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An experiment on the investigation of optical diffraction radiation (ODR) from a slit target as a possible tool for noninvasive electron beam-size diagnostics has been performed at the KEK accelerator test facility. The experimental setup has been installed at the diagnostics section of the extraction line. We have performed the first incoherent ODR observation from a slit target. The measured angular distributions are in reasonable agreement with the theoretical expectation. The beam-size effect onto the ODR angular pattern has been observed. Moreover, the sensitivity to the beam size as small as 14 microm has been achieved.

A system for inspecting the inner surface of superconducting rf cavities is developed in order to study the relation between the achievable field gradient and the defects in the inner surface. The inspection system consists of a high resolution complementary metal-oxide-semiconductor camera and a special illumination system built in a cylinder that has a diameter of 50 mm. The camera cylinder can be inserted into the L-band 9 cell superconducting cavity. The system provides a resolution of about 7:5 m=pixel. Thus far, there have been good correlations between locations identified by thermometry measurements and positions of defects found by this system. The heights or depths of the defects can also be estimated by measuring wall gradients using the reflection angle relation between the camera position and the strip illumination position. This paper presents a detailed description of the system and the data obtained from it.

A novel scheme for the focusing of high-energy leptons in future linear colliders was proposed in 2001 [P. Raimondi and A. Seryi, Phys. Rev. Lett. 86, 3779 (2001)]. This scheme has many advantageous properties over previously studied focusing schemes, including being significantly shorter for a given energy and having a significantly better energy bandwidth. Experimental results from the ATF2 accelerator at KEK are presented that validate the operating principle of such a scheme by demonstrating the demagnification of a 1.3 GeV electron beam down to below 65 nm in height using an energy-scaled version of the compact focusing optics designed for the ILC collider.

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