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UCLA Permanent Magnet Quadrupole Final Focus System


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.


Parameters Value
Magnetic material NdFeB
Remnant field [kG] 12
Inner radius [mm] 2.5
Outer radius [mm] 7.5
Length [mm] 10.0
Field Gradient [T/m]
Magnetic effective length [mm] 10.35
Integrated magnetic field strength [T] 6.0

External Links

[1] RADIA page