Single Channel Pulse Height Analyzer Research Articles

Operating outdated EPMA (JXA-8600SX) by popular microcomputers and Windows PC

Here we report on the operation of the JEOL JXA-8600SX wavelength-dispersive electron probe microanalyzer (EPMA) after replacing the outdated and damaged native computers with popular and up-to-date microcomputers (Arduino) and a desktop Windows PC. Stepper motors actuating the sample stage and spectrometers are driven by computerized numerical control (CNC) kits commercialized for hand-made 3D printers, open-source firmware GRBL installed on Arduino, and a common text-based command “G-code” sent from a PC. X-ray pulse signals from the single-channel pulse-height analyzer (SCA) and analog signals from the probe ammeter are also acquired by Arduino. Sending commands from the PC to Arduino and receiving signals from Arduino to the PC are routinized by a homemade program coded by Visual Basic.NET. Quantitative analyses of anhydrous silicates and oxides, applying the Bence-Albee correction, provide reasonable oxide concentrations that are generally within 99-101 wt.% in total and compatible with stoichiometry within a 1%-2% relative deviation. This alternative control system not only extends the use of EPMA hardware regardless of generational changes in computer technology, but also introduces optional analytical techniques not available in the built-in system.

｀１２５´Ｉ用シンチレーションサーベイメータに対する漏洩磁場の影響

The effect of the weak leakage magnetic field on the response of a scintillation survey meter for 125I is studied. The counting rate and the magnetic flux density are measured on the planes above the surface of an analog meter. The meter produces the weak leakage magnetic field. With the presence of the magnetic field, the counting rate for background radiations increases, whereas that for radiation from 125I decreases considerably. The spectra of these radiations are observed to be shifted to the lower energy side. An amplification factor of the photomultiplier tube connected with the scintillator is reduced by the magnetic field. The variation of the counting rate is therefore ascribed to the shift of the spectra. When the main part of the spectrum enters the window set by the single channel pulse height analyzer of the survey meter, the counting rate increases. On the other hand, when the part leaves the window, the counting rate decreases. These results show that when radioactive contamination is checked with the scintillation survey meter, it is necessary to be more careful about the effect of the leakage magnetic field.

Radiation detectors in nuclear medicine.

Single-photon-emitting or positron-emitting radionuclides employed in nuclear medicine are detected by using sophisticated imaging devices, whereas simpler detection devices are used to quantify activity for the following applications: measuring doses of radiopharmaceuticals, performing radiotracer bioassays, and monitoring and controlling radiation risk in the clinical environment. Detectors are categorized in terms of function, the physical state of the transducer, or the mode of operation. The performance of a detector is described by the parameters efficiency, energy resolution and discrimination, and dead time. A detector may be used to detect single events (pulse mode) or to measure the rate of energy deposition (current mode). Some detectors are operated as simple counting systems by using a single-channel pulse height analyzer to discriminate against background or other extraneous events. Other detectors are operated as spectrometers and use a multichannel analyzer to form an energy spectrum. The types of detectors encountered in nuclear medicine are gas-filled detectors, scintillation detectors, and semiconductor detectors. The ionization detector, Geiger-Müller detector, extremity and area monitor, dose calibrator, well counter, thyroid uptake probe, Anger scintillation camera, positron emission tomographic scanner, solid-state personnel dosimeter, and intraoperative probe are examples of detectors used in clinical nuclear medicine practice.

Thermal neutron activation analysis of Cu in its ores by using an241Am−Be neutron source

A thermal neutron activation method has been developed for the determination of Cu in Cu−Pb−Zn ores and chalcopyrite ore concentrates using the reaction63Cu(N, γ)64Cu. The samples were irradiated with thermal neutrons from an241Am−Be neutron source and the annihilation γ-radiations of 0.511 MeV were counted on 3″×3″ NaI(T1) detector coupled with single channel pulse height analyzer. The method is nondestructive, economical and ideal for bulk analysis of ores with 1–16% Cu.

A gain monitor and calibrator for a single-channel pulse height analyser

A monitoring NIM module that visually displays the peak position and facilitates the calibration of the single-channel pulse-height analyser used in the counting of nuclear-radiation particles, has been developed. The module includes a visual 100-point bar graph array, which presents any peaks in a given spectrum with greater intensity than that of the background. A gating circuit that accepts the early or late generation of logic pulses from a single-channel analyser enables the display of the window to be set by the single-channel analyser.

マルチチャネル波高分析装置を用いた液体シンチレーション計数法の最適条件の決定

The method for determining optimum conditions of a liquid scintillation counter (LSC) for lowlevel counting of tritium was studied. To compare the lower limit of detection, the figure of merit EM/√B was used. The measurement system is a LSC connected with a multichannel pulse-height analyzer (MCA) . Both of tritium spectra and background spectra were searched for the condition that maximizes the figure of merit. The optimum condition obtained by using the MCA was fitted for a single channel pulse-height analyzer of the LSC. The figure of merit obtained by this method was 20.6% greater than that obtained by the balance point method.

In-Service Partial Discharge Testing of Generator Insulation

Progressive degradation of high-voltage generator insulation, whether due directly to the erosive effects of internal or slot discharge or to other debilitating factors such as heat and vibration, may be detected and monitored as a function of time by in-situ partial-dischargetests. This paper describes new diagnostic test techniques for assessing the condition of generator insulation with a minimum of service interruption. An improved means of coupling or data acquisition is described, as well as a versatile single-channel pulse height analyzer with characteristics a dequate for a field application of this type. Some typical test data are given. These studies were sponsored by the Canadian Electrical Association and are presented with their permission.

DNA-Umsatz im Ganzkörper tumortragender Mäuse

During the last 3 decades several authors have found in tumour-bearing animals an increase of synthesis and content of DNA in various organs which were free from neoplastic cells (Griffin, 1957;Kelly and Jones, 1950; Morgan and Cameron, 1973; Cerecedo et al., 1951; Lombardo et al., 1952). 5-iodo-2'-deoxyuridine (IUdR) is a thymidine analogue and specifically incorporated into DNA. When it is labelled with 125I or 131I it permits to reinvestigate these findings by measuring the rate of precursor incorporation into DNA and the rate of loss of labelled DNA in the living animal by means of counting the gamma emission from the incorporated iodine isotopes. In this paper, therefore, an attempt is made to analyse the DNA turnover in the whole body of liver tumour-bearing mice. 5-iodo-2'-deoxyuridine (IUdR) labelled with 125iodine was used as DNA precursor. It is a thymidine analogue 5% of which is specifically incorporated into the DNA of those proliferating cells which are in the phase of DNA synthesis at the moment of tracer application. Non-incorporated IUdR (about 95% of the injected amount) is rapidly degraded and excreted within 24 hours. The tracer remains bound to the cellular DNA druing the life span of the labelled cells. After cell death only about 5% of IUdR from DNA breakdown is reutilized. 125I has a half live of 60 days and therefore allows, over periods of weeks, external measurements of the DNA turnover in the living animal without disturbing the physiological environment. The measured loss of DNA-bound 125I reflects almost exclusively the turnover of the labelled cells. Female albino NMRI mice, 2 months old, bearing sarcoma-180 implanted into the right hind leg were intraveneously injected with 2 muCi 125I-UdR. At the time of injection, the tumour had reached in one group of mice an average volume of about 25 mm3 and in another group an average volume of nearly 850 mm3. When implanted into subcutaneous tissue sarcoma-180 rarely produces metastases in parenchymal organs, never in the spleen and--within the first 30 days after implantation--only in ca. 10% of the animals a small metastasis in a single lymphnode (Deodhar and Crile, 1969; Franchi et al., 1968). Whole body measurements were carried out immediately after tracer injection and then daily during the first week and every second or third day in the following 2 weeks in a NaI well counter with a single channel pulse height analyser. The tumour activity was also determined in vivo by a special counting device. In the normal mouse 4 to 6% of injected 125I-UdR is retained in the whole body 24 hours after tracer injection. During the following five days the 125I activity rapidly declines to 0.8% of that of day O immediately after injection. Thereafter the rate of loss of activity greatly diminishes (Fig. I). The first component of the turnover curve reflects an average daily cell loss of approximately 30% and involves about 90% of the incorporated activity...

Determination of iron and titanium in kaolins by the method of non-dispersive X-ray fluorescence

The possibility of application of the radioactive source excited X-ray fluorescence analysis for titanium and iron determination in kaolins to the routine test of the refinement process has been studied. The iron content can be determined with a simple counting system using a single-channel pulse height analyser, argon filled proportional counter and109Cd source of 3 mCi for the excitation of K Fe rays. The samples were analysed both as pellets and powders. The iron content ranged from 0.2–2.5% and titanium from 0.1–0.64%. For simultaneous determination of titanium and iron a Si(Li) spectrometer has been used. The238Pu source has been used for K Fe and K Ti excitation. It is the most convenient source for simultaneous determination of titanium and iron.55Fe is the most efficient source for the determination of titanium alone. The best values of precision and determination limit have been achieved for iron with238Pu and for titanium with55Fe.

Potential Errors in the Radioassay of 126I

The radioassay of very small 125I samples in both conventional and side-hole well crystals has been investigated. Using a multichannel analyzer, the source was counted at various positions within these well crystals. The effect of using a single-channel pulse-height analyzer was simulated by summing the counts over a 24-keV range across the primary peak, over a 30-keV range across the sum-coincidence peak, and over a 56-keV range across both peaks. In all crystals the primary peak was independent of sample position within the well over a range of several centimeters. The contribution of the sum-coincidence peak varied significantly with sample position in the conventional well crystals. With the side-hole crystal the counts contributed by the sum-coincidence peak exhibited a 2-cm plateau.

An inexpensive timing single channel pulse height analyzer

Described below is a simple design for a leading-edge timing single channel pulse height analyzer (SCA) which uses integrated circuits.

A dual source gamma ray traversing mechanism suitable for the non-destructive simultaneous measurement of bulk density and water content in columns of swelling soil

A traversing mechanism is described in which 100 mCi sources of americum-241 and caesium-137 are alternately brought into line with a sodium iodide (thallium) scintillation counter connected to a single-channel pulse height analyser equipped with two preset base lines. The equipment is capable of scanning a 10 cm diameter soil column equipped with sensors to a height of 200 cm, and facilities are provided for automatic indexing at preset intervals to an accuracy of 0.01 cm. Non-linear counting losses in the spectrometer system are described, and were found to be dependent on the window setting of the pulse height analyser. With the window setting adjusted to cover the apparent spread of the gamma peak, counting losses were negligible. Mass absorption coefficients of various materials were obtained using a compartmented box. Measured mass absorption coefficients of water, silica sand, and a chernozemic soil were 0.201, 0.247, and 0.303 cm2 g-1 respectively for americum-241, and 0.0826, 0.0746, and 0.0728 respectively for caesium-137. The precision of the apparatus was demonstrated by determining the moisture characteristic and bulk density characteristic of 0.5-1.0 mm aggregates of Narrabri soil during absorption and desorption. Gamma ray attenuation measurements and direct volumetric measurements were comparable. The standard deviations in the gamma ray measurements were found to be 0.03 g cm-3 for bulk density and 0.04 cm3 cm-3 for water content. Most of this inaccuracy arose from lack of precision in the americum-241 mass attenuation coefficient for the soil. By contrast, changes in moisture content and bulk density, at any level, of 0.004 cm3 cm-3 and 0.004 g cm-3 respectively, were statistically very significant.

A Fast Single Channel Pulse Height Analyzer for Precision Timing with Scintillation Counters

For fast precision time measurements with scintillation detectors zero, crossing synchronisation and fast energy selection on the current pulses from the detector seem in many cases to be the best choice. A fast S.C.A. has been developed giving both a zero crossing and a leading edge output for timing purposes. Input pulses are analyzed from 4 to 400 mA. The total time slewing of the zero crossing output is about 150 ps over the whole range of input amplitudes. Particular care has been devoted to the logic of the instrument, assuming always correct time information being carried by the output pulses. Measurements, performed with scintillation detectors, gave a best resolution of 190 ps using on both channels the zero crossing output and narrow energy selection. Good results have been obtained also with very wide energy selection.

Pulse height analysis of the falling characteristic in low frequency ozonizer discharge†

Pulses occurring in ozonizer discharges through nitrogen, oxygen and argon under 5O Hz, a.c. excitiition have been examined with a single channel pulse height analyser. A clipper circuit appropriately biased to blank out the 50 Hz background was designed to isolate the positive and negative pulses from one another. The charge associated with pulses of different heights, as also the total charge transferred by them to the eloctrodes at different applied voltages, was determined. The plot of the charge transfer versus applied voltage exhibits a negative slope over a voltage range slightly above the starting potential and about twice this value in all the three gases. The pulse height spectra indicate that, the formation of a positive space charge in the discharge space is associated with the falling characteristic.

Field measurements of thorium and uranium in lujavrites from the Ilímaussaq intrusion

During last summer 3388 field measurements of the thorium and uranium content of the lujavrites from the Ilimaussaq intrusion were carried out with a portable spectrometer (Løvborg, 1967; Løvborg et al. 1968; Løvborg et al. in press) consisting of a seintillation detector and a single-channel pulse-height analyser. Within selected small areas measurements were made at the joints of a 1m grid.

Electronic Collimation in Proportional Counter by Rise Time Discrimination

A method of electronic collimation in the proportional counter was developed and its performance examined. The method utilizes the difference in the rise time of output pulses. The rise time is converted into pulse height using a rise-time-to-pulse-height converter, followed by a single channel pulse height analyzer. Choosing the pulses of the fastest rise time one can selectively register the energies of the particles parallel to the center wire (anode). The method is applicable to gas recoil fast neutron spectrometers.

A single-channel pulse-height analyser with 100 nanoseconds resolution

A single-channel pulse-height analyser is described having a dynamic range of threshold and channel width of 200:1, and a signal resolution of 100 nsec. Channel position and width may be adjusted independently by internal or external means (external means by potentiometer or analogue voltage), the width being adjusted symmetrically or asymmetrically as desired. Temperature stability of channel position and width is better than ±0.005%/° C over the operating range -25 mV to - V. Paralysis may be preset over the range 0.1 to 50 μsec and an external strobe facility is provided to reduce time-walk. The instrument may also be operated as two independent discriminators (with internal or external control) sharing a common input terminal.

Electronic Collimation in Proportional Counter by Rise Time Discrimination

A method of electronic collimation in the proportional counter was developed and its performance examined. The method utilizes the difference in the rise time of output pulses. The rise time is converted into pulse height using a rise-time-to-pulse-height converter, followed by a single channel pulse height analyzer. Choosing the pulses of the fastest rise time one can selectively register the energies of the particles parallel to the center wire (anode). The method is applicable to gas recoil fast neutron spectrometers.

A Simple Pulse-Height Analyzer for Partial-Discharge-Rate Measurements

A single-channel pulse-height analyzer with suitable pulse-shaping circuits designed for partial-discharge measurements is described. The circuit of the pulse-height analyzer has a basic resolution limit of 1.5 μs. The unit may be used in conjunction with an RLC-type partial-discharge-detection circuit and is thus applicable to discharge measurements on high-voltage apparatus such as transformers, capacitors, and cables. Typical results, obtained with an artificial void simulated with metallic-dielectric electrodes, are presented.

A Single Channel Pulse Height Analyzer of Gain Sweep Type

Design and performance of a single channel pulse height analyzer of gain sweep type are described. The analyzer has a constant fractional channel width. The amplifier gain is varied discretely by a precision attenuator. When automatic operation of the analyzer is intended, pulses coming from a differential discriminator are counted by a storage counter and the dc output at the end of a cycle is held constant in the analog memory in the next cycle for the recorder display. Thus the spectrum is recorded in the histogram form.