Design of a harmonic generation FEL experiment at BNL

Abstract

We present the design parameters of a harmonic generation FEL experiment to be carried out at the Accelerator Test Facility (ATF) at BNL. Tl_s experiment will be carried out as a proof-of-principle for the proposed UV-FEL User's Facility at BNL. In the experiment we plan to triple the frequency of a CO2 seed laser by utilizing two superconducting wigglers and a dispersive section. The first wiggler will be used in conjunction with the CO2 seed laser to generate a ponderomotive force that will bunch the electron beam. The bunching will then be enhanced by the dispersion section. The second wiggler, tuned to the third harmonic of the seed laser will follow. In the beginning of the second wiggler the bunched beam will produce super-radiant emission (characterized by a quadratic growth of the radiated power), then the radiation will be amplified exponentia!ly. The last part of the wiggler will be tapered. We plan to study the evolution of the various radiation growth mechanisms as well as the coherence of the tripled and exponentially amplified radiation.

Linac-based short wavelength fels: The challenges to be overcome to produce the ultimate x-ray source–the x-ray laser

“…These experiment setups include the experiments at UCLA [ 151 and BNL [13], the LANLNCLA-experiment at LANL [16], LEUTL at ANL [18], the High-Gain Harmonic-Generation ( H G H G ) experiment at BNL [17], VISA at BNL [19] in the US and the TTF FEL at DESY [20] in Germany. The first three of these experiments were completed successfully in 1998.…”

Self-compensation for the axial velocity spread in a wiggler field

“…For a finite spot size, equilibrium occurs for kP > 0. However, for emittances typical of a high quality photo-injector [4,5], the beam is nearly in equilibrium for k1 = 0. We now consider numerical calculations of the electron orbits in a wiggler field with B 0 = 3 kG and X, = 27t/kw = 5 cm.…”

Technological challenges to X-ray FELs

“…Other important characteristics such as the saturation length and the power level at saturation have not been measured yet. Experiments are being prepared to complete the verification of the theory and to extend it towards the 1000Å region and below [9,10,11,12]. None of these experiments will be able to explore the SASE physics in the x-ray region near 1Å.…”