Three-component approximation for estimation of the nonequilibrium charge fractions of boron and nitrogen ions on passing through thin films

Analytical expressions for nonequilibrium charge fractions and the dependence of the average ion charge on the target thickness are derived on the basis of a three-component approximation. Calculations for B ⁱ⁺ and N ⁱ⁺ ions with velocities of 12 × 10⁸ cm/s (E = 0.75 MeV/nucleon) upon passing through thin organic films (celluloid) are conducted. The calculation results are in agreement with experimental data within the accuracy of measurement (2–5%).     

Energy losses of beryllium ions penetrating through thin films before the attainment of charge equilibrium

The dependences between the energy losses of beryllium ions penetrating through thin organic (celluloid) films and the initial ion charge i ₀ and target thickness t are calculated. The proposed modified method is used to determine the charge fractions and average charge of an ion beam and the half-width and skewness of the charge distributions before the attainment of charge equilibrium. Calculations are performed for Be ⁱ⁺ ions with a velocity of 8 × 10⁸ cm/s (E = 0.33 MeV/nucleon).     

Nonequilibrium charge states of light ions penetrating through carbon films

The formation of helium, carbon, and nitrogen ion charge equilibrium upon their penetration through thin carbon films is examined. The ions under consideration have different initial charges and energies ranging from 0.3 to 3 MeV/nucleon. A semiempirical formula based on measured data is proposed for calculating the dependence of the mean nonequilibrium ion charge on the target thickness and estimating the carbon target thickness corresponding to the achievement of an equilibrium charge state.     

Method for calculating the nonequilibrium characteristics of light ions passing through thin organic films

A method is proposed for calculating the charge fractions, mean charges, and dispersion of the charge distribution in ion beams passing through thin organic films under nonequilibrium conditions. Calculations are performed for N ions travelling at different velocities (from 8 × 10⁸ to 12 × 10⁸ cm/s) in celluloid. The energy loss is estimated depending on the initial charge states and velocities of the incident ions.     

40MeV/u 40Ar与Cu相互作用的靶余核

使用离线y能谱法和厚靶──厚收集箔技术测量了40MeV/u ⁴⁰Ar和Cu相互作用中靶余核的生成截面和前向平均反冲射程FW值.根据电荷分布假设得到了靶余核的质量产额分布.从FW值导出了重离子碰撞中的线性动量转移.与¹²C+Cu和²⁰Ne+Cu的类似结果比较指出,在相同的弹核速度下,相应于中心碰撞的相对线性动量转移随弹核质量增加而减小,但是在⁴⁰Ar离子和Cu的中心碰撞中产生的复合系统的激发能比¹²C和²⁰Ne离子碰撞情况下更高,达到每核子5.3MeV.     

Comparative analysis of light-ion ranges in gaseous,liquid, and solid media

Ranges of ions from He to Ne in gaseous (hydrogen and argon), liquid (water), and solid (carbon) media are analyzed. This analysis demonstrates the different dependences of ranges on the velocities, the charges, and the masses of ions in different velocity region. In the case of small ion velocities, the ranges are directly proportional to their velocities and masses and are inversely proportional to the nuclear charge. In the intermediate velocity region corresponding to an ion energy of Е = 0.1–1 MeV/nucleon, in which processes of ion charge exchange play an important role and the average ion charge differs from the nuclear charge, the ranges become proportional to the squared ion velocities and masses and are inversely proportional to the nuclear charge. To establish the relation between the ion ranges in the regions of small and average velocities, it is convenient to use the universal function f(Z, M) = RZ/M, successfully describing the reduced ranges of ions with given velocities in gaseous, liquid, and solid media. In the case of large velocities where ions upon passing through the media lose all electrons, the ranges are directly proportional to the squared ion energies and masses and are inversely proportional to the squared nuclear charge.     

Non-equilibrium processes in heavy-ion collisions at relativistic energies

We use transport theory to describe the inclusive cross sections for protons and pions produced in collisions between two identical heavy ions at an energy of 800 MeV per particle. In addition to the nucleonic we take the Δ-degree of freedom into account. Thus we consider a two-component system whose distributions in transverse momentum and rapidity we describe by two coupled Fokker-Planck equations. These transport equations contain the one-nucleon knock-out process as initial condition. In the limit of large interaction times they lead to thermal equilibrium (fireball) distributions. For light nuclei the interaction time is not large enough for equilibrium to be reached. A recent experiment for two colliding carbon nuclei at 800 MeV per nucleon shows evidence of nonequilibrium effects. We compare our calculations with experimental data for ¹²C on ¹²C and Ne on NaF at 800 MeV/N.     

Target Residues from the Interaction of Copper with 40MeV/u 40Ar Ions

Cross Sections and average forward recoil range FW were measured for target residues from the interaction of Cu with 40MeV/u ⁴⁰Ar ions using off-line y-ray spectroscopy.The mass yield distribution was obtained with assumption of charge distribution.The linear momentum transfer was calculated from FW values.A comparison with similar results of ¹²C+Cu and ²⁰Ne+Cu reactions indicates that the fractional linear momentum transfer,corresponding to central collisions,decreases with increasing projectile mass at the same energy per nucleon. However,the excitation energy of the composite system created from the collisions of Cu with ⁴⁰Ar ions reached the value of 5.3MeV /u and was higher than those from the collisions with ¹²C and ²⁰Ne ions.     

Evidence for existence of multiply charged argon ions in anomalous cosmic rays

The spectrum of Ar ions in anomalous cosmic rays in the energy range 14–42 MeV/nucleon was measured in the PLATAN-5 experiment at the Mir space station in 1994–1997. The spectrum is analyzed along with the data obtained by the SIS instrument on the ACE spacecraft in the circumterrestrial space. On the basis of the comparison of the spectra recorded within and beyond the magnetosphere, the average effective charge of ACR argon ions has been estimated. The estimate obtained is much larger than unity at energies exceeding 22 MeV/nucleon. The ion charge gradually increases with an increase in energy and reaches the value Q = 4 at an energy of 38 MeV/nucleon.     

Effect of electrode material on the photoconduction behaviour of ion-irradiated kapton-H polyimide

Photoconduction behaviour of 75 MeV oxygen ion-irradiated (fluence: 1.8×10¹³ ions/cm²) kapton-H polyimide film in the visible region has been investigated for different electrode materials at various operating temperatures ranging 40–250 °C and at different electric fields (40–400 kV/cm). A photoinduced exciton formation is the major source for providing charge carriers through thermolization and field-assisted dissociation processes. A decrease in the photocurrent in ion-irradiated samples when compared with pristine samples has been associated with the enhancement in the trapping sites, which may deplete the charge carriers and a loss in the photoactive groups owing to radiation-induced demerization. The evidence of Schottky type conduction (based on Schottky's coefficient estimation) mechanism in irradiated samples is observed at moderate temperatures (80–160 °C). A strong dependence of photocurrent on temperature in irradiated samples reconfirms the thermal ionization process of exciton for photogeneration of charge carriers.     

Studies of anomalous cosmic ray N, O, and Ne using Cn track detectors

We report measurements of the energy spectra of anomalous cosmic ray N, O and Ne in the energy interval 5–25 MeV/nucleon made with stacks of cellulose nitrate sheets exposed on “Cosmos” satellites in Earth's vicinity in 1994. The successive etching was applied for the best charge identification.     

Direct versus thermal particle emission in high-energy heavy-ion collisions

Recent measurements of proton inclusive cross sections for heavy-ion collisions at several hundred MeV per nucleon are discussed in a phenomenological model which assumes coexistence of direct and thermal particle emission. The model postulates the existence of an additive twocomponent structure for inclusive spectra. The two components consist of a direct and a thermal one. The direct component is described in an extended impulse approximation and the thermal component in the participant-spectator geometrical model. Their normalizations are fixed by geometrical considerations. With this model we calculate the charged particle and proton inclusive spectra for Ne on U at 250 MeV per nucleon, Ne on U and Ne on Al at 400 MeV per nucleon, and Ne on NaF at 800 MeV per nucleon. A comparison is made with corresponding data. At 250 MeV and 400 MeV per nucleon, we find the postulated two-component structure to be instrumental in reproducing satisfactorily the slopes and the magnitudes of the data in the critical forward angle region. At 800 MeV per nucleon, due to the larger transparency of the nuclei, non-equilibrium statistical components appear to be important.     

The ISAC post-accelerator

The acceleration chain of the ISAC facility boosts the energy of both radioactive and stable light and heavy ions for beam delivery to both a medium energy area in ISAC-I and a high energy area in ISAC-II. The post-accelerator comprises a 35.4 MHz RFQ to accelerate beams of A/q ≤ 30 from 2 keV/u to 150 keV/u and a post stripper, 106.1 MHz variable energy drift tube linac (DTL) to accelerate ions of A/q ≤ 6 to a final energy between 0.15 MeV/u to 1.5 MeV/u. A 40 MV superconducting linac further accelerates beam from 1.5 MeV/u to energies above the Coulomb barrier. All linacs operate cw to preserve beam intensity.     

Complete Set of Deuteron Analyzing Powers for dp Elastic Scattering at Intermediate Energies and Three Nucleon Forces

With the aim of clarifying roles of the 3NFs in nuclei experimental programs with the polarized deuteron beam at intermediate energies are in progress at RIKEN RI Beam Factory. As the first step, we have measured a complete set of deuteron analyzing powers in deuteron–proton elastic scattering at 250 and 294 MeV/nucleon. The obtained data are compared with the Faddeev calculations based on the modern nucleon–nucleon forces together with the Tucson–Melbourne’99, and UrbanaIX three nucleon forces.     

Four-Body Faddeev–Yakubovsky Equations Using Two-Cluster RGM Kernels: Applications to 4N and 4α Systems

Four-cluster Faddeev–Yakubovsky calculations using two-cluster RGM kernels are carried out for identical clusters. A precise ground-state energy of the α-particle, predicted by the quark-model nucleon–nucleon (NN) interaction fss2, is E _α  = ?26.61 MeV, including approximate effects of the Coulomb force and the charge dependence of the 2N force. The missing ?1.7 MeV in the experimental value ?28.3 MeV is about half of 3–4 MeV, predicted by modern meson-exchange 2N potentials, implying that almost half of 3–4 MeV is attributed to the off-shell effect of our nonlocal NN interaction fss2. As to the applications to four-α system, a method to eliminate the Faddeev redundant components from the basic Faddeev–Yakubovsky equations is proposed.     

Features of the pre-equilibrium charge states of light ions passing through thin celluloid films

A semi-empirical method for establishing of the average charge of ions passing through thin celluloid films is proposed. Calculations for helium (He) and nitrogen (N) ions with different initial velocities (12?18.7 × 10⁸ cm/s for He and 4?12 × 10⁸ cm/s for N) are presented. The equilibrium thickness of a celluloid target in dependence on the initial charge states of incident ions is evaluated.     

Effect of the capture and loss of two electrons on the charge distributions of ions

The effect of the processes of capture and loss of two electrons on the width of the equilibrium charge distribution of ions in different materials is studied. These processes increase the width of the equilibrium charge distribution in the energy region of E < 0.1 MeV/nucleon. The effect increases with decreasing ion nuclear charge and reaches 10–15% for boron ions.     

Investigation of the fragmentation of 20Ne and 40Ar ions at the COMBAS setup

Properties of the COMBAS fragment separator are compared with respective properties of similar setups. Results of experiments aimed at obtaining products of one-proton-stripping reactions induced by a beam of ⁴⁰Ar ions with an energy of 35 MeV/A and two-neutron-stripping reactions induced by a beam of ²⁰Ne ions with an energy of 52 MeV/A are presented. A high resolution of the fragment separator in obtaining secondary neutron-rich ³⁹Cl and neutron-deficient ¹⁸Ne ion beams is demonstrated.     

Breakup Reactions of Drip-Line Nuclei Near N = 20, 28

The one-neutron removal cross section from ²⁹Ne, ^33,35,37Mg, and ^39,41Si on a Pb target have been measured at around 240 MeV/nucleon at the RIBF (RI-Beam Factory) at RIKEN. This main goal of the experiment was to extract the inclusive Coulomb breakup cross sections in order to probe possible halo structures through their enhanced low-energy E1 strengths - so-called soft E1 excitations. The results showed significant enhancement of the one-neutron removal Coulomb breakup cross section for ³⁷Mg. This in turn provides evidence for the existence of halo structure in ³⁷Mg.     

Effect of iodine doping on the photoconduction behaviour of pristine and high-energy heavy ion-irradiated kapton-H polyimide

The effect of iodine doping on the photoconduction behaviour of pristine and 75 MeV oxygen ion-irradiated (fluence: 3.12×10¹² ions/cm²) kapton-H polyimide film in the visible region has been investigated for different doping hours at various operating temperatures ranging 40–250°C and at different electric fields (40–400 kV/cm). The formation of charge transfer complexes in polymers effectively decreases the trapping sites by handling the charge carriers. A decrease in the photocurrent in ion-irradiated samples at higher exposure time for iodine vapours as compared with pristine samples has been associated with the enhancement in the trapping sites which may deplete the charge carriers and a loss in the photoactive groups owing to radiation-induced demerisation. The evidence of Frankel-type conduction (based on the estimation of Schottky coefficients) mechanism in irradiated samples is observed. A strong dependence of photocurrent on temperature in doped pristine and ion-irradiated samples reconfirms the thermal ionisation process of exciton for photogeneration of charge carriers.