Coherent Electron Cooling

Cooling intense high-energy hadron beams poses a major challenge for modern accelerator physics. The synchrotron radiation emitted from such beams is feeble; even in the Large Hadron Collider (LHC) operating with 7 TeV protons, the longitudinal damping time is about 13 hours. None of the traditional cooling methods seem able to cool LHC-class protons beams. In this Letter, we present a novel method of coherent electron cooling based on a high-gain free-electron laser (FEL). This technique could be critical for reaching high luminosities in hadron and electron-hadron colliders.

Figure 1

A general schematic of the Coherent Electron Cooler (CEC) comprising three sections: A modulator; a FEL plus a dispersion section; and, a kicker. The FEL wavelength, $\lambda$, in the figure is grossly exaggerated for visibility.

Figure 2

The amplitude (blue line) and the phase (red line, in the units of $\pi$) of the FEL gain envelope after 7.5 gain lengths (300 period). Total slippage in the FEL is $300\lambda$, $\lambda =0.5\mu \mathrm{m}$. A clip shows the central part of the full gain function for the range of $\zeta =\{50\lambda ,60\lambda \}$.

Figure 3

A chromatic chicane tilts the wave fronts of charge-density modulation in an electron beam, making the electric field dependent on the horizontal position.