Y. Ohsawa

Magnet system for the KEKB main ring

Abstract KEKB is a two-ring electron–positron collider with asymmetric energies of 8 and 3.5 GeV to study CP violation in B meson decay. In KEKB, there are 21 types of magnets; about 1600 in total. About 430 dipole and quadrupole magnets were recycled from TRISTAN, the preceding program. All quadrupole magnets are equipped with vertical and horizontal steering dipole magnets. The number of steering magnets is about 1700. There are 212 sextupole magnets, and all of them are fixed on remotely controlled movers to adjust their positions to the beam passage. All main dipole magnets have back-leg coils to steer beams precisely. All quadrupole and sextupole magnets are equipped with correction coils to have a capability for beam-based alignment. Also one-turn coils are installed as well to each magnetic pole of the main magnets to monitor the magnetic flux in the case of trouble. The magnetic field in all magnets was measured and its quality strictly checked. After field measurement, the magnets were installed and precisely aligned. A cooling water system and a power supply system for these magnets were constructed. Magnet design was started in 1994, and construction of the two rings was completed in November 1998. The parameters of the magnets and the construction of the KEKB magnet system are described. Some of the problems experienced during this construction work are also presented.

Superconducting quadrupole magnet system for TRISTAN mini-beta insertions

Superconducting quadrupoles for the mini-beta insertions were installed close to every interaction point and their performances were tested successfully. The system consists of four subsystems, which can be operated individually at the local control rooms located near the subsystems and/or at the remote central cryogenic control room.<<ETX>>

Field measurement of superconducting quadrupole magnets for TRISTAN mini-beta insertions

Eight superconducting quadrupole magnets for TRISTAN minibeta insertions (QCS) have been measured by the rotating coil method before installation in the TRISTAN electron-positron colliding ring. Following the alignment of the magnet to the measuring system by use of a movable QCS-support, harmonics and field gradients were measured as functions of current and the median plane was determined for each magnet. Details of the measuring systems and results of the measurements are presented. The results of the field measurements show that the relative errors of the integral field gradient can be kept within +or-0.001 for all the magnets and that the higher multipole components are small enough for the tolerance required to the QCS.<<ETX>>

Status of PF-AR

The PF‐AR is a full‐time single‐bunch light source for SR experiments in the X‐ray region. Electrons are injected at 3.0 GeV and ramped up to the final energy of 6.5 GeV for normal user operation or 5.0 GeV for medical application. The typical initial beam current is 55 mA at 6.5 GeV and the beam lifetime is 15 h at 50 mA. The initial single‐bunch impurity better than 10−8 was achieved, however, degradation of the impurity during the users’ run has to be solved. Since the present emittance of 290nm⋅rad is not satisfactory, we are making an effort to realize the minimum attainable emittance of 160nm⋅rad. The high quality of pulse X‐ray has brought us abundant occasions to do time‐domain and/or time‐resolved measurements.