Fluxus. Prima, durante, dopo

Fluxus è stato definito il più radicale e sperimentale movimento artistico degli anni Sessanta. Dalla prima comparsa ad oggi è stato osannato, analizzato, dimenticato e riscoperto molte volte, tuttora però rimane una delle più grandi incognite critiche della storia dell’arte del Novecento. La ricerca si sviluppa secondo uno schema tripartito: indagare origini, ascendenze e ispirazioni; collocare e contestualizzare il periodo di nascita e sviluppo; esaminare influenze e lasciti. Attraverso un confronto di manifesti, scritti autografi e opere si è cercato di verificare punti di contatto e di continuità tra Fluxus e le Avanguardie Storiche, con particolare riferimento a Futurismo e Dadaismo. Successivamente si è cercato di ricostruire le dinamiche che hanno portato, alla fine degli anni Cinquanta, al definirsi di un terreno fertile dal quale sono germinate esperienze strettamente legate quali Happening, Performance Art e lo stesso Fluxus, del quale si sono ripercorsi i cosiddetti “anni eroici” per evidenziarne le caratteristiche salienti. Nella terza sezione sono state individuate diverse ipotesi di continuazione dell’attitudine Fluxus, dal percorso storico-filologico dei precoci tentativi di musealizzazione, alle eredità dirette e indirette sulle generazioni successive di artisti, fino alla individuazione di idee e concetti la cui attualità rende Fluxus un elemento imprescindibile per la comprensione della cultura contemporanea.

An experimental and theoretical approach to correct for the scattered radiation in an X-ray computer tomography system for industrial applications

The main problem connected to cone beam computed tomography (CT) systems for industrial applications employing 450 kV X-ray tubes is the high amount of scattered radiation which is added to the primary radiation (signal). This stray radiation leads to a significant degradation of the image quality. A better understanding of the scattering and methods to reduce its effects are therefore necessary to improve the image quality. Several studies have been carried out in the medical field at lower energies, whereas studies in industrial CT, especially for energies up to 450 kV, are lacking. Moreover, the studies reported in literature do not consider the scattered radiation generated by the CT system structure and the walls of the X-ray room (environmental scatter). In order to investigate the scattering on CT projections a GEANT4-based Monte Carlo (MC) model was developed. The model, which has been validated against experimental data, has enabled the calculation of the scattering including the environmental scatter, the optimization of an anti-scatter grid suitable for the CT system, and the optimization of the hardware components of the CT system. The investigation of multiple scattering in the CT projections showed that its contribution is 2.3 times the one of primary radiation for certain objects. The results of the environmental scatter showed that it is the major component of the scattering for aluminum box objects of front size 70 x 70 mm2 and that it strongly depends on the thickness of the object and therefore on the projection. For that reason, its correction is one of the key factors for achieving high quality images. The anti-scatter grid optimized by means of the developed MC model was found to reduce the scatter-toprimary ratio in the reconstructed images by 20 %. The object and environmental scatter calculated by means of the simulation were used to improve the scatter correction algorithm which could be patented by Empa. The results showed that the cupping effect in the corrected image is strongly reduced. The developed CT simulation is a powerful tool to optimize the design of the CT system and to evaluate the contribution of the scattered radiation to the image. Besides, it has offered a basis for a new scatter correction approach by which it has been possible to achieve images with the same spatial resolution as state-of-the-art well collimated fan-beam CT with a gain in the reconstruction time of a factor 10. This result has a high economic impact in non-destructive testing and evaluation, and reverse engineering.