Cavity optimization for compact accelerator-based free-electron maser
In previous works [1] we have successfully commissioned pre-bunched beam pumped free electron maser based on Stimulated Coherent Diffraction Radiation (SCDR) generated in an open resonator. An ultra-fast Schottky Barrier Diode (SBD) detector has enabled us to investigate the properties of the radiation in the range from 3 to 5 mm of wavelengths among broad frequencies stored in the cavity as well as the intrinsic properties of the cavity itself. We observed a turn-by-turn SCDR generated by a multibunch electron beam and directly measured the opened cavity quality factor of 11.4. In this report we represent the work directly related to optimization of both the maser system to achieve higher quality factor of the cavity essential to gain soft X-ray production via Thomson scattering in the next stage of the experiment and measurement system for better characterization of the maser light. One way of optimization is to minimize losses of energy due to transmission through resonator mirrors. For this purpose we have designed and constructed a test setup to investigate reflection and transmission properties of different mirror materials. Theoretical calculations have been performed using optical constants and theoretical models of electrical permittivity to compare with experimental results. In this report we summarize the experimental activity, represent new experimental results and represent steps undertaken to achieve the new resonator mirror design. For better understanding of the resonator performance a test of the SBD detector linearity is also demonstrated.
Diffraction Radiation from Relativistic Particles
Foreword Preface 1. Radiation from Relativistic Particles 2. General Properties of Diffraction Radiation 3. Diffraction Radiation at Optical and Lower Frequencies 4. Diffraction Radiation in the Ultraviolet and Soft X-Ray Regions 5. Diffraction Radiation at the Resonant Frequency 6. Diffraction Radiation from Media with Periodic Surfaces 7. Coherent Radiation Generated by Bunches of Charged Particles 8. Diffraction Radiation in the Pre-Wave (FRESNEL) Zone 9. Experimental Investigations of Diffraction Radiation Generated by Relativistic Electrons References
REFORMA DO ESTADO E AS POLÍTICAS PARA A EDUCAÇÃO SUPERIOR NO BRASIL NOS ANOS 90
This article aims at discussing the federal policies for higher education implemented in Brazil in the 1990s. It assumes that such policies are based on socio-political choices and interests linked to the changes occurring in the contemporary Brazilian scene, changes that have deep historical roots, which emerge in the process of reformation of the Brazilian State. This situation implies alterations in the field of public policies, and more particularly in that of social policies, since the on-going official proposals and projects are characterized by a decrease of the role of State. The borders between public and private affairs have become increasingly blurred in a process detrimental to the former. The contradictions in the federal policies for higher education are analyzed here, as well as their results as for the following fields: institutional diversification and differentiation; assessment criteria, broadening and privatization of this level of education.