Effects of surface damage on rf cavity operation

Ion Solid Interaction And Surface Modification At RF Breakdown In High-Gradient Linacs

“…Our previous OOPIC simulations 1 showed that the copper surface can become very hot as a result of ion bombardment within a few nanoseconds in close vicinity to the plasma and can be melted. Therefore, a liquid Cu surface for MD simulation was prepared by heating a copper substrate to the melting temperature of 1310 K, equilibrating this configuration, and storing it as an input file for the sputtering yield calculations.…”

“…The ion energies were selected between 50 and 150 eV, corresponding to the sheath potential value obtained by our OOPIC simulation. Figure 1 shows the results of our MD simulations of self-sputtering of the copper rf-cavity surface by accelerated Cu+ ions, at ion energies varied between 50 and 150 eV and surface temperatures of 300-1310 K. The 1 To be published elsewhere ID 441 3 most important result is that the self-sputtering yield at 800 K for an ion energy of 100 eV was found to be approximately 2.5 and increases as the melting point of 1310 K is reached.…”

“…Energetic ion collisions with solid targets are an important area of research in basic science [1][2][3][4][5][6][7][8], as well as in numerous industrial applications [9][10][11][12][13][14][15][16][17][18][19]. Self-sputtering processes are also of fundamental interest in the development of high-gradient rf accelerators [1].…”

“…Self-sputtering processes are also of fundamental interest in the development of high-gradient rf accelerators [1]. The Neutrino Factory and Muon Collider Collaboration is looking at developing low-frequency structures for muon cooling [2][3][4][5][6], the International Linear Collider is optimizing the performance of 1.3 GHz superconducting rf structures aimed at the design of a 1 TeV superconducting electron/positron collider [7], and the High Gradient RF Collaboration is studying high-frequency (f >10 GHz) structures aimed at an electron-positron collider operating at energies higher than 1 TeV [8].…”

The Problem of RF Gradient Limits

“…An earlier paper has shown that all structures seem to break down at a fixed value of E local and any variation in the gradient limits must be due to the maximum enhancement factors in specific structures [14]. As the basic processes in all rf arcs follow similar mechanisms, and the primary difference between the particular structures is due to the energy of the arc.…”