SLAC-PUB-13664 Experimental studies of light emission phenomena in superconducting RF cavities + P.L. Anthony a , J.R. Delayen b , D. Fryberger a, ∗ , W.S. Goree c,  , J. Mammosser b,d , Z. M. Szalata a , J.G. Weisend II a a SLAC National Accelerator Laboratory, Menlo Park, CA 94025 b Thomas Jefferson National Accelerator Facility (TJNAF), Newport, News, VA 23606 c 2G Enterprises, Pacific Grove, CA 93950 d Present Affiliation: The SNS Facility, Oak Ridge National Laboratory, Oak Ridge, TN Abstract Experimental studies of light emission phenomena in superconducting RF cavities, which we categorize under the general heading of cavity lights, are described. The cavity lights data, which were obtained using a small CCD video camera, were collected in a series of nine experimental runs ranging from ~½ to ~2 h in duration. The video data were recorded on a standard VHS tape. As the runs progressed, additional instrumentation was added. For the last three runs a LabVIEW controlled data acquisition system was included. These runs furnish evidence for several, possibly related, light emission phenomena. The most intriguing of these is what appear to be small luminous objects ≤ 1.5 mm in size, freely moving about in the vacuum space, generally without wall contact, as verified by reflections of the tracks in the cavity walls. In addition, on a number of occasions, these objects were observed to bounce off of the cavity walls. The wall- bounce aspect of most of these events was clearly confirmed by pre-bounce and post-bounce reflections concurrent with the tracks. In one of the later runs, a mode of behavior was observed that was qualitatively different from anything observed in the earlier runs. Perhaps the most perplexing aspect of this new mode was the observation of as many as seven luminous objects arrayed in what might be described as a macromolecular formation, coherently moving about in the interior of the cavity for extended periods of time, evidently without any wall contact. It is suggested that these mobile luminous objects are without explanation within the realm of established physics. Some remarks about more exotic theoretical possibilities are made, and future plans are discussed. PACS: 46.90 + s; 52.80 Mg Keywords: Field emission; cavity lights 1. Introduction In 1999, Delayen and Mammosser [1] reported observations of glowing filaments of light suspended in the vacuum space of superconducting niobium RF cavities. These observations were obtained using a small CCD video camera 1 looking along the axis into the cavity. The original purpose of the experiment was to study field emission phenomena. Two different experimental setups were used, one with a single-cell cavity and one with a five-cell cavity. Similar results were obtained in both setups. It was reported that: "Three general classes of glowing filaments were observed: 1) regular- + Supported by the Department of Energy Contracts DE-AC02-76SF-00515 and DE-AC05-84ER40150. ∗ Corresponding author. E-mail address: fryberger@slac.stanford.edu (D. Fryberger).Tel.: + 1-650-926-2768.  Deceased 1 Monochrome Micro Camera, Model H53004, Edmund Scientific Optics and Optical Catalogue N991A, 1999, p. 177. July 2009 Submitted to Nuclear Instrumentation and Methods (NIM)