Multichannel Pulse Height Analyzer Research Articles

High-rate X-ray spectroscopy in mammography with photon counting detectors using a limited number of energy bins

Direct measurement of mammographic X-ray spectra under clinical conditions can be useful for quality control (QC) in mammography for estimating image quality and patient dose. The measurement of mammographic X-ray spectra using the traditional detectors with multi-channel pulse height analyzer (MCA) systems is challenging because of the limitations imposed on measurements with high energy resolution at high photon counting rates, as well as geometrical restrictions, especially in a hospital environment. Semiconductor photon-counting detectors equipped with faster electronics enable utilization in somewhat high count rate situations at the expense of decreased energy resolution. This work presents a method for estimating mammography X-ray spectra from measurements acquired with a multi-energy bin photon counting detector. Simulation tests were conducted out for different incident X-ray spectra, energy thresholds and for multiple noise realizations assuming an ideal photon-counting X-ray detector with three energy thresholds. In addition, experimental measurements of mammography X-ray spectra were estimated by using a high-count rate Gallium Arsenide (GaAs) photon counting detector (with two or four energy thresholds) and a high resolution X-ray spectroscopy detector with Cadmium Telluride (CdTe) sensor for comparison. Differences between half-value layer values (HVL) obtained from the estimated spectra using the proposed method were found to be within 0.04 mm of the true values. This proposed method could be an attractive tool for laboratory research and calibration of photon-counting detectors.

Development of Digital Multi-channel and Time-division Pulse Height Analyzer Based on PXIE Bus for Hard X-ray Diagnostic in East

Pulse height analyzer (PHA) is an important component of hard X-ray diagnostic to measure energy spectrum in experimental advanced superconducting tokamak (EAST). In order to satisfy physics research of high parameters plasma, the energy resolution, time resolution and number of channels of PHA are required to be improved. A Multi-channel and time-division PHA (MTPHA) based on PXIe bus is designed using 16 bit ADC and FPGA as core processing unit, and has a maximum number of channel addresses of 4096 and minimum time resolution of 2 ms. The function of energy spectrum analysis is realized in the FPGA. Moreover, the PXIe communication drive is realized by combination of hardware code in FPGA and LabVIEW software in host computer. The MTPHA performance has been tested in the lab with pulse generator, 152Eu isotope radiation source and tested in plasma discharge of EAST. It is found in the lab that the full width at half maxima (FWHM) of MTPHA is no more than 2 channels, and the linear correlation coefficient R of pulse height and channel address is 1. In EAST, the MTPHA can work well and produce experimental data consistent with other diagnostics.

DETERMINATION OF THE URANIUM CONTENT IN SOME SOIL SAMPLES FROM AJAOKUTA, KOGI STATE: NIGERIA

This work present the Uranium (238U) content in soil samples collected in Ajaokuta from some villages was been determined. The measurement of the soil Uranium activity concentration were made using a multi–channel pulse height analyzer (Camberra series 10 plus) coupled to a 76.2mm x 76.2mm NaI (TI) scintillation detector. 2.93)The mean Uranium content in the analyzed samples was found to be (44.26 Bq/kg which is higher than the world mean value of 35Bq/kg. The results were in good agreement with others for soils from region which is considered as normal or slightly high in radioactivity level.

The mass attenuation coefficients, effective atomic numbers and effective electron numbers of some concrete containing barite for 511, 835 and 1275 keV gamma rays

The linear attenuation coefficients (μl) of concretes including barite fractions of 0%, 50% and 100% were measured at the gamma energies of 511, 835 and 1275 keV.The measurements have been performed using a low level gamma counting spectrometer including a 3”x3” NaI(TI) detector by ORTEC Inc., connected to a multichannel pulse height analyzer. Total mass attenuation coefficients, effective atomic numbers and effective electron numbers valuesf or concretes are calculated in the energy range from1keVto 100GeV. The values of mass attenuation coefficients used in calculations are taken from the XCOM. The results from the measurements were compared with the theoretically calculated results. The measured results of mass attenuation coefficients, effective atomic numbers and effective electron density were found to be in good agreement with the calculations.

MULTICHANNEL PULSE HEIGHT ANALYSER USING FPGA FOR DATA ACQUISITION

This document gives the description of a multichannel pulse height analyser which is implemented using FPGA technology for high speed data acquisition and analysis. Multichannel analysers (MCA) are used globally in various laboratories in the application of nuclear spectroscopy. The most common use of a MCA is to plot the energy spectrum or to find the decay rate of the radio material under test. In the following context we have described the designing of an open source multichannel pulse height analyzer which uses a high speed ADC for data acquisition and displays the output on a graphical user interface designed using labVIEW in a computer.

Determination of the energy dependence of the BC-408 plastic scintillation detector in medium energy x-ray beams

The energy dependence of the response of BC-408 plastic scintillator (PS), an approximately water-equivalent material, has been investigated by employing standardized x-ray beams. IEC RQA and ISO N series x-ray beam qualities, in the range of 40–100 kVp, were calibrated using a PTW-type ionization chamber. The energy response of a thick BC-408 PS detector was measured using the multichannel pulse height analysis method.The response of BC-408 PS increased gradually with increasing energy in the energy range of 40–80 kVp and then showed a flat behavior at about 80 to 120 kVp. This might be due to the self-attenuation of scintillation light by the scintillator itself and may also be partly due to the ionization quenching, leading to a reduction in the intensity of the light output from the scintillator. The results indicated that the sensitivity drop in BC-408 PS material at lower photon energies may be overcome by adding some high-Z elements to its polyvinyltoluene (PVT) base. The material modification may compensate for the drop in the response at lower photon energies. Thus plastic scintillation dosimetry is potentially suitable for applications in diagnostic radiology.

Analysis on the Impact of the Data Acquisition Board on the Performance Indicators of the Virtual Multi-Channel Pulse Height Analyzer

The DAB (Data Acquisition Board) is a key component of the VMPHA (Virtual Multi-channel Pulse Height Analyzer). In order to assist the design of the VMPHA, the influence of the DAB on the performances of the VMPHA has been studied through the method of theoretical analysis in this paper. The Sampling Rate, the LSB (Least Significant Bit) and the Data Transfer Rate of the DAB have decisive effects on the performance of the VMPHA. The Sampling Rate and the LSB are the two main factors that determine the energy resolution which is one of the most important performance indicators for the VMPHA. Another most important performance indicator for the VMPHA, the number of channels, is determined by the LSB alone. Moreover, the relationship among the three key performance parameters of the DAB is mutual influence. At the end of the paper, the selection method of the DAB for developing a VMPHA is summarized and presented.

Analysis on the Impact of the Data Acquisition Board on the Performance Indicators of the Virtual Multi-Channel Pulse Height Analyzer

The DAB (Data Acquisition Board) is a key component of the VMPHA (Virtual Multi-channel Pulse Height Analyzer). In order to assist the design of the VMPHA, the influence of the DAB on the performances of the VMPHA has been studied through the method of theoretical analysis in this paper. The Sampling Rate, the LSB (Least Significant Bit) and the Data Transfer Rate of the DAB have decisive effects on the performance of the VMPHA. The Sampling Rate and the LSB are the two main factors that determine the energy resolution which is one of the most important performance indicators for the VMPHA. Another most important performance indicator for the VMPHA, the number of channels, is determined by the LSB alone. Moreover, the relationship among the three key performance parameters of the DAB is mutual influence. At the end of the paper, the selection method of the DAB for developing a VMPHA is summarized and presented.

XRF시스템용 효율적인 Trapezoidal 필터 및 최대값 검출 회로 설계

XRF 시스템에서 디지털 방식으로 펄스를 합성하는 기술은 현재 다양하게 발전 되면서 기존의 아날로그 방식을 대신하고 있다. XRF 시스템에서는 펄스의 높이를 분석하기 위해 주로 trapezoidal 필터를 사용한다. 본 논문에서는 trapezoidal 필터의 하드웨어 구현을 위한 효율적인 구조를 제안한다. 또한 측정 오차가 기존 알고리즘에 의한 오차의 절반으로 감소되면서 효율적인 하드웨어 구현이 가능한 최대값 검출 알고리즘을 제안한다. 제안한 알고리즘은 하드웨어 언어인 Verilog HDL로 설계하고 FPGA로 구현하였으며 테스트보드를 제작하여 성능을 검증하였다.

252Cf fission-neutron spectrum using a simplified time-of-flight setup: An advanced teaching laboratory experiment

The removal of PuBe and AmBe neutron sources from many university teaching laboratories (due to heightened security issues) has often left a void in teaching various aspects of neutron physics. We have recently replaced such sources with sealed 252Cf oil-well logging sources (nominal 10–100 μCi), and developed several experiments using them as neutron sources. This includes a fission-neutron time-of-flight experiment using plastic scintillators, which utilizes the prompt γ rays emitted in 252Cf spontaneous fission as a fast timing start signal. The experiment can be performed with conventional nuclear instrumentation and a 1-D multi-channel pulse-height analyzer, available in most advanced teaching laboratories. Alternatively, a more sophisticated experiment using liquid scintillators and n/γ pulse-shape discrimination can be performed. Several other experiments using these neutron sources are also feasible. The experiments can introduce students to the problem of detecting the dark matter thought to dominate the universe and to the techniques used to detect contraband fissionable nuclear materials.

Tritium Water Monitoring System Based on CaF2 Flow-Cell Detector

For measuring the tritium concentration in water, a water monitoring system was developed. The monitoring system consists of a flow-cell detector, a pair of photomultiplier tubes, a circuit unit (including a high-voltage power supply and a coincidence counting module), a water flow pump and a multichannel pulse height analyzer. The flow-cell detector was fabricated using granular CaF2(Eu), which was solid scintillation materials. The performance of the water monitoring system was examined with three water samples containing different tritium concentrations of 10, 50 and 100 Bq/ml, and linearity between the count rate and the tritium concentration was examined. The results suggest that our system reasonably works as a water monitor for measuring low level tritium concentration. This system is the first such real-time monitoring system able to measure tritium concentrations in water continuously flowing through the solid scintillation detector.

Elemental 2D imaging of paintings with a mobile EDXRF system

Imaging techniques are now used commonly and intensively in cultural heritage object analysis. Nowadays, many different techniques in nature as well as many applications exist, where they can be applied. X-ray radiography and infrared reflectography as well as UV photography are some of the most applied techniques. The study of works of art usually requires these techniques to be non-invasive. Furthermore, they are frequently required to perform in situ analysis. A few years ago, our laboratory developed a mobile energy-dispersive X-ray fluorescence and UV-vis-NIR coupled spectrometer, especially designed for fieldwork studies, where all three techniques can be applied strictly at the same site of analysis. Recent developments on a new positioning system have now allowed us to perform 2D elemental mappings with our equipment, which is especially well adapted to painting analysis. The system control is carried out entirely through a laptop computer running a dedicated homemade software. The positioning is achieved by means of a CCD camera embedded in the system and controlled via a Wi-Fi connection through the computer. The data acquisition system, which is made through a homemade multichannel pulse height analyzer, being also managed via the software mentioned above, goes through an Ethernet connection. We will present here the new developments of the system and an example of in situ 2D elemental mapping applied on an anonymous oil painting on wood panel. The discovery of a hidden painting under this oil painting makes it a good choice for a first example of 2D large scan with a mobile instrument.

Rapid measurements of concentrations of natural uranium in process stream samples via gamma spectrometry at an extraction facility

A new application of gamma spectrometry in the efficient measurement of natural uranium in the process stream at an extraction plant is described here. The inherent nuclear properties of uranium viz. emanation of characteristic gamma rays (185.7 keV) has been exploited for the determination of concentrations ranging from 5 to 450 g l −1 by passive photon counting of 185.7 keV gamma rays from 235U isotope for a maximum of 3–10 min per sample. This technique is totally matrix independent unlike other instrumental analytical techniques like wavelength dispersive X-ray fluorescence spectrometry and UV–vis spectrophotometry. Solution samples of aqueous and organic phase can be directly counted without the requirement of sample preparation. A MINIM-based gamma spectrometer consisting of a multichannel pulse height analyzer and a 3 in. × 3 in. well-type NaI(Tl) scintillation detector with an approximately 2 in. thick lead shield has been employed for the measurements. The results are compared with those obtained by potentiometry and wavelength dispersive X-ray fluorescence spectrometry (WD-XRF). Relative standard deviation of 1–5% has been obtained depending upon the concentration of uranium, which is more than adequate for routine process control samples. This paper also discusses in detail the problems associated with the determination of high concentrations of uranium in using 63 and 93 keV gamma rays emanating from 234Th ( t 1/2 24 days) the immediate daughter of 238U isotope in samples that have attained secular equilibrium and the limitations of these energies in the routine analysis of freshly extracted uranium.

연료극 지지체식 고체산화물 연료전지용 고성능 공기극 제조 및 특성 연구

A rapid and simple method is described here for the determination of scandium in monazite by neutron activation analysis. The sample is irradiated for 20 hours at the neutron flux of thermal neutrons//sec in the TRIGA MARK Ⅱ reactor, after which the sample is decomposed by fusion with concentrated sulfuric acid. The scandium-46 together with scandium carrier are separated from the irradiated sample by precipitating with ammonia, and are extracted by solvent extraction of the thiocyanate complex into ether. The induced radioactivity is measured by gamma scintillation spectrometry using the Multichannel Pulse Height Analyzer connected with 22 NaI(Tl). The chemical yield is determined gravimetrically by precipitating scandium with mandelic acid. In order to check the efficiency of scandium separation and the errors from interfering activities of the other elements, scandium was separated by the cation exchange resin column, and the results from both samples were compared each other, which showed that the chemical procedure used in this work was as selective as the ion-exchange method with respect to scandium separation. The scandium contents in Korean monazite were found to be about 12 p. p. m.

PCGAP: Application to analyze gamma-ray pulse-height spectra on a personal computer under Windows NT®

PCGAP is a software code, which was written to provide gamma-ray pulse height spectrum analysis on a personal computer platform. The code was specifically developed for Windows NT for either an Intel® or DEC Alpha® based processor. PCGAP includes programs which can be used to control data collection using a Canberra INSPECTOR® multichannel pulse-height analyzer. With suitable spectrum conversion routines PCGAP can be used to analyze data from almost any multi-channel analyzer. Besides the normal functions associated with a robust spectrum analysis package, PCGAP can be used for radionuclide analysis for actinides via L-X and gamma-ray spectrometry. It can be used to control and analyze data from an INEEL developed pulse injection system for individual spectrum validation. The package includes programs for the manual analysis of spectra using displays which permit the spectroscopist to interactively define the spectral continuum and peak fitting limits, and display the resulting function fitting forms.

Microdischarge activity in vacuum insulating systems with Cu-coated ceramic spacers

This paper presents the measured results of microdischarge activity in a vacuum insulating system after deposition of a Cu layer on a ceramic spacer's surface. The frequency of occurrence vs. charge magnitude characteristics of microdischarges were obtained using a multichannel pulse-height analyzer. The parameters describing microdischarge intensity which were evaluated, included total and maximum charge of microdischarges, number of pulses and average charge of pulse. Relations between microdischarge intensity and voltage as well as time for various thickness of Cu-deposited layers were determined.

Development of high speed multichannel scalar using line memories

A high speed multichannel scaling mode time analyzer (MCS) for time of flight (TOF) experiments was developed by using high speed serial access memories and a personal computer. The MCS was composed of two memory banks, run alternately for each trigger. The channel width of the MCS was selected from 50 ns to 200 ns (4 stage). The count per channel per trigger signal was one, but the dead time for channel advancing may approach zero. The MCS was tested with linear accelerator (linac)-TOF experiments. The results agreed satisfactorily with the design goal. It was confirmed that the high speed MCS runs normally. A small discrepancy at high energy channels between the time spectrum of the MCS and that of the time-to-pulse-height converter (TPHC)-multichannel pulse height analyzer (PHA) time analyzer was observed. One of the reasons for the discrepancy was the uncertainty of the MCS start time after the trigger signal by linac because of asynchronous crystal oscillations with the linac trigger signal.

Simple System for Dual-Parameter Multichannel Pulse-Height Analysis

A dual-parameter multichannel pulse height analyzer has been simply constructed by use of two analog-to-digital converters, a digital input/output board and a personal computer. The control program for data acquisition and graphic display was written in an assembler. Stored data were promptly displayed on a monitor in both a contour and an isometric display. This system is simple to operate and applicable to any field of radiation measurement.

Student measurement of radon gas concentrations

A sodium iodide crystal connected to a multichannel pulse height analyzer card in a microcomputer is used to detect and analyze the progeny of radon gas present in the ambient air of several buildings. Relative levels are obtained in three buildings and an attempt is made at calculating absolute levels.

Electric strength of vacuum gap under various voltage conditions

Although the electric strength of vacuum gap under various voltage conditions has been discussed in many paper, research on this subject is still ongoing. The first page of our investigations was examining the prebreakdown state of vacuum gap under ac voltage excitation. Field electron emission in short vacuum gap (0–2 mm) and microdischarges in long vacuum gap (over 10mm) were analyzed. Field electron emission current was measured with an unbalanced hv bridge. Next, using voltage-current characteristics analysis, the parameters of field electron emission were obtained. The microdischarges phenomenon was monitored with a multichannel pulse-height analyzer. The relation between breakdown voltage and the parameters characterizing prebreakdown phenomena was then determined. Finally, the characteristics of electric strength under ac (50 Hz), switching impulse (250/2500 μs) and lighting impulse (1.2/50 μs) voltages were obtained. The investigations were carried out with CuCr contacts in a wide range of interelectrode distance (0.5–12 mm).