Time bunching of slow positrons for lifetime and time-of-flight measurements of ortho-positronium

Development of a high-efficiency pulsed slow positron beam for measurements with orthopositronium in vacuum

“…6d. The compression ratio is ≃ 100, which is a factor 5 better than the values previously obtained by Iijima et al [21], reporting a compression from 50 ns to 2.2 ns, and by Tashiro et al…”

“…For the bunch width of ∼ 2.3 ns and a repetition period of 1µs our pulsing efficiency is ≃ 31 %, which is also a factor 6 better than reported in [21].…”

“…However, instead of applying a sinusoidal-like RF field, a more suitable pulse shape of the electric field, with an approximate inverse parabolic function of time, is applied to a single gap for the positron velocity modulation [20]. This method has been further developed by Iijima et al [21] for material measurements in which the lifetime of orthopositronium atoms is close to its vacuum value of ≃ 142 ns. For these applications it is necessary to modify the originally proposed technique in order to generate higher intensity positron beams by accumulating positrons over a wider time interval, even though the bunch width becomes larger, but is still much less than the typical measured timing intervals of ≃ 100 ns.…”

“…For these applications it is necessary to modify the originally proposed technique in order to generate higher intensity positron beams by accumulating positrons over a wider time interval, even though the bunch width becomes larger, but is still much less than the typical measured timing intervals of ≃ 100 ns. Using a high permeability buncher core, a bunch width of 2.2 ns (FWHM) for 50 ns collection time and a repetition period of 960 ns has been achieved [21]. One of the problems encountered is the limitation of the voltage supplied by a post-amplifier to the buncher.…”

Generation of H-Atom Pulses and Associative Desorption of Hydrogen Isotopologues from Metal Surfaces

“…Today, femtosecond laser driven equivalent-time experiments have become a central tool in physics, chemistry and biology for studying inter-and intramolecular dynamics [2][3][4][5][6][7][8][9] . This scientific toolbox has been extended by short electron pulses [10][11][12][13] as well as other charged particles [14][15][16] .…”