Modification of ZnO films under high energy Xe-ion irradiations

ZnO films were deposited on (100) Si substrate by radio frequency magnetron sputtering. These films were irradiated at room temperature with 308 MeV Xe-ions to a fluence of 1.0 x 10(12), 1.0 x 10(13) or 1.0 x 10(14) Xe/cm(2). Then the samples were investigated using RBS, XRD, FESEM and PL analyses. The obtained experimental results showed that the deposited ZnO films were highly c-axis orientated and of high purity, 308 MeV Xe-ion irradiations could not change the c-axis oriented. The topography and PL properties of the ZnO films varied with increasing the Xe-ion irradiation fluence. For 1.0 x 10(13) or 1.0 x 10(14) Xe/cm(2) irradiated samples, surface cracks were observed. Furthermore, it was found that the 1.0 x 10(14) Xe/cm(2) irradiated sample exhibiting the strongest PL ability. The modification of structure and PL properties induced by 308 MeV Xe-ion irradiations were briefly discussed. (C) 2008 Elsevier B.V. All rights reserved.

Beam dynamics design of an RFQ for a planned accelerator, which uses a direct plasma injection scheme

To meet the requirements of providing high-intensity heavy ion beams the direct plasma injection scheme (DPIS) was proposed by a RIKEN-CNS-TIT collaboration. In this scheme a radio frequency quadrupole (RFQ) was joined directly with the laser ion source (LIS) without a low-energy beam transport (LEBT) line. To find the best design of the RFQ that will have short length, high transmission efficiency and small emittance growth, beam dynamics designs with equipartitioning design strategy and with matched-only design strategy have been performed, and a comparison of their results has also been done. Impacts of the input beam parameters on transmission efficiency are presented, too. (C) 2008 Elsevier B.V. All rights reserved.

Effects of helium and oxygen common implantation in silicon wafer

Defect engineering for SiO2] precipitation is investigated using He-ion implantation as the first stage of separation by implanted oxygen (STMOX). Cavities are created in Si by implantation with helium ions. After thermal annealing at different temperatures, the sample is implanted with 120keV 8.0 x 10(16) cm(-2) O ions. The O ion energy is chosen such that the peak of the concentration distribution is centred at the cavity band. For comparison, another sample is implanted with O ions alone. Cross-sectional transmission electron microscopy (XTEM), Fourier transform infrared absorbance spectrometry (FTIR) and atomic force microscopy (AFM) measurements are used to investigate the samples. The results show that a narrow nano-cavity layer is found to be excellent nucleation sites that effectively assisted SiO2 formation and released crystal lattice strain associated with silicon oxidation.

Neutron-proton bremsstrahlung from intermediate energy heavy-ion reactions as a probe of the nuclear symmetry energy?

Hard photons from neutron-proton bremsstrahlung in intermediate energy heavy-ion reactions are examined as a potential probe of the nuclear symmetry energy within a transport model. Effects of the symmetry energy on the yields and spectra of hard photons are found to be generally smaller than those due to the currently existing uncertainties of both the in-medium nucleon-nucleon cross sections and the photon production probability in the elementary process pn -> pn gamma. Very interestingly, nevertheless, the ratio of hard photon spectra R-1/2(gamma) from two reactions using isotopes of the same element is not only approximately independent of these uncertainties but also quite sensitive to the symmetry energy. For the head-on reactions of Sn-132 + Sn-124 and Sn-112 + Sn-112 at E-beam/A = 50 MeV, for example, the R-1/2(gamma) displays a rise up to 15% when the symmetry energy is reduced by about 20% at rho = 1.3 rho(0) which is the maximum density reached in these reactions. (C) 2008 Elsevier B.V. All rights reserved.

Nuclear stopping and compression in heavy-ion collisions at intermediate energies

The nuclear stopping and the radial flow are investigated with an isospin-dependent quantum molecular dynamics (IQMD) model for Ni + Ni and Pb + Pb from 0.4 to and 1.2 GeV/u. The expansion velocity as well as the degree of nuclear stopping are higher in the heavier system at all energies. The ratio between the flow energy and the total available energy in center of mass of the colliding systems exhibits a positive correlation to the degree of nuclear stopping. The maximum density (rho(max)) achieved in the compression is comparable to the hydrodynamics prediction only if the non-zero collision time effect is taken into account in the later. Due to the partial transparency, the growing of the maximum density achieved in the central region of the fireball with the increase of beam energy becomes gradually flat in the 1 GeV/u energy regime. (C) 2008 Elsevier B.V. All rights reserved.

Emission characteristics of three final continuum electrons produced in low-energy double ionization of helium

The double ionization of helium by electron impact for 106 eV incident energy was studied in a kinematically complete experiment by using a reaction microscope. The pattern of the angular correlation of the three emitted electrons was analyzed by selecting different values of the recoil ion longitudinal momentum. The Wannier predicted geometry appears when the recoil ion carries the full initial projectile momentum. It was found that at this low impact energy, the outgoing electrons still remember the initial-state collision information.

Vacuum window of intermediate energy heavy-ion microbeam irradiation facility

The beam must be extracted into the air through the vacuum window to irradiate the living cell. In the window design, the material and thickness must be chosen to compromise the beam spot size broadening and the window safety. The structure-static analysis on the window of different structures and materials is done with the finite element analysis method, and the deformation and the equivalent stress axe simulated. The safety of these candidates is investigated using the intensity theory. In addition, the small angle scattering and the transverse range of ions are simulated using SRIM code, including all the effects on the beam spot size broadening, such as the incident ion energy, the material and the thickness of the window and the air composing. At last, the appropriate vacuum windows are presented, including the structure, material and thickness.

Beam matching between SFC and SSC

The beam matching status between the two isochronous cyclotrons in the Heavy Ion Research Facility at the Lanzhou-Cooling Storage Ring (HIRFL-CSR) is described. Several methods which can be used to accomplish 100% matching are proposed. By comparing of them, the best method is determined. The advantage due to this method is discussed.

Rotating wheel filter design and optimization for a uniform depth dose distribution in heavy ion therapy

Treatment planning of heavy-ion radiotherapy involves predictive calculation of not only the physical dose but also the biological dose in a patient body. The goal in designing beam-modulating devices for heavy ion therapy is to achieve uniform biological effects across the spread-out Bragg peak (SOBP). To achieve this, a mathematical model of Bragg peak movement is presented. The parameters of this model have been resolved with Monte Carlo method. And a rotating wheel filter is designed basing on the velocity of the Bragg peak movement.

Effect of entrance-channel asymmetry on the isospin dependence of nucleon emission in heavy ion collisions

Using the isospin- and momentum-dependent hadronic transport model 1BUU04, we have investigated the influence of the entrance-channel isospin asymmetry on the sensitivity of the pre-equilibrium neutron/proton ratio to symmetry energy in central heavy-ion collisions induced by high-energy radioactive beams. Our analysis and discussion are based on the dynamical simulations of the three isotopic reaction Systems Sn-132+Sn-124, Sn-124+Sn-112 and Sn-112+(112)Su which are of the same total proton number but, different isospin asymmetry. We find that, the kinetic-energy distributions of the pre-equilibrium neutron/proton ratio are quite sensitive to the density-dependence of symmetry energy at incident beam energy E/A = 400 MeV, and the sensitivity increases as the isospin asymmetry of the reaction system increases.

Advance in in-beam PET

Tumor radiotherapy was a promising modality and over 100 years. Beams of heavy-charged particles show high RBE advantages and become the optimum tool for tumors therapy. Newly, along with the development of accelerators, scintillators, micro-electronics and computers, the heavy ion tumor therapy has been recognized more and developed.

Heavy-ion conformal irradiation in the shallow-seated tumor therapy terminal at HIRFL

Basic research related to heavy-ion cancer therapy has been done at the Institute of Modern Physics (IMP), Chinese Academy of Sciences since 1995. Now a plan of clinical trial with heavy ions has been launched at IMP. First, superficially placed tumor treatment with heavy ions is expected in the therapy terminal at the Heavy Ion Research Facility in Lanzhou (HIRFL), where carbon ion beams with energy up to 100 MeV/u can be supplied. The shallow-seated tumor therapy terminal at HIRFL is equipped with a passive beam delivery system including two orthogonal dipole magnets, which continuously scan pencil beams laterally and generate a broad and uniform irradiation field, a motor-driven energy degrader and a multi-leaf collimator. Two different types of range modulator, ripple filter and ridge filter with which Guassian-shaped physical dose and uniform biological effective dose Bragg peaks can be shaped for therapeutic ion beams respectively, have been designed and manufactured. Therefore, two-dimensional and three-dimensional conformal irradiations to tumors can be performed with the passive beam delivery system at the earlier therapy terminal. Both the conformal irradiation methods have been verified experimentally and carbon-ion conformal irradiations to patients with superficially placed tumors have been carried out at HIRFL since November 2006.

Probing the medium effect and isospin dependence of the in-medium nucleon-nucleon cross section in heavy ion collisions

Probing in-medium nucleon-nucleon (NN) cross section sigma(1)(NN)(alpha) in heavy ion collisions has been investigated by means of the isospin-dependent quantum molecular dynamics (IQMD) with the isospin- and momentum- dependent interaction (IMDI(tau)). It is found that there are the very obvious medium effect and the sensitive isospin- dependence of nuclear stopping R on the in-medium NN cross section sigma(1)(NN)(alpha) in the nuclear reactions induced by halo-neutron projectile and the same-mass stable projectile. However, R induced by the neutron-halo projectile is obviously lower than that induced by the corresponding stable projectile. In particular, there is a very obvious dependence of R on the medium effect of sigma(1)(NN)(alpha) in the whole beam energy region for the above two kinds of projectiles. Therefore, the comparison between the results of R's in the reactions induced by the neutron-halo projectile and the corresponding same-mass stable projectile is a more favourable probe for extracting the information of sigma(1)(NN)(alpha) because of adding a new judgement.

A high charge state all-permanent magnet ECR ion source for the IMP 320 kV HV platform

A 320 kV high voltage (HV) platform has been constructed at Institute of Modern Physics (IMP) to satisfy the increasing requirements of experimental studies in some heavy ion associated directions. A high charge state all-permanent magnet ECRIS-LAPECR2 has been designed and fabricated to provide intense multiple charge state ion beams (such as 1000 e mu A O6+, 16.7 e mu A Ar14+, 24 e mu A Xe27+, etc.) for the HV platform. LAPECR2 has a dimension of 0 650 mm x 560 mm. The powerful 3D magnetic confinement to the ECR plasma and the optimum designed magnetic field for the operation at 14.5 GHz makes it possible to obtain very good performances from this source. After a brief introduction of the ECRIS and accelerator development at IMP, the conceptual design of LAPECR2 source is presented. The first test results of this all-permanent magnet ECRIS are given in this paper.

Capability verification of the beam delivery system in the superficially-placed tumor therapy terminal at HIRFL

The passive beam delivery system in the superficially-placed tumor therapy terminal at Heavy Ion Researc h Facility in Lanzhou (HIRFL), which includes two orthogonal dipole magnets as scanning system, a motor-driven energy degrader as range-shifter, series of ridge filters as range modulator and a multileaf collimator, is introduced in detail. The capacities of its important components and the whole system have been verified experimentally. The tests of the ridge filter for extending Bragg peak and the range shifter for energy adjustment show both work well. To examine the passive beam delivery system, a beam shaping experiment were carried out, simulating a three-dimensional (3D) conformal irradiation to a tumor. The encouraging experimental result confirms that 3D layer-stacking conformal irradiation can be performed by means of the passive system. The validation of the beam delivery system establishes a substantial basis for upcoming clinical trial for superficially-placed tumors with heavy ions in the therapy terminal at HIRFL.