Magnetic Measurements of a Third Harmonic Table-Top Undulator for Free Electron Lasers

Abstract

We describe the measurement studies of a third harmonic undulator. The harmonic undulator is fabricated by placing shims at suitable locations along the length of a table-top six-period planar undulator. The undulator field is measured with a Hall probe and pulsed wire bench. The pulsed wire data show good agreement with the Hall probe data.

Design and magnetic measurements of bi-harmonic undulators for free electron laser

“…Neverthless the method is powerful tool in designing dual harmonic undulator FEL scheme proposed earlier [20]. The scheme is also useful in designing even harmonic emission on axis that will lead eventually to the design of N-frequency undulator based free electron laser as proposed [6,7].…”

“…The seventh harmonic is less than 1%. All other odd higher harmonic gets eliminated at this shim gap [7].…”

“…At the gaps of 24 mm, 27 mm, 30 mm, there is no higher harmonic emission. The design principle of third harmonic undulator is discussed by Mona et al [7]. The 50 mm period undulator has 13 vertical (V = 13) and 12 horizontal magnets (H = 12) including the end half magnets.…”

“…The Novosibirsk Tera Hertz FEL successfully lased on the third harmonic [17] and the harmonic lasing in an XFEL has been experimentally demonstrated too [18]. The biharmonic undulator field is expressed as, B = ∑ ∞ h=1 ŷB h sin(hk u z) [6] and recently a third harmonic undulator has been fabricated and reported [7].…”