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Undulator; free-electron laser; beam wander; phase shake; shimming.

A compact ultrafast terahertz (CUTE) free-electron laser (FEL) is being developed at the Raja Ramanna Centre for Advanced Technology (RRCAT), Indore. The undulator required for the CUTE-FEL has recently been developed. We have designed, built and characterized a variable gap, 5 cm period, 2.5 m long pure permanent magnet undulator in two identical segments. The tolerable error in the magnetic field was 1% in rms, and we have measured it to be 0.7%. The obtained rms phase shake is around 2°. To ensure that the trajectories do not have an exit error in position or angle, corrector coils have been designed. Shimming coils have been applied for both the undulator segments to reduce the amplitude of the betatron oscillations in the vertical trajectory. Details of novel corrector coils and soft iron shims are given and their performance is discussed.

B Biswas¹ V Kumar¹ S Chouksey² S Krishnagopal³

1. Beam Physics and FEL Lab., Raja Ramanna Centre for Advanced Technology, Indore 452 013, India
2. Indus Operations and Accelerator Physics Design Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013, India
3. Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India

Published

December 2008

Manuscript received

23 April 2008

Accepted

27 May 2008