Abstract
Electron cooling is a fundamental process to guarantee the beam quality in low energy antimatter facilities. In extra low energy antiproton, the electron cooler reduces the emittance blowup of the antiproton beam and thus delivers a focused and bright beam to the experiments at the unprecedentedly low kinetic energy of 100 keV. In order to achieve a cold beam at this low energy, the electron gun of the cooler must emit a monoenergetic and relatively intense electron beam. An optimization of the extra low energy antiproton electron cooler gun involving a cold cathode is studied, with the aim of investigating the feasibility of using carbon nanotubes (CNTs) as cold electron field emitters. CNTs are considered among the most promising field emitting material. However, stability data for emission operation over hundreds of hours, as well as lifetime and conditioning process studies to ensure optimal performance, are still incomplete or missing, especially if the purpose is to use them in operation in a machine such as extra low energy antiproton. This manuscript reports experiments that characterize these properties and ascertain whether CNTs are reliable enough to be used as cold electron field emitters for many hundreds of hours.
Highlights
The extra low energy antiproton (ELENA) ring is the newest and most compact synchrotron decelerator at CERN with a circumference of only 30.4 m [1,2,3]
ultrahigh vacuum (UHV) and bakeout perfectly match the requirements of ELENA, where the nominal pressure is around 10−12 mbar and bakeout is part of the conditioning procedure
One of the biggest concerns about carbon nanotubes (CNTs) pertain to their lifetime and stability
Summary
The extra low energy antiproton (ELENA) ring is the newest and most compact synchrotron decelerator at CERN with a circumference of only 30.4 m [1,2,3]. During the deceleration process the beam emittance, or transverse energy, increases due to adiabatic blowup, intrabeam scattering, and scattering with residual gas species in the beam pipe. This leads to losses and a poor-quality beam which is not very useful for the experiments. To counteract these effects, electron cooling [5] is applied to reduce the longitudinal and transverse energy spreads of the antiproton beam, leading to an increased phase-space density. The cooling process takes place twice during ELENAs beam cycle [9,10]: (i) First cooling plateau, where the antiproton beam with kinetic energy 650 keV (momentum 35 MeV=c) is cooled by an electron beam
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