DIPAC2011 - List of Authors (Zolotorev, M.S.)

Paper	Title	Page
TUPD53	A Low-Power Laser Wire with Fiber Optic Distribution	425
	R.B. Wilcox, J.M. Byrd, M.S. Zolotorev LBNL, Berkeley, California, USA V.E. Scarpine Fermilab, Batavia, USA
	Funding: This work was supported by the US Department of Energy under contract DE-AC02-05CH11231. Laser-based position diagnostics for hydrogen ion (H⁻) beams typically use high power optical pulses that must be transported via free space to the diagnostic point. It is difficult to maintain stable alignment through such systems, especially when multiple channels are required. We describe a method for distributing low power, amplitude modulated pulse trains via fiber optic, and detecting interaction with the H⁻ beam by synchronous detection of the stripped electrons. Trains of 10 ps, 10⁶⁴ nm pulses at 400 MHz repetition rate are modulated by a 1 MHz signal that is the reference for a lockin amplifier. The average beam power is below one Watt. Synchronous detection at RF frequencies allows for efficient noise rejection when using optical powers below the nonlinear (Raman scattering) threshold of an optical fiber. The laser is synchronized with the bunch repetition rate, so the diagnostic can be used for bunch length measurements as well. We present results of tests of the optical system with 10⁰ m, single-mode fiber and realistic detected signal levels, demonstrating detection of the modulation signal with high signal-to-noise ratio and low nonlinearity.

Paper

Title

Page

A Low-Power Laser Wire with Fiber Optic Distribution

425

R.B. Wilcox, J.M. Byrd, M.S. Zolotorev
LBNL, Berkeley, California, USA
V.E. Scarpine
Fermilab, Batavia, USA

Funding: This work was supported by the US Department of Energy under contract DE-AC02-05CH11231.
Laser-based position diagnostics for hydrogen ion (H⁻) beams typically use high power optical pulses that must be transported via free space to the diagnostic point. It is difficult to maintain stable alignment through such systems, especially when multiple channels are required. We describe a method for distributing low power, amplitude modulated pulse trains via fiber optic, and detecting interaction with the H⁻ beam by synchronous detection of the stripped electrons. Trains of 10 ps, 10⁶⁴ nm pulses at 400 MHz repetition rate are modulated by a 1 MHz signal that is the reference for a lockin amplifier. The average beam power is below one Watt. Synchronous detection at RF frequencies allows for efficient noise rejection when using optical powers below the nonlinear (Raman scattering) threshold of an optical fiber. The laser is synchronized with the bunch repetition rate, so the diagnostic can be used for bunch length measurements as well. We present results of tests of the optical system with 10⁰ m, single-mode fiber and realistic detected signal levels, demonstrating detection of the modulation signal with high signal-to-noise ratio and low nonlinearity.