No abstract available

No abstract available

[en] In this paper, K sup(π)=1/2⁺ rotation bands (0.58 MeV 1/2⁺, 0.98 MeV 3/2⁺, 1.96 MeV 5/2⁺ and 2.74 MeV 7/2⁺) are reported, which are weakly excited in electron scattering. Ground rotation band and K sup(π)=1/2₁⁺ rotation band of ²⁵Mg, which are strongly excited by ²⁴Mg (d,p) reaction and others, can be considered to possess the internal state that each odd neutron occupies Nilsson orbit No.5 or No.9. If the transition to K sup(π)=1/2⁺, rotation band is assumed to occur from the transition of an odd neutron from Nilsson orbit No.5 to No.9, the magnitude order of experimental data can not be explained. The transition probability from No.5 to No.9 was calculated, taking into consideration the mixing of Nilsson orbits because of Coliolis' force. Calculating the Coulomb form factor of K sup(π)=1/2₁⁺ rotation band state on the basis of that assumption, E2 intensity decreased by two figures as to 0.58 MeV 1/2⁺ and 0.98 MeV 3/2⁺ states, and by one figure as to 1.96 MeV 5/2⁺ and 2.74 MeV 7/2⁺ states, as compared with experimental data. In this way, the transition intensity of K sup(π)=1/2₁⁺ rotation bands can be explained by considering the orbital mixing of odd neutrons. (Tai, I.)

[en] In two 4⁺ levels (2.37 MeV 4₁⁺ and 2.77 MeV 4₂⁺) of ⁵²Cr, the dependency of the form factors on momentum transfer q differs. The 4₂⁺ level is explained by considering the mixing of seniority at fsub(7/2)⁴ proton coordination. For the 4₁⁺ level, that at other coordination must be considered. The results of analysis on the 4₁⁺ level with this incorporation of the mixing at other coordination are described. In the analysis, starting from not unreasonable hypothesis, the wave function at the 4₁⁺ level was determined. (Mori, K.)

[en] The ground state of ⁵²Cr has relatively simple coordination, i.e., it is the closed shell for neutrons and has fsub(7/2)⁴ state of protons. Several excitation states can be generated from this only one coordination. These states are characterized by seniority as well as spin and parity. Because of the requirement of anti-symmetry of wave functions, really probable states are those with seniority V=2 and angular momentum J=2, 4 and 6, and those with V=4 and J=2, 4, 5 and 8. These states are expected to have low exciting energy. As to the transition among these states or the excitation from ground states, seniority selection rule restricts the transition, therefore all transition of ΔV=4 is forbidden. The electrical transition of ΔV=0 is also forbidden. In some experiments, however, the γ ray emissive transition from 6⁺ state of V=2 to both 4⁺ state of V=2 and 4⁺ state of V=4 has been observed. Moreover, the forbidden γ ray transition from 4⁺ state of V=2 to 2⁺ state of V=2 has been observed. It is interpreted that the occurrence of such forbidden transition is due to the seniority mixing in each state. The experiment, reported in this paper, shows that this phenomenon of forbidden transition can not be explained only by employing the seniority mixing. (Tai, I.)

No abstract available

[en] THz sciences have been developing rapidly to satisfy high demands from commercial and industrial usages with helps of the recent significant developments of radio technologies at higher frequencies and optics for longer wavelengths. For the developments of THz light sources, the accelerators have an advantage to generate light pulses with high peak powers and short durations by their manipulability that make electrons compressed less than pico-seconds. Here, we use the proposed 'combination of velocity bunchings' method for the compression of electrons in order to generate the quasi-monochromatic THz light sources as the undulator radiations. In this paper, we report on the result of experiment held at Nihon Univ., where we observe signals of the THz lights generated from interactions between the existing IR-undulator and the low energy electron beam at around 13 MeV that have not been achieved as successful transportations until then. (author)

[en] The 125-MeV electron linac at the Laboratory for Electron Beam Research and Application (LEBRA) has been operated about 2000 hr a year for a variety of users' experiments conducted using near-infrared free-electron laser (FEL) and parametric X-ray (PXR). Combination of the fundamental infrared FEL with BBO non-linear optical crystals yielded the higher harmonics with good conversion efficiencies, which has extended the available wavelength range as short as 400 nm. The latest work on the PXR generation using a Si(220) target crystal demonstrated the highest energy of approximately 33.2 keV with sufficient intensity for application. Improvement in the temperature control of the accelerator cooling water system has contributed greatly to stabilization of the electron beam and the light sources. However, there still remain other minor but non-negligible factors causing fluctuation in the properties of the light sources, especially of the PXR beam when used for experiments of diffraction enhanced imaging. (author)

[en] The resonator length of the free electron laser (FEL) at LEBRA in Nihon University has been correlated with the temperature of the floor concrete in the accelerator room. This has suggested that the change in the resonator length due to expansion and contraction of the floor may be compensated by monitoring the temperature to keep the constant FEL output power. For more precise monitoring of the temperature around the FEL system a new thermometry system has been installed in the accelerator room, since the data logger system was deteriorated due to a long period of use under the strong radiation. The dependence of the FEL resonator length on the floor temperature has been estimated to be approximately -81.4 μm/degC. However, the measurements over the period of 24 hr have suggested a stronger correlation with the temperature of the air surrounding the undulator rather than the floor concrete. (author)

[en] Operation time of the 125-MeV electron linac was approximately 2000 hours in 2010 at the Laboratory for Electron Beam Research and Application in Nihon University, serving total of 1400 hours of beam time for users' experiments. In addition to conventional full-beam acceleration, a burst-beam acceleration mode was implemented in the renewed electron gun system. The x-ray intensity in the parametric x-ray radiation beam has been measured using thin-wall ion chambers developed for in-line monitoring. (author)