摘要:

A simple noniterative method using an orthonormal basis for expressing field distributions has been developed for obtaining surface‐wave solutions in piezoelectric crystals. Velocity and field distributions are obtained forYZLiNbO3that agree with earlier works. The boundary conditions are incorporated in a manner that is easily adapted to layered structures. Dispersion curves are obtained for surface waves in LiTaO3with a SiO2layer at the surface; the results are in good agreement with those published earlier.

ISSN:0021-8979    

DOI:10.1063/1.324670

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The lead myristate multilayer analyzer has provided a basis for a relatively simple and efficient spectroscopy for the low‐energy x‐ray emissions in the 20–80‐A˚ region (where conventional crystal spectroscopy and grazing incidence grating spectroscopy are generally inefficient). The percent reflectivity, the integrated coefficient of reflection, and the Bragg diffraction width of the lead myristate analyzer have been measured and found to be consistent with the predictions of a simple theoretical model for multilayer diffraction. This multilayer spectroscopy at large Bragg angles has a high efficiency (high instrument transmission) as compared to grazing incidence grating spectroscopy in this 20–80‐A˚ region. However, the resolution is limited to that set by the diffraction width of the lead myristate analyzer of about 1 eV. Because the collimator‐crystal broadening function can be precisely defined, a simple and effective deconvolution procedure can be applied with this multilayer spectroscopy to bring the resolution into the sub‐electron‐volt region. To demonstrate the efficiency of lead myristate spectroscopy in the 20–80‐A˚ region, spectra were measured and analyzed from x‐ray excited fluorescent sources which are characteristically of low intensity. (X‐ray excitation yields a minimum of background spectra and of radiation damage.) These include theL2,3atomic spectrum of argon and the C‐Kmolecular spectrum of CO2, both in the gas phase, and the Cl‐L2,3and O‐Kspectra from solid lithium perchlorate. Many samples undergo appreciable radiation‐induced chemical change during the exposure time that is required for measurement—even with an optimally fast spectrograph and with fluorescent excitation. A method has been developed to evaluate and to correct for radiation damage by distributing the exposure over an effectively large sample volume either by gas flow or by rotating through multiple samples during measurement. Several spectral scans were made on the LiClO4using six samples. The total exposure time for each data point in each scan was recorded which permitted an extrapolation into a ’’zero’’ exposure spectrum. Finally, Fe‐L2,3/O‐Kspectrum (from Fe2O3) in the 17–25‐A˚ region is presented to illustrate the effectiveness of the lead myristate analyzer in third‐order diffraction. For this multilayer, the third‐order diffraction efficiency is one‐third that of the first order and is nearly twice that of the second order for this wavelength region.

ISSN:0021-8979    

DOI:10.1063/1.324671

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The field backscattered from a remote surface into the laser cavity induces an efficient modulation, both in amplitude and frequency, of the cavity field. The modulating signals are the interferometric components (sin and cos) of object optical path length, which can be recovered by heterodyne detection through a separate reference‐frequency mode. Using a dual polarization Zeeman stabilized He‐Ne laser, a compact self‐aligning interferometer is developed.

ISSN:0021-8979    

DOI:10.1063/1.324672

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Highly exposed radiographs are utilized in microradiography in order to increase the signal‐to‐noise ratio. Relief radiography enables the evaluation of these microradiographs. Relief‐exposure characteristics are shown to follow a relationship of the typeR=Rm[1−exp(−E/Em)], whereRis the relief height,Eis the exposure, andRmandEmare constants. The density of developed silver in Ilford L‐4 nuclear emulsion is found from the value ofRmto be 2.86. The constantEmis shown to give the exposure for maximum contrast. The experimental results are discussed and compared to those found in the literature.

ISSN:0021-8979    

DOI:10.1063/1.324673

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Possible methods are described for constructing ion linear accelerators in the 100‐MeV range which have pulsed current outputs 105times higher than currently available. A drift‐tube design with insulating magnetic fields between the tubes is presented. The fields not only prevent electron flow, but also are essential for beam neutralization by low‐energy electrons and transverse beam focusing. Preliminary discussions are given on accelerator design and construction, transverse focusing and beam neutralization, and control of the beam in longitudinal phase space.

ISSN:0021-8979    

DOI:10.1063/1.324674

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A high‐fluence reflection‐refraction x‐ray spectrometer allows spectral diagnosis of intense bursts ofxradiation from about 0.5 to 8 keV. Grazing‐incidence x rays, reflected first by a vitreous carbon mirror, are rereflected off the flat polished face of a plastic scintillator that is viewed by a photomultiplier tube. By making the scintillator‐mirror reflection angle greater than the carbon‐mirror angle, one efficiently refracts an energy band out of the incident spectrum into the scintillator. Reflection by the carbon mirror determines the high‐energy edge of the bin, whereas refraction into (or reflection from) the subsequent scintillator determines the lower edge. The current from the photomultiplier is a direct time‐dependent measure of the contents of the band. The sharpness of the band edges (about 0.1 keV) determines the narrowest measurable energy band and hence best possible energy resolution. The response to light of the scintillator‐photomultiplier limits the sensitivity. Measurements with continuum and monoenergetic sources are compared to theory.

ISSN:0021-8979    

DOI:10.1063/1.324675

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Ion‐beam optics of a two‐stage electrostatic accelerator (i.e., the extraction‐accel‐decel column) is studied by three approaches: (i) a linear optics analytic solution based on the paraxial equations which account for lens effects and beam space charge, (ii) a nonlinear optics solution based on the Poisson‐Vlasov equations and including the two‐dimensional source‐plasma sheath, and (iii) a 60‐kV single‐beamlet experimental study. Principal results are that in certain operating modes, the minimum beam divergence in a two‐stage source is significantly less than in the conventional single‐stage source and that the optics of the two‐stage source is less sensitive to variation in extraction perveance about the divergence minimum. This is because the optimum extraction perveance in such modes of operation is relatively high, causing the crucial residual aberration fields near the first electrode to be smaller.

ISSN:0021-8979    

DOI:10.1063/1.324676

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Characteristics of high‐energy/power amplifiers including large‐signal gain, extraction efficiency, and pulse deformation are analyzed in terms of material and operating parameters. A figure of merit for large‐signal amplifier material is defined, which is inversely proportional to the stimulated‐emission cross section. A method for detailed pulse tailoring in nonlinear amplifiers is developed. It is found that a high stored‐energy density, which is obtainable with a small stimulated‐emission cross section, is very important for achieving high gain and tolerable pulse deformation. The high stored‐energy density is also found to be effective for suppressing laser beam degradation due to nonlinear refractive‐index effects.

ISSN:0021-8979    

DOI:10.1063/1.324677

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Direct measurements of the vibrational distribution tov?30 obtained from the first overtone emission from CO in a liquid‐N2‐cooled laser plasma have been made in the presence of varying amounts of O2. These observed distributions show enhanced vibrational populations for small additions and show upper‐level depopulation for larger additions. Both observations support a recent plasma‐kinetic model of the effect of O2in low‐pressure CO laser plasmas.

ISSN:0021-8979    

DOI:10.1063/1.324664

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

We report the observation of repetitive self‐Q‐switched pulses from a continuously operating ruby laser pumped by an argon ion laser. 500‐W pulses of 2 nsec width at a 3‐kHz rate are observed. It is tentatively concluded from the pulse characteristics and other data that the phenomenon can be explained by a saturable absorber mechanism.

ISSN:0021-8979    

DOI:10.1063/1.324665

出版商:AIP    

年代:1978

数据来源: AIP