Alpha particle sources

Terzaghi-Howe M, Ford JR, Turner JE, et al. 1996. Influence of cell position relative to planar alpha-particle sources on survival and preneoplastic transformation of primary rat tracheal epithelial cells. 

SIMS analysis of electrodeposited Th alpha-particle sources gives rise to higher signals for the ThO and ThO/ than for Th. This leads to difficulties in quantitation as the oxide to atomic ion ratios will be sensitive to local oxygen concentrations. Isobaric... 

Goddu SM, Howell RW, Rao DV. Cellular dosimetry Absorbed fradions for monoener-getic eledron and alpha particle sources and S-values for radionuclides uniformly distributed in different cell compartments. J Nud Med 1994 35 303-316. 

Arrangement of Ernest Marsden s experiment A-B, alpha particle source. R-R, gold foil. P, lead plate. S, zinc sulfide scintillation screen. M, microscope. 

The resonant reactions of alpha particles with boron have been very fully studied by Shire et al., who observ- ed protons, deuterons, neutrons and gamma rays from and protons from B. Their yield curves for B are shown in Fig. 45 that for gamma radiation is extended to higher energies by Talbott and Heydenburg [43] and that for neutrons by Walker with low resolution, using a polonium alpha particle source. 

Curium may be used as a thermoelectric power source (a never-ending battery) for space flights. Curium was also the alpha particle source for the Alpha Proton X-Ray Spectrometer on Mars. 

Radium is not the only element to have a radiochemistry related to practical implications. Beryllium is an excellent moderator and therefore has had a long history of use in the nuclear weapon and power industries. Mixed with an alpha-particle source, commonly radium, beryUium also provides a good laboratory source of neutrons, as shown in Equation (13.13) ... 

Figure 22 Pulse height spectra obtained with a BP-on-Si device with and without an "Am 5.5-MeV alpha particle source present. (From Ref. 73.)...

Source of narrow beam of fast-moving alpha particles... 

However, some of the conditions in the alpha ion source do differ significantly from those in conventional ion-molecule sources. The most important difference is caused by the absence of an electric field and the mode of sampling. Positive and negative particles are carried out by mass flow. Therefore it is necessary to understand the reaction and sampling conditions at least qualitatively. For this reason we are devoting this section to a description of the conditions and a discussion of some experiments which were done specifically to obtain a better understanding of the sample prehistory. 

A is the manufacturer s rated activity based on calorimetric measurement of the heat evolved by the source. Since one 3-m.e.v. alpha particle produces 3 X 104 ion pairs in air of 1 mg. sq. cm. 1 density we calculate 7, the number of ion pairs produced per second above the leak in 1 cc. air at p torr pressure as ... 

During the red giant phase of stellar evolution, free neutrons are generated by reactions such as C(a,n) and Ne(a,n) Mg. (The (ot,n) notation signifies a nuclear reaction where an alpha particle combines with the first nucleus and a neutron is ejected to form the second nucleus.) The neutrons, having no charge, can interact with nuclei of any mass at the existing temperatures and can in principle build up the elements to Bi, the heaviest stable element. The steady source of neutrons in the interiors of stable, evolved stars produces what is known as the "s process," the buildup of heavy elements by the slow interaction with a low flux of neutrons. The more rapid "r process" occurs in... 

Radioactive source of alpha particles, embedded in lead to absorb most of the radiation. 

The diagram above shows the results of Rutherford s experiment in which he used a radioactive source to shoot alpha particles at a thin sheet of gold foil. Based on these results, what were Rutherford s conclusions ... 

Marechal CN, Telouk P, Alberede F (1999) Precise analysis of copper and zinc isotopic compositiorrs by plasma-source mass spectrometry. Chem Geol 156 251-273 Martin P, Hancock GJ, Paulka S, Akber RA (1995) Determination of Ac-227 by alpha-particle spectrometry. Appl Radiat Isot 46 1065-1070... 

Figure 4.13. Schematic diagram of a tandem accelerator source of high energy alpha particles.

Edwards et al. (1980) used a Cm-242 source to irradiate externally a thin film of blood. The energy of 4 9 MeV of the alpha particles were almost entirely absorbed by the blood. The dicentrics yield was linear from 0.11 to 4 2 Gy. From this resulted a RBE of 17.9 with respect to Co-60 gamma rays. It was, however, only 6.0 at the initial slope. To explain this RBE, which was low compared to that expected from neutron experiments, a model is presented taking into account cell killing and mitotic delay. 

Neutrons have no electrical charge and have nearly the same mass as a proton (a hydrogen atom nucleus). A neutron is hundreds of times larger than an electron, but one quarter the size of an alpha particle. The source of neutrons is primarily nuclear reactions, such as fission, but they are also produced from the decay of radioactive elements. Because of its size and lack of charge, the neutron is fairly difficult to stop, and has a relatively high penetrating power. 

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