Noncollimated bidirectional shearing interferometer for measuring a long radius of curvature

Lee, Yun Woo; Cho, Hyun Mo; Shin, Dong Joo; Lee, In Won

doi:10.1364/ao.36.005317

Cited by 5 publications

(1 citation statement)

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“…For the OK-5 FEL, to allow 10% of error in FEL gain, the mirror's radius of curvature measurement accuracy should be better than ±50 cm There exist several methods used to measure the mirror's radius of curvature, such as Newton ring, interferometer and direct measurement based upon the geometric optics principles, etc. [4] [5]. The direct measurement method has been used at DFELL for years.…”

Section: Introductionmentioning

confidence: 99%

Improved Long Radius of Curvature Measurement System for FEL Mirrors

Wu²,

Sun³

Proceedings of the 2005 Particle Accelerator Conference

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The 53.73 meter long Duke free electron laser (FEL) cavity consists of two concave mirrors with radius of curvature longer than 27 meters. A proper radius of curvature is designed to achieve an optimal and stable operation of the FEL. This requires accurate measurements of the cavity mirror's radius of curvature before its initial installation. Subsequent radius of curvature measurements are performed to ensure no significant deformation of the mirror occurs after a period of extensive use. A direct measurement based upon the geometric optics principles has been used at Duke FEL Lab (DFELL) for years. Recently, we have significantly upgraded this measurement apparatus by utilizing a He-Ne laser as the light source and a straight wire with a proper size as the object. In this paper we describe the details of the measurement setup and report the benefits of the recent upgrades. In addition, we report the improved data analysis technique and results of recent long radius of curvature measurements.

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Section: Introductionmentioning

confidence: 99%