Abstract
The High Luminosity LHC project (HL-LHC) foresees the construction and installation of important new equipment to increase the performance of the LHC machine. The Hollow Electron Lens (HEL) is a promising system to control the beam halo. It improves the beam collimation system of the HL-LHC and mitigates possible equipment damage in case of failure scenarios from halo losses. The halo can store up to 30 MJ energy. The specifications for this new device are quite demanding. The source, an electron gun with an annular shaped cathode, has to deliver a current up to 5 A. This is five times higher than the current in the existing electron lenses in Fermi and Brookhaven national laboratories. This note describes the programme carried out to design and test high-perveance guns equipped with two types of high-performance scandate cathodes. The size of the final gun is now considerably smaller than the one of the first prototype, allowing a reduction of diameter and cost of the superconducting magnet system used to steer the electron beam. The tests carried out at FNAL, BVERI and BJUT demonstrated that the developed cathodes fulfil the specifications and can supply a 5 A fully Space Charge Limited (SCL) current.
Highlights
HOLLOW ELECTRON LENSES FOR High Luminosity LHC (HL-LHC)The Large Hadron Collider (LHC), at CERN, is the largest and most powerful accelerator for high-energy physics [1]
The manipulations needed to prepare the beams for collision and the collisions for physics entail unavoidable beam losses, which generally become greater as the beam current and the Hollow electron lenses (HEL) are a promising method to improve the beam collimation system
HEL are expected to boost the performance of the LHC and of its HighLuminosity upgrade, through active control of halo particles’ diffusion speed and tail population [3]
Summary
HOLLOW ELECTRON LENSES FOR HL-LHCThe Large Hadron Collider (LHC), at CERN, is the largest and most powerful accelerator for high-energy physics [1]. In the HEL an annular thermionic cathode emits the electron beam, which is accelerated and confined, compressed and steered by a magnetic field generated by a set of superconducting solenoids. In order to assess the possibility of reaching such a high current, a programme to design and test different cathodes and electron guns was launched about three years ago.
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