Superconducting niobium sputter-coated copper cavity modules for the LEP energy upgrade

Benvenuti, C.; Bernard, P.; Bloess, D.; Cavallari, G.; Chiaveri, E.; Haebel, E.; Hilleret, N.; Tückmantel, Joachim; Weingarten, W.

doi:10.1109/pac.1991.164525

Cited by 13 publications

(9 citation statements)

References 5 publications

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“…It is also insensitive to magnetic flux trapping and thus allows the design of cryomodules without magnetic shields and provides much higher thermal stability against quenches. The pioneering niobium sputter-coating technique was invented at CERN for the accelerating cavities of LEP [28] and the sputtering technology that is needed for this type of geometry was developed at INFN [29]. The coating chamber is an ultra-high vacuum system, allowing base pressures to reach the low 10 −9 mbar range.…”

Section: Superconducting Quarter-wave Resonatorsmentioning

confidence: 99%

Post-accelerated beams at ISOLDE

Kadi

Blumenfeld

Delsolaro

et al. 2017

J. Phys. G: Nucl. Part. Phys.

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This paper presents an overview of the REX-ISOLDE post-accelerator and a detailed description of the high intensity and energy ISOLDE (HIE-ISOLDE) energy upgrade. The status of the HIE-ISOLDE post-accelerator and its performance, including time structure, beam spot size, beam purity, etc. is presented. The high-energy beam transfer line is also described in detail and an overview of present and future instrumentation and plans for further developments is given. Finally, the hardware and beam commissioning is presented.

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Section: Superconducting Quarter-wave Resonatorsmentioning

confidence: 99%

Post-accelerated beams at ISOLDE

Kadi

Blumenfeld

Delsolaro

et al. 2017

J. Phys. G: Nucl. Part. Phys.

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“…Oxygen-free high-conductivity (OFHC) copper is one of the metals which has a higher thermal conductivity than high-purity Nb below 10 K and it has been used as a substrate for the deposition of Nb thin-films on the inner surface of cavities for particle accelerators [15]. The higher thermal conductivity allows for a better thermal stabilization of the cavity, even when cooling with LHe, particularly against the presence of defects in the superconducting thin-film.…”

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confidence: 99%

Multi-metallic conduction cooled superconducting radio-frequency cavity with high thermal stability

Ciovati

Cheng

Pudasaini

et al. 2020

Supercond. Sci. Technol.

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Superconducting radio-frequency cavities are commonly used in modern particle accelerators for applied and fundamental research. Such cavities are typically made of high-purity, bulk Nb and are cooled by a liquid helium bath at a temperature of ∼ 2 K. The size, cost and complexity of operating a particle accelerator with a liquid helium refrigerator makes the current cavity technology not favorable for use in industrial-type accelerators. We developed a multi-metallic 1.495 GHz elliptical cavity conductively cooled by a cryocooler. The cavity has a ∼ 2 µm thick layer of Nb3Sn on the inner surface, exposed to the rf field, deposited on a ∼ 3 mm thick bulk Nb shell and a bulk Cu shell, of thickness 5 mm deposited on the outer surface by electroplating. A bolt-on Cu plate 1.27 cm thick was used to thermally connect the cavity equator to the second stage of a Gifford-McMahon cryocooler with a nominal capacity of 2 W at 4.2 K. The cavity was tested initially in liquid helium at 4.3 K and reached a peak surface magnetic field of ∼ 36 mT with a quality factor of 2 × 10 9 . The cavity cooled by the crycooler achieved a peak surface magnetic field of ∼ 29 mT, equivalent to an accelerating gradient of 6.5 MV/m, and it was able to operate in continuous-wave with as high as 5 W dissipation in the cavity for 1 h without any thermal breakdown. This result represents a paradigm shift in the technology of superconducting accelerator cavities.

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“…Pioneering work [15,16] on Cu cavities coated with Nb thin film has been done at the European Organization for Nuclear Research, known as CERN. By 1998, 272 copper 352 MHz cavities, Nb thin film coated via magnetron sputtering, were deployed for the Large Electron-Positron Collider (LEP-II) project.…”

Section: Motivation For Superconducting Thin Film Developmentmentioning

confidence: 99%

Energetic condensation growth of Nb thin films

Krishnan

Valderrama

James

et al. 2012

Phys. Rev. ST Accel. Beams

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This paper describes energetic condensation growth of Nb films using a cathodic arc plasma, whose 60-120 eV ions penetrate a few monolayers into the substrate and enable sufficient surface mobility to ensure that the lowest energy state (crystalline structure with minimal defects) is accessible to the film. Heteroepitaxial films of Nb were grown on a-plane sapphire and MgO crystals with good superconducting properties and crystal size (10 mm Â 20 mm) limited only by substrate size. The substrates were heated to temperatures of up to 700 C and coated at 125 C, 300 C, 500 C, and 700 C. Film thickness was varied from $0:25 m to >3 m. Residual resistivity ratio (hRRRi) values (up to a record hRRRi ¼ 587 on MgO and hRRRi ¼ 328 on a-sapphire) depend strongly on substrate annealing and deposition temperatures. X-ray diffraction spectra and pole figures reveal that RRR increases as the crystal structure of the Nb film becomes more ordered, consistent with fewer defects and, hence, longer electron mean-free path. A transition from Nb(110) to Nb(100) orientation on the MgO(100) lattice occurs at higher temperatures. This transition is discussed in light of substrate heating and energetic condensation physics. Electron backscattered diffraction and scanning electron microscope images complement the XRD data.

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Superconducting niobium sputter-coated copper cavity modules for the LEP energy upgrade

Cited by 13 publications

References 5 publications

Post-accelerated beams at ISOLDE

Post-accelerated beams at ISOLDE

Multi-metallic conduction cooled superconducting radio-frequency cavity with high thermal stability

Energetic condensation growth of Nb thin films

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