Takashi Obina

Reconstruction for the brilliance-upgrading project of the Photon Factory storage ring

Reconstruction of the Photon Factory storage ring (PF ring; 2.5 GeV) is now in progress to provide very brilliant synchrotron radiation to users, i.e. the emittance is being reduced by a factor of five. Components, such as the quadrupole and sextupole magnets, vacuum chambers, beamlines and beam-position monitors, are being replaced by new ones in 16 normal-cell sections of the PF ring. The accelerating cavities, injection systems and control systems are also being replaced. Operation will commence when the improvements are completed on 1 October 1997.

Operation of a fast polarization-switching source at the Photon Factory

We have been developing a fast polarization-switching source for the vacuum ultraviolet and soft X-ray region at the B15-16 straight section of the 2.5-GeV Photon Factory (PF) storage ring. The source consists of two tandem APPLE-II-type elliptically polarizing undulators (EPUs), namely, U#16-1 and U#16-2, and a fast kicker system. The target frequency of polarization switching is 10 Hz. As the first step, we installed U#16-1 and five identical bump kickers in the PF ring in March 2008. Then, we constructed U#16-2 and installed it in August 2010. The orbit switching operation at 10 Hz, for user experiments, started in January 2012. We describe the details of the operation status of two EPUs and the fast local bump system in this report.

Commissioning of the PF Ring after the Reconstruction for the Straight‐sections Upgrade

At the 2.5‐GeV ring of the Photon Factory, a large reconstruction of the lattice around the straight sections has been accomplished in 2005. Thus reconstruction is the main part of the straight‐sections upgrade project to rebuild existing undulators and to increase the number of undulator beamlines. As a result of the reconstruction, four short straight sections have been newly created and the lengths of the existing straight sections have been much extended. To exploit the new straight sections, short‐period narrow‐gap undulators which have a sufficiently high brilliance in hard x‐ray range have been developed. The reconstruction work of the ring was completed in a seven‐month shutdown from March to September, 2005. In the area over two thirds of the storage ring, all the quadrupole magnets and all the beam ducts have been renewed and rearranged to construct the new lattice. Recommissioning of the storage ring was finished at the end of October, 2005. Though we made no in‐situ baking for the beam ducts, ...

Fast polarization switching in the soft X-ray region at PF BL-16A

Recent development in fast polarization switching at the soft X-ray beamline, BL-16A in the Photon Factory is reported. Two APPLE-II type undulators installed in a tandem configuration enables us to achieve polarization switching between not only two opposite circular polarizations, but also the vertical and horizontal linear polarizations. An energy shift is observed during polarization switching due to a vertical modulation in the electron beam, which has been reduced by properly correcting the electron orbit.

Present status of Photon Factory Advanced Ring

The upgrade project of the pulse X-ray source PF-AR was successfully completed by the end of 2001. The initial beam current and the lifetime were largely improved. The injection energy was raised from 2.5 GeV to 3.0 GeV, the maximum beam current of 65 mA was achieved. With a new global orbit feedback system, orbit drifts were largely improved.

Initial test of a bunch feedback system with a two-tap FIR filter board

Initial beam test of the KEKB bunch-by-bunch feedback system prototypes has been performed in the TRISTAN-AR on the longitudinal plane. A simple two-tap finite impulse response (FIR) filter system consisting of hardware logic realizes the function of the phase shift by 90°, the suppression of static components, and the delay of up to a hundred turns. With the prototype filter board and a longitudinal kicker, the feedback loop has been closed successfully. The shunt impedance of the kicker was estimated from the excitation amplitude and measured damping. The damping time of the system has been measured by using the single-bunch Robinson instability. The feedback system stabilized the coupled-bunch instability completely under 8-bunch operation.

New Upgrade Project for the Photon Factory Storage Ring

A new project for upgrading the 2.5‐GeV Photon Factory (PF) storage ring is now being undertaken to create six new short‐straight sections and to lengthen the existing eight straight sections. The short‐straight sections will provide an opportunity to install short‐period narrow‐gap undulators, while the extensions of existing straight sections will be taken advantage of updating current insertion devices to the latest models in future. To this end, the lattice configuration around the straight sections is modified by replacing old quadrupole magnets with new shorter ones and placing them closer to the near‐by bending magnets. Necessary replacement of the vacuum ducts and the beamline front ends will be carried out together. This project will be completed by the end of September, 2005, after six months of shutdown.

Molecular orientation change during adsorption of NO and N2O on Ir(111) observed by real-time wavelength-dispersive x-ray absorption spectroscopy with polarization switching

The molecular orientation of NO and N2O during adsorption on Ir(111) is observed by combining the wavelength-dispersive x-ray absorption spectroscopy with 1 Hz switching between the vertical and horizontal linear polarizations. It is revealed that NO adsorbs keeping its molecular axis at ∼20° from surface normal. In contrast, N2O rapidly adsorbs up to 2/3 of the saturation coverage with an orientation angle of ∼35°, then turns to a slow adsorption phase with larger orientation angles, and gradually reaches its saturation with an average orientation angle of ∼45°. Such a complicated behavior is interpreted by assuming different adsorption sites.

Status of R&D efforts toward the ERL-based future light source in Japan

The energy recovery linac is a very promising synchrotron light source in future. We are contemplating to realize a ERL_based next generation light source in Japan, under a collaboration between KEK, JAEA, ISSP, and other SR institutes. To this end, we started R&D efforts on its key technologies, including a low-emittance photocathode gun and superconducting cavities. We also plan to assemble these technologies into a small test ERL, and to demonstrate their operations. We report our R&D status.

Longitudinal feedback system for the Photon Factory

In the KEK Photon Factory, longitudinal coupled- bunch instabilities are suppressed using the RF phase- modulation technique during the users operation. This technique is very effective not only to suppress the instabilities but also to enlarge the beam lifetime. Together with the study for top-up operation, longitudinal bunch-by-bunch feedback system has been developed. A two-port longitudinal kicker based on DAPhiNE-type cavity were designed and installed in the storage ring in the summer of 2006. FPGA-based signal processing part is under development based on the KEKB design. A mode feedback system which suppresses a specific coupled-bunch mode was tested successfully as a preliminary test of the kicker. By using a commercial FPGA evaluation board, a simple bunch-by-bunch feedback system was implemented and succeeded to suppress the coupled-bunch instability up to 52 bunches in the ring.