Range alpha particle

Figure 2.3. Alpha-particle range in air and aluminum. (Data from ICRU 1993, pp. 192 and 213.)...

In the equation, A is the source activity in Bq, 91 is the alpha particle range in mg/cm, a is the source area in cm, m is the source mass in mg, and x is the source thickness in mg/cm. The equation indicates that, for samples with a constant activity per unit mass, the surface flux decreases linearly with thickness to one-fourth the disintegration rate when the source thickness equals the range, which is about7 mg/cm for the 5.5-MeV alpha particle emitted by Am. Beyond this thickness, the surface flux is predicted to remain constant ... 

Equation (7.1b) shows that the counting efficiency varies inversely with the sample mass when the thickness exceeds the alpha-particle range, i.e., at infinite thickness. ... 

The PIXE method using 30 MeV a-particles, has been applied for the elemental analysis of metal targets by Bauer et al. (1978) who have reported the advantage of better accuracy and deep penetration ( 100 pm) of a-particles into the sample. The Ka X-ray yield of thick targets for alpha particles ranging from 1 to 100 MeV was reported by Castiglioni et al. (1992). The heavy ions such as C, N+, 0+, and Ne" " are not very suitable for PIXE studies mainly because the cross-sections for X-ray production are too small (not... 

Boron [7440-42-8] B, is unique in that it is the only nonmetal in Group 13 (IIIA) of the Periodic Table. Boron, at wt 10.81, at no. 5, has more similarity to carbon and siUcon than to the other elements in Group 13. There are two stable boron isotopes, B and B, which are naturally present at 19.10—20.31% and 79.69—80.90%, respectively. The range of the isotopic abundancies reflects a variabiUty in naturally occurring deposits such as high B ore from Turkey and low °B ore from California. Other boron isotopes, B, B, and B, have half-Hves of less than a second. The B isotope has a very high cross-section for absorption of thermal neutrons, 3.835 x 10 (3835 bams). This neutron absorption produces alpha particles. 

Because the cytotoxic effects of the energetic lithium-7 and alpha particles are spaciaHy limited to a range of only about one-ceU diameter, the destmctive effects are confined to only one or two cells near the site of the event. Thus BNCT involves the selective deUvery of sufficiendy high concentrations of B-containing compounds to tumor sites followed by the irradiation of these sites with a beam of relatively nondestmctive thermal neutrons. The resulting cytotoxic reaction can then in theory destroy the tumor cells that are intimately associated with B target. 

General. The use of alpha particles instead of electrons as in conventional ion-molecule reaction mass spectrometers introduces a difference in primary ionization conditions which is not as great as might be supposed. Thus, the primary ion mass spectra produced by alpha particles are very similar to these produced by say 70-e.v. electrons (30). Secondary electrons produced by the alpha particles are responsible for more than 50% of the total ionization. The energies of these electrons peak in the range 20-100 e.v. so that again the primary ions will be similar to those produced by 70-e.v. electrons. 

The range in tissues and linear energy transfer (LET) depend on the type of radiation emitted and its energy. The potent lethality of Auger and low-energy conversion electrons is demonstrated by intranuclear localization of the radioisotope due to their short ranges (about one cell nucleus in diameter). Alpha particles have ranges of several cell diameters (40-90 pm) and are effective in... 

When Rn-222 decays with the emission of a 5.49 Mev alpha particle the recoiling energy of the newly formed Po-218 atom is 0.10 Mev which is sufficient for a range of about 50 micrometers in air. However, the velocity of the recoiling Po-218 atom is still small compared with that of the orbital electrons. 

In vivo the doses are always not only due to internal alpha but also due to the external gamma irradiation, which must be taken into account, especially in the low dose range. Therefore in vitro experiments with alpha particles of radon daughters at doses comparable to the in vivo investigations have been carried out (0.05 to 3 mGy). The method is described. Preliminary results show similar dose response as at our in vivo studies. 

Abstract The equation of state (EOS) of nuclear matter at finite temperature and density with various proton fractions is considered, in particular the region of medium excitation energy given by the temperature range T < 30 MeV and the baryon density range ps < 1014 2 g/cm3. In this region, in addition to the mean-field effects the formation of few-body correlations, in particular light bound clusters up to the alpha-particle (1 < A < 4) has been taken into account. The calculation is based on the relativistic mean field theory with the parameter set TM1. We show results for different values for the asymmetry parameter, and (3 equilibrium is considered as a special case. 

Alpha particles are relatively large particles and are emitted with a limited number of energy levels. They carry a double positive charge and as a result attract electrons from the atoms of the material through which they pass, causing ionization effects. They have an extremely short range, even in air, and as a result present very little hazard as an external source of radiation but their effects within living cells or tissues can be serious. 

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