[en] The geological age of the Quaternary Shiobara group has generally been accepted as Pleistocene. But, more strict correlation of this group involves many problems to be solved by future studies. No good tie has been shown between the material dated and the stratigraphic sequences established in other areas through geological studies. The author collected five fossil woods from the Shiobara Basin. The present report gives radiocarbon data of the Shiobara group. Four radiocarbon analyses of fossil woods from the Shiobara group yielded data ranging from 28000+-1400 years B.P. (Gak-3356, fossil wood from the Akagawa formation, upper unit of the Shiobara group) to 33600+3200-2200 years B.P. (Gak-3596, fossil wood from the Akagawa formation, upper unit of the Shiobara group). The radiocarbon measurements reported here were made by Dr. K. Kigoshi, Gakushuin University. The author hopes that this work will call for fresh studies on the geological age of the Shiobara group. (auth.)

[en] The sphenoidal sinus lesions, which were documented by sinus CT, were found in 32 sides of sphenoidal sinus of 19 patients seen in 14 months from January 1984 to February 1986. Sphenoiditis was frequently seen as in 17 % in the all poly-sinusitis, and sphenoidals cysts were seen in 4 side in 3 patients. The indications of the sphenoiditis by CT were thickening of the mucosa and opacificasion with soft tissue density. By sphenoid cysts, no contrast enhancement was seen and margins of the cyst wall were smooth and regular with bone erosion. Since erosion of the bone is also seen in Wegener's granulomatosis and carcinoma, the CT image of the bone erosion is not specific to either of them and does not contribute to the definitive diagnosis of malignancy. (author)

[en] In order to attain the heightening of oscillation power and the shortening of oscillation wave length of free electron laser, it is necessary to increase the current and heighten the quality of incident beam. The quality of incident beam depends strongly on the performance of an electron gun. For shortening the region where the effect of spatial charge exists, RF electron gun was developed. The RF electron gun using a photo-cathode is excellent very much for accelerating large current, high quality electron beam, however, the problem is that the life of generally used photo-cathodes is short. For the purpose of acquiring the basic data of the photo-cathode which is required for developing the RF electron gun, the development of a large power, high quality beam injector system was started. The results of research in fiscal year 1995 and the present state are reported. First, a DC type electron gun was made, the feature of which is the mechanism of turning the cathode. Next, the test of applying DC 200 kV was carried out. At present, the beam test by using a generally used thermal cathode is in progress. The basic characteristics of this electron gun are measured, and the effect that the asymmetry of electric field exerts to beam is studied. The development of hereafter is described. (K.I.)

[en] Presently, the Beam Group of Oarai Engineering Center in Japan Nuclear Cycle Development Institute (JNC) completed the high power CW electron linac. Then we started full-scale beam experiments after the government permission for a radiation equipment had given last January. Measurements of basic performance for the mesh-grid type electron gun have been done to launch stable beam at 300 mA peak current downstream of the accelerator. These experiments disclosed to increase beam loss in the electron gun in some cases of voltage supplied the mesh-grid in spite of same beam current from gun. Consequently, we could find the best condition for mesh-grid voltage and heater current to supply stable beam at 300 mA peak current for accelerator study. (author)

[en] An electron gun launching high average current beam has been designed for the high power CW electron linac at PNC. A peak electron beam current of 400mA with beam energy 200keV is required from the buncher design. However its average current is very high(duty factor 20%), a mesh grid is not able to be used for current control because of heating up or melting of grid. Furthermore, the beam current have to be variable up to 400mA to match with downstream modules, especially the accelerating guides including recirculating system. We employed the electron gun with two aperture grids to control beam current. The dimension of the electrodes, electron trajectory, the size of beam radius, and gun emittance was simulated by EGUN. (author)

[en] Presently, the Power Reactor and Nuclear Fuel Development Corporation(PNC) is investigating the best way to treat high-level radioactive nuclear wastes from reactors. As part of their basic research on the transmutation of fission products, PNC developed a high-power CW electron linac for various applications, in particular for studying the use of strong gamma rays for transmuting the medium-lived fission products (MLFP), Sr-90 and Cs-137. As the results of studies of transmutation by photoreaction, high-flux and high-energy gamma rays (∼15MeV) are needed. However, to make an approach feasible it is very important to generate the gamma rays at a reasonable cost. To increase the intensity of the gamma rays, a high-current electron beam and a high-power laser are needed. This paper reports our findings which show that to generate gamma rays by inverse Compton scattering effectively the photons accumulated in a optical resonator must intensify the monochromatic gamma ray flux by the collisions of inverse Compton scattering with electrons. The method we discuss employs inverse Compton scattering with an optical resonator composed of very high-reflectance and low-absorptance mirrors. With advances in technology, the flux of gamma rays that can be attained is of the order of 10¹⁸, and its efficiency is 0.9% using this method. If future technological progress results in a mirror with a reflectance of 8N and absorptance of 0.001 ppm, then it might be possible to achieve a flux of the order of 10²⁰ and an efficiency of more than 30%. In the case of a concentric resonator, the density of the photon beam at the interaction point can be higher than that in a confocal type so that a gamma ray flux of the same order as the 8N case may be achieved. (author)

[en] A high brightness gun with a small thermionic cathode has been designed and manufactured to produce a low emittance beam. To study the beam we have developed an emittance measurement system based on the 'pepper-pot' method. We find a normalized rms emittance of order π mm · mrad, and a normalized brightness of order 10¹⁰ A/m² · rad². (author)

[en] It is the report to improve the problem of flow reduction in water cooling system resolved completely in summer, 2017. It is continued the phenomenon decreasing the flow (5,800 L/min) of circulating water cooling in DTL and SDTL about 3% per week. By the flow reduction, the entire operation of J-PARC and operation of the accelerator are stopped and low flow contact of flowmeter installed in cavities. The phenomenon is progressed about 9 years since we confirm it and drastic measures for it are aspired. In this report, the point of interest to solve this problem is written. Similarly, it is suggested that the point we should be careful when we use the water cooling system it is one of the utility of J-PARC accelerator. In last summer, the flow reduction does not occur completely as specification changes and replacement of the pumps. Thanks of that, the entire operation and operation of accelerator of J-PARC is operated safety. (author)

[en] The authors report a 10-day-old infant with osteomyelitis of the maxillary bone, where computed tomography was very useful in diagnosis, determining the type and time of surgery, and in observation of the postoperative course. Although osteomyelitis of the maxillary bone in new-born infants has once been a life threatening disease, it can now be controlled and treated adequately with surgery and chemotherapy through accurate evaluation of the disease using computed tomography. (author)

[en] We tested a beam transport system in the JNC Linac at a high average beam current test. In this test, a 100 mA electron beam with 1.5 msec pulse width and 35 pps repetition was accelerated to 7 MeV and we found issues those are heat generations of ceramics ducts for current monitors and a beam duct at a quadrupole magnet for a beam dump. In this paper, we discuss causes and cures of them. (author)