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We fabricated high-lifetime thin nitride carbon stripper (NCS) foils with high nitrogen contents using ion-beam sputtering with reactive nitrogen gas and investigated the dependence of their lifetimes on the sputter angle. The nitrogen in carbon foils plays a critical role in determining their lifetime. Therefore, in order to investigate the effects of the nitrogen level in NCS foils on foil lifetime, we measured the sputtering yield for different sputter angles at a sputtering voltage of 10 kV while using carbon-based targets. We also measured the nitrogen-to-carbon thickness ratios of the foils using Rutherford backscattering spectrometry. The foils made at a sputter angle of 15° using a glassy amorphous carbon target exhibited an average increase of 200-fold in lifetime when compared to commercially available foils.

Newly developed Hybrid type Boron mixed Carbon (HBC) stripper foils are extensively used not only for the RCS of J-PARC and PSR of LANL, but also for other low energy, high intensity proton accelerators in medical applications. We had before tested HBC stripper foils with 3.2 MeV Ne+ and DC heavy ion beams. In order to further understand characteristics of HBC stripper foils, we measured the following parameters using the KEK-650 keV H− and light ion Cockcroft Walton DC accelerator: foil lifetime, thickness reduction, uniformity before and after beam irradiation, and foil deformation. Energy deposition in the present experiment was adjusted to a similar level to that of the HBC foil used in the RCS of J-PARC’. In addition, to understand the reason why the HBC stripper foils have high durability against high intensity beam irradiation, we investigated various physical properties, and compared them between the HBC foils and other tested carbon stripper foils. The sizes of the carbon particles in the HBC foil were found to play a vital role in the lifetime.

The tilted-foil method for producing spin-polarized radioactive isotope beams has been studied using the re-accelerated radioactive 8 Li and 123 In beams produced at Tokai Radioactive Ion Accelerator Complex (TRIAC) facility. We successfully produced polarization in a 8 Li beam of 7.3(5)% using thin polystyrene foils (4.2 μg/cm 2 ). The systematic study of the nuclear polarization as a function of the number of foils and beam energy has been performed, confirming the features of the tilted-foil technique experimentally. After the study, a spin-polarized radioactive 123 In beam, which is the heaviest ever polarized in its ground state by this method, has been successfully generated by the tilted-foil method, for the nuclear spectroscopy around the doubly magic nucleus 132 Sn.

Accurate measurement of the cross-section of the 12C(α, γ)16O reaction is very important in nuclear astrophysics. Enriched 12C targets prepared with the high energy vibrationl powder plating [HIVIPP] method for this purpose have been used successfully. Initially, however, the 12C deposits for studying this small cross-section partially peeled from their Au backings when irradiated with beam currents≥2 times the 7 μA pulsed α-beam used previously. This problem was solved when the amorphous 12C powders were converted to graphite by heat-treatment in a high-temperature furnace. We investigated powder heat treatments at temperatures of 2600–3500 °C to reveal, which conditions resulted in uniform and highly adhesive depositions on Au backings.

We have successfully developed a new method to reduce the amount of carbon buildup on thin cluster (less than 3.5 μg/cm 2 ) carbon stripper foils by heating them with infrared radiation during beam bombardment. We studied the carbon buildup and the foil temperature on foil lifetime using a 2.0 ± 0.5 μA beam of 3.2-MeV Ne + ions. It was found that the carbon buildup begins to rapidly suppress at 460 °C; further, at a foil temperature higher than approximately 820 °C, the initial foil thickness did not change until the foil ruptured. We also found that the carbon buildup shortens the lifetime of stripper foils. The foils treated by the newly developed present method could withstand the maximum and average total beam charges of 530 mC/cm 2 and 340 mC/cm 2 , respectively, which are approximately 18 and 11 times larger than the values for the best commercially available foils and approximately 3 and 2 times greater than the values for the cluster foils that are not treated by this method.

Thin carbon stripper foils used in high-intensity proton accelerators and heavy-ion accelerators must have long lifetimes. Thin carbon foils were fabricated by ion-beam sputtering using reactive and inert gas ions. The lifetime of the foils was measured using a KEK 650-keV high-intensity DC H − (negative hydrogen ion) beam; changes in the foil thickness and surface deformations during irradiation were investigated. The lifetime of a typical stripper foil fabricated by heavy-ion-beam (Ar and Kr) sputtering was 60–70 times longer than that of the best commercially available foils. This paper reports a fabrication method for carbon stripper foils, along with an investigation of their lifetimes and changes in foil thickness during beam irradiation.

Mixed noble gas (Kr+Ne) was used for ion beam sputtering (MIBS) with the aim to produce stripper foils with long lifetime. Further characteristics of the MIBS method were investigated. Angular thickness distributions were measured for the deposits of three crystalline structures of carbon sputter targets: synthetic diamond, glassy carbon and polycrystalline graphite. In this setup the vertical ion beam hits the horizontal surface of the respective carbon target. Differences are presented for three ion energies. In a second setup the angle of the sputter target relative to the vertical ion beam could be adjusted for preparing carbon deposits with lifetime dependences on the inclination angle α on a glassy carbon surface. Resulting stripper foils were tested for their lifetime depending on sputter material and sputtering angle θ in case of graphite. The lifetime measurements were performed with a 3.2 MeV Ne + ion beam as usual.

We have developed hybrid type boron-mixed carbon (HBC) foils for the rapid cycling synchrotron (RCS) of Japan-proton accelerator research complex (J-PARC) using the controlled DC arc-discharge method. The method has been found suitable for the production of thick foils up to a maximum of 700 μg/cm2 due to the strong adhesion to the substrate. The foils thus produced showed rather long lifetime. By the development, high-temperature damage (foil deformation, thickness reduction and pinhole formation) of the foil was significantly mitigated even at a temperature of approximately 1700 K. However, when the foil temperature was higher than about 1800 K, especially pinhole formation in the irradiated area of the foil and its peripheries were always observed. In order to relieve high-temperature damage, we investigated the possibility to lower the temperature rise in single and double layer HBC-foils while keeping the total thickness the same. We also compared the lifetime of the single and the double layer HBC-foils as well as diamond and commercially available foils, using a 3.2 MeV Ne+ ion beam from the Van de Graaff accelerator.

Thick enriched isotopic 130 Te targets are required to search for high-spin isomers in 142 Pr using fusion reactions in 130 Te produced in a low-energy 17 N radioactive ion (RI) beam (∼5 MeV) at RCNP, Osaka University. For this investigation, we have successfully prepared self-supporting 130 Te targets of more than 4 mg/cm 2 in thickness with 22 mm diameter and with-and-without backing-support using the HIVIPP method with a protective wax coating. The deposition yield and the thickness uniformity of the Te targets were compared with Te targets of like thickness and size made by vacuum deposition from a flat boat source and a crucible source with a collimator.

The diffusion coefficients of Li in the NaTl-type Li intermetallic compound of β-LiGa have been measured by using a short-lived radioactive diffusion tracer. As the tracer, the α-emitting radioisotope of 8Li delivered as the energetic and pulsed beam from Tokai Radioactive Ion Accelerator Complex (TRIAC) was implanted into the β-LiGa compounds with the composition in the range of about 43 to 54 at.% Li. By analyzing the time-dependent yields of the α-particles measured according to the repetition cycle of the beam, the tracer diffusion coefficients were extracted over the wide range of Li composition. Abnormal composition-dependence of Li diffusion coefficients in β-LiGa was observed; the stoichiometric β-LiGa showed the highest diffusivity of Li. By referring to the composition-dependent diffusivity of Li in the iso-structural β-LiAl and β-LiIn, we could identify the abnormal diffusion of Li in very Li-poor composition of β-LiGa. The anomaly has been discussed qualitatively in terms of the formation of defect complex and the interaction between the constitutional defects.

We recently developed a new variation for the deposition method named HIVIPP (HIgh energy VIbrational Powder Plating), which is based on the high-energy vibrational motion of powder in the high electric field between parallel electrodes at room temperature and in vacuum. The HIVIPP method is very simple and does not require any complicated mechanisms to prepare both supported (backed) and self-supporting targets. The motivation for the present work was a desire to explore whether it could be done successfully with pressures higher than one bar, with reactive gases or inert gases, and without a vacuum-pumping system. The first successful results are reported for depositions of metallic chromium and non-metallic silicon powders in nitrogen, oxygen, and air at >1 bar.

We control the amount of carbon buildup on slackened thin cluster carbon stripper foils (less than 3.5 μg/cm 2 ) by heating with a high-power infrared lamp during beam bombardment. Foil lifetime measurements were performed using 2.0±0.5 μA beams of 3.2 MeV Ne + ions and quantified as the total charge/area before breakage. Lifetimes were obtained up to 1286 mC/cm 2 at maximum and 1139 mC/cm 2 on the average; these values are, respectively, approximately 51 times at maximum and 46 times on average greater than the best commercially available foils, when used unheated and unslackened.

Carbon stripper foils with a higher nitrogen content were made by ion beam sputtering with reactive nitrogen gas. Such foils seem to be very useful as strippers for high-intensity heavy ion accelerators. To know further characteristics of the lifetime of such carbon foils, we have measured the sputtering yield of the carbon source material at a sputtering voltage of 4–15 kV and the lifetime dependence of such foils on thickness. Lifetime measurement was performed with a 3.2 MeV Ne + ion beam. The sputtering yield on average showed 0.75 atoms/ion at over 9 kV sputtering voltage. The lifetime of the foils noticeably depends on the foil thickness, and the thickness range as practical stripper foil is to be around 15 to 33 μg/cm 2 . Two foils made at 13 kV showed extremely long lifetimes of 6800 and 6000 mC/cm 2 at maximum and the foils made above 10 kV lived longer than about 900 mC/cm 2 , which correspond to about 270 and 40 times longer than commercially available best foils. We measured the thickness ratio of nitrogen to carbon in each foil made at the different sputtering voltages and at the different irradiation stages (mC/cm 2 ) by RBS method. We also inspected the structure of a nitrided carbon foil by transmission electron microscopy.

Non-destructive and on-line Li diffusion experiments in Li ionic conductors are conducted using the short-lived !-emitting radiotracer of 8Li. The radiotracers produced as an energetic and pulsed ion beam from TRIAC (Tokai Radioactive Ion Accelerator Complex) are implanted into a structural defect mediated Li ionic conductor of NaTl-type intermetallic compounds ("-LiGa and "-LiIn). The experimental time spectra of the yields of !-particles are compared with simulated results and Li diffusion coefficients in the intermetallic compounds are extracted with an accuracy of ±10%. The diffusion coefficients obtained for "-LiGa with Li content of 43-54 at.% are discussed in terms of the interaction between Li-ion and the structural defects in the specimen, compared with the cases of "-LiAl and "-LiIn. The nonlinear Li-content dependency of Li diffusion coefficients for "-LiGa suggests that the Li diffusion with the Li-deficient region is obstructed by the defect complex composed of vacancies at the Li sites.

An ISOL-based radioactive nuclear beam (RNB) facility, Tokai Radioactive Ion Accelerator Complex (TRIAC), has been jointly developed by High Energy Accelerator Research Organization (KEK) and Japan Atomic Energy Agency (JAEA). The facility started to supply RNBs for experiments in 2005 and RNBs including fission fragments with energies up to 1.1MeV/A are available in the present. Several experimental studies were performed successfully using 8Li beams with various energies.

The Japan-Proton Accelerator Research Complexes (J-PARC) requires thick carbon stripper foils (250–500 μg/cm 2 ) to strip electrons from the H − beam supplied by the linac before injection into the Rapid Cycling Synchrotron (RCS). The 200 MeV H − beam from the linac has a pulse length of 0.5 ms with a repetition rate of 25 Hz and an average beam current of 335 μA. For this high-energy and high-intensity beam, conventional carbon stripper foils will break in a very short time and even a diamond foil will be ruptured at around 1800 K by the MW class accelerator. Thus, thick carbon stripper foils with high durability at 1800 K produced by energy deposition in the foil are indispensable for this accelerator. For this purpose, we have been developing carbon stripper foils of 350 μg/cm 2 by means of both the controlled DC and AC/DC arc-discharge methods. Recently, we have successfully developed hybrid type thick boron-doped carbon stripper foils, which showed a drastic improvement not only with respect to the lifetime, but also with respect to thickness reduction and shrinkage at high temperature during long beam irradiation. In this report the preparation procedure and lifetime measurements with a 3.2 MeV, Ne + beam are presented.

Low-energy (1–2 MeV/nucleon) radioactive nuclear beams (RNBs) of 8Li, 12B and 16N have been produced through nuclear transfer reactions using a recoil mass separator (RMS) at Japan Atomic Energy Research Institute (JAERI). The contamination of the primary beam to the RNB was investigated quantitatively and was well suppressed. The typical beam intensities of 8Li-, 12B- and 16N-RNB were 1.4 × 10 4 , 7.8 × 10 3 and 4.7 × 10 3 pps , respectively. Their purities were 99 % , 98 % and 98.5 % , respectively.

For the effective use of short-lived radioactive beams, soon to be available at the Tokai Radioactive Ion Accelerator Complex, the authors have developed a radiotracer method for diffusion studies in solids. The experimental test was performed by the measurement of the diffusion coefficients of Li in a sample of the compound βLiAl using an α-emitting radiotracer of 8Li (T1/2=0.84 s). It was found that the time-dependent yields of the α particles from the diffusing 8Li that was initially implanted in the sample could be used as a measure of the diffusivity of the tracer in a nondestructive way. The method was applied to measure the self-diffusion coefficients of Li in βLiGa, and for investigating how the Li diffusion in the Li ionic conductors is affected by the concentration of atomic defects (i.e., the existence of the atomic vacancies of Li and the defects in Ga sites that are replaced by Li).

As an effort to effectively use the short-lived radioactive ion beams to be available in near future at Tokai Radioactive Ion Accelerator Complex, we have developed a radiotracer method for diffusion studies in solids. A test experiment has been performed to measure the diffusion coefficients of Li in the sample of LiAl compound, by using the α-emitting radiotracer of 8Li (T1/2 = 0.84 s). The yields of α-particles emitted from diffusing 8Li primarily implanted in the sample have been measured as a function of time under a recurrent time sequence; the implantation of 8Li for 1.5 s (beam-on) and subsequent diffusion for 4.5 s (beam-off). We have found that the time-dependent yields of the α-particles could be used as a measure of the diffusivity of the tracer in a none-destructive way. By taking into account the experimental conditions, we have simulated the time-dependent α-particle yields for various diffusion coefficients and compared with the experimental ones in order to extract the diffusion coefficients of Li in the sample. The process of the simulations and the comparisons is discussed.

An ISOL based radioactive nuclear beam (RNB) facility in Japan, TRIAC (Tokai Radioactive Ion Accelerator Complex), will be able to provide various short-lived radioactive isotopes for experiments with an energy ranging from 0.1 to 1.1 MeV/nucleon. As an interdisciplinary application of the RNB for materials science, two experiments have been proposed; diffusion studies in super ionic conductors, and β-NMR and PAC studies by implantation of polarized RNB. The present status of the experimental and instrumental development for the experiments is discussed.

Japan-Proton Accelerator Research Complex requires thick carbon stripper foils (300–500 μg/cm2) to strip electrons from the H− beam supplied by the linac before injection into the Rapid Cyclic Synchrotron. The 400 MeV H− beam from the linac has a pulse length of 0.5 ms with a repetition rate of 25 Hz and an average beam current of 335 μA. For this high-energy and high-intensity beam, the conventional carbon stripper foils will be ruptured in a very short time. Thus, long-lived thick carbon stripper foils are indispensable to this next-generation accelerator. For this purpose, we prepared carbon stripper foils of 130 μg/cm2 by means of a controlled AC–DC arc discharge method. The preparation procedure is described and lifetime tests with a 3.2 MeV Ne+ beam of 3–4 μA are reported.

The lifetimes of our carbon stripper foils (10–25 μg/cm2) prepared by reactive nitrogen ion-beam sputtering were distributed in a wide range. Expressed in units of integrated beam current received, lifetimes of 750±400 mC/cm2 were usual for a 3.2 MeV Ne+ beam. This wide distribution of lifetimes have been improved by applying a binary gas mixture (N2+Ne) for sputtering of carbon. With high reproducibility, lifetimes of 475±80 mC/cm2, approximately 15 times those of the best standard commercially available foils, have been achieved. We have also investigated the influence light-element admixtures had on the lifetimes of carbon stripper foils.

We have studied, by a computer simulation, the feasibility of the radiotracer method for diffusion studies using short-lived radioactive nuclear beams as tracers. We have considered two typical examples of radiotracers that will be available in KEK-JAERI RNB facility, 18F (half-life: 1.8 h, β+-emitter) and 8Li (half-life: 0.83 s, α-emitter). The sample is set on a given temperature and irradiated by the tracer beams for a time-duration. In the case of 18F, the serial sectioning technique by the ion-beam-sputtering device is assumed to obtain the concentration-depth profile of the tracer diffused during the irradiation time. In the case of 8Li, the simulation reveals that the time-dependent yields of α particles can be used as a measure of the diffusivity of the tracer in a non-destructive way. The present method could be applied to measure rather large diffusion coefficients of various radiotracers with a short measuring time.

A new ISOL-based radioactive nuclear beam (RNB) facility has been constructed as a joint project of the High Energy Accelerator Research Organization (KEK) and the Japan Atomic Energy Research Institute (JAERI) at the Tandem accelerator of the Tokai site of JAERI. It uses heavy-ion linacs and related equipment of the presently closed KEK-RNB facility. Fission fragments with energy from 0.1 to 8 MeV/u will be available at this facility.

The projectile fragment separator provides a wide variety of short-lived RI-ions with less restrictions on their chemical property or lifetime limit. The beam energy and quality is, however, not adequate for low-energy beam experiments, in particular for trapping experiments. Recently, one has proposed to obtain a low-energy beam from an energetic RI-beam leaving a projectile fragment separator by using a large gas-catcher and an rf ion-guide system. In off-line and in on-line test experiments, the principle of the rf ion-guide was proven. An overall efficiency of 0.2% for 70 MeV/u 8 Li from the RIKEN projectile fragment separator (RIPS) was obtained so far.

For the construction of an electron cyclotron resonance (ECR) charge breeder (CB) at KEK-JAERI radioactive nuclear beam facility, we have made a pilot charge breeding system consisting of two compact-sized ECR ion sources. In order to find the necessary conditions for an ECRCB with high efficiency, the charge breeding efficiency for Ar ions in nitrogen plasma has been measured and compared with the results from the simulation of the trajectories of the ions in the plasma. By explicitly taking into account the cumulative small angle scattering of charged ions as well as the confinement magnetic field of the pilot CB, the simulation predicts the stopping efficiency. This is defined as a probability that the injected ions are still within the plasma volume when their initial directional motions have become randomized. Incorporating the ionization efficiency for the ions, the overall breeding efficiency has been estimated. Finally, the characteristics of the ECRCB recently installed for tests at KEK is described.

The performance of the RNB facility at KEK-Tanashi, which is a pilot facility for the E-arena in the KEK–JAERI joint project, is presented. The muonic X-ray spectroscopy of unstable nuclei by combining the RNB with muon-beam from the M-arena in the joint project is introduced.

For the radioactive nuclear beam facility at KEK Tanashi based on an isotope separator on-line (ISOL), two different types of ion sources are currently employed: a single stage 6.4 GHz ECR and a surface ionization-type ion sources. Several proton-rich radioactive nuclear beams were developed for astrophysical interests. LiF powder target in a water-cooled Cu container is used for the production of Ne isotopes and CaF 2 mixed with fine graphite powder for Na isotopes. The ion beams are bunched at the exit of the ion source in order to reduce the beam loss in post acceleration.

A non-destructive and on-line diffusion tracing in Li ionic conductors has been demonstrated. As the tracer, the pulsed beam of the short-lived α-emitting radioisotope of 8Li was implanted into a typical Li ionic conductor LiGa. By analyzing the time-dependent yields of the α-particles measured in coincident with the repetition cycle of the beam, the tracer diffusion coefficients were extracted with a good accuracy. The ordering of the Li vacancies in the Li-deficient β phase of LiGa was observed for the first time in terms of the Li diffusion by the present method.

A new ion guide, with an additional function having an infinite gas thickness by using a strong magnetic field, is proposed, which enables us to stop energetic radioactive nuclear ions in He gas. The stopped singly charged ions, guided in a dc field with a focusing force generated by an rf field in the gas, are extracted with a SPIG (sextupole rf ion guide) of a focusing device for a spectroscopic study of radioactive nuclei.

In order to investigate the nuclear magnetic moments and the magnetization distributions in the unstable nuclei of 7,11Be, laser-microwave spectroscopy experiments using an ion-trap are under progress at IPNS, KEK-Tanashi. Status of the experiment for the first unstable isotope 7Be is reported.

For an investigation concerning the nuclear magnetic moments and their distributions in the nuclei of 7,11Be, an experimental project using laser-microwave double resonance spectroscopy for trapped ions is under progress at INS. Laser cooled ion crystals consisting of a few 9Be+ ions were observed and the ground state hyperfine splitting of 9Be+ was measured with a precision of 10−5. Experiments on the unstable isotope 7Be have been started.

An ISOL-based radioactive nuclear beam facility is just about to come into operation at INS. The present status of the INS radioactive nuclear beam project is reported. The capability of the facility and possible experiments are also discussed, including research programs of nuclear physics and nuclear astrophysics.

A new type of linear ion trap system in combination with a sextupole ion beam guide (SPIG) has been developed for the accumulation of a continuous ion beam. An axial trapping potential is generated by three cylindrical electrodes mounted outside, but concentric to, the SPIG. The ions in a continuous beam are trapped in the potential well via collisions with He gas. This linear ion trap is called the “SPIG-trap”. The properties of the SPIG-trap were tested off-line with a discharge ion source in a gas cell. Up to 106 ions were trapped and extracted as a bunch with an efficiency of 10% for 10 ms of accumulation. The SPIG-trap system was then connected to a gas filled recoil mass separator (GARIS) and tested with an energetic primary beam from a cyclotron (16O, 107 MeV). The overall efficiency of the SPIG-trap including ion losses in an energy degrader, which was placed in front of the He cell, was measured to be of the order of 10−5 for 10 ms accumulation.

The number of stored Ca\(^+\) ions in an ion trap was measured optically by utilizing the metastable states. All the ions trapped are first pumped into the metastable \(D\) states. The ions in the metastable \(D\) states are transferred to the ground \(S\) state via the \(P\) state by exciting a \(D\rightarrow P\) transition. Each ion then emits one photon through a subsequent \(P\rightarrow S\) spontaneous emission. Thus, the number of photons is the same as the number of trapped ions initially in the metastable states. When a fraction of all the stored ions are pumped into the metastable states, the method is still applicable if the fraction of the ions is known.

A pulsed gating-potential method for millisecond beam-bunching has successfully been applied for the first time to a single-stage 6.4 GHz ECR ion source. Clear bunching effects were observed when a pulsed alternating potential of a few hundred volts was applied between the ECR chamber of the source and an electrode placed near its exit hole. The bunched current observed at a sufficiently low repetition rate of the bunching potential shows a sharp peak in the beginning of the duty-on period and decreases exponentially with time, approaching a value expected without the bunching potential. From this time structure of the current, we could deduce mean residence time of ions in the plasma zone. When the repetition rate of the potential is sufficiently high, the bunched current is observed to be almost constant, its magnitude being determined by the duty factor of the bunching potential and the ionization efficiency of the source. We also describe theoretical formulation of the bunching effect in the above two cases, from which the ionization efficiency can be extracted easily.

Thick carbon stripper foils (multi-layer thickness ≈ 200 μg/cm 2 ) have been developed for use with 800 MeV, H + ion beam in the Proton Storage Ring (PSR) at Los Alamos National Laboratory. Foils were prepared by means of the modified controlled ACDC arc discharge method (mCADAD). The lifetime measurements of the foils made by different methods were performed using an 800 MeV proton beam of up to 85 μA in the PSR, and a 3.2 MeV Ne + ion beam of 3 μA at Tokyo Institute of Technology. The foils made by the mCADAD method showed very long lifetimes, as compared to other foils tested, for both 800 MeV p and 3.2 MeV Ne + beam bombardments.

A project to acquire directly nuclear cross sections of (α, n) and (p, n) reactions using low energy light neutron-rich radioactive nuclear beams (RNB) is in progress at JAERI-Tandem facility. The method of the production of neutron-rich RNB, an improvement of a gas counter (MSTPC) in order to work effectively under the high RNB-injection rate, and the feasibility of our experiments are discussed.

In order to study the starting point of the r-process, the 16 N(α, n) cross section has been measured directly at the energy region of E cm = 1.5 – 4.0 MeV, corresponding to the Gamow peak energy T 9 = 2 – 6.

The tilted-foil method for producing spin-polarized radioactive isotope beams has been studied for the application to nuclear physics and materials science, using the radioactive nucleus 8Li ( $\ensuremath I^{\pi}=2^+$ , g = 0.82678(9) , $\ensuremath T_{1/2}=0.838(6)$ s) produced at the Tokai Radioactive Ion Accelerator Complex (TRIAC). We successfully produced polarization in a 8Li beam of $\ensuremath 7.3\pm0.5$ % using 15 thin polystyrene foils (4.2 $\ensuremath \mu \mathrm{g/cm}^2$ fabricated especially for this purpose. A systematic study of the nuclear polarization as a function of the number of foils, beam energy, tilt angle and foil material has been performed, confirming the features of the tilted-foil technique experimentally. The contributions made to the nuclear polarization of 8Li nuclei by the atomic states was investigated.

A device for the deposition of a radioactive Langmuir-Blodgett (LB) film was developed with the use of: (1) a modified horizontal lifting method, (2) an extremely shallow trough, and (3) a surface pressure-generating system without piston oil. It made a precious radioactive subphase solution repeatedly usable while keeping its radioactivity concentration as high as possible. Any large-size thin films can be prepared by just changing the trough size. Two monomolecular-layers of Y-type films of cadmium [ 3 H] icosanoate and 109 Cd icosanoate were built up as 3 H and 109 Cd β-sources for electron spectroscopy with intensities of 1.5 GBq (40 mCi) and 7.4 MBq (200 μCi), respectively, and a size of 65×200 mm 2 . Excellent uniformity of the distribution of deposited radioactivity was confirmed by autoradiography and photometry.

We have prepared very thin plastic supported carbon stripper foils (1.2±0.3 μg/cm 2 ) using a controlled DC arc-discharge (CDAD) method. The lifetime of these foils was measured with 3.2 MeV Ne + ions. These foils recorded lifetimes about four times longer at the maximum and three times longer on the average than those commercially available foils produced by evaporation–condensation.

A spin-polarized radioactive 123In (Iπ, g = 1.220(2) , T1/2 = 5.97(5) s) beam has been successfully generated by the tilted-foil method. This nuclide is the heaviest ever polarized in its ground state by this method. Using the ISOL-based re-acceleration-type facility TRIAC, an 123Ing.s. beam of 305 keV/nucleon went through a stack of 15 carbon foils with a tilt angle of 70° , and an asymmetry of 0.76 ± 0.25% of β-decays was observed by the β-NMR technique. The asymmetry shows that the tilted-foil method combined with a re-acceleration facility is useful for producing spin-polarized beams for applications such as nuclear physics and materials science.

A highly efficient focusing device which uses a RF multipole field (sextupole-ion-beam guide (SPIG)) has been developed for the ion guide isotope separator on-line (IGISOL). The SPIG, placed after the nozzle, consists of six circular rods uniformly distributed on a circle in the plane perpendicular to the axis of symmetry. Under the combined action of the sextupole RF electric field produced by the rods and helium gas flow, well focused ion beams with low energy spread can be transmitted efficiently by use of the SPIG. The experimental results, using a discharge ion source, show that almost nearly 90% of the ions which leave the nozzle can be transported through the SPIG, and that the width of the kinetic energy distribution after the SPIG is about 0.8 eV (FWHM). These experimental results agree with the results of Monte Carlo simulations; the simulation studies also indicate that the size of the spatial distribution in the plane perpendicular to the symmetry axis is less than 1 mm in diameter at the end of the SPIG.

To solve the controversial issue concerning the possible existence of a 17 keV neutrino with a 1% admixture in nuclear [beta] decay, we searched directly for any evidence of a production-threshold effect. The [sup 63]Ni [beta] spectrum was measured with a magnetic spectrometer, with very high statistics along with a fine energy scan over a narrow energy region around the expected threshold. The obtained mixing strength was [vert bar][ital U][vert bar][sup 2]=[[minus]0.011[plus minus]0.033(stat)[plus minus]0.030(syst)]%, very consistent with zero, and decisively excluding the existence of a 17 keV neutrino admixing at the 1% level with the electron neutrino. The corresponding upper limit was set at [vert bar][ital U][vert bar][sup 2][lt]0.073% (95% C.L.). A new limit was also obtained for a wider mass range: [vert bar][ital U][vert bar][sup 2][lt]0.15% (95% C.L.) for 10.5 to 25.0 keV neutrinos.

An on-line ion trap system is under construction at INS in order to study properties of the trapped unstable nuclei produced by a cyclotron beam. Among several subjects on the system, development of a direct trapping method for unstable nuclear ions from a recoil separator is taken to be of first priority. We have successfully developed a new ion cooling device for this purpose using an ion-guide followed by an RF multipole ion beam guide.

We are developing an ion trap system for nuclear physics research at INS using lasers and a Penning trap. It has several important features, i.e., no specificity to ion species, fast response due to dynamic trapping and hopefully a high trapping efficiency.

A surface-ionization ion source for the use of a thick target has been studied by an isotope separator on-line at INS using the 40Ca(p,2pn)38K reaction. The ionization efficiency and release time were measured for CaC2, CaO and CaF2 targets. The measured efficiency turned out to be about 20% both for tantalum and platinum surface ionizers. The release time was also deduced for each target at various values of temperature by measuring time distributions of the extracted radioactivity after bombarding the target for a short time.

We have performed a search for a 17 keV neutrino by looking for a kink in the 63 Ni β-spectrum near the expected energy threshold. Using a large number of events (2.4 × 10 9 ) accumulated in a narrow energy region with the INS iron-free π √2 β -spectrometer, we obtain a mixing strength of [1.8±3.3(stat.)±3.3(syst.)]×10 −4 , and no indication of the presence of a 17 keV neutrino with the order of 1% mixing. We set an upper limit of 0.095% for the admixture of a neutrino with a mass of 17 keV and of 0.1% with a mass range of 10–24 keV, at the 95% confidence level.