摘要: A high intensity variable energy positron beam has been constructed at Brookhaven National Laboratory (BNL). Positrons from a 97mCi (sup 22)Na source are moderated by a thin layer of solid neon. A magnetic guiding system delivered... 展开 A high intensity variable energy positron beam has been constructed at Brookhaven National Laboratory (BNL). Positrons from a 97mCi (sup 22)Na source are moderated by a thin layer of solid neon. A magnetic guiding system delivered up to 5(times)10(sup 6)e(sup +)/sec to an experiment. Currently tests are under way to facilitate the operation with the magnetic guiding system or -- for other experimental sites -- with an electrostatic beam transport. The electrostatic lenses are fabricated from (mu)-metal. No compensation of the earth magnetic field is required. Several experiments can utilize the beam on a time sharing basis. In the near future the source will be replaced by (sup 64)Cu which has a much higher activity. Beam intensities up to 10(sup 9)e(sup +)/sec are expected. 收起