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We constructed the SCRIT (Self-Confining Radioactive Ion Target) electron scattering facility to realize electron scattering off short-lived unstable nuclei at RIKEN in Japan. Electron scattering is one of the most powerful and reliable tools to study structures of atomic nuclei. However, it has been extremely difficult to apply electron scattering to unstable nuclei because of target preparation problems. SCRIT is a novel ion-trapping technique that achieves high luminosity of more than 1027 cm-?2s-?1 with a small amount of target ions. Following completion of the facility, a series of commissioning experiments of the entire facility with several stable nuclear targets, including 208Pb and 132Xe, were performed. Momentum transfer distributions of elastic scattering from those targets were successfully measured at several electron beam energies, and the charge density distribution of the 132Xe nucleus was extracted for the first time.

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 (Self-Confining Radioactive-Isotope Ion Target) electron scattering facility has been constructed at the RIKEN RI Beam Factory. In the commissioning experiment, the ion-trapping properties of the SCRIT system were studied using stable ions. By using an electron spectrometer, the momentum transfer distribution of the electron elastic scattering of $^{132}$Xe was measured at 150, 200, and 300~MeV, and the charge density distribution was deduced. During the measurements, a luminosity of $1.8 \times$10$^{27}$~cm$^{-2}$s$^{-1}$ was achieved with a 250-mA electron beam and only 10$^8$ trapped ions. Production of RIs has begun in an electron-beam-driven RI separator, and developments are underway to increase the production rate of short-lived nuclei. Soon, measurements of electron elastic scattering by short-lived nuclei will be performed.

The SCRIT (Self-Confining RI Ion Target) facility has been constructed at RIKEN to make the electron-RI scattering experiment possible for the first time in the world. At SCRIT, the angular momentum distribution of scattered electrons is measured by WiSES (Window-frame Spectrometer for Electron Scattering) which consists of a dipole magnet and front/rear drift chambers, covering a solid angle of $\sim$80 mSr with an intrinsic momentum resolution of $\Delta p/p\sim10^{-3}$. Also the luminosity of the electron-RI scattering is estimated from bremsstrahlung photons measured by LMon (Luminosity Monitor) to obtain the absolute cross-section of the scattering. The LMon consists of a CsI calorimeter to measure the photon energy, and plastic fiber scintillators to measure the 2D hit distribution of the bremsstrahlung photons. In 2015-2016 the first physics experiment has been performed using $^{132}\rm Xe$ target, then the luminosity and angular distributions were successfully measured at the electron beam energy of 150-300 MeV, achieving a luminosity above $10^{27}cm^{-2}$s$^{-1}$. In this article, we present the performances of the WiSES and LMon detectors obtained by using the $^{132}\rm Xe$ experiment data.

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.

Photoproduction of the K 0 from the deuteron and the carbon nucleus has been investigated at the Laboratory of Nuclear Science, Tohoku University in Sendai. The Neutral Kaon Spectrometer and the Neutral Kaon Spectrometer 2 were developed to detect π + π − pairs coming from the decay of the K S 0 . The resulting K 0 momentum spectra for inclusive K 0 photoproduction were compared with theoretical calculations based on isobar models for γ + n → K 0 + Λ , utilizing the spectator hypothesis. An upgrade of the inner detectors to enhance the acceptance for the coincidence measurement of the K S 0 and Λ is underway. We expect that the exclusive and kinematically complete measurement of the reaction will provide us with direct access to the center-of-mass observables that are important for further understanding the mechanism for strangeness photoproduction.

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.

The total cross sections for the π+π− photoproduction on the deuteron were measured in an energy range of 0.8 to 1.1 GeV. The obtained total cross section for the quasi-free π+π− photoproduction on the deuteron was about 60 % of those on the free proton. The cross section for Δ++Δ− photoproduction was derived from the non-quasi-free π+π− photoproduction events. It was smaller than the previous data.

Toshimi Suda1 , Akitomo Enozokizono2, Masahiro Hara3, Yuji Haraguchi4, Sin’ichi Ichikawa3, Kazuyoshi Kurita2, Saki Matsuo2, Tetsuya Ohnishi3, Tadaaki Tamae1, Mamoru Togasaki2, Kyo Tsukada1,Teruaki Tsuru1, Shuo Wang5, Shunpei Yoneyama1 and Masanori Wakasugi3 1Research Center for Electron-Photon Science, Tohoku University, 1-2-1 Mikamine, Sendai, 981-0928, Japan 2Department of Physics, Rikkyo University, Ikebukuro, Tokyo, 171-8501, Japan 3Nishina Center, RIKEN, Wako, Saitama,351-0198, Japan 4Department of Electrical Engineering, Nagaoka University of Technology, Nagaoka, Niigata, 940-2137, Japan 5School of Space Science and Physics, Shandong University, Weihai, China

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.

The γ n → K 0 Λ process plays an important role in the study of strangeness production by the electromagnetic interaction. We have investigated the quasi-free production reaction on a 12 C target in the threshold region ( E γ = 0.8 – 1.1 GeV ) at the Laboratory of Nuclear Science, Tohoku University. Preliminary results are presented.

A single-sided N-type silicon microstrip detector (SSD) was directly irradiated by a 200 MeV electron beam in order to examine radiation hardness. The leakage current increased linearly with the fluence up to 5×10 14 /cm 2 . The SSD efficiency began to drop at 2×10 14 /cm 2 , but was recovered by increasing the bias to 150 V and was maintained up to 3×10 14 /cm 2 . Noise figures increased slightly, but were within acceptable levels. Our results show that SSDs can operate up to a 200 MeV electron fluence of 3×10 14 /cm 2 without any significant degradation in performance.

The measurement of neutral kaon photoproduction in the threshold region is in progress at Laboratory of Nuclear Science, Tohoku University. One of the purpose of the experiment is to study electromagnetic strangeness production mechanism, which is necessary for hypernuclear spectroscopy by electromagnetic probes. We have observed K 0 's produced on a carbon target in a commissioning run. Data taking will start in 2003.

We report on the design and performance of compact detector packages currently installed in the four magnetic out-of-plane spectrometers for electron scattering experiments at the MIT-Bates Linear Accelerator Center. The detector packages have been designed to meet the mechanical requirements arising from out-of-plane particle detection. They offer good trajectory and momentum reconstruction, particle identification and time-of-flight measurements for electrons, pions, protons, and deuterons with large momentum bites and in broad kinematical ranges and high luminosities. The detectors have so far been used with great success in out-of-plane measurements of 12 C ( e → , e ′ p ) , 2 H ( e → , e ′ p ) , virtual Compton scattering below pion threshold and in studies of the N → Δ transition in both exclusive reaction channels 1 H ( e → , e ′ p ) π 0 and 1 H ( e → , e ′ π + )n .

Masashi Kaneta1, Brian Beckford1, Petr Bydžovský2, Takeshi Fujibayashi1, Takao Fujii1, Yu Fujii1, Kenta Futatsukawa1, Toshiyuki Gogami1, Yuncheng Han3, Osamu Hashimoto1 ∗, Kentaro Hirose4, Kenji Hosomi1, Ryotarou Honda1, Aran Iguchi1, Takatsugu Ishikawa4, Hiroki Kanda1, Yusuke Kaneko1, Yuma Kasai1, Taito Kawasaki1, Chigusa Kimura1, Shogo Kiyokawa1, Takeshi Koike1, Kazushige Maeda1, Nayuta Maruyama1, Masao Matsubara1, Koji Miwa1, Yohei Miyagi1, Sho Nagao1, Satoshi N. Nakamura1, Takashi Nishizawa1, Akira Okuyama1, Miloslav Sotona2,∗, Tadaaki Tamae4, Hirokazu Tamura1, Kyo Tsukada1, Nobu Terada1, Tieshan Wang3, Fumiya Yamamoto1, Takeshi O. Yamamoto1, and Hirohito Yamazaki4 (the NKS2 collaboration)

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.

Proton-proton bremsstrahlung events were measured at 400 MeV proton energy. Two arm spectrograph and a liquid-hydrogen target system with well tuned beam provided good event identification.

A new beam line to allow parasitic experiments in two separate experimental halls has been installed. The total length of the beam line is about 80 m. Two achromatic 90° deflecting systems have been incorporated. For the beam delivered to the second experiment, the beam diameter was 2 mm and the emittance was 1 mm mrad. The duty factor was reduced to an average of 50% from 80%. This decrease was satisfactorily recovered using a deflector system synchronized with the beam pulse. The tagged photon beam, and experimental conditions were significantly improved when the transported beam was used. Successful parasitic experiments involving electron scattering and tagged photon experiments have now been demonstrated.

The electrofission cross section of $^{182}\mathrm{W}$ was measured in the range 80--180 MeV. A pronounced inflexion, corresponding to a sharp structure in the (\ensuremath{\gamma},f) curve, shows up around 140 MeV. A photofission model, based on a photopion-deuteron reabsorption process, was worked out to explain this finding. Good agreement between calculation and experimental data was achieved.

The SCRIT electron scattering facility is under construction at the RIKEN RI Beam Factory. This is the worlds first facility dedicated to the study of the structure of short-lived nuclei by electron scattering, which has been a long-standing dream for nuclear physics. A novel Self-Confining RI Target (SCRIT) technique makes this challenging research possible. A series of test experiments using stable nuclei performed at this partially completed facility show that the collision luminosity between electron beam and target nucleus reaches 10^27cm^-'2s^-'1, which is required for an elastic electron scattering measurement to determine the charge density distribution of the target nucleus. The first electron scattering for unstable Sn isotopes will take place in the year 2014. Nuclear Physics at the SCRIT Electron Scattering Facility

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.

Differential cross sections and analyzing powers for the proton-proton bremsstrahlung have been measured at 389 MeV incident energy. At the present kinematical conditions, an enhancement of the cross sections due to the Δ current contribution is predicted. The measured cross sections are larger than the theoretical predictions including the Δ current contribution.

The elementary photo-strangeness production process has been intensively studied based on the high-quality data of the charged kaon channel, γ + p → K+ + Λ(Σ0). However, there had been no reliable data for the neutral kaon channel γ + n → K0 + Λ(Σ0) and the theoretical investigations suffer seriously from the lack of the data. In order to have reliable data for the neutral kaon photo-production data, substantial effort has been made to measure the γ + n → K0 + Λ process in the π+π- decay channel, using a liquid deuterium target and a tagged photon beam (Eγ = 0.8-1.1 GeV ) in the threshold region at the Laboratory of Nuclear Science (LNS), Tohoku University. We have taken exploratory data quite successfully with the use of Neutral Kaon Spectrometer (NKS) at LNS-Tohoku in 2003 and 2004. The data is compared to theoretical models and it indicates a hint that the K0 differential cross section has a backward peak in the energy region. The second generation of the experiment, NKS2, is designed to extend the NKS experiment by considerably upgrading the original neutral kaon spectrometer, fully replacing the spectrometer magnet, tracking detectors and all the trigger counters. The new spectrometer NKS2 has significantly larger acceptance for neutral kaons compared with NKS, particularly covering forward angles and much better invariant mass resolution. The estimated acceptance of NKS2 is three (ten) times larger for [Formula: see text] than that of NKS. The spectrometer is newly constructed and installed at the Laboratory of Nuclear Science, Tohoku University in 2005. The deuterium target data was taken with tagged photon beam in 2006-2007. We will report recent results of NKS2 in this paper. Additionally, a status of the upgrade project that gives us larger acceptance and capability of K0 + Λ coincidence measurement will be presented.

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.

The photoproduction process of neutral kaons on a liquid deuterium target is investigated near the threshold region, ${E}_{\ensuremath{\gamma}}=0.8\text{\ensuremath{-}}1.1$ GeV. ${K}^{0}$ events are reconstructed from positive and negative pions, and differential cross sections are derived. Experimental momentum spectra are compared with those calculated in the spectator model using a realistic deuteron wave function. Elementary amplitudes as given by recent isobar models and a simple phenomenological model are used to study the effect of the new data on the angular behavior of the elementary cross section. The data favor a backward-peaked angular distribution of the elementary $n(\ensuremath{\gamma},{K}^{0})\ensuremath{\Lambda}$ process, which provides additional constraints on current models of kaon photoproduction. The present study demonstrates that the $n(\ensuremath{\gamma},{K}^{0})\ensuremath{\Lambda}$ reaction can provide key information on the mechanism of the photoproduction of strangeness.

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.