Author: Gonnella, D.
Paper Title Page
WEPPC070 Automated Cavity Test Suite for Cornell's ERL Program 2372
  • D. Gonnella, M. Liepe, N.R.A. Valles
    CLASSE, Ithaca, New York, USA
  As of 2011, fabrication and testing of main linac 7-cell cavities has begun for Cornell's Energy Recovery Linac prototype project. To standardize the testing process, minimize errors and allow for quick and precise measurements of these cavities, a suite of MatLab programs has been written to automate cavity tests. The programs allow measuring the quality factor versus temperature, and quality factor vs. accelerating gradient, and allow extracting material properties such as RRR and residual resistance. They are compatible with EPICS input/output controllers or standalone computers. Finally, the program can measure continuous Q vs E curves from a single high field decay curve, and can perform temperature mapping and quench localization from oscillating superleak transducer data.  
WEPPC071 Quench Studies of a Superconducting RF Cavity 2375
  • D. Gonnella, M. Liepe, S. Posen
    CLASSE, Ithaca, New York, USA
  In tests of superconducting RF cavities, it is important to understand the cause of high field quenches. Quenches at high field above 25 MV/m are a limiting factor in the performance of high accelerating field cavities but their causes are currently not well understood. An ILC shaped single cell cavity with quench field near 40 MV/m was tested with temperature mapping to determine the cause of its hard quench. Prior to quench, heating on the order of 25 mK was concentrated in two hot spots. After a quench, these two hot spots remain and a new one appears with much higher heating (about 40 mK). The quench location was found by the temperature mapping system to be centered at the new hot spot, not at the two hot spot locations before that dominated quench. By studying the quench location and heating on the surface of the cavity, some hints were gained as to the cause of this quench.  
WEPPC079 Residual Resistance Studies at Cornell 2393
  • S. Posen, D. Gonnella, G.H. Hoffstaetter, M. Liepe
    CLASSE, Ithaca, New York, USA
  • J. Oh
    Cornell University, Ithaca, New York, USA
  The Cornell single-cell temperature mapping system has been adapted for use with ILC and Cornell ERL-shape superconducting accelerator cavities. The system was optimized for low-noise, high-precision measurements with the goal of measuring resistances as low as 1 nohms. Using this system, a T-map of an ILC single cell was obtained at accelerating fields below the onset of Q-slope and at temperatures at which BCS resistance is small, producing a measurement of the distribution of residual resistance over the surface of the cavity. Standard procedures were used in preparing the cavity to avoid Q-disease and trapped flux caused by cooling the cavity through its transition in the presence of magnetic fields. Studying the T-map gives clues to the source of residual resistance, so that steps can be taken to reduce it, thereby lowering losses and increasing Q0. The temperature map noise-reduction studies as well as the residual resistance results are presented in this paper.