A milestone was set by the Linac (linear accelerator) of J-PARC (Japan Proton Accelerator Research Complex) on January 24, 2007. Protons were, for the first time, successfully accelerated to the designed energy of the Linac (181 million electron-volts, traveling at about half the speed of light). This marks the first step in commissioning of the high intensity proton accelerator complex, jointly built by the two national institutions, Japan Atomic Energy Agency (JAEA) and High Energy Accelerator Research Organization (KEK).
 
Negatively charged hydrogen atoms are accelerated to the designed energy through a series of accelerator components; Radio Frequency Quadruple (RFQ), Drift Tube Linac (DTL) and Separated-type Drift Tube Linac (SDTL). The average electric current was one quarter micro-ampere. "We saw the first successful beam acceleration through the RFQ last November, and we expected to complete the beam acceleration with the rest of the 120 meters Linac by the coming spring" says the linac manager Kazuo Hasegawa. "We are much delighted to have achieved the designed beam energy by three months ahead of the schedule. Of course we still have to work very hard to reach the designed beam current of two hundreds microamperes on average."
 
Two institutions started construction of J-PARC in 2001, and they are working to complete the construction of a kilometer wide accelerator complex by 2009. It is built at the Tokai Campus of JAEA, which is located approximately 100 km northeast of Tokyo. The 3 GeV rapid cycling synchrotron (RCS) will be used for a 1 MW neutron spallation source and muon source. The 50 GeV synchrotron with 0.75 MW proton beams will generate various secondary particles, such as neutrinos for T2K experiment and kaon beams for the study of kaonic nuclei, hypernucleim and kaon rare-decays.
 
"We will offer a world-class high power proton beam in various fields of research," says the J-PARC director Shoji Nagamiya. "The beam power is a product of the beam energy and the current. It is our next goal to inject proton beams from the linac into the 3 GeV synchrotron. Also, our next goal is to increase the beam current at the Linac. We plan to start injecting protons into the 3 GeV synchrotron by this fall."