SHIM 2015 Swift Heavy Ions in Matter

All atoms and molecules can – even in their ground state – form clusters, weakly bound molecules, held together by the van der Waals force. The smallest if this type is the dimmer, composed of two atoms/molecules. While the Ne dimer is a representative for rare gas dimers in general, the He dimer is a quite exotic object, with a broad internuclear distribution, stretching up to several 100 a. u. Here we investigated the ionization and fragmentation dynamics of He2 and Ne2 induced by ion impact (11.4 MeV/u, S14+). We employ the technique of COLTRIMS reaction microscopes to determine the momenta of all fragments in coincidence. Thereby different pathways are accessible depending on how the electrons have been removed from the atomic sites. The two dominant mechanisms are: 1.) The direct mechanism: Here the projectile ionizes each of the two atoms individually. The dimer’s constituents have ionization properties similar to those of a single atom, completely different than what is known for a covalent bound molecule. The ionization dynamics strongly varies with the impact parameter b. But its measurement is rather difficult, if possible at all. Especially for large b, which dominate ionization, are believed not resolvable. Here the nuclear scattering is smaller than the typically exchanged momentum with the electron. Leading to ambiguities, the impact parameter is inaccessible through any momentum transfer measurement between the nuclei. Here we show that the large internuclear distance of rare gas dimers opens a new way to this puzzling question. Focusing on the two electron release, the impact parameter dependent ionization probability P(b) leads to a maximum angle between the molecular axis and the ion beam. Further tilts result in the ionization of only one atom. 2.) In some cases, an ionized atom stays electronically excited. This energy is efficiently release via the Interatomic Coulombic decay (ICD). Predicted in 1997 and in photoionization experiments observed in 2004, ICD is an extermely efficient source for the production of low energetic electrons. It probably plays a significant role for radiation damage in living tissue and for ion radiation therapy.

Non-equilibrium and equilibrium charge state distributions for 2.0 MeV/u Sq+ (q = 6−16) and Cq+ (q = 2−6) ions after penetrating carbon foils have been investigated experimentally. Those wide ranges of the initial charge states have proved that charge state distributions, mean charge states, and distribution widths for projectile ions without K-shell holes, Sq+ (q = 6−14) and Cq+ (q = 2−4), once coincided at a target thickness of 6.9 and 5.7 micro-g/cm2, respectively, showing a "quasi-equilibrium", and simultaneously evolved to establish a real equilibrium when the foil thickness was increased further. Those for projectile ions with K-shell hole(s), S15, 16+ and C5, 6+, evolved differently and directly to the real equilibrium, established at a target thickness of around 100 micro-g/cm2 or greater for S ions and at over 10 micro-g/cm2 for C ions. The quasi- and real-equilibrium mean charge states for 2.0 MeV/u S ions were 12.3 and 12.68, respectively, whereas those for 2.0 MeV/u C ions were 5.48 and 5.57. Simulations using ETACHA code and solution of simpler rate equations showed that the quasi-equilibrium was brought by a difference between the reaction-rates for K- and L-shell processes.

Fast Highly Charged Ions (HCIs) going through matter induce material modifications and, in turn, their stopping power, charge state and excited states are affected by the material encountered. Here, we report on experimental studies, performed at GANIL, on the production and transport of HCIs excited states in thin solid targets in the so-called high velocity domain. Solids of various thicknesses to investigate the transport effects have been used but also atomic targets to control the primary process that populates the projectile excited states. With the development of quantum transport theories to treat, on the same footing, all the competing processes, we have reached an unprecedented precision in the description of the ion transport in matter in this perturbative regime. On the other hand, in the non-perturbative regime, where the ion stopping power is maximum, the probabilities related to all the primary electronic processes are of the same order of magnitude. This leads to “interference effects” and makes the determination of experimental cross sections of single elementary collision processes extremely difficult. To overcome this issue, we propose a project, named FISIC*, that will allow studying ion-ion collisions under well controlled conditions. Our goal is to reach experimentally the true three-body system and then add additional electrons, one by one, to explore the quantum dynamics of N-body systems. Those experiments are now possible with the avenue of the new large scale facilities such as GANIL/SPIRAL2 and FAIR/CRYRING. * FISIC for Fast Ion-Slow Ion Collisions

Since the prediction of the Interatomic Coulombic Decay (ICD) by Cederbaum et al. in 1997 [1], the rare gas atomic dimers have been widely investigated by photon impact. However, the investigation of dimers with the ions and electrons as the projectile is still scare [2-6]. For neon dimer, only a few works involved with heavy ions were reported [4]. Utilizing the reaction microscope [7], we investigated the fragmentation of neon dimer induced by highly charged O6+ ion at the projectile energy of 240 keV. In the present work, we clearly observed four peaks in the spectrum of kinetic energy release (KER) for Ne+-Ne+ pair, which locate at 4.5, 7.3, 8.5, and 9.7 eV, and are marked by A, B, C, and D successively. By comparing with the potential curve of Ne2 [8], we clarified the fragmentation mechanisms of them. The peak A results from the coulombic explosion (CE) and ICD, while the peak B results from radiation charge transfer (RCT) of one-site states Ne2+(2p4)-Ne. The peaks C and D can be ascribed to the contribution of the radiationless charge transfer [9]. These two peaks were the first time observed in transfer ionization and pure double electron capture processes induced by heavy ions. This work was partially supported by the 973 Program of China under Grants No. 2010CB832902 and by the NSFC of China under Grants Nos. 10979007, 10974207 and 11274317. References [1] L. S. Cederbaum et al 1997 Phys. Rev. Lett.79, 4778. [2] J. Matsumoto et al 2010 Phys. Rev. Lett. 105, 263202. [3] J. Titze et al 2011 Phys. Rev. Lett. 106, 033201. [4] H.-K. Kim et al 2013 Phys. Rev. A 88, 042707; 2014 Phys. Rev. A 89, 022704. [5] S. Yan et al 2013 Phys. Rev. A 88, 042712; 2014 Phys. Rev. A 89, 062707 [6] W. Iskandar et al 2014 Phys. Rev. Lett. 113, 143201. [7] X Ma et al 2011 Phys. Rev. A 83, 052707. [8] S D Stoychev et al 2008 J. Chem. Phys. 129, 074307. [9] K. Kreidi et al 2008 Phys. Rev. A 78, 043422.

The space environment is inhospitable to humans and the spacecrafts utilised by us to access space, its systems, subsystems and EEE component. An important element of the space environment is the abundance of high energy particles, constituting the natural space radiation environment. The space radiation environment detrimentally affects EEE components flown on space missions. The impact on electronic components vary from slow degradation of electrical parameters, due to cumulative effects, or sudden unwanted events due to transient effects. In this presentation, we will show several cases of single event effects (SEE) and the associated radiation hardness assurance (RHA) issues. The presentation will be divided in three parts: - In a first part, we will illustrate a major difficulty usually encountered in space projects, which is the traceability of the design and fabrication process when procuring parts from semiconductor manufacturers, and consequently the representativeness of the SEE tests performed before flight. Any modification in the design or process will induce a different SEE response, potentially catastrophic. Examples of this type of SEE issue encountered in the frame of space projects will be presented: (a) latch-up in a SRAM memory, (b) burn-out in a quad CMOS driver, used as a clock driver for CCDs. - In a second part, SEE in two component types, Flash-based FPGAs, and Floating-gate memories, will be detailed. Both show re-programming failures after irradiation. The impact on their flight mission is though significantly different: it will directly affects the memory primary function, while FPGA are usually not reprogrammed in flight, except in few exceptional situations. The failure mechanisms, as well as other effects, such as single event upsets and transients (SEU and SET) will be shown from both broad beam and microprobe experiments. - Finally, the example of new types of power devices, based on silicon carbide, will be highlighted and compared to silicon ones. The failure mechanism in silicon carbide is resolutely different from silicon based devices, and will necessitate to adapt SEE test methods and RHA rules. Based on these examples, we will conclude with general considerations on failure sources in EEE components used in space and methods to prevent these failures.

Due to their excellent mechanical properties, corrosion resistance, fatigue strength, low density and low activation under irradiation, titanium (Ti) alloys are currently being considered for use as a structural material for the beam dump shell for the Facility for Rare Isotope Beams (FRIB): A new generation accelerator with high power heavy ion beams. The capability of the FRIB to operate at full beam power depends on the beam dump being able to absorb up to a 325 kW beam power (with primary Beam from O to U). Ti-6Al-4V (grade 5) is the preferred candidate for this beam dump shell material. A significant increase of beam dump lifetime with respect to fatigue due to thermal cycling can be expected for the rotating beam dump if Ti-6Al-4V with an addition of 1% boron (Ti-6Al-4V-1B) is used [1]. Two sets of samples of both Ti-6Al-4V and Ti-6Al-4V-1B were irradiated at the IRRSUD beam line at the GANIL CIMAP, Caen France with swift heavy ion beams respectively 36Ar (36MeV, Se =7.5keV/nm) and 131Xe (92MeV, Se =19.7 keV/nm). The samples were polished and etched before irradiation and selected areas on the surfaces of the samples were characterized before and after irradiation using Scanning Electron Microscopy and Electron Backscatter Diffraction. In addition, Vickers hardness and nano-indentation measurements were also used to probe the change in hardness and elastic modulus as a function of the depth. This talk will describe irradiation setups and the post irradiation techniques used to characterize the material. The results indicate a low-radiation damage sensitivity in both materials. This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, the State of Michigan and Michigan State University. [1] W. Chen, C. J. Boehlert (2009). Materials Transactions,, Vol. 50, No. 7 pp. 1690 to 1703.

Beam induced hardening and thermal conductivity degradation plays an important role in the failure of targets, beam catchers, beam windows and collimators for the new generation of high power accelerators (Large Hadron Collider, Facility for Antiproton and Ion Research, Facility for Rare Isotope Beam). Operating at high temperatures is expected to anneal significantly the radiation dam-age. The goal of this work is to investigate the effect of damage recovery on thermal diffusivity and hardening behavior of high-temperature ion-irradiated graphite by Raman spectroscopy, photo-thermal radiometry and nanoindentation. Information on ion-induced thermal conductivity degradation of materials is in general extremely scarce. We present the first experimental data on thermal diffusivity of isotropic graphite thin foils irradiated with 8.6 MeV/u 197Au ions, at temperatures up to 1600 °C, done by innovatively using a photothermal radiometry method for this type of samples. Nanoindentation tests have been performed for following the influence of the irradiation temperature on the hardness and Young modulus of the same ion exposed graphite samples. At high irradiation temperatures, the degradation of thermal diffusivity and the ion induced hardening are less pronounced due to enhanced vacancy mobility. Our results advocate operation temperatures above 1000 °C for graphite targets and beam catchers.

Single event effects (SEEs) in semiconductor devices is a phenomenon of increase importance with the development in device technology. In this work, the SEE tests have been carried out by heavy ions from HIRFL accelerator. The Geant4 simulations have been performed to better understand the experimental results. The test strategies for new technologies of very large-scale integration are studied. The influences of heavy ion parameters on devices are investigated, systematically. The results indicate that some important parameters for SEE testing, such as ion energy, ion range, beam flux, beam angle etc. have effects on the results. The angular dependence of multiple bit upset responses in a series of SRAM devices has been performed. We observed that the differences depend on the ion species and devices. Therefore it is important to select proper test conditions to ensure the experiment performed correctly. We have done the computational simulation of single event upset (SEU) induced by the passage of heavy ions through the device with Geant4-tool based on Monte Carlo transport code. The key parameters affecting SEU occurrence are examined, and related geometrical construction and critical charge are all quantified. The multi-functional package for SEU analysis has been successfully programmed and applied for SEU occurrence after completion of device geometrical construction, critical charge and SEU cross section calculation.

The XPnano group at LSI (Ecole Polytechnique, France) synthesises nanoporous polymer membranes using ion track technology in collaboration with the CIMAP (GANIL). The zone of defects along the ion-trajectory, namely the latent track, is rich of radicals in numerous polymers and may be directly modified chemically by radio-induced grafting (Ion-track grafting). Latent tracks may also be etched to obtain either cylindrical pores of monodiperse radii ranging from 10 nm to few microns or other geometries like biconical shapes with an aperture of only few nm. The remanence of radicals after etching in a semi-crystalline PVDF membrane was proven in our group by EPR for pore diameter inferior to 100 nm and the subsequent radiografting was localized by Confocal Laser Scanning Microcoscope. This property allows us to radiograft, very locally, a hydrophilic polymer in a hydrophobic matrice from nanopore walls. Using controlled radical polymerization (i.e. RAFT mechanism), the grafted layer can be tuned very accurately from nanometric coverage of nanopore walls to complete blockage of the pores and appearance of radiografted chain protusions at the membrane surface. Ion-track grafting have permitted the fabrication of many devices in our group. Some achievements were obtained in proton-exchange membrane fuel cell (automotive application) and in water quality sensors for toxic metal ions at the trace level (sub-ppb sensitivity). Track-etched membranes are also routinely used as template to grow metallic nanowires (NWs) by electrodeposition. It opens the field of research to composite membranes. Non-conventionnal behaviour of embedded Ni NW magnetoresistance have been registered when biconical NWs are contacted. An experimental set-up at LSI allows contacting only one NW over billions. Combined to electroactive polymers such as piezoelectric β-PVDF, recent results have shown a giant magnetostrictive effect in a single Ni NW induced by mechanical stress.

Metallic nanowires have great potential for future plasmonic applications. By varying nanowire dimensions, composition, shape and morphology, their plasmonic resonance frequency and near field characteristics can be tuned for specific sensing functions in the infrared and visible light range. For their implementation as sensors, however, two main challenges are being tackled: (i) the nanostructures plasmonic performance must be understood and optimized and (ii) stable and complex assemblies of nanowires such as networks and arrays must be developed. In this overview, we demonstrate how ion-track nanotechnology combined with electrochemical deposition allows the tailored synthesis of complex structures including three dimensional interconnected nanowires. Moreover, the deposition of special AuAg alloy wires is presented with Au:Ag concentrations tailored by varying the synthesis parameters. Chemical dissolution of the Ag content produces wires and mechanically stable networks of high porosity. The tremendously increased effective surface is of great interest for providing plasmonic hotspots. Compared to smooth nanowires, highly porous Au nanowires show a red-shift of their plasmon resonance frequency as demonstrated by electron energy-loss and infrared spectroscopy.

Graphene is an ultimate thin membrane with carbon atoms arranged in a honeycomb lattice and extra high mechanical property. Introduced nanopores in graphene can be used in water desalination technologies because of high efficiency in rejecting salt ions. Here, swift heavy ion was used to prepare single nanopore in monolayer graphene which was transferred to PET membrane. After asymmetric etching of irradiated PET membrane, the PET suspended graphene nanopre can be obtained and used to carry out the ionic transport study. In order to investigate the rectification effect of suspended graphene nanopore, three electrolytes with monovalent cations LiCl, NaCl and KCl are chose for current-voltage measurement, respectively. Obvious rectification effect was confirmed in the electrolytes of KCl and the rectification ratio can be adjusted by varying the concentration and pH value of KCl solutions. The giant rectification ratio of 190 was observed in 0.02 M KCl with the pH value of 2.

Since two-dimensional materials with their unique physical properties have become accessible to experimental physics, the scientific interest in this material class has been very high as they promise a multitude of possible applications. In particular, it has been shown that ionizing particle irradiation allows structuring of these 2d materials [1- 4]. In addition to graphene, so-called carbon nanomembranes (CNMs) also belong to the class of the new two-dimensional materials. They offer the advantage that they can be produced and transferred by standard chemical and physical methods instead of mechanical exfoliation. For this experiment we have prepared single layer graphene as well as CNMs samples. The latter were prepared by electron induced crosslinking of aromatic self-assembled monolayers like biphenylthiol which was evaporated on copper [5,6]. Our samples have been irradiated with swift heavy ions under glancing angles of incidence. The samples were analysed by atomic force microscopy in ambient conditions and in ultrahigh vacuum. The latter measurements served as test measurements for our newly built setup at the M branch of the UNILAC beamline in GSI (Darmstadt, Germany) and were performed in-situ directly after irradiation. The CNMs show modifications in form of extended pores with shapes different from those which we typically observe in graphene. Finally, experiments performed at different accelerator facilities (GSI, GANIL, and RBI) with different beams energies were used to determine the threshold for pore formation. References: [1] S. Akcöltekin et al., Appl. Phys. Lett. 98 (2011) 103103 [2] O. Ochedowski et al., Appl. Phys. Lett. 102, 153103 (2013) [3] J. Hopster et al., 2D Materials 1 (2014) 011011 [4] R. Ritter et al., Appl. Phys. Lett. 102, (2013) 063112 [5] A. Turchanin and A. Gölzhäuser, Prog. Surf. Sci. 87, 108 (2012), [6] D.G. Matei et al., Adv. Mater. 2013, 25, 4146–4151

After a brief historical and personal view on some highlights concerning ion tracks I will concentrate on the present state of understanding and modelling of track formation. The frequently used inelastic thermal spike model requires substantial modification with regard to two aspects. The first aspect concerns the assumption that the concentration of free carriers is independent of time and of the distance from the ion path. This assumption is only acceptable for metals but not for insulators and semiconductors. Several groups have now identified this deficiency and try to find solutions by following carrier production and subsequent processes in great detail. The progress made and the encountered difficulties will be outlined. The second aspect concerns the fact that the inelastic thermal spike model ignores thermal stresses. More precisely, the energy transferred from the electronic system to the atomic system appears not completely as heat as it is assumed in the inelastic thermal spike model, but is shared between heat and mechanical work (a generalization of the term pδV in the first law of thermodynamics). The importance of this term for the energy balance will be demonstrated and the consequences with regard to melting and boiling will be discussed. It will turn out that, if the excitation in the track is sufficiently large, dislocation generation is much more probable than boiling. Experimental evidence for this process will be provided and its consequences for the radiation resistance of some non-amorphizable materials like NiO, MgO, and UO2 will be demonstrated.

FAIR with its intense beams of ions and antiprotons provides outstanding and worldwide unique experimental conditions for extreme matter research in atomic and plasma physics and for application oriented research in biophysics, medical physics and materials science. The associated research programs comprise interaction of matter with highest electromagnetic fields, properties of plasmas and of solid matter under extreme pressure, density, and temperature conditions, simulation of galactic cosmic radiation, research in nanoscience and charged particle radiotherapy. A broad variety of APPA-dedicated facilities including experimental stations, storage rings, and traps, equipped with most sophisticated instrumentation will allow the APPA community to tackle new challenges. The worldwide most intense source of slow antiprotons will expand the scope of APPA related research to the exciting field of antimatter.

In this talk I will give an overview of the transient nonequilibrium electron and atomic kinetics after high-energy deposition in dielectric. An ultrafast energy deposition can be made my means of x-ray free-electron laser (FEL) irradiation or swift-heavy ion (SHI) beams. The differences between the two methods will be discussed. In both cases, first, the electron subsystem of a dielectric is excited. Electrons are provided with energy up to a few tens of keV, which initiates nonequilibrium electron kinetics. High-energy electrons then perform secondary cascading and exchange energy with the lattice. The different channels of scattering and their simulation challenges will be addressed. Dielectrics and semiconductors under irradiation with intense femtosecond laser pulses can undergo a phase transition via two different channels: thermal and nonthermal. Their difference will be discussed in detail. The first one occurs if the lattice is heated strongly enough by electron-ion (electron-phonon) coupling. The second one results from the modification of the atomic potential energy surface by excitation of electrons from the valence to the conduction band. I will present our developed approach to include both channels within a consistent framework. The developed hybrid model consists of tight-binding molecular dynamics (TBMD) for modeling atomic system with the potential energy surface dependent on the state of electronic system [1]. Simultaneously, electronic state is traced with the Boltzmann equation for low-energy electrons, and with a Monte Carlo model for high-energy electrons. With this model it is possible to study different channels of energy dissipation in dielectrics. Examples of thermal and nonthermal melting and their interplay will be presented for silicon and diamond. [1] N. Medvedev, H.O. Jeschke, B. Ziaja, New Journal of Physics 15, 015016 (2013)

Organic polymers display some of the most prevalent applications in ion track technology. With the high susceptibility of ion tracks to chemical etching, track-etched polymers are commonly utilized for the production of nano-porous track-membranes and filters, embedding microelectronic devices such as micro-capacitors, diodes and nanowires as well as for in-vivo storage vessels and a large range of sensor applications. We present our results on the investigation of un-etched ion tracks in polymers, such as polycarbonate and polyimide. The ion tracks were created by swift heavy ion irradiation at the Universal Linear Accelerator at GSI. We have previously demonstrated that synchrotron-based small angle x-ray scattering (SAXS) allows the detailed characterization of ion tracks in a number of materials [1]. Here, SAXS reveals a diameter of 5 nm for tracks in polycarbonate films. Complementary small angle neutron scattering (SANS) measurements reveal a similar value, yet the combination of both techniques allows an element-specific investigation in the change in density as a consequence of the ion irradiation. A significant hydrogen deficiency in the irradiation polymer areas is revealed that is independently confirmed by infrared spectroscopy (FTIR) on the same specimens. Furthermore, the effect of energy deposition and irradiation fluence was studied systematically, both displaying a significant influence on the resulting track size. The stability of tracks was investigated by thermal annealing: For temperatures up to 200ºC, the damage region was observed to recover gradually and a decreases in the difference in density to the undamaged region was measured. However, this process is accompanied by an increase in the track diameter, contrary to our previous results on tracks in inorganic materials, where the diameter displays a shrinkage. This suggests a fundamental different recovery mechanism for this class of materials. [1] P. Kluth et al., Phys. Rev. Lett. 101 (2011) 175503.

Unlike beta- and gamma-rays irradiations that lead to quite homogeneous energy deposition, Swift Heavy Ions (SHI) induce an heterogeneous energy deposition at the nanoscale level. Due to their high LET and because SHI deposit their energy close to the ion path, in a track core of a few nanometers, the local dose nearby these track cores is huge; in between, the dose is very low. A great number of detailed studies were performed under inert environment to assess the influence of the high ionization and excitation densities induced by SHI on polymer ageing. It was shown that, the huge amount of energy deposited locally by SHI induces specific damage processes, which involve complex molecular rearrangements and collective atom motions. Contrary to what has been done under inert environment for assessing the specificity of SHI on polymers, only few detailed studies have been undertaken under oxidative environments. Thus, the aim of the present work is to understand how high ionization/excitation densities induced by SHI impact the mechanisms underlying polymer degradation in presence of oxygen. Polymers submitted to ionising radiations are modified by the creation of macromolecular defects such as unsaturated bonds, chain scissions and crosslinks, or oxidative defects in presence of oxygen. The counterpart of these macromolecular defects is gas emission. We have examined both processes. In the course of the present work, we have studied the influence of the LET, the dose and the dose rate on different polymers. Additionally, we have considered the influence of the polymer chemical structure on its oxidative ageing, particularly as a function of the LET.

In this work, the influence of spatial confinement in one dimension on the chemical effects induced by 2.2 GeV Bi and 2 MeV H ions in ultrathin PMMA films was investigated, by quantifying bond breaking rates as a function of the thickness h of the polymer layers (2<h<200 nm). Our data indicate that for both beams damage cross-sections for carbon-oxygen bonds, do not show substantial difference down to the smallest thickness accessible to XPS analysis (h~5 nm). The damage cross-sections estimated are ~1.5x10-13 cm2 (for O-C-O bonds) and ~2.3x10-13 cm2 (for C=O bonds) for the Bi irradiation, whilst for proton irradiation the values are ~2.7x10-16 cm2 and ~4.4x10-16 cm2, for O-C-O and C=O bonds, respectively. Variation of the cross-sections among samples of different thicknesses were within error bars. Films thinner than ~5 nm become difficult to analyse, because of the non-negligible signal of the omnipresent carbon on the substrate and because of beam-induced surface roughening and sputtering. The absence of a decrease in the damage cross section in ultrathin layers is surprising, considering the high velocity of the ions and the long range of the emitted secondary electrons, which may escape the sensitive volume before thermalization and thus lowering the effective dose. Our observations are also in contrast to recent findings of a strong thickness dependence of cratering and mass transport induced by swift heavy ions in ultrathin polymer layers, indicating that at least the chemistry probed by XPS is related to short-range events close to the track core, while in sputtering, long-range, cooperative effects along the track are of greater importance.

AlN, GaN and InN were irradiated at room temperature with monatomic Swift Heavy Ions and high energy fullerenes. Despite a common crystallographic structure, these compounds show much contrasted response towards the electronic energy deposition. Transmission Electron Microscopy in both plane-view and cross-sectional modes is used to characterize ion tracks. AlN shows a remarkable resistance towards track formation. InN is the most sensitive and shows partial decomposition inside the tracks, likely into N2 and In metallic clusters. In GaN tracks are observed, containing amorphous pockets, but high fluence irradiation does not give an amorphous layer because of recrystallization induced by track overlapping. In AlN, below the electronic stopping power threshold for tracks formation, optical absorption was studied in-situ at 15 K. Point defects inducing an absorption band at 4.7 eV are created. Detailed analysis of the influence of both electronic and nuclear stopping powers indicates a synergy between electronic excitations and elastic collisions. For the heaviest projectiles, the enhancement of the color center creation yield amounts to two orders of magnitude due to the electronic energy loss. An enhancement by electronic stopping power of point defect creation or of point defect mobility is also evidenced by TEM observations.

We exposed nitrogen-implanted diamonds to beams of swift heavy ions (1 GeV, 4MeV/u) and find that these irradiations lead directly to the formation of nitrogen vacancy (NV) centers, without thermal annealing. We compare the photoluminescence intensities of swift heavy ion activated NV centers to those formed by irradiation with low-energy electrons and by thermal annealing. NV yields from irradiations with swift heavy ions are 0.1 of yields from low energy electrons and 0.02 of yields from thermal annealing. We discuss possible mechanisms of NV center formation by swift heavy ions such as electronic excitations and thermal spikes. While forming NV centers with low efficiency, swift heavy ions could enable the formation of three dimensional NV assemblies over relatively large distances of tens of micrometers. Further, our results show that NV center formation is a local probe of (partial) lattice damage relaxation by electronic excitations in diamond. ACKNOWLEDGMENTS This work was supported by the U.S. Department of Energy under Contract No. DE-AC02—05CH11231 and by the Laboratory Directed Research and Development Program. Ref.: [1] J. Schwartz, et al., J. Appl. Phys. 116, 214107 (2014)

Swift heavy ion (SHI) irradiation leads to formation of narrow ion tracks in many materials, can be used in modifying nanomaterials, and in some materials with existing damage induces defect recovery. Molecular Dynamics (MD) simulations, which include the energy deposition from electronic stopping following the inelastic thermal spike calculation input, can show the time evolution of these processes, and reveal how differences in solid – liquid phase transitions and recrystallization lead to very different behavior in damage formation and recovery in different insulator and semiconductor materials, subjected to similar initial electronic excitation. In silicon carbide (3C-SiC), MD simulations complement our recent ion-beam experiments and clearly show that the irradiation-induced defect recovery process in SiC is active from swift heavy ions to low values of electronic stopping, in a regime where electronic stopping is often considered negligible. In other materials like zircon, an opposite co-operative effect of nuclear and electronic stopping is observed. The competitive processes of damage production and defect recovery are relevant for understanding radiation damage production for many materials in nuclear energy applications and for investigating radiation damage in materials using ion irradiation methods. In a-Ge, a-Si and their alloys, local melting around the swift heavy ion path leads to formation of nanometer scale voids and/or ion tracks, the latter observable in these amorphous materials only indirectly as localized density changes in SAXS experiments. MD simulations explain the formation of the density variations and the shape of voids, due to the volume contraction associated with the molten phase and the following radially progressing expansion of the resolidifying ion track.

This contribution discusses recent results on the recrystallization effect [1,2] induced by swift heavy ions (SHI) in pre-damaged silicon carbide. The recrystallization kinetics was followed by using increasing SHI fluences and by starting from different levels of initial damage within the SiC samples. The quantitative analysis of these data shows that the recrystallization rate depends drastically on the local amount of crystalline material: it is nil in fully amorphous regions and becomes more significant with increasing amount of crystalline material. For example, in samples initially nearly half-disordered, the recrystallization rate per incident ion is found to be 3 orders of magnitude higher than what it is observed with the well-known IBIEC process using low energy ions. This high rate can therefore not be accounted for by the existing IBIEC models. A comprehensive quantitative analysis of all the experimental results indicates that the SHI induced high recrystallization rate can only be explained by a mechanism based on the melting of the amorphous zones through a thermal spike process followed by an epitaxial recrystallization initiated from the neighboring crystalline regions if the size of the latter exceeds a certain critical value. Finally, this quantitative analysis also reveals that the molecular dynamic (MD) calculations [3,4] supposed to reproduce the recrystallization phenomenon are actually far from being realistic since they lead to a recrystallization rate per incident ion which is about 40 times higher than the experimental value [5]. [1] A. Benyagoub, A. Audren, L. Thomé, F. Garrido, Appl. Phys. Lett. 89, 241914 (2006). [2] A. Benyagoub, A. Audren, J. Appl. Phys. 106, 083516 (2009). [3] A. Debelle, M. Backman, L. Thomé, W. J. Weber, M. Toulemonde, S. Mylonas, A. Boulle, O. H. Pakarinen, N. Juslin, F. Djurabekova, K. Nordlund, F. Garrido, D. Chaussende, Phys. Rev. B 86, 100102(R) (2012). [4] M. Backman, M. Toulemonde, O. H. Pakarinen, N. Juslin, F. Djurabekova, K. Nordlund, A. Debelle, W. J. Weber, Comput. Mater. Sci. 67, 261 (2013). [5] A. Benyagoub, arXiv:1402.3200 (2014).

Biological effects induced by ionization radiations is a complex function of many parameters. Some are related to the type of irradiated cells and their environment. Some others are related to the irradiation characteristics. While considering the specific case of swift ions, not only the dose of irradiation but also the ion charge, the ion energy, the irradiation temporal and spatial substructures need to be considered. In 2008, at the shim conference [1], we presented the two track-structure models dedicated to the prediction of cell killing induced by ions and pointed out some of the conclusions we drew from a detailed analysis of these models. Based on these conclusions, we developed an alternative model: nanoxTM (NAdosimetry and Oxidative stress). The nanoxTM model takes as input dosimetry quantities at multi-scale, starting from nanoscale, but also the production of radicals induced by water radiolysis. The model will be presented along with first results. [1] M. Beuve, A. Colliaux, D. Dabli, D. Dauvergne, B. Gervais, G. Montarou, E. Testa, Statistical effects of dose deposition in track-structure modelling of radiobiology efficiency, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 267, Issue 6, March 2009, Pages 983-988

Heavy ions possess much higher linear energy transfer and produce severe ionizing damage to DNA in biological sample or PN junction in microelectronics along the ion trajectory. Heavy ion microbeam and high energy microbeam is attracting more and more interests because of the clinical spread of high energy particle cancer therapy using protons and carbon beams and care of space radiation effect, especially from cosmic heavy ion rays, in spacecraft and astronauts. Such a microbeam is a powerful tool to study the spatial radiation response or the local radiation effect both in materials and biological samples to simulate the space radiation at ground, and the high energy and long penetration of hundred MeV/u beam may also expand the application of the above mentioned microbeam application to large samples. This work presents the development of the interdisciplinary experimental system at the high energy microbeam of IMP, and then shows the study of protein dynamics of DNA repair after single ion irradiations.

Energetic charged particles (HZE) are encountered in spaceflight as part of the galactic cosmic rays, where they pose a health risk to astronauts. However their destructive potential can be used in heavy ion tumour therapy. The deposition of energy of these HZE particles occurs mostly along the trajectory of the particle itself, but depending on its energy, there is some probability for energy deposition relatively far from the nominal trajectory, due to long-ranged delta rays. These delta rays are considered to induce non correlated DNA damage similar to low-linear energy transfer (LET) radiation (like X-rays), whereas the dense ionizing track of HZE particles is assumed to produce more complex and clustered DNA damage, which is slowly repaired or is even irreparable. To study the spatiotemporal protein dynamics during charged particle irradiation, a remote controlled microscope was established at the accelerator facility of GSI. The system enables the acquisition of high-resolution fluorescence images of living cells during ion irradiation. The microscope allows studying early radiation effects without the time lag of minutes presently conditional on limitations of access to the irradiation devices. GFP-tagged repair proteins like NBS1 were used for the spatio-temporal characterization of DNA damage in respect to the particle trajectory in cell nuclei. To compare high LET (ions) and sparsely ionizing radiation (X-rays) induced DNA damage, the microscope can alternatively be equipped with a 35 kV x-ray tube operated at high dose rate (40 Gy/min). Time-lapse series of repair proteins like XRCC1 proved accumulations within seconds along the ion tracks indicating a fast recognition of DNA damage in combination with a quite stable location of damage processing. In the study presented here, we used a spectrum of different particles over a broad range of LETs in addition to x-rays to address the dynamics of the early DNA damage response in regards to the damage density in living cells. The detailed analysis of NBS1-GFP revealed differences in the recruitment kinetics and retention at damage sites in connection to the LET and radial track structure of the particles.

Ions offer a more advantageous dose distribution than photons for external beam radiotherapy, due to their invers dose deposition and, in particular, a characteristic dose maximum at their end of range (Bragg peak). Therefore, a more conformal therapeutic dose can be applied to the tumor while sparing the surrounding healthy tissue, even if organs at risk are in striking distance. This makes, however, a precise positioning of the Bragg peak inside the tumor volume a challenging demand. Range verification in ion beam therapy relies to date on nuclear imaging techniques which require complex and costly detector systems, and none has still reached clinical maturity. In this project, we make use of the pressure pulse and related acoustic wave induced by ions stopping in tissue (ionoacoustics) to measure the ion range with ultrasound methods. This technique could offer a simple and more direct possibility to correlate, in-vivo and in real-time, the conventional ultrasound echo of the tumor region with the position signal of the ion Bragg peak. The idea of using acoustic signals in water for detection of high energy particles, in particular of neutrinos, has long been proposed and ultrasound signals have first been measured in 1979 with energetic protons. The first demonstration of an acoustic pulse generated in a patient during radiation treatment with a proton beam was performed in 1995, but the accuracy needed in radiation therapy could never been reached. However, to-day’s more advanced irradiation schemes with active beam scanning and dose delivery with higher pulse intensities are in favor of a more accurate ionoacoustic approach. This presentation will address our experimental and simulation work investigating the potential of the ionoacoustic method to enable sub-mm imaging of the Bragg peak. The proof-of-principle experiments were performed at the Tandem accelerator of the LMU and TU Munich, using a 20 MeV proton beam and different focused US transducers.

Proton accelerators driven with ultra-intense short pulse lasers provide proton beams with extraordinary characteristics. The extreme acceleration fields (typically exceeding TV/m) allow very compact accelerators (acceleration lengths on the micrometer scale) to reach energies of 10s of MeV with up to 2 1013 particles per bunch and excellent spatial beam quality (transverse emittance). The short duration of the acceleration fields excited by the laser provides the basis for proton bunches with ultrashort pulse duration. Such short proton pulses raise the possibility of investigating the temporal dynamics of the fundamental interaction of protons and ions with matter directly. Here we report on the temporal characterisation of few picosecond (ps, 10-12 s) laser driven proton bunches for this purpose. Prompt transient opacity for optical probe radiation from protons stopping in high purity fused silica (a-SiO2) provides the basis for single-shot characterisation of laser-accelerated proton bunches. The rapid ionisation dynamics allow the measurement of proton pulse durations as short as 3.5 ± 0.7 ps in a 0.4 ± 0.05 MeV bandwidth. This corresponds to an ultra-low longitudinal emittance of (1.75 ± 0.25) × 10-6 eV s and is in excellent agreement with numerical modelling. These observations pave the way to generating seed pulses for proton-driven wakefield acceleration of electrons in advanced lepton collider concepts.

In the last years, ion-shaping technique has been proposed as an innovative and powerful tool to manipulate matter at the nanometer scale. Deformation can be indirectly induced by embedding metallic NPs into an ion-deformable amorphous host matrix. With this technique, it is possible to transform nanospheres into nanorods, nanowires, facetted nanoparticles, or other original shapes. The aspect ratio and spatial orientation of these NPs can be tuned by varying the irradiation conditions (ion, ion-energy, irradiation angle, fluence). To understand the mechanisms of deformation, the evolution of the temperature profile during the ion impact within the nanoparticle is simulated by implementing the thermal-spike model for three-dimensional anisotropic and composite media. By this way, a straight correlation is found between the fraction of the nanoparticle that is molten (vaporized) and the deformation path followed by the nanoparticles during the irradiation. This allows to relate the initial nanoparticle to its final morphology, in order to generalize the ion-beam shaping process for all the nanoparticle shapes and dimensions. Besides the fundamental aspects related to the ion-matter interaction, ion-shaping can also be used to give new insights into the plasmonic properties of metallic nanoparticles. Here, Electron Energy Loss Spectroscopy (EELS) is used to study Localized Surface Plasmon Resonances (LPSR) in ion-shaped metallic nanoparticles with a nanometer-scale spatial resolution. LSPR are generated through electron excitation is a Scanning Transmission Electron Microscope (STEM), equipped with a High Angle Annular Dark Field (HAADF) detector. These experimental results are simulated using a specifically developed Auxiliary Differential Equations-Finite Difference Time Domain (ADE-FTDT) code and the Metallic NanoParticles Boundary Element Method (MNPBEM) code.

Nanometer-sized noble metallic particles embedded in dielectric matrices have attracted a great deal of attention. They are used in many applications mostly due to surface plasmon resonance which has dependence on their size and shape. Therefore, efforts have been made to vary their size and shape by various methods during or after fabrication. Swift heavy ion irradiation has been found to be very useful in this objective [1-3]. It has been shown that the size and shape of nanoparticles can be varied depending on the particle size and the expected size of the ion tracks in the matrix [4]. In particular, swift heavy ion irradiation has been recommended as size filter to embedded noble nanoparticles [5]. Our group has proposed a model based on inter-particle separation to explain the swift heavy ion induced modification in the size of embedded nanoparticles smaller than the ion track size in matrix [4]. In the present work, we have tested this hypothesis by atomistic simulation and tried to gain a better understanding of nanoparticle size modification pathway. The size of nano-particles and inter-particles separation, kept in the simulation, were taken from the experimental work [4]. Effect of ion irradiation was mimicked by considering local short-time heating effects. The results agree with the experimental results of growth or reduction of embedded nanoparticles depending on the inter-particle separation. References: [1] Y.K. Mishra, D. Kabiraj, D.K. Avasthi, J.C. Pivin, Radiat. Eff. Defects Solids, 162, 207 (2007). [2] Y. K. Mishra, D. K. Avasthi, P. K. Kulriya, F. Singh, D. Kabiraj, A. Tripathi, J. C. Pivin, I. S. Bayer and A. Biswas, 90, 073110 (2007). [3] F. Singh, S. Mohapatra, J.P. Stolquert, D.K. Avasthi, J.C. Pivin, Nucl. Instr. and Meth. B, 267, 936 (2009). [4] D.K. Avasthi, Y.K. Mishra, F. Singh, J.P. Stoquert, Nucl. Instr. and Meth. B, 268, 3027 (2010). [5] Y. Yang, C. Zhang, Y. Song, J. Gou, L. Zhang, Y. Meng, H. Zhang, Y. Ma, Nucl. Instr. and Meth. B, 308, 24 (2013).

Physical processes involved in the interaction of ion beams in Warm Dense Matter (WDM) (i.e. 1 - 100 eV, 0.01-100 g/cc) is fundamental to the understanding of condensed matter, solid-state physics, fusion sciences, and astrophysical phenomena. In particular, in the WDM regime the charge equilibrium and stopping power of ions differs significantly from that of both cold matter and ideal plasma due to free electron contributions, plasma correlation effects and electron degeneracy. Furthermore, experimental data is extremely scarce in this regime; the reason being that the creation a WDM state with a temporal duration consistent with the particles used to probe it has been extremely difficult to achieve experimentally. For the past couple of years, we have been developing an experimental platform using short pulse lasers that can produced relatively short bunches of protons (picosecond time scale) to study plasmas in the WDM regime. Earlier this year, using the Titan Laser at JLF, we used the CPA laser to create two identical proton beams in a gas jet. One was used as a reference, and the other beam was used to perform the stopping power measurement in a gas plasma that was heated by the long pulse beam. These measurements will allow for a first evaluation of semiempirical formulas that are being used to predict the stopping power of ions in numerical codes that are often used in ICF and astrophysics. The development of this short-pulse laser platform thus shows great promise to push further the investigation of ion interactions in the experimentally challenging conditions of WDM.

The nature and intensity of ion-surface interactions are intimately connected to projectile energy deposition in the target and therefore depend both on the kinetic and the potential energies [1]. The energy losses of swift heavy ions (SHI, MeV to GeV) induce along the ion path intense electronic excitations in a small volume which spawn formation of surface modifications and latent tracks in depth. Beside it, highly charged ions (HCI) carry several tens of keV of potential energy which is delivered into only few atomic layers of the surface, resulting in many different phenomena that are significantly dependent on the potential energy deposition. Quite recently a coherent synergy of nuclear and electronic energy losses is suggested in ion-irradiation processes from the nuclear to the electronic energy regime [2] and the model developed for track formation was extended to explain the nuclear effect. In our recent work, a complementary study [1] has shown an additive effect between depositions of kinetic energy and potential energy in a medium energy range for surface nanostructure formation on CaF2. Based on suggestion of Aumayr et al. [3] and on knowledge of track formation at high energy, including experiments and model description [4], we will show the results of surface modifications on various insulating material surfaces (i.e CaF2 Eg=12eV (done in [1]), c-SiO2 Eg= 9eV, Al2O3 Eg=8eV and MgO Eg=7.8eV) induced by highly charged ions and swift heavy ions in a medium energy range. [1] Y.Y. Wang et al, Sci. Reps. 4(2014)5742 [2] M.Toulemonde et al, PRB 83(2011)054106 [3] F. Aumayr et al, J. Phys. Cond. Matt. 23(2011)393001 [4] A. Meftah et al, NIMB 237(2005)563

In this study, CeO2 and NiO were irradiated with Au ions in the energy range of 200-340 MeV at oblique incidence. Observation of as-irradiated samples by transmission electron microscope (TEM) shows that hillocks are created not only at the wide faces but also at the crack faces of thin samples. Since the hillocks created at the crack faces can be imaged by TEM, their shape and crystallographic features can be revealed by TEM. From the images of hillocks created at the crack faces, many of the hillocks are found to be spherical for ion-irradiated CeO2. For ion-irradiated NiO, atomic-scale steps are found to be created at the top surface of the hillocks. We present an experimental evidence that hillocks created for both oxides irradiated with swift heavy ions have a crystal structure whose lattice spacing and orientation coincide with those of the matrix. The mechanism of hillocks formation will be discussed based on the present results, and the advantages of the novel observation technique used in the present study will be also discussed.

Y-Ti oxides and Me23C6 precipitates are typical representatives of nanoparticle population in ferritic oxide dispersion strengthened (ODS) steels. Their stability during dense ionization in the so-called swift heavy ion regime has received considerable attention in recent years because the change in nanoparticle morphology should inevitably affect the mechanical properties of the first few subsurface microns of cladding material that is in contact with fissionable fuel and exposed to fission fragments. In this report we present and discuss the results of a TEM study of structural changes induced by krypton and xenon ions of fission fragment energy (1.2 MeV/nucleon) in Y2Ti2O7 and Me23C6 nanoparticles in EP450 ODS steel. It was found that swift heavy ion irradiation leads to formation of amorphous latent tracks in both materials. The electronic stopping power threshold for track formation in pyrochlore nanoparticles lies in the range 7.4– 9.7 keV/nm and the mean track diameter varies linearly with the electronic energy loss.

Research on materials under coupled extreme conditions including pressure, temperature, and irradiation has become a new and vibrant area of investigation [1]. Incorporation of relativistic ion beams, in particular, has proven effective for synthesis and stabilization of novel phases far from thermodynamic equilibrium [2]. The technique couples static compression and high-density energy deposition via the bombardment of pressurized samples by relativistic heavy ions that are injected into a diamond-anvil cell [3]. Most recently, we applied this technique to amorphous germanium dioxide (GeO2). Germanium dioxide boasts a diverse array of polymorphs. One hexagonal polymorph, disordered niccolite (d-NiAs-type) GeO2, is notably absent in nature. This d-NiAs-type structure forms exclusively from aperiodic starting materials during shockwave experiments, and static compression experiments in a limited temperature range (1000 – 1300 K) at pressures above 6 GPa [4]. Prior attempts to quench the high-pressure phase were unsuccessful —noting a gradual transformation to the stishovite structure within hours. Here, we report on the crystallization and permanent stabilization of the d-NiAs-type structure of GeO2 formed by in situ irradiation of GeO2 glass with 6 GeV 209Bi ions at 45 GPa in the absence of external heating. Synchrotron x-ray structural refinement of the quenched material suggests that the phase is stabilized by ion-induced cation vacancies that randomly occupy half of the octahedral sites. References: [1] R.J. Hemley, G.W. Crabtree & M.V. Buchanan, Physics Today 62, 32-37 (2009) [2] M. Lang et al., Nature Materials 8, 793-797 (2009) [3] M. Lang et al., J. Synchrotron Rad. 16, 773–777 (2009) [4] V.B. Prakapenka et al., J. of Phys. and Chem. of Solids 65, 1537-1545 (2004)

In the relatively shielded environments provided by interstellar dense clouds in our Galaxy, infrared astronomical observations have early revealed the presence of low temperature (10-100 K) ice mantles covering tiny grain “cores” composed of more refractory material. These ices are of specific interest because they constitute an interface between a solid phase under complex evolution triggered by energetic processes and surface reactions, with the rich chemistry taking place in the gas phase. The interstellar ice mantles present in these environments are immersed in a flux of cosmic ray particles [1-3] that produces new species via radiolysis processes, but first affects their structure which may change and then induces desorption of molecules and radicals from these grains [4-6]. Theses cosmic rays can be simulated in the laboratory for a better understanding of astrophysical processes. The high-energy cosmic ray component (just below or above 100 MeV/u) was so far only scarcely simulated experimentally. Nevertheless, there is a clear need to study the interaction of high energy cosmic rays with ices, since the energy deposited on dust grains and ice mantles is expected to be important compared to protons and concomitant with UV photons. In particular, the physical state of the ice is extremely important in many respects for astrophysicists, to allow in particular surface physicist to perform experiments on realistic surfaces for a better understanding of interstellar chemistry. This talk will be dedicated to describe the evolution, in an astrophysical context and based on laboratory experiments, of the ice’s physical state (amorphous, crystalline, metastable), including sputtering, resulting from the interactions with swift ions and photons. [1] Shen et al. 2004, A&A,415, 203; [2] de Nolfo et al. 2006, Adv. Space Res., 38, 1558; [3] George et al. 2009, ApJ, 698, 1666 ; [4] Fama et al. 2010, Icarus, 207, 314; [5] Dartois et al. 2013, A&A 557, A97; [6] Mejía et al. 2015,Icarus, 250, 222.

We report on a new time-of-flight (TOF) spectrometer designed to investigate sputtering phenomena induced by swift heavy ions in the electronic stopping regime. In this experiment, particular emphasis is put on the detection of secondary ions along with their emitted neutral counterparts in order to examine the ionization efficiency of the sputtered material. For the detection of neutral species, the system is equipped with a pulsed VUV laser for post-ionization of sputtered neutral atoms and molecules via single photon ionization at a wavelength of 157 nm (corresponding to 7.9 eV photon energy. For alignment purposes and in order to facilitate comparison to nuclear sputtering conditions, the system also includes a 5-keV Ar+ ion beam directed to the same sample area. The instrument has been added to the GSI M-branch beam line and was tested with 4.8 MeV/u Au26+ ions impinging onto various samples including metals, salts and organic films. It is found that secondary ion and neutral spectra obtained under both bombardment conditions can be acquired in an interleaved manner throughout a single accelerator pulse, thus making efficient use of valuable beam time. In addition, the keV ion beam can be intermittently switched to dc mode between subsequent accelerator pulses in order to ensure reproducible surface conditions by dynamical sputter cleaning. For the case of a clean metal surface, comparison of secondary ion and neutral signals obtained under otherwise identical instrumental conditions reveal that the ionization probability of atoms emitted under electronic and nuclear sputtering conditions is similar.

Amorphous silicon nitride films (thickness 30 nm) deposited on Si(001) were irradiated with 30 – 1080 keV C₆₀ and 100 MeV Xe ions to fluences ranging from 2.5 × 10¹¹ to 1 × 10¹⁴ ions/cm². The composition depth profiles of the irradiated samples were measured using high-resolution Rutherford backscattering spectrometry. Both silicon and nitrogen signals in the film decrease with fluence. The sputtering yields were estimated from the observed RBS spectra. The observed total sputtering yield of C₆₀ increases from 1200 to 4600 when the energy increases from 30 to 1080 keV. The corresponding sputtering yields estimated using the SRIM code are less than 100, suggesting that the electronic sputtering is responsible for the observed large sputtering yields. On the other hand, the observed sputtering yield of 100 MeV Xe is about 500. Considering the fact that the electronic stopping power of 100 MeV Xe ion (16.6 keV/nm) is larger than those of 30 – 1080 keV C₆₀ ions (2 – 10 keV/nm), the large sputtering yields of C₆₀ ions are ascribed to the synergy effect between the electronic and collisional sputtering. In order to estimate such a synergy effect, calculations of the sputtering yield are now in progress using the inelastic thermal spike model taking account of the nuclear stopping power [1]. The result of the calculation will be presented at the conference. [1] M. Toulemonde, W.J. Weber, G. Li, V. Shutthanandan, P. Kluth, T. Yang, Y. Wang and Y. Zhang, Phys. Rev. B 83 (2011) 054106.

Complex organic molecules are observed in many astrophysical objects, but little is known about their formation mechanism and survivability. In molecular clouds, atoms and molecules condense on dust particles leading to formation of icy mantles. Astrophysical ices contain mainly H2O, while CO, CO2, NH3, and CH3OH are also commonly observed. These ices are exposed to energetic processing by ions, photons and electrons, and/or thermal processes that trigger the chemical evolution of the ice. Laboratory simulations on interstellar ices and molecular clusters are therefore of paramount importance for understanding the origin of complex organic molecules (possibly relevant to the origin of life). Studying in-situ the chemical evolution of ices and of remaining refractory organic residues (after slow heating-up) provides relevant hints on the fundamental physical and chemical steps associated with the increase of the molecular complexity in space. Several experiments show that the basic building blocks of organic matter can be formed by interaction of UV photons, electrons and keV-MeV light ions with ices. The aim of the present work is to mimic the reactivity in ices and molecular clusters triggered by heavier ions, also being present in space. On the one hand, we will focus on the physical chemistry induced by heavy-ion cosmic rays inside ammonia-containing ices (e.g. H2O:NH3:CO) irradiated by Ni ions. The infrared spectra of the irradiated ice samples exhibit bands of several new species including HNCO, N2O, OCN−, and NH4+. After IR measurements the irradiated samples were slowly warmed up to room temperature. This IR spectrum contains bands that can be tentatively assigned to vibration modes of zwitterionic glycine and to hexamethylenetetramine. Moreover, we need to know the probability that such complex organic molecules survive when exposed to radiation. Therefore, we have also performed irradiations of adenine films with MeV ions. On the other hand, it is believed that PAHs are omnipresent in the interstellar medium. We will also present very recent results on ion-induced reactivity in pyrene clusters and radiolysis of pyrene films.

High density electronic excitation caused by fission fragments (FFs) in nuclear fuels and transmission targets is known to induce of ion tracks along the penetration path of FFs. Understanding of the structure of ion tracks together with the overlapping effects is one of the essentials for the development and assessment of the fuel/target materials under the extreme radiation condition. This paper reports the structure and accumulation process of ion tracks in ceria through a variety of transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) techniques. Ion tracks in CeO2 have been shown to retain the fluorite structure. Bright-field TEM and high-angle annular dark-field (HAADF) and annular bright-field (ABF) STEM techniques showed that the core region of ion tracks is 3-4 nm in diameter [1,2], and that the atomic density inside the ion tracks is decreased for about 10% [3]. Furthermore, ABF-STEM observation detected the preferential disorder of O-anion sublattice at the core region of the ion track [3]. On the other hand, analysis of the accumulation of ion tracks suggested the existence of an influence region, in which the formation and recovery of ion tracks are balanced [1]. The significantly large size of influence region (17 nm in diameter) than observable size is discussed that the core damage region detected by TEM and STEM is a vacancy-rich region formed after the recovery process of thermal spike [4]. Interstitial ions are considered to be generated during the recovery process within a rather wide region, to result in the development of dislocation structure at high fluence irradiation condition. It is also presented in this paper that the size of Fresnel contrast of ion tracks with bright-field TEM strongly depends on the defocused condition. [1] K. Yasuda, et al., Nucl. Instr. Meth. B 314 (2013) 185 [2] K. Yasuda, et al., Proc. on 11th Int. Topical Meetings on Nuclear Applications of Accelerators (2013) 7. [3] S. Takaki et al., Nucl. Instr. Meth. B, 326(2014) 140. [4] S. Takaki et al., Prog. Nucl. Energy (2014) in press.

Small angle X-ray scattering (SAXS) provides an interesting tool to study the structure of etched and un-etched ion tracks. It is non-destructive and can yield high precision measurements of the track radii in bulk amorphous and crystalline materials. Short acquisition times associated with the high photon flux at 3rd generation synchrotron devices facilitate in situ studies to determine the annealing kinetics of ion tracks as well as the use of diamond anvil cells to investigate track stability under high pressure conditions. Monte Carlo calculations enable advanced SAXS data analysis using complex track shapes. This presentation will give an overview of our recent advances in characterising ion tracks using SAXS and outline potential future directions. Examples include: In situ annealing experiments of ion tracks in quartz to study a complex elastic behaviour of the tracks [1] as well as their annealing kinetics; the composition dependent annealing behaviour of tracks in natural apatite; etching experiments in apatite which reveal hexagonally shaped etch pits depending on track orientation and apatite composition; ion track formation at elevated temperatures in apatite and quartz showing an increase in the track radii by approximately 1 Å/100°C as a consequence of an increased local temperature leading to a larger melting radius in the thermal spike [2]; the influence of pressure on the formation, stability and annealing behaviour of ion tracks. Increasing pressure during formation leads to increased track radii, while track recovery appears to be enhanced at elevated pressures. Experimental results were complemented by molecular dynamics simulations. [1] B. Afra et al., Phys. Rev B 90 (2014) 224108 [2] D. Schauries et al., J. Appl. Cryst. 46 (2013) 1558

Defects in oxide materials created by irradiation are often revealed by optical absorption for the formation of colour centres and by transmission electron microscopy (TEM) for the individual latent track and microstructure evolution observations. The characterizations by X-Ray diffraction of irradiated materials were lesser used but are since few years under investigation going with the development of versatile laboratory diffractometers allowing good resolution and grazing geometry (GIXRD) required to probe the upper irradiated part of samples. In this work a detailed study on the structural modifications of Al2O3 compound induced by swift heavy ion irradiation is presented by an original combination of the three techniques, previously mentioned, in-situ GIXRD, TEM and in-situ UV-Vis absorption. The irradiation experiments have been performed at IRRSUD beamline of GANIL where the energy range, i.e. 0.3-1 MeV/A, implies a mean projected range in solid matter around only a few micrometers and a decrease with depth of the electronic stopping power (Se). Depth profile by GIXRD is thus topical to get structural parameters at different Se values. In the communication the study of alpha-Al2O3 polycrystals and single crystals irradiated by 92 MeV Xe and 74 MeV Kr will be shown. Contributions from point defects and extended defects induced by irradiation to structural modifications will be discussed. An amorphization of the material is observed and its kinetics of ion track overlapping will be shown. This amorphization is associated in the crystalline part to tensile strain, unit cell swelling, microstrain, grain subdivision and a variable damaging sensitivity of the anionic and cationic sublattices. Our results are consistent with the previous reports found in literature and are in agreement with the given Se threshold for amorphization. These results will be fully described and illustrated during the communication.

The localized nature of f-electrons results in systematic variation in the structures and electronic configurations accessible to oxides across the lanthanide and actinide series, with some exceptions due to partial f-electron itinerancy in the light actinides. To study the influence of the resulting variation in f-block oxide phase space on the response of these materials to highly-ionizing radiation, various lanthanide and actinide oxides were irradiated with swift heavy ions possessing energies ranging from 167 MeV to 2.2 GeV. Modifications to the materials were characterized using x-ray diffraction, x-ray absorption spectroscopy, and Raman spectroscopy. Sesquioxides (A2O3), with the bixbyite structure and minimal redox activity, exhibited radiation-induced phase transformations to high temperature polymorphs, with the final phase and the transformation rate showing dependence on the cation ionic radius. In contrast, fluorite-structured dioxides (AO2) retained their initial structure, but underwent partial cation valence reduction to the trivalent state, causing unit cell expansion and microstrain commensurate with the propensity of their cations to accommodate these valence changes. Finally, uranium trioxide (UO3) showed extensive cation reduction to the tetravalent state, decomposing to a UO2+x phase with the fluorite structure. From these results, the effects of swift heavy ion irradiation on the f-block oxides can be understood in terms of coupled modifications to their atomic and electronic structures. These effects are constrained by the stabilities of structures and electronic configurations, governed by variations in ionic radius and f-electron itinerancy characteristic of the f-block oxides.

High energy proton microscopy (HEPM) or radiography is a novel technique for probing the interior of dense objects in static or dynamic experiments by mono-energetic beams of GeV-energy protons. A special system of magnetic lenses is employed for imaging and aberrations correction. Using this technique, one can measure the areal density distribution of a thick sample with sub-percent accuracy, micrometer-scale spatial and nanosecond-scale temporal resolutions. HEPM is of considerable interest for materials research, plasma physics, biophysics and medicine. The future PRIOR (Proton Microscope for FAIR) facility will use 1 - 10 GeV intense proton beams and will allow for a significant step forward in spatial (~ 10-15 µm) and temporal (~ 5-10 ns) resolution. A PRIOR prototype has been constructed and successfully commissioned at GSI in 2014 using 3.5 - 4.5 GeV intense proton beams from the SIS-18 synchrotron. The status of the PRIOR project and the first results obtained in static and dynamic experiments with the PRIOR prototype are presented.

For decades we have been involved in the selective excitation of the heavy atomic ions from Ar to U in the x-ray energy domain making use of a thin single crystal. The swift ions accelerated to ~70 % of the speed of light using the heavy ion synchrotron facility are guided in the silicon single crystal, and excited by a temporally oscillating strong Coulomb field arising from the periodical atomic arrangement. When one of the frequencies corresponds to the transition energy of the ion, the oscillating field has a chance to resonantly excite the internal atomic states of the ion. This process is called “resonant coherent excitation” (RCE). Starting from the resonance by periodic field due to the arrays of the atomic strings in the crystal (2D-RCE) under the planar channeling condition, we developed the resonance technique by the periodical field by an array of the atomic planes (3D-RCE) under the non-channeling condition. Making use of the 3D-RCE, we have made a significant progress in the selective excitation of heavy atomic ions like Ar and Fe ions accompanying one or a few electrons. Control of magnetic substate population i.e., ion alignment has been achieved by selecting polarization of the periodic field. The use of double resonance technique offered a variety of population control and probing scheme in three-level configurations, that enabled observation of 1) quantum optical phenomena like dressed atoms even in the x-ray energy domain, 2) double excitation to make two K-shell holes in an heavy ion, and 3) sequential excitation to the higher electronic states. We also have succeeded in observing the 2s-2p transitions of Li-like U ions, which offers us a future possibility of the precision atomic spectroscopy.

Precise data on electronic stopping powers for heavy ions are of high interest in various fields of research. Since more than one decade a new technique, which uses a combination of time-of-flight and energy detectors to collect continuous dE/dx data over a wide range of energies in a single measurement [1], has been successfully applied in different experiments. However, for high ion masses and low energies, where dE/dx data are nowadays still scarce, ionization based energy detectors suffer from incomplete energy detection, resulting in pulse height defect and a relatively poor energy resolution. As calorimetric low temperature detectors (CLTD's) provide substantially better energy resolution and linearity (with the absence of any pulse height defect) for heavy ion detection [2], this type of energy detectors has the potential to increase sensitivity and accuracy for dE/dx measurements and to extend the accessible energy range towards lower energies. For that purpose a CLTD array has been used to replace the Si-detector in an established setup for dE/dx measurements at the K-130 cyclotron at the University of Jyväskylä, and to perform measurements with 0.05–1 MeV/u 131Xe-ions in carbon, nickel and gold absorbers [3]. In addition to the determination of new stopping power data for low energy heavy ions, the excellent energy resolution of CLTD's allowed to resolve unexpectedly strong channeling effects for thin polycrystalline absorbers in the transmission type energy loss measurement, and therefore also to obtain data for channeling energy loss of 0.1–0.5 MeV/u 131Xe ions in nickel and gold absorbers. This contribution will present the detector concept of CLTD's as well as the results of this recent application for stopping power measurements. References [1] W.H. Trzaska et al., Nucl. Instr. Meth. B (2002) 195, 147. [2] P. Egelhof and S. Kraft-Bermuth, Top. App. Phys. (2005) 99, 469. [3] A. Echler et al., J. Low Temp. Phys. (2014) 176, 5, 1033.

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 chemical damages during processing. Researches were initiated on ion beam fabrication of optical waveguides in tellurite glasses. Channel waveguides were written in Er: TeO2–WO3 glass through a special silicon mask using 1.5 MeV N+ irradiation. This method was improved by increasing N+ energy to 3.5 MeV to achieve confinement at the 1550 nm wavelength, too. An alternative method, direct writing of the channel waveguides in the tellurite glass using focussed beams of 6–11 MeV C3+ and C5+ and 5 and 10 MeV N3+, has also been developed. Channel waveguides were fabricated in undoped eulytine- (Bi4Ge3O12) and sillenite type (Bi12GeO20) bismuth germanate crystals using both a special silicon mask and a thick SU8 photoresist mask and 3.5 MeV N+ irradiation. By using even higher energy irradiation, 25 MeV C5+ at low doses, planar optical waveguides were fabricated in sillenite-type BGO crystal. Focussed ion beam (11 MeV C3+, 10 MeV N3+) irradiation was also used to fabricate transmission optical gratings in Pyrex and Er: TeO2–WO3 glasses, sillenite type BGO and LiNbO3 crystals. The waveguides were studied by phase contrast and interference microscopy and micro Raman spectroscopy. Guiding properties were checked by using m-line spectroscopy and the end fire method.

We are running a High Resolution Scanning Electron Microscope in the beam line of the UNILAC ion accelerator at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, which has recently been extended also with an EDX-system and two micro-manipulators. This instrument allows us to in-situ investigate the structural and compositional development of individual objects and structures in the um- and nm-range under swift heavy ion bombardment, from the very first ion impact up to high fluences of the order of several 10^15 / cm^2. The sample under investigation is irradiated in small fluence steps and in between SEM-images (and EDX-scans) of one and the same surface area are taken. The irradiation can be carried out at any incidence angle between 0 and 90 degree and also under stepwise or continuous azimuthal rotation of the sample. The micro-manipulator system allows us to perform additional analysis like electrical and mechanical characterization as well as substrate-free EDX at sub-um objects. We are now also able to irradiate almost free standing sub-um structures (pasted on a nanoscale tip or held in micro-tweezers). In this report an overview over this unique instrument and its capabilities and advantages will be given, illustrated by the results of our recent in-situ studies on ion induced modification of thin films (dewetting and self-organisation) and on shaping of sub-um objects with swift heavy ions (by taking advantage of ion sputtering, ion hammering and ion induced visco-elastic flow).