KEK’s accelerator test facility, ATF, has many components installed on its beamline, many of which come from other laboratories around the world. From 21 May to 6 June, two scientists from the US laboratory SLAC, Janice Nelson and Glen White, came to ATF to check and recover systems that they are responsible for: the cavity beam position monitor (BPM) system (in collaboration with Royal Holloway) and the magnet mover system on the ATF2 beamline.
“There was damage from the earthquake,” said Nelson. The ATF2 magnet mover system is equipped with some 90 sensors and six of those were completely broken. They also identified damage to the crate containing electrical devices that monitor and provide controls to the cavity BPM system, the devices capable of measuring the x- and y-axis positions of the electron beam. “We asked our SLAC colleagues to send a crate while we are here in Japan. Once that arrived, and the bad crate was replaced, the system was brought back online,” said Nelson. Thanks to the scientists’ dedication, all the recovery work was completed in two weeks.
Nelson and White were the first overseas visitors to see ATF after the March 2011 earthquake. Many of the conferences planned to be held in Japan were cancelled, and some scientists expressed hesitation in even coming to Japan. “I was worried about colleagues here at KEK, and coming to see that everyone is OK was one of the purposes of this visit. I did not worry about the damage to myself,” said Nelson. “We very much want to help our Japanese colleagues. Our particular systems are important to the whole system. We wanted to fix them as soon as possible so that they could recover the beam.”
Usually, SLAC physicists can remotely monitor the systems at ATF from SLAC, but because of the power shutdown, they could not know what was going on until they actually came to KEK. “It is very difficult for me to understand how big the earthquake was,” said Nelson, who noted that she did not know what to expect. “Magnitude 9.0 earthquake – what does it mean?” She saw evidence that very heavy equipment had been moved, shaken and slammed around. But the size of damage to the magnet movers was small enough that they were easy to recover.
“But we came here with more ambitions,” Nelson said. They came with a plan to upgrade one of the mover systems, to make it move faster, and will conduct a test on one unit. “With the SLAC systems recovered enough for beam use, we are working hard to begin the upgrade tests. We will be back again to finish the upgrade.”
The checkout for the beam at ATF is moving forward. On Friday, 3 June, KEK scientists confirmed a test beam reached the beam dump at the end of ATF2, which was extracted without a significant amount of beam loss. “We still have a lot of things to check: the intensity in the ring, emittance and many beam instruments,” said Nobuhiro Terunuma of KEK, a spokesperson for the ATF international collaboration. The hard work will be continued during the planned summer shutdown, during which scientists aim to accomplish as much work as possible.