‘First turns’ for SuperKEKB

18 March 2016

On 10 February, the SuperKEKB electron–positron collider in Tsukuba, Japan, succeeded in circulating and storing a positron beam moving close to the speed of light through 1000 magnets in a narrow tube around the 3 km circumference of its main ring. And on 26 February, it succeeded in circulating and storing an electron beam around its ring of magnets in the opposite direction.

The achievement of “first turns”, which means storing the beam in the ring through many revolutions, is a major milestone for any particle accelerator.

SuperKEKB, along with the Belle II detector, is designed to search for new physics beyond the Standard Model by measuring rare decays of elementary particles such as beauty quarks, charm quarks and τ leptons.

Unlike the LHC, which is the world’s highest-energy machine, SuperKEKB/Belle II is designed to have the world’s highest luminosity – a factor of 40 higher than the earlier KEKB machine, which holds many records for accelerator performance. SuperKEKB will therefore be the leading accelerator on the “luminosity frontier”.

The Belle II detector at SuperKEKB was designed and built by an international collaboration of more than 600 physicists from 23 countries. This collaboration is working closely with SuperKEKB accelerator experts to optimise the machine performance and backgrounds.

At the same time as first turns were achieved, the BEAST in its cave at Tsukuba Hall awakened from its slumber. The BEAST II detector is a system of detectors designed to measure the beam backgrounds of the SuperKEKB accelerator. The parasitic radiation produced by electromagnetic showers when the beam collides with the walls of the vacuum pipe not only obscure the signals that we wish to observe, but can also damage the detector. Therefore, when operating the new accelerator, these beam backgrounds must be well understood.

The BEAST II detector will collect data in the unique environment produced by SuperKEKB’s first beams, allowing Belle II to safely roll into the beam in 2017.

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