Experimental demonstration of particle acceleration with normal conducting accelerating structure at cryogenic temperature

TL;DR

This paper demonstrates that operating a normal conducting X-band linear accelerator at cryogenic temperatures significantly enhances its performance, including higher gradients and reduced breakdown rates, through experimental validation.

Contribution

It provides the first experimental evidence of high-gradient operation of a normal conducting accelerator at cryogenic temperature, showing substantial performance improvements.

Findings

Achieved electron beam acceleration up to 150 MV/m at 77 K.

Reduced breakdown rates by a factor of 100 at cryogenic temperature.

Confirmed increased quality factor and efficiency of the accelerator at low temperature.

Abstract

Reducing the operating temperature of normal conducting particle accelerators substantially increases their efficiency. Low-temperature operation increases the yield strength of the accelerator material and reduces surface resistance, hence a great reduction in cyclic fatigue could be achieved resulting in a large reduction in breakdown rates compared to room-temperature operation. Furthermore, temperature reduction increases the intrinsic quality factor of the accelerating cavities, and consequently, the shunt impedance leading to increased system efficiency and beam loading capabilities. In this paper, we present an experimental demonstration of the high-gradient operation of an X-band, 11.424 GHz, 20-cells linear accelerator (linac) operating at a liquid nitrogen temperature of 77 K. The tested linac was previously processed and tested at room temperature. We verified the enhanced accelerating parameters of the tested accelerator at cryogenic temperature using different measurements including electron beam acceleration up to a gradient of 150 MV/m, corresponding to a peak surface electric field of 375 MV/m. We also measured the breakdown rates in the tested structure showing a reduction of two orders of magnitude, x100, compared to their values at room temperature for the same accelerating gradient.