I. Spassovsky

Compact, High-Power Electron Beam Based Terahertz Sources

Although terahertz (THz) radiation was first observed about 100 years ago, this portion of the electromagnetic spectrum at the boundary between the microwaves and the infrared has been, for a long time, rather poorly explored. This situation changed with the rapid development of coherent THz sources such as solid-state oscillators, quantum cascade lasers, optically pumped solid-state devices, and novel coherent radiator devices. These in turn have stimulated a wide variety of applications from material science to telecommunications, from biology to biomedicine. Recently, there have been two related compact coherent radiation devices invented able to produce up to megawatts of peak THz power by inducing a ballistic bunching effect on the electron beam, forcing the beam to radiate coherently. An introduction to the two systems and the corresponding output photon beam characteristics will be provided.

THz-ARTE: non-invasive terahertz diagnostics for art conservation

The project THz-ARTE ldquoTerahertz Advanced Research TEchniques for non-invasive analysis in art conservationrdquo has recently been selected in the area of Technologies applied to Cultural Heritage in the framework of the Agreement between the Government of Italy and the Government of Japan on cooperation in Science and Technology.

Reflective terahertz imaging at the ENEA FEL facility

The development of both transmissive and reflective THz imaging is under way at ENEA-Frascati employing a THz compact free electron laser (THz GFEL). The high peak power available makes the FEL particularly suitable for long range detection. Different setup was tested at different levels of spatial resolution to image objects from a few centimetre square to larger sizes.

Double free-electron laser oscillator for photon-photon collisions

In view of a quantum electrodynamics test, a “double” free-electron laser (FEL) oscillator is proposed as a possible device for head-on photon–photon collisions in vacuum. The oscillator is conceived in order to produce two laser beams in the same cavity by two counterpropagating electron beams. The latter are in turn exploited to produce gamma photons by backward Compton scattering of the intracavity FEL radiation itself. In view of an effective device design, specific ranges of values for the various parameters, that characterize the system, are individualized for operation at the maximum of the γ–γ scattering cross section. An estimate of the collision rate in definite device configurations is provided.

Detection of terahertz radiation by AlGaN/GaN field-effect transistors

High electron mobility transistors can work as room-temperature direct detectors of radiation at frequency much higher than their cutoff frequency. One open issue is how the radiation couples to the sub-wavelength transistor channel. Here, we studied the coupling of radiation to an AlGaN/GaN transistor with cut-off frequency of 30 GHz. Local irradiation with a Free Electron Laser source at 0.15 THz allowed us to selectively couple the signal to the channel through one transistor terminal at a time. Far-field experiments at 0.15–0.94 THz were also performed in order to study the nonlinear properties of the transistor channel.

Future seeding experiments at SPARC

This communication describes the research work plan that is under implementation at the SPARC FEL facility in the framework of the DS4 EUROFEL programme. The main goal of the collaboration is to study and test the amplification and the FEL harmonic generation process of an input seed signal obtained as higher order harmonics generated both in crystals (400 nm and 266 nm) and in gases (266 nm, 160 nm, 114 nm). The SPARC FEL can be con-figured to test several cascaded FEL layouts that will be briefly analysed.

Imaging in the frequency range between 100 GHz and 1 THz using Compact Free Electron Lasers

At ENEA-Frascati THz imaging experiments have been set-up in the biological and environmental field utilizing a Compact Free Electron Laser (C-FEL) at 130 GHz [1], and a second source, FEL-CATS, operating in the range 0.4 to 0.7 THz [2].

Pathway to a compact SASE FEL device

Abstract Newly developed high peak power lasers have opened the possibilities of driving coherent light sources operating with laser plasma accelerated beams and wave undulators. We speculate on the combination of these two concepts and show that the merging of the underlying technologies could lead to new and interesting possibilities to achieve truly compact, coherent radiator devices.

High-quality electron beam with nonadiabatic electrostatic pumping

In this paper we report on the numerical results for a nonadiabatic beam pumping method by electrostatic modulation. A 700 kV, several hundred amperes nonadiabatic gun is able to produce a high-quality hollow electron beam with pitch ratio of 0.6, perpendicular spread of 1.5% and longitudinal spread of 0.1% after adiabatic magnetic compression. >

Beam–Wave Interaction From FEL to CARM and Associated Scaling Laws

The development of a microwave tube providing high output power (~1 MW) at a high frequency (~250 GHz) with high efficiency of the beam–wave power conversion is a challenging task. A great deal of theoretical and experimental efforts is directed toward such a goal. A promising powerful source of microwave radiation is the cyclotron autoresonance maser (CARM) oscillator. In this paper, we revisit the well-known physical models in a way, which is suitable for their implementation in the numerical tools for computer-aided design and optimization of a CARM operating at high frequency. The analysis developed by us is an attempt directed toward the realization of an adequate design tool for the development of CARM devices.