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.

At the Laboratori Nazionali di Frascati of the INFN to monitor real time bunch behavior of the positron ring of the DAΦNE collider a novel diagnostics experiment has been set-up on a bending magnet exit port of the positron ring. The front-end of the experiment consists of a UHV chamber where a gold-coated plane mirror deflects the radiation through a ZnSe window. After the window, a compact optical layout in air focuses the radiation on compact mid-IR fast uncooled HgCdTe photodiodes used to measure the bunch-by-bunch emission. Alignment of the mirrors and a first characterization of the radiation emitted have been performed. Here we present the longitudinal measurements of the bunch behavior in the time domain performed with fast IR detectors. This novel diagnostics is ready to allow real time monitoring of the bunch-by-bunch positron emission. The system has been designed to improve the DAΦNE diagnostics with the main aim to identify and characterize longitudinal bunch instabilities. Possible upgrades to improve detection capabilities in the transverse plane are considered.

At the Laboratori Nazionali di Frascati of the National Institute of Nuclear Physics (INFN) an infrared (IR) array detector with fast response time has been built and assembled in order to collect the IR image of e-/e+ sources of the DAΦNE collider. Such detector is made by 32 bilinear pixels with an individual size of 50x50 μm2 and a response time of  1 ns. In the framework of an experiment funded by the INFN Vth Committee dedicated to beam diagnostics, the device with its electronic board has been tested and installed on the DAΦNE positron ring. A preliminary characterization of few pixels of the array and of the electronics has been carried out at the IR beamline SINBAD at DAΦNE. In particular the detection of the IR source of the e- beam has been observed using four pixels of the array acquiring signals simultaneously with a four channels scope at 1 GHz and at 10 Gsamples/s. The acquisition of four pixels allowed monitoring in real time differences in the bunch signals in the vertical direction. A preliminary analysis of data is presented and discussed. In particular we will outline the correlation between signals and displacements of the source occurring with bunch refilling during a complete shift of DAΦNE.

DAFNE-Light is the Synchrotron Radiation Facility at the INFN-Frascati National Laboratory (Rome, Italy). Three beamlines are operational, using in parasitic and dedicated mode the intense photon emission of DAFNE, a 0.51 GeV storage ring with a routinely circulating electron current higher than I Ampere. Two of these beam lines - the soft x-ray (DXR1) and UV (DXR2) - use one of the DAFNE wiggler magnets as synchrotron radiation source, while the third beamline SINBAD (Synchrotron Infrared Beamline At DAFNE) collects the radiation from a bending magnet. New XUV bending magnet beamlines are nowadays under construction and the low energy one (35-200 eV) will be ready for commissioning by the end of 2009. A presentation of the facility will be given together with some recent scientific results achieved at SINBAD and DXR1 beamlines.

At the Laboratori Nazionali di Frascati, a novel diagnostics experiment named 3+L (Time Resolved e Light), funded by the V National Scientific Committee of the Istituto Nazionale di Fisica Nucleare, has been set-up on one of the positron ring bending magnet to monitor in real time e+ bunch shape and behavior in DAΦNE lepton collider. The system represents a novel fast diagnostic instrument that allows monitoring of bunch-by-bunch and turn-by-turn positron infrared (IR) emission with the goal to improve the DAΦNE diagnostics. Indeed, the main aim is to identify and characterize both longitudinal and transverse bunch instabilities to understand better the limits to the DAΦNE performances in terms of positron beam current and collider luminosity. The front-end of the experiment consists of an ultra high vacuum (UHV) chamber where a gold-coated plane mirror deflects the radiation through a ZnSe window. In addition, a compact optical layout in air focuses the radiation on uncooled HgCdTe photodetectors used to measure the synchrotron radiation emission at mid-IR wavelengths. At present, all experimental installations of the project have been completed and a characterization of the radiation emitted by the positron beam is available. In this technical note we present the actual status of the experiment and a description of the experimental set-up. Moreover, wave optics simulations of the photon emission, measurements of the visible beam spot collected with a CCD camera and measurements of the IR optical power at the focus spot will be presented and discussed. Data in the time domain acquired with different fast IR photo-detectors from both electron and positron bunches at DAΦNE and at the Hefei synchrotron radiation facility from the electron beam will be also presented. Finally preliminary measurements obtained with a fast IR array detector will be presented.

Bunch-by-bunch longitudinal diagnostics is a key issue of modern accelerators. To face up this challenging demand, tests of mid-IR compact uncooled photoconductive HgCdTe detectors have been recently performed at DAFNE. Different devices were used to monitor the emission of e- bunches. The first experiments allowed recording of 2.7 ns long e- bunches with a FWHM of a single pulse of about 600 ps. These results address the possibility to improve diagnostics at DAFNE and to this purpose an exit port on a bending magnet of the positron ring has been set-up. An HV chamber, hosting a gold-coated plane mirror that collects and deflects the radiation through a ZnSe window, is the front-end of this port. After the window, a simple optical layout in air allows focusing IR radiation on different detectors. The instrumentation will allow comparison in the sub-ns time domain between the two rings and to identify and characterize bunch instabilities. Moreover, to improve performances tests of new photovoltaic detectors with sub-ns response times are in progress. We will briefly summarize the actual status of the 3+L experiment and will discuss future applications of fast IR photovoltaic detectors and the development of fast IR array detectors.

Real-time beam diagnostics is a key issue of accelerator operations and is certainly one of the most demanding aspects of modern storage rings and 4 generation radiation sources such as FEL’s. Compact and vacuum compatible mid-IR fast uncooled photo-detectors have been tested at DAΦNE to monitor single e bunches with a FWHM of 150-300 ps separated by 2.7 ns. These detectors appear suitable to set up a compact and low cost bunch-by-bunch longitudinal diagnostic device useful to improve the DAΦNE diagnostic. To this purpose a bending magnet synchrotron radiation (SR) front end on the e ring has been set-up with a HV chamber, a goldcoated plane mirror and an IR window. The system will allow collection of the SR light for tests of IR detectors and diagnostic of e bunches using a compact optical system installed in air after the IR window. Here we will present the DAΦNE source characteristics, the optical setup and the detector acquisition system that may allow to monitor, identify and characterize bunch instabilities and/or increase the DAΦNE current in the e ring.

Compact uncooled HgCdTe semiconductor detectors optimized in the mid-IR range have been used to record time resolved single bunch synchrotron radiation (SR) emissions from the DAΦNE electron ring (1). These IR devices allow a low cost bunch-by-bunch longitudinal diagnostics. Indeed, these detectors make possible to record a train of a few ns long bunches per turn. To the purpose of diagnostic a comparison with the light signals coming from the positron ring appears stimulating but at DAΦNE only two SR beamlines are operational on the electron ring. The lack of apertures in the shielding wall offers no easy alternatives for the emission from the e+ ring. To solve the problem, a compact SR port has been designed and is going to be implemented at DAΦNE where a HV chamber and remotely controlled mirrors will focus the positron light on IR detectors. The source characteristics have been simulated and the optical setup with the complete acquisition system will be described. After the installation and tests, a real time comparison between data collected with the two beams will be possible improving accelerator diagnostics and as a major tool to increase the stored currents in the e+ ring and possibly the collider luminosity.

We analyze the scattering of 480MeV positrons in bent crystal lattices carried out at the Beam Test Facility of the INFN – Laboratori Nazionali di Frascati. We observe experimentally that some particles follow the bending of the crystal lattice, presumably being guided by channeling phenomenon, and are deflected through the angles of about 10mrad over length of 1mm of silicon. This technique may lead to the use of channeling effect for steering of particle beams at the energies under 1GeV, aimed at the production of ultrastable beams of low emittance for medical and biological applications.

We observe positron bending by a crystal lattice, presumably being guided by a channeling phenomenon, deflecting the beam by about 10 milliradian over a length of 1 mm of silicon. This technique may lead to the use of the channeling effect for steering particle beams at energies below 1 GeV, for the purpose of producing beams of low emittance with enhanced stability for medical and biological applications.

Accelerator-based sources of hard-photon radiation are a rapidly developing field. Coherent radiation of a particle beam in an undulator is a popular choice. The crystalline undulators with periodically deformed crystallographic planes offer electromagnetic fields of the order of 1000 T and could provide a period L in the sub-millimeter range. In this way, a hundred-fold gain in the energy of emitted photons would be reached, as compared to a usual undulator. The first real construction of a crystal channeling undulator was recently proposed and realised by the present collaboration. After the sine-like deformation of crystal was proven in X-ray tests, four undulators were tested for channeling in a beam of 70-GeV protons. It was observed in the experiment that the crystal cross-section is efficiently channeling high energy particles, similarly to usual crystal deflectors. The experimentally established transparence for channeling of high energy particles allows one to start a direct experiment on photon production from a positron beam in the crystalline undulator. Details of commissioning of the experimental setup in the first run with 3 GeV positron beam are presented.

Nell’ambito del progetto CryoAlp è stato sviluppato e collaudato un sistema di movimentazione micrometrica a sei gradi di libertà progettato per esperimenti di microscopia e spettroscopia in alto vuoto. Le caratteristiche di questo sistema micrometrico, dimensioni compatte, ampio campo operativo unito ad alta precisione, possibilità di eseguire mappature di superfici con geometrie complesse, compatibilità con ambiente di alto vuoto, temperature di esercizio fino a -50 C, rendono questo sistema unico nel suo genere per esperimenti non convenzionali su campioni con superfici irregolari, in condizioni di temperatura controllata in vuoto. In the framework of the CryoAlp project we developed and tested a micro-positioning system with six degrees of freedom devoted to spectromicroscopy experiments in a highvacuum regime. The characteristics of this micrometric system: compactness, wide operating range combined to a high precision, capability to perform mapping of sample surfaces with complex geometries, compatibility with high-vacuum, operating temperatures down to -50 C make this system a unique system, tailored to specific requirements of non conventional experiments, such as those looking at samples with non homogeneous surfaces, in a controlled temperature regime in vacuum.

Three synchrotron radiation beam lines have been built on DAPhiNE, the Frascati electron-positron accelerator. It is possible to monitor and control all the elements on the beam lines using a modular network distributed I/O system by National Instruments (FieldPoint) with BridgeVIEW/LabVIEW programs. Two of these beam lines have radiation safety problems solved by two independent and redundant systems, using mechanical switches, and S7-200 PLC's by Siemens. In this article our solution will be described in details.

The optical behavior of point defects created by low energy electron beams (3 divided by 12 keV) in multilayer LiF:NaF and in pure LiF and NaF films, grown by physical evaporation on amorphous substrates, has been investigated. Their visible photoluminescence has been measured at room (RT) and liquid nitrogen temperatures (LNT) by excitation with an Ar+ laser. Controlling the deposition parameters and the irradiation conditions in order to influence the color centers spatial distribution, it is possible to obtain green-yellow-red photoluminescent materials with predesigned optical features.

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.

In this work we report the visible and infrared emissions of the color centers created in bilayer LiF:KCl thin films, obtained by pumping them with appropriate Ar+ and Ti:Sapphire laser lines, The large concentration of color centers induced by low-energy electron irradiation in a thin dielectric layer of controlled depth allows to investigate the spectroscopic properties of point defects which cannot be found in mixed crystals.

Photoluminescence (PL) emission spectra have been carried out on a partially relaxed SiSi1−xGexSi quantum well (QW) grown by solid-source MBE at a nominal composition of x = 17%. The results are discussed in terms of the film morphology, as derived from structural techniques (SEM, RHEED, RBS and XRD), especially as regards the presence of a high density of dots-like 3D structures. PL spectra show an intense broad band, attributed to excitonic recombinations at interstitial plateletes in the dots, with smaller XNP and XTO excitonic lines due to phonon-resolved interband transitions originated from the strained epitaxyal layer grown before the dot formation.

The formation of laser active color centers in LiF films irradiated with low energy electrons has been investigated as a function of the film growth parameters, Spectroscopic measurements have shown that the formation efficiency of F-aggregate centers is higher in polycrystalline films than in single crystals and can depend on the film growth conditions, which in turn influence the surface to volume ratio, the void presence and the preferred orientation of the crystallites.