T. Mitsuhashi

Commissioning of KEKB

KEKB has been operated since December, 1998, to deliver BB pairs for a physics detector. In this paper,we describe the commissioning procedure of KEKB.

KEKB beam instrumentation systems

For the stable high-luminosity operation and luminosity increase, the electron and positron storage rings of the KEK B-Factory (KEKB) is equipped with various beam instrumentations, which have been working well since the start of the commissioning in December, 1998. Details and performance of the beam-position monitor system based on the spectrum analysis using DSPs, the turn-by-turn BPM with four-dimensional function available for measurements of the individual bunch position, phase and intensity, the parametric beam-DCCTs designed so as to avoid the magnetic-core-selection problems for the parametric flux modulation, the bunch-by-bunch feedback system indispensable to suppress the strong multibunch instabilities in KEKB, the various optical beam diagnostic systems, such as synchrotron radiation interferometers for precise beam-size measurement, the tune meters, the bunch length monitors and the beam-loss monitors are described. Delicate machine tuning of KEKB is strongly supported by these instrumentations.

Construction of a multiundulator, Revolver No. 19, at the Photon Factory

A multiundulator, Revolver No. 19, was constructed and installed at the straight section (B 18‐B19) of the 2.5‐GeV Photon Factory storage ring. The mechanical structure of Revolver No. 19 consists of a main frame and two rotatable beams with four base plates, on which undulator magnets with four different lengths of period are mounted. A pair of undulator magnets with a desired period length can be selected by revolving the rotatable beams. The energy range of the radiation covered by fundamental peaks from the undulator magnets is from 7.8 to 1150 eV.

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.

The construction of the superconducting vertical wiggler and its operation in the photon factory

Abstract The superconducting vertical wiggler of the Photon Factory, KEK, was installed in the storage ring in October 1982. Its first operation with 2.5 GeV electron beam was successfully done in February 1983, the wiggler radiation was observed in the beamline through a Be window using a fluorescent screen as well as with a solid state detector, by changing the magnetic field strength of the wiggler. Since February 1984 it has been operated in the normal users time. The maximum magnetic field achieved after installation in the storage ring is 5.8 T. However, we have operated the wiggler magnet at 5.0 T in usual operation as to obtain long enough beam lifetimes for the users run. At this moment, we have achieved an average beam lifetime of 1500 min at a stored curret of 100 mA.

Beam position stabilization at the Photon Factory (invited)

To obtain position‐stabilized photon beams from the Photon Factory storage ring, our efforts were concentrated on two directions, one to minimize any disturbances causing the stored beam to move, and the other to suppress undesired beam motion by using feedback systems. This paper concerns one of the most disturbing cases, the diurnal beam position drift. The drift motion was suppressed with a global orbit feedback system, so that photon beam position was kept stable at all the beamlines. At the same time, some disturbances were reduced by investigating the cause and the mechanism of beam motion. The fact that the beam drift motion was closely correlated to the outdoor temperature variations led us to make a model simulation by taking account of the meteorological conditions around the building. It was proved that the building distortion due to the external thermal stress resulted in the diurnal beam motion. To minimize such distortion, it is suggested that one should insulate the building on the rooftop rather than underneath it as is usually done.

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, ...

High-flux photon beam position monitor

A high‐flux photon beam position monitor for insertion devices was constructed and tested at the Photon Factory. The monitor comprises two pairs of water‐cooled right‐triangle electrodes placed in paralled at both horizontal edges of the beam. The monitor’s linear regions are 800 μm in the horizontal direction and more than 1200 μm in the vertical direction. The response of the monitor was also studied for various gap sizes of insertion devices.

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.

Measurement of the beam size at the compact superconducting storage ring by the SR interferometer

The beam size in the compact superconducting storage ring AURORA was measured using the SR interferometer developed by one of the present authors. The spatial coherence of the radiation beam in the visible range was derived from the visibility of the interferogram recorded by a CCD camera and its dependence on the spatial frequency has shown that the beam profile is described by a Gaussian. Analysis of the data has yielded the beam size to be 10.5 μm in the vertical direction, which is unexpectedly small for the storage ring having only a weak beam focusing system.