Abstract: In an apparatus for neutron-capture-based on-line elemental analysis of bulk substances, the control of neutrons which escape from the volume in which the analyzed substance is placed improves accuracy and reduces potential radiation hazards. The apparatus includes a neutron source, which exposes the analyzed bulk substance momentarily contained within the instrument to a flux of neutrons. The analyzed substance captures some of these neutrons by (n,.gamma.) reactions, producing prompt gamma rays which are detected to provide the composition measurement. The placement of neutron absorbers around the volume containing the bulk substance and the neutron source and the proper geometrical relationship between the various parts of the instrument provide this neutron control. The materials used in controlling escaping neutrons and in the instrument structure are chosen to avoid interfering radiations.

Abstract: An apparatus for analyzing the spectral data in an elemental analyzer measuring gamma rays arising from neutron capture in bulk substances is disclosed. The formation of optimally-weighted linear sums of the number of counts in various portions of the energy spectrum of neutron-capture gamma rays improves measurement accuracy in an apparatus for on-line elemental analysis of bulk substances. Within the apparatus, the analyzed bulk substance is exposed to neutrons, and neutron capture generates prompt gamma rays therefrom. A detector interacts with some of these gamma rays to produce electrical signals used to convert their energy spectrum to digital form by pulse-height analysis. A small computer uses this digitized spectrum to construct the weighted linear sums corresponding to at least one interesting element. Generally, several elements are measured, and the computer forms ratios between the elemental sums to provide relative concentration measurements which are independent of absolute counting rates.

Abstract: The active reduction of the number of analyzed events with pulse amplitudes which pileup has distorted improves measurement accuracy and response time in an apparatus for neutron-capture-based on-line elemental analysis of bulk substances. Within the apparatus, the analyzed bulk substance is exposed to neutrons, and neutron capture generates prompt gamma rays therefrom. A detector interacts with some of these gamma rays to produce electrical signals used to measure their energy spectrum by pulse-height analysis. Circuits associated with this pulse-height analysis also detect the pileup of the signals of two or more independent gamma rays using one or more of several techniques. These techniques include multiple outputs from a special amplifier-discriminator system, which has been optimized for low pulse-pair resolving time and may have adaptive thresholds, and the requirement that the relative amplitudes of the outputs of slow and fast amplifiers be consistent with a single event producing both outputs.

Abstract: An apparatus having a digital circuit containing a variable-modulus counter and a frequency source for rapidly cycling the variable-modulus counter through all of its states is used to produce a random sample from the set of digits through which the variable-modulus counter is cycling upon the actuation of a pushbutton-controlled sampling circuit. The sample is added to previous samples, if any, and displayed or may be cleared. A modulus selector is used to determine the modulus, or operating range, of the variable-modulus counter and may utilize any suitable commercial type device such as a rotary switch and logic gates. A synchronizer operates in response to the sample pushbutton to enable sampling counting at an appropriate instant of time.

Abstract: An improved system of circuitry for operating an electronic counter connected to a Geiger-Mueller (GM) tube or to a similar source of random pulses with an associated dead time making the system response linear at increased counting rates, includes an electronic one-shot device, an and-gate connected to a pulse counter, a second and-gate connected to an interval counter, and a frequency source for producing periodic clock pulses. When a GM tube is operated as a part of this system, it detects ionizing radiation by producing pulses at a rate proportional to the amount of radiation present. The one-shot inhibits further GM-tube pulses from entering the pulse counter for a fixed time selected to be somewhat longer than the maximum GM-tube dead time, and at the same time it inhibits further periodic clock pulses from entering the interval counter, automatically correcting the measured and displayed pulse count for dead time without regard to the precise value of the dead time of the GM tube or other pulse source.

Abstract: In a unipolar version of an analog-to-digital converter of low-level signals involving a self-zeroing current-to-frequency converter, which virtually eliminates the effects of voltage offsets at the input to the converter while avoiding large leakage currents, improved circuitry is provided in order to avoid paralysis of the converter which could be caused by small input currents or charges of polarity opposite to that of the normal signal current or by drifts in the converter input voltage which produce a negative-charge offset. The circuitry includes provision for the automatic introduction at the converter input of a relatively-large restoration current with the same polarity as the signal current, and this current can also be used for converter checking and calibration. One version of this circuitry involves exposing a junction diode at the converter input to light, causing it to act as a photodiode.

Abstract: A digital circuit determines the maximum frequency present in a first pulse train and indicates when a selected fraction of this maximum frequency is exceeded in subsequent pulse trains. The invention comprises a prescaler circuit for the purpose of reducing the frequency of the input pulse train to a level suitable for a digital period-measuring circuit; a digital period-measurement circuit that measures the period of the output of the prescaler and compares that measured value to a stored value; a frequency-multiplier circuit that produces the reference frequency used to measure the period in the period-measurement circuit; and a control circuit to operate the circuits in a first mode for storing a digital value representative of the maximum frequency present in the input pulse train, and in a second mode for comparing the frequency of subsequent pulse trains with the value stored in the first mode.

Abstract: An improved digital telemetering system for conveying information from a subsurface measuring device to a receiving station located at the other end of the cable used to lower and retrieve the measuring device is disclosed. The information being telemetered is converted into digital form within the subsurface measuring device and is communicated as digital numbers over the telemetry link for recording, display and interpretation at the receiving station. A single insulated wire within the hoist cable can convey all signals and the electrical power to the subsurface equipment. The outer sheath of the hoist cable provides the return circuit. A decoder circuit located within the surface equipment recovers the data and converts them to useful information. The system can be adapted to handle data from several sources simultaneously and can act as a communication link in both directions without the need for added conductors in the hoist cable.

Abstract: An improved system of circuitry for use in combination with an ionizing-radiation detector over a wide range of radiation levels includes a current-to-frequency converter together with a digital data processor for respectively producing and measuring a pulse repetition frequency which is proportional to the output current of the ionizing-radiation detector, a dc-to-dc converter for providing closely regulated operating voltages from a rechargeable battery and a bias supply for providing high voltage to the ionization chamber. The ionizing-radiation detector operating as a part of this system produces a signal responsive to the level of ionizing radiation in the vicinity of the detector, and this signal is converted into a pulse frequency which will vary in direct proportion to such level of ionizing-radiation.

Abstract: A method of measuring the duration of a discontinuous signal, which consists of groups of pulses with the duration of the gap between individual pulses in the same group being smaller then the time between groups, includes the steps of starting a time-measuring device at the time of arrival of the leading edge of the first pulse in the group whose duration is to be measured, copying the measured value from the time-measuring device without stopping that time-measuring device whenever signal gaps occur, storing each successive measured value until a timer examining the signal gaps determines that no signals have occurred for a preselected time, and displaying the measured value of the time copied from the time-measuring device at the last instant that the pulsating signal was present.