Search

Tapered glass capillary optics was utilized to produce MeV ion microbeams at the RIKEN Pelletron facility. A microbeam of 3 MeV He ions was used to irradiate HeLa cells and demonstrated an ion track consisting of double strand break points in the cell nucleus. A new microbeam line was developed with profile measurements of 2.8 MeV H+ microbeams in the atmosphere, using image recognition and knife-edge methods. After the suppression of the halo component in the microbeam, a smaller beam size was measured to be approximately 40 μm for the irradiation distance of 1 mm, which satisfied requirements of the planned applications.

Charge deposition dependences of electron transmission through insulating PET nanocapillaries and a tapered glass microcapillary are reported and differences with HCI transmission are noted. Investigations were conducted for electrons with incident energies 500–1000 eV, corresponding to energies per charge similar to those used for HCI studies, incident on (1) an array of PET nanocapillaries (density ∼5 × 108/cm2) with diameters 100 nm in a foil of thickness 12 μm, and (2) on a tapered glass microcapillary with inlet/outlet diameters of 800/100 μm and a length of ∼35 mm. The transmission was measured for incident electrons at small sample tilt angles ranging from 0° to 5° with respect to the beam direction. For most angles, including those near zero degrees, there was an initial quiet period during which essentially no transmission was observed, followed by large rises in the transmission during relatively short periods of charge deposition before equilibrium of the transmission was reached. The resulting equilibrium was stable, blocked or had frequent oscillations depending on the incident energy and the capillary used. Observations for both capillaries show that a negative charge patch is needed to guide incident electrons through the capillaries similar to the manner in which HCIs are guided through capillaries.

An experimental study of electron transmission and guiding through a tapered glass capillary has been performed. Electrons were transmitted for tilt angles up to ∼6.5° and ∼9.5° (laboratory angles) for incident energies of 500 and 1000 eV, respectively. It is found that elastic and inelastic contributions give rise to distinguishable peaks in the transmitted profile. For 500 eV elastic transmission dominates the profile, while for 1000 eV both elastic and inelastic contributions are present. The transmission for both energies was studied as a function of the charge (time) deposition and found to be strongly dependent. Results suggest fundamental differences between 500 and 1000 eV incident electrons. For 500 eV the transmission slowly increases suggesting charge up of the capillary wall, reaching relative stability with infrequent breakdowns for all angles investigated. For 1000 eV for tilt angles near zero degrees the time dependent profile shows oscillations in the transmission, which never reached a stable condition, while for the larger angle investigated the transmission reached near equilibrium. Inelastic processes dominated the transmission for 1000 eV even at very small tilt angles, but was generally elastic (due to Coulomb deflection) for 500 eV even for the largest tilt angle measured.

Straight and curved glass capillaries were tested for the guiding of 8 keV Ar 8+ ion beams. The straight capillary was about 50 mm long and 0.87 mm/1.1 mm in inner/outer diameter. One of the two curved capillaries was similar, but was curved with a 270 mm radius. The other was 53 mm long, had diameters of 2.34 mm/2.99 mm, and was curved with a 150 mm radius. The corresponding bending angles of the two curved capillaries were 9.6° and 17.5°, respectively. Transmission through the straight capillary disappeared when the tilt angle was larger than 5°. The curved capillaries guided the ion beams into their corresponding bending angles, which were much larger than 5°, with transmission efficiencies of a few tens percent. This demonstrates the possibility of developing a new scheme of simple small beam deflectors and related beam optics.

The angular (φ-) dependences of the yields of scattered ions and neutrals were measured when 8–80 keV Ar8+ ions were obliquely incident on the single-crystalline ZnO (0001) and ( 000 1 ¯ ) surfaces at small incidence angles of ψ = 5, 7, and 9° measured relative to the plane of the surface. The φ dependences of the yields had a peak near the specular reflection angle that is φ ∼ 2ψ. The maximum yields of the ( 000 1 ¯ ) surfaces at the peaks were almost twice as large as those of the (0001) surfaces at each incidence angle ψ for a given energy E. A faint difference between the two polarity surfaces was observed in the ψ-dependences of the maximum yields. The influence of the surface polarity on the scattering processes was examined by comparison with simulated results.

We report the experimental study of 1000 eV electrons transported through a tapered borosilicate glass capillary with inlet/outlet diameters of 800 μm/100 μm and a length of 35 mm. Transmission was observed for tilt angles from −9.5° to 1.0°. For tilt angles −9.5° to −4.5° the angular distributions of the normalized intensities of transmitted electrons consisted of a single peak showing stable transmission with inelastic behavior, while for tilt angles closer to zero (−4.0° to −1.0°) the spectrum consisted of two peaks also with an inelastic nature. Interestingly, when the tilt angle was within the range −0.8° to 0°, three peaks were observed, one being the direct peak with only elastic nature, and the other two showing both inelastic and elastic behaviors.

We measured resonant coherent excitation of a 2s electron of 83.3 MeV/u Fe 23+ ions planar-channeling in the ( 2 ¯ 2 0 ) plane of the silicon crystal. A silicon surface barrier detector (SSD) was used as a crystal target in order to obtain information on the ion trajectory in the channel since the energy deposit ( Δ E ) to the SSD gives information on the ion trajectories where the resonant transitions occur. For the low Δ E , i.e., near the channel center, optically allowed 2s–3p transitions were much stronger compared with other transitions. Increasing Δ E , i.e., increasing the amplitude of ion trajectory, the optically forbidden 2s–3s transition rapidly became strong. On the other hand, the optically forbidden 2s–3d transitions did not become strong as rapidly as 2s–3s transition. Furthermore, it was found that the transition energies to the n = 3 states changed with Δ E . The shifts of the transition energies were consistent with the estimation for the energy levels of the Stark-mixed n = 3 states depending on the distance from the channel center.

We observed a slowly and regularly oscillating transmission current through a gap (0.1 mm) of paired soda lime glass plates during an injection of a steady highly charged ion beam. The oscillation frequency was almost proportional to the injection current intensities. This phenomenon can be attributed to the charge–discharge iteration cycle with dynamic resistive switching of the glass plate. Our model calculation based on such cyclic resistive switching well reproduces the experimental observation.

An ion irradiation system in liquid has been developed using a tapered glass capillary with a thin window at the tip. Irradiation at a solid–liquid interface is interesting because it can be applied to novel analysis, radiation testing, and surface modification processes. In this study, polyethylene and polytetrafluoroethylene were irradiated with H+ ions in an aqueous solution containing acrylic acid monomers. The irradiated surfaces which were originally hydrophobic became hydrophilic due to the surface layer formed by the acrylic acid polymer.

We have measured two-dimensional images of 3.5–7 keV Ne 7+ ions guided by PET nanocapillaries as a function of the deposited charge. The transmitted ion position and shape are found to change with the intensity evolution. After saturation of the guided ion intensity, the transmission profile is nearly isotropic and its angular width amounts to about 1°, which differs from previous measurements.

K X-rays emitted from 2.1 keV/u N ions transmitted through a thin Ni microcapillary foil were measured in coincidence with a final charge state qf, using a Si(Li) X-ray detector in the cases of incident charge states of qi = 7 and 6. It was found that (1) the coincidence X-ray yield for (qi, qf) = (7, 6) decreased faster than those for other (qi, qf) combinations, (2) the coincidence X-ray yields did not depend on the number of K-shell holes of the incident ions but on the final charge state qf.

We have made coincidence measurements between L X-rays and final charge states of highly-charged Ar ions passing through a Ni microcapillary thin foil to study the formation and relaxation processes of hollow atoms. By using N6+ projectile ions which have single K-shell hole, Ninomiya et al. [Phys. Rev. Lett. 78 (1997) 4557] showed the existence of long lived excited states formed by multiple electron transfer from a Ni microcapillary thin foil. To further study the formation and relaxation dynamics, such experiments were extended to Ar ions with multiple L-shell holes. The yields of L X-rays from Ar ions, which have one stabilized-electron, decrease faster than those from ions with multiple stabilized-electrons, when the projectiles have multiple inner shell holes.

We observed resonant coherent excitation of the 2s electron to the n = 3 states of 83.5 MeV/u Li-like Fe23+ ions planar-channeling in the ( 2 2 ¯ 0 ) plane of a Si crystal. A survival fraction of the Li-like ions was measured as a function of the angle between the incident beam and the [0 0 1] axis. Clear resonance dips corresponding to the transitions of a 2s electron to all the n = 3 states were observed. The transition of each resonance dip was identified by comparing with spectroscopic data. The resonance dips at the transition energies corresponding to the optically forbidden 2s1/2–3s1/2, 2s1/2–3d3/2 and 2s1/2–3d5/2 transitions were observed as well as the resonance dips at transition energies corresponding to the optically allowed 2s1/2–3p1/2 and 2s1/2–3p3/2 transitions.

To detect weak X-rays with a high-resolution spectrometer, a charge-coupled device was operated in a single X-ray photon detection mode. A procedure to effectively identify single X-ray was established. In the case of 2.3 keV/u N7+ and Ne9+ incidence, X-rays emitted from ions transmitted through a Ni microcapillary target were measured with the spectrometer using the procedure of the single event mode. The signal-to-noise ratio was improved by using the single photon counting method.

The resonant coherent excitation from a 1s state to n=2 states of 94 MeV/u Ar17+ ions channeling in the (2 2 0) plane of a Si crystal was observed as the decrease of the survival fraction of Ar17+. Three resonance dips of survival fraction were clearly seen. The resonance profile is attributed to the spin–orbital interaction, the position-dependent Stark effect, the position-dependent transition probability and the position-dependent ionization probability of excited states. The estimated experimental resolution of measurement of the resonance profile is comparable to the width of the narrowest resonance dip (∼1.5 eV FWHM) or less.

The formation and relaxation processes of hollow atoms and related excited states of ions produced with a Ni microcapillary thin foil have been studied employing various experimental techniques. The first stage of the charge transfer from the surface to the ions was studied by using visible light measurements. On the other hand, X-ray measurements revealed the core electronic configurations of ions at the last moment of the hollow atom evolution. The overall feature of the electron capture processes in the capillary was given by the charge state distribution measurements.

Instantaneous switching to the voltage state of a superconducting tunnel junction (STJ) following a decrease in the critical current induced by a heavy ion beam was observed by introducing 40Ar particles with a kinetic energy of 95 MeV/nucleon into an Nb/Al–AlOx/Nb STJ. The particle detection by using this rapid switching of STJ could realize fast timing measurements at the level of ps.

The pulse-height spectrum and two-dimensional image of a 0.5 mm thick GSO scintillator were investigated for a 6 A cold neutron beam. The 31 and 81 keV peaks resulting from neutron absorption by Gd nuclei were identified in the pulse-height spectrum by using a photomultiplier tube. Images of 1.5 and 2.1 mm (FWHM) in diameter were observed for 1 and 2 mm diameter incident beams with an image intensifier and viewed by a CCD camera, corresponding to a position resolution of 1.3 mm (FWHM). The result implies that a position resolution of better than 100 μm would be achievable by employing a GSO scintillator thinner than 20 μm .

We are developing high-resolution X-ray detectors based on superconducting tunnel junctions (STJs). A two-stage superconducting quantum-interference device (SQUID) amplifier with high gain, low noise and high sensitivity was employed as a readout electronic device. We have developed the STJ readout circuit which makes it possible to optimize the STJ bias condition without disturbing the operating point of the SQUID amplifier. High-resolution X-ray detectors using our system is discussed.

X-ray detectors based on Nb/Al/AlO x /Al/Nb superconducting tunnel junctions (STJ) have been fabricated. X-ray responses of the fabricated STJs were measured by illumination with X-rays from a 55 Fe electron capture source. The energy resolution of 41, 58 and 65 eV (FWHM) at 5.9 keV were obtained for 20×20, 100×100, 200×200 μm 2 , square-shaped devices, respectively. The X-ray measurements were performed at 0.35 K using a charge-sensitive preamplifier at room temperature. We also discussed the capability to suppress the substrate phonon events using Al 2 O 3 insulation layer. An advantage for the combined use of the Al 2 O 3 insulation layer and the sapphire substrate was demonstrated.

It is possible for a superconductive transition edge sensor (TES) to detect directly the low energy proton generated in the neutron beta decay. The precision measurement of the proton spectrum is important to test the prediction of the Standard Model of electroweak interaction. Therefore, we are developing a TES microcalorimeter with a large effective area for a proton detector. Our first TES device consists of four-pixels using a Ti/Au bilayer. All pixels are parallel biased and X-rays from a 55Fe source are detected successfully.

We present a novel facility for micro-irradiation of living targets with ions from a 1.7 MV tandem accelerator. We show results using 1 MeV protons and 2 MeV He(2+). In contrast to common micro-irradiation facilities, which use electromagnetic or electrostatic focusing and specially designed vacuum windows, we employ a tapered glass capillary with a thin end window, made from polystyrene with a thickness of 1-2 μm, for ion focusing and extraction. The capillary is connected to a beamline tilted vertically by 45°, which allows for easy immersion of the extracted ions into liquid environment within a standard cell culture dish. An inverted microscope is used for simultaneously observing the samples as well as the capillary tip, while a stage-top incubator provides an appropriate environment for the samples. Furthermore, our setup allows to target volumes in cells within a μm(3) resolution, while monitoring the target in real time during and after irradiation.

High-precision magnetic-field mapping was performed for an experiment to search for a violation of time-reversal invariance in the K + → π 0 μ + ν μ decay at the KEK proton synchrotron. A commercially available three-dimensional Hall probe was used in conjunction with a specially designed mapping device and a goniometer system. Details concerning the measurement principle, calibration, actual measurements and analysis are described.

International audience; Multiply charged ion beam transmission through insulating capillaries is today a very active field of research. Thanks to the work of several groups during the last five years, several features of this unexpected process have been evidenced. The open challenge is to understand and control the self-organized charging-up of the capillary walls, which leads finally to the ion transmission. Up to now, the specific charge distribution on the inner surface, as well as the dynamics of the build-up, are still to be understood. While capillaries usually studied are microscopic pore networks etched in different materials, our concern is in macroscopic single capillaries made of glass. With a length of several centimeters and a diameter of a few micrometers at the exit, these capillaries have nevertheless the same aspect ratio as the etched pores (length/diameter ≈ 100). One of the leading goals of this research on single capillaries is to produce multi-charged ion beams with diameters smaller than a micrometer (nano-beams). These glass capillaries offer the opportunity to be used as an ion funnel due to their amazing properties of guiding and focusing highly charged ion beams without altering neither their initial charge state nor the beam emittance (

A new electromagnetic calorimeter is designed for the experiment E246 at KEK. It consists of 768 CsI(Tl) crystals with PIN-diode readout. A short description of the calorimeter design and performance is given.

The π0 detector constructed for the T-violation search experiment E246 at KEK is described. It consists of 768 CsI(Tl) crystals with PIN photodiode readout. The crystals are assembled in a tight barrel with holes for muons entering the magnetic spectrometer. The design and performance of the calorimeter are presented. The average light yield of 11 000 p.e./MeV and average equivalent noise level of 63 keV (bench test) were obtained for the CsI(Tl) modules used in the calorimeter. The coherent noise was found to be about 11 keV per a module. A readout electronics has been specifically developed for the high counting rate environment of the experiment. A π0 invariant mass resolution of 9.9 MeV (σ) was obtained for the whole detector, including regions around the muon holes. A time resolution of 3.8 ns (rms) was achieved in the photon energy range of 10–200 MeV.