Pulse Height Analysis System Research Articles

Simultaneous recording of true and random coincidences using a two-parameter analyzer system

A description is given of a simple fast coincidence method which allows the simultaneous recording of coincidence and random coincidence spectra. The method is based on the properties of a standard two-parameter pulse-height analyzer system, and no special electronics is required.

Simple technique for precise determinations of counting losses in nuclear pulse processing systems

A new technique has been developed to determine precisely the fraction of all counting losses suffered in counting and pulse height analysis systems. Of particular significance is the applicability of this method to time-dependent counting rates. The method is based on a technique in which the rate of radiation incident upon the detector is sampled continually. Upon the detection of a preset number of counts, a pulser signal is injected into the preamplifier. At the end of the experiment, the total number of injected pulses is compared with the number of these pulses that are recorded in the multichannel analyzer or scaler. Since the pulser peak suffers the same fractional losses as the spectral components of the detected nuclear events, such a comparison provides an accurate representation of the counting losses due to all loss-producing effects. These include losses incurred in ADCs, computers, pileup rejectors, etc. Losses suffered due to pileup may not be negligible compared with those due to the ADC and memory of fast multichannel analyzers. The application of this technique to constant counting rates, and to varying counting rates encountered in charged-particle-induced reactions and in radioactive-decay studies are treated in detail.

An inexpensive gain stabilizer controlled by a time-shared computer

An electronic pulse amplifier is described for automatic gain correction in high-resolution high-rate pulse-height analysis systems. The circuit gain is controlled by a PDP-7 computer devoting less than 4 ms per second of its time to provide gain correction signals for up to 8 ampliers. Necessary control voltages are developed in the computer's CRT display circuits and transferred to a “sample and hold” circuit associated with each gain stabilizer. Gain control is accomplished by adjusting the gate voltage of an FET which shunts a small fraction of the total signal.

ARMSPAN — [formula omitted]gonne [formula omitted]ultichannel [formula omitted]tored [formula omitted]rogram [formula omitted]alyzer

A pulse height analysis system based on a computer (DDP-116) with a memory of 4096 16-bit words has been developed. While the cost of the system is comparable to that of a conventional multichannel analyzer, its capabilities are far greater. The system features include single or 2-parameter pulse height analysis, software controlled servo-stabilization of gain and zero-intercept, digital bias, flicker-free interlaced display etc. The deadtime of the system is comparable to that of a conventional multichannel analyzer. Data are stored in 3000 memory locations and programs in the remainder. Basic functions such as ACCUMULATE, DISPLAY and READOUT are controlled by special front panel sense switches. Communication between operator and computer is in decimal. Data reduction programs include routines for determinations of centroids, fwhm and peak/total. Energies corresponding to unknown spectral peaks are computed by using the system's differential response to correct for non-linearity. Prompt calculations on the accumulated data provide the researcher with key parameters which enable him to determine whether the data is meaningful and he should proceed, or the run should be repeated. Similar calculations at a later time may result in inefficient use of time and experimetal facilities.

A simple system programmer for radioactive half-life measurements in the millisecond to second range

A simple electronically-pulsed relay driver is described. Its period is in the range 0.5–50 sec with a 2.5–97.5% duty cycle. The relay driver output controls a cyclotron, pulse height analyzer and detection system in a specific timing sequence for radioactive half-life measurement in the msec to sec range.

The statistics of digital stabilizers

Many pulse-height analysis systems include devices which continually readjust the gain of the system on the basis of digital information recorded in the pulse-height analyzer. The gain of such a system fluctuates because of the counting statistics. This effect is studied as a function of the parameters of the stabilizing system, and in comparison with the ability of the system to compensate for electronic drift.

Alpha-Particle Emission During Nuclear Fission at Moderate Excitation Energies

Protons, deuterons, and helium ions of various energies up to 42 MeV were used to induce fission in thin targets of ${\mathrm{Th}}^{232}$, ${\mathrm{U}}^{235}$, ${\mathrm{U}}^{238}$, and N${\mathrm{P}}^{237}$. $\ensuremath{\alpha}$-particle emission during fission was detected by a system of solid-state detectors coupled to a coincidence-gated pulse-height analysis system. $\ensuremath{\alpha}$ particles emitted prior to fission were distinguished from fission-accompanied $\ensuremath{\alpha}$ particles by the tight angular correlation between $\ensuremath{\alpha}$-particle and fission fragments which prevails in the latter case. It was found that the probability of $\ensuremath{\alpha}$ emission during fission is insensitive to excitation energy over the energy interval from about 5 to 38 MeV for a variety of heavy nuclei from thorium to plutonium. There is a suggestion that $\ensuremath{\alpha}$-particle emission is fractionally more probable for spontaneous fission than for fission of the same nuclei excited to energies \ensuremath{\ge}5 MeV. $\ensuremath{\alpha}$-particle emission in the fission of ${\mathrm{At}}^{213}$ (${\mathrm{Bi}}^{209}$+42 MeV $\ensuremath{\alpha}$) was detected, the probability of $\ensuremath{\alpha}$-accompanied fission being about $\frac{1}{3}$ of that for a typical thorium or uranium nuclide. A possible effect of angular momentum on the probability of $\ensuremath{\alpha}$ emission during fission was looked for by forming ${\mathrm{Pu}}^{239}$ in two different ways, the excitation energy being the same but the angular momentum being different. No significant effect was observed. A correlation between the energy of the $\ensuremath{\alpha}$ particles and the sharpness of their angular distribution relative to the fission fragments, which had been seen at lower energies, was observed here to hold as well at higher excitation energies. In an experiment to determlne whether a correlation exists between the probability of $\ensuremath{\alpha}$-particle emission and the mass ratio of the two heavy fission fragments, there is a suggestion that near-symmetric fragments have slightly less probability of emitting an $\ensuremath{\alpha}$ particle than asymmetric heavy fragments, although the effect is not very pronounced.

Multiparameter pulse height analysis programs

An extensive set of programs for a large computer has been developed to process the magnetic tape output of a small on-line computer. The two computers together constitute a very versatile general purpose multiparameter pulse height analysis system. The programs are written in the Fortran IV and MAP programming languages for the University of Iowa's IBM 7044 digital computer. The on-line computer is a CDC 160A.

Precision Measurements of Gamma-Ray Energies in the Region from 2.3 to 7.1 MeV

Precision energy measurements have been made on $\ensuremath{\gamma}$ rays in the region from 2.3 to 7.1 MeV by means of Ge(Li) detectors and a gain-stabilized pulse-height analyzer system. The transitions studied include certain non-Doppler-broadened $\ensuremath{\gamma}$ rays occurring in the reactions ${\mathrm{C}}^{12}({\mathrm{He}}^{3},p){\mathrm{N}}^{14}$, ${\mathrm{N}}^{14}(d,p){\mathrm{N}}^{15}$, ${\mathrm{N}}^{14}(d,n){\mathrm{O}}^{15}$, and ${\mathrm{F}}^{19}(p,\ensuremath{\alpha}){\mathrm{O}}^{16}$ and the $\ensuremath{\gamma}$ rays emitted in the radioactive decays of ${\mathrm{B}}^{12}$, ${\mathrm{C}}^{15}$, ${\mathrm{O}}^{14}$, and ${\mathrm{N}}^{16}$. In most cases energy calibrations were made with mixed sources and the extension to higher energies depended on the assumption of 1022.01 keV for the energy separation between full-energy-loss and two-escape peaks. The $\ensuremath{\gamma}$-ray energies in keV, with the nucleus from which they originate in parentheses, were determined to be the following: 2312.68\ifmmode\pm\else\textpm\fi{}0.10 (${\mathrm{N}}^{14}$), 2792.68\ifmmode\pm\else\textpm\fi{}0.15 (${\mathrm{N}}^{14}$), 4438.91\ifmmode\pm\else\textpm\fi{}0.31 (${\mathrm{C}}^{12}$), 5104.87\ifmmode\pm\else\textpm\fi{}0.18 (${\mathrm{N}}^{14}$), 5240.53\ifmmode\pm\else\textpm\fi{}0.52 (${\mathrm{O}}^{15}$), 5270.60\ifmmode\pm\else\textpm\fi{}0.46 (${\mathrm{N}}^{15}$), 5299.03\ifmmode\pm\else\textpm\fi{}0.43 (${\mathrm{N}}^{15}$), 6129.96\ifmmode\pm\else\textpm\fi{}0.46 (${\mathrm{O}}^{16}$), and 7117.02\ifmmode\pm\else\textpm\fi{}0.49 (${\mathrm{O}}^{16}$).

A Three Parameter Pulse Height Analyzer and Coincidence System for Satellite Cosmic Ray Studies

A cosmic ray experiment to be flown on an Orbiting Geophysical Observatory (OGO-E) consists of Cerenkov, scintillation, and solid state detector telescopes with associated electronics. Primary emphasis in this paper is placed upon description of the 256 channel pulse height analyzer and coincidence system electronics. Description of the three parameter system used for the scintillation telescope is emphasized since it is the most representative of the three telescope systems. A pulse height analysis is performed on each of the three photomultiplier tube outputs. Results are sent into the spacecraft data handling system. Circuits in the analyzer discussed in detail because of their improved performance over previously used circuits are a low noise charge sensitive amplifier, an RC pulse shaping technique, a delay line gated oscillator and a peak detecting circuit for pulse shape discrimination. In conjunction with the basic analyzer a coincidence system using a basic circuit for threshold discrimination and coincidence gating is described. Precise control of resolution down to 100 nanoseconds is obtainable.

Instrumental Requirements for High-Resolution Gamma-Ray Spectrometry Using Lithium-Drifted Germanium Detectors

Recent development of pre-amplifiers employing field-effect transistors have made it possible to achieve energy resolutions less than one kilovolt (FWHM) with lithium-drifted germanium gamma-ray detectors. This coupled with the availability of 4096-channel ADC's makes it possible to measure gamma-ray energies to better than 1 part in 104 over a reasonable energy range. To realize this degree of precision it has been necessary to re-examine all elements of a laboratory pulse-height analysis system. This includes linear amplifiers, ADC's, test pulse generators, and data storage and analysis techniques. To establish the limits of present state-of-the-art equipment for precision gamma-ray spectrometry, an extensive evaluation has been made of amplifiers, threshold amplifiers, gain stabilizers, and 4096-channel ADC's. Several noise sources exist that are amplitude and rate dependent, thus affecting energy resolution as a function of gamma-ray energy. These effects make it difficult to obtain accurate experimental measurements of the Fano factor for germanium. Recent measurements of the Fano factor obtained with a 4096-channel ADC, are presented. Techniques are described for the measurement of system linearity, stability, and dynamic performance of spectrometers under changing experimental conditions. The evaluation of analogue-to-digital converters has included their use both with conventional hard-wired pulse analyzers and programmed data processors. Precision pulse generators, methods for measurement of system linearity, and computer programs for data analysis developed to obtain precision values for energies and intensities of gamma rays in complex pulse-height spectra are described. Data are presented to demonstrate the precision which can be obtained with equipment presently available.

Osmotic adaptation of mouse lymphoblasts.

Abstract 1. 1. Osmotic adaptation in a tissue-cultured mammalian cell, the L5178-Y mouse lymphoblast, has been studied by means of an electronic cell counter coupled with a pulse-height analyzer system. 2. 2. It was found that these cells first swell and then ultimately return to normal size in various dilutions of medium. Also, cells remain viable after the temporary shock of these dilutions. 3. 3. An empirical equation has been computer-fitted to the data. A permeability constant for water has been obtained, 0.83 ± 0.05 μ 3 per min per μ 2 of cell surface per atm difference in osmotic pressure, which checks closely with other cells with the same surface-to-volume ratio of 0.55 μ −1 . Possible explanations for the swelling and shrinking phenomenon are offered.

System for automatically punching onto IBM cards the output of a 400-channel pulse height analyzer

The output typewriter drive of the RIDL 400-channel pulse height analyzer system has been adapted to drive the IBM Model 526 card punch without impairing any of the analyzer systems standard features. The card punch operates at close to maximum speed, stepping the analyzer along digit-by-digit by briefly closing the analyzer interlock. The analyzer “print” signal controls the starting and stopping of the punch exactly as in a typewriter readout. One 400-channel spectrum is punched onto 40 complete cards, which are also numbered serially and punched with an identifying tag, in approximately 3.5 min. No modifications are necessary on the card punch; a few interior signals must be brought to connectors or toggle switches in the analyzer system. One external chassis containing simple interlock and starting circuits and the serial-numbering device is used.

Sub-nanosecond timing with semiconductor detectors

A technique is described for achieving better than 1 nsec timing resolution in a semiconductor system, without degrading its energy resolution performance. The technique consists of transformer-coupling a fast amplifier and discriminator in series with a charge-sensitive amplifier, which is used as the first element of a pulse-height analysis system. (T.F.H.)

A study of the decay of V 48

The low excited states of Ti 48 have been studied by examining the gamma- and beta-ray spectra following the decay of V 48. The study utilized a double-focussing, √2 π beta-ray spectrometer and gamma-ray scintillation spectrometers with associated coincidence circuitry and pulse-height analysis systems. The energies and relative intensities of the observed nuclear transitions are 944.9±0.7 keV (9.8±0.9), 983.3±0.4 keV (100), 1311.7±0.6 keV (98.0±3.2), 2240.6±1.0 keV (2.9±0.2) and 2.64±0.02 MeV (0.04±0.02). By coincidence techniques, the 945, 1312 and 983 keV gamma-rays were established as the members of a triple cascade of nuclear transitions which originates at a newly found excited level at 3240 keV and ends at the ground state. The 2241 and 983 keV gamma-rays were observed to form a double cascade to the ground state. The 2.64 MeV gamma-ray has been assigned as the transition from a previously reported level at 3.62 MeV to the first excited state. As the result of an experimental determination of the internal conversion coefficient for the 945 keV transition, the multipolarity has been found to be predominantly M1, and a spin and parity assignment of (5+) has been proposed for the new energy level at 3240 keV. A level scheme which incorporates the findings of this study has been constructed for Ti 48.

Photodisintegration of the Deuteron with 94-Mev Bremsstrahlung Radiation

Differential cross sections for the reaction $\ensuremath{\gamma}+d\ensuremath{\rightarrow}p+n$ have been determined at laboratory angles of 45\ifmmode^\circ\else\textdegree\fi{}, 75\ifmmode^\circ\else\textdegree\fi{}, 90\ifmmode^\circ\else\textdegree\fi{}, and 135\ifmmode^\circ\else\textdegree\fi{} for laboratory photon energies from approximately 50 to 90 Mev. At each of the above angles the energy spectrum of the recoil protons was determined with a counter telescope and a pulse-height analysis system. The low cross section for this reaction necessitates the reduction of background to a minimum. This was accomplished by the use of a gaseous target and a particle selection technique. The differential cross sections and the estimates of the parameters describing angular distributions are in reasonable agreement with recent calculations by de Swart and Marshak and by Zernik, Rustgi, and Breit.

A Non-Dispersive X-ray Fluorescence Unit for the Analysis of Biological Tissue Sections

AbstractAn X-ray fluorescence analysis unit has been designed and built especially for the measurement of certain mineral elements in individual biological tissue sections. Such a section may contain in the neighborhood of 10-10 grams of an element of interest, in a concentration in the range of 1-100 p.p.m.The unit consists of a special high-power X-ray tube with a builtin interchangeable secondary radiator, which irradiates the speciman with the characteristic lines of the radiator element) and a proportional counter and pulse-height analyzer system, which provides analysis of the X-ray spectrum emitted by the specimen. Because the emitted spectrum is greatly simplified by the use of an appropriate radiator element, a diffracting crystal can be omitted, permitting a great increase in absolute sensitivity.The system is feasible only because of two peculiarities of our biological specimens: they are so thin that matrix effects are negligible, and they consist essentially of a few mineral elements in a light matrix.Design considerations, calibration procedures, procedures for the analysis of the observed proportional counter pulse-height spectra and results to date will be discussed.