화학공학소재연구정보센터
Materials Science Forum, Vol.363-3, 686-688, 2001
Set-up of a slow positron beam for Auger spectroscopy
At the new research reactor FRM II of the Technical University of Munich, an in-pile intensive slow positron source is currently built up. There, neutron capture gamma rays created by Cd-113(n,gamma)(114) Cd generate positrons by pair production [1]. One of the first planned experiments at this new positron source is positron induced Auger electron spectroscopy (PAES). In order to test the Auger facility in advance, a simple slow positron beam was constructed. At this, Cu-64 produced by activation of natural copper or alternatively Na-22 are used as beta (+) emitter. The high energy positrons are moderated in transmission geometry by an annealed tungsten foil and subsequently accelerated to some 10 eV into beam direction. A longitudinal magnetic field guides the positrons along a bent beamline into the Auger analysis chamber, where they are focused onto a sample by electric lenses. Recently, the slow positron beam intensity was measured by means of the annihilation signal of the incoming positrons, and amounts to 2(.)10(4) e(+)/s with the Na-22 source, resp. to 2(.)10(5) e(+)/s with 64Cu. Afterwards, the beam profile will be studied by a space-resolving micro channel plate detector in order to optimize beam characteristics. A beam diameter of approximately 1 cm is expected.