Enrico Simonetti

Multilayer optics for hard x-ray astronomy by means of replication techniques

In this paper we will report on an activity undertaken with the aim of setting up a method for the realization of hard x-ray multilayer mirror astronomical optics based on a replication process. Our approach foresees the direct deposition of the multilayer stack on to the mandrel by ion-beam sputtering followed by the deposition of the Nickel by means of an electrolytic bath. The Nickel gives the mechanical strength to the mirrors. All deposited materials are later on separated from the mandrel by cooling it. This is a natural extension of the method already successfully used for the production of the soft x-ray optics with Au monolayer coating for the SAX, JET-X and XMM telescopes. This method is particularly convenient because permits not only of keeping the mirror supports very thin but also of achieving good imaging performances. Here we will present the main features of this method and the x-ray reflectivity and topographic results obtained from a first prototype flat sample we produced following this way.

Plastic substrate hardening by PE-CVD

The usage of plastic substrates has known a big enhancement driven by ophthalmic applications, but a further spreading can be foreseen in higher technological fields too. As known, two drawbacks are outlined when using these substrate: low scratching resistance; high thermal expansion coefficient, thus bad compatibility with the optical coatings made of inorganic layers. The most widespread solution up to now is a hardening and mechanical matching lacquer coating by dipping, which is well accepted in ophthalmics, but cannot be utilized in precision optics due to its intrinsic thickness disuniformity. Recently similar layers have been realized by Plasma Enhanced Chemical Vapor Deposition. This paper describes Ce.Te.V.s activities and results in setting up this coating by RF PE-CVD, aimed to both ophthalmics and precision optics. The two different functions (hardening and mechanical matching) and the performances of the coating-with special attention to scratch and thermal shock resistance-are examined. The experimental equipment and the optical and environmental characteristics are described.

Direct-current magnetron sputtering for optical coatings

The advantages of optical coatings realized by Sputtering versus thermal evaporation by crucible or Electron Gun, are very well known, but this technique is used only partially for dielectric coatings despite of a wide use in semiconductors and microcircuits, due to the slowness of RF Sputtering processes when starting from dielectric targets. This paper describes a DC Reactive Magnetron Sputtering technique from metal target set up at Ce.Te.V. for deposition of multilayer coatings, with cycle times comparable-or even faster-than conventional solution. The advantages of this process consist in obtaining films with high optical and mechanical performances with high repeatability on room temperature substrates. Pumping cycle can thus be faster and dead time for substrates heating and cooling down can be avoided, characteristics which plastic substrates can particularly take advantage of. Performances of the realized coatings on glass and plastic substrates, together with cycle time and material costs, are finally compared to results obtainable by Electron Beam Gun Reactive Deposition.