A novel internal target has been developed, which will make electron scattering off short-lived radioactive nuclei possible in an electron storage ring. An "ion trapping" phenomenon in the electron storage ring was successfully utilized for the first time to form the target for electron scattering. Approximately 7 x 10(6) stable 133Cs ions were trapped along the electron beam axis for 85 ms at an electron beam current of 80 mA. The collision luminosity between the stored electrons and trapped Cs ions was determined to be 2.4(8) x 10(25) cm(-2) s(-1) by measuring elastically scattered electrons.

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The 3-GeV rapid cycling synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC) is a high-power pulsed proton driver aiming at 1 MW output beam power. The RCS was beam commissioned in October 2007 and made available for user operation in December 2008 with an output beam power of 4 kW. Since then, the output beam power of the RCS has been steadily increasing following progressions in beam tuning and hardware improvements. So far, the RCS has successfully achieved high-intensity beam trials of up to 420 kW at a low-level intensity loss of less than 1%, and the output beam power for the routine user program has been increased to 210 kW. The most important issues in increasing the output beam power are the control and minimization of beam loss to maintain machine activation within the permissible level. This paper presents the current status of the RCS beam power ramp-up, with particular emphasis on our approach to beam loss issues. The future prospects of RCS beam commissioning and operation are also described.

Development of a SiC microwave absorber for a damped cavity is presented. The SiC studied has a resistivity of 101–102 Ω cm, which is the expected value to damp higher-order modes (HOMs) in the cavity and also has high thermal conductivity. The absorber is attached to the cavity as a part of the beam duct. Since the SiC duct receives a large amount of energy from the electron (or positron) stored beam, it is very important to estimate the dissipation power in the SiC duct and to design a cooling mechanism. The heat load problem of the SiC duct is discussed and the results of high power testing of the SiC duct are presented. The damping mechanism for HOMs is based on the power dissipation due to the resistivity of SiC. The fine control of the resistivity of SiC in fabrication is very important. The preliminary results on this problem are also presented.

Electron cyclotron emission (ECE) measurements on the tandem mirror GAMMA 10 are reported. The fifth-harmonic ECE in the thermal barrier region was measured in order to obtain the temporal and spatial evolution of hot electrons produced by electron cyclotron resonance heating for the formation of a thermal barrier potential well. The electron temperatures in the central and plug cells were determined using the second-harmonic ECE which was corrected for the hot-electron emission by considering a relativistic shift of resonance layers. The results, thus obtained, show strong evidence for the existence of a thermal barrier.