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Applying permanent magnet technology to beam focusing in klystrons can reduce power consumption and increase reliability. These features benefit a variety of applications especially for large facilities that use a large number of klystrons such as the International Linear Collider. The low magnetic field needed for the purpose allows us to use inexpensive ferrite magnets instead of rare earth magnets. In order to evaluate the feasibility of such a focusing system with ferrite magnets, a test model for 750 kW L-band klystron was constructed. As a result of the power test, we attained 94% of the output power compared to an electromagnet.

Permanent magnets are superior to electromagnets in generating strong multipole magnetic fields. Their fields are sometimes stronger than those that can be generated by superconducting magnets with the same bore radius, when the number of poles are higher. Three fabricated multipoles including a quadrupole magnet for the ILC (International Linear Collider) final focus doublet, a quadrupole magnets as a spin filter for cold neutrons, and a sextupole magnet for neutron beam focusing are described.

The design and the magnetic field measurement of the quadrupole magnet for the compact ion ring, S-LSR, are presented. Because the S-LSR is a compact ring accelerator, whose components take up most of the space in the arc sections. Therefore, we have to optimize the integrated field gradient in the quadrupole magnetic field taking account of the effect of the neighboring field clamp. Under these conditions plus requirements from accelerator parameters, the design of the S-LSR quadrupole magnet was optimized by means of 2D and 3D modeling calculations. A magnet field measurement by a Hall probe is carried out together with the field clamp and S-LSR bending magnet. Both results of the calculation and the measurement present the almost same result as that for the effect of the field clamp.

Permanent magnet quadrupoles (PMQ) and sextupoles (PMSx) have been fabricated and tested. Their effective strengths are variable. The PMQ has been developed as a final focus magnet for a linear collider. There is enough space to put Gluckstern's 5-ring singlet structures in each incoming beam line. The magnetic center offsets and higher harmonic components can be adjusted by adjusting the positions of the magnet pieces with screws on holders. The measured integrated gradient can be reduced down to less than 1% of the maximum strength. The PMSx has been developed to focus pulsed cold neutrons for a small angle neutron scattering (SANS) experiment. The strength is modulated by a so called double ring structure, where the inner ring is fixed and the outer ring is rotated. A torque canceller can reduce the torque to rotate the outer ring by one third of its original magnitude. The focal length of the fabricated triplet lens is less than 50 cm for Very Cold Neutrons (VCN). It is demonstrated that VCN-SANS can shorten a SANS beamline, which usually has a few tens of meters, down to 2~3 meters.