The probe beam linac in CTF3

JACoW web site http://accelconf.web.cern.ch/AccelConf/e06/The test facility CTF3, presently under construction at CERN within an international collaboration, is aimed at demonstrating the key feasibility issues of the multi-TeV linear collider CLIC. The objective of the probe beam linac is to "mimic" the main beam of CLIC in order to measure precisely the performances of the 30 GHz CLIC accelerating structures. In order to meet the required parameters of this 200 MeV probe beam, in terms of emittance, energy spread and bunch-length, the most advanced techniques have been considered: laser triggered photo-injector, velocity bunching, beam-loading compensation, RF pulse compression ... The final layout is described, and the selection criteria and the beam dynamics results are reviewed

The Compact Linear Collider (CLIC) - 2018 Summary Report

The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear $e^+e^-$ collider under development at CERN. Following the CLIC conceptual design published in 2012, this report provides an overview of the CLIC project, its current status, and future developments. It presents the CLIC physics potential and reports on design, technology, and implementation aspects of the accelerator and the detector. CLIC is foreseen to be built and operated in stages, at centre-of-mass energies of 380 GeV, 1.5 TeV and 3 TeV, respectively. CLIC uses a two-beam acceleration scheme, in which 12 GHz accelerating structures are powered via a high-current drive beam. For the first stage, an alternative with X-band klystron powering is also considered. CLIC accelerator optimisation, technical developments and system tests have resulted in an increased energy efficiency (power around 170 MW) for the 380 GeV stage, together with a reduced cost estimate at the level of 6 billion CHF. The detector concept has been refined using improved software tools. Significant progress has been made on detector technology developments for the tracking and calorimetry systems. A wide range of CLIC physics studies has been conducted, both through full detector simulations and parametric studies, together providing a broad overview of the CLIC physics potential. Each of the three energy stages adds cornerstones of the full CLIC physics programme, such as Higgs width and couplings, top-quark properties, Higgs self-coupling, direct searches, and many precision electroweak measurements. The interpretation of the combined results gives crucial and accurate insight into new physics, largely complementary to LHC and HL-LHC. The construction of the first CLIC energy stage could start by 2026. First beams would be available by 2035, marking the beginning of a broad CLIC physics programme spanning 25-30 years

Results of SC proton cavity tests (B = 1 and B = 0.65)

The two superconducting cavities were carefully designed for challenging performance. They were fabricated in industry with intermediate tests and specialized processing in CEA and CNRS. The results are promising, except for a degradation of the field flatness of the low velocity cavity, after electron-beam welding. This might reduce the accelerating gradient. Due to delays in manufacturing, the final performance tests will be carried out in the coming months

Multipactor studies for the FCC-ee superconducting SWELL cavities

International audienceThe Future Circular electron-positron Collider (FCCee) is a proposed new storage ring of 91 km circumference, which has been designed to carry out a precision study of Z, W, H, and ttbar with an extremely high-luminosity and unprecedented energy resolution. Given the high-energies, ranging from 45.6 to 183 GeV, the Synchrotron Radiation (SR) power is assumed to be limited to 50 MW per beam in all operation modes. A high-performance RF system based on Superconducting Cavities (SC) is supposed to compensate for SR losses. Different SC technologies are currently under study for such a system, the Slotted Waveguide ELLiptical (SWELL) being one of the possible solutions. In this paper, we numerically compute the position of the multipacting barriers of a SWELL cavity prototype, resonating at 1.3 GHz. We benchmark it against the TESLA cavity barriers, which are well documented. First results show that the SWELL cavity is less prone to multipacting in its operation range than the equivalent TESLA one

Development of vertical electropolishing process applied on 1300 and 704 MHz superconducting niobium resonators

An advanced setup for vertical electropolishing of superconducting radio-frequency niobium elliptical cavities has been installed at CEA Saclay. Cavities are vertically electropolished with circulating standard HF-HF-H_{2}SO_{4} electrolytes. Parameters such as voltage, cathode shape, acid flow, and temperature have been investigated. A low voltage (between 6 and 10 V depending on the cavity geometry), a high acid flow (25  L/min), and a low acid temperature (20° C) are considered as promising parameters. Such a recipe has been tested on single-cell and nine-cell International Linear Collider (ILC) as well as 704 MHz five-cell Super Proton Linac (SPL) cavities. Single-cell cavities showed similar performances at 1.6 K being either vertically or horizontally electropolished. The applied baking process provides similar benefit. An asymmetric removal is observed with faster removal in the upper half-cells. Multicell cavities (nine-cell ILC and five-cell SPL cavities) exhibit a standard Q_{0} value at low and medium accelerating fields though limited by power losses due to field emitted electrons