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1

Digitale Medien

Power and magnetic field-induced microwave absorption in Tl-based high Tc superconducting films (1991)

Portis, A. M. ; Cooke, D. W. ; Gray, E. R. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 58 (1991), S. 307-309

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The increase in the microwave surface resistance Rs of high Tc superconductors at elevated microwave power levels is reported for both oriented and unoriented Tl-based films as a function of rf magnetic field at 820 MHz and 18 GHz. The application of dc magnetic fields produces qualitatively similar increases in Rs and in the surface reactance Xs. The increase in Rs with dc field is shown to arise from simple decoupling of grains by intergranular magnetic flux. The increase in Rs with microwave power, on the other hand, is a consequence of hysteretic intergranular processes.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.104670

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2

Digitale Medien

Apparatus for measurement of surface resistance versus rf magnetic field of high-Tc superconductors (1990)

Delayen, J. R. ; Bohn, C. L. ; Roche, C. T.

[S.l.] : American Institute of Physics (AIP)

Review of Scientific Instruments 61 (1990), S. 2207-2210

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ISSN: 1089-7623

Quelle: AIP Digital Archive

Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik

Notizen: A coaxial niobium quarter-wave resonant cavity has been fabricated and used for measurement of the surface resistance of disk-shaped samples of high-Tc superconductors at 820 MHz and 4.2 K, and at surface rf magnetic fields ranging to 300 G. The cavity can accommodate samples as large as 36 mm in diameter. A measurement procedure has been developed with which rf surface resistances less than 20 μΩ can be resolved for a 24-mm-diam sample at 820 MHz. This cavity is useful in determining the suitability of high-Tc superconductors for high-power rf applications.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1141390

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3

Digitale Medien

Introduction to low-velocity superconducting accelerating structures and recent work at ASI and Caltech (invited) (1986)

Delayen, J. R.

[S.l.] : American Institute of Physics (AIP)

Review of Scientific Instruments 57 (1986), S. 766-769

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ISSN: 1089-7623

Quelle: AIP Digital Archive

Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik

Notizen: The characteristics and design parameters of low-velocity superconducting resonators for the acceleration of heavy ions are reviewed and discussed. Recent results obtained on lead-plated split-ring and half-wave resonators are also presented.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1138859

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4

Digitale Medien

Tests of a superconducting rf quadrupole device (1990)

Delayen, J. R. ; Shepard, K. W.

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 57 (1990), S. 514-516

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: High surface electric fields have been obtained in the first tests of a superconducting rf quadrupole device. The rf quadrupole fields were generated between niobium vanes 6.5 cm in length, with an edge radius of 2 mm, and with a beam aperture of 6 mm diameter. In tests at 4.2 K, the 64 MHz device operated cw at peak surface electric fields of 128 MV/m. Virtually no electron loading was observed at fields below 100 MV/m. It was possible to operate at surface fields of 210 MV/m in pulses of 1 ms duration using a 2.5 kW rf source. For the vane geometry tested, more than 10 square centimeters of surface support a field greater than 90% of the peak field. The present result indicates that electric fields greater than 100 MV/m can be obtained over an appreciable area, sufficient for some accelerator applications. It also shows that superconducting rf technology may provide an extended range of options for rf quadrupole design.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.103636

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5

Digitale Medien

rf properties of an oxide-superconductor half-wave resonant line (1988)

Delayen, J. R. ; Goretta, K. C. ; Poeppel, R. B. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 52 (1988), S. 930-932

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Cylindrical rods of YBa2Cu3O7−δ from 0.6 to 1.9 mm in diameter and up to 565 mm long have been used as the center conductor of a half-wave resonant coaxial line. The resonant line can be immersed in liquid nitrogen, which provides excellent cooling of the current-carrying superconducting surface, even in the presence of substantial rf losses. Such superconducting resonant lines have been operated at frequencies of a few hundred MHz and at rf surface magnetic fields up to 150 G at 77 K.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.99277

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6

Digitale Medien

Radio frequency surface resistance of large-area Bi-Sr-Ca-Cu-O thick films on Ag plates (1989)

Bohn, C. L. ; Delayen, J. R. ; Balachandran, U. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 55 (1989), S. 304-306

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Films nominally 80 μm thick of Bi-Sr-Ca-Cu-O on silver substrates with surface areas from 1.25 to 182 cm2 were fabricated using two different processing procedures. Their rf surface resistances were measured as functions of temperature in the frequency range 2.65–29.2 GHz at low rf field amplitudes using cylindrical resonant cavities. The critical temperatures of the films were in the range 81–83 K. At X-band frequencies, the surface resistances matched that of room-temperature copper. The results were comparable to recent data on small pellets of bulk Bi-Sr-Ca-Cu-O.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.102411

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7

Digitale Medien

Measurements of the surface resistance of high-T c superconductors at high RF fields (1990)

Delayen, J. R. ; Bohn, C. L. ; Roche, C. T.

Springer

Journal of superconductivity 3 (1990), S. 243-250

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ISSN: 1572-9605

Schlagwort(e): High-T c ; superconductors ; microwave ; accelerator

Quelle: Springer Online Journal Archives 1860-2000

Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik

Notizen: Abstract We report measurements of the r.f. surface resistance of a wide variety of high-T c superconductors in bulk form and as films on silver substrates. Several apparatuses have been constructed and used for measurements at frequencies from 0.15 to 40 GHz and r.f. surface magnetic fields as high as 640 G. In every case in which the field dependence of the surface resistance was measured, the surface resistance increased monotonically with field amplitude through a transition region characterized by a strong field dependence. It then saturated at high field at a value of a few percent of the normal-state surface resistance just aboveT c . In the presence of this field dependence, the frequency dependence of the surface resistance changed from quadratic to less than linear.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00625264

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