<i>RF Superconductivity for Accelerators</i>

Padamsee, H.; Knobloch, Jens; Hays, T.; Wilson, Perry B.

doi:10.1063/1.882759

Cited by 509 publications

(776 citation statements)

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“…Both R 0 fl and R 1 fl were observed to display a steep minimum when the electron mean free path l approximately matches the BCS coherence length, ξ 0 ≅ 33 nm. This result casts some doubt on the validity of the commonly accepted explanation [5,6], in particular as an independent measurement of H c2 [7] was in conflict with earlier measurements used in the argumentation developed in Reference [6]. It was instead proposed in Reference [1] that pinning should provide the dominant contribution to R fl .…”

Section: Introductioncontrasting

confidence: 44%

“…As most models of fluxon dynamics [3,4] predict R fl ≅ R n H ext / H c2 , R n being the value of the surface resistance in the normal conducting state and H c2 the upper critical field, this difference between films and bulk has been blamed [5,6] on a similar difference between the values taken by H c2 . In Reference [1] R fl was measured for a large variety of films spanning a wide range of electron mean free paths and the evolution of R 0 fl anf R 1 fl was tracked for the first time from the dirty limit (films containing more than 10 atomic percent of neon) to the clean limit (deep-drawn bulk niobium subsequently annealed at 1100°C).…”

Section: Introductionmentioning

confidence: 99%

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Fluxon pinning in niobium films

Benvenuti

Calatroni

Darriulat

et al. 2001

Physica C: Superconductivity

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Section: Introductioncontrasting

confidence: 44%

Section: Introductionmentioning

confidence: 99%

Fluxon pinning in niobium films

Benvenuti

Calatroni

Darriulat

et al. 2001

Physica C: Superconductivity

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“…By applying this technique it has been possible to raise the threshold for field emission in multicell cavities from about 10 MV͞m to more than 20 MV͞m in the past few years. The topics of thermal instability and field emission are discussed at much greater detail in the book by Padamsee, Knobloch, and Hays [16].…”

Section: Thermal Instability and Field Emissionmentioning

confidence: 99%

Superconducting TESLA cavities

Aune¹,

Bandelmann²,

Bloess³

et al. 2000

Phys. Rev. ST Accel. Beams

351

266

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The conceptional design of the proposed linear electron-positron collider TESLA is based on 9-cell 1.3 GHz superconducting niobium cavities with an accelerating gradient of E acc $ 25 MV͞m at a quality factor Q 0 $ 5 3 10 9 . The design goal for the cavities of the TESLA Test Facility (TTF) linac was set to the more moderate value of E acc $ 15 MV͞m. In a first series of 27 industrially produced TTF cavities the average gradient at Q 0 5 3 10 9 was measured to be 20.1 6 6.2 MV͞m, excluding a few cavities suffering from serious fabrication or material defects. In the second production of 24 TTF cavities, additional quality control measures were introduced, in particular, an eddy-current scan to eliminate niobium sheets with foreign material inclusions and stringent prescriptions for carrying out the electronbeam welds. The average gradient of these cavities at Q 0 5 3 10 9 amounts to 25.0 6 3.2 MV͞m with the exception of one cavity suffering from a weld defect. Hence only a moderate improvement in production and preparation techniques will be needed to meet the ambitious TESLA goal with an adequate safety margin. In this paper we present a detailed description of the design, fabrication, and preparation of the TESLA Test Facility cavities and their associated components and report on cavity performance in test cryostats and with electron beam in the TTF linac. The ongoing research and development towards higher gradients is briefly addressed.

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“…Next we present hRRRi and T c measurements in Nb thin films that were grown on a-sapphire and MgO crystal substrates. The hRRRi is here defined [1] as the ratio of resistivity at 300 K to that at 10 K, averaged across the film thickness. This bulk averaged hRRRi is different from the local RRR (at any depth in the film) because our measurement averages the RRR across the film.…”

Section: Introductionmentioning

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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RF Superconductivity for Accelerators

Cited by 509 publications

References 0 publications

Fluxon pinning in niobium films

Fluxon pinning in niobium films

Superconducting TESLA cavities

Energetic condensation growth of Nb thin films

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