O.J. Luiten (Eindhoven University of Technology), will deliver a lecture
in the John Adams Institute for Accelerator Science series at 14.30 on
Thursday 8 October 2009 in the Fisher room, Denys Wilkinson Building,
Keble Road, Oxford.
Title: Generation of intense THz pulses using ultrashort, high-brightness
Radiofrequency (RF) photoguns, presently the brightest pulsed electron
sources, were originally developed as injectors for (X-ray) Free Electron
Lasers. In recent years exciting small-scale applications have emerged as
well, such as pulsed radiolysis, femtosecond electron diffraction, and
generation of intense THz pulses.
At Eindhoven University of Technology RF photoguns are being developed
which are characterized by full cylindrical symmetry and 100-fs
photoemission in the bunch blow-out regime. A new technological feature of
our 2nd generation 1.5 cell RF photogun is clamping of the different parts
instead of brazing, preventing deformation during the brazing process. Our
approach results in picosecond electron bunches of a few MeV with peak
currents in excess of 100 A and a normalized emittance better than 1
mm·mrad, corresponding to state-of-the-art brightness.
We have used these bunches to generate strong, single-cycle free-space THz
pulses by means of the coherent transition radiation (CTR) process. In
addition we have shown that the CTR process can be used to generate
intense single-cycle THz pulses coupled to the surface of a metal wire,
so-called surface plasmon polaritons (SPPs). SPPs propagating along a
metal wire can be focused to a spot much smaller than the wavelength by
simply tapering the wire into a sharp tip. In this way highly localized
fields of unprecedented strengths can be realized at THz frequencies,
opening up an entirely new experimental regime.
22 October 2009, Louis Rinolfi: CLIC
5 November 2009, Georg Hoffstaetter (tbc)