Scintillation Method Research Articles

Resolving Pulsar Magnetospheres Using Interstellar Scintillation

Pulsars are very small objects and to resolve a pulsar magnetosphere you would need an interferometer with a baseline of 14 AU at a frequency 100 MHz. If the angular size of the diffraction pattern at the Earth is less than the angular size of pulsar:θc<θLCthen emission regions separated by alight-cylinder radius will produce scintillations that are independent. The interstellar scintillation method presents a unique oppotunity for measuring the angular size of sources with a resolution up to 10−8arcsec at meter wavelengths.There were different attempts to resolve pulsar magnetospheres by the scintillation method (Cordes, Weisberg and Boriakoff, 1983, Wolszcan and Cordes, 1987; Smirnova and Shishov, 1989; Smirnova, 1992). Here we present new observations of 4 pulsars: PSR 0834+06, 1133+16, 1237+25 and 1919+21 at a frequency 102 MHz from which we can see evident decorrelation of the pulsar spectrum with increasing space separation between sources in the pulsar magnetosphere.

IPS Observations at STELAB for the Fruitful Coming Decade

AbstractWe have been carrying out solar wind measurements using the interplanetary scintillation (IPS) method. Our IPS observation system is operated at a frequency of 327MHz and consists of four stations located at Toyokawa, Fuji, Sugadaira and Kiso. The present system, however, has insufficient sensitivity to measure enough IPS sources for observing the solar wind with adequate spatial and temporal resolution. Therefore we have been excuting the upgrade project since 1994 in order to observe a larger number of compact radio sources. The Fuji system has been improved successfully and has achieved sensitivity by a factor over five compared with the previous system. The upgrade project is now in progress for the Toyokawa and Sugadaira station.

IPS observations at stelab for the fruitful coming decade

We have been carrying out solar wind measurements using the interplanetary scintillation (IPS) method. Our IPS observation system is operated at a frequency of 327MHz and consists of four stations located at Toyokawa, Fuji, Sugadaira and Kiso. The present system, however, has insufficient sensitivity to measure enough IPS sources for observing the solar wind with adequate spatial and temporal resolution. Therefore we have been excuting the upgrade project since 1994 in order to observe a larger number of compact radio sources. The Fuji system has been improved successfully and has achieved sensitivity by a factor over five compared with the previous system. The upgrade project is now in progress for the Toyokawa and Sugadaira station.

Magnetic fields and radio jets in giant radio galaxies

The study of giant radio galaxies by the scintillation method [1-4] at 102 MHz enables us to estimate the strength of the magnetic field and also the density of relativistic electrons in compact radio sources. Using the formula 0 = 4.3'1016S1/2~-5/4H±1/4(1 + z) I/4 [5] the strength of the magnetic field H± is estimated, where 0 is the angular size of the source, S is the maximum flux density at frequency z,, and z is the redshift. One readily may determine the energies of the magnetic field and relativistic electrons by estimated values of H± and the density of electrons. Comparison of these energies (see Table 1) shows that in the radio galaxy DA240 the strength of the magnetic field is 6 orders of magnitude greater than the energy of relativistic electrons [1]. In DA240 the relativistic electrons can be easily captured by the magnetic field and consequently emit isotropic radiation. In this case the radio jet cannot be formed. In NGC1275 the energy of the magnetic field is 8 orders of magnitude less than the energy of electrons [2], and the relativistic electrons can easily pass through the galaxy into the intergalactic medium. Hence the radiation in the radio range is absent far from the core. In this case a radio jet will not be observed. In NGC315 and 3C31 the energy of the magnetic field is comparable with the energy of electrons [3, 4], and the electrons are gathered in the galaxy and around it. But the magnetic field prevents electrons from passing through the galaxy, which are captured by magnetic field radiating in radio range. If the magnetic field has a fixed direction or electrons are being ejected by the galaxy core in a fixed direction, then radio jets can be formed. The interaction of electrons with the vicinity can form compact radio sources at the edge of the radio jet. Thus, we can conclude that in radio galaxies where the energies of the magnetic field and relativistic electrons are comparable, radio jets can be formed, otherwise they do not form.

The scintillation method tested over a dry vineyard area

Measurements of a scintillometer device mounted at 4 m above a dry vineyard area in La Mancha, Spain, are used to obtain an average sensible heat flux densityH. Averaging is over a rectangular area determined by the distance between the scintillometer light source and receptor (875 m) and some upwind distance governed by the horizontal wind speed perpendicular to that line. Using similarity relations obtained from La Crau, a good correspondence betweenH measured with the scintillometer and an eddy-correlation device in the centre of a vineyard is obtained. The friction velocityu * was either measured directly using a sonic anemometer or obtained indirectly from two wind speeds and known values of the roughness length zo and displacementd. The free convection formulation underestimates the sensible heat flux by about 30%. This is due to a significant contribution of mechanically generated turbulence to the total turbulent transport, which was caused by relatively strong winds and rough terrain.

222Rn in Water

The U.S. Environmental Protection Agency has proposed a drinking water standard for 222Rn in public water supplies. When promulgated, operators of public water supplies will be required to determine water 222Rn concentrations. Most likely, water samples will be collected and mailed to laboratories for analyses. Additionally, it is probable that homeowners will test private well water in a similar manner by collecting water samples and mailing them to a laboratory for 222Rn analyses. In anticipation of these actions, this study was conducted to evaluate two methods of water sample collection and to evaluate the potential losses of 222Rn from water samples mailed to a laboratory. Thirdly, temporal variations in 222Rn concentrations in several groundwater supplies in North Carolina were examined. Water supplies at four sites in eastern North Carolina and five sites in western North Carolina were sampled over a 7-mo period beginning in the fall of 1993 and continuing through the spring of 1994. Samples were analyzed using a liquid scintillation method. This study showed that a "slow-flow" method is not only suitable for sample collection, but may be the preferable method for water sample collection since slow-flow collection resulted in less 222Rn loss than was observed during syringe collection, i.e., the water 222Rn concentrations in samples collected by the slow-flow method were generally higher. Further, based on this study, mailing water samples to a laboratory for analysis should not have a substantial effect on the measured 222Rn concentrations. Consequently, water samples can be collected by the slow-flow method by water supply operators, as well as homeowners, and mailed to laboratories for 222Rn analyses with reasonable assurance that the samples have not suffered significant 222Rn loss. Temporal variations in water 222Rn concentrations were observed in this study. One factor complicating the study of temporal variations in 222Rn concentrations was the striking influence that inconstant water usage and inadequate well purging prior to sample collection had on 222Rn loss from the water.

A new calibrated chamber for parametric studies of radon and thoron gases

A new environmental radon chamber has been designed, constructed, and tested by our group. The design was evolved in order to meet the needs of several different radon detection techniques, both active and passive. The radon activity concentration of the barrel was determined by cross calibration against the standard radon chamber at the UK National Radiological Protection Board with known activity concentration, using the Lucas cell scintillation method. The radon activity concentration inside the barrel was found to be about 90 kBqm −3.

Tritium Production-Rate Measurement Techniques Developed at FNS/JAERI

The tritium production-rate (TPR) is a very important neutronic parameter in the D-T fusion blanket research. The following five techniques for the measurement of TPR have been developed at FNS/JAERI: (1) Subtraction method using a pair of Li-glass scintillators, (2) Indirect method using a small sphere NE213 scintillator, (3) Liquid scintillation method with Li{sub 2}O pellet, (4) Liquid scintillation method with Li{sub 2}O plate/block (zonal method), and (5) LiF TLD self-irradiation method. This paper describes these methods, comparison of their features, and their typical results for the blanket benchmark experiments at FNS.

Solar wind speed and its acceleration inferred using the interplanetary scintillation method in carrington rotation 1753

Solar wind speeds (SWSs) estimated by interplanetary scintillation (IPS) observations during Carrington rotation 1753 are projected onto the so-called ‘source-surface’ of 2.5 solar radii along magnetic field lines in interplanetary space. The following two working hypotheses are examined from different points of view: (1) The SWS is a weighted mean along the line of sight to a radio source; the weight for the SWS depends on the distance from theP-point, the closest approach to the Sun on the line of sight. (2) The weighting function has a very sharp peak at theP-point, so that the SWS shows a real solar wind speed at theP-point. In both the two cases, the SWSs projected onto the source surface are further projected onto the photosphere along magnetic field lines in the corona. Footpoints of these field lines are inferred as photospheric source regions of the solar wind. The intensity of the Hei (1083 nm) absorption line (HEI) in the chromosphere corresponding to these photospheric sources is interpolated from observational data. The weighted mean of the HEI is calculated in case 1. The HEI corresponding to theP-point is used in case 2. The SWS is compared with the HEI in both the two cases. It is found that the correlation between the SWS and the HEI is better in case 2 than in case 1. It is further inferred by correlation analysis between the SWS and the HEI that the solar wind is accelerated within ∼27 solar radii on average. Although the data examined in this paper were limited to just one solar rotation, these results suggest that the SWS estimated by the IPS technique corresponds to the solar wind speed near theP-point and the weighting function along the line of sight may have a very sharp peak near theP-point.

Alpha-beta discrimination liquid scintillation counting for uranium and its daughters

Advances in liquid scintillation counting (LSC) technologies, such as imporved scintillation cocktail formulations and alpha-beta radiation discrimination, make LSC suitable for applications in uranium process chemistry. Ease of use, low cost, and the huge dynamic range of LSC are distinct advantages for analytical support of actinide processing. All uranium isotopes decay primarily with alpha radiation emission. The immediate short-lived daughters of238U are234Th and234Pa. These nuclides are beta emitters having energy bands that overlap the uranium bands in a liquid scintillation spectrum. The resolution of these overlapping bands by alpha-beta radiation discrimination is useful for uranium quantification and purity verification. Protactinium-234 is a high-energy beta emitter that can be further identified and quantified from it's Cherenkov radiation. Energy spectra were collected on the Packard 2500AB liquid scintillator analyzer for uranyl solutions in diisopropylnaphthalene and pseudocumene based scintillator cocktails. Calibration curves were prepared for nitric, hydrochloric, and sulfuric acid media. Base titrations demonstrated the effect of acid quenching on those system. Ion exchange and water soluble polymer extraction studies are readily followed using liquid scintillation methods.

Tritium volume activity in the baltic sea in 1987–1989

Tritium volume activities measured in the Baltic Sea are summarized in this paper. Activity levels were determined by the liquid scintillation method with a LS-1000 counter. The field investigations showed that the tritium volume activity in the Baltic Sea can change substantially in absolute magnitude. Therefore, average volume activity is used as an indicator of natural content. Correlations between calculated (averaged) tritium activity levels and the Chernobyl accident are very briefly discussed. 7 refs., 2 figs., 1 tab.

Standardization of iodine-129 by the TDCR liquid scintillation method and 4π β-γ coincidence counting

Iodine-129 is a long-lived fission product, with physical and chemical properties that make it a good candidate for evaluating the environmental impact of the nuclear energy fuel cycle. To avoid solid source preparation problems, liquid scintillation has been used to standardize this nuclide for a EUROMET intercomparison. Two methods were used to measure the iodine-129 activity: triple-to-double-coincidence ratio liquid scintillation counting and 4π β-γ coincidence counting; the results are in good agreement.

Determination of uranium by liquid scintillation and Cerenkov counting

Three radiometric methods for the determination of uranium in aqueous samples, involving the use of a liquid scintillation counter, have been studied and compared. Uranium is separated and purified by coprecipitation with iron(III) hydroxide followed by an anion-exchange process. The purified uranium in the eluate (0.1 mol l–1 HCl) can either be collected and stored and the Cerenkov radiation from the in-growth of the high-energy β-emitter 234Pa counted, or the uranium can be extracted from the chloride eluate into diethylhexylphosphoric acid in toluene containing appropriate scintillation materials and counted by a liquid scintillation technique. Alternatively, uranyl chloride can be converted into uranyl nitrate, which is then dissolved in 1 ml of 1,4-dioxan, and the solution is subsequently mixed with scintillation solution and counted. In the liquid scintillation methods, both 234U and 238U can be determined, but, by using the Cerenkov method, 238U is measurable in isolation. Several variants of the chemical-separation procedure have been studied in relation to their effect on quenching, sensitivity and accuracy. The background count rates observed were 0.04, 0.075 and 0.213 counts s–1 for the 1,4-dioxan, extraction and Cerenkov techniques, respectively; the lower limit of detection was taken as 3σ of the background. Chemical yields were in the range 80–90%.

Monitoring of 35S in ash of incinerated waste.

The National Institute of Environmental Health Sciences incinerates low-level radioactive waste containing 3H, 14C, and 35S as a means of volume reduction. The primary isotope remaining in the ash is 35S. Some effects of the chemical and physical form of the waste on sulfur retention in ash and several methods for determining the activity remaining in the ash have been explored. It was found that the sulfur in sodium sulfate has a higher retention in ash than the sulfur in methionine and that the presence of glass appears to enhance the retention. Liquid scintillation and proportional counting methods were compared. A sulfur extraction procedure using liquid scintillation counting was found to give the lowest minimum detectable activity. However, it was determined that a more practical method for routine monitoring is to suspend a small quantity of ash in a liquid scintillation gel.

Electret Ion Chamber Radon Monitors Measure Dissolved 222Rn in Water

This paper describes a simple and relatively inexpensive method of determining the concentration of dissolved 222Rn in water. The method involves a recently developed electret-passive environmental radon monitor, which uses an electret ion chamber. The procedure consists of sealing a known volume of a carefully collected water sample with one of these monitors in an exposure container and determining the average equilibrium 222Rn gas concentration in the air phase during the exposure time period. This average concentration can then be used to calculate the 222Rn concentration in the original water sample. Identical samples were analyzed both by this new method and by a standard liquid scintillation method, and the results were compared over a wide range of 222Rn concentrations. There was good agreement except that the electret ion chamber method gave results that were consistently lower by about 15%. This bias in the results was attributed to both 222Rn losses during sample handling and possibly to some errors in the assumptions made in the theoretical model. A correction factor is recommended to bring the results of this technique into agreement with the standard method. The procedures are simple and economical and can be easily employed by many primary 222Rn-measuring laboratories currently using these monitors for measuring indoor 222Rn.

Temperature dependence of protein solubility — determination and application to crystallization in X-ray capillaries

A scintillation method was developed for determinations of the temperature dependence of the solubility, and of nucleation induction times of proteins, in 50–100 μl volumes of solution. Solubility data for lysozyme and horse serum albumin were obtained for various combinations of pH and precipitant concentrations. These data and the nucleation induction information were used for dynamic crystallization control, that is, for the controlled separation of nucleation and growth stages. Individual lysozyme and horse serum albumin crystals were grown in 15–20 μl solution volumes contained in X-ray capillaries.

Problems and Methods of Dating Low-Activity Samples by Liquid Scintillation Counting

The important problem of contamination of old samples by younger 14C necessitates treatment of organic and carbonate samples to ensure more complete removal of contaminating carbon. Here we present studies of chemical procedures for the liquid scintillation method of 14C dating undertaken since 1960 in the former USSR. We discuss new procedures such as lithium carbide synthesis from charred organic samples and benzene synthesis on a V2O5·Al2O3·SiO2 catalyst, as well as memory effect in the carbide synthesis procedure and characteristics of two homemade counters.

Metabolism and Distribution of 1-[14C]Alprazolam in Rats

Using 14C-labeled alprazolam (1-[14C]APZ) as a model for 1-[11C]APZ, we evaluated the tissue distribution of total radioactivity and assessed the contribution of the polar metabolites of APZ (α-hydroxmethyl-and 4-hydroxy-APZ) to radioactivity levels in the plasma and brains of rats over the course of 1h. The biodistribution data showed that the uptake of radioactivity by rat brain was 0.31% of the injected dose per gram of tissue weight at 10min postinjection. Pretreating rats reduced the levels in brain to 0.21% of the injected dose at 10min but had little effect on the distribution of radioactivity in plasma and other tissues studied. Analysis of the metabolites in plasma and brain homogenates by an extraction-thin-layer chromatography-liquid scintillation method revealed that >94% of the radioactivity in the rat brain was due to 1-[14C]APZ over the course of 1h. APZ, therefore, is stable to metabolic transformations in the rat brain, and the polar metabolites are readily conjugated and excreted so that their cerebral uptake is minimal.

222Rn (226Ra) determination in water by scintillation methods

A comparison between the counting parameters of solid and liquid scintillation methods for radon determination in water is attempted. The counting efficiency is better for a toluene-based liquid scintillator but, as the background is considerably higher than in solid scintillators, the figure of merit and the lower limit of the measurable activity are favorable for a scintillation counter based on zinc sulfide (Ag activated) scintillator.

Review of optical scintillation methods of measuring the refractive-index spectrum, inner scale and surface fluxes

Abstract The background, recent progress and future trends of remote sensing of three environmental parameters using optical scintillation are reviewed. The parameters are the refractive-index spectrum of turbulence, the inner scale of turbulence, and the surface fluxes of heat, humidity and momentum.