BIW2012 - List of Authors (Fong, N.W.)

Paper	Title	Page
TUPG035	Evaluation of New, Fast Wire Scanner Designs for the LCLS	210
	P. Krejcik, M.L. Campell, N.W. Fong, J.C. Frisch, H. Loos SLAC, Menlo Park, California, USA
	Funding: This work was supported by Department of Energy Contract No. DE-AC0276SF00515. Transverse beam size measurement for emittance tuning of the LCLS electron beam relies on wire scanners strategically placed on the beam line. It was originally intended to use Optical Transition Radiation (OTR) screens to obtain single shot measurements of the transverse beam size but it was soon discovered that the Coherent OTR that is a feature of ultra-short bunch length operation in linac FELs swamped the signal and rendered this diagnostic unusable. The original SLAC wire scanners that have been in operation for about 20 years are fairly slow and not optimized for the rapid measurements needed to monitor and fine tune the very small LCLS beam emittances, taking over a minute to complete a measurement in both planes. Two new wire scanner designs are being tested at LCLS that make use of state-of-the-art mechanical slides and position read-back systems to make fast, vibration-free measurements of the beam size. One uses an in-vacuum piezo-controlled linear slide and the other uses a dc linear servo motor coupled through a pair of vacuum bellows. The merits of the two designs are compared to the original SLAC design that relies on a ball screw driven by a stepping motor.

Paper

Title

Page

Evaluation of New, Fast Wire Scanner Designs for the LCLS

210

P. Krejcik, M.L. Campell, N.W. Fong, J.C. Frisch, H. Loos
SLAC, Menlo Park, California, USA

Funding: This work was supported by Department of Energy Contract No. DE-AC0276SF00515.
Transverse beam size measurement for emittance tuning of the LCLS electron beam relies on wire scanners strategically placed on the beam line. It was originally intended to use Optical Transition Radiation (OTR) screens to obtain single shot measurements of the transverse beam size but it was soon discovered that the Coherent OTR that is a feature of ultra-short bunch length operation in linac FELs swamped the signal and rendered this diagnostic unusable. The original SLAC wire scanners that have been in operation for about 20 years are fairly slow and not optimized for the rapid measurements needed to monitor and fine tune the very small LCLS beam emittances, taking over a minute to complete a measurement in both planes. Two new wire scanner designs are being tested at LCLS that make use of state-of-the-art mechanical slides and position read-back systems to make fast, vibration-free measurements of the beam size. One uses an in-vacuum piezo-controlled linear slide and the other uses a dc linear servo motor coupled through a pair of vacuum bellows. The merits of the two designs are compared to the original SLAC design that relies on a ball screw driven by a stepping motor.