Abstract
The new 735m long linear accelerator “SwissFEL” at the Paul Scherrer Institute (PSI) in Wurenlingen is extremely sensitive against vibrations coming from surrounding equipment (pumps, ventilators, transformers, etc.). The manufacturer’s vibration limit for this linear accelerator is 0.1μm displacement amplitude. Therefore, all vibration sources must strictly be isolated to the highest-possible degree from the rest of the structure. This paper discusses the vibration situation in general for this unique construction (ground vibrations, vibration propagations / structural amplifications, vibration limits, etc.) and as a case study the isolation of a pump located in the building. Steel springs were used and it was achieved to reduce the vibration transmitted to the floor by more than 99%, to a level where the coherent component of the motion recorded on the floor next to the linear accelerator is non-measurable / below the ground motions. The measurements were found to be in good accordance with the FEM model used.
Highlights
The Swiss Free Electron Laser (FEL) is located in the Paul Scherrer Institute (PSI) in Würenlingen
Electron beams are accelerated through linear accelerators, located in a concrete tunnel of 735 m length
The allowable displacements are very strict and the design and construction of the FEL was done with great care in order not to exceed them
Summary
Electron beams are accelerated through linear accelerators, located in a concrete tunnel of 735 m length. Afterwards they are sent into an array of alternatively poled magnets which deflect them into a wavy path. In order for the FEL to function properly, very strict structural displacement values are allowed, both under static and under dynamic loading. The allowable displacements are very strict and the design and construction of the FEL was done with great care in order not to exceed them. Their exceedance would lead to the malfunction of FEL. Some sources of vibration had to be elastically supported and decoupled from the building
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