Characterization of Carbon-Contaminated B4C-Coated Optics after Chemically Selective Cleaning with Low-Pressure RF Plasma

Boron carbide (B4C) is one of the few materials that is expected to be mostly resilient with respect to the extremely high brilliance of the photon beam generated by free electron lasers (FELs) and is thus of considerable interest for optical applications in this field. However, as in the case of many other optics operated at modern light source facilities, B4C-coated optics are subject to ubiquitous carbon contaminations. These contaminations represent a serious issue for the operation of high performance FEL beamlines due to severe reduction of photon flux, beam coherence, creation of destructive interference, and scattering losses. A variety of B4C cleaning technologies were developed at different laboratories with varying success. We present a study regarding the low-pressure RF plasma cleaning of carbon contaminated B4C test samples via inductively coupled O2/Ar, H2/Ar, and pure O2 RF plasma produced following previous studies using the same IBSS GV10x downstream plasma source. Results regarding the chemistry, morphology as well as other aspects of the B4C optical coating before and after the plasma cleaning are reported. We conclude from these comparative plasma processes that pure O2 feedstock plasma only exhibits the required chemical selectivity for maintaining the integrity of the B4C optical coating.Comment: 27 pages, 15 figure

Ungheria: le autorità indipendenti e la “democratic erosion”

SOMMARIO: 1. Introduzione. La democrazia ungherese: dalla transizione all’involuzione. 2. La trasformazione populista. 3. Le autorità indipendenti e la horizontal accountability. 4. La “cattura” della Commissione elettorale. 5. La riforma del sistema degli ombudsman. 6. Il settore dei media: un’Autorità potente al servizio del potere. 7. Conclusioni: le autorità indipendenti di garanzia come chiave di lettura del sistema ungherese attuale

L'involuzione democratica nel continente africano. Quali indicazioni dall'emblematico caso del Benin?

Lo scopo del lavoro è quello di studiare il fenomeno dell’involuzione democratica nell’eterogeneo contesto africano, concentrandosi in particolare sull’emblematico caso del Benin, un piccolo Paese generalmente riconosciuto fino a pochissimi anni fa come una delle maggiori speranze democratiche del continente. Le recenti riforme implementate dalla maggioranza di governo su impulso del Presidente della Repubblica Patrice Talon, spesso avallate dalla potente e leale Corte costituzionale, stanno progressivamente indebolendo le garanzie democratiche nel Paese, il quale sta indubbiamente facendo dei notevoli passi indietro.The aim of the paper is to study the democratic backsliding phenomenon within the heterogeneous African context, specifically focusing on the emblematic case of Benin, a small Country generally recognised as one of the continent’s best hopes until very few years ago. The recent reforms carried forward by the government majority on the impulse of the President of the Republic Patrice Talon, often endorsed by the decisions of the powerful and loyal Constitutional Court, are gradually weakening the democratic guarantees within the Country, which is therefore undoubtedly moving backwards