The final focus system for the Thomson X-ray scattering experiment termed PLEIADES (Picosecond Laser-Electron InterAction for Dynamic Evaluation of Structures) at LLNL demands ultra-high field gradient quadrupoles in order to focus electron beams to 10-20µm spot sizes. The final focus scheme is based on an ultra-high gradient of 560T/m quadrupole which employs the Halbach 16-piece, permanent magnet design. Use of this optimized geometry, NdFeB material, and a small bore of 5 mm allows the desired field gradient, and a few cm focal length, to be achieved. The adjustability of the focusing system is obtained by changing the relative longitudinal positions of sub-component focusing and defocusing magnets on precision movers.
|Remnant field [kG]||12|
|Inner radius [mm]||2.5|
|Outer radius [mm]||7.5|
|Field Gradient [T/m]
|Magnetic effective length [mm]||10.35|
|Integrated magnetic field strength [T]||6.0|
 RADIA page