Alpha Particles In Water Research Articles

Development and evaluation of a standard for absorbed dose to water from alpha-particle-emitting radionuclides

Targeted radionuclide therapy and brachytherapy with alpha particles has gained significant clinical relevance recently. Absorbed dose traceability to a standard is currently lacking in the dosimetry chain. The short range of alpha particles in water of <100 μm complicates the absorbed dose measurements in the form of significant attenuation and perturbation effects. The aim of this work was to develop and validate a standard for absorbed dose to water from alpha-particle-emitting radionuclides. A dosimetric formalism to realize surface absorbed dose to water per unit activity using a windowless cylindrical parallel-plate ion chamber (IC) was introduced. IC-based and Monte Carlo (MC)-based correction factors were calculated for a planar circular 210Po alpha-particle emitter. The measured absorbed dose to air was compared to the MC-calculated absorbed dose. A parallel-plate IC with a nominal 4 mm collector diameter composed of polystyrene-equivalent material was utilized as a standard. MC simulations were performed using the TOPAS MC code and finite source size, backscatter, and emission angle divergence correction factors were calculated by modeling the IC and the source. Multiple measurement trials were performed to measure ionization current at air gaps in the 0.3 mm to 0.525 mm range. The proposed dosimetric formalism was employed to calculate the surface absorbed dose to water from a point-like 210Po source. The recombination and polarity correction factors were measured to be <0.50% when a 150 V mm−1 electric field strength was applied. The MC-calculated and measured absorbed dose to air agreed within 2.05%. The finite source size and backscatter corrections were <10% with the emission angle divergence correction being in the 93%–239% range. The surface absorbed dose to water was measured to be 2.8913 × 10−6 Gy s−1 Bq−1 with a combined uncertainty of 4.23% at k = 1. This work demonstrated the ability of a windowless parallel-plate IC as a standard for absorbed dose from alpha-particle-emitting radionuclides.

Theoretical evaluation of calibration factor for CR-39 track detector for alpha radioactivity measurement in natural water

A simple track-etch method by using CR-39 detectors has been developed for determining the total alpha radioactivity level in natural water. The detectors are immersed into water sample for alpha exposure. Alpha particles generated near the detectors create latent tracks, which are a measure for the alpha radioactivity of the sample. Calibration factor (CF) evaluation for a track detector is a part of this method. It is evaluated by considering major alpha-emitters present in natural water and taking into account the actual geometry of the set-up. The method for evaluating the CF is based upon the calculating range of alpha particles in water and the estimating effective volume of water around the detector. The evaluated CF is found to be(116.18±9.88)Bq.l−1.(tracks.cm−2.h−1)−1. This method has been used to determine the total alpha radioactivity of 52 drinking water samples collected from different tube-well and tap water points at eight districts of Indian state of West Bengal. Measured radioactivity values vary from (15.17±1.29)Bq.l−1 to (45.67±3.88)Bq.l−1 with a mean value of (27.64±2.35)Bq.l−1. These radioactivity values are compared well with the worldwide alpha activity values reported in research articles. It is observed that the measured alpha radioactivities are below the recommended reference level and hence, the drinking waters of the sampling sites are safe for consumers. The CF evaluated and the experimental method developed in the present study can also be utilized in the radioactivity research field. Data obtained in the present study may serve as a good baseline.

Feasibility evaluation of a direct detection method of alpha particles in water using YGAG plate with pulse shape analysis

Ce doped (YGd)3(GaAl)5O12:Ce (YGAG) is a ceramic scintillator with high light output, and its decay times are different between alpha particles and gamma photons or beta particles. This characteristic may be applied to the direct measurement of alpha particles in water where the gamma photons or beta particles become background counts. Thus we proposed a radiation detector using a YGAG plate dipped in water that contained alpha radionuclides to detect alpha particles in water. The scintillation photons from the YGAG plate were detected by a position sensitive photomultiplier tube (PSPMT) set in water that contained alpha radionuclides. A YGAG plate (20 × 20 × 0.5 mm) was set on the bottom of a glass cup filled with water containing alpha radionuclides that emit alpha particles. The alpha particles near the YGAG plate were detected by the scintillator, and the scintillation light was detected by the PSPMT . For radon-containing water sampled from a hot spring, pulse shape spectra showed two peaks: one for the alpha particles and another for the beta particles and the gamma photons. By pulse shape discrimination for the peak of the alpha particles, their count rate decreased with a decay of Rn-222 (3.8 days). For tap water, the pulse shape distribution showed only one peak and the count rate was almost constant, indicating these counts were mainly from the background beta particles or gamma photons. We could show a detection principle for alpha radionuclides in water and this detection principle for alpha radionuclides in water might be a new method for estimating the alpha radionuclide concentration in water.

Calculation of the Relative Stopping Power of Protons and Alpha Particles In Water

n this research we studied and calculatedtherelative stopping power(RSP) of protons and alpha particles in water with energy (35-150)MeV by calculating the range of these particles in water and air, where the range of protons in water calculated by usePSTARprogram and ASTARprogram to calculate the range of alpha particles in water for the same range of energy .The range of protons in air calculate by semi empirical equation while by using Bragg and Kleeman ruleincalculation the range of alpha particle in air.

Ionization cluster size distribution for alpha particles: experiment, modelling

The paper presents data for measured ionization cluster size distributions by alpha particles in tissue equivalent media and comparison with the simulated data for liquid water. The experiments were carried out with a beam of 4.6 MeV alpha particles performed in a setup called the JET Counter. The theoretically derived cluster size distributions for alphas particles were obtained using the K-means algorithm. The simulation was carried out by Monte Carlo track structure calculations using cross sections for liquid water. The first moments of cluster size distributions, derived from K-means algorithm as a function of diameter of cluster centroid, were compared with the corresponding moments derived from the experiments for nitrogen and propane targets. It was found that the ratio of the first moments for water to gas targets correlates well with the corresponding ratio of the mean free paths for primary ionization by alpha particles in the two media. It is shown that the cluster size distributions for alpha particles in water, obtained from K-means algorithm, are in agreement with the corresponding distributions measured experimentally in nitrogen or propane gas targets of nanometer sizes.

Monte Carlo Track Structure Code for Low-Energy Alpha-Particles in Water

The paper describes the development of a new generation of Monte Carlo track structure code, which simulates full slowing down of low-energy alpha-particles history tracks (leahist) in the range 1 keV-8 MeV in water. All primary interactions including elastic scattering, ionization, excitation, and charge exchange by He 2 + , He + , and He 0 were taken into account. Cross sections for bare and dressed helium ions and neutral helium impact were obtained from experimental data for water vapor targets. Where data were lacking the existing experimental data were fitted and extrapolated. The tracks of secondary electrons were generated using the electron track code kurbuc. The code can be operated to generate tracks both in the track segment and the full-slowing-down modes. Tracks were analyzed to provide confirmation on the reliability of the code and information on physical quantities, such as range, W-values, restricted stopping power and radial dose profiles. This new development enables us to work on aspects of the radiation of environmental interests such as radon. No attempt was made to simulate the track of alpha-particles below 1keV as in this region cross sections for interactions involving electron loss and capture are severely lacking and in general the chemistry which follows the interaction of these slow ions is not well-known.

Influence of the physical state and straggling on the computation of the radiation dose due to radon daughters deposited in the lung

The effect of the physical state (phase) of the absorbing medium and the energy straggling of the alpha particles on the calculation of the radiation dose due to the daughter products of radon deposited in the lung, have been studied in detail. The stopping power data for alpha particles in water and water vapour have been used. It has been found that the effect of straggling on the stopping power calculations is small, and therefore its contribution to dose calculations is negligible. The phase effect has been found to be dependent on the energy of the alpha particles and the depth in the medium. If the stopping power of water vapour is used instead of that for liquid water, the dose may be overestimated by 5-20 and 1-11% for 6 and 7.7 MeV alpha particles, respectively, at the beginning of alpha range, and underestimated by 15 and 40% respectively for the above energies at the end of the range.

Preliminary report of an improved technique for determining mean range of alpha particles in water

A new technique is discussed for determining the mean range of alpha particles in water.

SOME DOSIMETRY PROBLEMS OF THE ALTERNATING GRADIENT SYNCHROTRON (AGS).

After a discussion of methods of high-energy dosimetry, data on linear energy transfer and quality factors of pions, protons, deuterons and alpha particles in water are summarized. These are shown to approximate the values for tissue and are given both for specific particle energies and as averages for complete tracks. The dosimetry of micro-meson fluxes is considered from a theoretical point of view. The response of personnel monitoring equipment to such fluxes is shown to be “fail-safe” for average particle quality factors of 2.9 or less. External proton beams are shown to be extremely hazardous and some data are given on the response of film badges to beams of protons and pions. Typical depth-dose curves are given. They show substantial build-up only in relatively uncontaminated beams of highenergy particles. Activation of machine parts and targets is described briefly.

The Experimental Determination of the Range-Energy Relations for Alpha Particles in Water and Water Vapour, and the Stopping Power of Water and Water Vapour for Alpha Particles at Energies below 8.78 MeV

A method for measuring the residual energy of alpha particles which have traversed paths of various lengths in water is described, and also a method for determining total alpha-particle range in water, the results being used to deduce a range-energy relation for alpha particles of energy up to 8.78 MeV in liquid water. A method is described for measuring the residual energy of alpha particles which have passed through air and through water vapour, and by means of a scintillation detector the complete alpha-particle range in air and in water vapour is established. From these results range-energy relations are deduced for alpha particles in air and in water vapour. The differential and integral stopping power of water and water vapour at various energies is calculated and the results are discussed.

The Range of Alpha-Particles in Water

A photographic method is described for measuring the ranges of alpha-particles in liquids whose properties are compatible with emulsion sensitivity utilizing a surface deposit of radiocolloid aggregates as point sources of alpha-radiation. The method has been applied to both water of normal isotopic composition and to heavy water containing 97 percent deuterium oxide. Using polonium radiocolloids as a source of 5.3-Mev alpha-particles ranges of 38.1\ifmmode\pm\else\textpm\fi{}0.5 and 38.0\ifmmode\pm\else\textpm\fi{}0.5 microns were measured in the respective liquids. By conducting the exposure at temperatures below the freezing point the method is also applicable to certain solid media. The ranges of RaF alpha-particles in normal and heavy ice were found to be 41.6\ifmmode\pm\else\textpm\fi{}0.5 and 41.5\ifmmode\pm\else\textpm\fi{}0.5 microns. The integral molecular stopping power of water is computed to be 1.56\ifmmode\pm\else\textpm\fi{}0.02 for an alpha-particle energy of 5.3 Mev. Similar measurements with radium sulfate radiocolloids indicates a molecular stopping power of 1.56\ifmmode\pm\else\textpm\fi{}0.02 for the alpha-particles from RaC\ensuremath{'}, as compared with a computed value of 1.54\ifmmode\pm\else\textpm\fi{}0.02. Larger estimates for this constant may originate from water-air interface effects inherent in experiments with an external detector.