In November 2006, an ASTRE candidature was presented to the "Conseil Général de l’Essonne" and accepted under the name SELMA. This allowed to purchase a small electron linear accelerator based on a magnetron as RF source.    A positron source based on the principle of such a small accelerator of low energy has the advantage not to be classified as a nuclear installation (INB).
(Source de Positons de Haute Intensité)
  The project to measure the gravitational acceleration of antihydrogen atoms requires the production of a dense target of  positronium atoms, the e+e- bound state with a lifetime in the triplet state of 142 ns. A large amount of "slow" positrons (energy range from eV to a few keV) is necessary. Radioactive sources based on 22Na are not intense enough. Moreover, the efficiency of the moderation process, which allows to slow down the positrons, must be taken into account .

 

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