摘要:

A high resolution, second‐order double‐focusing mass spectrometer has been constructed for the precise determination of atomic mass differences. The instrument has a mean radius of curvature in the electrostatic analyzer of 1 m and has operated with a resolving power at the base of the peaks of ∼200 000. Details of current operation are given. The best precision achieved to date is 2.5×10−9, corresponding to ∼250 eV atM= 100 amu; typical precision is ∼5×10−9.

ISSN:0034-6748    

DOI:10.1063/1.1684832

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The effect of static magnetic fields up to 210 kG on the characteristics of commercial germanium and platinum resistance thermometers was measured at various temperatures in the range 3.5–78 K. Measurements of the transverse (sample currentInormal to magnetic fieldH) and longitudinal (I∥H) magnetoresistance were carried out on both types of thermometers. A description is given of the dc resistance measuring technique used in these experiments. This method is a semiautomatic potentiometric scheme which increases the speed of measurement while maintaining high resolution and reasonable accuracy. The magnetoresistance of the germanium sensors was found to be large and orientation dependent over the temperature range investigated. These effects preclude the use of germanium elements, as presently fabricated, for temperature sensors in a high magnetic field environment. In the case of platinum resistance thermometers, the magnetoresistance at temperatures above 30 K is small enough so that it becomes practical to correct for it. In fact, these thermometers have been recently used in studies of the magnetic phase transitions in antiferromagnets in fields up to 200 kG.

ISSN:0034-6748    

DOI:10.1063/1.1684886

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A spectrometer shield for stray iron x‐ray radiation was devised and installed in the scanning electron microscope. A modification to the touch alarm was also made to make the system operative.

ISSN:0034-6748    

DOI:10.1063/1.1684843

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

An accurate method for determining the surface charge density on foil electrets is described. The method is based on the measurement of an induction charge on a capacitive probe parallel to, and at a certain distance from, one of the charged surfaces of the electret. The method does not interfere electrically or mechanically with the electret charges. It is simple to implement and capable of measuring surface charge densities from 5×10−11to some 10−6C/cm2. For a surface charge density of 10−8C/cm2, the reproducibility error is less than 1% and the systematic errors are estimated to be of the same order.

ISSN:0034-6748    

DOI:10.1063/1.1684847

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

An apparatus employing the spinning analyzer technique is described for measurement of Faraday and Kerr rotation in fields up to 20 kOe and at temperatures down to 3 K. Rotation angles are measurable to an accuracy better than 0.01° and are continuously recorded. The technique is extended to include measurement of Faraday and Kerr ellipticity.

ISSN:0034-6748    

DOI:10.1063/1.1684868

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

An ir radiometer utilizing a Golay cell was constructed to measure heat production in excised muscle preparations near room temperature. This radiometer resolves temperature changes of 1 mdeg on surface areas of several square millimeters with a lag time constant of a few milliseconds. It is shown that myothermic radiometry can provide an accurate measure of muscle temperature changes, with an ultimate time resolution below 0.5 msec.

ISSN:0034-6748    

DOI:10.1063/1.1684869

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The paper describes a system forming a precise nuclear quadrupole resonance (NQR) thermometer based on the resonance line of35Cl in KClO3. The system includes a transistorized Robinson oscillator for the detection of the NQR absorption signals. Details of the oscillator design are given and the method of detection of the NQR absorption signals through frequency modulation is described. The oscillator is locked to the NQR absorption line through a feedback loop including a phase sensitive detector. Conversion of frequency modulation to amplitude modulation in the amplifier section is partially avoided through the use of a second feedback loop which locks the amplifier tuning frequency to the oscillator frequency. An accuracy of the order of 0.003°C in temperature determination at liquid nitrogen temperature is obtained.

ISSN:0034-6748    

DOI:10.1063/1.1684870

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The design and performance of a set of coils for providing the field gradient in a Faraday type magnetometer are described. In contrast to systems which employ special pole caps for this purpose, these coils produce a gradient which is field independent, maintaining the high sensitivity of the Faraday technique at all fields. The facility of being able to adjust the gradient electronically is also shown to have several advantages. The coils described can produce a gradient as large as 485 Oe/cm in a region 3 mm high in which the gradient varies by less than ±0.1%. The magnetometer can detect absolute magnetic moments as small as 10−6–10−7emu.

ISSN:0034-6748    

DOI:10.1063/1.1684871

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A rocket borne solid state spectrometer was used recently during a solar flare to detect solar x‐ray emissions in the energy range 4–40 keV. The silicon detector, cooled by liquid nitrogen and incorporating an optical feedback preamplifier, is believed to be the first such detector used in this type of experiment. This paper evaluates the spectrometer and detection system under laboratory and field conditions, offering calibration data and some experimental results. Suggestions are made for future experimentation.

ISSN:0034-6748    

DOI:10.1063/1.1684872

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A technique for producing highly collimated beams of negative ions using apertures is discussed. The application of the method produced a 30 &mgr; diam H−beam with an angular divergence of 1.5 mdeg. The results of a study of the small angle scattering of protons from a carbon are presented. Other possible applications are outlined.

ISSN:0034-6748    

DOI:10.1063/1.1684873

出版商:AIP    

年代:1971

数据来源: AIP