Author/Authors :
Alberola، نويسنده , , N. and Anthonioz، نويسنده , , T. and Badertscher، نويسنده , , A. and Bas، نويسنده , , C. and Belov، نويسنده , , A.S. and Crivelli، نويسنده , , P. and Gninenko، نويسنده , , S.N. and Golubev، نويسنده , , N.A. and Kirsanov، نويسنده , , M.M. and Rubbia، نويسنده , , A. and Sillou، نويسنده , , D.، نويسنده ,
Abstract :
We have developed a high-efficiency pulsed slow positron beam for experiments with orthopositronium in vacuum. The new pulsing scheme is based on a double-gap coaxial buncher powered by an RF pulse of appropriate shape. The modulation of the positron velocity in the two gaps is used to adjust their time-of-flight to a target. This pulsing scheme allows to minimize non-linear aberrations in the bunching process and to efficiently compress positron pulses with an initial pulse duration ranging from ∼ 300 to 50 ns into bunches of 2.3 to 0.4 ns width, respectively, with a repetition period of 1 μ s . The compression ratio achieved is ≃ 100 , which is a factor 5 better than has been previously obtained with slow positron beams based on a single buncher. Requirements on the degree, to which the moderated positrons should be mono-energetic and on the precision of the waveform generation are presented. Possible applications of the new pulsed positron beam for measurements of thin films are discussed.
