MeV Heavy Ion Research Articles

The 300 MeV proton and heavy ion accelerator complex for SESRI project in China

The 300 MeV proton and heavy ion accelerator complex, which is the key part of SESRI (Space Environment Simulation and Research Infrastructure) project, is currently under construction in China. It comprises an 18 GHz high charge-state ion source, a 108.48 MHz cascaded linac injector consisting of a four-rod RFQ and three interdigital H-mode drift tube linacs, a compact synchrotron, and three irradiation terminals. The extensive ion species from proton to 209Bi32+ will be injected into the synchrotron using multi-turn injection method. The third-order resonance and RF-knockout extraction scheme is adopted to provide quasi-continuous spill for irradiation experiments. The general design of the accelerator complex and simulation results are discussed in this paper.

A Novel Microshear Geometry for Exploring the Influence of Void Swelling on the Mechanical Properties Induced by MeV Heavy Ion Irradiation.

Small disks are often the specimen of choice for exposure in nuclear reactor environments, and this geometry invariably limits the types of mechanical testing that can be performed on the specimen. Recently, shear punch testing has been utilized to evaluate changes arising from neutron irradiation in test reactor environments on these small disk specimens. As part of a broader effort to link accelerated testing using ion irradiation and conventional neutron irradiation techniques, a novel microshear specimen geometry was developed for use with heavy-ion irradiated specimens. The technique was demonstrated in pure Cu irradiated to 11 and 110 peak dpa with 10 MeV Cu ions. At 11 peak dpa, the Cu specimen had a high density of small voids in the irradiated region, while at 110 peak dpa, larger voids with an average void swelling of ~20% were observed. Micropillar and microshear specimens both exhibited hardening at 11 dpa, followed by softening at 110 dpa. The close alignment of the new microshear technique and more conventional micropillar testing, and the fact that both follow intuition, is a good first step towards applying microshear testing to a wider range of irradiated materials.

Interfacial and structural analysis of MeV heavy ion irradiated SiC

Interfacial and structural analysis of MeV heavy ion irradiated SiC

Mechanical properties of 6H-SiC irradiated by neutron and MeV heavy ions: A nanoindentation and finite element method study

Understanding the mechanical properties of structural materials under an irradiation environment stands as a major challenge for developing advanced nuclear systems. In this paper, the mechanical properties, including the Young's modulus, yield stress, and hardness, of SiC samples irradiated by neutron and heavy ions (3 MeV C and Si ions) have been investigated by nanoindentation measurement. When the load-depth curves were analyzed by the widely used Oliver-Pharr method, for the samples irradiated at the same displacement damage level (0.1 and 0.2 dpa), both the elastic modulus and hardness of the ion irradiated SiC are significantly higher compared with those of neutron irradiated samples. The discrepancy is mainly attributed to the irradiation induced surface lateral stress in ion irradiated samples, which cannot be taken into account for the Oliver-Pharr method. After carefully considering this effect by the finite element method in simulating the load-depth curves, both the Young's modulus and yield stress of ion irradiated samples agree well with those of neutron irradiated samples. This study reveals that by the combined method of nanoindentation and finite element, the mechanical properties, including the Young's modulus, yield stress and hardness, for neutron irradiated SiC can be reasonably evaluated by MeV heavy ion irradiation.

Monitoring Ion Track Formation Using In Situ RBS/c, ToF-ERDA, and HR-PIXE.

The aim of this work is to investigate the feasibility of ion beam analysis techniques for monitoring swift heavy ion track formation. First, the use of the in situ Rutherford backscattering spectrometry in channeling mode to observe damage build-up in quartz SiO2 after MeV heavy ion irradiation is demonstrated. Second, new results of the in situ grazing incidence time-of-flight elastic recoil detection analysis used for monitoring the surface elemental composition during ion tracks formation in various materials are presented. Ion tracks were found on SrTiO3, quartz SiO2, a-SiO2, and muscovite mica surfaces by atomic force microscopy, but in contrast to our previous studies on GaN and TiO2, surface stoichiometry remained unchanged. Third, the usability of high resolution particle induced X-ray spectroscopy for observation of electronic dynamics during early stages of ion track formation is shown.

MeV ion irradiation effects on the luminescence properties of Si‐implanted SiO2‐thin films

AbstractThe effects of MeV heavy ion irradiation at varying fluence and flux on excess Si, introduced in SiO2 by keV ion implantation, are investigated by photoluminescence (PL). From the PL peak wavelength (λ) and decay lifetime (τ), two PL sources are distinguished: i) quasi‐direct recombination of excitons of Si‐nanoparticles (SiNPs), appearing after thermal annealing (λ > 720 nm, τ ∼ μs), and ii) fast‐decay PL, possibly due to oxide‐related defects (λ ∼ 575‐690 nm, τ ∼ ns). The fast‐decay PL (ii) observed before and after ion irradiation is induced by ion implantation. It is found that this fast‐decay luminescence decreases for higher irradiation fluence of MeV heavy ions. After thermal annealing (forming SiNPs), the SiNP PL is reduced for samples irradiated by MeV heavy ions but found to stabilize at higher level for higher irradiation flux; the (ii) band vanishes as a result of annealing. The results are discussed in terms of the influence of electronic and nuclear stopping powers. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Modification of semiconductor or metal nanoparticle lattices in amorphous alumina by MeV heavy ions

In the present work we investigate effects of MeV heavy ions (from 0.4 MeV Xe to 15 MeV Si) on regularly ordered nanoparticle (NP) lattices embedded in amorphous alumina matrix. These nanostructures were produced by self-assembling growth using magnetron-sputtering deposition. From grazing incidence small-angle x-ray scattering measurements we have found that the used MeV heavy ions do not change the NP sizes, shapes or distances among them. However, ions cause a tilt of the entire NP lattice in the direction parallel to the surface. The tilt angle depends on the incident ion energy, type and the applied fluence and a nearly linear increase of the tilt angle with the ion fluence and irradiation angle was found. This way, MeV heavy ion irradiation can be used to design custom-made NP lattices. In addition, grazing incidence small-angle x-ray scattering can be effectively used as a method for the determination of material redistribution/shift caused by the ion hammering effect. For the first time, the deformation yield in amorphous alumina was determined for irradiation performed at the room temperature.

Effects of MeV heavy ion irradiation on structural, morphological and optical properties of nanostructured SnO2 thin films prepared by thermal evaporation

We report on the effects of 8 MeV Si3+ ion irradiation on the structural, morphological and optical properties of nanostructured SnO2 thin films, prepared by a simple thermal evaporation method. The structural and morphological evolution of nanostructured SnO2 thin films upon MeV ion irradiation was studied by X-ray diffraction (XRD) and atomic force microscopy (AFM), while the optical properties of the thin films were characterized by Raman spectroscopy and photoluminescence spectroscopy (PL). XRD studies revealed the presence of nanocrystals of orthorhombic SnO2 and cubic Sn in the as-deposited thin films. AFM studies revealed growth of SnO2 nanoparticles in the films upon MeV ion irradiation. PL studies on the 8 MeV Si ion irradiated nanostructured SnO2 thin films revealed strong enhancement in the intensity of UV and visible emissions from SnO2 nanostructures.

Surface modifications of hydrogen storage alloy by heavy ion beams with keV to MeV irradiation energies

This study deals with the effect of surface modifications induced from keV to MeV heavy ion beams on the initial reaction rate of a hydrogen storage alloy (AB5) in electrochemical process. The rare earth based alloys like this sample alloy are widely used as a negative electrode of Ni–MH (Nickel–Metal Hydride) battery. We aimed to improve the initial reaction rate of hydrogen absorption by effective induction of defects such as vacancies, dislocations, micro-cracks or by addition of atoms into the surface region of the metal alloys.Since defective layer near the surface can easily be oxidized, the conductive oxide layer is formed on the sample surface by O+ beams irradiation, and the conductive oxide layer might cause the improvement of initial reaction rate of hydriding. This paper demonstrates an effective surface treatment of heavy ion irradiation, which induces catalytic activities of rare earth oxides in the alloy surface.

Structural damage in InGaN induced by MeV heavy ion irradiation

In0.18Ga0.82N films were irradiated with 4MeV 84Kr and 8.9MeV 209Bi ions to various fluences at room temperature. The irradiated films were analyzed by means of Rutherford backscattering/channeling (RBS/C) and high resolution X-ray diffraction (HRXRD). The RBS/C measurements show that under the irradiation conditions, the relative lattice disorder in the films, obtained from the normalized backscattering yield, exhibits a rapid increase in the range from ∼2% to 68%. There is also an increasing lattice expansion of the films with increasing ion fluence, as determined by the HRXRD measurements. At a comparable level of lattice disorder, the Kr irradiation leads to a more pronounced lattice expansion than the Bi irradiation. This may be attributed to a larger portion of the single interstitials in the films produced by the lighter Kr ion irradiation.

An electrostatic quadrupole doublet focusing system for MeV heavy ions in MeV-SIMS

The importance of imaging mass spectrometry (MS) for visualizing the spatial distribution of molecular species in biological tissues and cells is growing. In conventional SIMS with keV-energy ion beams, elastic collisions occur between projectiles and atoms in constituent molecules. The collisions produce fragments, making acquisition of molecular information difficult. In contrast, MeV-energy ion beams excite electrons near the surface and enhance the ionization of high-mass molecules, hence, fragment suppressed SIMS spectrum of ionized molecules can be obtained. This work is a further step on our previous report on the successful development of a MeV secondary ion mass spectrometry (MeV-SIMS) for biological samples. We have developed an electrostatic quadrupole doublet (EQ doublet) focusing system, made of two separate lenses, Q1 and Q2, to focus the MeV heavy ion beam and reduce measurement time. A primary beam of 6MeV Cu4+ was focused with this EQ doublet. We applied 1120V to the Q1 lens and 1430V to the Q2 lens, and the current density increased by a factor of about 60. Using this arrangement, we obtained an MeV-SIMS image of 100×100pixels of cholesterol-OH+ of cerebellum (m/z=369.3) over a 4mm×4mm field of view, with a pixel size of 40μm within 5min, showing that our EQ doublet reduces the measurement time of current imaging by a factor of about 30.

Ejection of Au and Si nanocrystals from Au implanted Si(1 0 0) by MeV heavy ion irradiation

Si(100) substrates implanted with 32keV Au− ions, were irradiated with 3MeV Au3+ ions at an angle of 60°. Transmission electron microscopy (TEM) studies on sputtered particles collected on catcher grids revealed the presence of Au and Si nanocrystals. The size distribution of collected Au nanocrystals exhibited inverse power law dependence with a decay exponent of 2. Atomic force microscopy (AFM) analysis of irradiated sample showed the presence of surface craters along with hillocks. The formation of Au and Si nanocrystals in MeV ion irradiated Au doped amorphous Si layer can be attributed to the localized melting due to thermal spike phase of atomic displacement cascades produced by MeV Au ion impacts.

An IGISOL portrait

This issue of Hyperfine Interactions consists of 21 articles describing scientific work related to the research at the on-line isotope separator facility IGISOL at the University of Jyvaskyla, Finland. Ten contributions containing a significant amount of original results, earlier unpublished, have been presented as a Topical Collection in the European Physical Journal (EPJA 48 issue No 4, 2012). In the early 1980s, the Ion Guide Isotope Separator On-Line (IGISOL) concept was realized at the 20 MeV proton cyclotron of the Physics Department at the University of Jyvaskyla (JYFL). For the first time, the technique allowed the production of high quality ISOL beams from nuclear reaction products with millisecond delay times without chemical restrictions. By providing access to short-lived isotopes of refractory elements it opened up new regions in the nuclear chart for nuclear decayand ground-state spectroscopy. During the 1980s, the main research activity at IGISOL was decay spectroscopy, and in particular, of fission products produced in proton-induced fission of natural uranium. Approximately 40 new isotopes and isomers were discovered and studied employing beta-, gamma-, and conversion electron spectroscopy. These experiments covered a broad range of neutron-rich nuclei from yttrium (Z = 39) to cadmium (Z = 48) and revealed how their structure was developing between highly deformed zirconium through triaxial ruthenium isotopes to weakly deformed vibrational cadmium isotopes. The original IGISOL facility was shut down in October 1991 and was reinstalled as IGISOL-2 at the science campus housing the laboratory for the K = 130 MeV heavy ion cyclotron. A new window of opportunity for extending research to neutrondeficient nuclei far from stability was opened and was going to have a strong impact

Relaxation of surface tracks on polycarbonate thin films induced by MeV heavy-ion impacts

In the present work, the relaxation behavior of nanometer-sized deformations produced by single ion impacts on the surface of monodisperse ( M w = 60,000 u) polycarbonate thin films was investigated at temperatures close to and below the glass transition. The relaxation functions for the length, height and width of the deformations were well described by a stretched exponential law, with characteristic relaxation times τ strongly dependent on temperature. For T > 100 °C, the temperature dependence of τ obeys a Vogel–Fulcher law, but for lower temperatures it becomes less steep and tends to an Arrhenius-type behavior.

Potential Measurement with the 6-MeV Heavy Ion Beam Probe of LHD

The potential in the plasma core of the Large Helical Device (LHD) was measured with the 6 MeV Heavy Ion Beam Probe (HIBP). The radial profile of the potential in the region where the normalized minor radius, ρ, is less than 0.5 was measured and the electric field obtained from the fitting function of the experimental data was compared with that calculated from neoclassical ambipolarity. The experimental results coincide well with the theoretical calculations. Negative pulses were observed in the potential signal in the inward shifted magnetic configuration. The time constants of these pulses were less than the energy confinement time. Potential fluctuations of the coherent modes were also observed, and one of their frequencies coincided with the geodesic acoustic mode (GAM). In this report, the present status of potential measurements with the HIBP system in LHD is described. c

Applications of Heavy Ion Irradiation in Photonic CrystalResearch

Photonic crystals (PC) have received extensive attention for the photonic band gap (PBG). The polystyrene (PS) particles bottom-up approach is a productive method for photonic crystal manufacture, this kind of photonic crystals having an unique PBG that depends on the particle's shape, sizes and defects. Heavy ion irradiation is a very useful method to induce defects in PC and change the shapes of the particles to tune the PBG. MeV heavy ion irradiation leads to an anisotropic deformation of the particles from spherical to ellipsoidal, the aspect ratio of which can be precisely controlled by using the ion energy and flux. Sub-micrometer PS particles were deposited on a Cu substrate and were irradiated at 230 K by using heavy ion energy and fluence in the range from 2 to 10 MeV and 1 x 10(14) cm(-2) to 1 x 10(15) cm(-2); respectively.

English

Studies on MeV heavy ion beam-induced epitaxial crystallisation of a buried silicon nitride layer are reported. Transmission electron micrographs and selected area diffraction patterns have been used to study the recrystallisation of an ion beam-synthesised layer. Complete recrystallisation of the silicon nitride layer having good quality interfaces with the top- and the substrate-Si has been obsorved. Recrystallisation is achieved at significantly lower temperatures of 100 and 200OC for oxygen and silver ions, respectively. The fact that recrystallisation is achieved at the lowest temperature for the oxygen ions is discussed on the basis of energy loss processes.Defence Science Journal, 2009, 59(4), pp.351-355, DOI:http://dx.doi.org/10.14429/dsj.59.1533

Radiation Effects in InGaAs and Microbolometer Infrared Sensor Arrays for Space Applications

Cobalt60, 60 MeV proton and heavy ion tests have been performed on InGaAs and amorphous silicon microbolometer arrays with CMOS readout circuits. The readout circuits showed latch-up at threshold LETs~14 MeV/mg/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , but the total dose and displacement damage effects were negligible for low earth orbit conditions. Effects in a microbolometer array tested, for use in Mercury orbit, to 100 krd(Si) and 3.2 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> 60 MeV p/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> showed acceptable performance, though there was a significant increase in power consumption for the CMOS readout circuit when biased during cobalt60 irradiation.

Characterization of swift heavy ion‐induced defects in Fe‐Rh alloy by using positron beam technique

AbstractRecently, we have found that 100–200 MeV heavy ion irradiation induces ferromagnetic state in B2 type Fe‐50at.%Rh intermetallic alloy below antiferromagnetic‐ferromagnetic transition temperature of unirradiated alloy. In order to characterize the lattice defects induced by swift heavy ion irradiation, we performed Doppler‐broadening experiments for unirradiated Fe‐Rh alloy and that irradiated with 200 MeV 136Xe ions by using a slow positron beam. The S‐parameter increases gradually with increasing the ion‐fluence up to 5 x 1012 ions.cm–2. Above 5 x 1012 ions.cm–2, the rate of S‐parameter increase is slowly saturated. From the dependence of S‐parameter on ion‐fluence, we have calculated the concentration of vacancy‐type defects surviving in the specimen, which is much smaller than that estimated by TRIM‐code. The result implies that anti‐site type defects dominantly remain in the irradiated specimen, which stabilize the ferromagnetic state in Fe‐50at.%Rh alloy. (© 2007 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Formation of nanometer-scale structures in SiO2 thin films by means of MeV-ion irradiation

Future nanometer-scale electronic applications will require the engineering and modification of new materials on the atomic and molecular scale. In this article, we explore the possibility of using MeV heavy-ion irradiation to induce physical modifications on the materials of choice of the existing microelectronic technology, such as SiO2, metals and silicon, to form nanometer-scale structures. Micrometer-sized trenches or H-shaped structures were machined using focused ion-beam milling in Al/SiO2 and Au/SiO2 bilayers on crystalline Si. These samples were irradiated with a 4.6 MeV O2+ beam at room temperature, and the structures were studied by scanning electron microscopy. The micrometer-scale SiO2 structures underwent an anisotropic deformation induced by the electronic energy loss of the MeV incoming ions, leading to a major flow of SiO2 which fills the trench region. The target dimensions perpendicular to the beam direction increased, and the trench width or the micrometer-sized gaps of these structures decreased down to the nanometer scale as a function of the ion fluence. In the case of Al/SiO2 and Au/SiO2 bilayers, only the SiO2 film underwent the plastic deformation, and there is no flow of either the silicon substrate or the metallic layer.