Speaker
Description
Laser heaters suppress microbunching instabilities in free-electron laser (FEL) injectors by increasing the uncorrelated slice energy spread. We investigate third-harmonic laser–undulator heating in the Linac Coherent Light Source-I (LCLS-I) injector and compare measurements of central slice energy spread versus laser pulse energy for fundamental and third-harmonic interactions. At moderate to high laser energies, the third-harmonic measurements follow the expected scaling with laser energy and harmonic coupling. At lower laser pulse energies, both configurations exhibit additional structure beyond a simple transverse overlap heating model, possibly associated with three-dimensional longitudinal space-charge (LSC) and transport effects. These results demonstrate the feasibility of third-harmonic laser heating in an operational injector, enabling heater operation at reduced beam energy or under constrained machine configurations.
Funding Agency
Work supported in part by US Department of Energy contract number
DE-AC02-76SF00515.
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