Magnetic trapping of ultracold neutrons

Three-dimensional magnetic confinement of neutrons is reported. Neutrons are loaded into an Ioffe-type superconducting magnetic trap through inelastic scattering of cold neutrons with 4He. Scattered neutrons with sufficiently low energy and in the appropriate spin state are confined by the magnetic field until they decay. The electron resulting from neutron decay produces scintillations in the liquid helium bath that results in a pulse of extreme ultraviolet light. This light is frequency downconverted to the visible and detected. Results are presented in which 500 +/- 155 neutrons are magnetically trapped in each loading cycle, consistent with theoretical predictions. The lifetime of the observed signal, 660 s +290/-170 s, is consistent with the neutron beta-decay lifetime.Comment: 17 pages, 18 figures, accepted for publication in Physical Review

Detecting ionizing radiation in liquid helium using wavelength shifting light collection

Detectors for counting low energy less than 1 MeV ionizing events in liquid helium are developed and characterized. These devices employ wavelength shifting fluors to convert extreme ultraviolet EUV helium scintillation light to the visible, allowing transport of signal light to room temperature. Three technological approaches are developed and tested wavelength shifting fiber, composite acrylic tube, and diffuse reflecting tube of expanded teflon. The tube based detectors have been used to detect magnetically trapped neutrons. All of the technological approaches have utility in other experiments, such as a more sensitive measurement of the neutron electric dipole moment and the monitoring of the low energy solar neutrino flu

Time dependence of liquid helium fluorescence

The time dependence of extreme ultraviolet EUV fluorescence following an ionizing radiation event in liquid helium is observed and studied in the temperature range from 250 mK to 1.8 K. The fluorescence exhibits significant structure including a short 10 ns strong initial pulse followed by single photons whose emission rate decays exponentially with a 1.6 mu s time constant. At an even longer time scale, the emission rate varies as 1 time inversely proportional to the time after the initial pulse . The intensity of the 1 time component from beta particles is significantly weaker than those from alpha particles or neutron capture on 3He. It is also found that for alpha particles, the intensity of this component depends on the temperature of the superfluid helium. Proposed models describing the observed fluorescence are discusse

'What's on your mind?' Writing on Facebook as a tool for self-formation

In the context of modern western psychologised, techno-social hybrid realities, where individuals are incited constantly to work on themselves and perform their self-development in public, the use of online social networking sites (SNSs) can be conceptualised as what Foucault has described as a ‘technique of self’. This article explores examples of status updates on Facebook to reveal that writing on Facebook is a tool for self-formation with historical roots. Exploring examples of self-writing from the past, and considering some of the continuities and discontinuities between these age-old practices and their modern translations, provides a non-technologically deterministic and historically aware way of thinking about the use of new media technologies in modern societies that understands them to be more than mere tools for communication