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EXPERIMENTAL ENERGY RESOLUTION OF A PARACENTRIC HEMISPHERICAL DEFLECTOR ANALYZER

EXPERIMENTAL ENERGY RESOLUTION OF A PARACENTRIC HEMISPHERICAL DEFLECTOR ANALYZER FOR DIFFERENT ENTRY POSITIONS AND BIAS. Theo J.M. Zouros. Presented by Giannis Gennarakis , Dept. of Physics, University of Crete - Heraklion. Part of Physics Undergraduate Diploma work.

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EXPERIMENTAL ENERGY RESOLUTION OF A PARACENTRIC HEMISPHERICAL DEFLECTOR ANALYZER

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  1. EXPERIMENTAL ENERGY RESOLUTION OF A PARACENTRIC HEMISPHERICAL DEFLECTORANALYZER FOR DIFFERENT ENTRY POSITIONS AND BIAS Theo J.M. Zouros Presented by Giannis Gennarakis, Dept. of Physics, University of Crete - Heraklion Part of Physics Undergraduate Diploma work

  2. Based on our recent publication Must be a record! And related to the APAPES project (THALIS): http://apapes.physics.uoc.gr/ (see poster) And to our Charged Particles Optics Erasmus IP: http://cpots2013.physics.uoc.gr/

  3. Charge particle optics:The ideal Hemispherical Deflector Analyzer (HDA) 1st order focusing in ideal 1/r2E-field 1938 object image 1st order focusing of charged particles in the dispersion plane of an ideal (1/r2E-field ) spherical sector (analogous to Barber’s rule for homogeneous B-field spectrographs) HDA = spherical sector with Φ=π HDA Main electron analyzer at SYNCHROTRONs and FELs

  4. Related activities http://cpots2013.physics.uoc.gr/ http://apapes.physics.uoc.gr/ (see poster 10 – THALIS grant) Postdoc position available NOW: Salary ~26.5k€/year (bruto) Enquire: tzouros@physics.uoc.gr

  5. Ideal vs. Real fields Ideal The ideal field in an HDA form semicircular equipotentials Since the potential V=V(r) NO FRINGING FIELDS!!! – analytical solution valid

  6. Ideal vs. Real fields Ideal Real The ideal field in an HDA form semicircular equipotentials Since the potential V=V(r) NO FRINGING FIELDS!!! – analytical solution valid In deflectors the ideal field is necessarily modified by the aperture plate producing fringing fields near the plate ANALYTICAL SOLUTION NOT VALID!!! - Must use numerical simulations (SIMION) Fringing fields (mostly!) lead to inferior focusing conditions!

  7. The fringing field problem of an HDA - proposed solutions The biased paracentric entry HDA All this discovered by SIMION!

  8. experimental setup to test resolution • ESCA-type spectrometer (HDA & Lens) • R0 = 84, 100, 112 mm Build by colleagues in Afyon e- gun Input lens HDA Detector Movable support for e-gun, gas jet and input lens Target gas nozzle Jet

  9. General Potential V ( r ) in an ideal HDA Experimental details – line shape Exit Beam Width Experimental Line shape Energy resolution

  10. FINAL RESULTS

  11. Numerical results - conclusions • The two paracentric entries are found experimentally to have a base resolution of 1.64 and 1.97 times better than the conventional entry • This resolution improvement is attained without introducing any new electrodes but purely by taking advantage of the fringing fields of the HDA itself which are used as a lens • SIMION simulations mostly support the experimental results

  12. I would now like to demonstrate a SIMIONrun for you

  13. Thank you for your attentionany questions? I would now like to demonstrate a SIMION run for you

  14. General Potential V ( r ) in an ideal HDA Some formulas Exit Beam Width Overall Base Resolution Base Resolution

  15. Two entry positions give good results

  16. Comparison: IDEAL VS. FRINGING FIELDS

  17. Various fringing field correction schemes

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