摘要:

A simple imaging system to facilitate crystal orientation with respect to the x−ray beam for Berg−Barrett topography has been constructed. This system consists of an image intensifier tube with an x−ray phosphor deposited on its fiber−optic input plate and means to manipulate and indicate the crystal orientation. Applications of the system to studies of both

ISSN:0034-6748    

DOI:10.1063/1.1134048

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A theory of waveguide behavior near cut−off as applied to the measurement of refractivity is developed. It is shown that the cut−off condition provides a means by which small changes [0(10−6)] in refractivity can be accurately measured. The general operating characteristics of a laboratory instrument operating at microwave frequencies (X−band) and designed for the measurement of atmospheric refractivity is presented.

ISSN:0034-6748    

DOI:10.1063/1.1134049

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A relatively simple apparatus for determining the index of refraction of substrates such as ZnSe and the index of refraction of thin films deposited on a substrate is described. Use is made of a readily available Lansing mirror mount and two Lansing translational stages.

ISSN:0034-6748    

DOI:10.1063/1.1134050

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A method is described for producing thin, large area plastic films used for entrance windows of x−ray proportional counters in rocket−borne experiments. Sizes up to 1800 cm2have been successfully prepared and flown.

ISSN:0034-6748    

DOI:10.1063/1.1134051

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A seven−channel K−edge filter spectrometer which uses Si PIN−type diodes has been developed as an x−ray diagnostic tool for laser plasma experiments. The spectrometer is designed to sample the photon energy range from 500 eV to 20 keV. The theory and techniques involved in the application of a K−edge filter−Si diode spectrometer to laser plasma studies are presented. Electron temperatures in plasmas are often determined by the two−foil ratio method. The present work defines conditions under which such a measurement may prove unreliable. Typical absolute x−ray spectra obtained from subnanosecond irradiation of 1000 &mgr; CD2spheres with a few joules of laser energy yields 200 eV electron temperatures and a 1% laser to x−ray conversion efficiency.

ISSN:0034-6748    

DOI:10.1063/1.1134052

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A tunable low−temperature rf oscillator with Si MOSFETs as active devices is described. Tunability by a factor of 2 in frequency is reached by using GaAsP varactor diodes. Used as an NMR probe with27Al and51V, the oscillator allows magnetic fields to be measured in superconducting magnets with an accuracy of better than 0.1 G. We found the gyromagnetic ratio &ggr; of27Al and51V at 4.2 K to be 1.11119±1 and 1.12555±1 MHz/kG, respectively, corresponding to a Knight shift of + 1.61×10−3and + 5.58×10−3, respectively.

ISSN:0034-6748    

DOI:10.1063/1.1134061

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A stroboscopic pulse radiolysis system is described which detects the transient absorption generated by a 20 psec pulse from a 20 MeV linear accelerator. The time resolution is obtained by using, as the analyzing light, the short pulse of ?erenkov light generated by the portion of the electron beam which passes through xenon. The remaining portion of the electron beam is delayed by passing around a 270° magnet and the delay of the light may be varied by an optical delay line. Block diagrams for the electronics and the optics are given. The magnitude of sources of errors are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1134063

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Four impedances are combined around an operational amplifier to give many of the characteristics of a Wheatstone bridge, but with important differences. Both the input and the output are referred to a common ground, and in some applications linearity is greatly enhanced. Stability considerations which limit the range of usable impedances are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1134038

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The third−order asymptotic aberration coefficients of round electrostatic lenses are reformulated in terms of the coordinates formed by the projections of the asymptotic incident and final rays onto the reference plane of the lens. In this formulation, all aberration coefficients are finite for all lenses, in contrast to the formulation in terms of coordinates projected onto the focal planes of the lenses, where all of the coefficients become infinite in the limit of very weak lenses and for certain strong lenses. Equations for the six third−order aberration coefficients are derived in the form of integrals involving derivatives of the axial potential no higher than the second. Using these equations and previously calculated potentials and first−order trajectories, we have computed the six aberration coefficients for the accelerating and decelerating two−tube electrostatic lens for voltage ratios from 1.1 to 10000. The results are believed accurate to better than 0.2%.

ISSN:0034-6748    

DOI:10.1063/1.1134017

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

This paper describes a low−vibration specimen stage in which the specimen is held by a block which slides on Teflon pads over the lower surface of the SEM lens. It provides X, Y, and tilting motions.

ISSN:0034-6748    

DOI:10.1063/1.1134018

出版商:AIP    

年代:1975

数据来源: AIP