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A number of studies have suggested that the irradiation behavior and damage processes occurring during sequential and simultaneous particle irradiations can significantly differ. Currently, there is no definite answer as to why and when such differences are seen. Additionally, the conventional multi-particle irradiation facilities cannot correctly reproduce the complex irradiation scenarios experienced in a number of environments like space and nuclear reactors. Therefore, a better understanding of multi-particle irradiation problems and possible alternatives are needed. This study shows ionization induced thermal spike and defect recovery during sequential and simultaneous ion irradiation of amorphous silica. The simultaneous irradiation scenario is shown to be equivalent to multiple small sequential irradiation scenarios containing latent damage formation and recovery mechanisms. The results highlight the absence of any new damage mechanism and time-space correlation between various damage events during simultaneous irradiation of amorphous silica. This offers a new and convenient way to simulate and understand complex multi-particle irradiation problems.

Simple and complex borosilicate glasses were irradiated with single and double ion beams of light and heavy ions over a broad fluence and stopping power range. As a result of the heavy ion irradiation (U, Kr, Au), the hardness was observed to diminish and saturate after a decrease by 35 ± 1%. Unlike slow and swift heavy ion irradiation, irradiation with light ions (He,O) induced a saturation hardness decrease of 18 ± 1% only. During double ion beam irradiation; where glasses were first irradiated with a heavy ion (gold) and then by a light ion (helium), the light ion irradiation induced partial damage recovery. As a consequence of the recovery effect, the hardness of the pre-irradiated glasses increased by 10–15% depending on the chemical composition. These results highlight that the nuclear energy loss and high electronic energy loss (≥4 keV/nm) result in significant and similar modifications whereas light ions with low electronic energy loss (≤1 keV/nm) result in only mild damage formation in virgin glasses and recovery in highly pre-damaged glasses. These results are important to understand the damage formation and recovery in actinide bearing minerals and in glasses subjected to self-irradiation by alpha decays. Keywords

A three oxide sodium borosilicate (BS3) and a complex, thirty oxide borosilicate glass (SON68) were irradiated with 2.3 MeV electrons to doses ranging from 0.15 GGy to 4.6 GGy at 350 K. The irradiated glasses were characterized using Raman and NMR spectroscopies, ToF-SIMS, AFM and microhardness to understand surface and bulk irradiation effects. Glass surfaces were observed to be depleted of the alkali atoms. The depletion depth depended on the dose and glass composition, reaching 660 nm and 500 nm on any vacuum facing surface for BS3 and SON68 at 4.6 GGy respectively. The alkali-depleted region was enriched in molecular oxygen and showed characteristics of phase separated glasses. In the bulk of the glass, Raman and NMR spectroscopies showed a silica network depolymerisation, a transformation of 4 to 3-coordinated boron and formation of non-bridging oxygen atoms on silicon and boron atoms. The hardness of the depolymerized glasses decreased by 20% (BS3) and 10% (SON68). Based on the experiments and theory, it is shown that electron stimulated desorption is the dominant surface depletion mechanism. These results show that the surfaces behave differently than the bulk of the glass. Therefore, surface related phenomena are expected to be dominant in TEM and other in-situ and ex-situ surface characterizations having depth resolution of a few hundred nanometers. Thus, sample size plays an important role in evaluating the radiation damage and one must be careful in extending the conclusions drawn from surface sensitive techniques to bulk irradiation effects in electron irradiated glasses.

Transmission electron microscopy (TEM) characterizations were carried out on a set of UO2 thin foils previously implanted at room temperature with 400 keV Xe2+ and 250 keV Kr2+ ions at the fluence 7.1015 at.cm-2 (equivalent to 1 at.%/at. UO2). The experiment was devoted to the study of the evolution of the fission gases bubbles populations with increasing temperature. Annealings were performed in the laboratory furnace at 600°C, 800°C, 1000°C for 12h, 1400°C for 4h and 1500°C for 2h under Ar-5%H2 atmosphere. For each annealing condition and for as-implanted specimens the bubble population has been characterized in size and number density. A comparison between Xe and Kr has been done that showed a similar behaviour. Globally, from the as-implanted sample to the 1500°C annealed, the bubbles growth phenomenon and the microstructure evolution with temperature was put in relieve.

This article reports the determination of the OH radiolytic yields in water irradiated by high energy C 6+ and Ar 18+ ions with LET values of 32 ± 2 and 280 ± 10 eV nm −1 . The time evolution of the yields between 9 × 10 −11 and 9 × 10 −8 s was deduced using the scavenging method with SCN − and Br − and pulse radiolysis with pulses of 5 and 10 μs. The thiocyanate chemical system is less affected with the local high dose rates specific to the high LET particles than the bromide system. At 32 eV nm −1 with C 6+ ions, G (OH ) reaches a maximum of 1.5 × 10 −7 mol J −1 at 1 ns and decreases at earlier times. With Ar 18+ ions of 280 eV nm −1 G (OH ) is always increasing at early times up to 1.6 × 10 −7 mol J −1 at 9 × 10 −11 s. In this case the evolution of the hydroxyl radical yields agrees with the high local concentrations obtained with Ar 18+ and C 6+ ions and depicted in recent literature with the yields of the hydrated electron in the ns range.

A monosilicated sintered fluorapatite (Ca 9 Nd(PO 4 ) 5 (SiO 4 )F 2 , britholite) was irradiated in the electronic stopping power regime with 85.8 MeV Krypton ions. The induced damage was characterized by means of X-ray diffraction. Following the evolution of crystallographic lattice parameters and the characteristic changes in the X-ray diffraction spectra, we showed the progressive damaging of this material. By calculating an effective radius ( R e ), damage in this britholite was quantified. The behaviour under thermal annealing was also studied by X-ray diffraction, using different durations of isothermal annealing (300 °C) in order to follow the structural rebuilding of the crystallographic lattice. From the evolution of the peak areas, we concluded that there is a partial rebuilding of the structure. This variation may be divided in two steps, according to the lattice parameters changes.

We have studied the carbonization of polyimide Kapton-H (pyromellitic dianhydride-oxydialinine, PMDA-ODA) thin films under heavy ion irradiations in the electronic slowing down regime. Irradiations were performed with 650-MeV Ni, 843-MeV Xe, 2.6-GeV Xe, 1.1-GeV Ta, and 707-MeV Pb ions that were transmitted through the polymer films with the electronic stopping power ranging between 3.5 and 17 keV nm−1. Room-temperature ac/dc electrical conductivity measurements, together with ESR, UV–visible optical absorption, and micro-Raman spectroscopy were used to characterize the irradiated films. These new data are compared to our previous results obtained with heavy ion irradiations in the 1-MeV uma−1 energy range. At the largest fluences near 1013 cm−2 the resulting carbonaceous material is found to be 8–9 orders of magnitude less conducting than with the slower ions. Such large dc-conductivity deviations are confirmed by the spin–lattice relaxation times deduced from the ESR line saturation measurements that are two orders of magnitude longer with the swift ions than with the slower ions. The evolution of the Raman spectra also shows that the appearance of a conjugated sp2-bonded structure is delayed with respect to the slow ion case, and is probably incomplete in the observed fluence range. The yield of paramagnetic centers is found to decrease when the ion energy increases. This is interpreted by an ion-velocity effect on damage due to a dilution of the deposited energy in the ion tracks. We think that this also induces a smaller sp2 cluster density impeding charge transport in the carbonaceous material.

Metal nanoclusters are induced for the first time by C6+ ion beam irradiation in aqueous solution. The results concerning monometallic silver and bimetallic gold–platinum systems are compared with those obtained by γ-rays and electron beam irradiation. The effects of linear energy transfer and dose rate on the formation yield, the size and the structure of the clusters are discussed.

Thanks to its high temperature properties and relatively good behaviour under irradiation, the MgAl 2 O 4 spinel is considered as a possible material to be used as inert matrix for the minor actinides burning. However, it is known to damage at high fluences. Several studies have shown that the damages induced by irradiation lead first to structural modifications and second to an amorphisation inducing an important swelling. In order to propose a better description of these structural modifications, we have irradiated different spinels at room temperature at Grand Accelerateur National d’Ions Lourds at Caen (GANIL) facility with swift Kr ions. The irradiation damages were characterised by Raman analysis and X-ray diffraction. Three different materials were irradiated, MgAl 2 O 4 and the isomorphic spinels ZnAl 2 O 4 and MgCr 2 O 4 , this allowing a better X-ray analysis of the cations distributions. Comparing our results with previously published ones, we show that the apparent damage of these materials do not depend on the irradiation conditions. In addition, we have unambiguously observed that the first damage stage is not a phase transformation but an order–disorder transition of the cationic sub-lattice. On the other hand, for the three materials, the cations are distributed on the classical 8a and 16d sites. The inversion rates we derive are however much higher than in non-irradiated materials at high temperatures. But in the Mg-materials, the cations are also located on the normally empty sites 16c and 48f, leading to highly disordered structures. We have then performed isochronal annealings, which show that the disorder recovers in one stage (ZnAl 2 O 4 ) or in two different stages (MgAl 2 O 4 and MgCr 2 O 4 ). The second stage can be attributed to the healing of the cation inversion rate, the first one to the displacement of the cations from the forbidden to the normal positions. In the three cases, the initial structure is totally healed after annealing at 1000 °C. These results could give some clues to explain the amorphisation stage of the spinels under irradiation and help in selecting a better inert matrix material.

Samples of monosilicated sintered fluorapatite (Ca 9 Nd(PO 4 ) 5 (SiO 4 )F 2 , britholite) and full-phosphated Durango fluorapatite were irradiated using different heavy ions with incident energies in the range of several hundred MeV, corresponding to the electronic stopping power regime. The induced damage was characterized by means of X-ray diffraction for the monosilicated fluorapatites and Rutherford backscattering spectrometry associated with channeling technique (CRBS) for the Durango fluorapatites. Characterizing the amorphization of the monosilicated fluorapatites revealed two main features. First, the evolution of the damaged fraction with the ion fluence and the ion species shows that amorphization is mainly dependent on the electronic energy loss ( S e ) value. Second, we suggest that a percolation of defects only occurs when S e is above a threshold near 5 keV nm −1 . This can be related to the limit of a fragmentation zone defined from microscopic observations. We have quantified damage in monosilicated fluorapatites by calculating amorphization effective radii ( R e ). By plotting these results versus S e , we found that they are in good agreement with those obtained from the irradiated single crystals of Durango fluorapatite.

Ion irradiation of SiO2 quartz at medium energy induces damage in the bulk as well as modification on the surface. To make a correlation between the bulk and the surface phenomena, AFM investigations on the SiO2 quartz surfaces, irradiated with Ni, Kr and Pb ions were performed. To avoid the overlap of the defects, the fluences were 5×109, 1×1010 and 6×1010 ions/cm2. The specific energies were between 2 and 6 MeV/u. The ion-induced damage surface was studied using a Digital Nanoscope III working in Tapping Mode, at ambient conditions. We observed hillocks induced by the irradiation with the different ions. The radius of hillocks has been compared with the radius of the tracks induced in the bulk. At high energy loss for dE/dx larger than 7 keV/nm, there is one hillock per ion, contrary to the observations of Wilson et al.

The radiolysis yields in pure water were determined using nanosecond pulse radiolysis using high linear energy transfer (LET) particles (1 ns pulses of high energy 1 GeV carbon ion beam). The main characteristics of this experiment were the nanosecond time resolution with heavy ion beam and the single value of LET along the ion track: 27 eV/nm. The kHz repetition rate of the pulsed beam used to reach a good signal-to-noise ratio in these experiments required the development of an acquisition method and a mathematical treatment of a DPO screen. The measured radiolytic yield for the hydrated electron at the nanosecond scale is quite high at 4.5×10−7 mol/J. A comparison of the experimental results obtained with a Monte Carlo simulation shows a rather good agreement at this LET value. To a certain extent this will allow a better adjustment of the Monte Carlo code.

The radiolytic yields of hydrogen peroxide in aqueous solution irradiated with ion beams at constant linear energy transfer (LET) values ranging from 2.5 keV/μm (30 MeV protons) to 30 keV/μm (1140 MeV carbon ions) and with 137Cs γ-rays, where the mean LET is 0.53 keV/μm, were determined. They are compared with those in the literature. The evolution of hydrogen peroxide yields is studied as a function of radical scavenger concentration. The radical-scavenging curves are discussed in terms of radical spatial distribution around the tracks. This distribution depends on both the type and the energy of radiation. This study also shows that the probing of the spatial structure for the proton track can be achieved by nitrate/methanol systems where the role of the nitrate is to protect hydrogen peroxide from the attack of hydrated electron.

We have done an extensive study of damage of polyimide (Kapton-H) thin films by heavy ion irradiations in the 1 MeV amu −1 energy range. We found that the irradiation-induced insulator–conductor transition proceeds through four stages on the basis of the progressive formation of a 3D graphite-like structure when track overlaps increase. All bulk dc conductivity and paramagnetic center volume density data were rescaled on a plot versus fluence ( φt ) times electronic stopping power ( S e ) squared i.e. φtS e 2 . Visible micro-Raman spectra were recorded in order to monitor the ion-induced modifications. It is seen that the spectral features of the pristine polymer progressively disappear during stages I and II, and that only two broad peaks at around 1360 and 1580 cm −1 , corresponding respectively to the well-known D and G bands of disordered graphitic materials, remain in stages III and IV regardless of the ion. We address the evolution of the polymer material according to the four stages of the transition versus φtS e 2 .

Upon γ -ray or argon ion irradiation of the lac repressor protein, its peptide chain is cleaved and the protein loses its lac operator-binding activity, as shown respectively by polyacrylamide gel electrophoresis and retardation gel electrophoresis. We developed phenomenological models that satisfactorily account for the experimental results: the peptide chain cleavage model considers that the average number of chain breaks per protomer is proportional to the irradiation dose and that the distribution of the number of breaks per protomer obeys Poisson's law. The repressor inactivation model takes into account the quaternary structure (a dimer of dimer) and the organization of the repressor in domains (two DNA binding sites, one per dimer). A protomer is inactivated by at least two different radiation-induced damages. A dimer is inactivated when at least one of the two protomers is inactivated. A tetramer is inactivated when both dimers are inactivated. From the combination of both models, we can deduce that chain cleavage cannot account for the protein inactivation, which should mainly result from oxidation of amino acid side chains. Indeed, particularly oxidizable and accessible amino acids (Tyr, His) are involved in the DNA binding process.

The formation of nano-hillocks on CaF2 crystal surfaces by individual ion impact has been studied using medium energy (3 and 5 MeV) highly charged ions (Xe19+ to Xe30+) as well as swift (kinetic energies between 12 and 58 MeV) heavy ions. For very slow highly charged ions the appearance of hillocks is known to be linked to a threshold in potential energy while for swift heavy ions a minimum electronic energy loss is necessary. With our results we bridge the gap between these two extreme cases and demonstrate, that with increasing energy deposition via electronic energy loss the potential energy threshold for hillock production can be substantially lowered. Surprisingly, both mechanisms of energy deposition in the target surface seem to contribute in an additive way, as demonstrated when plotting the results in a phase diagram. We show that the inelastic thermal spike model, originally developed to describe such material modifications for swift heavy ions, can be extended to case where kinetic and potential energies are deposited into the surface., 12 pages, 4 figures

International audience; Carbon implantation into titanium is known to enhance some of its surface properties like wear behavior, mechanical hardness or the friction coefficient. Therefore the method is a candidate to be applied as a powerful surface engineering tool for titanium alloys. Recently, a new implantation technique has been developed, which is based on a compact particle accelerator device that is easy to handle. The device allows simultaneous multi-charged ion-implantation (from C+ up to C4+) in order to get a plateau like implantation profile based on the energetic distribution. The aim of this study is to investigate microstructural modifications of the near surface region of Ti–6Al–4V due to this processing technology and to enhance the surface performance. Nanoindentation and tribological measurements revealed a threshold of critical C contents where friction coefficient and wear are significantly reduced. Furthermore, these enhancements have been correlated to the presence of additional graphitic carbon.

Polycrystalline samples of monoclinic zirconia (α-ZrO 2 ) have been irradiated at room temperature with 190 MeV 36 Ar and 170 MeV 84 Kr ions in the electronic slowing down regime. Room-temperature X-ray diffraction (XRD) and micro-Raman spectroscopy measurements show consistently that a phase transition to the tetragonal form (β-ZrO 2 ) occurs for 170 MeV 84 Kr ion irradiation above an electronic stopping power value around 15 MeV μm −1 . The kinetics of the transition were monitored by on-line XRD measurements on the same sample. No such phase transformation is seen with 190 MeV 36 Ar ion irradiation for an electronic stopping power value around 6 MeV μm −1 . The plot of the tetragonal phase fraction deduced from XRD measurements vs fluence is analysed with single-impact and double-impact kinetic models. The data seem to be in favour of a double ion impact process.

Samples of monoclinic zirconia were irradiated with heavy ions having incident energies in the range of a few hundred MeV giving then rise to a slowing down essentially caused by high electronic excitations. The characterizations of the samples by X-ray diffraction and complementary Raman spectroscopy analyses revealed two main features. First, in the electronic stopping power regime, it is only when the electronic energy loss is above a threshold near 13 keV nm−1 that monoclinic zirconia undergoes a transformation to the tetragonal phase. Second, the evolution of the amount of the tetragonal phase with the ion fluence exhibits a sigmoidal shape suggesting a mechanism for phase transformation which very likely needs two ion impacts.

The radiolysis of water with heavy ions of high linear energy transfer (LET) (-dE/dx) is characterized, in deaerated medium, by the production of superoxide anions, the radiolytic yields of which increase with the LET. Radiobiological interest in such radical species comes from the oxidative stress which may be generated by their dismutation in O2 and H2O2 in anoxic medium (radiotherapy with heavy ions). A brief review of the measurements of superoxide free radicals in aqueous solution by indirect or direct methods is presented. Moreover, some experimental results obtained by pulse radiolysis with Ar18+ ions (TEL = 290 keV·µm-1), are described. The interpretation of the kinetics takes into account the superoxide absorbance and that of hydrogen peroxide, which is present at the millisecond time scale.Key words: pulse radiolysis, heavy ions, superoxide radicals, high LET, kinetics.[Traduit par la Rédaction]

The new method described in this article allows the detection of low concentrations of radical species created in water for high linear energy transfer (LET) pulse radiolysis. The time-resolved chemiluminescence was used in a pulse radiolysis experiment at the Grand Accelerateur d'Ions Lourds (Caen, France) with an 40 Ar 18+ ion beam for the determination of radical yields. In water, for an LET of 280 eV/nm, the yield of OH is 2.2 10 -8 mol/J. A minimum value of the eaq - and HO2/O2 - yields is obtained. These experimental G values are compared to those obtained for the same LET. They are in good agreement with the values in the literature. The sensitivity of the time-resolved chemiluminescence method allows the measurement of concentrations of radicals species as low as 2 10 -7 M.

Dynamic and thermodynamic magnetization experiments on heavy-ion-irradiated single-crystalline ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ are correlated in order to clarify the nature of the mixed-state phase diagram. It is shown that whereas the entropy contribution to the free energy in the London regime plays a minor role in unirradiated crystals and irradiated crystals at fields close to or above the matching field ${B}_{\ensuremath{\varphi}},$ it becomes very important at low fields in irradiated crystals with high ${B}_{\ensuremath{\varphi}}.$ The direct determination of the entropy contribution to the free energy from the reversible magnetization allows one to determine not only the correct values of the pinning energy, but also to extract quite detailed information on pancake vortex alignment. The characteristic field ${H}_{\mathrm{int}}\ensuremath{\sim}\frac{1}{6}{B}_{\ensuremath{\varphi}}$ at which intervortex repulsion begins to determine the vortex arrangement and the reversible magnetization is shown to coincide with a sharp increase in the irreversibility field ${H}_{\mathrm{irr}}(T)$ and with the recoupling transition found in Josephson plasma resonance. Above ${H}_{\mathrm{int}},$ the repulsive interaction between vortices causes both the vortex mobility to decrease and pancake alignment to increase. At higher fields $\ensuremath{\gtrsim}\frac{1}{3}{B}_{\ensuremath{\varphi}}\ensuremath{\gg}{B}_{c1},$ free vortices outnumber those that are trapped on a columnar defect. This causes the decrease of the c-axis resistivity and a second crossover of the irreversibility field, to a regime where it is determined by plastic creep.

Cet article decrit les resultats obtenus par spectroscopie d'absorption resolue en temps sur les radicaux HO 2 /O - 2 et electron hydrate e - aq issus de l'irradiation de l'eau avec des ions lourds acceleres. Les experiences ont ete realisees au cyclotron du Grand Laboratoire National d'Ions Lourds (GANIL, Caen-France) avec les ions 12C6+ (75 MeV/A) et 40Ar18+ (70 MeV/A) dont le transfert d'energie lineique (TEL =-(dE/dx) elec ) est respectivement de 26 keV/μm et de 290 keV/μm. La structure temporelle du faisceau donne acces a des mesures de rendement radiolytique a t = 5 μs pour e - aq et t = 2 ms pour O - 2 , ainsi qu'a leurs temps de formation et de disparition. Les rendements mesures sont g(e aq ) = 0,4 molecules/100e pour un TEL de 26 keV/μm et g(O - 2 ) = 0,05 molecules/100eV pour un TEL de 290 keV/μm.

Time-resolved absorption spectroscopy has been used to detect radical species in water ionised by swift heavy ions. These experiments have been performed at the GANIL cyclotron (Caen–France) with 12C6+ (75 MeV/A) and 36S16+ (77 MeV/A) particles whose linear energy transfer (LET=−(dE/dx)elec is respectively two and three orders of magnitude greater than electron or gamma rays. The chemistry in water is thus considerably modified at the first moments after the ionisation. In particular the radiolytic yields of the radicals like hydrated electron decrease when the LET is increasing. The temporal structure of the beam is used to perform time-resolved spectroscopy of the transient radicals formed by water radiolysis within the microsecond time scale. It is possible to show the inhomogeneous chemistry around the ion tracks and to compare these results with the Monte Carlo simulations.

This study deals with the sputtering of uranium atoms from UO2 surfaces, induced by high 238U15+ and 116Sn36+ irradiation. The sputtered uranium atoms were collected on mica energy foils which were subsequently irradiated with thermal neutrons in order to fission the 235U. The fission fragments created latent tracks in mica which were revealed by chemical etching. Finally, we determined the track densities as a function of the emission angle in the mica detectors using three microscopy techniques: optical microscopy, SEM and AFM. The total yield of uranium emission and the angular distribution are given for both projectiles.

The description of the cross-linking induced by irradiation with high energy ions is a difficult problem. Indeed, the cross-links are not induced randomly as under electron or gamma irradiation: the probability to produce several events close to each others is high. Under swift ion irradiation, the production of large molecular masses directly in the path of a single ion is favoured. We present the results obtained by steric exclusion chromatography on the cross-linking of polystyrene irradiated with high-energy proton and carbon ions. The total cross-link yield and the partial yields of multiple cross-links increase with the electronic stopping power of the ion. For the highest electronic stopping power, a gel fraction can be produced directly in the track of the ion.

Cet article presente les premiers resultats obtenus avec une nouvelle experience de radiolyse pulsee montee en sortie d'un accelerateur d'ions lourds. Pour un TEL de 30 keV/μm, obtenu avec des macro-impulsions de 20 μs d'ions C 6+ d'energie 900 MeV, nous avons determine le rendement en electron hydrate dans l'eau pure desaeree en etudiant sa cinetique de formation et de disparition. Nous trouvons un rendement radiolytique de 0,16 molecule/100 eV, a la fin de l'impulsion. Le temps de demi-vie est de 53 μs.

The Neutrons For Science (NFS) facility is a component of SPIRAL-2 laboratory under construction at Caen (France). SPIRAL-2 is dedicated to the production of high intensity Radioactive Ions Beams (RIB). It is based on a high-power linear accelerator (LINAG) to accelerate deuterons beams in order to produce neutrons by breakup reactions on a C converter. These neutrons will induce fission in 238U for production of radioactive isotopes. Additionally to the RIB production, the proton and deuteron beams delivered by the accelerator will be used in the NFS facility. NFS is composed of a pulsed neutron beam and irradiation stations for cross-section measurements and material studies. The beams delivered by the LINAG will allow producing intense neutron beams in the 100 keV-40 MeV energy range with either a continuous or quasi-mono-energetic spectrum. At NFS available average fluxes will be up to 2 orders of magnitude higher than those of other existing time-of-flight facilities in the 1 MeV - 40 MeV range. NFS will be a very powerful tool for fundamental physics and application related research in support of the transmutation of nuclear waste, design of future fission and fusion reactors, nuclear medicine or test and development of new detectors. The facility and its characteristics are described, and several examples of the first potential experiments are presented., JRC.D.4-Standards for Nuclear Safety, Security and Safeguards

We have studied by Fourier transform infrared spectroscopy the chemical modifications induced by swift heavy ions in polystyrene. The overall destruction yield becomes very significant at high electronic stopping power ( d E d x ) e and the radiation sensitivity of this aromatic polymer merges typical values of equivalent aliphatic polymers as polyethylene. So, the radiation resistance conferred, at low ( d E d x ) e , to polystyrene by the phenyl side group is lost at high ( d E d x ) e . The creation of different unsaturated groups is also observed. They correspond to the vibration frequencies of alkyne, allene, vinylidene, vinyl and trans-vinylene groups. Moreover, the emergence of a wide band without any structure around 1600 cm−1 reveals the presence of double bonds with different degrees of conjugation. By comparison with the modifications induced in polyethylene, we discuss the role played by the phenyl side group and we consider the multiple ionisation of the aromatic ring as one possible way to induce the observed modifications.

Tracks of various heavy ions with energies up to 13 MeV/u were studied using the technique of selective chemical etching. It was found that for homogeneous track etching the energy loss of the ions has to surpass a threshold of about 450 eV/A. In a transition regime between 180 and 450 eV/A etching was possible but the mean diameter of the resulting pores showed a wider distribution than pores at higher energy losses. In order to describe this observation, the radial dose distribution was calculated using a Monte Carlo simulation code. Inhomogeneous etching is interpreted as due to the spatial fluctuations of the deposited energy along the ion path.

From the atomic data tables to the observations of a latent track in a solid, many different processes take place. The first one concerns the development of the electronic cascade around the ion path. The resulting energy distribution around the ion path should be considered as an input for the models which describes the relaxation of the matter under this dense electronic excitation. In this paper, we show that the mean values such as the linear energy transfer or the radial distribution of the dose are not sufficient to explain all the experimental results on the latent tracks. To go further one has to take into account the microscopic description of the density of events and above all one should not forget the specific structural or chemical responses of target.

Nous nous sommes propose d'etudier, a l'aide d'ions Ar 18+ (95 MeV/A) ayant un TEL constant (250 eV.nm -1 ), les rendements de reduction du tetranitromethane (TNM) en phase aqueuse a pH 7. Le TNM est reduit non seulement par les electrons hydrates et les radicaux H, mais egalement par les radicaux superoxyde. Nous avons determine l'influence de doses d'irradiation croissantes de 100 Gy a 1000 Gy (debit de dose 10 Gy. s -1 ) dans des solutions de TNM 3,2x10 -4 mol.l -1 aerees, ou saturees de N 2 , ou de N 2 O. Les rendements de reduction du TNM ont ete mesures et les valeurs de G e - aq et de G O 2 - qui en ont ete deduites ont ete comparees a celles de la litterature.

We have measured the low temperature luminescence of the self-trapped excitons, STE, in NaCl submitted to very dense electronic excitations induced by swift heavy ions. We have compared the features of the excitonic luminescence excited by X-ray and by high energy ion irradiations. The luminescence yield results from a competition between radiative (temperature independent) and non-radiative (temperature dependent) recombinations. For swift heavy ion irradiations, the high density of the deposited energy is supposed to induce a very significant transient temperature increase in the vicinity of the ion path. In this paper we have studied the influence of a thermal spike on the STE luminescence yield. Using numerical computations based on equilibrium thermodynamics, we predict the local increase of the temperature as a function of time t, and of the distance r, from the ion path. At every (r, t) we calculate the temperature induced decrease of the STE non-radiative recombination lifetimes, and we deduce the corresponding changes in the STE luminescence yields. It appears that the numerical predictions of the luminescence yield are very sensitive to the radial extent of the energy deposition, and consequently of the STE concentration. The role of the different parameters and the hypotheses of the calculations are discussed.

The modifications induced by the high energy ions in materials may be understood only if the particularities of the energy transfer from the ion to the target are considered. This is true in particular for polymers. Indeed the ion irradiations are characterised by their large value of the linear energy transfer and certainly by their spatial distribution of the primary events and of the damages. The primary events are strongly correlated to each other: they are mainly located in a small cylinder centred on the ion path. The density of ionisation and the radius of this cylinder (the core region) depend on the projectile and on its velocity. Roughly, the higher the ion energy, the larger the radius is and the lower the ionisation density is. So the dose (the amount of energy absorbed by unit mass of the target) is not sufficient to characterise a high energy ion irradiation. In this paper we describe the physical aspects of the ion irradiation and we shall demonstrate that three parameters are needed to have a non-ambiguous description of these irradiations. They should be, for example, the atomic number, the velocity and the fluence.

We have studied the effects of dense electronic excitations on vinyl linear polymers, by performing swift heavy ion, SHI, irradiations. We used different ion beams, from C to Pb, provided by the GANIL accelerator at energies of a few MeV/u. We mainly studied the physico-chemical modifications induced in polyethylene (PE), but the role of chemical substitutions has also been investigated by studying the swift heavy ion induced damage in polyvinylidene fluoride (PVDF) and polystyrene (PS). The irradiated samples were analysed ex-situ by means of Fourier transform infrared spectroscopy in the transmission mode. Any contact with air was avoided: oxidation does not occur. Swift heavy ion irradiations are characterised by a significant increase of the yield of chain scission associated with unsaturated end groups. Moreover, we have evidences for specific modifications, i.e. modifications which are never observed when using low ionising particles as electrons or gamma-rays; namely the creation of alkyne and allene end groups. These specific modifications are little sensitive to chemical substitutions. For instance, alkyne formation is observed in PE, PVDF and PS. A simultaneous ionisation of the different atoms of a constituting monomer is likely needed for triggering the formation of the specific swift heavy ion induced modifications. On the other hand, if we pay attention to the physico-chemical modifications which are easily induced by low ionising particles, it is observed that increasing the electronic stopping power does not significantly modify the creation yield of, for instance in PE, trans-vinylene or trans-trans diene groups.

We studied the Hall effect in a ${\mathrm{Tl}}_{2}{\mathrm{Ba}}_{2}{\mathrm{CaCu}}_{2}{O}_{8}$ epitaxial film and in an ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7}$ single crystal in the mixed state before and after irradiation with high energy Pb ions. Pinning enhancement due to irradiation-induced columnar defects leads to the decrease in magnitude of the longitudinal and Hall resistivities, but does not modify the behavior of the Hall conductivity. This result is valid independent of the sign of the Hall effect in the pinned region (positive for ${\mathrm{Tl}}_{2}{\mathrm{Ba}}_{2}{\mathrm{CaCu}}_{2}{O}_{8}$ and negative for ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7}$). The present work proves straightforwardly that the mixed-state Hall conductivity does not depend on the pinning strength, in agreement with theory. This result is a dual analog of the behavior of 2D electronic systems where the Hall resistivity remains unaffected by disorder.

International audience; Transmission electron microscopy (TEM) experiments were carried out on the JANNUS platform (Joint Accelerators for Nano-science and NUclear Simulation) at CSNSM (Center of Nuclear Spectrometry and Mass Spectrometry) laboratory in Orsay. The experiment was devoted to the study of the evolution of the xenon aggregate population with increasing implantation fluence. A thin UO2 foil was implanted at fluences ranging from 3 x 10(12) to 7 x 10(14) at cm(-2) with 390 key Xe3+ ions at an irradiation temperature of 873 K. The TEM results indicate the presence of nanometer size bubbles above a fluence of 6 x 10(12) Xe cm(-2) and an increase in the bubble number density was observed between 6 x 10(12) Xe cm(-2) and 2 x 10(14) Xe cm(-2). Above 2 x 10(14) Xe cm(-2), the number density levels off at 4 x 10(23) +/- 0.5 x 10(23) m(-3). (C) 2011 Elsevier B.V. All rights reserved.

The high energy density of electronic excitations due to the impact of swift heavy ions can induce structural modifications in materials. We present a X-ray diffractometer called ALIX, which has been set up at the low-energy IRRSUD beamline of the GANIL facility, to allow the study of structural modification kinetics as a function of the ion fluence. The X-ray setup has been modified and optimized to enable irradiation by swift heavy ions simultaneously to X-ray pattern recording. We present the capability of ALIX to perform simultaneous irradiation - diffraction by using energy discrimination between X-rays from diffraction and from ion-target interaction. To illustrate its potential, results of sequential or simultaneous irradiation - diffraction are presented in this article to show radiation effects on the structural properties of ceramics. Phase transition kinetics have been studied during xenon ion irradiation of polycrystalline MgO and SrTiO3. We have observed that MgO oxide is radiation-resistant to high electronic excitations, contrary to the high sensitivity of SrTiO3, which exhibits transition from the crystalline to the amorphous state during irradiation. By interpreting the amorphization kinetics of SrTiO3, defect overlapping models are discussed as well as latent track characteristics. Together with a transmission electron microscopy study, we conclude that a single impact model describes the phase transition mechanism., 12 pages, 8 figures, Accepted to Review of Scientific Instruments

We study the angular dependence of the magnetic properties of Y-ba-Cu-O thin films irradiated with 0.86 GeV Pb and 5 GeV Xe ions. For the Pb irradiated samples the critical current has a maximum when the direction of the external magnetic field coincides with the direction of the columnar defects induced by the irradiation. For the Xe irradiated samples such anisotropy in the critical current was not found. The pinning force density obeys a scaling law of the form b p (1 − b ) q , where b = H ext / H irr ( T ), and H ext and H irr are the external and the irreversibility fields, respectively. The exponents p and q depend on the type and direction of the irradiation.

Damage induced in several oxide materials by swift heavy ions is presented. The discussion is based on results obtained on the following materials [Y3Fe5O12, AFe12O19 (A = Ba, Sr), BFe2O4 (B = Ni, Mg, Zn), ZrSi2O4, SiO2 quartz, Al2O3, high Tc superconductors (YBa2Cu3O7 − δ and Bi2Sr2CaCu2O8)] which have been irradiated by ions with atomic number ranging between 6 (12C) and 92 (238U) and energies between 0.05 GeV and 6 GeV. The damage cross section A has been deduced using several physical characterisations like Mossbauer spectrometry, saturation magnetisation measurements, channeling Rutherford backscattering, infrared absorption and electrical resistance measurements. Depending on the material and on the value of the electronic stopping power (dE/dx) the damage cross section varies between 10−17 and 10−12 cm2. Using medium and high resolution transmission electron microscopy and chemical etching of the latent track, an electronic stopping power evolution of the damage morphology has been observed leading to the definition of an effective radius Re of the latent track which can be linked to the damage (amorphous) cross section A by the relation Re = √A/π. Moreover there is a direct correlation between these values and the damage morphology: for Re > 3 nm the latent tracks are long and cylindrical, conversely for Re < 3 nm the damage is inhomogeneous along the latent track. The effect of the irradiation temperature, of the crystallographic orientation, of the initial electrical resistivity and of the oxygen stoichiometry will be presented. In opposition to what has been usually believed it will be shown that alumina (Al2O3) is indeed sensitive to the electronic stopping power. Moreover the velocity of the incident ion has a direct influence on the damage production: the lower the velocity, the higher the damage.

We have studied the effects of dense electronic excitations on the physico-chemical modifications of polymers by performing heavy ion irradiations in the energy range of some MeV amu −1 . The effects induced by swift heavy ion irradiations were compared to those induced by MeV electron irradiations performed in similar experimental conditions in polyethylene and poly(vinylidene difluoride) films. The irradiated samples were analysed ex situ by means of Fourier transform infrared spectroscopy in the transmission mode. High electronic stopping power, (d E /d x ) e , irradiations are characterised by a significant increase of the yield of chain scission. Vinyl terminal unsaturations are recorded with radiochemical yields increasing markedly as (d E /d x ) e increases. Moreover, characteristic bands of alkyne terminal groups were observed only above a threshold of (d E /d x ) e . The overall set of results is analysed taking into account the radial dose deposition predicted by numerical calculations and the defect creation measured after electron irradiations. This allows us to elucidate the kind of chemical modifications influenced by the local dose rate; i.e. for which a specific effect due to a dense electronic excitation appears.

In this paper the swift heavy ion interactions with condensed matter are studied from the point of view of the modifications induced in the electronic subsystem of the target. A Monte Carlo method is used to describe event by event the interactions of the projectile with the target electrons as well as the evolution of the electronic subsystem. The validity of the method and the results are discussed. This detailed picture of the excited target could be used for further explanations and calculations of the damage creation by electronic excitation. We have focused our attention on two materials whose electronic properties are different: graphite and quartz. For both materials a quantitative analysis of the energy deposition mechanism is given.

We present the results of simultaneous in situ luminescence and optical absorption studies of alkali-halides, submitted to very dense electronic excitations induced by swift heavy ion irradiations at low temperatures (15–200 K). X-ray irradiations performed in the same experimental conditions permit the necessary comparison with ion irradiations. The luminescence of the self-trapped excitons is only slightly modified by increasing the electronic stopping power, while new features appear for the point defect creation. For instance, in NaCl at 15 K, F centres are efficiently created by Ne, Zn and Xe irradiations and F2 centres only by Zn and Xe irradiations. We discuss the evolution of the yields of defect creation as a function of the temperature and of the electronic stopping power.

Les phenomenes elementaires de l'interaction des ions avec la matiere ont beaucoup ete etudies, mais ce n'est que recemment que les modifications induites par les ions lourds rapides ont ete decrites et que des modeles de creation de defauts ont ete affines. Le defi pose par ces inadiations provient du caractere collectif des phenomenes mis en jeu qui resultent d'une forte densite locale d'ionisation et d'un important debit de dose. Les rendements de creation de defauts vont, en general, etre augmentes et dans certains cas, un desordre particulier va etre induit tout le long du trajet de l'ion: une trace latente

International audience; The "Neutrons for Science" (NFS) facility will be a component of SPIRAL‐2, the future accelerator dedicated to the production of very intense radioactive ion beams, under construction at GANIL in Caen (France). NFS will be composed of a pulsed neutron beam for in‐flight measurements and irradiation stations for cross‐section measurements and material studies. Continuous and quasi‐monokinetic energy spectra will be available at NFS respectively produced by the interaction of deuteron beam on thick a Be converter and by the 7Li(p,n) reaction on a thin converter. The flux at NFS will be up to 2 orders of magnitude higher than those of other existing time‐of‐flight facilities in the 1 MeV to 40 MeV range. NFS will be a very powerful tool for physics and fundamental research as well as applications like the transmutation of nuclear waste, design of future fission and fusion reactors, nuclear medicine or test and development of new detectors.

Epitaxial ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ thin films irradiated with swift heavy ions under different directions showed a strongly changed angular dependence of the critical current density ${\mathit{J}}_{\mathit{c}}$(B,T,\ensuremath{\vartheta}) in the mixed state. Additional peaks, which dominate the angular dependence of ${\mathit{J}}_{\mathit{c}}$, appear at angles where the magnetic field is parallel to the irradiation direction, due to the strong pinning of the introduced linear defects. Irradiated ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$/${\mathrm{PrBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ superlattices, however, reveal no additional ${\mathit{J}}_{\mathit{c}}$ peaks but an isotropic ${\mathit{J}}_{\mathit{c}}$ enhancement in a wide angular range. This contrary behavior could be explained by flux lines of different dimensionality.

Epitaxial YBa 2 Cu 3 O 7−δ (YBCO) thin films and YBa 2 Cu 3 O 7−δ /PrBa 2 Cu 3 O 7−δ (Y/Pr) multilayers were irradiated with high energy heavy ions (770 MeV 208 Pb and 340 MeV 129 Xe) under varius directions Φ relative to the c-axis. The irradiation resulted in columnar defects tilted by Φ from the c-axis. The angular dependence of their pinning activity was studied by measuring the anisotropy of the critical current density. The J c (B,T,θ) behaviour of the irradiated YBCO thin films showed an additional peak, which exceeds the intrinsic pinning peak, exactly at the irradiation direction. The Y/Pr multilayers, however, showed an isotropic J c -enhancement by a factor of 5, without any additional structure in the J c (B,T,θ)-curve.

(1993). Irradiation effects of high energy ions in superconductor YBa2Cu3O7. Radiation Effects and Defects in Solids: Vol. 126, No. 1-4, pp. 155-158.