Large-Scale Industrial Production of Superconducting Cavities

Many laboratories around the world, notably CEBAF, CERN, DESY and KEK, after a period of research and development, are presently or have recently been involved in the industrial production of a large number of RF superconducting cavities. CERN, instead of using the standard bulk niobium technique, has developed a new Nb/Cu technology (niobium film deposited by magnetron sputtering on copper). The aim of this paper is to present the transfer of this technology to three European firms [Ansaldo, CERCA and Siemens (now ACCEL)]. Emphasis will be placed on the major challenges to industry of mastering the very complex procedure (which requires high quality control at every stage of the production) needed to achieve a very demanding final RF performance [Q(6 MV/m) = 3.4¥109 at 4.5 K]

Superconducting RF Cavities: Past, Present and Future

In the last two decades many laboratories around the world, notably Argonne (ANL), TJNAF (formerly CEBAF), CERN, DESY and KEK, decided to develop the technology of superconducting (SC) accelerating cavities. The aim was either to increase the accelerator energy or to save electrical consumption or both. This technology has been used extensively in the operating machines showing good performances and strong reliability. At present, the technology using bulk niobium (Nb) or Nb coated on copper (Cu) is mature enough to be applied for many different applications, such as synchrotron light sources and spallation neutron drivers. Results, R&D work and future projects will be presented with emphasis on application to linear accelerators

A High-power Superconducting H−^- Linac (SPL) at CERN

The conceptual design of a superconducting H^- linear accelerator at CERN for a beam energy of 2.2 GeV and a power of 4 MW is presented. Using most of the superconducting RF cavities available after the decommissioning of LEP, it operates at 352 MHz and delivers 10^16 protons per second. At an early stage it will upgrade the performance of the PS complex by replacing Linac2 and the PS booster, by injecting protons directly into the PS. The brilliance of the LHC beam will thus be tripled. The present ISOLDE facility can be supplied with five times more beam current than to-day. In conjunction with an accumulator and a compressor, the purpose of its design is to be the proton driver of a neutrino factory at CERN.<br

The CERN Nb/Cu Programme for the LHC and Reduced-b Superconducting Cavities

The niobium/copper (Nb/Cu) sputter technology, successfully used on a large scale for LEP2, has been applied to the LHC and reduced-b superconducting (SC) cavities. For the LHC RF system the SC cavities were chosen, not only because of their high accelerating field leading to a small contribution to the machine impedance, but also because of their high stored energy which minimizes the effects of periodic transient beam loading associated with the high beam intensity (0.5 A). There will be eight single-cell cavities per beam, each delivering 2 MV (5.3 MV/m) at 400 MHz. In this paper the results of the industrial production of 21 cavities will be presented, and high-power test results on the prototype cryomodule reported. For the reduced-beta application an R&D programme at CERN was started in 1996. The goal is to demonstrate both the feasibility of such cavities and the possibility of producing them by low-cost modifications of LEP2 cavities (once LEP is decommissioned. Four different geometries were extensively tested (b = 0.48, 0.62, 0.66 and 0.8). In the present paper results obtained with single and multicell cavities will be presented, and a possible scenario for a superconducting proton linac will be reported

The quadrupole resonator: Construction, RF System Field Calculations and First Applications

The quadrupole resonator allows measurement of the RF properties of superconducting (sc) films deposited on disk-shaped metallic substrates. We describe the construction of the apparatus, the brazing and electron-beam welding procedures, the arrangements for compensating mechanical tolerances of samples and for assuring reproducible sample illumination. We explain the special features of the RF sy stem and give the results of field calculations with a 3D cavity code. Finally we present first measurements of Nb on Cu film samples and compare them with calibrations done with a bulk Nb sample

Production and Test of 352 MHZ Niobum-Sputtered Reduced-β\beta Cavities

Three types of 352 MHz single-cell cavities foreseen for different particle speeds (v/c=0.8, 0.625 and 0.48) have been designed and built with the niobium sputtered on copper technique. We report on the results of the cold tests at 4.5 and 2.5 K and the actual status of the data analysis

Various methods of manufacturing superconducting accelerating cavities

We report on experience in superconducting cavity production methods gained in shaping, joining and thin film coating with various materials and techniques (Pb, Nb, Nb$_{3}$Sn, NbN, NbTiN) with emphasis on their potential to reduce mass production costs

Design Considerations for the LHC 200 MHz RF System

The longitudinal beam transfer from the SPS into the LHC 400 MHz buckets will not be free of losses without a lower frequency capture system and a fast longitudinal damping system in LHC. We present a complete study of a combined system using four identical copper cavities at 200 MHz delivering 3 MV total CW voltage and having still enough bandwidth to achieve fast longitudinal damping. The shape of a cavity was designed according to the accelerating mode performance, its tuning and the higher order mode spectrum with respect to the LHC beam lines and their possible attenuation. The possibility to park the cavities during coast was included. The local heat load and the corresponding cooling water distribution as well as deformations were studied and techniques to build the cavity with all ports at low cost are proposed. The parameters of the RF generators, couplers and detuning are determined. Simulations of the total LHC RF system incorporating real delays, generator bandwidth and the control loops confirm that this system is capable of capturing and damping the beam longitudinally without losses

Analysis and results of the industrial production of the superconducting Nb/Cu cavities for the LEP2 project

For the energy upgrade of the Large Electron Positron Collider at CERN 216 RF superconducting cavities were ordered from three European industrial firms (Ansaldo, Cerca, Siemens/Accel) at the beginning of 1991. These cavities are made of copper (Cu), internally coated with niobium (Nb) according to a procedure developed at CERN. Up to now about 147 of these cavities fulfilling the specifications have been produced. The large-scale statistics available and the use of dedicated analytical and optical inspection techniques shed new light on the relationship between production procedures, niobium film properties and cavity performance. An overview of this subject is presented, together with some significant trends and results