Determination Of Dead Time Research Articles

A new dead-time determination method for gamma-ray detectors using attenuation law

This study presents a new dead-time measurement method using the gamma attenuation law and generalized dead-time models for nuclear gamma-ray detectors. The dead-time of the NaI(Tl) detection system was obtained to validate the new dead-time determination method using very thin lead and polyethylene absorbers. Non-paralyzing dead-time was found to be 8.39 μs, and paralyzing dead-time was found to be 8.35 μs using lead absorber for NaI(Tl) scintillator detection system. These dead-time values are consistent with the previously reported dead-time values for scintillator detection systems. The gamma build-up factor's contribution to the dead-time was neglected because a very thin material was used.

A simple method for rapid calibration of faraday and ion-counting detectors on movable multicollector mass spectrometers.

Methods are presented for rapid determination of relative efficiencies of Faraday cups in a multicollector array with movable cups and of Daly or electron multiplier detector dead time and gain values. The Faraday calibration approach is based on measuring the same isotopic ratio in two sequences with different collector configurations having one collector in common. Changes in thermal fractionation during the two measurement sequences are monitored using the same two collectors. Since the relative efficiencies are determined by measuring the same ratio in different cups corrected for time-dependent changes in fractionation, it is unnecessary to use a standard of known composition and calculations are simple, not requiring the solution of multiple equations. Determination of dead time and gain values for a Daly detector are shown based on multidynamic measurements of masses 207, 206, and 208 from Pb standard SRM982 in two sequences consisting of L1-Daly-H1 and Daly-H1-H2. This provides two equations that can be solved for Daly dead time and gain. This method uses static measurements and is therefore insensitive to signal instability. It also does not require use of a standard of known isotopic composition. The potential of using known cup efficiencies to help determine absolute isotopic abundances is discussed.

Dead time determination of 2-alkanone homologues series using methanol/water eluent in high performance liquid chromatography system by indirect method

The calculations of the dead time have been done in High Performance Liquid Chromatography System using spreadsheet method. The dead times produced by spreadsheet method were compared to the dead times of iteration method. The dead time were calculated using retention time and carbon number of 2-alkanone that eluted in several eluent composition of methanol/water. The dead time value generated by spreadsheet method shows the dead time value with equally good criteria to iteration method in generating the dead time value as low as possible, where the standard deviation of dead time value against the change of eluent composition is relatively low and the plot linearity of ln(k′) vs nC is shown to be good.

A Study on the New Development for Determination of Dead Time in GC-OTC/FID

A Study on the New Development for Determination of Dead Time in GC-OTC/FID

Linearity testing and dead-time determination for MC-ICP-MS ion counters using the IRMM-072 series of uranium isotope reference materials

The IRMM-072 series of reference materials is applied to perform linearity testing and dead time determinations for the ion counters on two MC-ICP-MS mass spectrometers at the IAEA.

Determination and Evaluation of Dead Time for X-Ray Fluorescence Spectrometer

When an X-ray photon which is generated by the sample enters into the detector, pulses can be produced and recorded. The detector is unable to respond to another photon that enters at the same time when a photon is being detected. The time that the detector takes to respond to a photon is regarded as dead time. For the x-ray fluorescence detector, the recorded count is less than the real count impulse due to dead time. Hence, to correct x-ray intensity of samples whose element content is vastly different, determination of dead time is necessary. In this paper, a new and complete way to determine dead time is proposed, which can be summarized as “intensity pair method”. Three “intensity pairs” were used for determining dead time, which were “intensity pair” of collimators (S2 and S4), “intensity pair” of spectral lines (Kα and Kβ) and “intensity pair” of beads with different flux-sample ratio (higher SH and lower SL analyte content in the beads). It comes to a conclusion that dead time obtained from “intensity pair” of beads is the most practical method for correcting X-ray fluorescence intensity. As for routine analysis, the dead time of proportional counter can be accurate to 1×10-9s, which can make intensity correction error less than 0.1%.

Dead time determination and its influence to retention index in GC system using polar capillary column

In this research for the determination of dead timeused a method that is mathematically calculated as iteration and linearization of the polar capillarry column in Gas Chromatography (GC) type DN-Wax, by injecting the homologous series of n-alkanes (n-pentane up to n-decane) on GC system. The dead time values obtained are then used to determine the Kovats Retention Index (Retention Index, RI). The results indicated that the retention index had values of systematic error those are more accurate than the retention time (tR), corrected retention time (tR') and retention factor(k'), but the retention index shows the value of random error slightly larger than with other retention parameters. In this study the average values obtained by the iteration method, the dead time was 3.52 minutes with a correlation coefficient of 0.9998. Retention index values obtained are at the confidence level 92.11%-97.06% with the systematic errors 2.04%-7.89%, while the linearization method showed the average value of the dead time 3.3 minutes witha correlation coefficient of 0.9992, but the value of retention index values obtained show that the systematic error is very large. Key words:Dead time, Retention Index, Homologous Series, GC

Consequences of and potential reasons for inadequate dead time measurements in isotope ratio mass spectrometry

Precise and accurate determination of the dead time of a pulse counting system is critical for correct isotope ratio determinations. In this paper, potential problems in the determination of dead time are investigated as well as the consequences of using an erroneous value when correcting for dead time. It is shown how the voltage setting of a SEM can affect the dead time of the system. This can be due to an increased pulse height distribution giving after-pulsing effects, which are not corrected for by a detector dead time model. This hypothesis is supported by pulse height measurements of the output signal of the SEM. Output signals of the amplifier and SEM of an Element2 are also studied and the different nature of these signals (extending vs non-extending) and the consequences of this in the correction of dead time count losses are discussed. It is also found that the dead time values determined via isotope ratio measurements can differ with up to 2.7 ns under optimised instrumental settings, and it is also shown that a relatively small difference (2 ns) in the actual dead time of the system and the value used to correct for dead time results in apparent non-linearity of the system which has been reported by other authors.

New approach to adaptive single pole auto-reclosing of power transmission lines

In this study, a novel digital algorithm is introduced for recognition of arcing (transient) faults and determination of dead time for adaptive auto-reclosing. The algorithm distinguishes between arcing and permanent faults by using the zero sequence voltage measured at the relaying point. If the fault is recognised as an arcing fault, then the third harmonic of the zero sequence voltage is used to evaluate the extinction time of secondary arc and to initiate reclosing signal. The proposed algorithm uses an adaptive threshold level and therefore no significant adjustment is needed for different transmission systems. Moreover, its performance is independent to fault location, line parameters and the system pre-fault operating conditions. The algorithm has been successfully tested for various faults and operating conditions on a 400 kV overhead line using the electro-magnetic transient program (EMTP). The test results have demonstrated validity of the algorithm in determining the secondary arc extinction time and blocking unsuccessful automatic reclosing during permanent faults.

Standardization of 222Rn by LSC and comparison with [formula omitted]- and [formula omitted]-spectrometry

Liquid scintillation counting (LSC) was used for the measurement of 222Rn in equilibrium with its daughters, with detection efficiency close to 5. The appropriate corrections were considered, including one related to the probability that the 165-μs half-life 214Po decays during the dead time of the counter initiated by the disintegration of his parent nuclide, 214Bi. The dead-time determination of a commercial LS counter is also presented using a 222Rn standard source. The LSC 222Rn sources were prepared by transfer of 222Rn produced by a solid 226Ra source into LSC cocktail frozen at 77 K, flame-sealed afterwards. They were measured using the LNHB triple coincidence counter with adjustable extending-type dead-time unit, between 8 and 100 μs; two different procedures were used to calculate an effective dead time and then to deduce the counting rate extrapolated to zero dead-time value. The LSC results were compared with those obtained by cryogenic α -particle spectrometry (LNHB system) and by γ -ray spectrometry for the same radon source in the LSC vial; the geometry transfer coefficient was calculated using the ETNA software. Measurement results and uncertainties are discussed.

Determination of Dead Times in the Recently Introduced Hybrid G-M Counter Dead Time Model

To extend the usable range of the G-M counters the hybrid G-M counter dead time model adopting paralyzable and non-paralyzable dead times (Tp and TNp) at the same time has been introduced and the relationship between true and observed counting rates (n and m) is more accurately expressed in the hybrid model. Other than the decaying source method, which requires a research reactor, the usual way of determining G-M counter dead time is the split source method. To find two dead times of the hybrid model a modified split source method was suggested. The major modification to the original method includes adoption of two split sources and iterative scheme due to transcendental nature of the hybrid model. The modified split source method was tested using Monte Carlo G-M counter simulator, GMSIM, based on ideal hybrid dead time model. Possibility of using interval distribution between observed events and non- Poisson variance characteristics of G-M counters in finding the dead times was also presented.

Method for Dead Time Determination in Reversed-Phase Capillary Electrochromatography with Methacrylate-Based Stationary Phases

A method for dead time determination in reversed-phase capillary electrochromatography (RP-CEC) with methacrylate-based monolithic stationary phases has been presented based on homologue series method. The dead times measured with homologue series method and thiourea, a commonly used electroosmotic flow (EOF) marker are compared under various conditions, such as the type and the concentration of organic modifier, ionic strength, and applied voltage. Results show that the former one is larger than the latter one. Under high ionic strength and low applied voltage, EOF velocity measured by thiourea is close to that determined by homologue series method.

Abnormal phenomenon of the dependence of the retention factors for uncharged species on applied voltage in capillary electrochromatography

Polymethacrylate-based monolithic columns were prepared for capillary electrochromatography (CEC) byin situ copolymerization of butyl methacrylate (BMA), 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), and ethylene dimethacrylate (EDMA) in the presence of a porogen in fused-silica capillaries of 100 μm I.D. The abnormal phenomenon that retention factors for neutral species decreases with applied voltage in CEC was observed. Capillary electrophoresis (CE) instruments usually require a period of time to increase voltage from 0 kV to desired value, which is called as ramp time. Such ramp time and any error in the determination of dead time should be taken into account during the accurate calculation of retention factors. After the correction of the retention factors, the plots of the corrected factors for alkylbenzene versus applied voltage were made, the absolute value of the plot slopes are less than 1.8×10−4, which indicates that the corrected retention times for neutral species do not show any dependence on applied voltage. Further, the plats of the corrected retention times for acidic and basic compounds versus the reciprocal of applied voltage were drawn, where the target compounds were eluted in neutral form. The very nice linearity of the plots was obtained. The linear correlation coefficients are over 0.999. Here, the slopes of the plots represent\(\frac{{L_{eff} \cdot L_{tot} \cdot \left( {l + k} \right)}}{{\mu eo}}\), which indicates that retention factors for the test compounds are constants under a given separation condition.

A calculation method based on isotope ratios for the determination of dead time and its uncertainty in ICP-MS and application of the method to investigating some features of a continuous dynode multiplier

A method for the determination of dead time (and its uncertainty) of the ion-counting detection system of ICP-MS instruments is presented. It is based on isotope ratio measurements, which are more precise than ion current measurements and will result in values for the dead time with a measurable uncertainty. The suggested method allows us to estimate the uncertainty associated with the dead time. Typical relative uncertainties of the dead time values were found to be in the range of 10-20%.

Measurements of dead time and characterization of ion counting systems for mass spectrometry

A method for characterization of electron multiplier-based pulse counting systems is presented. Specific attention is paid to measurement of the counting system dead time. The systems discussed here are typically used to measure the abundance of ions passing through a mass spectrometer. A method for the determination of dead time by measurement of at least two isotopic ratios of an element with at least three isotopes is given. This method differs from the “text book” method typically used to measure the dead time. The theoretical basis for the measurements is given and an example of measurements of Ti isotopes by secondary ion mass spectrometry (SIMS) is shown. Dead time measurements on SIMS instruments can be performed in a few hours of machine time. A brief description of the pulse detection and counting circuit and its operation is also given. Guidelines for the proper measurement of pulse shapes and the determination of reasonable settings for electron multiplier gain, preamplifier gain, and discriminator threshold are also discussed.

Global treatment of chromatographic data with MICHROM

The program MICHROM for the general treatment of chromatographic data is presented. MICHROM takes part in all the stages of the analytical process. It allows determination of dead time, smoothing of chromatograms, measurement of peak parameters, fitting of skewed peaks, and deconvolution of overlapped peaks. Tools for the experimental design, optimization of the mobile phase composition to resolve a mixture of analytes, and simulation of chromatograms in several experimental conditions, are implemented. Routines for the graphical representation of chromatograms, resolution surfaces, contour maps, management of data series, optimization and regression analysis, are also included. The resolution of chromatographic problems of diverse nature and complexity is possible.

Determination of dead-time in photon counting photometers by a polarimetric method

Experiments are described which demonstrate that the dead-time constant associated with a photon counting stellar photometer/polarimeter is readily determinable by the application of the Malus law. It is also proposed that corrections for dead-time losses should be applied by an iteration technique to the exact equation rather than using the available approximation formulae.

Dead time of dual detector tools : J. A. Czubek, Nuclear Geophysics, 8(4), 1994, pp 317–326

A theory of the dead time for the dual detector nuclear tool with the analogue signal transmission is given in the paper. At least two different times exist in such tools: the dead time of detectors (for final computation they are assumed identical to each other) and the dead time of the signal transmission set-up. A method of two radioactive sources is proposed to measure these two different dead times. When the times used for measuring every countrate needed in the dead time determination algorithm are taken into account, the statistical accuracy of the dead time determinations can be obtained. These estimations are performed by the computer simulation method. Two codes have been designed: DEADT2D (DEAD Time for 2 Detectors) and DEADT2DS (DEAD Time for 2 Detectors with Statistics)

A Comparison of Methods for the Determination of Dead Time in a Reversed-Phase High-Performance Liquid Chromatography System Used for the Measurement of Lipophilicity

Abstract The dead time (void volume) of a reversed-phase system utilizing a column containing the divinylbenzene-styrene copolymer packing (PRP-1) was determined using candidate dead time markers, and two series of homologues, n-alkanols and n-alkyl benzenes. The retention data from the homologous series were subjected to several mathematical treatments. The retention data for n-alkanols gave consistent values for the dead time (1.24–1.27 minutes) provided that data from MeOH and EtOH were not included. Data from the n-alkyl benzene series did not provide a reliable value for system dead time. Of the candidate void volume markers examined, sodium nitrate and water (1.26 minutes) had retention times which were consistent with dead times calculated from the n-alkanol series. As nitrate is readily detected by both UV and RI at low concentrations, it is the preferred dead time marker for this HPLC system. The homologous series of compounds were used to calibrate the system for the determination of lipophilici...

Column dead-time determination methods based on the isothermal retention-time behaviour of a homologous series in chromatography

In this paper, the theory of chromatographic retention behaviour of the members of a homologous series is tested, which is based on the hypothesis that the ratio of the adjusted retention times of any two consecutive members of any homologous series in an isothermal column is constant. The paper shows how the dead time of a column can be calculated from the slope and intercept of a linear graph of the gross retention times of the n+ 1th homologue members versus the gross retention times of the nth homologue members, and a method is outlined whereby equal weighting can be given to all the experimental retention times of the homologue members used in the said plot.