Superconducting cavities (original) (raw)

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.

High Power Coupler R&D for Superconducting CH-cavities

2019

The upcoming demands of the future research programs at GSI exceed the technical opportunities of the existing GSI UNIversal Linear ACcelerator (UNILAC). Besides, the existing machine will be exclusively used as an injector for FAIR (Facility for Antiproton and Ion Research) providing high power heavy ion beams at a low repetition rate for injection into a heavy ion synchrotron. A new dedicated superconducting (sc) continuous wave (cw) linac is crucial to keep the GSI research program competitive. The first part of the cwlinac, comprising a 217 MHz multi gap Crossbar-H-mode (CH) cavity surrounded by two sc solenoids inside a cryostat, already served as a prototype demonstrating reliable operability in a realistic accelerator environment. A sufficient high power RF-coupling concept is needed to feed this newly developed cw-RF cavity with up to 5 kW of RF-power in cw-mode. A high power coupler test stand was recently built to provide for a testing environment; further upgrade measures...

Conceptual design of the RF accelerating cavities for a superconducting cyclotron

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2006

A superconducting cyclotron accelerating ions up to 250 A MeV, for medical applications and radioactive ions production is being studied at Laboratori Nazionali del Sud in Catania. The radio frequency (RF) system, working in the fourth harmonic, is based on four normal conducting radio frequency cavities operating at 93 MHz. This paper describes an unusual multi-stem cavity design, performed with 3D electromagnetic codes. Our aim is to obtain a cavity, completely housed inside the cyclotron, with a voltage distribution ranging from 65 kV in the injection region to a peak value of 120 kV in the extraction region, and having a low power consumption.

The science and technology of superconducting cavities for accelerators

Superconductor Science and Technology, 2001

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 and muon sources. There are now nearly one kilometre of superconducting cavities installed in accelerators around the world, providing more than 5 GV of acceleration. The most recent installation of 20 m for a free-electron laser realized an average gradient a factor of four higher than existing applications. Improved understanding of the physics of RF superconductivity, together with advances in technology, are responsible for the spectacular increases in performance. RF superconductivity is a mature science going well beyond technological know-how and trial-and-error approaches to genuine understanding of the underlying physics. Research continues to push performance levels towards the theoretical limit, which is another factor of two higher than the levels yet achieved.

Reduction of field emission in superconducting cavities with high power pulsed RF

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1994

A systematic study is presented of the effects of pulsed high power RF processing (HPP) as a method of reducing field emission (FE) in superconducting radio frequency (SRF) cavities to reach higher accelerating gradients for future particle accelerators. The processing apparatus was built to provide up to 150 kW peak RF power to 3 GHz cavities, for pulse lengths from 200 ws to 1 ms. Single-cell and nine-cell cavities were tested extensively. The thermal conductivity of the niobium for these cavities was made as high as possible to ensure stability against thermal breakdown of superconductivity. HPP proves to be a highly successful method of reducing FE loading in nine-cell SRF cavities. Attainable continuous wave (CW) fields increase by as much as 80% from their pre-HPP limits. The CW accelerating field achieved with nine-cell cavities improved from 8-15 MV/m. with HPP to 14-20 MV/m. The benefits are stable with subsequent exposure to dust-free air. More importantly, HPP also proves effective against new field emission subsequently introduced by cold and warm vacuum "accidents" which admitted "dirty" air into the cavities. Clear correlations are obtained linking FE reduction with the maximum surface electric field attained during processing. In single cells the maximums reached were Epeak = 72 MV/m. and Hpeak = 1660 Oe. Thermal breakdown, initiated by accompanying high surface magnetic fields is the dominant limitation on the attainable fields for pulsed processing, as well as for final CW and long pulse operation. To prove that the surface magnetic field rather than the surface electric fields is the limitation to HPP effectiveness, a special two-cell cavity with a reduced magnetic to electric field ratio is successfully tested. During HPP, pulsed fields reach Epeak = 113 MV/m. (Hpeak = 1600 Oe) and subsequent CW low power measurement reached Epeak = 100 MV/m, the highest CW field ever measured in a superconducting accelerator cavity .

Design study on a superconducting multicell RF accelerating cavity for use in a linear collider

IEEE Transactions on Nuclear Science, 1998

A nine-cell superconducting RF accelerating cavity is designed for the TeV electron linear accelerator collider in the next century. The ratio of the maximum surface electric field to the accelerating gradient, E pk =E acc , is reduced to 2.024 and the cell-to-cell coupling remains as high as 1.95%. The distribution of the higher-order mode passbands is reasonable. There is no overlap between these bands, therefore no trapped modes. The circle-straight/line-ellipse-type structure provides good mechanical strength in the accelerating cavity. According to the present state of the art of surface processing techniques of Niobium cavities, it is possible to reach an accelerating gradient of 25-30 MV/m with beam load.

400 mA Beam Store with Superconducting RF Cavities at PLS-II

2015

Three superconducting RF cavities were commissioned with electron beam in way of one by one during the last 3 years, and now PLS-II is in user service on the way of beam current to 400mA, the target of PLS-II. The cavities and cryomodules were prepared with SRF standard technology and procedures, then vertical test, windows conditioning, cryogenic test in each cryomodule, horizontal power test, conditioning, and commissioning without and with beam at PLS-II tunnel by collaboration with industries. All the cavities showed stable performances as good as not-observing any RF instability from cavities, couplers and windows up to 400 mA beam store, but observing several cavity quenches and minor vacuum bursts by abrupt power with control and human errors. The initial beam current for user run were recorded as 150 mA with one cavity, 280 mA with two cavities and 320 mA with three cavities. The 400 mA beam was also achieved with two cavities by decay mode and also with three cavities by top-up mode. The stabilities of RF amplitude and phase are good enough not to induce beam instabilities.

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.