Generation of highly monochromatic positrons using cold moderators

Brown, B. L.; Crane, W. S.; Mills, A. P.
March 1986
Applied Physics Letters;3/17/1986, Vol. 48 Issue 11, p739
Academic Journal
Slow positron beams generally employ a radioactive β+ emitter with a crystal moderator in which the positrons thermalize. A small fraction of the thermalized positrons are desorbed at low (1–3 eV) energy, characteristic of the positron work function in the crystal. The energy width of the emitted positrons from W(110) and Ni(111) moderators can be narrowed significantly by cooling to liquid N2 temperatures. A practical configuration for a cooled moderator positron gun is presented which produces a narrow energy positron beam with good efficiency.


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