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We developed a grid-controlled laser ion source using a KrF excimer laser and investigated the effects of grid-controlled extraction on beam current waveform and beam quality. By using grid-controlled extraction in the over-dense regime, the beam current waveform was found to be stabilized. The beam current increased in proportion to V3/2, where V is the extraction voltage, which proves that the grid control worked properly and that the ion beam was extracted in a one-dimensional space-charge-limited mode. Beam quality measurement using a pepper-pot imaging method revealed that the beam optics was strongly disturbed by the grid potential in the source-limit regime. Conversely, in the over-dense regime there were no deleterious effects of the grid bias on the beam patterns. This result indicated that the virtual anode in the gap acted as a kind of momentum filter and improved the beam quality.

The feasibility of using hot plasmas as strippers for low-energy ion beams has been investigated by measuring charge state distributions of 350 keV/u ions (12C,16O,19F) after their passage through a laser-produced plasma target. The plasma target was produced by irradiating a small pellet of lithium hydride with a Nd-glass laser. The profiles of electron densities of the plasma target were estimated from the intensity profiles of an Ar laser refracted by the plasma. The intensities of ions with different charge states were simultaneously measured using a time-resolved magnetic spectrograph. It was found that this plasma can yield higher charge states than conventional gaseous or solid strippers. Results of a numerical analysis are compared with the experimental data to explain the observed stripping capability of the plasma.

The energy dependence of the stopping power of 16 O ions in a laser-produced plasma target was experimentally investigated in the projectile energy range of 150–350 keV/ u . In order to produce the target plasma a Q-Switched Nd-glass laser was focused onto a small lithium hydride (LiH) pellet. The plasma electron temperature and the electron line density were 15 eV and 2×10 17 cm −2 , respectively. The energy loss of 16 O ions in the plasma was measured by a time-of-flight (TOF) method. We found that the stopping power in the plasma agreed with the theoretical estimation based on a modified Bohr equation with correction at low velocities. In this evaluation, the effective charge of the projectile was calculated by means of rate equations on the loss and capture of electrons. It has been also found that in this projectile energy range the stopping power of the 16 O ions in the plasma still increases with decreasing projectile energy, while it decreases in cold equivalent.

A solid hydrogen target has been developed for the beam–plasma interaction with a GM cycle cryo-refrigerator. The hydrogen gas was fed into the solid forming cell at a pressure of about 30 Torr, and condensed directly into crystal. The hydrogen target could be repeatedly produced every 10 min without breaking vacuum. A TEA–CO2 laser irradiated the solid hydrogen target with an intensity of 2.2×108 W/cm2 to produce a high density plasma. Optical diagnostics of a hydrogen plasma gave a maximum electron density of 2×1017 cm−3 and a maximum electron temperature of 9 eV.

In order to determine the Coulomb logarithm in the interaction between hot plasma and ion beams, the stopping power of 350 keV protons in a laser plasma target was measured by TOF method. The electron temperature and the electron density of the target plasma was 20 eV and 1018 cm−3, respectively. The Bethe’s Coulomb logarithm calculated using the measured stopping power of protons was 1.8 times as large as that in the beam–cold matter interaction. The mean charge state for 350 keV/u 16O after the interaction with the plasma was also measured by using a time-resolved magnetic spectrograph. The Coulomb logarithm of 350 keV/u 16O was estimated by using measured mean charge state and previously measured stopping power. The obtained Coulomb logarithm for both projectiles are compared.

We have measured a time-resolved emittance of a laser ion source by a pepper-pot method using a commercially available digital camera for personal use and a micro channel plate detector. The micro channel plate was operated in pulse mode by applying a short pulse of high voltage to the detector. This enabled us to obtain the time-resolved images of the pepper-pot. The ion source is based on irradiation of a frequency-doubled Nd : YAG laser on a copper target. The copper ion beam was extracted from the laser plasma by an induction accelerator module during 400 ns. The emittance was observed as a function of time between 180 and 380 ns after the extraction voltage was applied.

In order to study the influence of motor vehicles on a local soil environment, depth profiles of elemental concentration of urban roadside soil were investigated by means of thick-target PIXE analysis. For comparison, we analyzed the soil sampled in a university campus with very low traffic intensity. From the measured depth profiles, it was found that the roadside surface layers up to the depth of approximately 5 cm from the ground level are highly polluted by S and Zn. According to cluster analysis this pollution can be attributed to the deposition of tire dust due to the heavy vehicular traffic volumes on the highways.

An energy loss of 240 MeV argon ions in a Z-pinch helium plasma has been for the first time observed throughout the entire pinching process. Standard Stark broadening analysis gives an electron density ranging from 4 to 6 × 1017 cm−3 during the pinch. To deduce stopping power from the energy loss, the target thickness of the helium plasma has been evaluated assuming the mean charge of helium based on thermal equilibrium. The observed electron density and the mean charge of helium give a target thickness of 30 ± 3 μg cm−2 from 1 μs to 1.8 μs after the discharge ignition. The measured stopping power exceeds a tabulated value for cold helium gas by a factor of 2 to 3 around the time of the first pinch. The experimental stopping power is compared with theoretical values calculated using an equation of stopping power for a partially ionized plasma.

This article reports on the interaction between slow ions and a partially ionized plasma. Temporal evolutions of energy loss and charge distribution of 2.4 MeV oxygen beams in the laser-induced polyethylene plasma were measured. The charge distribution showed strong stripping ability in the early phase of the plasma. Stopping power deduced from the experimental energy loss was 1.9 times larger than that for the solid. The effective charge of the projectile ion was estimated from the yields of 4+ and 6+ states. The peak value of the effective charge was 1.4 times larger than that of the solid. The stopping power equation given by Sigmund was extended for the partially ionized plasma and it could reproduce the measured energy loss.

The energy loss of 180 keV/u 28Si ions in a plasma target was measured by using a TOF system. In order to produce the target plasma a Q-switched Nd-glass laser was focused onto a small LiH (Lithium Hydride) pellet. Spherical symmetry of the plasma expansion was checked by a high speed framing camera. Using this system we found that the energy loss of the ions in the plasma was larger than that in the cold equivalent by a factor of 3.5.

We have developed a high-current laser ion source for heavy ion fusion research based on induction accelerators. A frequency-doubled Nd:YAG laser irradiated a copper target with an intensity of 108–109 W/cm2, producing plasmas composed of Cu+ and Cu2+ ions dominantly. The laser plasma supplied a large number of ions (∼1014 ions/pulse) during several microseconds, which meets the requirement of heavy ion fusion. An inductive acceleration module extracted high-current ion beams over 0.1 A/cm2 from a plasma-filled gap.

In order to study influence of automobile traffic on a local urban atmospheric environment, we have investigated suspended particulate matter (SPM) collected at sampling sites in a region which includes a major highway and a residential area in the southern part of Tokyo during August - November 1999. The atomic composition of each sample was measured by means of PIXE analysis using a 2.0 MeV proton beam. Sixteen elements were quantitatively measured. The positional dependence of SPM loading was determined for each element using samples simultaneously collected at three different sites. For the experimental results obtained for downwind conditions, the measured concentration as a function of the distance from the highway was compared with a simple calculation based on the Gaussian plume model. The concentration distribution of some heavy elements in the fine fraction is well reproduced by this analysis. It has been found that for ordinary moderate downwind conditions the area within 300-400 m from the highway is directly affected by emission due to the automobile traffic.

We experimentally investigated the stopping power of 225 keV/u oxygen ions in laser-produced lithium hydride (LiH) plasma. The plasma target was produced by irradiation of a small LiH pellet with a Q-switched Nd-glass laser. We have developed a system to measure the energy loss of projectile ions in the target with a time-of-flight method. We found that the measured stopping power in the plasma was more than three times higher than the one in cold matter. The effective charge of the projectiles determined from the measured stopping power was also higher than the one in cold matter.

We have experimentally investigated the stopping power of a laser-ablated carbon plasma tested with a 225 keV/u oxygen beam. A dense plasma target was produced by irradiation of a graphite rod with a Q -switched Nd–glass laser. We have developed a diagnostics system for the target plasma using laser interferometry. The motion of the fringes was observed by a streak camera in order to obtain time-dependent electron density profiles. The maximum areal electron density of the carbon plasma reached n e l =1×10 18 cm −2 . For the measurement of the energy loss of ions in the target, we developed a time-resolved magnetic spectrometer system with a plastic scintillator and an MCP. Using a streak camera we measured the shift of the beam spot on the MCP. The stopping power observed 40 ns after the laser was fired was 15 MeV/(mg/cm 2 ). This value is enhanced by 50% compared to that in the cold equivalent.

Experimental investigations into the interaction of an ion beam with a plasma target showed increased stripping as compared to cold targets. Measurements were performed with a 900 keV ion beam of 7 Li 1+ . The plasma was created by irradiating the surface of a polyethylene disk with a 6 J TEA CO 2 laser. This produced a partially ionized surface blow-off plasma with electron densities between 10 18 and 10 16 cm −3 . As another plasma target a z -pinch discharge in helium gas has been prepared. This target yields electron densities of about 5×10 17 cm −3 . Interaction will be measured with a 6 MeV/u 40 Ar 18+ beam from the HIMAC accelerator. Concerning the detector signals, the beam line was designed to minimize any noise stemming from the pulsed discharge. The beam line allows acceptably good beam transmission for current densities in the plasma of up to 80 kA/cm 2 .

A laser-produced plasma target system was developed for beam–plasma interaction experiments concerning heavy-ion inertial fusion. Irradiating a small particle of lithium hydride (LiH) with a pulsed laser, transformed the particle into a plasma. The isotropy of the plasma expansion was monitored by charge collectors. The electron density distribution was measured by interferometry. For particle sizes below and irradiation energies above certain critical values, we obtained a spherically symmetric Gaussian-like density distribution and a high degree of ionization. The expected density and size of the spherical plasma as a target for ion beams are roughly ∼10 18 cm −3 and ∼1 mm, respectively.

An intense heavy ion linac system was constructed for basic research on heavy ion fusion and ion-pumped laser at Tokyo Institute of Technology. By using this system, we are planning to study the plasmas induced by the heavy ion beams. At present a 4 He + beam with a current of 1.6 mA and an energy of 220 keV amu −1 is focused onto a spot area of 1.1 mm 2 From this spot size, a beam power density of 140 kW cm −2 is expected to be transferred to the target.

By means of a numerical method, beam dynamics was analyzed for an RFQ, where mixtures of positive and negative ions were injected into the quadrupole channel. In order to simulate simultaneous bunching of ions with opposite charges, the motion of particles injected into the cavity during two RF periods was traced under consideration of 3D Coulomb forces between particles. Effects of neighbor bunches were also taken into account. In the input region of the structure, the transverse beam divergence due to space charge forces was suppressed by the charge neutralization. However, it was found that the bunch formation in the cavity was disturbed by the attractive forces between positive and negative ions, leading to longitudinal beam loss. Dependence of the beam transmission efficiency on the input beam intensity as well as on the blend ratio of two ion species is reported. These results are compared with those obtained when injecting ions of single species.

Motion of off-centered beams in an RFQ for basic researches on nuclear transmutation was analyzed by using a beam optics computer code. In this analysis not only higher-order harmonics in the intervane potential but also 3D beam-generated forces including image effects were taken into account. Beam loss property and transmission efficiency were investigated for different input beam currents as well as for different injection angles. Results are compared with predictions by the PARMTEQ code. Enhancement of beam displacement at the exit of the cavity as well as increase in transverse beam loss was observed as effects of the image charge force. In any case beam loss due to the image effects was less than 3% of the injected particles. For beam injection angles larger than 1°, the beam transmission efficiency decreased owing to non-linear terms in the intervane potential. Tolerance for the error in beam injection angle into the RFQ cavity is also discussed.

We present the velocity measurements in electro-magnetic shock tube for beam interaction experiment by three methods; laser refraction, photodiode for self-emission, and high speed framing camera. The laser refraction showed that the average shock velocity was 6.7 km/s when the initial pressure was 1000 Pa and the initial charging voltage was 16 kV. The self-emissions from piston discharge plasma were measured by photodiodes and by high speed framing camera. The measurements showed that the duration between shock and piston was up to 8 microseconds with a 400-mm propagation in the shock tube, which is enough time as dissociation target for beam interaction experiment.The complementary velocity measurement is significant for understanding the electro-magnetically driven shock physics.

At the Tokyo Institute of Technology, generating a plasma with a heavy ion beam has been studied for basic research on inertial fusion and a heavy-ion pumped laser. These experiments require a high intensity and high brightness beam. An 80 MHz heavy-ion RFQ linac is being constructed to meet the requirements. This linac accelerates particles with a charge to mass ratio ( q A ) greater than 1 16 from 5 keV/amu up to 214 keV/amu. Two-dimensional (2D) machining is applied for cutting of the RFQ vane-tips. We simulated the beam optics including effects of higher order harmonies in the intervane potential (H. Deitinghoff, A. Schempp, H. Klein and O. Pan, Particle Acc. 37–38 (1992) 47; Chen Chia-Erh, Fang Jia-Xun, Li Weigo, Pan Oujia, Lu Yuanrong, Li Deshan, Wang Lishan, Yu Maolin, H. Deitinghoff, A. Schempp and H. Klein, Proc. European Particle Acc. Conf. (1992) p. 1328) for optimization of the vane parameters. In order to increase the acceleration efficiency, synchronous phase was gradually raised from −30° to −20° in the accelerator section of the cavity. The expected beam transmission is 91.8% for a beam current of 0 mA and 68.4% for 10 mA.

Behavior of misaligned ion beams in an RFQ was analyzed by using a 3D beam dynamics computer code. In order to take the image force into account, a 3D Dirichlet's boundary problem defined by the electrode surface and the off-centered beam space charge was solved at every time-integration step. This method was applied to analysis of the beam dynamics in an 80-MHz RFQ. Compared with the result obtained without image charge effects, no marked change was observed for the beam transmission efficiency. However, it has been found that the amplitude of transverse beam oscillation can be amplified by the image charge force.

Using a 3D computer code, beam dynamics in an RFQ has been analyzed under consideration of external electric field with higher-order multipole moments as well as space charge/image charge force. Beam transmission performance for two types of vane tip design with different tip curvature radii are reported. These results are compared with the ones obtained with the idealized linear two-term potential. It has been found that the transverse beam loss under beam-generated force can be enhanced by the external non-linear field due to the vane tip geometries.

For optimization of the vane parameters of a heavy-ion RFQ, we used a beam dynamics code including effects of higher-order harmonics in the intervane potential. By using a three-module cavity structure, we obtained not only precise and easy assembling but also stable RF characters during operation.

The CSA (Compact Storage and Acceleration) ring for FEL was projected in 1989 [T. Hattori et al., Proc. 14th Linear Accelerator Meeting, Japan (1989) 212]. The lattice of the ring is a double bend double achromatic type. The circumference is 15 m. In spite of the short circumference, the ring has two long straight sections for undultors. The bending magnets were completed and their magnetic field strength was measured [Y. Takahashi et al., Proc. 8th. Symp. on Accelerator Science and Technology 8 (1991) 419]. This paper will present the design and the characteristics of the ring. Furthermore, results of beam tracking are reported.

Chemical speciation of chlorine (Cl) in atmospheric particulate matter (APM) was performed by using a wavelength-dispersive PIXE spectrograph based on high-resolution measurement of Cl-Kβ emission. Samples of atmospheric particles were size-fractioned and collected by a cascade impactor at an urban area in Tokyo. The target position with respect to the spectrograph was precisely adjusted by a 2D laser displacement sensor to achieve high detection efficiency. The samples were irradiated with 2 MeV protons from a tandem electrostatic accelerator. The beam current was 300–500 nA. During the irradiation, the target was cooled by liquid nitrogen to avoid the evaporation of volatile Cl compounds. The measured spectra for the NaCl standard samples clearly showed the Cl-Kβ series composed of the Kβ1 and the satellite Kβx, Kβ5 lines. From the measured X-ray yields, it was found that the chemical speciation of samples with Cl concentrations as low as ≈1% is possible by this method. The Cl-Kβ series were also successfully observed in the case of APM samples with particle sizes of 11.0–2.1 μm. The spectra shapes of the NaCl standard samples and an APM sample were slightly different from each other, because of some possible mixing of non-sea salt component in the APM sample.

Tape coil technique has been applied to a compact quadrupole magnet for Wideroe-linac drift tubes. Boiling heat transfer has been tested for effective heat removal from the coil. A simplified numerical analysis of the coil temperature has been made and qualitative agreement with the experimental results has been obtained. A magnetic field gradient of 4.1 kG/cm has been stably obtained for a drift tube size of 100 mm in outer diameter and 23 mm in bore tube inner diameter.

An analysis system has been established for stoichiometry of thin layers composed of chemical elements which range from light elements to medium-heavy ones such as Fe. A beam of 10 MeV 35C1 was used to recoil nuclei from the target. The mass of recoils has been identified by a counter telescope which consists of two timing detectors for time of flight (TOF) and a surface barrier detector (SBD) for energy measurement of each particle. The detection efficiency of the TOF spectrometer was determined as a function of atomic number Z for light elements up to chlorine. Experimental results are reported for LiF/Si, BF2-implanted SiO2/Si and FeOv/C samples. Factors which affect the accuracy of the present method are discussed.

We have developed a high-current laser ion source that can provide low-charge-state ions for induction accelerators. A frequency-doubled Nd:YAG laser (λ=532 nm) irradiated a copper target with relatively low intensities of 108–109 W/cm2. The laser-produced plasma supplied a large number of Cu+ and Cu2+ ions over 1014 ions/cm2 at a distance of 10 cm from the target. We have successfully extracted high-current copper beams over 0.1 A/cm2 using an inductive acceleration module. The beam emittance measured by a pepper-pot method was about 40 πmm mrad. © 2000 American Institute of Physics.

Using an NEC 5SDH-2 tandem and an upgraded KN-4000 single-ended Van de Graaff machine we are investigating the depth profiles of 1,2H, 4He and 6,7Li which have been implanted or dispersed into silicon wafers, SiO2/Si, SiO2/magnetic bubble garnet, soda-lime glass and stainless steel. The tandem is used to generate an 8 MeV 16O beam for ERD measurements of these light elements and also a 15N4+ beam for profiling hydrogen by means of the 1H(15N, αγ)12C reaction. The Van de Graaff has a maximum terminal voltage of 4.75 MV and accelerates 15N2+ ions for 1H profiling and 3He+ ions for highly sensitive 2H measurements by means of the 2H(3He, pα) reaction. An RBS investigation is running instead of PIXE experiments which have been terminated some years ago. We are using two types of homemade cold-cathode Penning-type ion source (PIG). The one has a side-extraction design for the tandem, and the other is an end-extraction source for the Van de Graaff. Owing to very low gas consumption, both sources are suitable for generation of ions of expensive isotopes such as 3He and 15N. We will report the experience with IBA using both types of electrostatic machines.

To observe nonlinearity in the stopping power of a nonideal plasma for heavy ions, we are planning a beam-plasma interaction experiment using 10−100 keV∕u projectiles. For the interaction experiment, a nonideal hydrogen plasma target was developed by means of a shock technique. Time-resolved spectroscopic measurements determined the temporal evolution of the electron density and temperature of the shock plasma. These data revealed that the structure behind the shock front has an appropriate spatial and temporal distribution to be used as a target. We also evaluated the temporal evolution of the Coulomb coupling constant and the degree of ionization at a fixed position where the projectiles are injected. We discuss the feasibility of the nonlinear stopping experiment by evaluating the beam-plasma coupling constant expected from the measured plasma parameters.

High-current ${\mathrm{Cu}}^{+}$ ion beams were extracted from a laser-produced plasma using a pulsed high-voltage multiaperture diode driven by an induction cavity. The amplitude and the duration of the extraction voltage were 130 kV and 450 ns, respectively. During the extraction, explosive beam divergence due to the strong space-charge force was suppressed by the focusing action of the gap between concentric hemispheres. Modulation of the extracted beam flux due to the plasma prefill in the gap has been eliminated by using a biased control grid put on the anode holes. By means of this extraction scheme we obtained a rectangular beam pulse with a rise time as short as $\ensuremath{\approx}100\text{ }\text{ }\mathrm{ns}$. The beam current behind the cathode was limited to $\ensuremath{\approx}0.1\text{ }\mathrm{A}$, owing to space-charge effects, as well as to poor geometrical transmission through the cathode sphere. From the measurement of the extracted beam current density distribution along the beam axis and the beam profile measurement, we found a beam waist slightly downstream of the spherical center of the diode structure. The measured beam behavior was consistent with numerical results obtained via a 3D particle code. No serious degradation of the beam emittance was observed for the grid-controlled extraction scheme.

We are studying an IH (Interdigital-H) type linear accelerator for application as part of the international cooperative research. Acceleration of deuteron and triton by the IH linac were planned for the production of useful radio-isotopes. The plan is to accelerate deuteron to 3.2 MeV by an IH linac for PET (positron-emission tomography) application. The linac was designed to accelerate deuterons from 0.2 MeV to 3.2 MeV by TUM and TIT. The accelerator cavity was manufactured in Romania. The beam-test facility was constructed at the Research Laboratory for Nuclear Reactors, TIT. The linac has successfully accelerated the proton beam. The shunt impedance was estimated to be about 370 MΩ/m by experiment.

Interaction of /spl ap/0.2 MeV/u oxygen ions with plasmas has been studied using laser plasma targets. We have observed high charge stripping at an early rise time of CO/sub 2/ laser and enhanced energy loss in LiH plasma.

Data of pulse height defects (PHD) of silicon surface barrier detectors (SBD) are very important for the particle mass assignment by means of TOF measurements. We have measured pulse height signals from SBD for protons (control) and five heavy ion species ( 16 O, 19 F, 28 Si, 35 Cl, 81 Br) in the incident energy range of 2–8 MeV. The experimental data have been best-fitted to a proposed empirical formula which reproduces PHD values for all particles with A = 16–80 in this energy range. The experimental results are discussed by comparing them with defect values calculated by using the TRIM code and with values calculated by the empirical formula proposed by Kaufman.

An intense heavy ion linear accelerator system is being constructed for basic researches on HIF and heavy ion pumped laser at TIT. This accelerator system consists of an RFQ‐Linac, an ECR ion source, a fine‐focusing beam transport system and a fast beam pulsing system. By using this system, ion beams of 16O+ with currents of 7 mA and an energy of 3.5 MeV will be focused onto a small spot area of about 1 mm2. At present, the maximum beam current obtained from the TIT‐RFQ is 1.6 mA for 4He+. The overall status of this linac system and preliminary experiments with beams of 4He+ are discussed.

By irradiation of a polyethylene disk with a 3-J TEA CO2 laser, a surface blow-off plasma was created. This plasma acted as a stripper medium for a beam of singly ionized lithium at 0.9 MeV incident energy. Stripping to 3+ could be shown on a timescale characteristic for the expansion of the ablated matter into the volume occupied by the beam.

We have developed a high-efficiency high-resolution particle-induced x-ray emission (PIXE) system employing a von Hamos-type crystal spectrometer for a chemical state identification of trace elements in environmental samples. The energy resolution of the system was determined to be about 0.05% through the observation of Si Kalpha(1,2) x rays (1.74 keV) from elemental silicon. The throughput efficiency of the system was also evaluated quasitheoretically to be 1.6x10(-7) counts/incident proton for Si Kalpha(1,2) emission. To demonstrate a chemical state analysis using the high-resolution PIXE system, Si Kalpha(1,2) and Kbeta x-ray spectra for SiC, Si(3)N(4), and SiO(2) were measured and compared. The observed chemical shifts of the Si Kalpha(1,2) peaks for SiC, Si(3)N(4), and SiO(2) relative to elemental silicon were 0.20, 0.40, and 0.55 eV, respectively. The tendency of these shifts were well explained by the effective charges of the silicon atoms calculated by a molecular orbital method.

Using a proton beam with an overall resolution of 300–400 eV (FWHM) spins, parities and partial widths were determined for all resonances observed (25 s -wave, 32 p -wave, 34 d -wave and two g -wave resonances). Differential cross sections were measured for proton elastic scattering at incident energies between 3.15 and 4.0 MeV and for proton inelastic scattering at incident energies between 3.15 and 3.48 MeV. Spectroscopic factors and Coulomb displacement energies were extracted for the fragmented analogue resonances which corresponded to the 5/2 + , 1/2 - , 5/2 + , 9/2 + , 9/2 + and 1/2 + states in 51 Cr at 3.979, 4.036, 4.070, 4.101, 4.155 and 4.610 MeV, respectively. A value of the s -wave proton strength function was deduced.

A system has been developed for heavy-ion irradiation using a 4.75 MV single-ended horizontal Van de Graaff. The present paper describes the development of two PIG ion sources, a beam energy analyzing and a transport system. The facility has been utilized for H( 15 N, αγ) 12 C hydrogen depth profiling and Ne surface bombardment studies. Examples of experimental results are discussed.

A new method is being studied to control the accelerating field distribution in an IH lineac with a high energy gain. In spite of its high shunt impedance, a shortcoming of an IH structure is that a concentration of accelerating field occurs at the low-energy section of the cavity. One of the practical methods to control the accelerating-gap voltages is adjusting the electric-capacity distribution of the structure. This method, however, is not always suitable for an IH lineac when the particle-energy gain is larger than the incident particle energy. The basic idea of our experiments is to utilize an inductive method to “tune” the accelerating field distribution. In order to test the applicability of this method, accelerating field distributions and shunt impedances are measured in terms of these “tuner” configurations by using 1 4 scale models. The results are compared with the calculations based on a four-terminal network simulation.

In order to measure the amounts of fluorine (F) atoms in the off-gas drain from polymer electrolyte fuel cells (PEFCs) using proton Rutherford Backscattering Spectroscopy (p-RBS), we used an impinger where potassium hydroxide (KOH) solution (0.1 mol/L) was filled and prepared the targets for p-RBS using these samples. In the measured RBS spectrum, however, the peak of fluorine (F) atoms of the decomposition products could not be clearly observed due to the interference by the low energy tail of the potassium (K) atom's peak. We confirmed using SEM, EPMA and XRD that the origin of the low energy tail of the potassium (K) atom's peak was the absorption of carbon dioxide (CO 2 ) in the air by potassium hydroxide (KOH) solution during drying. We also found that the target prepared by vacuum drying was more suitable for measuring the spectra of light elements in p-RBS than that by natural drying.

At the Tokyo Institute of Technology (TIT) a four-vane RFQ is to be applied for inertial confinement fusion research. The RFQ (TIT RFQ) is designed for acceleration of particles with charge to mass ratio (q/A) of 1/16 from 5 keV/amu to 213 keV/amu. The planned maximum injection beam current is 10 mA for /sup 16/O/sup +/. Beam dynamics was calculated using a PIC (particle-in-cell) code which can take influence of the multipole components in the intervane potential into account. For an input beam current of 10 mA a transmission of 60% was obtained. A half-scaled cold model was fabricated to investigate fundamental rf characteristics. In the cold model experiment, the difference in electric field strength between each quadrant was minimized to /spl plusmn/3% by using side tuners and a flat field distribution along the beam axis was achieved by adjusting end tuners. >