Performance of an Intense Nuclear-Reactor Based Positron Beam

In this paper the performance of the high intensity (continuous) positron beam (POSH) at the Positron Centre Delft is presented. Positrons are created by pair-production induced by prompt gamma -rays produced in the core of a 2 MW research reactor at Delft. After one year of operation the initial beam intensity of 2x10(8) decreased to a stable 8x10(7) e(+) s(-1). Transport of the positrons over a distance of about 25 in by means of axial magnetic fields introduces an intensity loss of only 5%. A strong NdFeB magnet placed behind the target reduces the beam diameter from 15 to 3 mm. FWHM. In March 2000 the beam has become operational and was coupled to a 2D-ACAR set-up.