ECLOUD'18chaired by , , Roberto Cimino
The sixth electron-cloud workshop, ECLOUD'18, will take place from 3 to 7 June, 2018 at La Biodola (Isola d'Elba) Italy. The existence of the electron-cloud effects (ECE’s) has been firmly established experimentally at essentially all modern positron and hadron storage rings, either via performance limitations or by deliberate provocation. The ECE is a consequence of the strong coupling between a positively charged particle beam and a cloud of electrons that inevitably develops inside the vacuum chamber. Resulting deleterious effects include beam instabilities, beam losses, emittance growth, increases in vacuum pressure, additional heat load on the vacuum chamber walls, and interference with certain types of beam diagnostics.
Electron-cloud effects remain dynamical phenomena which are only incompletely understood. While the fundamental mechanisms are well recognized and the qualitative picture is clear, the phenomena involve many surface properties and geometrical parameters of the vacuum chamber coupled in a nontrivial way with the beam characteristics. The ECE can also conspire with classical wake-field effects and/or the beam-beam interaction. In addition, the relevant time and energy scales span a wide range, and many of the essential parameters are not well known a priori. Hence the detailed prediction of ECE's at a given machine, not to mention the extrapolation from one machine to another, are subject to great uncertainty.
High-power microwave applications in modern satellites are perturbed by phenomena of multipacting and RF breakdown, which are governed by the same surface parameters as ECE in accelerators. Especially for multi-carrier signals, they exhibit very similar characteristics and electron-cloud build-up time scales, and can be modelled by similar simulation tools.
Since the last successful workshop ECLOUD’12, which also took place in La Biodola (Isola d'Elba) Italy, an intense R&D effort has been under way to further understand the physics of the electron cloud and to investigate new methods for the mitigation of its adverse consequences.
Electron cloud remains a major concern for the High Luminosity LHC and even for the actual LHC run 2. At CERN and worldwide a significant effort is also dedicated to the study of Future Circular Collider (FCC) options – involving both proton and electron-positron colliders which may suffer from electron cloud. As a consequence of the high synchrotron radiation, large bunch charge, and close bunch spacing in several of the FCC machines, the ECE’s are expected to be significant. It is urgent to better quantify and understand the associated phenomena to ascertain the feasibility of the performance goals. ECE’s have been noticeable during the first commissioning run of SuperKEKB in 2016. The next commissioning run from early 2018 onward will further raise the beam intensity.
The ECLOUD'18 program will focus on: a review of EC observations at existing machines; recent experimental efforts to characterize the EC (including EC diagnostics, experimental techniques, characterization of mitigation methods, and characterization of beam instabilities and emittance growth); the status of EC physics models and simulation codes and their comparison with recently acquired experimental data; and the mitigation requirements and potential performance limitations imposed by the EC on existing, upgraded and future machines.