Microstructural evolution in metals during helium and proton irradiations

Abstract

Recent investigations of helium-implanted and proton irradiated metals at medium temperatures (T≤100°C) have demonstrated the importance of high energy cascade effects for the microstructural evolution. They can effect the formation and the evolution of He densities in small bubbles formed by He implantation and are important also for the formation of periodic walls of defect clusters, a phenomenon observed under proton irradiations. Experimental results obtained by transmission electron microscopy and differential dilatometry for MeV irradiations of Cu and Ni are summarized and compared with observations after heavy-ion and neutron irradiations.     

Electron induced modification in poly(ethylene terephthalate)

Abstract

The effect of 100 kGy dose of 2 MeV electron irradiation on Poly(ethylene terepthalate) (PET) has been studied by different characterisation techniques such as the Fourier transformed IR spectroscopy, electron spin resonance spectroscopy, thermogravimetric analysis, differential scanning calorimetry and X-ray diffraction analysis. Oxidative degradation leading to amorphisation of the polymer has been observed from spectral analysis. The thermal stability of the polymer was found to decrease due to electron irradiation. The thermal decomposition temperature as well as the melting temperature in case of irradiated PET was found to be decreased due to electron bombardment. A decrease in crystallinity of the polymer has also been observed after irradiation.     

Comparative study on low energy ion beam modification of thermoplastic polymers

ABSTRACT

Polycarbonate (PC) and polyethylene terephthalate (PET) thermoplastic polymer films were irradiated by low energy ion beams such as 100 keV Hydrogen (H⁺) ions and 350 keV Nitrogen (N⁺) ions at varied fluence from 1?×?10¹³ ions/cm² to 5?×?10¹⁴ ions/cm². The depth profile concentration of ions was calculated using Stopping and Range of Ions in Matter (SRIM) software code. Fourier Transform Infrared (FTIR) technique shows decrement in the intensity of peaks and disappearance of peaks mainly related to carbonyl stretching at 1770?cm^?1 and C–C stretching at 1500?cm^?1. Scanning electron microscopy (SEM) of irradiated polymers showed the formation of pores. X-ray diffraction (XRD) analysis has showed decrease in the intensity indicating the decrease in crystallinity after irradiation. Mechanical studies revealed that the molecular weight and microhardness decrease with increase in ion fluence due to increase in chain scission. The contact angle increased with increase in ion fluence indicating the hydrophobic nature of polymer after irradiation. Antibiofilm activity test of irradiated films shows resistance to Salmonella typhi (S. typhi) pathogen responsible for typhoid. The study shows that Nitrogen ion induces more damage compared to Hydrogen ions and PC films get more modified than PET films.     

Effect of proton irradiation on the physical properties of PC/PBT blends

Samples from polycarbonate/poly (butylene terephthalate) (PC/PBT) blends film have been irradiated using different fluences (1?×?10¹⁵– 5?×?10¹⁷ H⁺/cm²) of 1?MeV protons at the University of Surrey Ion Beam Center, UK. The structural modi?cations in the proton irradiated samples have been studied as a function of fluence using different characterization techniques such as X-ray diffraction and UV spectroscopy. The results indicate that the proton irradiation reduces the optical energy gap that could be attributed to the increase in structural disorder of the irradiated samples due to crosslinking. Furthermore, the color intensity ΔE, which is the color difference between the non-irradiated sample and those irradiated with different proton fluences, increased with increasing the proton fluence up to 5?×?10¹⁷ H^+/cm², convoyed by an increase in the red and yellow color components. In addition, the resultant effect of proton irradiation on the thermal properties of the PC/PBT samples has been investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). It is found that the PC/PBT decomposes in one weight loss stage. Also, the variation of transition temperatures with proton fluence has been determined using DSC. The PC/PBT thermograms were characterized by the appearance of two endothermic peaks due to the glass transition and melting temperatures. The melting temperature of the polymer, T_m, was investigated to probe the crystalline domains of the polymer, since the proton irradiation destroys the crystalline structure so reducing the melting temperature.     

Feasibility of high power refractory metal-foil targets for EURISOL

EURISOL foil-targets have to withstand a primary proton beam of 1 GeV kinetic energy and up to 100 μA beam current. These foil targets will be based on previous high-power target concepts, i.e. the RIST target [J.R.J. Bennett et al., Nucl. Instrum. Meth. Phys. Res. B 126, 117 (1997)] or high power targets used at TRIUMF [P. Bricault et al., Nucl. Instrum. Meth. Phys. Res. B 204, 319 (2003), M. Dombsky et al., Nucl. Instrum. Meth. Phys. Res. B 204, 191 (2003)]. A single target unit is capable of dissipating up to 25 kW, hence, several target units can be merged together by individual transfer lines to one common ion source. The single target units will be irradiated by a proton beam in a time sharing mode to distribute the primary proton beam current to the individual target units. In this feasibility study the necessary properties of high-power foil targets are discussed and the requirements to design a foil target according to the proton beam parameters [CITE] for the future EURISOL facility are given.     

Surface and Bulk Structure Characterization of Proton (3 MeV) Irradiated Polycarbonate

Polycarbonate (Makrofol‐N) thin films were irradiated with protons (3 MeV) under vacuum at room temperature with the fluence ranging from 1×10¹⁴ to 1×10¹⁵ protons cm^?2. The change in surface morphology, optical properties, degradation of the functional groups, and crystallinity of the proton‐irradiated polymers were investigated with atomic force microscopy (AFM), UV‐VIS, and Fourier‐transform infrared (FTIR) spectroscopy, and X‐ray diffraction (XRD) techniques, respectively. AFM shows that the root mean square (RMS) roughness of the irradiated polycarbonate surface increases with the increment of ion fluence. The UV‐VIS analysis revealed that in Makrofol‐N the optical band gap decreased by 30% at highest fluence of 1×10¹⁵ protons cm^?2. The band gap can be correlated to the number of carbon atoms, M, in a cluster with a modified Robertson's equation. The cluster size in the proton‐irradiated Makrofol‐N increased from 112 to 129 atoms with the increase of fluence from 1×10¹⁴ to 1×10¹⁵ protons cm^?2. FTIR spectra of proton (3 MeV) irradiated Makrofol‐N showed a strong decrease of almost all absorption bands at about 1× 10¹⁴ protons cm^?2. However, beyond a higher critical dose an increase in intensity of almost all characteristic bands was noticed. The appearance of a new peak at 3,500 cm^?1 (‐OH groups) was observed at the higher fluences in the FTIR spectra of proton‐irradiated polycarbonate. XRD measurements showed an increase of full width at half maximum (FWHM) and the average intermolecular spacing of the main peak, which may be due to the increase of chain scission and the introduction of ‐OH groups in the proton irradiated polycarbonate.     

Development of radiation medicine at DLNP, JINR

The Dzhelepov Laboratory of Nuclear Problems’ activity is aimed at developing three directions in radiation medicine: 3D conformal proton therapy, accelerator techniques for proton and carbon treatment of tumors, and new types of detector systems for spectrometric computed tomography (CT) and positron emission tomography (PET). JINR and IBA have developed and constructed the medical proton cyclotron C235-V3. At present, all basic cyclotron systems have been built. We plan to assemble this cyclotron at JINR in 2011 and perform tests with the extracted proton beam in 2012. A superconducting isochronous cyclotron C400 has been designed by the IBA-JINR collaboration. This cyclotron will be used for radiotherapy with proton, helium and carbon ions. The ¹²C⁶⁺ and ⁴He²⁺ ions will be accelerated to an energy of 400 MeV/amu, the protons will be extracted at the energy 265 MeV. The construction of the C400 cyclotron was started in 2010 within the framework of the Archarde project (France). Development of spectrometric CT tomographs may allow one to determine the chemical composition of a substance together with the density, measured using traditional CT. This may advance modern diagnostic methods significantly. JINR develops fundamentally new pixel detector systems for spectrometric CT. The time-of-flight (TOF) system installed in the positron emission tomograph (PET) permits essential reduction in the detector noise from occasional events of different positron annihilations. The micropixel avalanche photodiodes (MAPDs) developed at JINR allow a factor of 1.5 reduction in the resolution time for the PET TOF system and suppression of the noise level as compared to commercial PET. The development of a combined PET/MRI is of considerable medical interest, but it cannot be made with the existing PET tomographs based on detectors of compact photomultipliers due to strong alternating magnetic field of MRI. Change-over to detectors of micropixel avalanche photodiodes permits making a combined PET/MRI.     

Gold nano-wires and nano-layers at laser-induced nano-ripples on PET

Gold nano-layers were deposited onto laser irradiated polyethyleneterephthalate (PET) surfaces. For irradiation, we used the linearly polarized light of a pulsed 248 nm KrF and 157 nm F₂ laser, respectively. In a certain range of irradiation parameters, the irradiation resulted in the formation of coherent ripples patterns with a lateral periodicity in the order of the wavelength of the laser light and with a corrugation height of several 10 nm. The deposited layers were then prepared by sputtering. The layers were analyzed by atomic force microscopy (AFM), focused ion beam (FIB) cuts, scanning electron microscopy (SEM), and angular resolved X-ray induced photoelectron spectroscopy (ARXPS). Gold sputtering on KrF laser irradiated PET led to the formation of separated “nano-wires” at the ridges of the nano-patterns and not to a continuous metal layer, as we obtained in case of gold sputtering onto F₂ irradiated PET. The results of the XPS analysis indicated, that the KrF irradiation caused degradation on the ridge of the ripples, whereas no noticeable degradation occurred for F₂ laser treatment. We attribute the different growth mechanisms of the deposited gold layers mainly to the difference in surface chemical composition of laser irradiated PET with the two different lasers employed.     

Mechanical response of proton beam irradiated nitinol

The present investigation deals with the study of mechanical behavior of proton beam irradiated nitinol at room temperature. The specimens in austenitic phase were irradiated over periods of 15, 30, 45 and 60 min at room temperature using 2 MeV proton beam obtained from Pelletron accelerator. The stress-strain curves of both unirradiated and irradiated specimens were obtained using a universal testing machine at room temperature. The results of the experiment show that an intermediate rhombohedral (R) phase has been introduced between austenite and martensite phase, which resulted in the suppression of direct transformation from austenite to martensite (A-M). Stresses required to start R-phase (σ_RS) and martensitic phase (σ_MS) were observed to decrease with increase in exposure time. The hardness tests of samples before and after irradiation were also carried out using Vickers hardness tester. The comparison reveals that the hardness is higher in irradiated specimens than that of the unirradiated one. The increase in hardness is quite sharp in specimens irradiated for 15 min, which then increases linearly as the exposure time is increased up to 60 min. The generation of R-phase, variations in the transformation stresses σ_RS and σ_MS and increase in hardness of irradiated nitinol may be attributed to lattice disorder and associated changes in crystal structure induced by proton beam irradiation.     

Evolution of vacancy defects in the surface layers of a metal irradiated with a pulsed electron beam

The distribution of vacancy defects in the surface layers of α-Fe after irradiation with a high-current pulsed electron beam is studied experimentally by unique nuclear-physical methods — low-energy positron annihilation, Rutherford backscattering (RBS), and proton-induced x-ray emission (PIXE). Regions with low local density, which are sources of crater formation on the surface of the irradiated sample, are observed by scanning a proton microbeam. Positron lifetime measurements reveal that as the electron beam power increases, nonequilibrium vacancies tend to be captured by carbon impurity atoms. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 8, 618–622 (25 April 1997)     

Laser Desorption Mass Spectrometry of Some Organic Acids

Abstract

Positive and negative ion laser desorption (LD) mass spectra of organic acids are characterized by the emission of the quasimolecular ions (M+H)⁺ and (M-H)^?. Generation of (M+H)⁺ ions is interpreted as evidence for the occurence of high pressure proton transfer reactions in LD. Fragment ions can be rationalized by loss of stable neutral molecules from quasimolecular ions although decomposition may also be occuring prior to ionization. Features unique to LD, including the detection of pyrolysis products along with ions characteristic of the sample, are discussed in terms of the internal energy distribution in the irradiated microvolume. Negative ion mass spectra of acids are dominated by (M-H)^?, while positive ion spectra contain abundant fragment ions, underlining the utility of detecting negative ions for acidic compounds.     

The Anthracen-9-ylmethyloxy Unit: An Underperforming Motif Within the Fluorescent PET (Photoinduced Electron Transfer) Sensing Framework

Compound 2, which was designed to act as a fluorescent sensor for calcium according to the PET (Photoinduced Electron Transfer) principle, shows a relatively small Ca²⁺-induced fluorescence enhancement factor (FE) of 1.8 whereas its close relative 1 is known to display a far higher FE value of 16. Though designed as fluorescent PET sensors for solvent polarity, compounds 5 and 6 also show negligible fluorescence enhancement as their environments are made progressively less polar even though their relatives 3 and 4 show limiting FE values of 53 and 3, respectively. Indeed, 3 and 4 are useful since they are fluorescent sensors for solvent polarity without being affected by Bronsted acidity. The poor sensory performance of 2, 5, and 6 relative to their cousins is attributed to the presence of an oxygen proximal to the 9-position of an anthracene unit, which opens up a CT (charge transfer) channel. Normal PET sensing service is resumed when the offending oxygen is deleted.     

Modification of polyethylene terephthalate by proton irradiation

Polyethylene terephthalate (PET) films were irradiated with 3 MeV proton beams at different fluences. The microhardness, electrical, thermal and structural studies were carried out using microhardness tester, LCR meter, thermogravimetric analysis (TGA) and FTIR spectroscopy. Vickers' hardness has been observed to increase with the fluence. The true bulk hardness of the film was obtained at loads greater than 400 mN. The AC electrical conductivity is practically unaffected by irradiation up to a frequency of 10 kHz, but it is found to increase exponentially at a frequency of 300 kHz. The loss factor and dielectric constant are observed to change appreciably with the fluence. It is observed that there is no significant change in the stability of the polymer up to the fluence of 10¹⁴ ions cm^?2 as revealed by TGA and FTIR spectroscopy.     

The magnetic phase transition in titanium oxide induced by proton irradiation

We have studied the magnetic properties of ⁵⁷Fe-doped TiO₂ compounds irradiated by proton with 0, 5 and 10 pC/μm². We have observed the enhancement of the magnetic moment, measured by superconducting quantum interference device magnetometer, with increasing proton irradiation ranging from 0 to 10 pC/μm². Mössbauer spectra of proton irradiated Ti_0.99⁵⁷Fe_0.01O₂ samples were taken at room temperature. Two sites of the wing (sextet) and the central (doublet) are shown in the spectra, which suggest the magnetically ordered phase and the paramagnetic phase, respectively. With increasing proton irradiation, the part of Fe³⁺ ions was converted to Fe²⁺ ions by compensation charge. This clearly suggests that the enhancement of magnetic moment after proton irradiation is contributed to the moment by the spin-orbit coupling of Fe²⁺ ions.     

Electron inducing soft errors in 28 nm system-on-Chip

ABSTRACT

The 28?nm system-on-chip (SoC) was irradiated by 12?MeV electron at the China Institute of Atomic Energy (CIAE) for the first time. Soft errors in the on-chip memory (OCM), D-Cache, Register and BRAM blocks were investigated. The obtained device cross sections are almost in the range of 10^?13 cm² to 10^?11 cm² for the blocks. The results demonstrate that electron fluence per pulse and the corresponding prompt dose rates have no influence on the soft errors in 28?nm SoC. The discrepancy was analyzed between proton and electron inducing soft errors in D-Cache and BRAM blocks, too. The secondary electron is considered as the dominant reason for soft errors caused by 12?MeV electron in 28?nm SoC.     

Phase transformation studies in unirradiated and proton beam irradiated Ni–Ti alloy between 25 and 100°C

The stress-induced phase transformation characteristics of unirradiated and proton beam irradiated NiTi alloy were investigated at different tests temperatures. The wire-shaped NiTi specimens were irradiated by 2?MeV proton beam for 30?min at room temperature to a flux of 10¹⁹ protons/m² s. Engineering stress–strain (S-S) curves of both unirradiated and irradiated specimens were obtained using a materials testing machine at 25, 50, 75 and 100°C. The results indicate a single-stage phase transformation from austenite to martensite (B2–B19′) in unirraidated specimens at all the test temperatures. In contrast, in the case of the irradiated specimens, a two-stage austenite–rhombohedral–martensite (B2–R–B19′) phase transformation is observed at 25 and 50°C. The B2–R–B19′ phase transformation, however, is found to change into B2–B19′ transformation at 75 and 100°C. The stress required to initiate the B19′ phase transformation (σ_MS) and the plateau range are found to be lower in irradiated specimens compared with those of the unirradiated specimens. The results obtained are discussed on the basis of the formation of Ni₄Ti₃ precipitates in irradiated specimens and their consequences on the phase transformations.     

Evidence of the primary-color photoluminescence in ion (H,H,C) irradiated and thermal annealed SrTiO3

We have measured photoluminescence (PL) spectrum of (1) thermal-annealed SrTiO₃/Si thin film and undoped SrTiO₃ single crystal; (2) SrTiO₃ single crystal irradiated by high energy (3 MeV) proton, deuterium, and He ion beams and (3) SrTiO₃ single crystal irradiated by low energy (60 keV) H⁺ and C⁻ ions. Two PL emissions are induced in (1) and (2) at visible frequencies 3 and 2.45 eV, while another PL peak is induced at 2 eV in (3). When compared with our previous PL experiments on high-temperature annealed SrTiO₃/SiO₂/Si thin film and 3 MeV proton (H⁺) irradiated STO single crystal, these results confirm that the three PL emissions with blue (3 eV), green (2.45 eV), and red-orange (2 eV) frequencies originate indeed from SrTiO₃. These primary-color PL effect induced at room-temperature makes STO a strong candidate material for future oxide-based optoelectronic application.     

1H NMR Spectral Simplification with Achiral and Chiral Lanthanide Shift Reagents. Mexiletine

The 60 MHz ¹H NMR spectra of mexiletine, 1-(2,6-dimethylphenoxy)-2-propanamine, 1, have been studied at 28° in CDCl₃ solution with the achiral reagent, tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato) europium(III), 2, Eu(FOD)₃, and the chiral reagents tris[3-(trifluoromethylhydroxymethylene)-d-camphorato]europium(III), 3, Eu(FACAM)₃, and tris[3-(heptafluoropropylhydroxymethylene)-d-camphorato]europium(III), 4, Eu(HFC)₃. Substantial lanthanide-induced shifts were seen for the proton signals of 1 with each reagent. Appreciable enantiomeric shift differences were seen for both methyl signals and for each of the CH₂CH proton signals using 3 and 4 that should permit direct determinations of enantiomeric excess for samples of 1. A predominant conformation for 1 is suggested based on observed splittings of the CH₂ proton signals and their relative lanthanide-induced shifts.     

Lattice damage and Al-metal precipitation in 2.5 MeV-electron-irradiated AlH3

AlH₃ powder was bombarded with energetic electrons at 20 K and at room temperature and investigated by EPR, NMR, X-ray diffractometry, and microwave dielectric-constant measurements. The EPR spectra of the irradiated powder and of a selected single crystal cuboid of mm edge show a complex asymmetric line centered at g = 2.009, with a Curie-like temperature dependence, attributed to radiation-induced color centers and/or their agglomerates. At the same time, the grains, which have become shiny black after irradiation, exhibit an increase of both the real and the imaginary part of . ²⁷Al-NMR spectra of the irradiated powder present a Knight-shifted line at 1600(50) ppm, close to the position of bulk metallic Al, and corresponding to a concentration of c(Al) . In addition, the main hydride line differs from that before irradiation, demonstrating an alteration of environmental symmetry. The irradiation induces also a change in shape and width of the ¹H-NMR line, another indication of symmetry change in the lattice. Finally, a refined X-ray single-crystal structure analysis of the irradiated cuboid indicates a change of structure from trigonal R -3 c to R -3, with a loss of mirror symmetry for the two Al sites caused by the introduction of Al-defects in the vicinity of one of them. Received: 20 October 1997 / Revised: 24 December 1997 / Accepted: 30 January 1998