Permanent Magnets Undulator for Terahertz FEL

TL;DR

This paper reports the development of a ferromagnetic undulator for terahertz free-electron lasers, featuring optimized magnetic field uniformity and focusing properties through magnetic element selection and displacement techniques.

Contribution

The creation and detailed characterization of a ferromagnetic undulator with improved magnetic field uniformity and focusing capabilities for terahertz FEL applications.

Findings

Magnetic field amplitude spread was reduced to 7%.

Additional windings compensated residual magnetic field spread.

Focusing gradient was achieved via pole displacement.

Abstract

The terahertz FEL ferromagnetic undulator has been created. The length of the undulator period is 9cm, number of the periods is 27. By means of selection and redistribution of magnetic elements the spread of amplitudes of the magnetic field was reduced to 7%. Additional windings of magnetic elements were used to compensate for residual spread. Required focusing gradient of magnetic field was obtained as a result of relative displacement of alternating poles with opposite charge of magnetic field along the x axis. Parameters of undulator including focusing properties in the horizontal plane were investigated.