The Cerenkov FEL, a source for next generation radar systems (TTN.3778)

The aim of the present proposal is the development of a versatile, high (peak) power, tunable Cerenkov Free Electron Laser (CFEL) operating in the millimetre and submillimetre wavelength region. This laser will cover part of a still existing gap in the spectrum where no high power, tunable and coherent radiation sources are available. It will increase available power levels by several orders of magnitude with continuous tunability. The advantage of a CFEL over normal FELs is the different dependence of wavelength on electron beam energy, i.e. the wavelength is reduced by decreasing the beam energy. This is the result of using a dielectric liner in a waveguide as a slow wave structure instead of an undulator. Using a beam energy ranging from 200 - 500 keV and a few different dielectric materials, it is possible to cover the spectrum from about 6 mm down to about 700 µm. In order to cover the same part of the spectrum with a normal FEL one needs beam energies ranging from 500 keV to about 2.5 MeV when using a fixed undulator period of 2.5 cm or with a fixed energy of 2.5 MeV, different undulators with periods ranging from 20 cm to 2.5 cm. The low energy electron beam results in less shielding problems and more compact equipment. It will be shown that the CFEL has saturation powers in the order of 100 kW at ~ 750 µm up to multimegawatts at ~ 6 mm corresponding to intrinsic efficiencies from a few tenth of a percent to about 20 %. The first year of the project will be used to complete and test the experimental set-up. The next year will be used to verify the above mentioned characteristics. Since the CFEL is conceptual similar to the travelling waves tubes used in radar, the development of the CFEL may result in the development of radar systems operating at shorter wavelength. These systems may be used for e.g. radar imaging and anti-collision systems. This will be a breakthrough in radar technology. To asses the usability of the CFEL in radars certain properties as a frequency chirp during the pulse or phase stability need to be demonstrated. Operating the CFEL as an amplifier requires a source which is equally tunable. A low power CFEL configured as an oscillator may be the most suitable source for such an amplifier. These topics will be addressed in the last two years of the project. A high power, tunable and coherent radiation source in the millimetre and submillimetre wavelength region will also stimulate basic researches in different fields e.g. such as hyperthermia (i.e. thermotherapy of cancer), non-linear phenomena in high T< sub>-super-conductors, plasma research etc., and it may have a large potential in industrial applications (e.g. where drying processes and/or (local) heating are required).

Computer simulations and design studies.

Er is één bedrijf bij dit project betrokken.

Prof.dr.ir. W.J. Witteman
Universiteit Twente
Faculteit Technische Natuurkunde
Postbus 217
7500 AE ENSCHEDE