摘要:

The article represents a review of direct extraction sources of negative hydrogen ions. During the past year or so interest in this method of producing high intensity beams of negative ions has increased considerably because of new developments resulting in currents of more than 20 mA. The first part of the article deals with inelastic collisions between particles which lead to the creation or destruction of negative ions. The knowledge of such elementary processes is relevant because the intensity of extracted H−currents is determined primarily by the equilibrium between the competing processes of creation and destruction. Attempts by several authors to analyze theoretically the production of H−ions in the plasma of a discharge will be explained subsequently and their results compared with experiments. Four types of direct extraction sources will be described next: duoplasmatrons, hollow discharge duoplasmatrons, Penning sources, and magnetron sources. Details of their design and beam characteristics will be given, as well as suggestions for further improvements.

ISSN:0034-6748    

DOI:10.1063/1.1685973

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A new method to produce high pulsed magnetic fields has been developed. Capacitors generally used for the storage of energy have been replaced by a superconducting coil which requires less space and lower operating cost. The choice for the different elements of the setup is discussed. A low energy model has produced a field of 20 teslas with a time constant of 15 msec.

ISSN:0034-6748    

DOI:10.1063/1.1685974

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A new diode‐quad transducer bridge circuit has been developed which features: (1) a high output that is independent of excitation frequency and waveform; (2) a fractional capacitance (&Dgr;C/Co) resolution of 4.4 × 10−8at a bandwidth of 10–30 Hz; and (3) the capability of conveniently grounding the transducer. Application to a capacitive transducer for pressure measurements yielded an output resolution of 0.003% corresponding to a pressure resolution of ± 1.5 × 10−4Torr.

ISSN:0034-6748    

DOI:10.1063/1.1685975

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An experimental arrangement is described which allows the exact determination of the density of neutral water traces in a cylindrical hollow cathode during operation of the discharge.

ISSN:0034-6748    

DOI:10.1063/1.1685976

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A bridge circuit is described which provides an increase in signal/noise by a factor of 10–100 over previous designs frequently used to monitor very low temperature resistance thermometers. The four‐terminal arrangement reads directly in ohms and requires that only the thermometer be located in the cryostat.

ISSN:0034-6748    

DOI:10.1063/1.1685977

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

This paper describes the application of laser‐Doppler anemometry to measurement of velocity distributions in two‐phase suspensions. It is shown that two groups of scattering particles, members of each of which are different in size and move with distinct velocities, will produce separate signals in the frequency domain, different in both amplitude and frequency. Block diagrams of the electronics used in the measurement of suspension flow are shown.

ISSN:0034-6748    

DOI:10.1063/1.1685978

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A method is described for generating single millijoule pulses of nanosecond duration through use of a CO2laser mode‐locked with a Brewster angle, acousto‐optic modulator coupled with an electro‐optic switch (extinction ratio of 50 000:1) driven by a laser‐triggered spark gap. The Brewster angle geometry eliminates the damage problems associated with the use of AR‐coated normal incidence modulators.

ISSN:0034-6748    

DOI:10.1063/1.1685979

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An experimental study was conducted of the performance of a translatory, magnetic suspension utilizing ceramic permanent magnets for vertical support and servo‐controlled electromagnets for lateral stability. Drag measurements were confined to low velocities ([less than double sim] 40 cm/sec); a typical measured value of drag coefficient is drag force/weight = 1.8 × 10−4at 18 cm/sec. Use of laminated electrical sheet rather than mild steel should provide an order of magnitude reduction in this value. For low amplitude oscillations in a magnetic valley, drag decreases further by about two orders of magnitude; free oscillations have been observed to continue for 12 min. In contrast, instrument quality ball bearings have a friction coefficient in the 10 to 40 × 10−4range. The total power required to maintain support is about two orders of magnitude lower than for a dc electromagnet suspension system. Assuming eddy current drag force proportional to velocity and hysteretic drag force independent of velocity, measured drag values extrapolated to high speed indicate that with laminated magnetic elements, the magnetic drag force would be low compared to air drag for a similarly suspended vehicle traveling at 270 m/sec (600 mph) in a tube evacuated to 10−3atm. The vehicle coasting at this velocity would lose little more than 1% of its velocity in 93 km (53 miles).

ISSN:0034-6748    

DOI:10.1063/1.1685980

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An x‐ray photoelectron spectroscopy (ESCA) apparatus designed specifically for surface research is described. The features, included in one vacuum envelope, are ultrahigh vacuum, a high intensity x‐ray source, a 10 cm mean radius hemispherical electron energy analyzer, sample cleaning by argon ion bombardment, sample heating by electron bombardment, and the facility for the collection of electron spectra as a function of angle relative to the surface plane of the sample. It is shown that (1) sample cleaning increases net signal strengths by factors as great as 14; (2) less than 2% of a monolayer of cesium on a clean molybdenum substrate can be readily detected; and (3) that ultrahigh vacuum is essential for investigation of well‐defined surfaces. Surface sensitivity is increased by an order of magnitude when spectra are collected at low electron take‐off angles relative to the surface plane, and the importance of measuring angular dependence of spectra for interpretation of data from surfaces is demonstrated.

ISSN:0034-6748    

DOI:10.1063/1.1685981

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A new version of an oscillating crucible viscometer is described which presents some advantages over previous types: (1) simpler mechanical construction which does not need great accuracy;(2) the two parameters of the viscometer can be varied in an ample range, allowing the measurement of the kinematic viscosity of all kinds of liquids.

ISSN:0034-6748    

DOI:10.1063/1.1685982

出版商:AIP    

年代:1973

数据来源: AIP