摘要:

A solid‐state electronic integrator capable of integrating and digitizing small currents has been developed. In a recent experiment, pulsed proton beams with an average value of 10−9A have been integrated and measured with a 0.1% accuracy. Pulsed or direct currents can be measured accurately down to a lower limit imposed by uncompensated variations of the order of 10−13A in input leakage current. The current to be integrated is applied to a Miller integrator circuit which employs a commercially available solid‐state operational amplifier. A diode‐switched charging circuit gated on and off by the integrator output voltage ``pumps down'' the integrator capacitor with discrete units of negative charge, simultaneously delivering digital output pulses to an external counter. An output voltmeter provides analog readout of residual fractional charge increments.

ISSN:0034-6748    

DOI:10.1063/1.1718533

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A discharge chamber has been constructed with electrodes of transparent metallic mesh. By the addition of quenching agents, mainly I2vapor, to noble gases at atmospheric pressure, and the use of pulses of one or several microseconds duration, it is shown that a great number of discharges connecting the two electrodes can develop simultaneously, starting from the ionized path of a particle. Pulses in the microsecond range of 2 to 3 kV/cm are used, thus allowing the easy operation of large sensitive volumes. Tracks of good resolution are observed, with a variation of the luminosity as a function of the primary ionization. Repetition rates up to 104/sec are reached. Sparks following the trajectory of particles inclined at angles of 45° with respect to the electrodes are observed.

ISSN:0034-6748    

DOI:10.1063/1.1718534

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A sandwich technique is described for fabricating polystyrene‐silica replicas for repeated examination of a selected area of a specimen in the electron microscope. Electron micrographs of these repetitive replicas are presented. The technique includes a method for manipulating the specimen grid without slippage and, also, a method for eliminating the difficulty of stripping the preliminary impression from a heavily etched steel surface.

ISSN:0034-6748    

DOI:10.1063/1.1718535

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A drive capable of producing controlled velocities in excess of 100 cm/sec is described. The drive consists of a loudspeaker ``motor'' coupled to a velocity transducer. Feedback is used to make the velocity follow an input waveform accurately. The system uses standard parts and is easy to build.

ISSN:0034-6748    

DOI:10.1063/1.1718536

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A compact gas high pressure cell for measuring the optical properties of solids at low temperatures under pressures up to 10 kilobars is described. Using helium gas as the pressure‐transmitting medium, the pressure is purely hydrostatic at 78°K and nearly hydrostatic at 7–12°K. Techniques are discussed for sealing windows of sapphire for optical studies, of beryllium for x irradiation, and dummy windows for electrical connections. A cryostat which can be accommodated in most recording spectrophotometers is also described.

ISSN:0034-6748    

DOI:10.1063/1.1718537

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A piezoelectric quartz crystal microbalance, utilizing a commercially available crystal, is described. It is bakeable for ultra‐high vacuum use. It has been employed in adsorption studies and for measurement of deposition rates in condensation and polymerization processes.

ISSN:0034-6748    

DOI:10.1063/1.1718538

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A semigraphical method is presented for evaluating the focusing conditions and the acceptance solid angle of quadrupole lens systems. The method is illustrated for a specific triplet magnetic quadrupole system for which the predictions are confirmed experimentally.

ISSN:0034-6748    

DOI:10.1063/1.1718539

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

X‐ray line profiles are measured fully automatically by means of a preprogrammed step scan. The intensity data are taken by means of the fixed count method and punched into paper tape by an electronic clock. The evaluation of the intensity data and the Fourier analysis of the line profiles is performed on an IBM 1620 computer.

ISSN:0034-6748    

DOI:10.1063/1.1718540

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A new instrument for obtaining induction times of explosives under vacuum and different atmospheres is described. The outstanding feature of the instrument is an automatic dropping mechanism which permits 50–100 ignition times to be determined without breaking the vacuum. Ignition times down to the millisecond range can be determined.

ISSN:0034-6748    

DOI:10.1063/1.1718541

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The absolute intensity of small‐angle x‐ray scattering has been measured by two methods—comparison with a beam transmitted through a series of similar attenuators, extrapolated to the case of no attenuators, and comparison with the scattering of air—with good agreement. Some reproducible substances are calibrated as standards at small angles and some also at larger angles, in the range accessible to the diffractometer. Brief interpretations are given of the small‐angle scattering; that of water is consistent with theory. The long‐range density fluctuations of vitreous silica are found to be mainly those frozen in at the glass transformation. The absolute scatterings are compared with Katz's unpublished small‐angle standardization and with Warren's standardizations of Lucite and vitreous silica by means of high‐angle scattering. Katz's measurements of silica and Warren's of Lucite are appropriate for quantitative comparison. They are about 2% higher and 7% lower, respectively, than the present result. Finally, the effect of impurities is derived.

ISSN:0034-6748    

DOI:10.1063/1.1718543

出版商:AIP    

年代:1963

数据来源: AIP