Range Of Alpha Particles Research Articles

Determination of the range of alpha particles in histological samples using a proton beam

Abstract The 70 μm -thick sliced mouse samples used in boron neutron capture therapy research are normally freeze-dried and permanently mounted on a sticky tape. Such a preparation alters the tissue density and makes it impossible to correctly determine the ranges of the alpha particles from the 10B(n,α)7Li reaction. Proton radiography utilising etched-track detectors can be successfully used for the density determination of these histological samples. The technique is based on the measurement of different energy losses in different tissues. A computer simulation was made in order to estimate the efficiency and sensitivity of this technique. Some typical values for tissue density and elemental composition were taken from the SRIM program database. The applicability of this technique was illustrated and ranges of alpha particles in a histological sample of tumor-bearing mouse were determined using proton ranges as a reference.

Therapeutic radiopharmaceuticals.

A variety of radiopharmaceuticals have been introduced for the internal therapy of malignant and inflammatory lesions in nuclear medicine. In order to destroy the diseased tissues radionuclides with high linear energy transfer (LET) such as beta, alpha, Auger or low energy conversion electron emitters are needed. The range of beta particles is in mm's so they are effective for large tumors. The range of alpha particles is short, only a few cell diameters. Thus, they are effective in treating circulating malignant cells and micrometastases. The range of Auger and conversion electrons is <0.1 micro m. They are very effective in cell killing when they are carried across cell membrane into the nucleus to damage DNA. Appropriate ions, molecules and particles are labelled with such radionuclides and used as radiopharmaceuticals in many different applications. For an effective dose to be delivered high target to non target ratios must be attained. Monoclonal antibodies to specific antigens expressed on tumor cells have been developed to increase the uptake by malignant tissues by specific accumulation. Radiolabelled peptides such as somatostatin, small molecules such as metaiodo-benzylguanidine (MIBG) and many different nano-and micro-particles have been investigated. The effectiveness of therapy can be increased by direct locoregional administration of the radiopharmaceutical. This way the radiation effects are confined locally and the normal tissues are spared from radiation effects. In this review article selection criteria and characteristics of radionuclides and carrier ions, molecules and particles for various therapeutic applications will be discussed, including mainly the recent developments.

Fetal Dosimetry from Natural Alpha-Particle Emitters

The alpha-particle dose to human fetal bone marrow from natural exposure was investigated. The rate of calcification and the (210)Pb activity levels in fetal vertebrae showed that (210)Pb follows the uptake of calcium into the skeleton. Lead-210-supported (210)Po activity concentrations of up to 0.18 Bq kg(-1) were found in fetal lumbar vertebra. The mean chord length of the trabecular spaces in lumbar vertebra were 110-320 micrometer at 20- 40 weeks, in rib 130-180 micrometer at 20-35 weeks, and in sternum 190 micrometer at 35 weeks of gestation. In lumbar vertebra, up to 80% of marrow was within alpha-particle range (37 micrometer) of a bone surface. This resulted in a gestational equivalent dose to marrow from (210)Pb-supported (210)Po in bone of 8 and 24 micrometerSv when the contribution from all major natural alpha-particle-emitting radionuclides was considered. The mean distance of CD34(+) cells from the nearest bone surfaces in lumbar vertebra was 61 and 46 micrometer at mid- and late gestation, respectively. The mean cellular and nuclear diameters of CD34(+) cells were 5.5 and 3.8 micrometer respectively, and remained constant with gestational age. Few stem cells were hit by alpha particles at natural exposure; however, those that were hit received doses of up to 1.3 Gy.

Determination of the range of alpha particles in SSNTD by optical density method

A technique based on the optical density ( D ) measurement of the etched track is useful for charged particles spectroscopy using SSNTD. It was shown that the stopping power of alpha particles in CR-39 is proportional to D . We measured the optical density and derived an expression to estimate the range of alpha particles in CR-39 detector as a function of the bulk etching rate and etching time. The relation between the etching time, track parameters (depth, radius) and D for different alpha particles energy and etching conditions were studied. A relation describing D as a function of track size is proposed.

Investigation of the range of alpha particles

Measuring the range of alpha particles is not as straightforward as it might seem: two techniques give a clearer picture than just one.

Energy distributions and yields of long range alpha particles emitted during spontaneous fission of 238,240,242,244Pu isotopes

The energy distribution and yield of Long Range Alpha (LRA) particles emitted during spontaneous fission of 238,240,242,244Pu-isotopes have been measured. Correlations between these experimental results with the total average excitation energy 〈TXE〉 the α-cluster preformation probability Sα and the fission modes have been shown. This permitted us to demonstrate that the LRA emission probability is strongly influenced by Sα and also that it is very much enhanced for the (more deformed) Standard II fission mode compared to the (more spherical) Standard I mode.

Whole body personnel monitoring via ionization detection

A project between Fernald EMP and LANL is to field a monitor for the detection of alpha-emitting contamination on a human body. Traditional personnel monitoring for alpha emitters involves either frisking with a probe or pressing against large detectors in order to overcome the short range of alpha particles. These methods have a low alpha collection efficiency, and can miss contamination on less accessible surfaces. We have investigated the sensitivity and practicality of measuring the entire subject simultaneously using the technique of ionization monitoring. The goal is to create a booth that personnel step into quickly during egress from radiological facilities. The detection technique relies on a breeze of air passing over the subject. Alpha emission produces copious ions in the ambient air which are transported by the air current to an ion collector, resulting in a small electrical current proportional to the amount of contamination. Results indicate a conservative sensitivity of 3000 disintegrations per minute localized to one of five areas of the body in a measurement lasting less than 2 minutes.

Registration of Alpha Particles of a Wide Energy Range in Polycarbonate

To broaden the registration energy range from 1.5 MeV up to about 5 MeV under one single electrochemical etching (ECE) processing of Lexan polycarbonate at about 27°C with the aim of reducing the background, and the ECE time, etc., methanol (CH 3 OH) was added as a mixture with PEW (a mixture of potassium hydroxide, ethanol, and water), under optimised conditions. Registration of alpha particle energies from 0.3 MeV up to about 2.8 MeV in a short etching duration was possible by using of PEWEG solution (a mixture of potassium hydroxide, ethanol, water, and ethylene glycol) as etchant, under optimised conditions.

Cytotoxicity of alpha-particle-emitting astatine-211-labelled antibody in tumour spheroids: no effect of hyperthermia.

The high linear energy transfer, alpha-particle-emitting radionuclide astatine-211 (211At) is of interest for certain therapeutic applications; however, because of the 55- to 70-microm path length of its alpha-particles, achieving homogeneous tracer distribution is critical. Hyperthermia may enhance the therapeutic efficacy of alpha-particle endoradiotherapy if it can improve tracer distribution. In this study, we have investigated whether hyperthermia increased the cytotoxicity of an 211At-labelled monoclonal antibody (MAb) in tumour spheroids with a radius (approximately 100 microm) greater than the range of 211At alpha-particles. Hyperthermia for 1 h at 42 degrees C was used because this treatment itself resulted in no regrowth delay. Radiolabelled chimeric MAb 81C6 reactive with the extracellular matrix antigen tenascin was added to spheroids grown from the D-247 MG human glioma cell line at activity concentrations ranging from 0.125 to 250 kBq ml(-1). A significant regrowth delay was observed at 125 and 250 kBq ml(-1) in both hyperthermia-treated and untreated spheroids. For groups receiving hyperthermia, no increase in cytotoxicity was seen compared with normothermic controls at any activity concentration. These results and those from autoradiographs indicate that hyperthermia at 42 degrees C for 1 h had no significant effect on the uptake or distribution of this antitenascin MAb in D-247 MG spheroids.

Study of ion implantation profiles by the PIXE technique

The RBS technique is currently used with alpha particles as a non-destructive way of studying concentration depth profiles. This technique is especially convenient in characterizing heavy atom distributions inside a matrix of lighter elements, and its use is less convenient in the case of light elements in a matrix of heavier ones. On the other hand the probing depth is limited by the small range of alpha particles in the matrix. We present here a new procedure for determining ion implantation profiles by means of the PIXE technique and by varying the impinging proton energy. As an example, silicon ions of two energies have been implanted into pure titanium samples in order to obtain implantation profiles with a double peak. The results presented here are in good agreement with the calculations using the TRIM code.

A Personal Neutron Dosimetry System Based on Etched Track and Automatic Readout by Autoscan 60

An instrument for reading chemically etched CR-39 elements, the Autoscan 60, has become commercially available. Based on this readout system a new personal neutron dosemeter badge has been developed. PN3 detectors (NE Technology) are used with a two step etching process. The radiators are polyethylene (PE), polyethylene with 6 Li and aluminium. In a nuclear reaction of 6 Li with thermal neutrons alpha particles and tritons ( 3 H) are produced. While the range of alpha particles (9 μm) is too short to be detected with a two step etching procedure, tritons (range = 52 μm in CR-39) easily reach the sensitive layer of the detector and increase the response for thermal neutrons to a value determined by the 6 Li concentration in the PE radiator. Aluminium inhibits the production of recoil protons and hence, causes a lower response to fast neutrons as compared to PE. From the ratio of the readings behind PE and Al, spectral information can be derived, especially in accident situations when the track density is high and a radiation field analysis is required. For extremely high track densities a microscope is used for evaluation, since automatic counting by Autoscan 60 saturates at doses above 50 mSv. The system has been tested for reproducibility, linearity, energy dependence up to 66 MeV neutron energy, angular dependence, radon background response and multiple use of CR-39 detectors.

Track etch velocity study in a radon detector (LR 115, cellulose nitrate)

For radon dosimetry, complete knowledge of the detection area of the detector used for alpha particles emitted by radon and its two daughters (Po 218 and Po 214) is compulsory. Latent tracks in the detector induced by alpha particles are enlarged in a hot hydroxide sodium bath to make them observable by microscopy. This paper deals with the determination of the track etch velocity (VT). We compared two different approaches to calculate the VT: for the first one, the VT in considered as a function of the alpha particle energy. The VT is determined by using a track etch model based on the experimental study of the track diameters for normal incidence versus alpha particle energies. For the second approach, we assumed that the VT was directly correlated with the ionisation rate (I) created all along the alpha particle range in the detector. This ionisation rate, which depends directly on the alpha particle energy was calculated using the TRIm programme. The knowledge of the VT enabled us to determine the critical incidence angle for each energy under which the alpha particle did not induce an observable track. Results for each approach were compared with the experimental data obtained with a specific irradiator system. Finally, track detection efficiencies of LR 115 for radon and their standard deviations are proposed for a simple configuration.

Radonography

Radonography

The effect of alpha-particle and proton irradiation on the electrical and defect properties of n-GaAs

Radiation damage effects were studied in n-GaAs grown by organo-metallic vapour phase epitaxy (OMVPE) for a wide range of alpha-particle (2.0 MeV and 5.4 MeV) and proton (2.0 MeV) particle fluences, using an americium-241 (Am-241) radio-nuclide and a linear Van de Graaff accelerator as the particle sources. The samples were irradiated at 300 K, after fabricating palladium Schottky barrier diodes (SBDs) on the 1.2 × 10 16 cm 3 Si-doped epitaxial layers. The irradiation-induced defects are characterized using conventional deep level transient spectroscopy (DLTS). A correlation is made between the change in SBD characteristics and the quantity and type of defects introduced during irradiation. It is shown that the two parameters most susceptible to this irradiation are the reverse leakage current of the SBDs and the free carrier density of the epilayer. The introduction rate and the “signatures” of the alpha-particle and proton irradiation-induced defects are calculated and compared to those of similar defects introduced during electron irradiation.

Alpha contamination monitoring of surfaces, objects, and enclosed areas

The usefulness of traditional alpha detectors for contamination monitoring is limited by the size and sensitivity of the detectors and by the short range of alpha particles in air. The long-range alpha detector (LRAD) detects the ions produced by the alpha particles passing through air, rather than the alpha particles themselves, limiting LRAD detection by the range of the ions (tens of meters), rather than the range of the alpha particles (a few centimeters). Since the LRAD collects all ions simultaneously, an LRAD monitor is sensitive to all of the sources of contamination contained within it. The electronic noise within the LRAD can be reduced so that better sensitivity than traditional detectors is also possible. These advantages are used in the object, pipe, and duct, floor, and soil surface monitors discussed. The design of these monitors and field test results are presented. >

LRAD-Based Alpha-Particle Contamination Monitoring of Personnel and Equipment

Traditional alpha-particle contamination monitors are limited in usefulness because of the short range of alpha particles in air. This range limitation makes it impossible to adequately monitor for...

Long-range alpha detector.

Historically, alpha-particle detectors have been limited by the very short range of alpha particles in air. This results in a number of problems inherent to alpha contamination detectors, such as relatively poor sensitivity, geometry limitations, and inefficient monitoring techniques. In this paper, we document tests of a new long-range alpha detector. The charges generated by the interaction of alpha particles with air can be transported over significant distances (several meters) in a moving current of air generated by a small fan. An ion chamber located in front of the fan measures the current carried by the moving ions and, hence, detects the alpha decays.

Assessment of the radioactivity of environmental samples by SSNTD technique

Plant samples collected from Transdanubia and spring water samples collected from the Highland of Lake Balaton were measured by alpha autoradiography with CR-39 detector. Standards were made in order to examine the influence of the sample matrix on the correlation between the track density and radioactivity concentration. The effective range of uranium alpha particles in grass ash was found to be 1.35×10-3 g/cm2 and that of the dry residues of water 8.26×10-4 g/cm2 The nominal uranium concentration of the spring water samples collected in 1989–1990 was found to be 0.5–3 μg/1 and that of ash samples 0.15–0.25 ppm. For the plant samples collected just after the Chernobyl accident this value was 0.5–2 ppm.

Giant Radiation-Induced Color Halos in Quartz: Solution to a Riddle

The radii of radiation-induced color halos(RICHs) surrounding radioactive mineral inclusions in mica generally correspond closely to the calculated range of common uranogenic and thorogenic alpha particles in mica. Many exceptions are known, however, and these variants have led investigators to some rather exotic interpretations. Three RICHs found in quartz are identified as aluminum hole-trapping centers. Whereas the inner radii of these RICHs closely match the predicted range of the most energetic common alphas(39 micrometers), the color centers observed extend to 100 micrometers. Migration of valence-band holes down a radiation-induced charge potential might account for enigmatic RICHs. Such RICHs provide natural experiments in ultraslow charge diffusion.

Diagnosis of laser produced plasmas using fusion reaction products

Experiments have been performed at the Central Laser Facility, Rutherford Appleton Lab., UK. using novel techniques in which laser produced plasmas have been diagnosed by measurements of the charged thermonuclear reaction products. Two types of experiment are being reported here. Firstly, thermonuclear alpha particles from an exploding pusher target have been used to determine the growth of the Rayleigh–Taylor instability in a separate laser driven planar foil. The resulting alpha particle range loss distributions provide a direct measurement of the foil thickness distribution and hence the instability. The R–T instability has been observed in a number of foils with range losses varying between almost zero to over lOμm. Secondly, a thermonuclear particle backlighting technique has been used in the measurement of the stopping power of hot plasma for different materials. The ratio of plasma stopping power to that of the cold material is measured and compared to a value obtained from theoretical modelling. The solid state nuclear track detector CR–39 has been used as a diagnostic for these experiments. A sophisticated image analysis system has been developed to enhance and improve data recovery.