Development of a laced electromagnetic wiggler

The construction of a one-period wiggler system called a laced wiggler is presented along with test results from a prototype design. The laced electromagnetic wiggler is being developed to attain higher magnetic fields, shorter wavelengths, and larger gaps for the induction-linear accelerator, free-electron-laser (FEL) program. In the laced wiggler design, permanent magnets are located (laced) between the electromagnetic coils to increase the reverse-bias flux in the iron pole beyond that possible with only pole-edge (side) permanent magnets. This increase in reverse-bias flux allows wiggler operation at midplane magnetic-field intensities comparable to those of a hybrid permanent magnet/steel wiggler, but with field adjustability over a specified range. The maximum field intensity and tuning range are selected, within limits, for specific design requirements. The test results show good agreement with the analytical predictions and confirm the ability of the laced wiggler to attain the desired midplane magnetic flux density and tuning range. Both the nominal wiggle field along the wiggler axis and the focusing field variation are within the acceptable limits of design requirements.