TY - JOUR

T1 - High-gradient behavior of a dipole-mode rf structure

AU - Woolley, B.

AU - Burt, G.

AU - Dexter, A.C.

AU - Peacock, R.

AU - Millar, W.L.

AU - Catalan Lasheras, N.

AU - Degiovanni, A.

AU - Grudiev, A.

AU - McMonagle, G.

AU - Syratchev, I.

AU - Wuensch, W.

AU - Rodriguez Castro, E.

AU - Giner Navarro, J.

PY - 2020/12/17

Y1 - 2020/12/17

N2 - A normal-conducting, X-band traveling wave structure operating in the dipole mode has been systematically high-gradient tested to gain insight into the maximum possible gradients in these types of structure. Measured structure conditioning, breakdown behavior, and achieved surface fields are reported as well as a postmortem analysis of the breakdown position and a scanning electron microscope analysis of the high-field surfaces. The results of these measurements are then compared to high-gradient results from monopole-mode cavities. Scaled to a breakdown rate of 10-6, the cavities were found to operate at a peak electric field of 154 MV/m and a peak modified Poynting vector Sc of 5.48 MW/mm2. The study provides important input for the further development of dipole-mode cavities for use in the Compact Linear Collider as a crab cavity and dipole-mode cavities for use in x-ray free-electron lasers as well as for studies of the fundamental processes in vacuum arcs. Of particular relevance are the unique field patterns in dipole cavities compared to monopole cavities, where the electric and magnetic fields peak in orthogonal planes, which allow the separation of the role of electric and magnetic fields in breakdown via postmortem damage observation. The azimuthal variation of breakdown crater density is measured and is fitted to sinusoidal functions. The best fit is a power law fit of exponent 6. This is significant, as it shows how breakdown probability varies over a surface area with a varying electric field after conditioning to a given peak field.

AB - A normal-conducting, X-band traveling wave structure operating in the dipole mode has been systematically high-gradient tested to gain insight into the maximum possible gradients in these types of structure. Measured structure conditioning, breakdown behavior, and achieved surface fields are reported as well as a postmortem analysis of the breakdown position and a scanning electron microscope analysis of the high-field surfaces. The results of these measurements are then compared to high-gradient results from monopole-mode cavities. Scaled to a breakdown rate of 10-6, the cavities were found to operate at a peak electric field of 154 MV/m and a peak modified Poynting vector Sc of 5.48 MW/mm2. The study provides important input for the further development of dipole-mode cavities for use in the Compact Linear Collider as a crab cavity and dipole-mode cavities for use in x-ray free-electron lasers as well as for studies of the fundamental processes in vacuum arcs. Of particular relevance are the unique field patterns in dipole cavities compared to monopole cavities, where the electric and magnetic fields peak in orthogonal planes, which allow the separation of the role of electric and magnetic fields in breakdown via postmortem damage observation. The azimuthal variation of breakdown crater density is measured and is fitted to sinusoidal functions. The best fit is a power law fit of exponent 6. This is significant, as it shows how breakdown probability varies over a surface area with a varying electric field after conditioning to a given peak field.

U2 - 10.1103/PhysRevAccelBeams.23.122002

DO - 10.1103/PhysRevAccelBeams.23.122002

M3 - Journal article

VL - 23

JO - Physical Review Accelerators and Beams

JF - Physical Review Accelerators and Beams

SN - 2469-9888

IS - 12

M1 - 122002

ER -