Gas Electron Multipliers for the Antiproton Decelerator

The new beam profile measurement for the Antiproton Decelerator (AD) at CERN is based on a single Gas Electron Multiplier (GEM) with a 2D readout structure. This detector is very light (~0.4% X0), and measures horizontal and vertical profiles directly in one plane. This overcomes the problems previously encountered with multi-wire proportional chambers for the same purpose, where beam interactions with the detector severely affect the obtained profiles. A prototype was installed and successfully tested in late 2010, with another five detectors now installed in the ASACUSA and AEGIS beam lines. This paper will provide a detailed description of the detector and discuss the results obtained.Comment: Paper presented at DIPAC 2011, Hambur

LEIR Commissioning

The Low Energy Ion Ring (LEIR) is a central piece of the injector chain for LHC ion operation, transforming long Linac 3 pulses into high density bunches needed for LHC. LEIR commissioning is scheduled to be completed at the time of the conference. A review of LEIR commissioning highlighting expected and unexpected problems and actions to tackle them will be given

Specification of a new electron cooler for the low energy ion accumulator ring, LEIR

For the cooling of Pb**5**4**+ ions in the future low-energy ion ring machine a new electron cooling device needs to be constructed. This new cooler will take advantage of all the recent developments in electron cooling in order to balance efficient and fast cooling with a sufficiently long ion beam lifetime for beam accumulation. This paper will present the special features of the device and how their combination will be used to obtain low emittance beams for transfer to the LHC

Recent highlights from the CERN-AD

The Antiproton Decelerator and cooling ring (AD) provides dense and cold beams of antiprotons to low energy experiments for the study of basic properties of antiprotons and antihydrogen. It combines stochastic cooling (at 3.5 and 2GeV/c) with electron cooling at 0.3 and 0.1GeV/c. In 2002 the AD gave beam during more than 1900h to its three experiments (ASACUSA, ATHENA and ATRAP) with beam properties meeting, and often exceeding design specification. Stochastic cooling with cool-down times of 18s works as aimed for in the design. Electron cooling using the "old LEAR cooler" reaches the very small equilibrium emittances required but still takes more time (12s instead of 6s anticipated in the 1996 design). However the increase in cycle length is made up for by the higher deceleration efficiency. ASACUSA has very successfully continued the program of antiprotonic helium 3 spectroscopy and ATHENA and ATRAP have reported last autumn the synthesis of copious numbers of cold antihydrogen atoms

40 Years of Electron Cooling at CERN

For nearly 40 years electron cooling has been used extensively on the storage rings of the CERN accelerator complex for the accumulation of ions or for the improvement of beam quality for precision experiments. Since the first cooling experiments on ICE the coolers have evolved to incorporate the latest advances in electron cooling technology and many unique experiments have also been performed when the coolers are not used for everyday operation. The trapping of anti-hydrogen atoms and more recently lead-lead and proton-lead ion collisions in the LHC have been made possible thanks to cooling in the AD and cooling and accumulation of lead ions in the LEIR respectively. The next cooler to be built at CERN will be installed on ELENA and will operate at electron energies below 350 eV. Many challenges lie ahead in operating at such a low energy with minimum perturbation to the storage ring. The present AD cooler, which has already seen two re-incarnations, will also be replaced with a new state-of-the-art device operating at higher energies in order to improve the quality of the antiproton beam in this ring

Design and Optimisation of the ELENA Electron Cooler Gun and Collector

Phase space compression of the antiproton beam in ELENA will be performed by a new electron cooler. The performance of the cooler is greatly influenced by the properties of the electron beam. Careful design of the electron gun electrodes, the quality of the guiding magnetic field and the efficient recuperation of the electrons in the collector ensure that the cooler performance is optimal. We have used COMSOL Multiphysics to design and optimise the complete electron cooler with particular attention to the gun and collector. This software suite uses physics interfaces for modelling common applications and then allows the user to combine the different interfaces in one multi-physics simulation

The CERN-ELENA Electron Cooler Magnetic System

Phase space compression of the antiproton beam in ELENA will be performed by a new electron cooler the performance of which is greatly influenced by the properties of the electron beam. Careful design of the electron gun electrodes, the efficient recuperation of the electrons in the collector and the quality of the guiding magnetic field ensure an optimal performance of the cooler. The ELENA cooler is a compact device incorporating an adiabatic expansion to reduce the electron beam temperature as well as electrostatic bending plates for efficient collection of the electron beam. The transverse components of the longitudinal field in the cooling section must be kept small (Bt/Bl ≤ 5x10-4) to ensure a minimal perturbation to the electron beam transverse temperature. The longitudinal field itself needs to be as low as possible such that the distortion to the closed orbit of the circulating ion beam due to the short 90° toroids is kept as small as possible. We present the solutions chosen to design and construct a magnetic system within the above constraints as well as the setup used to measure and optimise the magnetic field components

Commissioning of the SEM-Grid Monitors for ELENA

ELENA is a compact ring for cooling and further deceleration of 5.3 MeV antiprotons delivered by the CERN Antiproton Decelerator. It decelerates antiprotons to a minimum energy of 100 keV, creating special challenges for the beam instrumentation. These challenges have been addressed by an extremely sensitive SEM-Grid monitor which is also compatible with the UHV requirements of ELENA. Since November 2019 ELENA’s H⁻ ion source has been used to test the SEM-Grid monitors and since July 2020 the monitors have been used to commission the ELENA transfer lines. In this paper a summary of the features of the SEM-Grid will be given, and an overview of the commissioning activities. A technique for testing the integrity of an inaccessible pickup wire will also be described

Stability and Lifetime Studies of Carbon Nanotubes for Electron Cooling in ELENA

Electron cooling is a fundamental process to guarantee beam quality in low energy antimatter facilities. In ELENA, the electron cooler reduces the emittance blow-up of the antiproton beam so that a focused and bright beam can be delivered to the experiments at the unprecedentedly low energy of 100 keV. To achieve a cold beam at this low energy, the electron gun must emit a monoenergetic and relatively intense electron beam. An optimization of the electron gun involving a cold cathode is studied to investigate the feasibility of using carbon nanotubes (CNTs) as cold electron field emitters. CNTs are considered among the most promising field emitting materials. However, stability data for emission over hundreds of hours, as well as lifetime and conditioning process studies to ensure optimal performance, are still incomplete or missing, especially if the aim is to use them in operation. This contribution reports experiments that characterize these properties and assess whether CNTs are suitable to be used as cold electron field emitters for many hundreds of hours