Multiple Counters Research Articles

A low-cost chromatograph data-collection system

A data collection system has been constructed, based on the low-cost BBC microcomputer, which provides for the digitization and storage of the data from one or more g.l.c. or h.p.l.c. instruments, or from other data sources with similar data rates. The data can be observed during collection on the graphics screen, and are then stored on disk for subsequent processing. This processing is designed to be interactive, so that the operator can influence decisions about base-line drifts, peak separations, etc. when integrating the peaks, and can decide which peaks are to be stored in a time/intensity record, on the basis of a visual display of the trace. A low cost multi-channel precision ADC, using isolated voltage-to-frequency transducers sited at the sources of data, and multiple counters at the computer, may be used to measure several signals simultaneously even when they originate at some distance from the computer, and extra memory can also be added to the BBC microcomputer to allow temporary storage of data. The software is written in machine code (for the data collection) and BASIC (for the analysis routines) so that modifications to the latter routines can be made easily. The user interface is suitable for routine users who have no computing experience.

The Counting Phase Detector with VLF Atmospheric Noise

The counting detector offers a simple means of making and averaging digital measurements of signal phase. However, use of the averages can lead to erroneous estimates if the signal has a low carrier-to-noise ratio. How to overcome this problem by using multiple counters is shown here. Characteristics for both Gaussian and impulsive noise are derived, and algorithms for estimating both phase and carrier-to-noise ratio are presented.

Design for a conventional high-resolution neutron powder diffractometer

The design considerations for a conventional neutron powder diffractometer are reconsidered. We find that the resolution can be improved to the limits imposed by the powder particle size, while the effective intensity can at the same time be increased by using multiple counters with the correct combination of seller divergences, monochromator mosaic spread, and take-off angle. With the profile technique for data analysis, this high-resolution diffractometer should permit the refinement of nuclear and magnetic structures having unit cells of up to 3500 A3 volume.

A Magnetically Pulsed Neutron Beam for Time-of-Flight Measurements of Inelastic Scattering

In many types of experiments, time-of-flight neutron spectrometers have the advantage of higher counting rates than crystal spectrometers, especially in view of the fact that multiple counters may be used. A method of magnetically pulsing a neutron beam has been developed that avoids the necessity of using high-speed rotating equipment. The magnetic intensity in a Bragg reflection depends on the orientation of the atomic magnetic moments relative to the scattering vector, and it becomes zero when the moments are directed along the scattering vector. The direction of magnetization in ferrite crystals can be switched rapidly with an external magnetic field so that these crystals can serve both as a neutron monochromator and pulser. Furthermore, the neutron pulse-width and repetition rate can easily be varied by changing the current pulse that produces the external field. The nuclear contribution for the (111) or (331) reflections can be made very small for 7Li-Ti ferrite of the correct composition. Large magnetic scattering intensities can be obtained in each case. The pulsed magnetic field is produced by switching the energy stored in a pulse-forming network into a magnet-drive coil by means of a silicon controlled rectifier. The pulse risetime is about 1 μsec and the pulse length in the present instrument is 12 μsec.

Characteristics of spark counters

The spark counter, operating as an α-particle detector, has been studied extensively both with respect to the corona current in a given gas, and for different gases. The performance of a single wire counter was first studied, and then the experiments were extended to multiple wire counters. Nitrogen showed good characteristics with a single-wire counter, but failed for multiple wires, whereas dry air showed the best characteristics with a counter with six wires.

Induced Discharge Phenomena on the Central Wires of Multiple Geiger Counters

Induced Discharge Phenomena on the Central Wires of Multiple Geiger Counters