Design of a 980-MeV energy recovery linac

A 980-MeV energy recovery linac with radiofrequency (rf) of 1.5 GHz is designed. Electrons are accelerated by two passages through a 480-MeV superconducting linac, and decelerated by two subsequent passages. Recirculation is accomplished with six 60-degree bending magnets. The threshold current for beam breakup instability exceeds 100 mA. Gaussian bunches with normalized transverse emittances of 0.1 mm-mrad and rms length of 1.85 ps may be compressed by a factor of 180 (to a bunch length of 10 fs) with only a slight increase in transverse normalized emittance. Bunch charges up to 8 pC may be compressed at 980 MeV without excessive degradation from coherent synchrotron radiation, allowing operation with beam currents up to 12 mA.