LEP’s legacy continues at the ESS

The last components of a radio-frequency (RF) power station equipped with a LEP klystron were recently shipped to the city of Lund in Sweden. The station will be used as an integration test stand at the European Spallation Source (ESS), with the purpose of training ESS engineers for the setting up of 154 RF stations needed in Lund.


A truck with the LEP klystron has arrived at ESS, in Lund.

A klystron that was originally part of the Large Electron-Positron Collider (LEP), CERN’s former flagship accelerator, will be used in the start-up phase of the world’s largest neutron source, the ESS. If this klystron could speak, it would have a long and interesting story to tell.

During LEP decommissioning and dismantling, 44 klystrons were put aside to be used for other projects. For about 20 of them, the high-voltage part was adapted in order to accommodate Linac4’s pulsed-RF operation. “Some of the klystrons were built in the 80s and already had 60,000 operation hours,” says Olivier Brunner, leader of the team responsible for the Linac4 high-power RF system. “Nevertheless, it turned out that they worked perfectly well for powering Linac4’s low-voltage cavities.”

One of the refurbished klystrons was installed in an RF power station at the SM18 test stand and used to test and condition a significant number of the Linac4 cavities. After the successful conditioning campaign, the RF power station with the LEP klystron found other uses. Since the end of October, its new home has been the test stand of the ESS, where it will be used to train ESS staff. 

An artist's impression of what the ESS should look like in 2019.

Indeed, the 154 RF transmitter stations that will be installed in 2019 in the ESS linear accelerator are, in many respects, similar to the Linac4 ones. In order to gain experience with the stations, the ESS staff will rehearse with the Linac4 power station. “This is especially important in view of the tight schedule of the ESS installation phase, which is planned for mid-2019 and envisages an average pace of one RF transmitter installed every 3.5 days,” says David McGinnis, an engineer at ESS and the person in charge of the integration test stand.

If everything goes well, the LEP klystron, at around 30 years of age, will come back from Sweden in spring 2017 and become a back-up machine for Linac4.

Live long and prosper, LEP legacy!

by Stefania Pandolfi