I. Rajta

I. Rajta
Institute for Nuclear Research, Hungarian Academy of Sciences · Section of Applications of Nuclear Physics

PhD

About

116
Publications
7,737
Reads
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1,395
Citations
Introduction
Additional affiliations
January 2012 - present
University of Debrecen
Position
  • Lecturer in "Ion Beams in Materials Science"
January 2001 - December 2001
National University of Singapore
Position
  • PostDoc Position
January 2000 - December 2000
University of Oxford
Position
  • PostDoc Position

Publications

Publications (116)
Preprint
Full-text available
Employing the $^{11}$B(p,$\gamma$)$^{12}$C nuclear reaction, the angular correlation of $e^+e^-$ pairs was investigated in the angular range of $40^\circ\Theta\leq 175^\circ$ for five different proton energies between E$_p$ = 1.5 - 2.5 MeV. At small angles ($\Theta\leq 120^\circ$), the results can be well interpreted by the internal pair creation p...
Preprint
Full-text available
Angular correlation spectra of $e^+e^-$ pairs produced in the $^{7}$Li($p$,$\gamma$)$^{8}$Be nuclear reaction have been studied at the sharp $E_p$= 441 keV resonance as well as at $E_p$= 650 keV, 800 keV and 1100 keV proton beam energies. The spectra measured at the resonance can be understood through the M1 internal pair creation process, but in t...
Article
High-energy low-mass proton implantation achieved considerable interest in semiconductor technology, due to much deeper penetration of hydrogen ions into silicon as compared to common dopants, boron, phosphorous, and arsenic. Accordingly, monitoring the accumulation kinetics and stability of proton-implantation induced defects and their influence o...
Article
Full-text available
Angular correlation spectra of e+e− pairs produced in the H3(p,e+e−)He4 nuclear reaction have been studied at Ep=510, 610, and 900 keV proton energies. The main features of the spectra can be understood by taking into account the internal and external pair creations following the proton capture by H3. However, these processes cannot account for an...
Preprint
We present computer simulations about the spatial and temporal evolution of a 1-MeV proton microbeam transmitted through an insulating macrocapillary with the length of 45 mm and with the inner diameter of 800 {\mu}m. The axis of the capillary was tilted to 1{\deg} relative to the axis of the incident beam, which ensured geometrical nontransparency...
Preprint
Energy-sum and angular correlation spectra of $e^+e^-$ pairs produced in the $^{3}$H(p,$\gamma$)$^{4}$He nuclear reaction have been studied at $E_p$=510, 610 and 900 keV proton energies. The main features of the spectra can be understood by taking into account the internal and external pair creations following the direct proton radiative capture by...
Article
Full-text available
We present computer simulations about the spatial and temporal evolution of a 1-MeV proton microbeam transmitted through an insulating macrocapillary with the length of 45 mm and with the inner diameter of 800 μm. The axis of the capillary was tilted to 1° relative to the axis of the incident beam, which ensured geometrical nontransparency. The sim...
Article
Full-text available
Proton irradiation induced radiolysis of methyl orange was investigated in aqueous solution with an in-air ion beam setup. 566–3024 keV energy protons were used for the irradiations of 1.6 mM aqueous methyl orange solutions, in the presence and absence of tert-butanol radical scavenger. The decoloration of methyl orange was followed by UV/vis spect...
Article
Full-text available
In this paper, the Atomki Accelerator Centre (AAC, Debrecen, Hungary) incorporating several small-sized particle accelerators is reviewed. The energy range of our accelerators for proton beam is between 50 eV and 20 MeV. The technical and personnel organization of AAC is presented together with the rules of beamtime requests and usage. Three of our...
Article
Full-text available
In this work resonance parameters of the ²⁸Si(p,p′γ)²⁸Si (Eγ = 1779 keV) and ¹⁴N(p,p′γ)¹⁴N (Eγ = 2313 keV) reactions were measured between 3 and 4 MeV proton energies for absolute proton beam energy calibration of particle accelerators. For the measurements commercially available self-supporting thin silicon–nitride films and a HPGe gamma-detector...
Conference Paper
Planar optical waveguides were designed and fabricated in an Er-doped Tungsten-Tellurite oxide glass and in a KDy (WO4)2 crystal by swift heavy ion irradiation. 12.5 MeV Au⁵⁺ ions were used in the first case and 10.5 MeV N⁴⁺ ions in the second one. Irradiated fluences were very low: 7·10¹⁴ ions/cm² in the first experiment, and 4·10¹⁵ ions/cm² ions/...
Article
Experimental observation of the dynamics of a micro-focused, 1 MeV proton beam guided through a single, insulating macrocapillary is presented. The micrometer sized proton beam was center injected into a poly(tetrafluoroethylene) capillary with macroscopic dimensions. The capillary was tilted to 1° with respect to the beam, i.e. no geometrical tran...
Article
We present theoretical investigation of the temporal evolution of the energy spectrum of ions passing through an insulating capillary. In our simulation we used 1 MeV proton microbeam, and a single, cylindrical shaped polytetrafluoroethylene (PTFE) macrocapillary. In order to prevent the simple geometrical transmission the beam axis was tilted with...
Article
Full-text available
Channel waveguides were directly written in Er: TeO2W2O3 glass using 11 MeV C4+ ion microbeam with fluences in the range of 1·1014–5·1016 ion/cm2. The channel waveguides supported a single guided mode at λ = 1540 nm. Propagation losses of the as-irradiated channel waveguides were around 14 dB/cm. A 30-min thermal annealing at 150 °C in air reduced...
Article
Full-text available
As (Ge)–S (Se) based amorphous bulk chalcogenide glasses and layers have been used for surface geometrical relief recording by 2 MeV energy H⁺ and He⁺ ion-beams. The formation of giant (height modulation from nanometers up to micrometers) geometrical reliefs (dots, lines), have been investigated. Efficiency of surface patterning was compared for se...
Article
The changes of the surface morphology of poly(tetrafluoroethylene)due to proton irradiation was investigated. 1 MeV proton beam was used for the irradiations with relatively low current densities, in the range of 10–100,000 pA/mm ² . The applied ion fluences ranged from 0.1 to 2500 nC/mm ² (6.24 * 10 ¹⁰ –1.56 * 10 ¹⁵ ion/cm ² ). The surface was cha...
Article
In this work we report about the layout, assembly and the first resolution tests of the nuclear nanoprobe at MTA Atomki, Debrecen, Hungary. The nanoprobe setup was installed on the recently inaugurated 2 MV Tandetron accelerator manufactured by High Voltage Engineering Europa B.V. (HVEE). Although the complete Tandetron Laboratory was planned at th...
Article
In this work commercially available self-supporting thin silicon-nitride films were applied to measure the differential cross sections for the reactions ²⁸Si(p,p′γ)²⁸Si (Eγ = 1779 keV) and ¹⁴N(p,p′γ)¹⁴N (Eγ = 2313 keV) in the proton energy range of 3–4 MeV. For an additional validation of the data, the cross section from the present work and from t...
Article
On a roundtrip to Mars, astronauts are expectedly exposed to an approximate amount of radiation that exceeds the lifetime limits on Earth. This elevated radiation dose is mainly due to Galactic Cosmic Rays (GCR) and Solar Particle Events (SPE). Specific patterns of the N‐glycosylation of human immunoglobulins have already been associated with vario...
Article
In this work we present the 2 MV Tandetron accelerator manufactured by High Voltage Engineering Europa (HVEE), that was installed at MTA Atomki in Debrecen, Hungary in 2015. Furthermore, we report on the first performance test of the whole facility including the calibration of the terminal voltage using accurately known resonance energies of the ²⁷...
Article
Full-text available
The CNO cycles are fusion processes in stars that convert hydrogen to helium. These hydrogen burning processes occur in several sites and stages of stellar evolution, such as red giants, asymptotic giant branch (AGB) stars, massive stars, and classical novae. One of the important reactions in the CNO-III and CNO-IV cycles is ¹⁷O(p,γ)¹⁸F [1]. The on...
Article
Among the many applications of chalcogenide glasses, their involvement as an active layer in redox-conductive-bridge-memory (CBRAM) devices triggers particular interest because of their potential to replace CMOS-based NAND and flash memory. In these devices the chalcogenide glass film is in contact with a silver film, and it is of a practical inter...
Article
As a continuation of our previously published work, this paper presents a detailed evaluation of a microfabricated cell capture device utilizing a doubly tilted micropillar array. The device was fabricated using a novel hybrid technology based on the combination of proton beam writing and conventional lithography techniques. Tilted pillars offer un...
Article
Full-text available
In this work the change in the surface topography of polydimethylsiloxane (PDMS) due to irradiation with 10.5 MeV N4 + ion microbeam is investigated. Parallel stripes with different widths and different gaps between the stripes were irradiated. The heavy ion beam induced physical and chemical processes caused shrinkage of the irradiated structures....
Article
Purpose: Rare interchange haplotypes in exon 3 of the OPN1LW and OPN1MW opsin genes cause X-linked myopia, color vision defect, and cone dysfunction. The severity of the disease varies on a broad scale from nonsyndromic high myopia to blue cone monochromatism. Here, we describe a new genotype-phenotype correlation attributed to rare exon 3 interch...
Article
The 17O(p,g)18F reaction plays an important role in hydrogen burning processes in different stages of stellar evolution. The rate of this reaction must therefore be known with high accuracy in order to provide the necessary input for astrophysical models. The cross section of 17O(p,g)18F is characterized by a complicated resonance structure at low...
Article
Among different configurations of lens systems for nuclear microprobes, the most common one is a triplet of magnetic quadrupole lenses. Nowadays, microanalysis and material modification will undoubtedly benefit from an improvement in spatial resolution. This work presents the results of simulations for improvement of the Oxford Triplet lens system...
Article
We present a classical trajectory Monte Carlo simulation of the transmission of 1 MeV H⁺ microbeam through an insulating macrocapillary. The focused proton beam was launched from the capillary entrance under 1° angle of incidence with respect to the capillary axis. The beam first hit the inner surface of the capillary and the protons were either im...
Conference Paper
Full-text available
Active and passive optical waveguides are fundamental elements in modern telecommunications systems. A great number of optical crystals and glasses were identified and are used as good optoelectronic materials. However, fabrication of waveguides in some of those materials remains still a challenging task due to their susceptibility to mechanical or...
Article
Design, fabrication, integration and feasibility test results of a novel microfluidic cell capture device is presented, exploiting the advantages of proton beam writing to make lithographic irradiations under multiple target tilting angles and UV lithography to easily reproduce large area structures. A cell capture device is demonstrated with a uni...
Article
Full-text available
The guiding of 1 MeV proton microbeam passing through a tapered-shape macroscopic insulator capillary was investigated. The intensity of the transmitted beam and the energy distribution of the transmitted particles were measured. We found that significant fraction of the beam can pass through the capillary without any significant energy loss indica...
Article
The ion guiding phenomenon was studied in the case of a single, straight, micrometer sized insulator capillary using a micro focused 1 MeV proton beam. The axis of the incident ion beam was tilted to 1° relative to the axis of the capillary. The aspect ratio of the target and the small beam divergence ensured the geometrical non-transparency of the...
Article
The transmission of 1 MeV proton microbeam passing between two parallel flat plates was investigated. Three different materials were used in our experiments. As insulators we used Polytetrafluoroethylene and borosilicate glass plates and glass with gold layer on the surface as conductor. The surface of the plates was parallel to the beam axis and o...
Article
Full-text available
We present the design and construction of our experimental setup for studying the transmission of proton microbeam through a single, cylindrical shape, macroscopic insulating capillary. The intensity as a function of time, the energy distribution as a function of the transmission and the deflection of the transmitted particles can be measured with...
Article
Full-text available
The transmission of 1MeV proton microbeam through aTeflon microcapillary was studied. Using the suitable combination of the capillary temperature and beam intensity we identified three different regions in the transmission as a function of time. In the third region stable guided transmission was obtained where the dominant contribution of the trans...
Article
Full-text available
The transmission of 1 MeV proton microbeam passing through between two parallel flat plates was investigated. During the measurements the surface of the plates was parallel to the beam axis. The energy and deflection of the beam were measured as a function of the sample position relative to the beam axis. We found significant differences in the pro...
Article
Full-text available
Nowadays, in the modern optical communications systems, channel waveguides represent the core of many active and passive integrated devices, such as amplifiers, lasers, couplers and splitters. Different materials and fabrication processes were investigated in order to achieve the aforementioned optoelectronic circuits with low costs and high perfor...
Article
Full-text available
Charged particles in front of surfaces always accelerate towards the surface due to the attractive image force between the charge and the surface. It is shown that using capillary transmission by charged particle projectiles the image acceleration can be clearly studied without close collision with the inner surface. We present experimental studies...
Article
In this work the refractive index depth profile, its relaxation and the absorption were investigated in 2 MeV proton irradiated PDMS. The above parameters were determined by the spectroscopic ellipsometry technique. The refractive index depth profile follows roughly the shape of the Bragg curve for the penetrating protons. It is shown that the obse...
Article
In this work we determined depth profiles of the chemical change in PMMA irradiated with 2 MeV protons by infrared spectroscopic and micro-Raman measurements. The measurements were carried out on 10 mu m thin stacked foil samples using an infrared spectrometer in universal attenuated total reflectance (UATR) and transmission modes; while the thick...
Article
In this work the creation of convex microlenses is presented in polydimethylsiloxane using shrinkage of the polymer due to energetic ions. The creation process is based on the observation that the PDMS shrinks due to irradiation and the surface of the unirradiated areas will have a regular curvature between the irradiated places. The created microl...
Article
This work is about the detailed investigation of the changes of the surface topography, the degree of compaction/shrinkage and its relation to the irradiation fluence and the structure spacing in poly(dimethylsiloxane) (PDMS) patterned with 2 MeV proton microbeam. The irradiated periodic structures consisted of parallel lines with different widths...
Article
Full-text available
Mechanical degradation of mobile silicon components of complex MEMS reduces device reliability and operation time. Although the considerable wear of the surface micromachined poly-crystalline elements can be decreased by substitution of crystalline-silicon-based equivalent, there is still room for further improvement in device durability. The demon...
Article
Full-text available
In this paper a study on the ion transmission ratio of a nanoporous alumina sample is presented. The sample was investigated by scanning transmission ion microscopy (STIM) with different beam sizes. The hexagonally close-packed Al(2)O(3) nanocapillary array, realized as a suspended membrane of 15 microm thickness, had pore diameters of approximatel...
Article
Full-text available
As a new alternative micromachining method to deep reactive ion etching (DRIE), the combination of proton beam writing (PBW) and porous silicon (PS) etching has proved to be a feasible technique to form crystalline silicon microstructures characterized by high aspect ratio and vertical sidewalls. However, the proposed use of the combined technology...
Article
Optical diffraction grating and micro Fresnel zone plate type structures were fabricated in relatively thin poly(dimethylsiloxane) (PDMS) layers using proton beam writing technique and the performance of these optical devices was tested. PDMS is a commonly used silicon-based organic polymer, optically clear, generally considered to be inert, non-to...
Article
In this paper poly-(dimethylsiloxane) (PDMS) is introduced as a resist material for proton beam writing. We were looking for a biocompatible micropatternable polymer in which the chemical structure changes significantly due to proton beam exposure making the polymer suitable for proton beam writing.Up to now PDMS has been used as a casting or repli...
Article
A 3D Si micro-turbine characterized by high aspect ratio vertical walls was formed by the combination of proton beam writing (PBW) and subsequent selective porous Si (PS) etching. Crystal damages generated by the implanted protons result in increased resistivity, thereby limit or even prevent the current to flow through the implanted area during el...
Article
Microreactors are innovative and promising tools in technology nowadays because of their advantages compared to the conventional-scale reactors. These advantages include vast improvements in surface to volume ratio, energy efficiency, reaction speed and yield and increased control of reaction conditions, to name a few examples. The high resolution...
Article
Full-text available
A variety of different photo resists are used for the fabrication of polymer and metal high aspect ratio structures. Among them SU-8, a chemically amplified negative tone photoresist is the mostly used. However, after processing the finished resist pattern (SU-8) is hardly removed from the substrate. In the present work the formulation and process...