Yoshihiko Shoji

Polarization Property Measurement of the Long Undulator Radiation Using Cr/C Multilayer Polarization Elements

A rotating analyzer ellipsometry (RAE) system was developed with Cr/C multilayers that function as polarization elements for photon energy range of 110 – 280 eV. Polarization properties of a planar undulator change axisymmetrically in off‐axial manner, and the second harmonic is more remarkable for the change. By using the RAE system, the polarization property of the second harmonic radiation from the NewSUBARU long undulator at the energy of 180 eV was examined. The degree of linear polarization of the on‐axis radiation was over 0.996. The spatial distribution of the polarization azimuth was measured and was in fair agreement with the theoretical calculation. A peculiar behavior of the polarization property near the radiation peak of the second harmonic was observed by changing the height of the undulator gap.

Circulation of Short and Intense Electron Bunch in NewSUBARU Storage Ring

We demonstrate our idea to circulate a short and intense linac bunch for some tens of turns in an isochronous ring. We compressed the SPring‐8 linac bunch to a few pico‐seconds rms by means of the energy compression system (ECS) and the beam transport line to NewSUBARU. The NewSUBARU storage ring was set at quasi‐isochronous condition and the bunch circulated for some tens turns after injection keeping the short bunch length.

RF Synchronized Injection from SPring‐8 Linac to NewSUBARU Storage Ring

This paper confirms the occurrence of RF synchronized injection from SPring‐8 Linac to the NewSUBARU storage ring. NewSUBARU is a 1.5 GeV storage ring with injection energy of 1.0 GeV. Besides the 1.5 GeV user mode, the ring is often operated at 1.0 GeV for EUV users with the so‐called top‐up injection mode. In this experiment, we use a new synchronization method developed at SPring‐8, wherein an instantaneous synchronization between NewSUBARU RF (500 MHz) and Linac RF (2856 MHz) enables a buckets‐to‐bucket beam transfer. This is one of the key technologies of top‐up operations in a storage ring that uses a linac as an injector. The RF clock and timing trigger signal are sent to the Linac from NewSUBARU, and this clock is used to delay units in order to maintain good synchronicity. This works as a standard because it has a system to compensate for transfer‐time drift. The arbitrary waveform generator is another key module. It produces a clock 1/32 of that of the Linac RF using the NewSUBARU RF clock. With...

Beam‐Based Confirmation of Skew‐Quadrupole Field Correction in 10.8 m Long Undulator

The synchrotron radiation facility NewSUBARU is a 1.5 GeV storage ring which has two long straight sections. A permanent magnet, planar‐type, out‐of‐vacuum 10.8 m Long Undulator is placed in one of the long straight sections. The longitudinal moments of the skew‐quadrupole field errors in the undulator were determined from the response of the stored beam. The method used was to measure the change of the horizontal closed orbit distortion produced by two types of vertical local bump orbit in the undulator. This method is more reliable than the global modeling of a ring, which uses the response matrix of the whole ring, since the present method is not sensitive to skew‐quadrupole field errors in sections other than the target section.

Observation of Coherent Synchrotron Radiation from Three Types of Beam at NewSUBARU

Coherent synchrotron radiation (CSR) in Tera‐Hz region was observed at NewSUBARU. Three types of CSR from three types of electron beam were detected in the storage ring. One was a radiation burst from a high‐density single‐bunched beam. The burst had a threshold current of 1.0 nC/bunch for the normal operation parameters. The second was a quasi‐dc radiation from a low current and short‐bunched beam. The ring was operated in a quasi‐isochronous (low momentum compaction factor) mode, which could store the short‐bunched beam stationary. The bunch charge was as low as 1 pC/bunch and the bunch length was as short as 4 ps FWHM. The third was a radiation pulse following injection. A short‐bunched linac beam, with a base width of 20 ps and a charge of 50 pC/bunch, emitted short‐pulsed CSR in the storage ring.

Beam Based Search for Linear Imperfection Fields in 11 m Long Undulator at NewSUBARU

The NewSUBARU storage ring has an 11 m long undulator. It is a permanent magnet planner undulator, consisting of eight units. We measured and adjusted its magnetic field distribution to minimize the imperfection fields mainly by an in‐situ sorting method developed by T. Tanaka of SPring‐8. The imperfection fields were minimized for each unit to prevent them from exciting unnecessary betatron resonance in the ring. We measured the gap dependence of linear imperfection fields, dipole and quadrupole field components, using the stored electron beam in the ring. The results confirmed that the field adjustment reduced the imperfection fields. Strengths of the dipole imperfection fields in the undulator were at the same level as the earth field. The normal and skewed quadrupole imperfection fields were about three times of the guideline, but were smaller than the imperfections produced by the ring magnets. We conclude that the linear imperfection fields were reduced to the acceptable level.

Stray field of a pulse septum induced by eddy currents

NewSUBARU, a 1.5 GeV storage ring, has a magnetic pulse septum to inject a 1 GeV electron beam from the SPring-8 linac. Its maximum field is 0.36 T with waveform of 1 ms width half-sine. Behavior of a stored electron beam indicated an existence of a stray field whose time structure was cosine like. A beam pipe for an injected beam and a beam duct for a circulating beam made an electric loop path of an eddy current induced by the magnetic field of the septum. Off-beam measurements of magnetic field and the induced current confirmed the existence and paths of the eddy currents. An electric insulation added to a metal support of a beam pipe cut the loop path and reduced the cosine like stray field. There still exists a weak current, which runs long path along a beam transport line.

Sextupole winding in a dipole magnet gap for a storage ring

In special synchrotrons a controllable sextupole field is required in the bending dipole magnets. One of them is NewSUBARU, a 1.5 GeV synchrotron light source. It has inverse dipole (bending) magnets to control the linear momentum compaction factor. It has to have a controllable sextupole at the position of the inverse bend for an independent control of its horizontal chromaticity and its higher order momentum compaction factor while keeping enough dynamic aperture. The inverse bend is a normal conducting C-type magnet whose bending angle, maximum field strength, yoke length and magnet gap are - 8 degrees, 1.554 T, 444 mm and 40 mm, respectively. The height of vacuum chamber in it is 28 mm, smaller than that in a normal bending magnet, while the magnet gaps are the same. This is because the vertical beta function at the inverse dipole is smaller. A pair of water-cooled coil sheets, which produce a sextupole field, are set at the space between the chamber and the pole face. Its thickness, the maximum current and the maximum sextupole field are 4.4 mm, 154 A and 70 T/m/sup 2/, respectively.

Relationship between Good Grades and Brain Waves

The relationship between motivation and performance is examined because students grades depend more on student motivation (concentration) than the guidance of a teacher. To elucidate student motivation in a lesson, we examine the relationship between the time spent concentrating by measuring brain waves and exam results. Students who focused longer earned better grades or showed a significant improvement between the first and second tests.

Demand Survey of Stem Classes as Liberal Arts Subjects

The IR section of the University of Hyogo conducted a demand survey of STEM (science, technology, engineering, and mathematics) classes for students in the Schools of Social Science and the College of Nursing, which was used to design a new liberal arts program for the university. The students of the university take classes at two separate campuses. The eastern campus is for freshmen in the School of Business Administration, the School of Economics, and the College of Nursing Arts and Science, while the western campus is for the School of Engineering, the School of Science, and the School of Human Science and Environment. We compared the physics assessment test scores of students at the two campuses. Students in the eastern area have the ability to understand STEM subjects but lack an understanding of basic STEM concepts. Two questions about their interest in physics show that a considerable amount of students are interested in physics but lack of confidence. The most popular scientific field is astrophysics.