Cavities will be the heartbeat of the ILC, accelerating electrons and positrons to very high energies so that they can collide in the centre of the detectors. The ILC’s core technology, superconducting radiofrequency technology or SCRF, is also used in other accelerators, for example FLASH at DESY of the future European XFEL. Because they are so central to so many of its projects, and because they are also very attractive, DESY asked science photographer Heiner Müller-Elsner to follow a cavity almost from the mine to the module. Starting at the ingot of pure niobium, the cavity life story takes us to a big melting pot, numbered sheets, tests of all possible sorts, clean rooms and strings to the final cryomodule. Commissioned by ILC-HiGrade, which had at its core the SCRF cavity, Müller-Elsner shows the precision involved in all steps, the fascination of acceleration technology and of course the people that are involved in it.
Have a look at the slideshow to see a selection of the images. Or if you prefer total immersion: a photo exhibition opens on 30 May at DESY in Hamburg and Karsten Buesser from DESY will give a public talk called “Cool runnings – cold technology for fast particles”. The event starts at 7 p.m. in the auditorium, the exhibition will be on show for two weeks. More info here.
The irony of life: precisely the thing that will later pass through the cavity puts it through one of its first stages of life: an electron beam. The niobium ingot, held by a crane, is roughly two metres long and weighs about a tonne. In the electron beam melting machine the pure ingot is made even purer.When the liquid niobium drips off the ingot, all elements and gases evaporate, leaving the purest of materials. Six complete melting cycles, each lasting some 30 hours, are needed for one ingot.The ingot has been manufactured into a niobium sheet which is now checked carefully by eye and by machine to ensure high quality.A quality check by eye……and one by a specially developed scanning machine. It takes 10 minutes per sheet, one cavity consists of 18 sheets, so you can do the maths how long the scanning for the ILC’s 16000 cavities will take.The OBACHT automated cavity inspector has a little camera and clever software that searches out potential problems in a cavity.After all tests and checks, work in the clean room begins. Every single part that goes into the high-tech in a cryomodule has to be absolutely clean and free of dust and other impurities.Cavities are sealed into a helium tank, and eight of these tanks are assembled in a string.When all cavities are connected and hermetically sealed, the cavity string can leave the clean room and await insertion into a cryomodule.The final home (before the tunnel): the cryomodule. All images: Heiner Müller-Elsner
