Shen Ding-Yu

Stopping power for MeV 12C ions in solids

Abstract The stopping powers for 0.3–6.4 MeV 12 C ions in C, Al, Ti, Cu, Nb and Ag have been measured with the transmission method. The experimental data on stopping power are compared with evaluated values using LSS theory, ZBL semiempirical model predictions and previous experimental data. The results show that there is significant discrepancy between present work and LSS theory; for C in Al, ZBL calculations quite agree with our measurements, yet for C in other stoppers, those cannot reproduce most of present experimental data; our work consists mostly with previous measurements. Moreover, present stopping power data exhibit apparent Z 2 -oscillation.

Extraction of MeV C2+C8+ cluster beams

Abstract Beams of C 2 + C 8 + clusters have been accelerated to 3 MeV in our 1.7 MV tandem accelerator without any modification of the machine. The beam intensity of the smaller C-cluster is large enough for some physics experiments. The change of charge from C-cluster negative ions to positive ions was achieved by collisions with N 2 molecules in a gas cell at the high voltage terminal. The gas density in the stripper cell is an important parameter for obtaining maximum C m + cluster beam.

Stopping power for MeV energy Au ions in silicon

Abstract The range distributions of Au ions with three implanted energies (Ei=1230, 2130, 3030 keV) in silicon were measured using Rutherford backscattering technique (RBS). The projected ranges were obtained and were larger than those of the TRIM-91 calculation. The nuclear stopping power Sn calculated by Biersack general potential and the electronic stopping power Se=A(E/E0)P generated from LSS theory were used to fit the experimental data. Then the values of parameters A and P in the electronic stopping power formula Se=A(E/E0)P were determined. Significant discrepancies of the electronic stopping power between the experimental results and the TRIM-91 calculations were observed.

Stopping powers of A1 for MeV Si ions

Abstract Stopping powers of A1 film for Si ions (0.8–6.4 MeV) have been measured with Rutherford backscattering (RBS) technique. A new method to determine the stopping powers for low-velocity heavy projectiles was used. The experimental results of the stopping powers for low-velocity Si ions are smaller than those of the TRIM code and LSS theory.

Identification and Rutherford Backscattering Measurement of MeV Carbon Cluster Ions

The MeV carbon cluster ions provided by 1.7 MV tandem accelerator were identified and Rutherford backscattering spectra of MeV carbon cluster ions on the gold film were measured with silicon surface barrier detector.

Comparison of Secondary Ion Emissions from Carbon Nanotubes under Bombardments of MeV Si and Si2Clusters

The emission yields of H, H2, H3 and heavy ions from carbon nanotubes under bombardments of Si and Si2 clusters in an energy range of 0.3–3 MeV per atom are measured by using the time-of-flight technique (TOF). The emission yields of the secondary ions increase with increasing energy of Si and the electronic stopping processes play an important role. The enhanced emission yields of secondary ions induced by Si2 clusters at the low energies are clearly seen and attributed to the vicinage effect of the nuclear collision processes of cluster constituents and the secondary ion emissions are still dominated by electronic stopping processes at high energies.

Ion-Implanted Waveguides in a Nd3+-Doped Silicate Glass

Monomode enhanced-index Nd3+-doped silicate glass waveguides fabricated by ion implantation are reported. The Nd3+-doped silicate glass was implanted by 3.0 MeV B+ ions, 3.0 MeV O+ ions and 4.5 MeV Ni2+ ions, respectively. A prism-coupling method was carried out to measure dark modes in the Nd3+-doped silicate glass using a model 2010 prism coupler. The moving fibre method was applied to measure the waveguide propagation loss. After a moderate annealing, the 3.0-MeV B+-ion implanted waveguide loss is about 3.54 dB/cm; the 3.0-MeV O+-ion implanted waveguide loss is about 5.36 dB/cm; and the 4.5-MeV the Ni2+-implanted waveguide loss is about 7.55 dB/cm. The results show that with the increasing ion mass, the loss in implanted waveguide is increased.

Enhancement in Energy Loss of MeV Silicon Clusters in C Films

Energy losses of 0.63-1.03 MeV/atom Sin (n≤3) clusters in thin carbon films (2-12µg/cm2) have been measured by using a special experimental set-up with the Rutherford backscattering (RBS) technique. The experimental results show that, for a given energy per atom, the energy loss of Si2+ ions, as well as Si3+ ions, is significantly larger than that of Si+ ions. This is the first observation of energy loss enhancement in measurements with the RBS technique. The enhancement in energy loss (i.e. the cluster effect) is evident enough when the effective thickness of the carbon target is thin, but not evident when it is thick. The effect will not be obvious until the energy of the projectile is over a certain limit for a special target. This suggests that the cluster effect only occurs in the first layers of the target film, and that the energy of the projectile must be large enough for the effect to be seen.

A microscopic mechanism of low temperature helium release

4He ions of various energies and at various doses were implanted into three kinds of samples: TiH2 films, high purity Ti pieces as-received and after hydrogenation. Thermal release of helium was monitored in-situ by proton-enhanced backscattering. Low-temperature helium release was observed at T ≤ 573K. Single jump model was used to calculate the active energies for the release. Based on the observations, a mechanism of helium cluster-vacancy complex (HemVn-Vi) for low-temperature helium release is proposed.

Formation of Optical Waveguide and Annealing Behaviour of LiNbO3Implanted by 3.0-MeV Nickel Ions

The optically polished LiNbO3 crystal was implanted with 3.0 MeV nickel ions to a dose of 8×1014 ions/cm2. The implanted sample was orderly annealed at different temperatures for different times in air ambient. The waveguide properties before and after annealing were investigated. Dark modes were observed by the prism coupling technique. The reconstructed refractive index profiles were obtained with the reflectivity calculation method. With the fibre probe technique, the attenuation of the Ni-implanted barrier-confined waveguide was measured for the first time. The waveguide loss was reduced from 1.65 dB/cm to 1.19 dB/cm when annealing was at 300 degrees C for 30 min. With the annealing temperature increasing to 370 degrees C, only fewer broad dark modes were found. It is indicated that the lattice damage by implantation began to resume under this annealing condition. After annealing at 380 degrees C for 60 min, all the dark modes disappeared.