cpots2012.physics.uoc.gr Dept. of Physics, University of Crete Aug 19 – Sept 2, 2012

1. UCM CPOTS – 2nd ERASMUS Intensive ProgramIntroduction to Charged Particle Optics: Theory and Simulation http://cpots2012.physics.uoc.gr Dept. of Physics, University of Crete Aug 19 – Sept 2, 2012 Heraklion, Crete, GREECE

2. Fringing fields of a parallel plateanalyzer (PPA) • Project 4 (for Unit 3) References: L3.1, L3.2, L3.4 Prof. BélaSulik Univ. of Debrecen & MTA Institute of Nuclear Research (Atomki) E-mail: sulik@atomki.hu • Dominik Schrempf • SpirosDoukas • Yasemin Gündoğdu

3. Goals • Learnthedifferencebetweenideal andrealsituations • Learnwhathappensifthefıeld is not terminatedbyspecialelectrodes • Study the distorded 450 field analyser • Do we need a field termination for a good PPA?

4. Ideal 450 PPA The development of fringing fields is prevented by the ideal grids in the slits Plate length L = 15mm Plate distance D0 = 3 mm Slit distance L0 = 10 mm Slit size w2 = 0.4 mm Ekin of electrons E0 = 1000 eV Upper plate voltage V0 = -600 V

5. Energy spectrum of an ideal PPA with broad slits. Plate length L = 15mm Plate distance D0 = 3 mm Slit distance L0 = 10 mm Slit size w2 = 0.4 mm Elevation angle varies from 400 to 50o

6. Ideal PPA with source outside We observe that if we move the source of the electrons lower, the focus point moves higher than the exit slit Plate length L = 15mm Plate distance D0 = 3 mm Slit distance L0 = 10 mm Slit size w2 = 0.4 mm Ekin of electrons E0 = 1000 eV Upper plate voltage V0 = -600 V

7. Energy spectrum of an ideal PPA with source outside and broad slits. Plate length L = 15mm Plate distance D0 = 3 mm Slit distance L0 = 10 mm Slit size w2 = 0.4 mm Elevation angle varies from 400 to 50o

8. In this analyzer we have removed the ideal grids and we observe fringing fields in the area around the slits Ekin of electrons E0 = 1000 eV Upper plate voltage V0 = -600 V Plate length L = 30 mm Plate distance D0 = 6mm Slit distance L0 = 20 mm Slit size w2 = 0.8 mm

9. 450 PPA with fringing fields As an effect of the fringing field, the beam isn’t focused in the exit slit. Plate length L = 30 mm Plate distance D0 = 6mm Slit distance L0 = 20 mm Slit size w2 = 0.8 mm Ekin of electrons E0 = 1000 eV Upper plate voltage V0 = -600 V

10. In the following figure we can see the distortion of the field near the exit slit and near the edge of the plate

11. Energy spectrum of a PPA with fringing fields. Plate length L = 30 mm Plate distance D0 = 6mm Slit distance L0 = 20 mm Slit size w2 = 0.8 mm Elevation angle varies from 400 to 50o

12. In this analyzer we have increased the size of the surrounding box and the distortion of the field becomes stronger

13. 450 PPA with fringing fields As an effect of the fringing field, the beam isn’t focused in the exit slit. Plate length L = 30 mm Plate distance D0 = 6 mm Slit distance L0 = 10 mm Slit size w2 = 0.8 mm Ekin of electrons E0 = 1000 eV Upper plate voltage V0 = -600 V

14. In the following figure we can see the distortion of the field near the exit slit and near the edge of the plate

15. Energy spectrum of a PPA with fringing fields. Plate length L = 30 mm Plate distance D0 = 6 mm Slit distance L0 = 20 mm Slit size w2 = 0.8 mm Elevation angle varies from 400 to 50o

16. Next, we reduce the size of the plates along the z-direction too. Plate width W = 5mm Plate distance D0 = 6 mm Slit distance L0 = 20 mm Slit size w2 = 0.8 mm Ekin of electrons E0 = 1000 eV Upper plate voltage V0 = -625 V

17. In order to have a focused beam on the exit slit with this item, we have to adjust the potential of the upper plate to V0=-623 V Plate width W = 5mm Plate distance D0 = 6 mm Slit distance L0 = 20 mm Slit size w2 = 0.8 mm Ekin of electrons E0 = 1000 eV Upper plate voltage V0 = -625 V

18. Thank you for your attention