Absorption beta particle

Self-absorption. Beta particles have a continuous energy spectrum extending from zero energy up to a maximum energy max. K a flat beta source is measured with a thin absorber of thickness L between the source and detector, the count rate / is very closely represented by... 

Am is produced when 239Pu is exposed to neutrons, such as may occur in nuclear reactors. (239Pu, it should be noted, is produced when uranium 238 [238U], is exposed to neutrons.) The reaction sequence involves the successive absorption of neutrons and emission of gamma rays, written as (n,y) and the emission of a beta particle, (3. ... 

The adsorption of ATP-14C to surface films of stearic acid and brain lipid was examined over an extended period of time under various conditions (Table I and Figure 6B). Table I shows the short-term results, where adsorption was studied during the first 30 minutes, and evaporation was not a factor. Upon adding stearic acid or brain lipid the measurable radioactivity decreased, probably as a result of displacement of ATP-14C from the surface layer and self-absorption of the beta particles by the lipid film. When PMCG was present, there was a slight but significant increase in the surface adsorption of ATP. The amount of ATP adsorbed was 4 X 10 10 moles/sq. cm. for stearic acid and 2.5 X 10"10 moles/sq. cm. for brain lipid. If the lipid concentration in the surface is assumed to be about 8 X 10 10M (as phospholipid in the case of brain lipid), the molar ratio of ATP to lipid would be about 0.5 for stearic acid and 0.3 for brain lipid. 

Beta particle absorption Compound radioisotopic decay Radioisotopic decay Introduction to Geiger detectors Introduction to counting statistics... 

For samples that emit beta particles, the sample must be evenly distributed, with defined and uniform thickness. Quantifying geometry and self-absorption of beta particles is unreliable for an unevenly deposited source. 

Preparation of a Beta-particle Self-absorption Curve for 40K... 

To quantify beta-particle self-absorption in KC1 samples of varying thicknesses. 

This experiment examines the count rate as a function of sample thickness. All other variables are held constant (except for a small change in source-detector distance). As the sample becomes thicker, more of the beta particles are absorbed in the sample itself. This is called self-absorption, and is shown in Figure 4.1. In thin samples, self-absorption is relatively small or negligible, but in thick samples it is measurable and must be considered when calculating the counting efficiency. 

This experiment examines the self-absorption of the beta particles emitted by 40K (t1/2 = 1.28 x 109 a, Emax = 1.311 MeV, 89.3%), a naturally-occurring isotope of potassium (abundance = 0.0117%), in potassium chloride (KC1) salt. The degree of beta-particle self-absorption (including self-scattering) depends on the energy of the beta particles, the sample matrix elemental... 

Beta particle self-absorption can be approximated as in Equation 4.1 ... 

The formula for the self-absorption factor is exact for gamma rays (see Experiment 3) but approximate for beta particles. That it is applicable at all is due to the near-linear decrease of the logarithm of the count rate with absorber thickness of a beta-particle group (see Figure 2.6 in the Radioanalytical Chemistry textbook). The obvious deviation is that this relation ends at the range of the maximum-energy beta particle, whereas it continues indefinitely for gamma rays. 

The simplest and most direct reliable way to characterize the self-absorption of beta particles in a sample is to obtain a self-absorption curve by counting the same radionuclide in aliquots of a solid sample over a range of sample thickness. Aliquots can be prepared with the same specific activity (activity per unit mass) but with different masses, in identical planchets. The sample aliquots are counted and the results are presented in graphic form for interpolating the self-absorption factor for the sample mass of interest. 

You are preparing to count beta particles from samples that contains low levels of "Mo. The final counting form is Mo03. Outline an experiment to prepare a "Mo beta self-absorption curve. How would the self-absorption be used to correct the observed counting activity in actual measurements (consider Tc-99m ingrowth) ... 

In the second separation, uranium is extracted from thorium. Ethyl acetate is the extractant for uranium, which is bound in a nitrate complex. Thorium remains in the aqueous phase. Thorium is then co-precipitated with Nd(OH)3 to avoid absorption of the beta particles emitted by 234Th and 234mPa by the large amount of NH4N03 if the solution were simply evaporated and counted. The filter with Nd(OH)3 is mounted on a planchet for counting beta and alpha particles. 

Evaluate the effect of beta-particle absorption in residual oxalic acid on the count rates of the initial uranium solution. 

Use calculations as shown in the beta-particle self-absorption experiment ( 4) or a comparison of the two sets of efficiency values with and without added mass in Experiment 2 to suggest that the self-absorption of 90Y beta particles is small for this experiment. 

D. The external radiation hazard from exposure to tritium is extremely small, because the beta particles emitted cannot penetrate the dead layer of skin. However tritium is easily internalized through inhalation and absorption through the skin. The low energy beta radiation from the tritium is an internal hazard only (i.e., the isotope must get inside your body to cause damage). 

The use of beta particle gauging is described for the measurement of blast wave density from the detonation of large charges of high expl on the surface, eg, 500-ton TNT spherical and hemispherical chafes. The basic principle of the gauge is the measurement of the varying absorption of beta particles caused by density changes... 

Radiation from radioactive sources can be detected and measured in essentially Ihe same way as X-radialioii (Sections l2B-4and 12B-S). Gas-filled chambers, scintillation counters, and semiconductor detectors are all sensitive to alpha and beta particles and to gamma rays because absorption of these particles produces ionization or photoelectrons, which can in turn produce thousands of ion pairs. A detectable electrical pulse is thus produced for each particle reaching the transducer. 

On the other hand, the low concentration of a radionuclide provides opportunities for use as tracer in chemical and physical studies. In radioanalytical chemistry, one benefit is that the addition of a stable-element carrier permits analysis without the requirement of quantitative analyte recovery. Another benefit is the opportunity to deposit very thin sources that minimize self-absorption in a source of alpha-and beta-particle radiation. 

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