A theoretical approach is developed to describe the dominant features of process by which craters form on the copper, gold and solid argon surfaces under self impacts of high velocity cluster ions. It is showed that, in the shock wave conditions generated at the impact of cluster on the surface, the dynamical process begins when the shock reaches the target free surface inducing the formation of a rarefaction wave(release wave) which propagates inward into the compressed region. The rarefaction causes the shocked material to move toward the free surface and expand into a vacuum forming the crater. It is found that the size of cluster has a significant influence on the mechanism of crater formation. In addition to metals (Cu and Au) the proposed approach has been successfully extended to impact of argon clusters on solid argon substrate. The approach has been validated using molecular dynamics simulated data for copper, gold and argon available in the literature. All simulated crater volumes have been analytically reproduced with a good agreement on the basis of a hemispherical shape.

An analytical approach is proposed to investigate the mechanism of implantation of size selected clusters into graphite, in order to explain the origin of linear variation of measured penetration depth with momentum or energy of incident cluster. In agreement with experimental observations, the cluster experiences, during its penetration, a force which consists in a component proportional with cluster velocity and a constant component. Expressions of these forces were obtained in the frame work of this approach. Regardless of whether the cluster breaks down into single atoms on the surface or not, there is evidence for existence of a wave generated under impact of cluster on the surface. Under the assumption that the cluster does not break up at impact on the surface, the penetration depth depends on the cross-section between the cluster and the surface, the cluster velocity and the properties of graphite. When the cluster fragments upon the impact on the surface, the generated wave is followed by a collective motion (“collective cascade”) of displaced atoms of target, including the constituents of cluster themselves, due to the transfer of cluster momentum. Thus, it is these displaced atoms which penetrate in the medium. During this collective penetration, some constituents of cluster can reach a certain depth which may be considered as the range of the deepest implanted constituents of cluster. It is shown that, the depth of penetration depends on the initial radius of cluster, its velocity and the properties of graphite. In addition, the depth varies non linearly with cluster velocity, for small clusters (n ≤ 7), while for large clusters (n ≥ 13), it varies (i) linearly with cluster velocity (or momentum) when the force proportional with speed of cluster is dominant. (ii) Linearly with the square of cluster velocity (or energy) if the constant force becomes dominant. It is shown that, a mechanism based on a collective motion of displaced atoms including the constituents of cluster themselves, induced by transfer of cluster momentum to the medium, permits to explain the behavior of measured depth of implanted clusters into graphite. This collective motion involves only one free parameter for all clusters of the same nature which are used as projectiles in the same experiment.

The dosimetric features of the Fricke dosimeter in clinical linear accelerator beams are considered. Experimental data were obtained using various nominal energies 6 and 18 MV, 12 and 15 MeV, including the (60)Co γ-ray beam. The calibration of the dosimeters was performed using the ionization chamber as a reference dosimeter. Some general characteristics of Fricke dosimeter such as energy dependence, optical density (OD)-dose relationship, reproducibility, accuracy, dose rate dependence were analyzed. The Fricke solution shows linearity in OD-dose relationship, energy independence and a good reproducibility over the energy range investigated. The Fricke dosimeter was found to be suitable for carrying out absorbed dose to water measurements in the calibration of high energy electron and photon beams.

We investigated the ferrous sulphate-benzoic acid-xylenol orange (FBX) aqueous chemical dosimeter for measurement of dosimetric parameters such as the output factor, backscatter factor and lateral beam profiles for different square fields sizes for (60)Co γ-rays. A water phantom was employed to measure these parameters. An ionization chamber (IC) was used for calibration and comparison. A comparison of the resulting measurements with an ionization chamber's measured parameters showed good agreement. We thus believe that the tissue equivalent FBX dosimetry system can measure the dosimetric parameters for (60)Co with reasonable accuracy.

The spontaneous desorption (SD) mechanism is a two-step process. Small molecular ions are field desorbed from a grid and hit a sample, inducing ion emission from the sample. It is shown that the average mass of the primary molecular ions is m/z ≈ 70 and that there is a delayed emission of electrons and ions after the main triggering process in SD. A two-grid arrangement for ion extraction and acceleration with various voltage combinations can be used to enhance the ion emission rate and emission yield in SD.

High charge state ions in the megaelectronvolt and kiloelectronvolt energy regions have been used to bombard a solid surface to study H+ emission under the same experimental conditions. The original experimental set-up is described. A radioactive source is used to generate high charge state ions of 208Tl at 116 keV. It is shown that the emission of H+ ions from a solid surface depends strongly on the primary ion charge state. The velocity and nature of the projectiles are not important parameters. A time scale of 10−16 s is used for the initial process triggering H+ emission, as in electron stimulated desorption.

A liquid metal ion source (LMIS) has been installed on a pulsed ion gun built at the IPN. The time of flight (TOF) spectra of the pulsed beam were recorded. With the gold source several cluster ions (up to 10 atoms in the cluster) and doubly charged ions were identified in the ion beam TOF spectra. With a second pulsation, single cluster ions can be selected as projectiles for secondary ion TOF mass spectrometry. We have studied the secondary ion emission (SIE) induced by cluster impact from a variety of targets: organic, CsI, metallic. A large enhancement of yield is observed by comparison to single atomic ion impact (e.g. factor of 30 between Au3+ and Au+). The secondary ion yields increase strongly with the number of constituents in the cluster. This effect is not linear. A comparison with other types of clusters and also fission fragments of 252Cf has been performed. The rate of secondary emission stimulated by cluster is similar to SI yield induced by fission fragments.