摘要:

This paper describes a method for the compensation of the spherical aberration of a polar diatomic molecule in an electrostatic quadrupole field. This perturbation, caused by the higher order terms in the Stark effect, limits the opening angle of the lens and is compensated by an electrostatic hexapole field placed in the middle of the quadrupole field where the influence is the strongest. A detailed mathematical treatment of the motion of a molecule in a composite lens is given and the calculations show that the transmission of the lens increases by a factor 5. Preliminary experiments confirm the theoretical predictions.

ISSN:0034-6748    

DOI:10.1063/1.1686230

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Over 1200 Alnico magnets (1.3 × 1.3 × 4 cm) are used to contain a conventional discharge plasma produced by 1–20 A of emission from 6–48 small filaments at − 60 V. Densities up to 1012ions/cm3are produced in argon at 2 × 10−3Torr. At 5 × 10−6Torr typical parameters are: 8 × 1010ions/cm3;ni/n0≈ 0.7;Te≈ 5 eV;Ti≈ 0.5 eV; noise ⟨ &dgr;n/n⟩ ≈ 2 × 10−4; and < 1% nonuniformity over a volume 31 cm diam by 69 cm. Uniform dense plasmas of He, D, and H are also produced. The ion containment appears to be both magnetic and electrostatic.

ISSN:0034-6748    

DOI:10.1063/1.1686231

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The design and performance of a digital microwave frequency lock system is described. The system locks a microwave source to a fixed intermediate frequency oscillator by digitally comparing the down‐converted microwave frequency to the IF. The microwave source may be frequency swept at a variable rate whose precision is the same as the reference oscillator, and the microwave source retains the long term stability of thefixedfrequency reference oscillator even when the microwave frequency is being swept. The digital frequency lock system is compared with an analog phase lock system, and it is concluded that the digital frequency lock is superior with respect to capture range and reliability, identical with respect to long term stability, and inferior with respect to spectral purity.

ISSN:0034-6748    

DOI:10.1063/1.1686232

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A charge sensitive preamplifier (CSP) followed by an amplifier with pulse shaping networks (PSA) of single differentiation‐single integration type (SDSI), designed to be used with uncooled silicon nuclear particle detectors aboard space vehicles, is described. Noise performance at 5 &mgr;sec SDSI time constant was measured to be 0.91 keV FWHMSiwith a slope of 43 eV/pF. The total power drain is 42 mW at + 12 V supply. The amplifier is stabilized against supply voltage and temperature variations.

ISSN:0034-6748    

DOI:10.1063/1.1686233

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An instrument is described which allows automatic recording of the temperature or magnetic‐fielddependence of both the magneto‐optic Faraday rotation and the ellipticity angle of circular dichroism ofmagnetic samples. The instrument includes a Wollaston analyzer prism, two light detectors, and an operational amplifier circuit containing an electronic divider for eliminating the influence of light intensityvariations. Changes of 10″ in the Faraday rotation angle and of 1′ in the angle of circular dichroism aredetectable with our equipment.

ISSN:0034-6748    

DOI:10.1063/1.1686234

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Two UHV systems have been built for studies of solid surfaces by ion backscattering in the energy ranges (a) 0.5–50 keV and (b) 100–300 keV on separate ion accelerators. The UHV systems are similar in most respects except that (b) has LEED optics. The stainless steel chamber with integral pumping system encloses a goniometer in which the sample can be rotated and tilted for alignment of a crystal axis with the beam. The sample can also be translated across the beam. The energies of backscattered ions are measured in an electrostatic analyzer which has three independent motions to allow the analyzer to be precisely aimed at the beam spot on the sample. The chamber sits on a table which can be adjusted vertically and horizontally. Samples can be inserted conveniently through a 3.8 cm side port and attached to the goniometer with a special tool. Special problems encountered in mating a UHV system to an ion accelerator will be discussed. Results of measurements in system (a) have been reported [D. J. Ball, T. M. Buck, D. MacNair, and G. H. Wheatley, Surface Sci.30, 69 (1972)].

ISSN:0034-6748    

DOI:10.1063/1.1686235

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Portable equipment for recording millisecond‐integration‐time photoelectric photometric data is described. Digital data are reliably recorded on standard 6.35 mm audio grade magnetic tape via a quadradial audio grade tape deck. The system is designed specifically for recording lunar occulations of stars, but the data recording technique is independent of the data source. Recovery of the data is made via minicomputer.

ISSN:0034-6748    

DOI:10.1063/1.1686236

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Modifications which permit control and sweeping of Hall‐effect magnetic‐field regulators by an external voltage source are presented. A four‐quadrant multiplier is used as a modulator. Cost is nominal, installation and alignment straightforward, and no loss in performance with respect to stability, linearity, and accuracy is introduced for most applications.

ISSN:0034-6748    

DOI:10.1063/1.1686237

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Theory, design parameters, and construction details are presented for a linac which accelerates charged microparticles in the 1–10 &mgr; diam range to meteoric velocities. The linac is of the Sloan‐Lawrence (low‐frequency, ac driven) type and contains 92 accelerating gaps with 100 kV accelerating potential applied at each gap. Particles are injected into the linac after preacceleration by a 1.6 MV modified Van de Graaff, giving a total accelerating potential of 10.8 MV for the system. In a significant departure fromconventional accelerator practice, the linac is adapted to single particle operation by employing a squarewave driving voltage with the frequency automatically adjusted from 12.5 to 125 kHz according to the variable velocity of each injected particle. Radial focusing is entirely second‐order and is adequate to contain the particle ``beam'' within 1.8 cm diam. Compared to the Van de Graaff alone, the linac provides a particle mass increase of about 300 times for a given velocity, or a velocity increase of about 2.5 times for a given mass.

ISSN:0034-6748    

DOI:10.1063/1.1686238

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A dual beam flash photolysis system for studying the kinetics of transient species is described. The system has high sensitivity and is capable of detecting species absorbing 0.1% of the analyzing light with a noise level equivalent to 0.02% of the analyzing light. This high sensitivity has been achieved by producing an intense (6.2×1018photons in the uv) flash of short duration (0.9 &mgr;sec to decay to half height and 3 &mgr;sec to decay to 1%). We have also used an analyzing lamp which is intensified to 30 times its normal brightness and a long path (27 cm) through the solution. The photomultipliers have been adjusted to be linear up to 10 mA so that the potentialities of the intensified analyzing beam may be exploited. Spurious transients produced in the water have been reduced by careful distillation of the water followed by further purification through the photolysis reaction of the flash itself. The configuration of the apparatus and components is described in detail.

ISSN:0034-6748    

DOI:10.1063/1.1686239

出版商:AIP    

年代:1973

数据来源: AIP