CERN Developments for 704 MHz Superconducting Cavities (original) (raw)

Use of Niobium for Fabricating Superconducting Radio Frequency Cavities

Since the pioneer work done by the High-Energy Physics Lab at Stanford University in 1965, superconducting radio frequency (SRF) technology has been developing steadily up to now. Demanding on niobium (Nb) has been increasing constantly, since more and more particle accelerators select Nb based SRF technology as a key part of their accelerator constructions. For example, the proposed International Linear Collider (ILC) that will probe new physics using TeV collisions of electron and positron beams will need approximately 17,000 1-meter-long Nb SRF cavities. Others such as x-ray free electron laser (XFEL) at DESY in Germany, energy recovery linac (ERL) at Cornell University in USA, the new Spiral 2 facility in France, the isotope separation and acceleration (ISAC) II in Canada, and the 12 GeV upgrade of CEBAF at Jefferson Lab in USA will all require Nb. This popularity in Nb can be, at least partially, attributable to the unique physical and mechanical properties that Nb possesses ---the highest superconducting transition temperature of 9.25 K and the highest superheating field of 0.23 T among all available pure metals with excellent ductility that enables machining to be done relatively easily. In this chapter, the use of Nb for fabricating SRF cavities is reviewed, giving particular attention to some examples of important new developments in the past decade on reducing the production costs and increasing the throughput of high quality Nb SRF cavities. Some R&D examples on the study of the requirements in the physical, chemical, metallurgical, and mechanical properties of Nb for the applications in particle accelerators based on Nb SRF technology are updated and reviewed. This chapter also includes some unpublished experimental results from my own research. Hopefully this review can be served as a useful reference for new researchers who want to use Nb for their various R&D projects in particle accelerators and for Nb suppliers and manufacturers who want to provide the best and the most economic products to be used in particle accelerators.

Prototyping of a Superconducting Elliptical Cavity for a Proton Linac

An L-band superconducting cavity has been designed for acceleration of particles travelling at 81% the speed of light (β = 0.81). Four single-cell prototypes have been being fabricated and tested. Two of these cavities were formed from standard high purity fine grain niobium sheet. The rest were fabricated from large grain niobium. The RF per- formance of the single-cell cavities indicate that the design is suitable for use in a proton linac; the highest measured accelerating gradient was about 28 MV/m. The fabrication of two 7-cell cavity prototypes is in progress.

Performance Overview of the Production Superconducting RF Cavities for the Spallation Neutron Source Linac

Proceedings of the 2005 Particle Accelerator Conference, 2005

As part of its efforts for the SNS construction project, Jefferson Lab has produced 23 cryomodules for the superconducting linac. These modules contained 81 industrially produced multicell Nb accelerating cavities. Each of these cavities was individually tested before assembly into a cryomodule to verify that they achieved the required performance. This ensemble of cavities represents the 3rd largest set of production superconducting cavities fabricated and tested to date. The timely qualification testing of such a collection of cavities offers both challenges and opportunities. Their performance can be characterized by achieved gradient at the required Qo, achieved peak surface field, onset of field emission, and observations of multipacting. Possible correlations between cavity performance and process parameters, only really meaningful in the framework of a large scale production effort, will also be presented. In light of the potential adoption of these cavities for projects such as the Rare Isotope Accelerator or Fermilab Proton Driver, such an analysis is crucial to their success.

Development, Production And Tests Of Prototype Superconducting Cavities For The High Beta Section Of The Isac-ii Heavy Ion Accelerator At Triumf

The medium beta section of the ISAC-II heavy ion superconducting linear accelerator, consisting of 20 cavities, has been in operation at TRIUMF since 2006. The high beta section of the accelerator, consisting of an additional twenty cavities, is currently under development and is scheduled for completion in 2009. The cavity is a superconducting bulk Niobium two-gap quarter-wave resonator for frequency 141 MHz, optimum β ο =0.11, providing, as a design goal, a voltage gain of V a =1.08 MV at 7 W power dissipation. The inner conductor is equipped with a donut drift tube. The cavity has a double wall mechanical structure with liquid Helium inside. Two prototype cavities for the ISAC-II high beta section were developed at TRIUMF and produced by a Canadian company, PAVAC Industries of Richmond, B.C. The prototypes are equipped with a mechanical dissipator to damp detuning environmental mechanical vibrations. An inductive coupler, developed at TRIUMF, provides low power dissipations to the liquid helium system. Superconducting RF tests of both cavity prototypes show that we have achieved the required frequency and exceeded the design goal parameters. Response of the cavity to liquid helium pressure fluctuations, Lorenz force detuning and microphonic sensitivity with and without the damper was tested. RF design, prototype production details and cavity test results will be presented and discussed. . ISAC-II high beta cavity design.

Technical developments on reduced-β superconducting cavities at CERN

Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366), 1999

Several authors proposed the construction of superconducting proton linacs using the LEP2 cavities once LEP will be decommissioned. However only a fraction (about half) of these cavities can be used as they are for the high-energy part (-~1) of such a linac, the low energy part requiring the development of accelerating structures optimized for lower values of the particle velocity. At CERN an R&D programme on reduced--single-cell cavities started in 1996 in order to study and explore the limits of the technology successfully used for the production of LEP2 cavities (copper cavities niobiumplated using the magnetron sputtering technique). Four different geometries were extensively investigated, each representing part of a multicell structure optimized for particles having -=0.48, -=0.625, -=0.66 and -=0.8 respectively. The results were encouraging for the last two types and therefore a new phase of R&D aimed at the production of multicell cavities for -=0.66 and -=0.8 was started. The goal is to demonstrate simultaneously the feasibility of such cavities and the possibility of producing them by low-cost modification of LEP cavities. In the paper, after a brief review of the results obtained on the single-cell cavities, we shall present in more detail the procedure for the transformation of the LEP cavities, which should allow a realistic estimate of the costs of such operation.

Advances in Nb3Sn superconducting radiofrequency cavities towards first practical accelerator applications

Superconductor Science and Technology, 2021

Nb3Sn is a promising next-generation material for superconducting radiofrequency cavities, with significant potential for both large scale and compact accelerator applications. However, so far, Nb3Sn cavities have been limited to continuous wave accelerating fields <18 MV m−1. In this paper, new results are presented with significantly higher fields, as high as 24 MV m−1 in single cell cavities. Results are also presented from the first ever Nb3Sn-coated 1.3 GHz 9-cell cavity, a full-scale demonstration on the cavity type used in production for the European XFEL and LCLS-II. Results are presented together with heat dissipation curves to emphasize the potential for industrial accelerator applications using cryocooler-based cooling systems. The cavities studied have an atypical shiny visual appearance, and microscopy studies of witness samples reveal significantly reduced surface roughness and smaller film thickness compared to typical Nb3Sn films for superconducting cavities. Poss...

A New Superconducting Linac for the Nuclotron–NICA Facility: Progress Report

Physics of Particles and Nuclei Letters, 2018

The project for a new injector linac for the Nuclotron-NICA accelerator tandem has been under development since 2015. The linac will accelerate protons and light ions to energies of 25 MeV and 7.5 MeV/nucleon, respectively. To fulfill the project, technology for fabricating superconducting RF cavities needs to be developed. The current status of the project, including the linac design, the required parameters of RF cavities, and our simulations of beam dynamics, is presented. Technological restrictions on the RF cavity parameters are discussed.

New Directions in Superconducting Radio Frequency Cavities for Accelerators

IEEE Transactions on Appiled Superconductivity, 2005

At Michigan State University, several avenues are being explored to improve and advance the use of SRF. Modifications to the shape and heat transfer characteristics of existing designs are being studied to increase the accelerating gradient and reduce the cryogenic losses. Also, a new type of cavity based on the TM01p waveguide mode is presented that has the potential to improve high current linear accelerators or the use of advanced materials such as Nb 3 Sn or high-T c superconductors.

The LHC superconducting cavities

Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366), 1999

The LHC RF system, which must handle high intensity (0.5 A d.c.) beams, makes use of superconducting singlecell cavities, best suited to minimizing the effects of periodic transient beam loading. There will be eight cavities per beam, each capable of delivering 2 MV (5 MV/m accelerating field) at 400 MHz. The cavities themselves are now being manufactured by industry, using niobium-on-copper technology which gives full satisfaction at LEP. A cavity unit includes a helium tank (4.5 K operating temperature) built around a cavity cell, RF and HOM couplers and a mechanical tuner, all housed in a modular cryostat. Four-unit modules are ultimately foreseen for the LHC (two per beam), while at present a prototype version with two complete units is being extensively tested. In addition to a detailed description of the cavity and its ancillary equipment, the first test results of the prototype will be reported.

Designing Superconducting Cavities for Accelerators

Accelerator Physics, Technology and Applications - Selected Lectures of the OCPA International Accelerator School 2002, 2004

Rapid advances in the performance of superconducting cavities have made RF superconductivity a key technology for accelerators that fulfil a variety of physics needs: high energy particle physics, nuclear physics, neutron spallation sources, and free electron lasers. New applications are forthcoming for frontier high energy physics accelerators, radioactive beams for nuclear astrophysics, next generation light sources, intense proton accelerators for neutron, neutrino and muon sources.