Helium ion irradiation

FIGURE 24.19 Relative change of the electrical resistance in VN (a) and CrN (b) coatings as a function of helium ion irradiation dose. (From Guglya, A. et ah, Radiat. Eff. Defects Solids, 162(9), 643, 2007. With permission from Taylor Francis Group.)... 

FIGURE 24.20 (a) Helium bubble density as a function of depth from the surface in Cu/V 50 nm and CuA 2.5 nm nanolaminates, (b) Hardness change of Cu/V nanolaminates as a function of the individual layer thickness—h. (From J. Nucl. Mater., 385(3), Fu, E., Carter, J., Swadener, J. et al.. Size dependence enhancement of helium ion irradiation tolerance in sputtered Cu/V nanolaminates, 629-632, Copyright 2009, with permission from Elsevier.)... 

Guglya, A., Neklyudov, I., Vasilenko, R. 2007. Effect of helium ion irradiation on the structure and electrical resistivity of nanocrystaUine Cr-N and V-N coatings. Radat. Eff. Defects Solids 162.9 643-649. 

Yamauchi Y, Sakurai T, Hirohata Y, Hino T, Nishikawa M (2002) Blue shift of photoluminescence spectrum of porous silicon by helium ion irradiation. Vacuum 66(3-4) 415—418 Zanoni R, Righini G, Mattogno G, Schirone L, Sotgiu G, Rallo F (1999) X-ray photoelectron spectroscopy characterization of stain-etched luminescent porous silicon films. J Lumin 80 159-162... 

Simulation of the neutron-induced damages using triple ion beams is schematically shown in Fig. 7. A proton and a helium ion are provided by the ion implanter and the single-ended accelerator, respectively. Heavy ions, such as iron or silicon, accelerated by the tandem accelerator, are injected into the target simultaneously. For example, the SiC/SiC composite was tested under triple ion beam irradiation consisting of a 380-keV proton, a 1.2-MeV helium ion, and a 7.8-MeV Si " ion. The triple irradiation system is equipped with an energy degrader and a beam scanner for uniform three-dimensional (3-D) irradiation. 

A light-ion microbeam system connected with the 3-MV single-ended accelerator was developed for high-resolution ion beam microanalysis [37]. The highest spatial resolution of 0.25 pm was achieved for 2-MeV proton and helium ions. The beam spot size was estimated from the intensity distribution of the secondary electrons emitted from a silicon relief pattern irradiated with the 2-MeV helium ion microbeam as shown in Fig. 10. 

The simultaneous irradiation with hydrogenic and helium ions can also present a serious blistering problem because of synergistic effects. Although there is a paucity of data, a D-T fusion environment is highly conducive to such synergistic effects. 

H. Atsumi, S. Yamanaka, P. Son, M. Miyake, Thermal desorption of deuterium and helium from ion irradiated graphite, J. Nucl. Mater. 133-134 (1985) 268... 

The mass spectrum of isopropyl acetate contained a fairly strong signal at mfe 61, [equation (140], corresponding to the formation of acetic acid, on irradiation of liquid isopropyl acetate with helium ions... 

The H2 yield from polystyrene irradiated with y-rays is two orders of magnitude less than that in polyethylene. The H2 yields increase with increasing LET for all the polymers shown in Fig. 2, but the increase is not linear. There is a considerably greater increase for polystyrene than polyethylene. A 5 MeV helium ion, a-particle, gives a G-value for H2 of 4.6 molecules/100 eV from polyethylene and 0.15 molecule/100 eV from polystyrene [11], The large increase in H2 yield for polystyrene suggests that this material is not as radiation inert as typically thought. The use of yields determined with y-rays for heavy ion radiolysis would clearly underestimate the production of H2 in transuranic waste materials. More experiments coupled with sophisticated models are required to predict H2 yields in other unexamined polymers and in complex mixtures. 

FIG. 2. Yield of H2 as a junction of track average LET for polyethylene, PE, polypropylene, PP, poly(methyl methacrylate), PMMA, and polystyrene, PS, irradiated with frays, protons, helium ions and carbon ions [11]... 

No. 97 has been obtained, by irradiation of americium (96) with helium ions accelerated in the cyclotron, as a nuclide of half-life 4-6 hours and probable atomic weight 243. It decays by electron capture. For it, the name berkelium, Bk, has been suggested. 

Californium — (State and University of California), Cf at. wt. (251) m.p. 900°C sp. gr. 15.1 at. no. 98. Californium, the sixth transuranium element to be discovered, was produced by Thompson, Street, Ghioirso, and Seaborg in 1950 by bombarding microgram quantities of Cm with 35 MeV helium ions in the Berkeley 60-inch cyclotron. Californium (111) is the only ion stable in aqueous solutions, all attempts to reduce or oxidize californium (111) having failed. The isotope Cf results from the beta decay of Bk while the heavier isotopes are produced by intense neutron irradiation by the reactions ... 

The papers [79,80] give consideration to the radiation tolerance of ferrite steel hardened with yttrium oxide (YjOj) particles of 20 nm. Two types of radiation treatment were used, in particular irradiation with helium ions that results in the formation of barely point defects and bombardment with high-energy (150 keV) iron ions. In the latter case, defects were mainly formed in displacement cascades, whose size ranges within 2-3 nm. It has been established that the changes in the distribution of dispersed phase and its component composition were not observed whatever methods were used to create defects. 

The multilayered films of Cu/V, Cu/Nb, and Fe/W with the thickness of some layers varying in the range of 2.5-200 nm were exposed to irradiation with helium ions and the formation of gas-filled pores has been analyzed [81-84]. Whatever the combination of metals is, helium bubbles accumulate along the boundaries between layers. Moreover, as the thickness of layers decreases the pore size reduces (Figure 24.20a). At a thickness of 2.5 nm, the resolution of electron microscope failed to show any helium formations. In addition, it was noticed that the hardening of multilayered structures degrades as the thickness of individual films decreases (Figure 24.20b). 

De Paz et have described recently a new technique with which cluster dissociation energies can be determined. Their study dealt with the proton hydrates H (H20) . The proton hydrates were produced by electron irradiation of water vapor in the 0.1-3-Torr range in the first ion source of a tandem mass spectrometer. The ion source of the second stage served as collision chamber and was filled with helium. Ions H (H20)fc formed by collisions of the primary H (H20) with He were detected with the second mass spectrometer. The energy required for the process... 

Fourier transform IR measurements were used to investigate PVDF films which had been irradiated by means of heavy ions (krypton ions) and electrons. Irradiation with krypton ions was carried out in the presence of helium, hydrogen, deuterium and oxygen. Triple bonds were characteristic of krypton ion irradiation. Double bonds (isolated and conjugated) occurred with both types of irradiation but concentrations were higher with the krypton radiation. The results, including the role of oxygen on the chemical modifications, were discussed. 36 refs. 

Helium ions from an electron cyclotron resonance source were used to study the effects on the irradiation prior to anodization on the PL spectrum of porous silicon, comparing them with the post-anodization effects (Yamauchi et al. 2002). 

Element 94 was named plutonium after the planet discovered last, Pluto. In 1941, the first 0.5 /rg of the fissionable isotope Pu were produced by irradiating 1.2 kg of uranyl nitrate with cyclotron-generated neutrons. In 1948, trace amounts of Pu were found in nature, formed by neutron capture in uranium. In chemical studies, plutonium was shown to have properties similar to uranium and not to osmium as suggested earlier. The actinide concept advanced by G. T. Seaborg, to consider the actinide elements as a second / transition series analogous to the lanthanides, systematized the chemistry of the transuranium elements and facilitated the search for heavier actinide elements. The actinide elements americium (95) through fermium (100) were produced first either via neutron or helium-ion bombardments of actinide targets in the years between 1944 and 1955. 

Activation methods are based on the measurement of the radioactivity or radiation produced in samples when they are irradiated with neutrons or charged particles, such as hydrogen, deuterium, or helium ions. An overview of the most common type of neutron activation is shown in Figure 32-6. Here, a neutron is captured by the target nucleus to form an excited compound nucleus. The compound nucleus de-excites almost instantaneously by emission of one or more characteristic prompt gamma rays. In many cases a new radioactive nucleus is formed, which can undergo /3 decay to an exited product nucleus with the emission of another characteristic delayed gamma ray. 

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