In response to the 2013 Update of the European Strategy for Particle Physics, the Future Circular Collider (FCC) study was launched, as an international collaboration hosted by CERN. This study covers a highest-luminosity high-energy lepton collider (FCC-ee) and an energy-frontier hadron collider (FCC-hh), which could, successively, be installed in the same 100 km tunnel. The scientific capabilities of the integrated FCC programme would serve the worldwide community throughout the 21st century. The FCC study also investigates an LHC energy upgrade, using FCC-hh technology. This document constitutes the second volume of the FCC Conceptual Design Report, devoted to the electron-positron collider FCC-ee. After summarizing the physics discovery opportunities, it presents the accelerator design, performance reach, a staged operation scenario, the underlying technologies, civil engineering, technical infrastructure, and an implementation plan. FCC-ee can be built with today’s technology. Most of the FCC-ee infrastructure could be reused for FCC-hh. Combining concepts from past and present lepton colliders and adding a few novel elements, the FCC-ee design promises outstandingly high luminosity. This will make the FCC-ee a unique precision instrument to study the heaviest known particles (Z, W and H bosons and the top quark), offering great direct and indirect sensitivity to new physics.

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FCC-ee: The Lepton Collider: Future Circular Collider Conceptual Design Report Volume 2

Beam loading of RF cavities is a subject of great concern for the design and operation of high current circular accelerators and storage rings. The steady state and transient perturbations of the accelerating voltage by the beam current lead to undesirable beam behaviour, like for instance the onset of instabilities or particle loss by lack of longitudinal acceptance. To some extent, it is possible to alleviate or even completely suppress these effects by a proper control of the RF power amplifier - cavity combination, using feedback or feedforward techniques. Several new developments in this field have taken place during the past years. For instance, the implementation of fast feedback technology, the use of cavity compensation schemes or digital filtering of signals in long delay feedback systems have resulted in considerably improved machine performance. Such techniiques will be reviewed in this paper and their performance and limitations will be presented.

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Control of Cavities with High Beam Loading

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Advanced Photon Source Upgrade Project preliminary design report

vii Chapter 1 The NuMI Beam 1 1.1 NuMI Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2 The Primary Proton Beam . . . . . . . . . . . . . . . . . . . . 6 1.3 Meson Production Target . . . . . . . . . . . . . . . . . . . . 10 1.4 Meson Focusing with Magnetic Horns . . . . . . . . . . . . . . 15 1.5 Decay Volume and Downstream Components . . . . . . . . . . 31 1.6 MINOS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 1.7 Outline of This Dissertation . . . . . . . . . . . . . . . . . . . 41 Chapter 2 The Fermilab Accelerators 43 2.1 Preaccelerator . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 2.2 Linac . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 2.3 Booster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 2.4 Main Injector . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 2.5 Antiproton Source & Recycler . . . . . . . . . . . . . . . . . . 57 2.6 Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

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Accelerator systems and instrumentation for the NuMI neutrino beam

Experimental with alpha particles at the CERN intersecting storage rings

In the CERN SPS proton synchrotron the four accelerating cavities are of the travelling wave structure type. At the 10 GeV/c injection energy the cavities present to the beam an impedance very similar to that of a detuned RLC cavity with the result that strong dipole and quadrupole instabilities occur. The SPS accelerated beam current was limited by the combined action of these two effects to 2.5 X 10/sup 13/ protons which resulted in capture losses increasing with the injected beam intensity. Among the solutions possible for this problem, the RF feedback, which would alleviate both transient beam loading and instability effects, looked to the authors to be the most promising. In such a system the total voltage seen by the beam is reinjected into the feedback cavity via its power amplifier. Without any delay in the system the cavity impedance seen by the beam could be greatly reduced. Unfortunately the long delay in the system severely limits the bandwidth and the RF feedback could hardly correct more than the n = O beam loading component. The authors circumvented this problem by observing that they needed a large gain only in the vicinities of the RF frequencies. Outside these bandsmore » the phase rotation due to the long delay is unimportant if the gain is made low enough. If, in addition, the total delay of the system is made exactly equal to one machine turn, the open loop phase of the feedback system is always zero for each RF frequency. The two ingredients needed to make the RF feedback work for n not too small are therefore a transfer function with comb filter shape and a total delay of one machine turn. In this paper these ingredients are derived.« less

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Reduction of the Apparent Impedance of Wide Band Accelerating Cavities by RF Feedback

Simultaneous acceleration of several beams in the same machine by several RF fields of slightly different frequencies was already considered a long time ago1,2). As they rotate at different frequencies, the bunches will periodically coincide in azimuth, thus producing beams of high local line density. Bunches rotating at different frequencies can be produced either outside the machine (e. g. in the injector) or even inside by appropriate modulation of the RF cavities. These techniques will be used in the p-p? project at CERN. A high line-density proton beam, necessary for antiproton production, is obtained in the CPS by azimuthal combination, either at the injection or at the ejection level. On the other hand, the antiproton bunches in the SPS must be azimuthally combined before storage in order to achieve the design luminosity. Computer simulation and RF manipulations of these procedures, as well as experimental results already obtained at the CPS, are presented.

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Production of Beams with High Line-Density by Azimuthal Combination of Bunches in a Synchrotron

The CERN-PS beam intensity is being steadily increased (1.55 10’ 3 protons per pulse achieved). In addition, a change of harmonic number by debunchingrebunching is performed to allow a clean bunch-intobucket injection into the SPS. Many collective phenomena had to be studied in this context lately, and selected results of interest to machine designers or operators are reported here. Topics covered are resistive-wall instabilities with peculiar characteristics due to space-charge detuning and fast-decaying wakes, microwave longitudinal instabilities, and problems associated with strong cavity beam-loading.

Collective Effects at Very High Intensity in the CERN-PS

Deuteron acceleration in the CERN 50 MeV Linac has been tried out already 13 years ago followed by programmed acceleration in tne CPS up to about 100 MeV.

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D. Boussard

Papers

Control of Cavities with High Beam Loading

Reduction of the Apparent Impedance of Wide Band Accelerating Cavities by RF Feedback

Production of Beams with High Line-Density by Azimuthal Combination of Bunches in a Synchrotron

Collective Effects at Very High Intensity in the CERN-PS

Acceleration and Stacking of Deuterons in the CERN PS and ISR