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X-rays emitted from Ar 17+ , Fe 24+ and Kr 35+ ions of about 400 MeV/u transmitting through a thin Si crystal of about 20 μm thickness have been measured in a planar channeling condition and compared with those in a random incident condition. We have found that the X-ray yield from Ar 17+ ions is larger for the channeling condition than for the random incidence, while those from Fe 24+ and Kr 35+ ions are rather smaller. Such tendencies are explained by considering the projectile dependences of excitation and ionization probabilities together with X-ray emission rates. A crude simulation has qualitatively reproduced these experimental results. When the crystal thickness is small, the X-ray yield is smaller in the channeling condition than in the random incident condition, because excitation is depressed. However, for thicker crystals, the X-ray yield is larger, since the survived population of projectile-bound electrons is larger due to small ionization probabilities under the channeling condition. This inversion occurs at a specific crystal thickness depending on projectile species. Whether the thickness of the used crystal is smaller or larger than the inversion thickness determines enhancement or depression of the X-ray yield in the channeling condition.

Energetic ions traveling through a single crystal are excited by an oscillating crystal field produced by a periodic arrangement of the atomic strings/planes, which is called Resonant Coherent Excitation (RCE). We have observed enhancement of convoy electron yields associated with RCE of 1s electron to the n=2 excited states of 390 MeV/u hydrogen-like Ar17+ ions passing through a Si crystal in the (2 2 0) planar channeling condition. Lost electrons from projectile ions due to ionization contribute to convoy electrons emitted in the forward direction with the same velocity as the projectile ions. With combination of a magnet and a thick Si solid-state detector, we measured the energy spectra of convoy electrons of about 200 keV emitted at 0°. The convoy electron yield as a function of the transition energy, i.e. the resonance profile, has a similar structure to the resonance profile observed through the ionized fraction of the emerging ions. It is explained by the fact that both enhancements are due to increase in the fraction of the excited states from which electrons are more easily ionized by target electron impact in the crystal than from the ground state.

A resonant slow-extraction method from synchrotron rings has been successfully developed in order to deliver a beam for a period of over several seconds. In the resonant slow-extraction method, an optimization of the parameters is necessary in order to keep the beam size and position constant during the extraction for sufficient use of the extracted beam. For this purpose, a simple method to measure the outgoing separatrix was proposed and verified at the HIMAC synchrotron. In this method, two tantalum rods each with diameter of 1 mm are used as internal probes located near the extraction channel. By observing the extracted beam under the rods inserted into the ring, the outgoing separatrix can be measured. This technique will significantly contribute to the operation of a synchrotron employing resonant slow-extraction.

X-rays emitted from resonant coherently excited (RCE) n =2 states of 390 MeV/amu hydrogen-like Ar 17+ ions were observed under planar channeling in a Si crystal. The resonance profiles for X-ray emission consisting of two peaks for j =1/2 and j =3/2 are characterized by suppression of the j =1/2 peak. The degeneracy of the n =2 states are removed by Stark effect due to the static crystal field. The RCE probability of these Stark splitted substates differs, reflecting the polarization of the oscillating crystal field. However, the associated alignment was not clearly observed. It is explained by the fact that both polarization of the oscillating crystal field and the wave functions of Stark-mixed n =2 states depend on the distance from the channel center, and the X-ray emission is preferred in a channel center in a crystal.

We measured the emerging charge-state distribution of hydrogen-like 390 MeV/u Ar 17þ ions planar channeled in a silicon surface barrier detector for the DE measurement, and observed their energy deposition in the detector simultaneously. We simulated the energy loss spectrum of specific emerging charge state, and succeeded in reproducing it with an adjusting parameter for the cut-off momentum transfer between close and distant collisions. 2002 Elsevier Science B.V. All rights reserved.

A prototype non-destructive beam-profile monitor employing tandem-type MCPs has been designed and tested at HIMAC. The monitor can measure the vertical beam profile of a circulating ion beam in the synchrotron. In a series of tests, however, it was found that the monitor had a defect in the accuracy of the measured profiles. It was caused by an electric field distortion in the work area. The electric field was improved so as to create a uniform equipotential distribution with the aid of a 3D-field simulation code. The field-shaping electrodes were replaced to longer ones, and the applied voltages of each electrode were changed to the optimum values. The monitor has been successfully used for studies of electron cooling as well as monitoring the beam under normal-mode operation in the HIMAC synchrotron.

Resonant coherent excitation (RCE) of 390 MeV/u hydrogen-like Ar 17a ions planar channeled in a Si crystal was investigated through measurements of the de-excitation X-rays as well as the charge state distribution of the transmitted ions. We observed enhancements of both the fraction of ionized Ar 18a ions and the intensity of the de-excitation X-rays under the RCE condition. The na 2 states of Ar 17a in the crystal are split into four energy levels due to spin‐orbit interaction and Stark eAect induced by the planar potential of the crystal. The intensities of the X-rays from the lower two levels were found to be smaller compared with those from the higher two levels, which is explained by the dominance of the 2s component not decaying via a single photon emission. The diAerence between the resonance profiles of the charge state and the X-ray reflects the nature of na 2 states in the crystal field. ” 2000 Elsevier Science B.V. All rights reserved.

Resonant coherent excitation of the 1s electron to na 2 states in a hydrogen-like ion was studied through measurements of the survived fraction of 390 MeV/u Ar 17a planar channeled in a Si crystal. Adopting a totally depleted Si surface barrier detector as a target crystal, the charge state of the individual emerged ion was measured in coincidence with the energy deposition in the target. By changing the incident direction along theO2 20 U ,O 004 U, andO1 11 Uplanes, a series of clear resonances were observed as the decrease in the survived charge fraction due to higher electron loss probability for the excited state. Each resonance profile reflects energy splitting of the na 2 manifold originated from l‐ s interaction and Stark eAect due to the crystal field. From the correlation between the energy loss and survived charge fraction, transition energy as a function of the ion trajectory amplitude is deduced which is in good agreement with calculated results. ” 1998 Elsevier Science B.V. All rights reserved.

Continuum X-rays emitted from Be- and C-targets bombarded with 75-290 MeV/u C6+ ions were observed with an HPGe detector placed at 90\(\) to the beam direction. In all spectra two components could be clearly distinguished: Radiative Electron Capture into Continuum (RECC) forming a characteristic edge, and Secondary Electron Bremsstrahlung (SEB) which dominates at high photon energies. The shape of the spectra was compared to a theoretical description. A special emphasis was given to the details of the RECC edge. It has been found that at the highest projectile energy of 290 MeV/u, in opposite to the lower beam energies, the detailed structure of this edge cannot be reproduced satisfactory within the approach applied.

Results are reported on precise measurements of the weak-decay processes of Λ 4 H and Λ 4 He hypernuclei formed via the 4 He (K stopped − , π − ) reaction. The lifetimes of Λ 4 H (194 −26 +24 ps) and Λ 4 He (256 ± 27 ps) were obtained. The π 0 and π − decay branching ratios of Λ 4 He (0.515 ± 0.035 and 0.322 ± 0.034, respectively) were precisely determined and they are compared with recent theoretical estimates and related experimental values. Our results favor a Λ-nucleus interaction with an inner repulsive core. The non-mesonic weak decay widths of Λ 4 H and Λ 4 He are reexamined on the basis of our measurements and updated knowledge of the mesonic decay processes. It is found that the non-mesonic decay of Λ 4 He predominantly takes place via the Λ + p → n + p process.

We observed resonant coherent excitation (RCE) of 1s electron to n=2 states in Ar17+ through measurements of the survived fraction of 390 MeV/u hydrogen-like Ar17+ channeled in a Si crystal. We adopted a totally depleted Si surface barrier detector as a target crystal as well as a probe of the energy deposition. The charge state of emerged ions was measured by a combination of a charge separation magnet and a 2D-position sensitive detector. We observed the RCE for planar channeled ions by tilting the target Si crystal from the direction of [1 1 0] axis in the (2 2 0) , (0 0 4) , and (1 1 1) planes. Prominent resonances at tilt angles under the resonance condition were observed. Moreover, each resonance profile is split into several lines due to the l·s interaction and the Stark effect originating in the static crystal field. The energy deposition in the crystal gives the information of the amplitude of the ion trajectory. The resonance peak position, intensity and width in the survived fraction of Ar17+ reflect the position dependent strength of the crystal field, the RCE and the electron loss probabilities. They are in good accord with our calculation of the transition energy and probability.

We have succeeded in observing the channeling of 290 MeV/u C 6+ ions in a Si crystal. Under 〈1 1 0〉 axial, and (0 0 4), (2 2 0) and (1 1 1) planar channeling conditions, energy loss of the channeled ion in the Si crystal was observed. We also calculated the trajectory dependent stopping power for planar channeling ions, which employs mean and local electron densities evaluated adopting the Moliere potential. Calculated energy loss spectra were found to reproduce the experimental results quite well.

Continuum x rays originated from radiative electron capture into continuum states (RECC) of relativistic Ne{sup 10+} ions have been observed. It has been found that the intensities of x rays decrease as their energy increases and the observed spectra show a clear edge which corresponds to the maximum energy transferred to free electrons under energetic projectile-ion collisions. The edge becomes dramatically sharp as the incident projectile energy decreases from 290 to 75 MeV/amu, indicating that the cross sections for RECC sharply increase at low projectile energies, which is in agreement with the theoretical expectation. {copyright} {ital 1997} {ital The American Physical Society}

Selective production of the doubly excited state in 464 MeV/u He-like Ar${}^{16+}$ ions was accomplished using three-dimensional resonant coherent excitation in a thin foil of silicon crystal. Through a coherent interaction with the periodic crystal field, the Ar${}^{16+}$ ions were resonantly excited sequentially from the ground state to the $1s2p$ (${}^{1}\phantom{\rule{-0.16em}{0ex}}P$) state and then $2{p}^{2}$ (${}^{1}\phantom{\rule{-0.16em}{0ex}}D$) state in a way analogous to two-color x-ray laser excitation. The periodic crystal fields of 10${}^{11}$ V/m in the projectile's frame are equivalent to the fields generated by x-ray lasers with photon energies of 3139.55 and 3286.95 eV and an energy flux of 10${}^{16}$ W/cm${}^{2}$. We confirmed the doubly excited state formation through observation of the subsequent collisional ionization, Auger ionization, and radiative deexcitation.

Results are reported on a lifetime measurement of Λ4H formed in 4He (stopped K−,π°) reaction. Decay of Λ4H was clearly identified by observing the monochromatic π− peak from the two-body decay ( Λ 4 H → 4 He + π − p x =132.9 MeV/c ). The lifetime of Λ4H was determined to be τ(Λ4H) = 194−26+24 ps from a distribution of time difference between the K− injection and π− emission.

Proton knockout reactions on carbon isotopes, p(9–16C,2p)8‐15B, at 250MeV/A were performed for systematic information on weakly to strongly bound 1p valence protons and deeply bound 1s protons. Various information such as energy gap between 1s and 1p orbits, widths of momentum distributions for 1s and 1p orbits, relative (p,2p) yields are obtained.

We report on the selective production of the 2s metastable state of 390-MeV u−1 H-like Ar17+ ions by the resonant coherent excitation (RCE). The RCE to the 2s state was achieved by using Stark mixing of n = 2 states under planar channeling conditions in a 1-m thick Si crystal. The population of the 2s state was quantitatively estimated from the ionization probability in a stripper foil installed 50 mm downstream of the crystal. The 2s population was found to be 0.05 of the total number of Ar17+ ions at the stripper. The result is in good agreement with a theoretical calculation performed with the density matrix approach.

We present a joint experimental and theoretical study of convoy-electron emission resulting from highly-charged-ion transport through carbon foils at moderately relativistic speeds. Energy spectra of electrons ejected at $0\ifmmode^\circ\else\textdegree\fi{}$ have been measured for 390 MeV/u hydrogen-like ${\mathrm{Ar}}^{17+}$ ions and 460 MeV/u $(\ensuremath{\beta}=v/c=0.74,\ensuremath{\gamma}=1.49)$ ${\mathrm{Fe}}^{25+}$ $(1s),$ ${\mathrm{Fe}}^{24+}$ ${(1s}^{2}),$ and ${\mathrm{Fe}}^{23+}$ ${(1s}^{2}2s)$ incident on carbon foils with thicknesses from 25 to $8700\ensuremath{\mu}{\mathrm{g}/\mathrm{c}\mathrm{m}}^{2}.$ Due to this unprecedented wide range of thicknesses, the sequential excitation and ionization of initially deeply bound electrons to highly excited states and continuum states can be followed in considerable detail. The analysis of the spectra is aided by simulations based on the classical transport theory which has been extended to relativistic energies and to multielectron projectiles. The motion of the projectile electron inside the solid target is calculated taking into account the Coulomb potential of the projectile ion and the multiple stochastic collisions with target cores and target electrons. Different phases of the convoy-electron emissions can be disentangled: direct ejection to the continuum, the transient buildup of an excited-state wave packet followed by ionization, and postionization modification of the continuum spectrum. We find good agreement between experiment and simulation for the evolution of charge states and the emission spectrum.

An extremely-thin Germanium crystal (0.8 μm-thick) has been firstly exploited in the resonant coherent excitation (RCE) experiment. The 460 MeV/u H-like Fe25+ ions were incident on the Ge crystal under the (220) planar channeling as well as non-channeling conditions. The RCE from 1s to 2p1/2 and 2p3/2 states were successfully observed as an enhancement of the x-ray fluorescence.

We studied the anisotropy of Ly-α x-rays from H-like Ar17+ ions excited by polarization-controlled resonant coherent excitation. The effects of fine-structure depolarization on the 2p1/2 and 2p3/2 states were experimentally demonstrated as a reduction in anisotropy of decay radiation.

We demonstrate the alignment of H-like and He-like heavy ions by three-dimensional resonant coherent excitation in a thin crystalline target. The projectile ions experienced a linearly polarized oscillating field in a crystal and were excited to a specific magnetic substate, forming the aligned 2P state. We prepared the different directions of the aligned states and observed the anisotropy of deexcitation x-ray emission, which was in good agreement with theoretical estimates.

We exploited the double resonance technique in three-dimensional resonant coherent excitation to the production of hollow He-like and Li-like heavy ions. The two K-shell electron were sequentially excited to the L-shell using two frequency components of the oscillating fields arising from the different arrays of atomic planes in a Si crystal.

Convoy electrons emitted from 416 MeV/u heliumlike Ar16+ ions excited by three-dimensional resonant coherent excitation (3D-RCE) have been explored. The 1s electron in the ground state was excited to the 2p state by a periodic crystal field during the passage through a Si crystal and released into the continuum by collisions with target atoms to form a cusp-shaped peak in the energy distribution, referred to as convoy electron. Under the resonance condition, we found not only enhancement of the convoy electron yield but also significant narrowing in the energy distribution, reflecting the initial bound state momentum distribution of the excited ions. This suggests that RCE is well-suited to study fast ion collisions involving the specific excited state.

We investigated resonant coherent excitation (RCE) of 445 MeV/u Li-like Ar15+ under the planar channeling and non-channeling conditions. The K-shell and L-shell excitations are observed as decreases in the survival fraction of the Ar15+ ions after passing through a thin Si crystal. RCE under the planar channeling condition provides the opportunity to study a strong static Stark effect on the Li-like system with K-shell or L-shell vacancy. Under the non-channeling conditions, the observed excitation energies and the reported theoretical calculations were in reasonable agreement.

X-ray spectra have been observed for the collision system of bare C6+, Ne10+, Si14+ and Ar18+ ions of 75-290 MeV/u with Be and C foil targets. The radiative electron capture into continuum states (RECC) of these projectiles is always noticeable. For 75 and 150 MeV/u Ar18+, we can also observe a peak due to radiative electron capture into the K-shell (K-REC) in addition to RECC. A small ridge corresponding to K-REC is discerned also for 75 MeV/u Si14+. These features reflect the energy and projectile charge dependence of the intensities of RECC and REC x-rays. The observed edge energies of RECC and peak energies of REC are consistent with estimated values based on energy conservation. The observed absolute intensities of these components are also compared with calculations.

Interactions of relativistic clothed heavy ions with solid targets have been studied for 390 MeV/u Ar17+ ions traversing carbon foils of various thicknesses through measurements of the convoy electrons. The electron energy spectra at 0° were obtained by a magnetic analyzer combined with a Si surface barrier detector with a depletion layer of 5 mm. The peak widths of the convoy electrons in the laboratory frame have been found to decrease as the target thickness is increased from 25 to about 500 µg/cm2, and broaden for thicker targets due to multiple scattering.

We measured the energy loss of charge-frozen clothed ions (i.e., partially stripped ions which maintain their charge states throughout the passage) in a Si solid employing a totally depleted silicon detector with 4.1 µm thickness as a target, to measure the energy deposition of 390 MeV/u Ar17+ directly. Under the present conditions, the probability of the electron loss is not so large, and that of the electron capture is negligibly small. Accordingly, the energy loss of charge-frozen Ar17+ ions in a rather thick target can be measured. Charge states of ions transmitted through the target were observed by a 2D-position sensitive detector in coincidence with the energy deposition. We have obtained an effective charge of Ar17+ ions for the stopping power, as Zeff = 17.36 (±0.03).

Heavy-ion irradiation systems were designed and constructed at two cyclotron facilities in Japan for use in various fields of radiation physics and radiation biology. A 135 MeV/u carbon beam as well as 12 MeV/u carbon and helium-3 beams were first used in experiments. We have established a systematic method for heavy-ion dosimetry at both high and low incident energies involving measurements of fluences. We also obtained differential W values (w) of air for those beams by comparing the results of fluence measurement dosimetry with ionization chamber dosimetry. The differential W values of air were found to be 36.2 +/- 1.0, 34.5 +/- 1.0, and 33.7 +/- 0.9 eV for 6.7 MeV/u carbon ions, 10.3 MeV/u 3He ions, and 129.4 MeV/u carbon ions, respectively. The w value for high-energy heavy ions approaches the W value for high-energy electron or photon beams. In ionization chamber dosimetry for a heavy-ion beam, we found a track-size effect. A difference in the track sizes of heavy ions in the gas and solid phases affected the output current of the ion chamber in the case of high-energy heavy ions.

Alpha– 16 O correlation measurements have been performed to investigate whether the projectile breakup process takes place sequentially or directly in the 20 Ne+ 40 Ca reaction at 92, 149 and 213 MeV. For the three-body final channel α+ 16 O(g.s.)+ 40 Ca(g.s.) (elastic breakup channel), which has much larger cross section than the other channels, the coincidence events have been analyzed. By examining carefully the relative energy spectra between α and 16 O, it was found that the sequential breakup process via the excited states of 20 Ne at 5.78 (J π = 1, K π = 0), 6.72 (0 + , 0 2 + ), 7.17 (3 - , 0 - ), 8.78 (6 + , 0 1 - ), 10.26 (5 - , 0 - ) and 11.95 (8 + , 0 1 + ) MeV was dominant at the all incident energies. The direct breakup process which proceeds without any concern with the excited states of 20 Ne has not been observed with the sensitivity of the present measurement.

We have developed a parallel beam suitable for channeling experiments with relativistic heavy ions at HIMAC (Heavy Ion Medical Accelerator in Chiba). To observe channeling phenomena, we used a silicon surface barrier detector (SSD) as a sample crystal and as a detector for the energy loss in itself. Further, we measured the angular spread of the beam transmitted through the SSD by a position sensitive detector (PSD) placed downstream of the SSD. Under axial and (111), (220) and (004) planar channeling conditions, we observed that the energy loss of the channeled ions in the SSD became almost a half and their angular spread was also reduced.