Calculation to Improve aberration

1
Introduction
Result and discussion
Calculation to Improve aberration
How many electrodes and magnetic poles are
necessary to obtain the potentials for the
condition 'C' ?
Suitable values of multipole components
Present Wien filter
New Wien filter
Aberration figures at the image plane
The shape of Wien filter


Image plane
Object plane

• Objective
• To estimate the sensitivity and the energy
  resolution of aberration-corrected multipole Wien
  filter.
• To determine the number of electrodes and
  magnetic poles.

Ideal electric and magnetic potential
Energy spectrum
Aberration figures at the image plane
Energy dispersion direction
Relationship between aberration coefficients and
multipole components

• Wien condtion Selection of electron with
  certain kinetic energy
• ?
• Stigmatic condition Correction of astigmatism ?
• Second order aberration correction condition
• Second order aberration coefficients
• Third order aberration correction condition
• Third order aberration coefficients

• Optimum number of electrodes and magnetic poles
  is 12.
• Transmission of new analyzer is 19 times better
  than that of previous one if shape of analyzer is
  included in our calculation.

Energy resolution dependence on acceptance angle

• Conclusion
• Improvement of the transmittance by the
  correction up to the 3rd-order aperture
  aberration
• ? The transmittance can be 26 times better than
  the Wien filter that we are using now in the
  ideal electric and magnetic fields.
• How many number of the electrodes and magnetic
  poles do we need ?
• ? 12 electrodes and magnetic poles can correct
  aberrations effectively.
• This new type of multipole Wien filter will
  bring us a user-friendly and bright EXPEEM system.

Transmission of new analyzer is 26 times better
than that of present one.
Necessary to eliminate aberration coefficients
using multipole components