Antonio Grilli

The DAΦNE‐Light Facility

The new Synchrotron Radiation facility at Frascati exploits the intense photon emission from DAΦNE, the 0,51 GeV storage ring circulating over 1 A of electrons. Among the three beamlines commissioned, the Synchrotron INfrared Beamline At Daφne (SINBAD) is fully operational by a brilliant SR beam spanning the entire IR. Recently, the soft X‐ray beamline has been characterized and, once implemented the double‐crystal monocromator, X‐ray Absorption Spectroscopy is applied on material standards in the distinguishing energy region below 4 keV. An UltraViolet line, presently dedicated to photobiology dosimetry, has also given first results on cell irradiation in the UVB band.

Large-field high-resolution x-ray monochromatic microscope based on spherical crystals and high-repetition-rate laser-produced plasmas

The combination of a table-top laser produced plasma X-ray source and spherically bent crystals for the soft X-ray region is used in traditional X-ray microscopy schemes. The X-ray source is well localized both spatially (approximately 20 micrometer) and temporally (1 ps - 10 ns, it depends on the used laser) and it is spectrally tunable in a relatively wide range (6 - 19 angstrom). High quality monochromatic ((delta) (lambda) /(lambda) approximately 10-5 - 10-3) images with high spatial resolution (up to approximately 4 micrometer) and in a large field of view (few mm) are presented. For many applications, these low-cost compact systems can offer a simple alternative to the larger installations which are usually used. It was demonstrated that the spherically bent crystals can be efficiently used in a wide ((Theta) equals 40 - 90 degrees) range of reflection angles, thus allowing wide wavelength selection. A very efficient concentration of monochromatic X-Ray radiation into different spot shapes (line, circle spot, etc) is demonstrated.

X-ray contact microscopy using a plasma source generated by long and short (120-ns and 10-ns) excimer laser pulses

Soft x-ray contact microscopy (SXCM), using a pulsed x-ray source, offers the possibility of imaging the ultrastructure of living biological systems at sub-50nm resolution. We have developed a pulsed plasma x-ray source for this application, generated by the large volume XeCl laser Hercules. Various unstable optical resonator configurations were employed to achieve a high laser intensity to increase the conversion efficiency to water window x-rays (280-530eV). Optimum plasma conditions for SXCM are discussed, including the effect of pulse duration on image resolution. Soft x-ray contact images of Chlamydomonas dysosmos (unicellular alga) and the cyanobacteria Leptolyngbya are shown. In addition, the potential of producing a movie film of the development of x-ray images within the photoresist (acting as the recording medium) is discussed, following the resist development while viewing by atomic force microscopy.

Novel portable high-luminosity monochromatically tunable x-ray microscope

A novel experimental setup for transmission x-ray microscopy is presented. It is based on the use of a point isotropic x- ray source and a single spherical crystal. The x-ray beam intensity is modulated by the object attenuation, then monochromatized and enlarged using a spherical crystal and, lastly, imaged using a detector downstream of the crystal. We demonstrate by ray tracing technique and experimental testing that this system allows microscopy studies with image resolution better than the dimensions of the source, high magnification ratios, and great field of view. Microscopes using this model ca be easily built using different micro x-ray sources, like conventional x-ray tube generators, x-rays emitted by laser generated plasmas or synchrotron radiation. Utilization of spherically bent crystals to obtain high-resolution, large field, monochromatic images in a wide range of Bragg angles is demonstrated for the first time. High quality monochromatic images with high magnification about 15-35 times and spatial resolution over a large field of view were obtained. Some possible applications and preliminary experimental verification of the feasibility of the setup are also presented.

Atmospheric-pressure soft x-ray source for contact microscopy and radiobiology applications

A large volume non-conventional XeCl excimer laser (HERCULES) emitting long pulses (from 10 ns up to 120 ns at a wavelength of 308 nm) has been used to drive a soft x-ray plasma source. The x-rays pulse duration and the energy conversion efficiency in different spectral regions have been measured; x-rays emission lasting up to 100 ns has been obtained in the 70 eV region. The dependence of x-ray pulse duration on the size of the laser spot is discussed. The x- ray source can be operated both in vacuum and in helium at atmospheric pressure. This allows irradiating over a large area both for contact microscopy of living specimens (up to 1 mm2 windows) and for radiobiology (up to some cm2 windows). The experimental results obtained for these two applications as well as for radiographic images of living insects are discussed.

Electron beam lithography on LiF films for integrated active optical waveguides

Low energy electron beam irradiation of LiF single crystals and polycrystalline films induces efficient formation of stable laser active defects emitting in the visible spectral range at room temperature, together with a consistent increase of the real part of the refractive index in the same wavelength interval. The use of electron lithography techniques look promising for the realization of active channel waveguides.

Amplified spontaneous emission in e-beam induced LiF:F2 waveguides

Electron-beam lithography techniques allow realizing channel waveguides based on laser-active color centers in lithium fluoride (LiF) emitting in the visible. Amplified spontaneous emission (ASE) of red light from F2 defects has been observed in these confining structures: the appreciable values of the gain coefficient, several cm-1, with an exciting power density of few mW/cm2, makes LiF a good candidate for the realization of active integrated optical devices.

An innovative photochemical facility at DAΦNE-L

An on-going project for a photochemical facility at the DAFNE-L laboratory at the Frascati National Laboratories of INFN (National Institute of Nuclear Physics) is presented. Such a facility takes advantage from the combined capabilities of two different synchrotron radiation beam-lines. The first operates in the visible-UV and is used as a strong excitation and irradiation light-source in which both intensity and spectral range can be selected to fulfil the experiment requirements. The second is an infrared beamline equipped by FTIR micro-spectroscopy and imaging facility. An optical fiber allows UV irradiation of samples directly into the FTIR interferometer or the microscope. Thus, fast photo-chemical reactions can be analysed in real time, letting unveil inter-phases not normally observable by analysing the reagents and products of the reaction itself. Complex unstable systems can be irradiated and analysed without changing the sample condition (morphology, humidity, irradiation etc.). Preliminary experiments, validating most of the facility capability, will be presented.

A Vacuum Soft X‐Ray Reflectometer for the Characterization of Multilayer Mirrors by Synchrotron Radiation at DAΦNE

High‐reflectivity multilayers are required in many soft X‐ray researches, from nowadays Synchrotron Radiation (SR) to future Free Electron Laser (FEL) optics. These synthetic reflectors are capable of working at near‐normal incidence covering the lower X energy range not accessible by crystal diffraction. Recently, the deposition of such devices has progressed at INFN Legnaro Laboratories (LNL), giving robust Si/Mo mirror devices and first Ni/Ti and Ni/TiO2 multilayers. To test these new optics, at INFN Frascati Laboratories (LNF) a new vacuum compatible reflectometer has been assembled and commissioned in 2005. The final system is a θ‐2θ diffractometer in vacuum environment, endowed with high angular resolution and repeatability and absolute detectors. A direct characterization of multilayer performances have been accomplished by SR from a wiggler source at DAΦNE. Results on characterization of the vacuum reflectometer and on the new Ni‐Ti based multilayers are presented.

The soft X-ray beamline at Frascati Labs

DAΦNE-Light is the Synchrotron Radiation laboratory at the Laboratori Nazionali di Frascati (LNF)1. Three beamlines were commissioned since spring 2003 to exploit parasitically the intense photon emission from DAΦNE, the 0.5 1 GeV storage ring routinely circulating over 1 A of electrons. The soft X-ray beamline utilizes a wiggler source and, by a double-crystal fixed-exit monochromator, it is operational in the distinguishing energy window 1.5 - 4 keV range to be extended from the water window toward 6 keV. At present, the research activity is focused on X-ray Absorption Spectroscopy (XAS): precisely, X-ray Absorption Near Edge Spectroscopy (XANES) on the inner electronic levels of light elements and transition metals from Al to Ge and both d- and f-shells of higher Z atoms. Preliminary tests of X-ray imaging have been performed in view of applying different focusing optics, namely policapillary systems in trasmission and/or bent mica diffractor in back-reflection, for X-ray microscopy and spectromicroscopy experiments. The use of polycapillary systems (lenses, halflenses, capillaries) for studying features of radiation transportation by such structures (X-ray channelling, focusing, bending, etc.) has been planned.