Shaftan, T.
(Timur Shaftan)

WEAIS01 Experimental Demostration of Wavelength Tuning in High-Gain Harmonic Generation Free Electron Laser
Timur Shaftan, Erik Johnson, Sam Krinsky, Henrik Loos, James Murphy, George Rakowsky, James Rose, Brian Sheehy, John Skaritka, Xijie Wang, Zilu Wu, Li-Hua Yu (BNL/NSLS, Upton, Long Island, New York)

We present experimental results on tuning of the HGHG FEL output wavelength while holding the input seed wavelength constant. Using compression of the initially chirped beam in the HGHG dispersion section we have measured the wavelength shift of about 1% around the nominal value of 266 nm. The tuning range is expected to reach 3 % after the dispersive section upgrade at the DUV FEL. An optimized design based on this principle, using additional linac sections, would have the capability of providing full tunability.

WEAOS02 Spectral Phase Modulation and chirped pulse amplification in High Gain Harmonic Generation
Zilu Wu, Erik Johnson, Sam Krinsky, Henrik Loos, James Murphy, Timur Shaftan, Brian Sheehy, Yuzhen Shen, Xijie Wang, Li-Hua Yu (BNL/NSLS, Upton, Long Island, New York)

High Gain Harmonic Generation (HGHG), because it produces longitudinally coherent pulses derived from a coherent seed, presents remarkable possibilities for manipulating FEL pulses. If spectral phase modulation imposed on the seed modulates the spectral phase of the HGHG in a deterministic fashion, then chirped pulse amplification, pulse shaping, and coherent control experiments at short wavelengths become possible. In addition, the details of the “transfer function” will likely depend on electron beam and radiator dynamics and so prove to be a useful tool for studying these. Using the DUVFEL at the National Synchrotron Light Source at Brookhaven National Laboratory, we present spectral phase analyses of both coherent HGHG and incoherent SASE ultraviolet FEL radiation, applying Spectral Interferometry for Direct Electric Field Reconstruction (SPIDER), and assess the potential for employing compression and shaping techniques.

WEBOS02 Generation of Terahertz Radiation by Modulating the Electron Beam at the Cathode
Jonathan Neumann, Ralph Fiorito, Patrick Gerard O'Shea (IREAP, College Park, Maryland), G.L. Carr (BNL, Upton, Long Island, New York), Henrik Loos, Timur Shaftan, Brian Sheehy, Yuzhen Shen, Zilu Wu (BNL/NSLS, Upton, Long Island, New York), Henry Freund (SAIC McLean, McLean)

A bunched electron beam can be used to generate coherent radiation in a particle accelerator. This experiment, a collaboration between the University of Maryland and the Source Development Laboratory at Brookhaven National Laboratory, uses a drive laser modulated at terahertz frequencies in an RF-photoinjecting electron accelerator to produce a bunched beam at the cathode. The experiment is designed to determine if such a scheme could be used to develop a compact, high power terahertz emitter. After acceleration to approximately 72 MeV, a mirror intercepts the beam. The backwards transition radiation from the mirror is measured with a bolometer. The experiment was conducted at various modulation frequencies and levels of charge.

THPOS62 Preliminary Measurements of the High-Gain FEL Radiation Properties along the Radiator
Timur Shaftan, Henrik Loos, Brian Sheehy, Li-Hua Yu (BNL/NSLS, Upton, Long Island, New York)

We present experimental results on evolution of properties of the DUV FEL output radiation along the radiator. Intercepting the electron beam at the different locations inside the undulator we recorded and analyzed transverse profiles, spectra and intensity of the FEL output. Shot-to-shot fluctuations of the FEL radiation may significantly affect the accuracy of measurement. In the paper we present and discuss a single-shot measurement technique, based on a special imaging system.