Abstract
We present the development of a high power fiber laser system to investigate its suitability for use in a transverse electron beam profile monitor, i.e., a laserwire. A system capable of producing individual pulses up to $165.8\ifmmode\pm\else\textpm\fi{}0.4\text{ }\text{ }\ensuremath{\mu}\mathrm{J}$ at 1036 nm with a full width at half maximum of $1.92\ifmmode\pm\else\textpm\fi{}0.12\text{ }\mathrm{ps}$ at 6.49 MHz is demonstrated using a master oscillator power amplifier design with a final amplification stage in a rod-type photonic crystal fiber. The pulses are produced in trains of 1 ms in a novel burst mode amplification scheme to match the bunch pattern of the charged particles in an accelerator. This method allows pulse energies up to an order of magnitude greater than the steady-state value of $17.0\ifmmode\pm\else\textpm\fi{}0.6\text{ }\text{ }\ensuremath{\mu}\mathrm{J}$ to be achieved at the beginning of the burst with a demonstrated peak power of $25.8\ifmmode\pm\else\textpm\fi{}1.7\text{ }\mathrm{MW}$ after compression. The system is also shown to demonstrate excellent spatial quality with an ${M}^{2}=1.26\ifmmode\pm\else\textpm\fi{}0.01$ in both dimensions, which would allow nearly diffraction limited focusing to be achieved.
Highlights
For a future linear electron-positron collider such as the International Linear Collider (ILC) [1] and the Compact Linear Collider (CLIC) [2], the generation and transport of beams while preserving the low emittance is essential to achieve the required final focus beam sizes and high luminosity
Two methods to achieve this are wire scanners that measure a projection of the beam and optical transition radiation screens to image the beam directly [3], but these can both suffer damage from high charge density beams. Conventional methods such as these are disruptive to the beam and they cannot be used for measurement and tuning of the accelerator during operation, the development of new diagnostics is essential
In the case of a high energy collider (Ee > 50 GeV), the energy of the electrons is degraded by a large fraction and it would be possible to detect these electrons as they are lost from the lattice. Both can be used as a measure of the Compton-scattering rate, which is modulated as the laser focus is scanned transversely across the electron beam, providing a laserwire scan
Summary
For a future linear electron-positron collider such as the International Linear Collider (ILC) [1] and the Compact Linear Collider (CLIC) [2], the generation and transport of beams while preserving the low emittance is essential to achieve the required final focus beam sizes and high luminosity. In the case of a high energy collider (Ee > 50 GeV), the energy of the electrons is degraded by a large fraction and it would be possible to detect these electrons as they are lost from the lattice Both can be used as a measure of the Compton-scattering rate, which is modulated as the laser focus is scanned transversely across the electron beam, providing a laserwire scan. Transmissive optics afford a much greater scanning range and allow direct measurement of the focused spot size Given these advantages, a compromise is to use a visible wavelength generated by frequency doubling a near infrared source, which increases the resolution but reduces the peak power [8]. We consider the requirements for a laserwire at the ILC and present the results of a fiber laser
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