Positron copper target

Figure 6 Positron target chamber and microwave cavity for measuring fine structure interval in the n=2 state of positronium. G, grid T, copper target M, mirror W, window K, CsTe photocathode of the uv photon detector A, antennae Nal(TI), annihilation y -ray detector.

Once in the copper target, the positrons behave in the same way as in the copper moderator (Figs. 3,4) with two important differences. First, the average incident energy of the e is SOO eV instead of 200 keV, so practically all the positrons are stopped in a short distance and diffuse back to the surface. 

Activation method — a target is placed at or near the reactor core, or the activated source is moved in and out of the reactor. Positrons can be created by activation of a source material (e g., copper) by thermal neutrons. The positrons can then be extracted after their emission or by moving the source material out of the activation zone to the experimental set up (as a solid source type or loop type). 

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