摘要:

A microprocessor‐controlled instrument for measuring the concentrations of radon progeny in indoor air is described. The measurement technique is based on alpha spectroscopy and uses two counting intervals following a sampling period during which radon progeny are collected on a filter. The counting intervals are selected to provide optimal precision for measuring222Rn progeny for fixed total measurement times ranging from 30 to 60 min: concentrations as low as 0.5 pCi/1 can be measured with less than 20% uncertainty in 45 min. The instrument can also be used to estimate the potential alpha energy concentration of220Rn decay products. The device operates under the control of a computer or a data terminal and functions for week‐long periods between filter changes. The user can specify the sampling‐ and counting‐interval timing over a wide range and select from among several operating modes. A number of performance tests are also described indicating that for typical indoor concentrations the measurement uncertainty is dominated by counting statistics.

ISSN:0034-6748    

DOI:10.1063/1.1137555

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

We describe an apparatus capable of measuring the magnetic force on small liquid samples in high magnetic fields. The apparatus has been used to measure the magnetic susceptibility &khgr; of liquid He at pressures up to 3 MPa in high magnetic fields and has a sensitivity in such measurements comparable to superconducting magnetometers in lower fields. The performance was tested by measuring the atomic diamagnetism of liquid4He and liquid3He as well as the nuclear paramagnetism of liquid3He at 1.2 K in fields up to 15 T.

ISSN:0034-6748    

DOI:10.1063/1.1137556

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A fast, versatile, and inexpensive programmable digital pulse sequence generator (PSG) suitable for use in broadline pulsed NMR has been developed. Its features include 20 ns resolution of pulse duration, operation without direct computer supervision, and enough flexibility to produce essentially any pulse sequence. The architecture and construction of the PSG are discussed, and an example of its programming is presented.

ISSN:0034-6748    

DOI:10.1063/1.1137557

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Modification of a 1811A Hewlett–Packard time domain reflectometry (TDR) system is described for long‐time drift reduction. Triggering methods for single‐channel as well as dual‐channel TDR systems are discussed. It is shown that the long‐time drift of the 1024‐point incident signal is reduced to less than one discrete point over a period of several hours. This modification extends the upper frequency limit of a TDR system to about 10 GHz for precision permittivity measurements.

ISSN:0034-6748    

DOI:10.1063/1.1137558

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A design for a high‐temperature reactive scattering cell for atomic hydrogen and atomic deuterium is described. At approximately 2700 K a dissociation of the molecular target species of over 95% has been obtained. The lifetime of 340 h of operation is sufficient for precision, long‐time, differential cross‐section measurements.

ISSN:0034-6748    

DOI:10.1063/1.1137559

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A simple and inexpensive TV camera image combiner for several purposes in current video dual image acquisition is described.

ISSN:0034-6748    

DOI:10.1063/1.1137560

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

An improved x‐ray collimation system for diamond‐anvil high‐pressure cells is described. The usual practice of mounting the collimator directly in the diamond‐anvil cell is not followed. Instead, the collimator is mounted and aligned in a fixture which can be removed from the diamong‐anvil cell. The end of the collimator furthest from the sample can be fitted with a set of removable plugs, each with a different aperture. This collimation system is easily aligned, can be removed from the high‐pressure cell with no loss of alignment, and is inexpensive to construct.

ISSN:0034-6748    

DOI:10.1063/1.1137561

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A data logger using electrically programmable read‐only memory for data storage is described. The storage capacity is sufficient to record measurements from eight instruments at 30‐min intervals for almost ten days. This approach provides a moderately priced alternative to data loggers using magnetic tape or floppy disks when only modest data‐storage capacity is needed.

ISSN:0034-6748    

DOI:10.1063/1.1137562

出版商:AIP    

年代:1983

数据来源: AIP