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For the purpose of future visualization of the flow field in superfluid helium-4, clusters of the triplet state excimer 4He2* are generated along the micro-scale recoil tracks of the neutron-absorption reaction n + 3He → 3T + p. This reaction is induced by neutron irradiation of the 3He fraction contained in natural isotopic abundance liquid helium with neutron beams either from the Japan Proton Accelerator Research Complex, Materials and Life Science Experimental Facility (JPARC)/Materials and Life Science Experimental Facility or from the Kyoto University Institute for Integrated Radiation and Nuclear Science. These 4He2* clusters are expected to be ideal tracers of the normal-fluid component in superfluid helium with several advantageous properties. Evidence of the excimer generation is inferred by detection of laser induced fluorescence emitted from the 4He2* clusters excited by a purpose-built short pulse gain-switched titanium:sapphire (Ti:sa) laser operating at a wavelength of 905 nm. The setup and performance characteristics of the laser system including the Ti:sa and two continuous wave re-pumping lasers are described. Detection at the fluorescence wavelength of 640 nm is performed by using optical bandpass filtered photomultiplier tubes (PMT). Electrical noise in the PMT acquisition traces could successfully be suppressed by post-processing with a simple algorithm. Despite other laser-related backgrounds, the excimer was clearly identified by its fluorescence decay characteristics. Production of the excimer was found to be proportional to the neutron flux, adjusted via insertion of different collimators into the neutron beam. These observations suggest that the apparatus we constructed does function in the expected manner and, therefore, has the potential for groundbreaking turbulence research with superfluid helium. [ABSTRACT FROM AUTHOR]

An inductively heated hot cavity catcher has been constructed for the production of low-energy ion beams of exotic, neutron-deficient 107Ag21+ isotopes. A proof-of-principle experiment has been realized by implanting primary Ag ions from a heavy-ion cyclotron into a graphite catcher. A variable-thickness nickel foil was used to degrade the energy of the primary beam in order to mimic the implantation depth expected from the heavy-ion fusion-evaporation recoils of N = Z94 Ag. Following implantation, the silver atoms diffused out of the graphite and effused into the catcher cavity and transfer tube, where they were resonantly laser ionized using a three-step excitation and ionization scheme. Following mass separation, the ions were identified by scanning the frequency of the first resonant excitation step while recording the ion count rate. Ion release time profiles were measured for different implantation depths and cavity temperatures with the mean delay time varying from 10 to 600 ms. In addition, the diffusion coefficients for silver in graphite were measured for temperatures of 1470 K, 1630 K, and 1720 K, from which an activation energy of 3.2 ± 0 3 eV could be determined. [ABSTRACT FROM AUTHOR]

The interest to produce negative osmium ions is manifold in the realm of high-accuracy ion trap experiments: high-resolution nearly Doppler-free laser spectroscopy, antihydrogen formation in its ground state, and contributions to neutrino mass spectrometry. Production of these ions is generally accomplished by sputtering an Os sample with Cs+ ions at tens of keV. Though this is a well-established method commonly used at accelerators, these kind of sources are quite demanding and tricky to operate. Therefore, the development of a more straightforward and cost effective production scheme will be of benefit for ion trap and other experiments. Such a scheme makes use of desorption and ionization with pulsed lasers and identification of the ions by time-of-flight mass spectrometry. First investigations of negative osmium ion production using a pulsed laser for desorption and ionization and a commercial matrix-assisted laser desorption/ionization time-of-flight system for identification has demonstrated the suitability of this technique. More than 103 negative osmium ions per shot were registered after bombarding pure osmium powder with a 5 ns pulse width Nd:yttrium aluminum garnet laser. The limitation in the ion number was imposed by the detection limit of the microchannel plate detector. [ABSTRACT FROM AUTHOR]