Uppsala University, Uppsala
At CERN the feasibility of CLIC (Compact LInear Collider) a multi-TeV electron-positron collider is being studied. In this scheme the RF power to accelerate the main beam is produced by a high current drive beam. To demonstrate this scheme a test facility (CLIC Test Facility 3, CTF3) has been constructed at CERN. Recently, the complex to generate the drive beam has been successfully commissioned producing a beam with a current around 30A. This beam is now being used to test the power production. The results of the test facility provide vital input for the CLIC conceptual design report to be finished by the end of 2010. This talk describes CTF3 activities and their importance for CLIC; it comments on design readiness for CLIC after a successful CTF3 demonstration.
Fermilab, Batavia
INFN/LNF, Frascati (Roma)
An algorithm for the simultaneous optimization of orbit, dispersion, coupling and beta-beating in the final focus of future linear colliders is presented. Based on orbit and dispersion measurements the algorithm determines the optimal corrector settings in order to simultaneously minimize the r.m.s orbit, the r.m.s dispersion, the r.m.s coupling, the r.m.s. beta-beating and the r.m.s strength of the dipoles correctors. A number of different options for error handling of beam position monitors, weighting, and correction have been introduced to ensure the stability of the algorithm. A sextupole tuning procedure is also applied to further optimize the beam parameters at the interaction point. Preliminary results for the beam delivery systems of CLIC are presented.
KEK, Ibaraki
The international linear collider (ILC) project is about to meet the technical design phase 2, of which the goal is to establish a realistic design by the end of 2012. Single-tunnel accelerator configuration is one of the most essential improvements to reduce the construction costs. The original design involves two tunnels which house the accelerator cavities and the power supplies separately, having such advantages as we can enter the power-supply tunnel even during beam operation. Although the single tunnel configuration sacrifices these functions, it saves big tunnel construction costs. The Asian team is studying a regional single-tunnel accelerator configuration to match the Asian site feature in conjunction with a compact high-level RF scheme called distributed RF system (DRFS). The design concepts have been developed by a conventional facility working group in the advanced accelerator association (AAA) which involves a collaboration among academic, industrial, and political communities in Japan. Not only cost reduction but also functional impacts of tunnel configuration on things such as life safety are discussed in this paper.
CERN, Geneva
EPFL, Lausanne
HIP, University of Helsinki
Optimizing the design and the manufacturing of the CLIC RF accelerating structures for achieving the target value of breakdown rate at the nominal accelerating gradient of 100 MV/m requires a detailed understanding of all the steps involved in the mechanism of breakdown. These include surface modification under RF fields, electron emission and neutral evaporation in the vacuum, arc ignition and consequent surface modification due to plasma bombardment. Together with RF tests, experiments are conducted in a simple DC test set-up instrumented with electrical diagnostics and optical spectroscopy. The results are also used for validating simulations which are performed using a wide range of numerical tools (MD coupled to electrostatic codes, PIC plasma simulations) able to include all the above phenomena. Some recent results are presented in this paper.
KEK, Ibaraki
CERN, Geneva
Politecnico/Milano, Milano
To investigate the breakdown characteristic related to the differences in purity and hardness, four types of oxygen-free copper (OFC) materials, usual class 1 OFC with/without diamond finish, 7-nine large-grain copper and 6-nine hot-isotropic-pressed copper, were tested with the DC spark test system at CERN. Measurements of beta, breakdown fields and breakdown probability are discussed followed by the surface inspection mostly with SEM on the tested materials.
HIP, University of Helsinki
CERN, Geneva
Helsinki University, Department of Physics, University of Helsinki
The Compact Linear Collider (CLIC) is currently under development at CERN as a potential multi-TeV e+e' collider. The manufacturing and assembly tolerances for the required RF components are essential for the final efficiency and for the operation of CLIC. The proper function of an accelerating structure is sensitive to mechanical errors in the shape and the alignment of the accelerating cavity. The current tolerances are in the micron range. This raises challenges in the field of mechanical design and demands special manufacturing technologies and processes. Currently the mechanical design of the accelerating structures is based on a disk design. Alternatively, it is possible to create the accelerating assembly from quadrants, which has the potential to be favoured for the mass production due to simplicity and cost. In this case, the functional shape inside of the accelerating structure remains the same and a single assembly uses less parts. This paper focuses on the development work done in design and simulation for prototype accelerating structures and describes its application to series production.
Fermilab, Batavia
UCR, Riverside, California
IIT, Chicago, Illinois
Illinois Institute of Technology, Chicago, Illinois
Muon ionization cooling provides the only practical solution to prepare high brilliance beams necessary for a neutrino factory or muon colliders. The muon ionization cooling experiment (MICE) is thus a strategic R&D project for neutrino physics. It is under development at the Rutherford Appleton Laboratory (UK). It comprises a dedicated beam line to generate a range of input emittance and momentum, with time-of-flight and Cherenkov detectors to ensure a pure muon beam. A first measurement of emittance is performed in the upstream magnetic spectrometer with a scintillating fiber tracker. A cooling cell will then follow, alternating energy loss in liquid hydrogen and RF acceleration. A second spectrometer identical to the first one and a particle identification system provide a measurement of the outgoing emittance. In the 2010 run, completed in August, the beam and most detectors have been fully commissioned. The time of the first measurement of input beam emittance is closely approaching. The plan of steps of measurements of emittance and emittance reduction (cooling), that will follow in 2011 and later, will be reported.
I submit this as chair of the MICE speakers bureau. If accepted, I will find a member of the collaboration that will register to the conference and present the contribution.
CERN, Geneva
This talk gives an overview of recent results and future prospects on RF sources for linac applications, including klystrons, magnetrons and modulators.
Texas A&M University, College Station, Texas
JLAB, Newport News, Virginia
A 1.3 GHz superconducting test cavity is being developed to test wafer samples of advanced SRF materials with surface fields at or beyond the Nb BCS limit. The mushroom-shaped Nb cavity is dielectric-loaded, with a hemisphere of high-purity sapphire located just above a detachable end flange. Wafer samples are mounted on the end flange. The cavity is operated in the TE011 mode, so no currents flow from the end flange to the side walls. Fields are concentrated on the wafer sample so that the peak surface field there is 4 times greater than anywhere else on the cavity walls. The loss tangent of ultrapure sapphire is critical to the performance of the test cavity. A separate first experiment has been conducted in a special 1.8 GHz cavity to measure this loss tangent in L band as a function of temperature for the first time. Results of the measurement and the final design of the ultimate-gradient test cavity will be presented.
KEK, Ibaraki
A CERN-SLAC-KEK collaboration on high gradient X-band accelerator structure development for CLIC has been ongoing for the past three years. A major outcome has been the stable 100 MV/m gradient operation of a number of CLIC prototype structures. The design of the structures, which have very strong higher-order-mode damping, is based on newly developed high-power scaling laws. The structures are being fabricated using the technology which was developed in the GLC/NLC projects which is giving excellent reproducibility. The features of this new generation of high-gradient normal conducting structures and their testing results are reviewed.
SLAC, Menlo Park, California
We present the results of R&D aimed at exploring the basic physics of RF breakdown phenomena in high vacuum structures. We performed an extensive experimental survey of materials for RF magnetic field induced metal fatigue. To do this, we designed a cavity operating at a TE01m-like mode which focuses RF magnetic field on the flat sample surface. We tested more than 20 samples of materials including single crystal copper, copper alloys, and refractory metals. With these results in hand, we constructed standing wave cavities of different geometries and materials to conduct RF-breakdown experiments. To study a broad range of materials and surfaces, we explored different structure-joining techniques, including those which allow us to avoid high temperature brazing. Using structures of different geometries, we examined the effect of the mixture of surface electric and magnetic fields on breakdown behavior. To study this effect further we designed a structure in which we can adjust the mixture of fields using two independent RF sources.
Fermilab, Batavia
Over the last decade there has been significant progress in developing the concepts and technologies needed to produce, capture and accelerate O(1021) muons/year. This development prepares the way for a new type of neutrino source (Neutrino Factory) and a new type of very high energy lepton-antilepton collider (Muon Collider). A review is given of the motivation, design and R&D for Neutrino Factories and Muon Colliders.