Wien Filter

The Wien filter separates the beam according to their velocities. When this velocity separation works effectively, a pure RI beam can be obtained after the Wien filter.

The high voltages are on development toward maximum voltages of +/-200 kV. Currently high voltages of +/-50-70 kV is available most of the time, but +/-100 kV or more may require several weeks (or months) for the conditioning (aging). Users should consider how much high voltages are needed. If you intend to use high voltages more than +/-100kV, ask conditioning beforehand.

The distance between the electrodes is 80 mm, and the maximum magnetic field is 0.3 T.

The measured velocity dispersion was 2.1 mm/% (%...1% difference in velocity). at the entrance of the F3 chamber, when the high voltages are +/-50kV. In typical measurements, seperations of more than 10-15 mm against the nearest contamination would make the beam purity almost 100%.

The transmission of the Wien filter is more than 70% for the primary (small dispersive) beam, and 30% for a typical secondary beam.

The optics of the Wien filter was made so that the image of the F2 and F3 are the same (unity magnification). The secondary beam size is usually 10 mm or less at the entrance of the F3 chamber, but in the downstream side of the F3 chamber (60-80 cm distant from the PPAC A), the diameter (FWHM) of the secondary beam will be 25-30 mm.


  • How much is the needed high voltages?
  • How much is the distance between the F3 PPAC A and your target?