Upper limits on emission of neutrons from Ti in pressurized D2 gas cells: A test of evidence for "cold fusion"

We have used a low background detector with high efficiency for detection of bursts to search for emission of neutrons from Ti alloy in pressurized D2 gas cells (cooled to 77 K in liquid nitrogen). Each cell contained between 16 and 67 g of Ti alloy chips and was prepared by methods identical to those used in a recent Los Alamos-Brigham Young University collaboration of Menlove et al. Three to four cells were used in each experimental run, with a total counting time of 103 h, leading to an estimate (based on the early reports of Menlove et al.) of at least four bursts and as many as 12 bursts expected in our experiment. In a later report the burst rate of Menlove et al. is greatly reduced leading to only one or so burst(s) expected in our experiment. The data were analyzed in two modes. In the first mode (singles mode) all detectors were used to search for neutron bursts with an efficiency of 28% for neutron detection and a background of 100 counts per hour (cph). In the second mode (coincidence mode) the neutron time of flight was measured in a search for random emission with an efficiency of 2% and a background of 2 cph. No statistically significant deviations from the background were observed for correlated neutrons emitted in bursts or for neutrons emitted randomly. All events are shown (with 90% confidence) to be consistent with background. For bursts of neutrons we deduce (with 90% confidence) an upper limit on the bursts' size of 50 neutrons. Our upper limit on the random emission of neutrons, 0.008 n/sec (90% confidence), is a factor of 6 to 25 smaller than the range of rates for random emission above background reported by the Los Alamos-Brigham Young University collaboration.