups, according to the fundamental radiation mechanism involved: Cherenkov, transition, or bremsstrahlung radiation. This is followed by a brief discussion of some of the technical fundamentals of high-power microwave sources, including power supplies and electron guns. Finally, the history and recent developments of both high-peak power and high-average power sources are reviewed in the context of four main areas of application: (1) plasma resonance heating and current drive; (2) rf acceleration of charged particles; (3) radar and communications systems; and (4) high-peak power sources for weapons-effect simulation and exploratory development. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148382

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The data gained on discharge pumped XeCl laser systems over the last 15 years were analyzed to identify common inherent regularities. It is obvious that there are three major classes of phenomena involved, namely: the electrical processes in the pumping circuit, the plasma-chemical kinetics, and the discharge contraction. It has been demonstrated that under certain conditions they can be considered separately. Such an approach allows one to estimatea priorithe optimal pumping conditions and the electrical circuit parameters to obtain the required laser energy. The results presented could be used in the engineering calculations of high-performance excimer laser systems to significantly reduce the cost of the design and the optimization stages. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148379

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have developed quite a simple and original lock-in photodetection system that works at a fixed radio frequency. The system includes a photodetector, a frequency down converter and a standard low-frequency lock-in amplifier. The resonant implementation of the radio-frequency attachment provides high gain and high selectivity, which have enabled us to attain the shot-noise-limited sensitivity to relative optical power change&dgr;P/P≃4×10−8Hz−1/2at a detection frequency of 6.2 MHz in measurements with a cw mode-locked Nd:yttrium aluminum garnet laser. We have realized the precise position-sensitive photodetection for laser pointing noise measurements and picosecond photoacoustic spectroscopy of solids. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148370

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The design of a device for the simultaneous application of uniaxial stress and hydrostatic pressure is presented. Shown in detail is the design of the part that applies the uniaxial force to the sample and first results of the simultaneous application of uniaxial stress and hydrostatic pressure to a semiconductor laser. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148371

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We present a new design of a Fabry-Pe´rot interferometer for Brillouin spectroscopy. Emphasis is placed on a quick change of the free spectral range without losing alignment, the possibility of switching the multipass arrangement from 3 to 5 pass and back, and finally on a simple and inexpensive construction. Besides this the new interferometer shows very good long term stability and is easy to handle. These features were not available before in this combination. The performance of the instrument will be demonstrated. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148372

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Two systems of widely tunable light sources for picosecond time-resolved resonance Raman(ps-TR3)spectroscopy have been constructed using a 1 kHz ps-Ti:sapphire laser/regenerative amplifier system. Performance of the systems was examined in terms of pulse duration, spectral width, pulse energy, and shot-to-shot stability. One system, consisting of white light continuum seeder and &bgr;-barium borate optical parametric amplifier, demonstrated tunability in the 500–660 nm range with 1.3–2.1 ps pulse duration and 15 &mgr;J pulse energy. The other system, consisting of a lithium triborate optical parametric generator in type II noncritical phase matching configuration and &bgr;-barium borate optical parametric amplifier, was found to yield visible pulses as high as 18 &mgr;J with 1.5–2.4 ps of pulse duration in the 520–630 nm region. The shot-to-shot stability of generated pulses is less than 10&percent; for both systems. Capability of the present systems is demonstrated by observingps-TR3spectra of nickel octaethylporphyrin in coordinating and noncoordinating solvents. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148373

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In order to obtain small angle scattering intensities in absolute units, measurements of the incident beam intensity and the intensity transmitted through the sample are required. For this purpose the scattering intensity of a calibrated polyethylene (LUPOLEN) standard is used. For the determination of the absolute photon flux and the correction of the scattering patterns obtained with a two dimensional position sensitive detector we use the detector response function. A set of data measured subsequently at the standard and at a given sample can be evaluated in a program that calculates a pattern in absolute units corrected by means of the detector response. This program also calculates the absolute photon flux, determines automatically the center coordinates of the incident beam, and calculates the scattering vectors that belong to the different positions on the detector. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148374

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We present an apparatus for fabricating ion exchanged glass waveguides with reproducible characteristics. It consists of a vertical furnace with a uniform temperature zone, which is flat to within 1 °C over the sample length, a silica crucible for containing molten salt, a metallic sample holder made of either aluminum or stainless steel, and a motor-driven sample lowering system. The time and temperature are accurately controlled to produce waveguides of desired index profiles. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148375

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Using the Monte Carlo method, we have calculated, for 50 keV electrons incident on a gold target, the dependence of the effective Sherman asymmetry function and scattered intensity on the target thickness and inelastic energy loss window for scattering angles from 90° to 180°. Our results show that, when the gold target is thicker than 700 Å or the inelastic energy loss window is larger than 1200 eV, the scattered intensity is maximum at a scattering angle of about 120°, and the effective Sherman function is almost constant over a wide range of scattering angles. Thus, for Mott scattering spin polarimeters, the electron detectors should be positioned at ±120°, and the larger the collection angle for scattered electrons, the higher the efficiency of the Mott polarimeter. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148381

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

This article reports the design and its special features for various grid biases for a retarding potential analyzer instrument aboard Indian satellite SROSS-C2 to ensure trouble free functioning of electron and ion traps. The polarities of the various grid biases, identify the difference between ion traps and electron traps. A new concept of generating bias sweeps on line for future missions has been proposed. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148376

出版商:AIP    

年代:1997

数据来源: AIP