New results with superconducting 500 MHz cavities at CERN

doi:10.1016/0167-5087(83)91241-3

Nuclear Instruments and Methods in Physics Research

Volume 206, Issues 1–2, 15 February 1983, Pages 47-56

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Abstract

New experimental results with three 500 MHz single cell Nb cavities of “spherical” shape are described. At 4.2 K, acceleration fields up to 6.5 MV/m and Q_o values up to 3 × 10⁹ (1.7 × 10¹⁰ at 2.2 K) have been reached. Rf He ion sputtering was used and allowed to decrease the electron loading sufficiently so that the fields were always limited by a thermal instability driven by a small region of increased rf losses. A stepwise removal of different lossy regions by mechanical grinding and milling allowed field levels to be increased. It was found that the cavity performance depends strongly on the arrangement of the cavity and the vacuum system. After an accidental exposure to laboratory air no strong Q₀ degradation was observed and the initial field value could be restored after a short He ion sputtering.

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^∗: Scientific Associate from Cornell University, Ithaca, USA.

^∗∗: Scientific Associate from Bari University, Italy.

^∗∗∗: Scientific Associate from University of Wuppertal, W. Germany.

⁺: Scientific Associate from Stanford University, Palo Alto, USA.

⁺⁺: Fellow from University of Wuppertal, W. Germany.

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New results with superconducting 500 MHz cavities at CERN

Abstract

Nucl. Instr. and Meth.

Nucl. Instr. and Meth.

CERN/ISR-LEP/79-33