Alpha-particle Bombardment Research Articles

Dependence of surface recombination velocity of p-type InSb on temperature and alpha particle bombardment

The temperature dependence of surface recombination velocity S of p-type InSb upon alpha particle bombardment is studied from photomagnetoelectric measurements between 16 and 80 K. Warming the specimen above 16 K we observe an increase of S followed by an abrupt fall of S at about 30–40 K. Further warming produces a strong maximum of S at about 100–120 K. Bombardment with alpha particles increases S at all temperatures up to about 120 K. The whole behavior is explained on the basis of a model proposed by the authors in an earlier paper.

Production of 119 mSn by alpha particle bombardment of 116Cd and its carrier-free separation

The production method of high specific 119 m Sn was studied by using the reaction of alpha particles with enriched cadmium. The excitation function for the 116Cd( α, n) 119 m Sn reaction and its thick-target yields were investigated with the stacked foil technique at the incident alpha particle energy of 25 MeV. When the incident alpha particle energy of 20 MeV was chosen, 0.1 μCi/μA·h of 119 m Sn could be produced at the end of bombardment. The procedure for the carrier-free separation of tin activity from the cadmium target and the copper backing by coprecipitation, organic solvent extraction and anion exchange is described.

A new radioisotope for lung ventilation studies: 19-neon.

Neon 19, 17-second positron-emitting radioelement, is produced continuously by 23MeV alpha particle bombardment of oxygen. For a 12 muA particle current the method of preparation described delivers 14 mCi of neon 19 per min to the functional exploration room. The radiochemically pure radioactive gas is diluted in air and breathed continously by the patient lying under a positron tomographic camera. The regional lung ventilation distribution is obtained on 2 cm thick sections of organ with a transverse resolution of 17 mm. Quantification of the ventilation output per unit lung volume is contemplated.

Measurements of L X-ray production and subshell ionisation cross sections of gold by light- and heavy-ion bombardment in the energy range 0.4-3.4 MeV

The L X-ray production and subshell ionisation cross sections of gold have been measured by proton, alpha particle, carbon, nitrogen and oxygen bombardment in the energy range 0.4-3.4 MeV. These data are compared with the predictions of the plane-wave Born approximation including the binding energy, Coulomb deflection and relativistic corrections. Satisfactory agreement has been obtained between theory and experiment except for the cross sections of the L2-subshell ionisation induced by heavy ions (12C, 14N, 16O). The theory underestimates these cross sections by almost one order of magnitude.

Ionizing central collisions and nuclear excitation

The K-shell ionization of Z=24−83 targets in very close collisions ( b=2−20 fm) with 7–12 MeV protons is studied. Nuclear K X-ray satellite intensities for Z≧50 under proton and alpha particle bombardment are characterized. Problems of beam modulation diagnostics and a correction formula for ionizing double scattering are briefly discussed. The ionization probability at 7 MeV for the lower-Z targets rises a factor 1.8 above the semiclassical relativistic value calculated with l=0, 1, and 2 angular momentum states of the free electron. The same calculation gives results somewhat above the data points at 7, 10, and 12 MeV for Z=42−50. A determination of the average nuclear lifetime of 3.4×10 −17 for 51 113Sb at 15 MeV excitation from the K X-ray spectrum is described.

Neutron Yields from Alpha-Particle Bombardment

Thick-target (α,n) neutron yields have been measured for 6,7,NATLi, 9Be,10,11,NATB, Pb19F2 and Zn19F2, NATMg, 27Al, NATSi, and 28SiNATO2. From the Pb19F2 and Zn19F2 data, we have extracted the neut...

Compcon Wrap-up

The conference theme of "exploding technology" seemed particularly appropriate to Session 18, "Integrating Semiconductor Memories into Systems," which probed some of the problems attendant upon increasing chip densities. Discussing alpha particle bombardments, Michael Geilhufe of Intel described the effects of such phenomena as random, non-recurring, single-bit errors. The rate of these "soft errors" today, said Geilhufe, is an order of magnitude greater than hard error rates. For example, with an error rate of 0.1 percent per 1K hours for a 16K RAM, a 16 x 64K memory would have an MTTF of 1.75 years, whereas a 16-megabyte memory would only have a MTTF of less than four days. Memory design alternatives such as automatic error correction, periodic memory purges, and systems redundancy must be considered. Periodic memory purges may be necessary since soft errors may accumulate in infrequently accessed memory regions.

Auger Electrons from Zinc and Cadmium Vapors by Proton and Alpha Particle Bombardments

The L- and M-shell Auger electrons from vapors of zinc and cadmium, respectively, excited by protons and alpha particles at 0.5–2.75 MeV in energy have been observed and compared with those by electron excitation. The simultaneous ionicities for the M-shell of zinc and the N-shell of cadmium are estimated from the shift-energies of Auger peaks, as 0.5 for protons and a few for alpha particles in average. Applying Rutherford scattering of projectiles and known ionizing collisions, the Auger yields are converted to the respective ionization cross sections, which fairly well agree with the theory of binary encounter approximation (BEA).

Alpha particle bombardment of natural nickel target for the production of 61Cu

The optimum conditions were investigated for the production of 61Cu by the alpha-particle bombardment of natural nickel. Formation cross-sections and thick-target yields were obtained for most of the reaction products in the energy range from 10 to 40 MeV. When the incident alpha energy of 21 MeV was chosen, after 2 hr of cooling 2.1 mCi/μA·hr of 61Cu could be produced with a 60Cu contamination of less than 1%. The other reaction products were also analyzed in terms of the corresponding nuclear reactions, and excitation functions were deduced for the 58Ni and 60Ni target nuclides.

The idea of the neutrino

During the 1920's physicists came to accept the view that matter is built of only two kinds of elementary particles, electrons and protons, which they often called “negative and positive electrons.” A neutral atom of mass number A and atomic number Z was supposed to contain A protons, all in the nucleus, and A negative electrons, A–Z in the nucleus and the rest making up the external electron shells of the atom. Their belief that both protons and negative electrons were to be found in the nucleus arose from the observations that protons could be knocked out of light elements by alpha-particle bombardment, while electrons emerged spontaneously (mostly from very heavy nuclei) in radioactive beta decay. Any other elementary constituent of the atom would have been considered superfluous, and to imagine that another might exist was abhorrent to the prevailing natural philosophy.

Production of 61Cu, 62Zn by alpha and 3He particle bombardment of natural nickel (author's transl)

The optimum irradiation conditions were investigated for the production of 61Cu and 62Zn by alpha and 3He particle bombardment of natural nickel. Formation cross sections and thick-target yields were obtained for reaction products in the energy range of 10 to 40 MeV. For the production of 61Cu and 62Zn, the alpha particle bombardment was found superior to the 3He particle bombardment in so far as the yield was concerned. When the incident alpha energy of 21 MeV was chosen, after 2.4 hours of cooling, 2.1 mCi/muA.h of 61Cu could be produced with less than 1% of 60Cu contamination. For the production of 62Zn, when the incident alpha energy of 35 MeV and the target thickness of 57 mg /cm2 were chosen, 97.5 muCi/muA.h of 62Zn could be produced. Radiochemical purity of 62Zn was the highest at 12 hours after the end of bombardment.

K Shell Ionizations of Carbon, Nitrogen, Oxygen, Fluorine and Neon by Proton and Alpha Particle Bombardments

The K Auger electron spectra have been measured for carbon, nitrogen, oxygen, fluorine and neon excited by protons and alpha particles of 0.5–2.6 MeV. In comparison with the spectra obtained by electron impact, the satellite lines have grown more intensively as projectiles become heavier. This indicates the presence of a contribution of simultaneous L shell ionization. A quantitative analysis has been made for the created L vacancies of nitrogen due to N+ p and N+α collisions. The ionization cross sections derived from the Auger yields have been compared with the theories of Born approximation and binary encounter approximation. The deviations from the theories found in O+α, F+α and Ne+α collisions might be explained by a shielding action of L shell electrons against nuclear charge of projectiles.

L Shell Ionizations of Chlorine and Argon by Proton and Alpha Particle Bombardments

The L Auger electron spectra have been observed for chlorine and argon bombarded with protons and alpha particles of 0.3–2.6 MeV in energy. The satellite lines, which are attributable to a simultaneous M shell ionization, have increased in comparison with the spectra obtained by electron impact. The numbers of created M shell vacancies of argon are estimated as 0.3±0.1 and 1.1±0.4 in average for protons and alpha particles at 1.8 MeV, respectively. The ionization cross sections for both projectiles have been compared with the theory of binary encounter approximation, resulting in a few tens percent reduction for argon and an overestimation for chlorine. The projectile z dependence of ionization cross section has been confirmed for chlorine and argon.

Solid state structure effects in flourine X-ray spectra produced by heavy ion bombardment

Flourine X-ray spectra produced by proton, alpha particle and oxygen ion bombardment of targets of LiF, NaF, CaF 2 have been measured. The Kα satellite yields of fluorine are different in each fluorine crystal due to the electronic structure of the compounds, however, the Kα hypersatellite yields are nearly identical.

Energy Dependence of Multiple Inner-Shell Ionization of A1 by Alpha-Particle Bombardment

The excitation of states in Al with single K- plus multiple L-shell vacancies formed by collisions with 0.4-3.0MeV helium ions is studied by observing the x-ray decay associated with filling of the K-shell vacancy. The observed K x rays come from initial states with one K-shell and 0, l, 2, and 3 L- shell vacancies. The absolute cross section for each of these transitions is determined and compared to a calculation using multiple Coulomb ionization. An important result of this experiment is the observation that the ratio of double to single ionization exhibits a maximum at a bombarding energy near the maximum for L-shell ionization. (auth)

Production and separation of cyclotron produced dysprosium-157

A method has been developed to produce dysprosium-157 with the alpha particle bombardment of natural gadolinium. The excitation function for the nuclear reactions producing this radionuclide has been determined and the threshold energy is found to be about 15 MeV. A method is described for the isolation of the clinical product, together with details of its radiochemical and chemical purity.

Absolute Neutron Yields from Alpha-Particle Interaction with Thick Targets of Natural Carbon

Recent measurements of the neutron yield resulting from the alpha-particle bombardment of carbon have disclosed an error in the data reported in the literature. New values of the thick-target yield...

Analytical capabilities of X-ray emission induced in heavy elements by high-energy protons and alpha-particles

The possibility of using high-energy ion beams for analytical purposes is explored. The most promising field is the identification of medium-weight elements by detection of K X-rays following alpha-particle and proton bombardment, where a sensitivity well bellow 1 ppm was predicted. In the case of heavy elements, interferences are possible because of competition of nuclear reactions. In the case of rare earths, the method is interference free, quantities of 0.1 mg/cm2 can be determined.

Self-radiation damage ingrowth in238PuO2

Abstract Self-irradiation damage due to alpha particle and recoil atom bombardment has been studied in 238PuO2. In a well-annealed sample, the room temperature damage ingrowth follows a simple exponential function to the saturation damage level. In incompletely annealed samples, the damage ingrowth curve is discontinuous and exhibits a maximum. This is believed to result from the migration of point defects to residual sinks.

Cross sections for the production of berylium isotopes from the 880 MeV alpha-particle bombardment of carbon

The cross sections for the production of 9Be and 10Be from the 880 MeV α-particle bombardment of carbon have been measured to be 10.6 ± 1.7 and 6.5 ± 1.4 mb. These values are essentially twice the high-energy proton cross sections. It is shown that the effect of the interstellar helium on the distribution of berylium isotopes in cosmic rays is thus less important than had been anticipated.