FIRST OBSERVATION OF SELF-AMPLIFIED SPONTANEOUS EMISSION AT 1.064 MU-M

We report evidence of self-amplified spontaneous emission at 1064 nm. Single pass, on-axis microwiggler emissions into a 25 nm bandwidth hav e been recorded as a function of beam charge, and show a clear enhance ment over spontaneous emission after threshold. These are the first me asurements of SASE at such a short wavelength, and employ the smallest period wiggler used to date in a successful SASE experiment. The expe riment has been performed with the MIT microwiggler at the Accelerator Test Facility at BNL. A single micropulse at 34 MeV with a variable c harge of 0-1 nC and < 5 ps bunch length is passed through the microwig gler and emissions into a limited solid angle and bandwidth, selected by an aperture and interference filter, are focused onto a silicon pho todiode. Enhancement of the emissions from 2 to 6 times the spontaneou s emission level is observed at the highest charges. (C) 1998 Elsevier Science B.V. All rights reserved.