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Beam Diagnostic Instrumentation for Free Electron Lasers and 3rd Generation Light Sources


Advanced electron-beam diagnostic instruments are needed to support the development of X-ray Free Electron Lasers (FEL), as well as the operation and upgrade of 3rd generation light sources. Grant applications are sought to develop monitors for beam position and electron bunch length. The beam position monitor should have nanometer resolution and associated electronics for both linac and storage ring applications. The electron beam bunch length monitor should perform non-destructive measurements, be capable of single-bunch resolution better than 100 fs, and possess a system design that is relevant for the bunch parameters of the future X-ray FEL and 3rd generation light sources.

Grant applications also are sought to develop diagnostic devices for the non-destructive measurement of electron beam emittance and for the energy spread within electron bunches. For FEL applications, measurements of electron bunch properties require resolution on the order of 10 ?m, so that the so-called “slice” properties can be determined with sufficient accuracy. Both
the beam emittance and the energy spread of the beam are critical parameters in FELs, and the measurement techniques must allow for rapid and noninvasive tuning, as well as for the implementation of feedback systems for systems optimization. Approaches of interest include optical techniques that employ transition radiation or synchrotron radiation. The diagnostics should be small (< 1 m length scale) and suitable for integration into an operational light source.

Grant applications also are sought to develop diagnostics for the measurement of charge modulation within an electron bunch at optical wavelengths in the regime 50-1000 nm. Seeded FELs utilize an inverse FEL scheme to first introduce an energy modulation into an electron bunch; then a dispersive transport region converts the energy modulation into a charge density modulation along the electron bunch. The charge density is modulated with the same period as
the laser, i.e., in the wavelength regime 50-1000 nm.

Grant applications are sought to develop a diagnostic technique for the dynamic measurement of the transverse position of the centroid of an electron bunch, as a function of position along that bunch. The transverse wakefields in a linac may introduce the so-called “banana shape” beam as a result of the beam-breakup instability, in which deflecting wakefields introduce a transverse spatial offset in the electron distribution along a bunch. Proposed diagnostics must be able to measure this effect with spatial resolution on the order of 1 ?m, and with temporal resolution (along the bunch) of 10-100 fs, in bunches of peak current 10-500 A.

Finally, grant applications are sought to develop high resolution multi-function diagnostics cavity beam position monitors (BPMs), which are well suited for LINAC applications as well as for advanced storage rings and energy recovery linacs (ERLs), represent one approach of interest. Such cavity BPM diagnostics should (1) have measurement capabilities that include sub-micron positioning, beam tilt, and charge; and (2) be physically small and low cost, in order to enable commercialization.

Questions – contact Eliane Lessner,

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