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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.

In J-PARC, the 3 GeV rapid cycling synchrotron (RCS) applied hybrid type thick boron-doped carbon (HBC) foils as charge stripper in the multi-turn injection. Although HBC foils have successfully operated to provide a high-power beam for experimental users since the operation of the accelerator started, the deformation and radio-activation of the foils occurred as serious problems. We investigated the cause of the problems, as result we found that impurities in the foil led to these phenomena. In this report, we describe why impurities were mixed in the foil, and which kinds of impurities were found by various methods of analysis. The effect of impurities is also discussed.

In the 3 GeV rapid cycling synchrotron (RCS) of the Japan proton accelerator research complex, we adopted the multi-turn charge exchange injection scheme using the stripper foils. After the fine beam tuning in the RCS, most of the beam losses occur at the foil only. However, the high residual doses were detected around the stripper foil, which cannot be explained by the direct scattering of the injected H− and circulating proton beams with the stripper foil. From the measurements and simulations, it is identified that secondary particles produced in the nuclear reactions with the foil had caused the high residual activity around there. The radio-activation of the foil itself and the high residual dose around the foil are intrinsic problems for all high power beam accelerators with stripping foil. A safe and efficient maintenance in the high radiation and narrow space in these accelerators is important. The foil maintenance under such an environment is required to keep staff radiation exposure as low as possible to reduce the risk of radioactive foil breakup or dispersion and to retrieve the foil without breaking for its analysis. We achieved a safe and efficient maintenance method to retrieve the radioactivated stripper foils.

Isotopic and natural carbon foils made by thermal cracking method are used for various purposes in nuclear physics experiments. An apparatus equipped with an oil free vacuum pumping system has been constructed to produce such foils on a resistively heated metallic Ta filament by the thermal cracking method. Properties of the foils such as accessible thickness and area, uniformity, purity and yield in the foil preparation were investigated. We also investigated the following issue during the foil production; when the Ta filament temperature was decreased after the cracking process, the cracked layer sometimes broke into pieces from the filament. Eventually, we could successfully fabricate enriched isotopic 12C foils and natural carbon foils with thicknesses from 0.2 to 5 mg/cm2 and with a dimension of 20 × 20 mm2 or even larger.

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.

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.

Enriched self-supporting targets of 28,29,30 Si are often used in the field of high resolution nuclear physics experiments. The Si targets were prepared by the thermal evaporation deposition or reduction–deposition methods. The targets, however, are always contaminated by oxygen as Si-material is easily oxidised. These contaminated targets lead to poor data with low S / N ratio. Thus it is very useful if one can estimate the amount of oxygen in the target quantitatively before experiments. In this work we have developed a method to estimate the amount of oxygen in the Si target. We used α-ray and β-ray thickness gauges, which have different sensitivity to oxygen atoms. Namely, the α-ray gauge is more sensitive to light elements such as oxygen compared to the β-ray gauge. Thus one can deduce the amount of oxygen by comparing the oxygen thickness measured by α-ray gauge with that of the β-ray gauge. Accuracy of a few percents can be obtained for the oxygen content in Si targets with a thickness of 1 mg/cm 2 . The present method can also be applied to heavy elements such as Ta 2 O 5 .

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.

To accumulate high-intensity proton pulses, the Los Alamos Proton Storage Ring (PSR) uses the chargeexchange injection method. H -ions merge with already circulating protons in a bending magnet and then are stripped of their two electrons in a carbon stripper foil. The circulating protons continue to interact with the foil. Despite efforts to minimize the number of these foil hits, like “painting” of the vertical phase space, they cannot be eliminated totally. As a result, foil heating and probably also radiation damage limit the lifetime of these foils. In recent years LANL has collaborated with KEK to improve the carbon foils in use at PSR, and these foils now typically last for several weeks. Recently an alternative in the form of corrugated diamond foils has been proposed for use at SNS. We have tested these foils in the PSR. Here we compare their performance in a PSR production beam to that of the LANL carbon foils during the 2005 run cycle. First results from the 2006 run cycle will also be presented.

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.

The Japan Proton Accelerator Research Complex (J-PARC) has been under construction in Tokai-mura, Ibaraki, Japan. Three independent charge stripper devices are set up at the injection line of the 3 GeV Rapid Cycling Synchrotron (RCS). The H− beam accelerated by a 181 MeV Linac is charge-exchanged to a H+ beam by the first stripper foil, and then injected into the RCS. The H0 and H− fractions of the beam, which are not stripped by the first stripper foil, are converted into a H+ beam by the second and the third stripper foils. We have designed the charge exchange devices by adopting the transfer-rod system for moving the foils in a vacuum. We have fabricated a new type of transfer-rod, which can move over a distance of 1500 mm. We have also developed a new telescope system to observe possible wrinkles and pinholes of the foil. The system withstands more than 1 MGy of radiation dose and has a resolution of 250 μm at a distance of 10 m from an object.

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.

We have made enriched 12C targets to accurately measure the cross-section of the 12C(α,γ)16O reaction, which is very important in nuclear astrophysics. Isotopically enriched 12C targets for studying this small cross-section, especially for use with an intense pulsed α beam was desired to meet the following requirements: (1) use of impurity-free enriched 12C, (2) stability for a long time measurement and (3) uniform thickness in the range 200–300 μg/cm2. To meet these experimental requirements, isotopically enriched amorphous 12C powder was converted into graphite powder in an electric furnace at a temperature of 3000 K and subsequently the graphite powder was deposited on a thick Au backing via the HIVIPP method. Targets thus prepared could be made thicker than 200 μg/cm2. They had a good uniformity and a very high stability against irradiation with high intensity ion beams.

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.

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.

Enriched 12C targets were needed to measure accurately the cross-section of the 12C(α,γ)16O reaction, important in nuclear astrophysics. A target of approximately 100 μg/cm2 thickness was made by depositing carbon powder on a thick (approximately 400 mg/cm2) Au substrate by using the H Igh energy V Ibrational P owder P lating method. The powder was made from a carbon plate (>5 mg/cm2), which was produced by a thermal cracking method using enriched 12CH4 gas. The target thus made survived intense and extended beam irradiation, and remained adherent to its substrate.

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.

It was found that the energy loss straggling of 10 MeV/amu 3He1+ and 6Li2+ ions transmitted through thin carbon foils exhibits a bump structure at the foil-thickness region where the charge-changed H-like component becomes comparable to the frozen-charged one. This characteristic behavior could be reproduced well by a Monte Carlo simulation taking account of the electron loss and capture processes. An abrupt increase of the straggling values were also observed for 12C5+ and 12C4+. In order to improve a quantitative understanding, not only the attenuation of H-like and He-like beams as a function of the foil thickness but also the electron-captured fractions for the incidence of bare and H-like beams have been measured and charge changing cross sections among the bare, H-like and He-like charge states are evaluated. A computer simulation taking account of charge exchanges can reproduce quite well the measured energy losses and straggling of partially clothed C ions in the thicker foils.

The energy losses of 10 MeV/amu 3 He 2+,1+ , 6 Li 3+,2+ , 12 C 6+,5+,4+ and 16 O 8+,7+,6+,5+ ions passing through carbon foils of 5–110 μg/cm2 in thickness were measured with a high resolution magnetic spectrograph. The measurement was carried out for ions emerging from foils in the same charge state as the incident beam. The measured fixed-charge stopping powers have been reported in our previous papers. In this paper, the energy loss straggling of partially clothed ions in the charge-state nonequilibrium region is reported for the first time. A double peak structure in energy loss spectra of 3 He 1+ and 6 Li 2+ ions transmitted through carbon foils of 40–50 μg/cm2, which is due to charge changing contributions, was also described before. The present study shows that these contributions also bring about a characteristic behavior in the foil thickness dependence of the straggling values. For partially clothed C and O ions, a linear relation between the foil thickness and the straggling does not hold in the thicker foil region and the straggling exhibits an abrupt increase, although the double peak structure did not appear in the energy loss spectra. A Monte Carlo simulation taking account of the charge exchange can well reproduce the energy loss straggling of 3 He 1+ and 6 Li 2+ emerging from thicker foils.

In order to analyze the physical properties of fullerene C 60 , which has an especially stable spherical shell structure as a cluster, the energy loss is measured when the fullerene C 60 in the energy region of several 100 eV/amu passes a carbon thin foil using the TOF method. The C 60 direct current beam extracted from an electron impact type ion source needs to be converted to a pulsed beam. A chopping method was adopted for the pulsing of this direct current beam, and a high frequency chopper was manufactured. In this way the C 60 direct current beam was changed into a pulsed beam of frequency 50 μs, and about 2.4 μs half width. After accelerating to 100 kV, the beam was passed through carbon foils of 1 and 5 μg/cm 2 , and energy loss measurements were performed.

The quenching of metastable states of antiprotonic helium by collisions with hydrogen and deuterium molecules was studied. A systematic investigation of the delayed annihilation time spectra at various H2 and D2 admixture ratios at the ppm level revealed characteristic changes of their shape, which indicated a strong principal and orbital quantum number dependent quenching of levels in both cases. Applying a laser spectroscopy technique to measure the lifetimes of individual states and cascades we deduced H2 and D2 quenching cross-sections for the states (n, l )= (39, 35) and (37, 34). These cross-sections establish for D2 molecules the strong increase of the quenching efficiency with increasing principal quantum number n of the state under investigation previously reported for the case of H2 admixtures. Our experiments indicate that the low-n state (37, 34) is somewhat less affected by D2 than by H2, while the high-n state (39, 35) is equally quenched by both isotopes.

We have performed laser spectroscopy of metastable antiprotonic helium atoms $(\overline{p}{\mathrm{He}}^{+})$ formed in helium media of 0.2--8.0 bars at 5.8--6.3 K and have observed a density dependence of the resonance vacuum wavelengths for the known transitions $(n,l)=(39,35)\ensuremath{\rightarrow}(38,34)$ and $(37,34)\ensuremath{\rightarrow}(36,33).$ They showed linear redshifts of $0.61\ifmmode\pm\else\textpm\fi{}0.01$ GHz and $0.22\ifmmode\pm\else\textpm\fi{}0.02$ GHz per 1 g/l, respectively. With the shift parameters above, the transition vacuum wavelengths were extrapolated to zero-density limits, yielding ${\ensuremath{\lambda}}_{0}=597.2570\ifmmode\pm\else\textpm\fi{}0.0003$ nm and ${\ensuremath{\lambda}}_{0}=470.7220\ifmmode\pm\else\textpm\fi{}0.0006$ nm, respectively. These values, with a 0.5-ppm precision, were compared with the result of recent theoretical calculations on the energy of the Coulombic three-body system, including relativistic corrections and the Lamb shift. The agreement between our experimental values and the calculations has become as good as $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}.$ This excellent agreement in turn provides a precise value of the antiproton Rydberg constant that surpasses the currently known precision and sets a severe constraint on the antiproton charge $(\ensuremath{-}{Q}_{\overline{p}})$ and the mass ${(M}_{\overline{p}})$ that both $|{Q}_{\mathit{p}}\ensuremath{-}{Q}_{\overline{p}}|/e$ and $|{M}_{\mathit{p}}\ensuremath{-}{M}_{\overline{p}}|{/M}_{p}$ be less than $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7},$ when a more precisely known constraint on the charge-to-mass ratio is combined. Thus we have opened a possibility of determining fundamental constants of the antiproton.

The procedure for the fabrication of self-supporting isotopically enriched 11B targets for the application to nuclear scattering measurements using an electron-beam-excited plasma (EBEP) method was described. A boron target layer of thickness 100±10 μg/cm2 was obtained. The thickness and uniformity of the prepared 11B film were determined by measuring the energy loss of alpha particles across the target area. The purity of the target was examined, and it was found that the investigated boron film contained about 10% impurities.

The pressure dependence of the metastable-state lifetimes in antiprotonic ${}^{3}\mathrm{He}$ atoms $\overline{p}{\ensuremath{-}}^{3}{\mathrm{He}}^{+}$ was studied using the recently observed laser resonance transition $(n,\mathcal{l})=(36,33)\ensuremath{\rightarrow}(35,32)$ in the $\ensuremath{\upsilon}=n\ensuremath{-}\mathcal{l}\ensuremath{-}1=2$ cascade. To this end antiprotons from the Low Energy Antiproton Ring (LEAR) at CERN were extracted in approximately 200-ns-long bunches with about ${10}^{8} \overline{p}$ per bunch and stopped in a ${}^{3}\mathrm{He}$ gas target. Time spectra of delayed annihilation products were taken with the help of a \ifmmode \check{C}\else \v{C}\fi{}erenkov counter with a gated photomultiplier. Under our experimental conditions, $p=136\ensuremath{-}690\mathrm{mbars}$ and $T=5.8\mathrm{K},$ the lowest metastable level $(36,33)$ was found to be much shorter lived than the corresponding state (37,34) in the $\ensuremath{\upsilon}=2$ cascade of $\overline{p}{\ensuremath{-}}^{4}{\mathrm{He}}^{+}.$ It was strongly quenched at pressures above 500 mbars, whereas the higher states in the cascade remained nearly unaffected. This enabled us to investigate the $(37,34)\ensuremath{\rightarrow}(36,33)$ transition by resonant laser deexcitation. Its wavelength was found to be $\ensuremath{\lambda}=524.155\ifmmode\pm\else\textpm\fi{}0.004\mathrm{nm},$ only 6 ppm lower than the theoretical value given by Korobov and Bakalov [Phys. Rev. Lett. 79, 3379 1997)] after including relativistic corrections.

Laser resonance transitions between normally metastable states of antiprotonic helium atoms were induced making use of state dependent quenching effects caused by trace admixtures of \mbox{H$_2$}\ to the target helium gas. With this method of ``\mbox{H$_2$}-assisted inverse resonances'' the decay rates of the states $(n,l)=(39,l),\ l=36,37,38$ and $(38,l),\ l=35,36,37$ of \mbox{$\overline{\mathrm{p}}$}\mbox{He$^{+}$}\ were determined as a function of the \mbox{H$_2$}\ admixture. The quenching cross sections at 30~K deduced therefrom for the states with $n=39$ were found to be of the order of the geometrical cross section for \mbox{$\overline{\mathrm{p}}$}\mbox{He$^{+}$}-\mbox{H$_2$}\ collisions ($2\cdot 10^{-15}$~cm$^2$), with a moderate decrease with increasing $l$. Within a given cascade with constant $v=n-l-1$, the quenching cross sections for states with $n=38$ are smaller by a factor of 4--6 than those for states with $n=39$.

The lifetime of charge stripping foils produced by means of new arc-discharge method developed by Sugai was measured for the bombardment of 10 MeV Au ions. Transmission of Au ions through 12UD-pelletron tandem accelerator was also measured. The lifetime of tested charge stripping foils for 10–15 μg/cm 2 thick and 3.8–5.0 μg/cm 2 thick, respectively, demonstrated to be longer than that of usual arc-discharge method by more than 30 times and 20 times, meanwhile, the transmission of 3.8–5.0 μg/cm 2 thick foils was about 4 times higher than that of 10–15 μg/cm 2 thick foils.

Plastic scintillators based on polystrene and a polystyrene derivative (MS resin) have been produced by the injection-molding technique, and the light yield, transmission, fluorescence, sunshine hardness and radiation hardness were compared with those of casting scintillators. It was also investigated whether or not a fluorescent lamp affected the transparency.

A laser spectroscopic method was developed to directly observe the lifetimes of individual states in metastable antiprotonic helium atoms $(\overline{p}{}^{4}{\mathrm{He}}^{+}).$ Collisional effects with surrounding helium atoms were studied in cryogenic gas targets at pressures between 0.1 and 9.0 bars and at temperatures between 5.5 and 7.0 K. The metastable state $(n,\mathcal{l})=(39,35)$ showed a lifetime of 1.5 $\ensuremath{\mu}\mathrm{s}$, regardless of density, whereas the lifetime of the energetically lower-lying state $(37,34)$ was found to shorten from 1.3 to 0.1 $\ensuremath{\mu}$s with increasing density. The lifetimes of the states $(38,34)$ and $(36,33)$ were determined to be 10 ns and 5 ns, respectively, showing the effects of the internal Auger process. When extrapolated to zero density, the measured lifetimes agreed with the results of calculations for the radiative and Auger widths. Using the fact that the state $(37,34)$ becomes short lived at high density, the resonance $(38,35)\ensuremath{\rightarrow}(37,34)$ at 529.62 nm was detected.

The attenuation of hydrogen atoms and H-like He, Li, C and O ions of about 10-MeV/amu due to the electron loss collisions in thin carbon foils was measured as a function of foil thickness. At the thinner foil region, the incident beams attenuated exponentially as the foil thickness increased. From the attenuation rates, we have determined the electron loss cross sections of the ground state H-like ions. The obtained cross sections are larger than the theoretical predictions based on the Born approximation, especially for projectiles of higher atomic number. They can be well explained quantitatively taking account of the contribution from the projectile excitation which leads to the ionization by the subsequent collision in the foils.

We have developed a new deposition method, which is based on the vibrational motion of microparticles in the electrostatic field between parallel electrodes. This method is straight forward and does not require any complicated mechanism. It has been found that this deposition technique is useful for the preparation of foils, in both the backed and unbacked condition. The first test results are reported.

A precise scan of the previously discovered laser-induced transition ( n, l ) = (37, 35) → (38, 34) in pHe + revealed a doublet structure with a separation of Δ ν HF = 1.70 ± 0.05 GHz. This new type of “hyperfine” splitting is ascribed to the interaction of the antiproton orbital angular momentum and the electron spin.

Very weak laser resonances of unfavored transitions (n,l)\ensuremath{\rightarrow}(n+1,l-1) have been observed in metastable p-|${\mathrm{Am}}^{4}$${\mathrm{He}}^{+}$ atoms by using a pulsed antiproton beam. The observed wavelengths (713.578\ifmmode\pm\else\textpm\fi{}0.006 nm for l=34 and 726.095\ifmmode\pm\else\textpm\fi{}0.004 nm for l=35), as well as those of the known favoured transitions, are to a few ppm accounted for by a recent variational calculation of Korobov [Phys. Rev. A 54, R1749 (1996); and (unpublished)] which includes the relativistic correction to the motion of the electron.

We have employed a laser resonance method to study the interactions of individual states of metastable antiprotonic atomcules p He + with surrounding H 2 molecules. We have found that the lifetimes of the ( n , 1) = (37,34) and (39,35) states are shortened by small admixtures of H 2 molecules in quite different ways; the observed quenching cross section for the upper (39,35) state in helium medium at 1 bar and 30 K is (2.4 ± 1.0) × 10 −15 cm 2 , a factor of 24 larger than that for the lower (37,34) state.

Another laser-induced resonant transition in the v=n{minus}l{minus}1=2 metastable cascade of antiprotonic {sup 4}He atoms has been found by using a double-resonance technique. This was done by setting the first laser to the already known 470.724-nm resonance [(n,l)=(37,34){r_arrow}(36,33)], while the (38,35){r_arrow}(37,34) transition was searched for with the second laser. The resonant transition was found at a wavelength of 529.622{plus_minus}0.003 nm, showing excellent agreement with a recent prediction of Korobov. {copyright} {ital 1997} {ital The American Physical Society}

Mean energy losses of high velocity H-like Li ions in thin carbon foils were measured in the charge state non-equilibrium region. Owing to the screening effect of the bound electron, the fixed-charge stopping power for 6 Li 2+ was smaller than that for 6 Li 3+ . The projectile atomic number dependence of the fixed-charge stopping powers for H-like ions is discussed including our previous data of He, C and O ions with the same velocity. The present result is also compared with the theoretical prediction.

An analog detection system has been developed to measure delayed antiproton annihilation time spectra for laser resonance spectroscopy of metastable antiprotonic helium atoms using the high-intensity pulsed beam of antiprotons from LEAR at CERN.

We have made high-resolution laser spectroscopy of the hyperfine structure of a radioactive isotope $^{179}\mathrm{Ta}$ (${T}_{\frac{1}{2}}=1.8$ y) using an argon-ion sputtering atomic-beam source. From hyperfine constants $A$ and $B$ of the atomic ground state ($^{4}F_{\frac{3}{2}}5{d}^{3}6{s}^{2}$), the magnetic dipole and electric quadrupole moments of the nuclear ground state of $^{179}\mathrm{Ta}(I=\frac{7}{2})$ have been determined for the first time: ${\ensuremath{\mu}}_{I}^{179}=2.289(9){\ensuremath{\mu}}_{N}$ and ${Q}_{s}^{179}=3.37(4)$ b. It is pointed out that magnetic moments of the ground and isomeric states in the region $N=102\ensuremath{-}112$ can be systematically described in terms of the presently available theory while the revealed systematic behavior of electric quadrupole moments is hardly reproduced by the theory.

An electron capture at the cyclotron energy has been explored by using a high-resolution magnetic spectrograph. The K-shell electron capture from heavy elements (V, Cr, Cu, Ge, Nb, Ag, and Sn) by $^{3}\mathrm{He}^{2+}$ projectiles at 52 and 72 MeV was measured. The dependence of the cross sections on the atomic number of the target obtained at these two energies are compared with current electron-capture theories. \textcopyright{} 1996 The American Physical Society.

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.

The atomic-beam laser-rf double-resonance technique has been used to make precision measurements of the hyperfine structure (hfs) splittings in the 5${\mathit{d}}^{2}$6${\mathit{s}}^{2}$ $^{3}$${\mathit{F}}_{\mathit{J}}$ (J=2\char21{}4) states in $^{177,179}\mathrm{Hf}$ i. By making corrections to the second-order hfs effects, magnetic dipole (A), electric quadrupole (B), and magnetic octupole (C) hfs constants are obtained for the $^{3}$${\mathit{F}}_{\mathit{J}}$ states in $^{177,179}\mathrm{Hf}$: The constant C has a strong J dependence as well as does A and B; the isotopic ratio of the constant A between $^{177}\mathrm{Hf}$ and $^{179}\mathrm{Hf}$ has a significant J dependence, indicating J-dependent hyperfine anomalies, while that of the constant C is independent of J within experimental uncertainties, which is taken to be the ratio of the nuclear-ground-state magnetic octupole moments \ensuremath{\Omega}, i.e., \ensuremath{\Omega}${(}^{177}$Hf)/\ensuremath{\Omega}${(}^{179}$Hf)=-0.41(9). It is also pointed out that there is a clear indication of nuclear-spin dependence of the isotopic ratios of C. The single-electron hfs parameters of the 5d electron for the 5${\mathit{d}}^{2}$6${\mathit{s}}^{2}$ configuration in Hf i are obtained, and the Sternheimer shielding factor ${\mathit{R}}_{5\mathit{d}}$=-0.397(8) is derived.

Hyperfine structure of the 5${\mathit{d}}^{3}$6${\mathit{s}}^{2}$ $^{4}$${\mathit{F}}_{3/2}$ ground state in $^{180\mathit{m}}\mathrm{Ta}$ i was precisely measured by means of atomic-beam laser-rf double-resonance spectroscopy. Hyperfine-interaction constants A and B for the ground state $^{4}$${\mathit{F}}_{3/2}$ were determined with accuracies of 3 and 10 ppm, respectively. The nuclear electric quadrupole moment was derived, as well as a precise value of the magnetic moment for $^{180\mathit{m}}\mathrm{Ta}$ (${\mathit{I}}^{\mathrm{\ensuremath{\pi}}}$=${9}^{\mathrm{\ensuremath{-}}}$): the magnetic dipole moment is ${\mathrm{\ensuremath{\mu}}}_{\mathit{I}}^{180\mathit{m}}$=+4.825(11)${\mathrm{\ensuremath{\mu}}}_{\mathit{N}}$ and the spectroscopic quadrupole moment is ${\mathit{Q}}_{\mathit{s}}^{180\mathit{m}}$=+4.946(20)b.

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.

Laser studies of metastable antiprotonic helium atoms, which we recently initiated by observing a sharp increase of the antiproton annihilation rate induced by laser-stimulated resonant transitions, have been extended. With a single laser tuned to the resonance already found at 597.26 nm, we have now established the time dependence of the upper state population. With two lasers ignited at variable time separation, we also studied the feeding of the upper state from higher atomic levels. The initial populations and level lifetimes of excited exotic atoms were determined.