Electrical breakdown in vacuum is a complicated phenomenon, since there are no gas particles to become carriers of breakdown currents. The breakdown characteristics are, therefore, fully influenced by surface conditions of electrodes and insulators. This article presents fundamental mechanisms of electrical breakdown in vacuum. It is pointed out that characterization of electrode surface condition is principally important and thus in situ surface analysis is necessary to reveal the electrical breakdown mechanism of a vacuum gap. An experimental system is introduced to carry out this in situ surface analysis and breakdown experiments. Some examples of surface precautions improving breakdown strength of a vacuum gap, such as in situ sputter cleaning, diamond turning to mirror finish, in situ heat treatment are given.

Recent progress of a laser plasma particle accelerator is reviewed. After the success of mono-energetic electron accelerations, researches were focused to obtain a reproducibility and stability by adopting various electron injection techniques and plasma channels. Stabilities of output parameters have been improved 20–50% by controlling electron injection and plasma channel.

As “top-up” injection is widely used in synchrotron radiation sources, it has become very important to suppress stored beam oscillation during beam injection. To minimize this oscillation, many methods have been proposed. A pulsed multi-pole magnet injection system is one of the promising candidates and has been studied for many years at KEK. In this article, we summarize this pulsed multi-pole magnet injection system focusing on the difference between the pulsed quadrupole magnet installed in the Photon Factory Advanced Ring and a pulsed sextupole magnet in the Photon Factory.

The International Workshop on Future Linear Colliders 2011 (LCWS11) was held from September 26 through 30 in 2011 at Granada, Spain. A brief overview of the ILC (International Linear Collider) accelerator part of the workshop is reported.

The 22nd International Conference on Magnet Technology(MT-22)¹⁾ was held in Marseille, France from 12 to September 16, 2011. The brief overview of this conference is reported.

A groundbreaking ceremony was held on November 18 at KEK Tsukuba Campus, to celebrate the official start of KEK’s new particle physics experiment, the “SuperKEKB project”. The program included a press tour to the KEKB accelerator and the Belle detector, a press briefing, a ceremony and a party.

Sixth International Accelerator School for Linear Colliders was held in Pacific Grove, California from Nov. 6 to Nov. 17 in 2011. Fifty five young researchers participated in this school and learned about future lepton collider technology. This report describes the overview of the school and our personal impression.