摘要:

An apparatus for measuring the frequency decay of magnetically suspended freely spinning steel spheres is presented. A residual drag torque, which considerably exceeds the gas friction torque in ultrahigh vacuum, has been determined by means of a new measuring system for small frequency changes, which features high resolution power even at low rotor speed. The decay ratio−&ohgr;˙/&ohgr;has been recorded for several spheres with different diameters over a frequency range from 0.2 to about 105Hz. Apart from some characteristic deviations, which have been related to certain experimental conditions, a linear frequency dependence of the decay ratio−&ohgr;˙/&ohgr;=a0+a1r&ohgr;has been detected in the described apparatus (rbeing the sphere radius) witha0≃3×10−9sec−1anda1≃3×10−12m−1. An explanation is given for this type of drag torque. Measurements are reliable within ±6×10−11sec−1up tor&ohgr;≃700 m/sec. Stabilities better than ±5×10−12sec−1during one day have been recorded. A long term stability of the latter magnitude is required to verify the existence of an &ohgr;6proportional energy dissipation, which was deduced by Keith in 1963 from relativistic gravitational theories.

ISSN:0034-6748    

DOI:10.1063/1.1685224

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

An optically pumped resonance magnetometer has been constructed which utilizes4He gas as the resonant element in the self‐oscillator mode of operation. This instrument is capable of monitoring anomalies and fluctuations in the magnetic field with a sensitivity of 0.1 &mgr;G over the range of the earth's field (0.25–0.75 G). Recordings of variations in the geomagnetic field are compared with recordings made simultaneously with a servo helium magnetometer. The characteristics and advantages of the new system are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1685225

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Construction details are presented for a cold cathode pulsed gas laser which utilizes a plasma tube made from straight pieces of ordinary glass tubing. The laser features ease of construction with relatively low cost. Several gases may be used giving a wide spectrum of laser lines.

ISSN:0034-6748    

DOI:10.1063/1.1685226

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

An instrument utilizing free precession in the earth's magnetic field has been developed for studying the field dependence of nuclear spin relaxation in liquids. Both1H and19F nuclei are accessible to measurement. The method requires that a current be switched on in the sample coil for a certain time, reduced quickly to some smaller value, and later reduced suddenly to zero. The resulting sample magnetization then precesses about the earth's magnetic field, inducing a voltage in the coil which is amplified and displayed on an oscilloscope screen. The sample coil, current switching circuit, signal detection circuit, and timing circuits are described. The instrument is capable of measuring spin‐lattice relaxation times (T1) of 30 msec and up in fields ranging from 2 to 500 G; the range of measurable spin‐spin relaxation times (T2) is 10 msec‐1 sec in the earth's field of 0.54 G. The signal‐to‐noise ratio for a 450 ml water sample is greater than 700:1 at a bandwidth of 20 Hz. Estimated precision of the relaxation time measurements is ±3%.

ISSN:0034-6748    

DOI:10.1063/1.1685227

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A scale expander for analog signals is described in which the output is presented in the form of an integer voltage (the suppressed voltage) and a voltage representing the remainder of the input signal. Choice of the range (magnitude of suppression) is rapid and automatic. The instrument can be used, as an interface module, with a very wide variety of analog data systems. A few illustrative applications are given. Advantages in instrument performance over presently available circuits are documented.

ISSN:0034-6748    

DOI:10.1063/1.1685228

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A method of calculation of the electron energy distribution produced by various electrostatic spectrometers is applied to Marmet's monokinetron. Properties of this apparatus are verified and studied as functions of the main geometrical and electrical parameters in second order approximation. Electron motion calculations are performed from two dimensional considerations, but consequences of finite axial dimensions are studied. Results are in agreement with the experimental and theoretical determination of the resolution done by Marmet.

ISSN:0034-6748    

DOI:10.1063/1.1685229

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A wide band correlator based on an orthogonal expansion of the correlation function to be analyzed is described. The resultant correlation function is displayed on an oscilloscope screen in ``live'' time. A frequency band from some kilohertz to 1 MHz can be dealt with only by changing the time constant of analyzing orthogonal filters. Some discussions about truncation error of orthogonal expansions and a treatment for the case of periodic functions are described.

ISSN:0034-6748    

DOI:10.1063/1.1685230

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A high sensitivity detector system for microwave resonance measurements utilizing a bridge balancing method is described. This system consists of a parametron preamplifier, a phase modulated pump circuit, and a phase discriminator. The preamplifier amplifies the measuring signal and the quadrature AFC error signal alternatively.

ISSN:0034-6748    

DOI:10.1063/1.1685231

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A Zeeman modulated microwave spectrometer, specifically designed for K band rotational studies of gaseous free radicals and transient molecular species and using a Fabry‐Perot type resonator as the absorption cell, is described. The theoretical sensitivity of the system is shown to be comparable to that of the most sensitive waveguide cell spectrometers. The previously assigned spectra of OH and NO2radicals have been successfully located with the system. The utility of the system as a search spectrometer for free radicals has been substantiated by locating previously unreported spectra for the NO2molecule and NF2(difluoroamino) free radical.

ISSN:0034-6748    

DOI:10.1063/1.1685232

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The error analysis and the design of a 16‐bit binary digital‐to‐analog converter are discussed. This method of conversion switches binary weighted constant current sources into a summing junction, in this case the yoke of a CRT. A conversion linearity of 0.00025% and a stability of 0.0004%/h were measured for a full scale current of 1 A showing that a converter linear to better than 16 bits can be constructed requiring no trimming of components.

ISSN:0034-6748    

DOI:10.1063/1.1685233

出版商:AIP    

年代:1971

数据来源: AIP