摘要:

A high‐current, three‐cavity, standing‐wave linear electron accelerator (PHERMEX) has been designed and built to produce a pulsed bremsstrahlung beam. This beam was desired for use in flash radiography of explosively driven metal configurations, as an aid in the study of shock‐induced hydrodynamic phenomena. An unfocused beam exceeding 70 A for 0.10 or 0.20 &mgr;sec is available, at a peak energy of about 20 MeV. A 20 A beam for radiographic use, for the same time intervals and peak energy, is focused directly onto a tungsten target to form a 3 mm diam bremsstrahlung source.

ISSN:0034-6748    

DOI:10.1063/1.1719343

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

An interferometer for use in aerodynamic and heat transfer studies has been designed and tested. As in a Mach‐Zehnder interferometer, the light beam is large in cross section (to permit a large field of view in the test apparatus) and traverses the test section only once. Using a continuous wave laser as a source, the light beam is split and eventually recombined when small in cross‐sectional area. This permits all optical components, other than two paraboloidal mirrors, to be much smaller than the field of view in the test section. The new design results not only in a less expensive unit, since most of the components are small, but also one that is much simpler to adjust than a conventional Mach‐Zehnder interferometer.

ISSN:0034-6748    

DOI:10.1063/1.1719344

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Beams of noble gas ions produced with a duoplasmatron ion source were magnetically analyzed while the gas pressure in the source was varied. At high pressure the beam consisted primarily of singly charged ions. With decreasing pressure the yield of multiply ionized ions increased and was finally limited by the rising arc voltage which caused overheating of the anode. No measurable amount of He2+or Ne2+was detected. In the other gases the following maximum yields were measured for the more highly ionized species: 63% A2+, 54% Kr2+, 16% Kr3+, 24% Xe2+, and 1.2% Xe3+. Traces of molecular ions were detected in all the noble gases studied.

ISSN:0034-6748    

DOI:10.1063/1.1719345

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Dense beams of positive ions of less than 1.0 keV energy have been produced using a duoplasmatron with an extraction voltage of 20 kV as a source. Outward radial electrostatic forces due to space charge impose a restriction upon the intensity of an ion beam while it is being formed in vacuum. This paper discusses the problem of designing the electrostatic lens system for decreasing the energy of the ions while simultaneously focusing them to produce a maximum density parallel beam. The system consisted of a unipotential lens, which was integral with the source (Radiation Dynamics type DY‐1), and two additional immersion lenses. Most of the deceleration and beam compression was accomplished in the last lens. Its design was the major problem. Because a fairly exact analysis would have been very complicated, a simple approximate method for designing this lens was devised. The design values of current in the final low energy beam checked well with those from experiment.

ISSN:0034-6748    

DOI:10.1063/1.1719346

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A magnetic nuclear‐electron double resonance spectrometer operating in magnetic fields of about 175 G is described. It is suited for measurements of dynamic nuclear polarization and relaxation times in proton and fluorine containing solvents. The NMR spectrometer is a Q‐meter device synchronized by a crystal oscillator. The uhf setup for the saturation of the ESR lines consists of a frequency multiplied driver stage and a 493 Mc power stage. The sample is placed inside a quarter wavelength coaxial cavity with the NMR coil around it. A rapid modulation technique allows u‐mode detection and convenient comparison of NMR signals with and without ESR irradiation. The nuclear relaxation times (T2) are measured by observing the decay of the magnetization brought into the x,y plane by an adiabatic passage in the presence of a strong rf field. The performance is demonstrated with examples of proton polarization studies in organic solutions of free radicals.

ISSN:0034-6748    

DOI:10.1063/1.1719347

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The design and operating procedure of apparatus for direct microscopic measurement of step movement during crystal growth is presented. The equipment consists of a microscope for observation of growth features, a reaction cell, furnace, and gas‐flow control system. The apparatus has been employed to investigate growth mechanisms operative during the deposition of germanium by dissociation of GeI2in an open tube flow system.

ISSN:0034-6748    

DOI:10.1063/1.1719348

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A torsion‐Knudsen effusion‐recoil apparatus with an automatic controlling and recording microbalance system was devised to determine the atomicity of metallic vapors. A detailed description is given of the apparatus and the calibration procedure. Data are presented in order to evaluate the experimental reliability and precision of the instrument.

ISSN:0034-6748    

DOI:10.1063/1.1719349

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A new ultrasonic liquid level gauge without moving parts is described in which two wire helices are employed as acoustic waveguides, transmitting sound energy from the top of the tank to the liquid surface and back. The directional propagation in the receiving wire is controlled by the sense of the helix and synchronous reinforcement of pulse coupling between the wires by the side‐by‐side juxtaposition of the two helices is achieved, resulting in a high signal‐to‐noise ratio of the device.

ISSN:0034-6748    

DOI:10.1063/1.1719350

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Two auxiliary circuits are described for incorporation in a pulsed nuclear magnetic resonance system to reduce the deadtime of the system following an rf exciting pulse. The function of one, a driven balanced clamp, is to reduce the Q of the detecting circuit for a controlled time after each pulse. The other, a symmetric damping circuit requiring little operating power, works in conjunction with the transmitter to ``square‐up'' the rf pulses generated. The circuits presented here represent certain improvements in established techniques of clamping and damping. Additionally, it is pointed out that there is a particular advantage, with respect to minimizing the deadtime in a coherent system, of using timing pulses which are phase locked to the rf reference.

ISSN:0034-6748    

DOI:10.1063/1.1719351

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A vacuum tight barium fluoride window with transmission range from 1800 Å to 14 &mgr; is described. The window consists of a barium fluoride disk sealed into a suitably formed fine silver spinning with silver chloride. Evacuated envelopes incorporating this window have been made and kept for months without indication of leakage, based on the performance of photoelectric cathodes in the vacuum space. This technique has been equally successful in sealing lithium fluoride windows. The sealing procedure is fully discussed.

ISSN:0034-6748    

DOI:10.1063/1.1719352

出版商:AIP    

年代:1965

数据来源: AIP