Pulse Height Analysis System Research Articles

Spectroscopic diagnostics on JET (invited)

The present spectroscopic diagnostics on Joint European Torus (JET) consist of bolometry, fiber- and close-coupled visible spectroscopy (200–700 nm), as well as survey (10–170 nm) and spatial scan VUV spectroscopy (10–250 nm). Visible bremsstrahlung is used routinely for Zeff measurements. Hydrogen and impurity influxes from walls, limiters, and rf antennas are derived from visible spectral lines. Visible charge-exchange spectroscopy, utilizing part of the JET heating beams, yields ion temperatures, rotation velocities, and impurity concentrations in the plasma. VUV spectroscopy is employed for measuring the impurity content in the bulk plasma using an impurity transport code. Spatial scan spectrometers allow verification of the transport models by means of recorded emission shells. A 20-m-high resolution crystal spectrometer yields ion temperatures and rotation velocities from the He- and H-like resonance lines, as well as other plasma parameters. A pulse-height analysis system covers the energy range of metal and Cl-K lines and can be used for electron temperature measurements. In the near future XUV (0.7–35 nm) and double-crystal spectrometers (0.1–2 nm), one of them providing a spatial scan, will be available, enabling studies of H- and He-like light impurities, as well as Ne-, He-, and H-like metals. Bolometry, visible spectroscopy, and two crystal instruments will be the only diagnostics left during the JET active phase. By then, models and methods must have been established for assessing the behavior of the important impurities C, O (,Be), and Ni with these diagnostics.

Idealized pulse pileup effects on energy spectra

The energy spectrum containing the effects of all orders of pulse pileup is predicted for an idealized X-ray pulse height analysis system measuring randomly occurring events. Two simplifying assumptions used are (1) a fixed pulse resolution time, and (2) that the measured energy of piled-up pulses is the algebraic sum of the energy associated with each pulse.

A simple automatic deadtime loss correction system for particle counting processes induced by ion beams with fluctuating intensities

Pulse height spectra of signals arising from particles induced by ion beams must be recorded using a digitizing current integrator rather than a time clock so as to cancel the effects of the unavoidable current fluctuations. The latter also have a bearing on the dead time loss processes. The various loss correction procedures will be examined. It will be shown in particular that “live time” type corrections are valid only for constant counting rates. A simple system is presented which corrects automatically for dead time losses in the presence of counting rate fluctuations. This device may be coupled readily to any pulse height analysis system used for experiments with accelerators.

Simple dead-time and pile-up correction technique using a gated periodic pulse train

In a pulse-height analysis system using a gated periodic pulse train for the correction of counting losses, it is shown that both the dead-time and pile-up losses can be corrected for if the clock pulses have the same width as the so called true pile-up time of the pulse processing system, and the clock pulses are rejected from the pulse train if a coincidence between the shaped clock pulses and the busy time of the system is detected. The technique was tested both with random-pulse generators and a Ge(Li) detector ( 60Co and 137Cs sources). At counting rate up to 50 kHz, it is shown that the correction was accurate to ± 1%.

Memphis a Modular Experiment Multiparameter Pulse Height Instrumentation System

A modular expandable multiparameter pulse height analyzer system for up to 16 ADC's has been developed. Certain computing functions which have been implemented in hardware allow on line data acquisition and manipulation making use of parallel processing at high event rates (> 2 × 104 pulses/sec) at an event word length up to 128 bits. The system can be easily interfaced to 16 and 32 bit computers (VAX 11/780) by a special CAMAC buffer module. Single parameter information is incremented and stored in 8K CAMAC memory modules, which can be read and displayed by a CAMAC compatible dataway operation allowing direct memory addressing.

PDX Divertor operation

PDX was brought into operation in January 1980 as a diverted tokamak with typical parameters of B T = 15–20 kG, a = 38 cm, R 0 = 123–159 cm, I P = 180–300 kA, q ~ 3.7, n ̄ e = 1–3.8 × 10 13 cm −3, Z ̄ = 1.1–3, t es ~ 25 ms , and pulse lengths up to 0.7s. Internal vacuum components that were exposed to the plasma (such as limiters, shields, microwave horns, etc.) were fabricated from 99% pure titanium. Glow discharge cleaning with 3 × 10 −2 Torr H 2 and pulse discharge cleaning were used to condition the vessel for high power discharges. For the divertor studies, work has concentrated on obtaining long, high current stable discharges. Radial position, plasma current, and gas injection control systems have been used to facilitate this effort. Discharges of inside-D, square, and inverse-D cross-section have been produced. Microwave interferometers, spectroscopy, an X-ray pulse height analyzer system, scanning and fixed bolometers, and thermocouple array have been used to determine plasma and impurity densities, temperature, radiation, and power loss to the divertor. A comparison of diverted and undiverted discharges is presented.

Distribution of chemical elements in the cellular and extracellular components of the stomach and duodenum of rats

Electron-probe x-ray microanalysis was performed on freeze-dried sections, 4 μm in thickness, of the walls of the stomach and duodenum of Sprague-Dawley rats by using a scanning electron microscope equipped with an energy dispersive x-ray detector and a pulse-height analysis system. Comparable cellular and extracellular components, i.e., the luminal epithelium, lamina propria, muscularis mucosae, submucosa, tunica muscularis, and serosa of the stomach and duodenum were probed with an electron beam using an acceleration voltage of 15 kV. This results in the emission of x-rays that are characteristic of the elements present in the volume probed. Six elements of biologic interest were detected, specifically Na, Mg, P, S, Cl, and K. Based on the peak /continuum ratios for these elements, relative concentrations were measured for each of the probe sites. The findings indicate significant differences exist between the relative amounts of Na (P < 0.01) and Cl (P < 0.001) in the submucosae of the stomach and duodenum. Also, between successive layers of the walls of the stomach and duodenum there are apparent differences in the relative concentrations of certain elements. Concentration gradients for Na, Cl, K, and P are apparent between the mucosal and serosal surfaces of these organs. Other elemental concentration and gradient differences are seen between and within the walls of the stomach and duodenum. Furthermore, these studies indicate that different cellular and extracellular probe sites in the stomach and duodenum show different spectral profiles due to subtle differences in peak intensities of the various elements. The findings of the present study suggest that electron-probe x-ray microanalysis might provide useful information on the relative distribution and concentration of chemical elements concerned with the physiologic processes of the gastrointestinal tract.

Directional-correlation results for 134Ba and 110Cd using a megachannel gamma- gamma coincidence system

The development of high-resolution Ge(Li) detectors has created a need for gamma-ray coincidence analysis systems able to process and store the large quantities of data generated. We describe a megachannel pulse-height analysis system that can sort and store these data on line. This is accomplished using a 32K-word PDP-8/E minicomputer and two moving-head disks that provide a storage capacity of 2 18 events at any of 2 20 data locations. An X-or Y-pulse-height spectrum, in coincidence with one to four arithmetically combined pulse-height peak and background windows, can be assembled for CRT display and spectral analysis within 2–20 s. The rapid recovery of data allows convenient set-up and monitoring of experiments and anlyysis of the accumulated data. To test the performance of the system, we made directional-correlation measurements on gamma-ray cascades in 134Ba and 110Cd. Analyses of these data gave E2/M1 mixing ratios that for most transitions agreed well with published results. Using this system with its improved energy resolution and data processing capabilities, we obtained new E2/M1 mixing ratio results of 13.3 ± 2.1 for the 563 keV transition in 134Ba and −1.24 ± 0.20 for the 1505 keV transition in 110Cd.

The use of logarithmic pulse height and energy scales in organic scintillator spectroscopy

The use of logarithmic pulse height and energy scales is advantageous for organic scintillator neutron spectroscopy, providing an expanded dynamic range and economy of computer usage. An experimental logarithmic pulse height analysis system is shown to be feasible. A pulse height spectrum from a neutron spectrum measurement has been analysed using linear and logarithmic scales; the latter reduced the computer storage requirements by a factor of 13 and analysis time by 8.7, and there was no degradation of the analysed spectrum. Most of the arguments favouring use of logarithmic scales apply equally well to other types of scintillation spectroscopy.

A 16-channel analog store and multiplexer unit

A 16-channel analog store and multiplexer unit is described. The unit enables storing and selection of analog information which is then digitally encoded by single ADC. This solution becomes economically attractive particularly in multidetector pulse height analysis systems.

A computerized pulse-radiolysis system

The construction of a computerized pulse-radiolysis system is described, employing an adapted multichannel pulse height analyzer system and an electron accelerator operating on a 25 Hz frequency. As a test for the performance the absorption spectra of e aq − and (CNS) 2 −, together with the kinetics of the formation of (CNS) 2 − in aqueous solution were measured and compared with the published data.

A megachannel γ-γ coincidence system using a PDP-8/E computer and moving-head disks

A megachannel pulse-height analysis system using a PDP-8/E computer and two moving-head disk memories has been developed. The system has a storage capacity of 220 memory locations, is capable of processing 1100 events/s, and provides on-line sorting and disk storage. An X- or Y-pulse-height spectrum in coincidence with one or several arbitrary pulse-height windows can be assembled in core for scope display and spectral analysis within 2 to 20 seconds. Reconstruction of a complete X- or Y-pulse-height spectrum requires about 3 minutes.

A Second-Generation 1024-Channel Portable Gamma-Ray Spectrometer

Following the successful design in 1974 of a 256-channel battery-powered pulse-height analyzer system, we have completed a second-generation analyzer with advanced features, lighter weight, and more rugged construction. The 17-kg analyzer includes a NaI detector and is packaged as a small suitcase; it has high stability and accuracy to allow use over the temperature range from -30 to +70°C. The waterproof unit has many features not found on any commercial unit to allow sophisticated analysis by non-electronics oriented personnel. Its 36-button keyboard will allow manipulation of multiple spectra, integrations, and expanded energy scale with readout in keV. If its self-contained SX70 display camera is not sufficient for record keeping, the unit will telemeter all data onto analog tape or send to a remote computer via phone coupler.

Double internal bremsstrahlung in electron capture

Double internal bremsstrahlung has been observed in the electron capture decay of 37Ar. The energy distribution of the two photons has been investigated, using a dual parameter pulse-height analysis system, at an angle of θ = 90° between two photon propagation vectors. For sum photon energies in the interval of 210–810 keV and at θ = 90° the ratio of the transition probabilities of double to single bremsstrahlung emissions was found to be (4.8±0.4)×10 −5.

Carbon/Oxygen (C/O) Logging Instrumentation

Abstract An instrument system has been developed for field measurement of the relative carbon content of reservoir rocks. Gamma rays produced by inelastic scattering of 14-MeV neutrons are detected and analyzed in a sophisticated scintillation spectrometer system adapted for routine commercial well logging. A pulsed-neutron source similar to those in commercial use for other nuclear logs is employed. A van de Graaff generator provides the accelerating voltage to initiate the deuterium-tritium reaction, which produces the neutrons in a specially designed ion acceleration tube. Pulses from the radiation detector are transmitted to the surface oiler a conventional seven-conductor logging cable without degrading the spectrum. The log is available on a limited commercial basis and is recommended for identifying oil-saturated zones in cased wells where formation water is too fresh for reliable application of the Neutron Lifetime Log. Introduction A practical method of identifying the element carbon and assaying its abundance in cased-off formations has long been sought as a means for finding oil in situ. Since oil is largely composed of carbon, a measurement of carbon concentration is a direct method of evaluating the oil content of a formation. A nuclear logging technique whereby such a measurement can be made has been known since about 1950, and much effort has been expended in many laboratories to develop a system that could be used commercially to evaluate the hydrocarbon saturation of potentially productive reservoir rocks. Such a system is now available and has been field tested with gratifying results. This paper concerns the general features of the system, which is presently in commercial use on a limited basis. FIELD INSTRUMENTATION The subsurface instrument is 3-5/8 in. in diameter by 14 ft long. It is rated for a maximum temperature of 350 degrees F and pressure of 15,000 psi. It is equipped with a collar locator to enhance the accuracy of depth correlation and it can log to 7 ft above bottom. One or more neutron-type curves can also be run to assist in correlation with available open- or cased-hole logs. The instrument operates on a standard seven-conductor logging line, and curves are recorded on a conventional strip-chart recorder. Measurement of carbon-to-oxygen ratio can be recorded as a continuous curve vs borehole depth when desired. In usual practice, a continuous curve is of little value because statistical fluctuations in the measurement tend to obscure the true character of me log. For best results, stationary measurements are made at preselected points of interest. These are made for a time interval of 1 to 10 minutes each, depending on the accuracy desired and the number of zones to be surveyed in the time available for the logging operations. Typically, a logging operation comprises a continuous "correlation curve" over all zones of interest plus a station measurement at each of 10 to 50 specific points. PRINCIPLES OF OPERATION PRINCIPLES OF OPERATION The logging system comprises a subsurface instrument equipped to initiate and detect radiation from carbon, and surface gear to analyze and record the amount of such radiation in a format that facilitates formation evaluation. To initiate the emission of radiation, a source of 14-MeV neutrons is required. To detect the radiation, a scintillation spectrometer is used. And to assay the abundance of formation carbon by analyzing the detected radiation, a multichannel pulse-height analyzer system is employed. SPEJ P. 463

Pulse-height analysis of a large counter system

The logical units for the control of a pulse-height analysis system of a 648-counter hodoscope spectrometer are described. The CAMAC system is used to accumulate the experimental data, measure the counter high voltages, test the linearity and stability of the pulse-height encoders, and test the scalers under simulated experimental conditions.

A Versatile Data Processing System for Nuclear Gamma-Rays Spectroscopy with a Minicomputer

A versatile data-processing system using a mini-computer USC-3 has been developed for nuclear gamma-ray spectroscopy with Ge(Li) detectors. In order to perform data analyses in a conversation mode more easily and rapidly a light-pen system was constructed and connected to the USC-3 computer. The light-pen system made with a photo-diode and TTL digital IC's was designed so as to be applicable to any computer-aided pulse-height analysis system. The gamma-ray spectrum data are analyzed with the aid of the light-pen system and software programs in the assembler language. The spectrum analysis programs mainly consist of the smoothing of the original data, the automatic search for peaks in the spectrum and the evaluation of the peak positions and areas after background subtraction. The design principle and the circuits of the light-pen system and softwares for spectrum analyses are described.

A real-time 448 000-channel multiparameter pulse-height analysis system

A multiparameter pulse-height analysis system, operating on a small multiprogrammed computer with auxiliary magnetic disk memory, has been developed. The method enables experimentalists to collect data in arrays up to 448 000 channels, at coincidence rates of over 300 per second. The data may be viewed as it is collected, and is ready, in histogram form, as soon as data-collection is completed.

A technique for investigating continuous photon distributions

Abstract A technique which is suitable for investigating photons with a continuous energy distribution is described. The experimental arrangement involves a Compton spectrometer with the two detectors of the spectrometer operated in a two dimensional pulse height analysis system. The technique is applicable to photon energy regions above 50 keV.

A Computer System for Multiparameter Pulse Height Analysis and Control

A multiparameter pulse height analyzer and computer control system is described. Features include individual peak hold detectors with a time-shared ADC front end driving a PDP-9 computer to measure time-of-flight and light intensity from 12 scintillation counters around the 40-inch hydrogen bubble chamber.