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The first elastic electron scattering has been successfully performed at the self-confining radioactive-isotope ion target (SCRIT) facility, the world's first electron scattering facility for SCRIT technique achieved high luminosity (over 10^{27} cm^{-2} s^{-1}, sufficient for determining the nuclear shape) with only 10^{8} target ions. While ^{132}Xe used in this time as a target is a stable isotope, the charge density distribution was first extracted from the momentum transfer distributions of the scattered electrons by comparing the results with those calculated by a phase shift calculation.

We have constructed the SCRIT electron scattering facility at RIKEN in order to realize electron scattering off unstable nuclei. Because electron scattering is the most powerful and reliable tool to study the internal structure of the atomic nuclei as demonstrated for many stable nuclei in the latter half of the 20th century, actualization of electron scattering for the unstable nuclei has been long awaited. Recently, we have performed a series of elastic electron scattering experiments with $^{132}$Xe target. The high luminosity of around 10$^{27}$~cm$^{-2}$s$^{-1}$ which is a minimum-requirement for electron scattering is achieved with using only 10$^8$ target ions. By comparing with a DWBA calculation assuming the two-parameter Fermi distribution as the nuclear charge density distribution, it is found that a root-mean-square of radius is consistent with that from the measurement of X-ray of muonic atom and an information of surface shape of $^{132}$Xe nucleus is extracted for the first time.

The SCRIT electron scattering facility, aiming at electron scattering off short-lived unstable nuclei, has been constructed at the RIKEN RI Beam Factory. This facility consists of a racetrack microtron (RTM), an electron storage ring (SR2) equipped with the SCRIT system, and a low-energy RI separator (ERIS). SCRIT (self-confining radioactive isotope ion targeting) is a novel technique to form internal targets in an electron storage ring. Experiments for evaluating performance of the SCRIT system have been carried out using the stable 133Cs1+ beam and the 132Xe1+ beam supplied from ERIS. Target ions were successfully trapped in the SCRIT system with 90% efficiency at a 250 mA electron beam current, and luminosity exceeding 10 26 /(cm2 s) was maintained for more than 1 s. Electrons elastically scattered from the target ions were successfully measured. Applicability of the SCRIT system to electron scattering for unstable nuclei has been established in experiments.

The strangeness photoproduction processes near the threshold have been intensively studied by measuring K + in reactions such as γ + p → K + + Λ ( Σ 0 ) . There has been no reliable data on the neutron and as a consequence theoretical investigation suffered seriously from the lack of the data. We have an effort to measure the γ + d → K 0 ( Λ ) + X reaction in the π + π − ( p π − ) decay channel of K S 0 (Λ) using a liquid D2 target and internally-tagged photon beams ( E γ = 0.80 – 1.08 GeV ) at Research Center for Electron Photon Science (ELPH), Tohoku University. We have renewed the spectrometer (NKS2) and took data with a liquid D2 target in 2005–2007. More recently, we took data in 2010 after a detector upgrade in the vertex region to substantially increase the acceptance. The results of Λ single measurements on a deuterium target were obtained for differential cross-section as a function of momentum, as a function of angle, and integrated cross-section as a function of beam energy. The results are compared with recent theoretical studies: Isobar models (Kaon-MAID and Saclay-Lyon A) and a Regge-plus-Resonance model.

Photoproduction of the neutral kaon on the deuteron has been investigated at the Research Center for Electron Photon Science, Tohoku University. We constructed the Neutral Kaon Spectrometer-2 for the detection of charged particles from the decay of the neutral kaon and the hyperon. We obtained a momentum distribution of K 0 with the inclusive measurement. It was consistent with the previous measurement. The total cross section of γ + d → K 0 + Λ + p was estimated from the measured integral cross section of γ + d → Λ + X. The total cross section with respect to the photon energy was compared with the theoretical calculations. It favored the Saclay-Lyon A model calculation with the ratio of the neutral to charged coupling constants of the axial-vector meson, K 1, as ~ −1.5. The energy dependence and the magnitude of the total cross section were similar to the total cross section of γ + p → K + Λ.

Double charged pion photoproductions from the deuteron have been studied at Research Center for Electron Photon Science (ELPH), Tohoku University. Tagged photon beams in an energy range of 0.67 ≤ E γ ≤ 1.08 GeV were impinged on the liquid deuteron target. Produced charged particles were observed with the Neutral Kaon Spectrometer2 (NKS2). The γ d → π + π − d process was clearly separated among the three charged tracks. We obtained the photon energy dependence of the normalized yields of this process.

The energy of tagged photons, which were provided from the internal photon tagging system of the Laboratory of Nuclear Science, Tohoku University, has been calibrated using the d(γ,π−pp) reaction. Charged pions and protons in the final state were detected with the Neutral Kaon Spectrometer (NKS2). Photon energies were obtained from the reaction of d(γ,π−pp). The derived photon energy was consistent with the design of the tagger system and the previous measurement using electron-positron pair production. The consistency demonstrates the performance of NKS2 and the capability of the photon energy calibration using d(γ,π−pp).

We have established a novel method which make electron scattering off short-lived radioactive nuclei come into being. This novel method was named SCRIT (Self-Confining RI ion Target). It was based on the well known "ion trapping" phenomenon in electron storage rings. Stable nucleus, 133 Cs , was used as target nucleus in the R&D experiment. The luminosity of interaction between stored electrons and Cs ions was about 1.02(0.06) × 1026 cm -2 s -1 at beam current around 80 mA. The angular distribution of elastically scattered electrons from trapped Cs ions was measured. And an online luminosity monitor was used to monitor the change of luminosity during the experiment.

A new beam line for photonuclear reaction experiments using tagged photons has been constructed to take advantage of the completion of the 1.2-GeV STretcher Booster (STB) ring at the Laboratory of Nuclear Science (LNS), Tohoku University. A photon tagging system was installed at the end of the new beam line. It provides bremsstrahlung tagged photon beams in an energy range from 0.2 E 0 to 0.8 E 0 MeV at the incident electron energy E 0 with an energy resolution of Δ E / E ≈ 10 - 2 . The tagged photon intensity I ⩽ 5 × 10 6 photons / s is available for typical photonuclear reaction experiments. We introduce the basic parameters of the tagged photons by showing the commissioning data.

Proton energy spectra of the 197Au(e,p) reaction were measured in the region between 17 and 30 MeV at three angles: 40°, 90° and 140°. Two prominent bumps were observed in the (γ,p) spectra converted using virtual photon theory. The higher-energy bump shifts with photon energies and the lower-energy one stays at 10.5 MeV. The higher-energy bump is much larger at 40° than at 140°; on the contrary the angular dependence of the lower-energy bump is small. Neither bump can be described by a statistical calculation. A calculation of a microscopic shell model shows that the lower-energy bump is attributed to the decay of proton-particle–neutron-hole pairs in the T> states, leaving a neutron hole around the Fermi surface. The higher-energy bump can be ascribed to the direct–semidirect mechanism. This paper gives the solution to a part of the long-standing question about the origin of photo-proton emission in heavy nuclei.

New electron scattering measurements have been made that extend data on the ${}^{3}\mathrm{He}$ elastic magnetic form factor up to ${Q}^{2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}42.6{\mathrm{fm}}^{\ensuremath{-}2}$. These new data test theoretical conjectures regarding non-nucleonic effects in the three-body system. The very small cross sections, as low as ${10}^{\ensuremath{-}40}{\mathrm{cm}}^{2}/\mathrm{sr}$, required the use of a high-pressure cryogenic gas target and a detector system with excellent background rejection capability. No existing theoretical calculation satisfactorily accounts for all the available data.

The self-confining RI target (SCRIT) electron scattering facility has been constructed at RIKEN RI Beam Factory. The commissioning experiment was performed, and the luminosity was achieved to around 1027 cm−2 s−1 with stable ions at a 250 mA electron beam current. For the electron scattering with short-lived unstable nuclei, the radioactive isotope production was started at electron-beam-driven RI separator for SCRIT. Furthermore, new devices, the electron spectrometer window frame spectrometer for electron scattering and the cooler buncher system were constructed. After the setup of new devices, a first electron scattering experiment with short-lived nuclei will be performed soon.

The energy spectra and angular distributions of protons from the 12C(e,e′p) coincidence reaction have been measured at azimuthai angles of φp= −45° and −135° out of the scattering plane, at energy transfer of 40 MeV and momentum transfer of 0.35 fm−1 (69 MeV/c). The longitudinal-transverse interference term, as well as the non-interference term of the (e,e'p0) cross section have been obtained, and the transition amplitudes are deduced in the LS coupling basis. The cross sections are compared with an RPA calculation. The photo-reaction cross section derived from the transverse term is in reasonable agreement with previous experimental results.

The absolute electrofission cross sections of Au and Ta were measured in the energy interval 40-250 MeV. Pronounced inflexions of the (e,f) curves are observed for both Au and Ta around 200-220 MeV, which are signatures of structures in the corresponding photofission cross-section curves. We show that these ( gamma ,f) structures are related to peculiarities of the thermalization process.

We report precision {sup 1}H(e, e{sup '{pi}+})n measurements in the {Delta}(1232) resonance at Q{sup 2}=0.127(GeV/c){sup 2} obtained at the MIT-Bates out-of-plane scattering facility. These are the lowest, but nonzero, Q{sup 2} measurements in the {pi}{sup +} channel. The data offer tests of the theoretical calculations, particularly of the background amplitude contributions. The chiral effective field theory and Sato-Lee model calculations are not in agreement with this experiment.

The absolute electrofission cross sections of Au and Ta were measured in the range 25--180 MeV. The deduced photofission cross section shows, for both Au and Ta, a pronounced dip around the photopion threshold ([similar to]140 MeV). This ([gamma],[ital f]) dip is interpreted as a consequence of a probable photopion absorption in a stopped pion regime.''

The spectra of protons and α-particles form the (e, p) and (e, α) reactions for 63,65Cu nuclei have been measured at 90° for incident electron energies ranging 14 to 60 MeV. The differential cross sections of the (γ, p) and (γ, α) reactions are deduced from the yield curves obtained from these energy spectra, using virtual- photon theory. The (γ, p0) differential cross sections are also deduced. The (γ, p) cross sections are in good agreement with those calculated from the (γ, n) cross sections using a statistical theory which includes the isospin-splitting effect, but in order to get the (γ, p0) cross sections, the direct-semidirect effects must also be included.

A novel technique for forming internal targets, named SCRIT (Self-Confining RI Ion Target), has been developed, which can make electron scattering off short-lived radioactive nuclei possible in an electron storage ring. SCRIT confines the ions of interest by utilizing the “ion trapping” phenomenon in the electron storage ring. Approximately 107 stable 133Cs ions were trapped in a three-dimensional configuration along the electron beam axis at an electron beam current of 75mA. The angular distribution of the electrons scattered from the trapped 133Cs ions was successfully measured, and a collision luminosity of 1026/(cm2 s) was achieved.

We carried out a demonstrative electron scattering experiment using a novel ion-trap target exclusively developed for short-lived highly unstable nuclei. Using stable $^{133}\mathrm{Cs}$ ion as a target, this experiment completely mimicked electron scattering off short-lived nuclei. Achieving a luminosity higher than ${10}^{26}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}2}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$ with around only ${10}^{6}$ trapped ions on the electron beam, the angular distribution of elastic scattering was successfully measured. This experiment clearly demonstrates that electron scattering off rarely produced short-lived nuclei is practical with this target technique.

A novel internal target has been developed, which will make electron scattering off short-lived radioactive nuclei possible in an electron storage ring. An "ion trapping" phenomenon in the electron storage ring was successfully utilized for the first time to form the target for electron scattering. Approximately 7 x 10(6) stable 133Cs ions were trapped along the electron beam axis for 85 ms at an electron beam current of 80 mA. The collision luminosity between the stored electrons and trapped Cs ions was determined to be 2.4(8) x 10(25) cm(-2) s(-1) by measuring elastically scattered electrons.

The absolute electrofission cross section of {sup 208}Pb was measured in the energy range 35--250 MeV, and the photofission cross section was deduced by means of the virtual-photon technique. A structure observed in the ({gamma},{ital f}) curve, around 200 MeV, was interpreted on the basis of recent calculations for the thermalization process which were performed in the framework of the intranuclear cascade model.

Experimental details of a virtual Compton scattering (VCS) experiment performed on the proton at the MIT-Bates out-of-plane scattering facility are presented. The VCS response functions ${P}_{LL}\ensuremath{-}{P}_{TT}/\phantom{{P}_{TT}\ensuremath{\varepsilon}}\ensuremath{\varepsilon}$ and ${P}_{LT}$ have been measured at ${Q}^{2}=0.057\phantom{\rule{0.28em}{0ex}}{\mathrm{GeV}}^{2}/{c}^{2}$. The generalized electric and magnetic polarizabilities, $\ensuremath{\alpha}({Q}^{2})$ and $\ensuremath{\beta}({Q}^{2})$, and the mean-square electric polarizability radius$\ensuremath{\langle}{r}_{\ensuremath{\alpha}}^{2}\ensuremath{\rangle}$ are obtained from a dispersion analysis of the data. The results are in good agreement with $O({p}^{3})$ heavy baryon chiral perturbation and indicate the dominance of mesonic effects in the polarizabilities.

Electron scattering is a superior method to investigate the internal structure, such as charge distribution, of atomic nuclei. Most of the radii of nuclei were determined unambiguously by that. However, radioactive isotopes (RI) which recently came up to a major research interest have not been accessible due to the difficulty in making fixed targets and taking measurements before they decay. We proposed a conceptually new target called SCRIT (Self‐Confining Radioactive Isotope ion Target) as opposed to a collider method. The luminosity expected for SCRIT is inevitably low (typically on the order of 1.E+27/cm2/s) and a large acceptance detector system is required. We plan to perform a coincidence measurement using an electron arm and a recoil ion detector which needs to be developed. Current status of the ion trapping with a prototype SCRIT and the background measurement results in an electron storage ring will be discussed.

We have studied the quasielastic He-3(e,e(')p)H-2 reaction in perpendicular coplanar kinematics, with the energy and the momentum transferred by the electron fixed at 840 MeV and 1502 MeV/c, respectively. The He-3(e,e(')p)H-2 cross section was measured for missing momenta up to 1000 MeV/c, while the A(TL) asymmetry was extracted for missing momenta up to 660 MeV/c. For missing momenta up to 150 MeV/c, the cross section is described by variational calculations using modern He-3 wave functions. For missing momenta from 150 to 750 MeV/c, strong final-state interaction effects are observed. Near 1000 MeV/c, the experimental cross section is more than an order of magnitude larger than predicted by available theories. The A(TL) asymmetry displays characteristic features of broken factorization with a structure that is similar to that generated by available models.

A novel method has been established to realize the experiment of electron scattering off short-lived nuclei. The method was based on the well known "ion trapping" phenomenon in electron storage rings. In the R&D experiments at Kyoto University, stable nucleus, 133Cs, was employed as the target nucleus. The luminosity of scattering experiment was nearly 1026 cm−2s−1 at electron beam current around 75 mA. The angular distribution of elastically scattered electrons from trapped Cs ions was measured and the result was well fitted by theoretical calculation. It was indicated that higher luminosity can be reached with larger electron beam current.

Measurements of the (2)H((-->)e,e(')p)n reaction were performed with the out-of-plane magnetic spectrometers (OOPS) at the MIT-Bates Linear Accelerator. The longitudinal-transverse, f(LT) and f(')(LT), and the transverse-transverse, f(TT), interference responses at a missing momentum of 210 MeV/c were simultaneously extracted in the dip region at Q2 = 0.15 (GeV/c)(2). In comparison to models of deuteron electrodisintegration, the data clearly reveal strong effects of relativity and final-state interactions and the importance of two-body meson-exchange currents and isobar configurations. We demonstrate that such effects can be disentangled by extracting these responses using the novel out-of-plane technique.

An optical-pumping system of rubidium atoms for a laser-driven polarized deuteron target was constructed. The density and polarization of the rubidium atoms were measured using Faraday rotation. The rotation angle was determined within an error of 0.01°. Our preliminary result showed a polarization of 0.4 at a gas thickness of 4×1013 atoms/cm2.

The (e,..cap alpha..) cross section in /sup 90/Zr has been measured at incident electron energies from 13.5 MeV to 66.5 MeV for ..cap alpha.. particles between 6.9 and 16.8 MeV. The (..gamma..,..cap alpha..) cross section was deduced from it assuming both E1 interaction and E2 interaction. The angular distribution of the (..gamma..,..cap alpha../sub 0/) cross section and an experiment using the bremsstrahlung plus electron beam make it clear that the E1 interaction is dominant over all the present energy range. The (..gamma..,..cap alpha..) cross section extracted by using E1 virtual photon spectra has a large bump above the excitation energy of 30 MeV in addition to a bump in the giant dipole resonance region. The (..gamma..,..cap alpha../sub 0/) cross section also has a bump at the giant dipole resonance which exhausts most of the (..gamma..,..cap alpha..) cross section in that region. The compound nucleus model was used successfully to explain the bump at the giant dipole resonance. The cross section above 30 MeV is discussed in terms of the pre-equilibrium ..cap alpha.. emission process combined with the quasi-deuteron model.

The energy spectra of α-particles and the (e, α) cross section for 24 Mg were measured with electrons in the energy region from 14 to 30 MeV to investigate α-particle emission from the giant resonance. The ( γ , α 0 ) and ( γ , α ) cross sections for 24 Mg were deduced from energy spectra and the (e, α) cross section using the virtual photon technique. E1 and E2 components were obtained from the analysis of angular distributions. A peak of 20 MeV seen in the (γ, n), (γ, p) and absorption cross sections is not observed in the (γ, α) cross section. The cross sections are explained by the statistical model with isospin mixing in the measured energy region, except around 20 MeV.

The electrofission angular distribution of 208Pb was measured at 35 MeV. The strong observed 45 degrees -peaked anisotropy would indicate that (2+,0) states dominate the fission-channel spectrum at the top of the fission barrier.

The D(e,e'p) coincidence cross section was measured at angles out of the plane, at an excitation energy of approximately 18 MeV and a momentum transfer of 0.33 fm/sup -1/. This is the first reported measurement of the longitudinal-transverse and transverse-transverse interference terms of the electrodisintegration cross section of the deuteron. The longitudinal plus transverse cross section is also reported. The results are in good agreement with a theoretical calculation carried out with use of the Paris potential.

The 65 Cu(e, e'p 0 ) coincidence cross section at θ e' =30° and φ p =-90° is measured at θ p =0°–180° in the giant dipole resonance energy region. The present geometrical setup is selected to enhance the Coulomb multipole strength. The angular distribution obtained is decomposed into a Legendre series and analyzed by the theory of Kleppinger and Walecka. The result shows the success in geometrically obtaining the contribution of electric quadrupole excitation.

The energy spectra and angular distribution of protons from the 40 Ca(e, e'p 0 ) coincidence reaction have been measured at angles out of the scattering plane, in the region of the giant dipole resonance. The longitudinal-transverse interference term of the electroexcitation cross section, as well as the non-interference term, have been obtained. These cross sections are in reasonable agreement with those derived from (γ,p 0 ) and (p, γ 0 ) reactions using the theory based on the two-step process through the giant resonances. The results are compared with the particle-hole model and the continuous RPA calculations.

The differential cross sections of the (e, e'p) reactions for 51V and 59Co have been measured at 90° over the region of excitation corresponding to the electric giant dipole resonance. The (γ, p) cross sections of these nuclei were deduced from differential cross sections assuming isotropic angular distributions of protons. The results are compared with the (γ, n) cross sections, and are used to obtain strengths of the T giant dipole states separately by using the statistical theory. For each nucleus the ratio of the separated strengths and the splitting energy are consistent with those expected by the isospin formalism.

The π + π − photoproductions on the proton and deuteron have been studied in a photon energy range of 0.8–1.1 GeV at the Laboratory of Nuclear Science, Tohoku University. Charged pions and protons were detected using Neutral Kaon Spectrometer. We obtained the cross sections for the p ( γ , p π + π − ) and d ( γ , p π + π − ) n . The quasi-free process with a neutron spectator was extracted by the neutron momentum cut of p n > 0.3 GeV / c . The cross section for the Δ + + Δ − production was deduced in the non-quasi-free process of the γ d → p n π + π − . It was 13.4 ± 0.4 μb at E γ = 0.82 GeV .

The absolute electrofission cross section of Au and Ta was measured in the energy interval 40--250 MeV. Pronounced inflexions of the ([ital e],[ital f]) curves are observed for both Au and Ta around 200--220 MeV, which are signatures of structures in the corresponding photofission cross-section curves. We show that these ([gamma],[ital f]) structures are originated in the stage of preequilibrium emissions in the nuclear thermalization process. The question associated to a possible connection between thermalization effects and competing photoexcitation mechanisms is addressed.

An approach for the delineation of the compound nucleus excitation energy, from the photofission cross section at intermediate energies, is worked out. An application for $^{182}\mathrm{W}$, Au, and Ta is presented. The potential of this formalism, for the study of pion properties inside the nuclear medium, is discussed. \textcopyright{} 1996 The American Physical Society.

Experimental results are presented for the cross sections measured at 90� of the reactions 42Ca(y, p), 42Ca(y, Po) and 42Ca(y, 1(0) between excitation energies 16 and 28 MeV.