The shiny blue and yellow structure looks rather like a giant game of Connect Four. In fact, it is the newly installed PS Booster injection system, which will receive negative hydrogen ions from Linac4 and strip them of their two electrons, before sending them off to the Booster’s four rings. The insertion of this key component of the new accelerator marks the completion of an important stage of the work being carried out on the 215 metres of beam lines that make up the PS Booster complex.
The PS Booster will be completely overhauled during Long Shutdown 2 (LS2) in the framework of the LHC Injector Upgrade project (LIU). Many components, notably numerous magnets and the radiofrequency acceleration system, have been dismantled and extracted, and the teams are preparing for the arrival of their replacements. Surveyors are marking out the locations of the components of the injection and extraction lines on the ground with great precision, while teams install the service networks (electrical cables, cooling and ventilation ducts).
The new acceleration system, which is based on Finemet technology and was developed in collaboration with KEK in Japan, is being installed. The first of the three structures that will house the radiofrequency cavities was inserted into the Booster on Thursday, 6 June and, since then, the teams have been busy fitting it with all its equipment.
Each structure contains eight cavities and 48 power amplifiers and is assembled entirely on the surface, before being emptied of its components, ready to be transported. “Each structure weighs 1.5 tonnes, rising to almost 5 tonnes with the cavities and the amplifiers. That’s why we have to dismantle them, transport them and then reassemble them in the accelerator,” explains Matthias Haase, who is coordinating the installation of the cavities.
His computer screen shows information pertaining to the roughly 1500 connecting cables that he has patiently inventoried, numbered and mapped. These plans will enable the cable fitters to connect the RF structures to the power supply and to the control room, using power and signal cables. It’s painstaking work, involving specific constraints relating to the sensitivity of the radiofrequency signals. The cables that transmit the commands to the cavities must be exactly the same length for all three structures, or else the three sets of cavities will not be in sync. “A few centimetres make all the difference,” says Matthias Haase.
The cavity installation will continue until October, when testing will start, and the commissioning of the new acceleration system will begin in November.