[en] An intense pulsed slow positron beam was extracted from a 100 MeV electron Linac at JAERI-Tokai (Japan Atomic Energy Research Institute, Tokai Establishment) using solenoid transport tubes

[en] It has been verified experimentally in JAERI-FEL that a high-gain FEL oscillator has the maximum extraction efficiency at the perfect synchronism of optical-cavity length. The simultaneous measurement of FEL efficiency and absolute cavity length has clearly shown that a sharp peak of detuning curve at the perfect synchronism appears in high-gain and low-loss regime and the FEL extraction efficiency exceeds the scaling law of short-bunch FEL oscillators. A numerical analysis indicates that lasing at the perfect synchronism is quasi-stationary superradiance with random fluctuations, which is analogous to a SASE FEL. Second-order autocorrelation measurements show that FEL pulses shorter than four optical cycles are generated successively for a number of round trips at the perfect synchronism, which is consistent with numerical results

[en] In 1982, aiming at the new development of atomic energy research, the tandem accelerator of Japan Atomic Energy Research Institute (JAERI) was installed. In fiscal year 1993, the superconducting boosters which can increase the ion energy by up to 4 times were added, and the research in the region below 1000 MeV became possible. Those are electrostatic type accelerators which are easy to be used especially in basic research field, and are useful for future research. The tandem accelerator has been operated while maintaining the first class performance as the accelerator for various kinds of heavy ion beam. It has the special shape among electrostatic type accelerators, and is excellent in the easiness of control and stability. The main particulars of the tandem accelerator are shown. As for the ion sources of the tandem accelerator, three cesium sputter type ion sources are installed on two high voltage stands. The kinds of the ions which can be accelerated are mainly negative ions. As the improvement, electron cyclotron resonance (ECR) ion sources are expected to be adopted. As for the tandem boosters, the 1/4 wavelength type resonance hollow cylinder was adopted. The constitution of the tandem boosters is explained. The way of utilizing the tandem accelerator system and the aim for hereafter are reported. (K.I.)

[en] An energy-recovery linac (ERL) for a high-power free-electron laser (FEL) has been designed and constructed at Japan Atomic Energy Research Institute (JAERI). The construction of the ERL was completed and first energy-recovery operation and first FEL lasing have been demonstrated. We present the design overview and the performance of the JAERI-ERL. Future plans towards a 10-kW FEL are also described

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[en] JAERI has been proposed a high intensity proton linear accelerator to be utilized in future accelerator-driven Partitioning and Transmutation (P and T) system. The R and D of the high intensity proton accelerator was started in 1991 as one of the approaches for the OMEGA program in Japan. The first phase of the R and D has been made successfully on the components of the front-end part of the accelerator i.e., an ion source and RFQ, resulting in the peak current of 70 mA with duty factor of 7 ∼ 10 % operation was obtained at the energy of 2 MeV after the RFQ acceleration. In these years, JAERI has been planned the Neutron Science Research Program (NSRP) for exploring basic researches and nuclear waste transmutation technology based on a next generation spallation neutron source driven by the high intensity proton linac. The conceptual design of the high intensity proton accelerator is rearranged slightly to achieve various operation modes in the NSRP. The second phase R and D has been started for the study of whole accelerator system with 1.5 GeV and 10 mA, beam power of about 15 MW. This report describes the summary of the first phase R and D and the present status of the second phase development of the high intensity proton linear accelerator. (authors)

[en] An energy-recovery linac for a high-power FEL has been developed at Japan Atomic Energy Research Institute, and a research program towards a 10 kW FEL is in progress. Since FEL interaction introduces large energy spread in the electron beam, special attention should be paid to both transverse and longitudinal phase space manipulation through the return-arc and the deceleration path. We present beam dynamics simulations coupled with a 1D FEL code, and discuss the limitation of FEL extraction efficiency determined by phase space acceptance of the return path

[en] A new linac was installed at Japan Atomic Energy Research Institute. This paper presents the linac performance and the experimental facilities, especially neutron target. The linac is an S-band machine, and consists of five accelerator sections. Each section is operated in the 2π/3 mode, and powered by a 20-MW klystron. Electron beam current, 1 mA at 190 MeV maximum energy and 600 mA at 100 MeV, is obtained when pulse width of 0.5 μsec and RF power of 20 MW are fed into each accelerator section. The pulse width from 10 n sec to 2μsec is available, and the repetition rate is variable between a single shot and 600 pps. The facilities by the time of flight method to measure neutron cross section are installed. Six flight paths radiate from the neutron target room. In these facilities, the total cross section measurement by transmission method is carried out at the 190 m station, the capture cross section measurement with a large liquid scintillation detector at the 55 m station, and scattering cross section measurement at the 45 m station, respectively. Water cooled tantalum was used as the target material for neutron production, because of its relatively low cost, high melting point, low residual activity and high resistance to erosion and corrosion. Several measurements were carried out for obtaining information about the electron beam spread in the target and for determining the target size. The electron energy dependence of relative neutron yield was also measured. (Kato, T.)

[en] This paper describes the new trigger pulsers to drive the large thyratrons (8479/KU275, ITT) in the linac modulators. A small thyratron 5C22 in the pulser was replaced by SCR's to improve long term stability and to expect easeier maintenance. The pulser of line-type uses two SCR's in series to keep enough voltage endurance and switching speed and generates pulse outputs of 1.5 kV in voltage and of 2 μsec in width. They have been working very well for about one year. (author)