Using a Bent Tube as an Energy Filter for a Positron Beam. Simulations on Determining the Optimum Angle of the Bend

D. Dinescua,b and N. Djourelov a aUniversity Politehnica of Bucharest, Faculty of Applied Sciences, Splaiul Independentei, no. 313, 060042, Bucuresti, Romania bExtreme Light Infrastructure - Nuclear Physics, Horia Hulubei National Institute for Physics, and Nuclear Engineering, 30 Reactorului Str., 077125 Magurele, Ilfov county, Romania

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One way to perform: lifetime measurements at a DC positron beam is to pass positrons through a pulsing device. The compressed e+ bunches are accelerated to a desired energy for depth profiling of the studied sample. A fraction of the e+ that are backscattered from the sample surface can travel back through the uniform magnetic field that is generated along the central axis of the beam transport lines and reach the accelerator. The backscattered e+ that reach the accelerator can be re-accelerated towards the sample and re-implant in it with a delay from the initial implanted e+ bunch. These e+ that are re-implanted into the sample with a delay cause distortions in the lifetime spectra. A setup which uses a bent tube to act as an energy filter to reduce the effect of the backscattered e+ is studied by simulations. The simulations are performed in order to find the optimum geometry for minimum distortions.

DOI: 10.12693/APhysPolA.132.1624 PACS numbers: 41.75.Fr, 78.70.Bj