[en] A multiprocessor data acquisition system has been built to replace the single processor systems at the Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory. The multiprocessor system was needed to accommodate the higher data rates at IPNS brought about by improvements in the source and changes in instrument configurations. This paper describes the hardware configuration of the system and the method of task sharing and compares results to the single processor system

[en] A new position-sensitive time-of-flight neutron detection and histograming system has been developed for use at the Intense Pulsed Neutron Source. Spatial resolution of roughly 1 cm x 1 cm and time-of-flight resolution of ∼1 μsec are combined in a detection system which can ultimately be expanded to cover several square meters of active detector area. This system is based on the use of arrays of cylindrical one-dimensional position-sensitive proportional counters, and is capable of collecting the x-y-t data and sorting them into histograms at time-averaged data rates up to ∼300,000 events/sec over the full detector area and with instantaneous data rates up to more than fifty times that. Numerous hardware features have been incorporated to facilitate initial tuning of the position encoding, absolute calibration of the encoded positions, and automatic testing for drifts. 7 refs., 11 figs., 1 tabs

No abstract available

[en] Calorimetric assay, in combination with a gamma-spectrometer analysis of sample isotopic content, yields the total sample Pu mass. The technique is applicable to sealed containers and is essentially independent of sample matrix configuration and elemental composition. Conventional calorimeter designs employ large water-bath heat sinks and lack the portability needed by inspection personnel. The ANL air-chamber isothermal calorimeters are low-thermal-capacitance devices which eliminate the need for large constant-temperature heat sinks. These instruments are designed to use a feedback system that applies power to maintain the sample chamber at a constant electrical resistance and, therefore, at a constant temperature. The applied-power difference between a Pu-containing sample and a blank determines the radioactive-decay power. The operating characteristics of a calorimeter designed for assaying mixed-oxide powders, fuel pellets, and Pu-containing solutions are discussed. This device consists of the calorimeter, sample preheater, and a microprocessor-controlled data-acquisition system. The small-sample device weighs 18 kg and has a measurement cycle of 20 min, with a precision of 0.1% at 10 MW. A 100-min gamma-ray measurement gives the specific power with a precision of better than 1% for samples containing 1 to 2 g of plutonium. 7 figures, 4 tables

[en] The heart of each time-of-flight neutron scattering instrument is its complement of detectors and the associated encoding and counting electronics. Currently there are ten fully-scheduled neutron scattering instruments in operation at IPNS, with three more instruments under development. Six of these instruments use position-sensitive neutron detectors (PSDs) of various types. These PSDs include a 30 cm x 30 cm, ∼3 mm resolution, neutron Anger camera area PSD with ⁶Li-glass scintillator; a 2.5 cm dia, ∼0.7 mm resolution, microchannel-plate area PSD with ⁶Li-glass scintillator; a 20 cm x 20 cm, ∼5 mm resolution, ³He proportional counter area PSD; a 40 cm x 40 cm, ∼4 mm resolution, ³He proportional counter area PSD; a flat 25 cm long, ∼1.6 mm resolution, ³He proportional counter linear PSD; and 160 cylindrical ³He proportional counter linear PSDs, each of which is 1.27 cm in dia and 60 cm long and has ∼14 mm resolution. In addition to these PSDs, ∼750 standard cylindrical ³He proportional counters of various sizes are utilized on IPNS instruments, and ∼20 BF₃ pulsed ion chambers are in use as beam monitors. This paper discusses these various detectors and associated electronics, with emphasis on the instrumental specifications and the reasons for the selection of the different types of detectors. Observed performance of these detectors is also discussed. 19 refs., 5 figs., 2 tabs

[en] The equations governing the charge-division encoding of a position-sensitive detector, represented as a distributed resistance-capacitance line with realistic end loading, are developed and discussed. Sources of the differential nonlinearity in the position encoding are identified and related to characteristics of the dynamic load impedances, and four practical means for reducing or eliminating such nonlinearities are proposed. The various methods for reducing nonlinearities are evaluated both by numerical solution of the circuit equations and by testing with an operating position-sensitive neutron detector and encoding system. All measurements and calculations show close agreement with one another and with the theory. (orig.)

[en] The Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory is a major new user-oriented facility which has come on line for basic research in neutron scattering and neutron radiation damage. This paper describes the distributed-processing data-acquisition system which handles data collection and instrument control for the time-of-flight neutron-scattering instruments. The topics covered include the overall system configuration, each of the computer subsystems, communication protocols linking each computer subsystem, and an overview of the software which has been developed

[en] A stable isotope ratiometer-multiple ion detector (SIRMID) unit which can drive existing gas chromatograph-quadrupole or magnetic sector mass spectrometers to monitor up to six ions in turn is described. Each of the three pairs of ions can be selected for quantitation; thus three different or successive components can be analyzed in a single GC run. A background subtraction option permits the ion intensity in the absence of sample to be subtracted automatically during sample measurement. Displays of accumulated counts and isotope ratio are updated twice per second during the measurement and can be printed out at its conclusion. All six ions can be monitored in the analog mode by parallel outputs to a multipen recorder. Experience gained in the construction of this prototype indicates that SIRMID units could be commercially available for $10K, or about ¹/₃rd to ¹/₆th of the cost of even an inexpensive computer system. (U.S.)

[en] The Argonne National Laboratory has recently installed an activated barrier, the Access Denial System, to upgrade its security. The technology of this system was developed in the late 70's by Sandia National Laboratory-Albuquerque. The Argonne National Laboratory is the first Department of Energy facility to use this device. Recent advancements in electronic components provide the total system support that makes the use of an activated barrier viable and desirable. The premise of an activated barrier is that it is deployed after a positive detection of an adversary is made and before the adversary can penetrate vital area. To accomplish this detection, sophisticated alarms, assessment, and communications must be integrated into a system that permits a security inspector to make a positive evaluation and to activate the barrier. The alarm sensor locations are selected to provide protection in depth. Closed circuit television is used with components that permit multiple video frames to be stored for automated, priority-based playback to the security inspector. Further, algorithms permit look-ahead surveillance of vital areas so that the security inspector can activate the access denial system in a timely manner and not be restricted to following the adversaries' penetration path(s)

[en] The correlation technique at a pulsed neutron spallation source using a mechanical pseudo-random chopper is found to be technically feasible and can be accomplished with relatively minor changes to a conventional chopper spectrometer. The strong variation of resolution with incident energy is a serious disadvantage for some applications. There may be specific instances in which the method is advantageous to the conventional chopper at such a source, but these remain to be identified. 8 refs., 5 figs