F J Currell

An overview of the Tokyo electron beam ion trap

A new Electron Beam Ion Trap has recently been completed in Tokyo. The general features of the apparatus, design and operation are given. This paper also surveys the planned and ongoing experimental program.

Characteristics of the beam line at the Tokyo electron beam ion trap

A new beam line has been constructed to make various experiments with highly charged ions produced in an electron beam ion trap. The characteristics of the beam line are reported. Ions are extracted upward into the beam line and are deflected horizontally and analyzed for the charge states by a double-focusing magnet. To obtain sufficient intensity, several electrostatic lenses are located. A quadrupole lens is used to correct the distorted beam shape before an entrance slit of the magnet. Ions are accelerated during the passing of the analyzing magnet to obtain the higher mass resolution. Trajectories were calculated by a ray-tracing program and matrix multiplication for lens actions. Preliminary results are shown here for investigation of characteristics of extracted ions.

The present status of the Tokyo electron beam ion trap

Recent progress of the Tokyo electron beam ion trap (Tokyo-EBIT) project is described. The Tokyo-EBIT is of an original design and construction with several features different from other EBITs in the world. The maximum energy and current of the electron beam are designed to be 340 keV and 300 mA with a magnetic field of 4.5 T. The ongoing and planned physics experiments are described and the results for the initial stage of operation of the Tokyo-EBIT are given.

Protein disulphide isomerase as a target for nanoparticle-mediated sensitisation of cancer cells to radiation

Radiation resistance and toxicity in normal tissues are limiting factors in the efficacy of radiotherapy. Gold nanoparticles (GNPs) have been shown to be effective at enhancing radiation-induced cell death, and were initially proposed to physically enhance the radiation dose deposited. However, biological responses of GNP radiosensitization based on physical assumptions alone are not predictive of radiosensitisation and therefore there is a fundamental research need to determine biological mechanisms of response to GNPs alone and in combination with ionising radiation. This study aimed to identify novel mechanisms of cancer cell radiosensitisation through the use of GNPs, focusing on their ability to induce cellular oxidative stress and disrupt mitochondrial function. Using N-acetyl-cysteine, we found mitochondrial oxidation to be a key event prior to radiation for the radiosensitisation of cancer cells and suggests the overall cellular effects of GNP radiosensitisation are a result of their interaction with protein disulphide isomerase (PDI). This investigation identifies PDI and mitochondrial oxidation as novel targets for radiosensitisation.

Probing nuclear properties by resonant atomic collisions between electrons and ions

The utilization of the resonant atomic electron–ion collision process of dielectronic recombination (DR) as a tool to probe nuclear properties via isotope shifts and hyperfine effects is discussed. Based on DR, this resonance reaction spectroscopy at electron coolers of heavy-ion storage rings denotes a versatile approach to access nuclear parameters such as charge radius, spin, magnetic moment or lifetimes of long-lived excited nuclear states (isomers). The high sensitivity of DR allows for experiments with artificially synthesized rare isotopes and isomers. Recent experimental progress in the preparation of such exotic species at the ESR storage ring in Darmstadt is presented. The DR technique is exemplified for the case of 234Pa88+ (Z = 91).

Antiproton induced DNA damage: proton like in flight, carbon-ion like near rest

Biological validation of new radiotherapy modalities is essential to understand their therapeutic potential. Antiprotons have been proposed for cancer therapy due to enhanced dose deposition provided by antiproton-nucleon annihilation. We assessed cellular DNA damage and relative biological effectiveness (RBE) of a clinically relevant antiproton beam. Despite a modest LET (~19 keV/μm), antiproton spread out Bragg peak (SOBP) irradiation caused significant residual γ-H2AX foci compared to X-ray, proton and antiproton plateau irradiation. RBE of ~1.48 in the SOBP and ~1 in the plateau were measured and used for a qualitative effective dose curve comparison with proton and carbon-ions. Foci in the antiproton SOBP were larger and more structured compared to X-rays, protons and carbon-ions. This is likely due to overlapping particle tracks near the annihilation vertex, creating spatially correlated DNA lesions. No biological effects were observed at 28–42 mm away from the primary beam suggesting minimal risk from long-range secondary particles.

The Belfast EBIT

A new Electron Beam Ion Trap has been designed for use at the Queens University, Belfast. We describe our design, with particular reference to the machines versatility and inclusion of new features which will make the machine particularly suited to the study of electron–ion interactions. An initial experimental program, making use of these features is described as is other information pertinent to potential collaborators.

Target dependence of multi-electron processes in Iq+ (q=10, 15)+rare gas (Ne, Ar, Kr and Xe) collisions

We have determined experimentally the absolute cross sections for i-electron capture (to projectile) and j-electron removal (from target) ( sigma q,q-ij), total electron capture ( sigma q= Sigma i sigma q,q-i), j-electron removal ( sigma qj= Sigma i sigma q,q-ij) and i-electron capture ( sigma q,q-i= Sigma j sigma q,q-ij) for the processes: Iq+(q=10 or 15)+B to I(q-i)++Bj++(j-i)e (B identical to Ne, Ar, Kr and Xe) at collision energy of 1.5q keV. Charge-state distributions of the scattered ions were measured in coincidence with the recoil ions. The absolute electron-capture cross sections were measured by the initial growth-rate method. The experimental results for sigma q and sigma qj were compared with the predictions of the extended classical over-barrier model (ECBM). The branching ratios of the multiply-excited ions produced by multi-electron transfer have also been determined.

Detector systems for use with an electron beam ion trap

This article describes two data systems, primarily for use with x-ray detectors in conjunction with an Electron Beam Ion Trap (EBIT). Both systems are designed from a common viewpoint that useful information should be presented in real-time whilst as much information as possible should be stored for subsequent off-line analysis.

Cold atmospheric pressure plasma jets: Interaction with plasmid DNA and tailored electron heating using dual-frequency excitation

Recent progress in plasma science and technology has enabled the development of a new generation of stable cold non-equilibrium plasmas operating at ambient atmospheric pressure. This opens horizons for new plasma technologies, in particular in the emerging field of plasma medicine. These non-equilibrium plasmas are very efficient sources for energy transport through reactive neutral particles (radicals and metastables), charged particles (ions and electrons), UV radiation, and electro-magnetic fields. The effect of a cold radio frequency-driven atmospheric pressure plasma jet on plasmid DNA has been investigated. The formation of double strand breaks correlates well with the atomic oxygen density. Taken with other measurements, this indicates that neutral components in the jet are effective in inducing double strand breaks. Plasma manipulation techniques for controlled energy delivery are highly desirable. Numerical simulations are employed for detailed investigations of the electron dynamics, which determines the generation of reactive species. New concepts based on nonlinear power dissipation promise superior strategies to control energy transport for tailored technological exploitations.