Experimental Studies of Light Emission Phenomena in Superconducting RF Cavitites Page: 2 of 103

                                
shaped closed, 2) irregular-shaped closed, and 3) open." We reproduce in Fig. 1 the
example of 1) as shown in Fig. 2a of Ref. [1]. As discussed in Sec. 5.1, this is a track
representing a ~16 ms time exposure of a small luminous object moving about in the
vacuum space of the cavity. We shall use the acronym MLO to refer to these mobile
luminous objects.
Beamtube-spool
Far Iris        Piece Flanges
SPL                 845A
Figure 1. Video frame (field) of a closed filament in the single-cell data. (Orbit No. 4 of Table I.
For reference purposes, the eccentricity, 8, of the ellipse in this figure is 0.9.) A glowing point of
light or SPL (see text) is indicated. The arcs of light reflected from the flange joining the beamtube
to the spool piece are also indicated.
These MLO's were completely unexpected. In order to study further this most intriguing
phenomenon, the ALE (Anomalous Light Experiment) Collaboration was formed with
membership from SLAC, TJNAF, and 2G Enterprises. The goals of this collaboration
are: 1) to determine the conditions that are conducive to the occurrence of cavity lights,
and 2) to understand the underlying physics.
Subsequent to the initial two runs, a number of additional experimental runs have been
undertaken. This present paper includes additional analysis of the data from the initial
two runs as well a discussion of data obtained in seven subsequent experimental runs.
Table I gives a brief overview of these runs. Through a more detailed analysis of the data
from these runs, we found that there are several light emission phenomena that appear to
have a physics relationship to the MLO's. Furthermore, in Run 7, as described in Sec. 7,
MLO's were observed behaving in ways that were qualitatively different from anything
seen in the earlier runs. This observation introduces a significant level of additional
complexity into the cavity lights phenomena. In addition to the data analysis, some
remarks about theoretical possibilities and plans for future work are also included.
For convenient reference, we list in Table II various luminous phenomena seen in these
runs, including brief descriptions of their salient characteristics. As described below,
there were a number of occasions in which two or more of these phenomena were present
in the cavity at the same time.