Development of a broadband laser in the UV region

A frequency comb in the UV region with a bandwidth greater than 100 MHz is generated by successive frequency shifts of a single mode laser by an acousto-optic modulator coupled to a passive ring cavity. The obtained spectrum is particularly suitable for laser cooling when a large velocity capture range is required as in the case, for example, of ions confined in a storage ring. This revised version was published online in August 2006 with corrections to the Cover Date.     

Ion beam crystallization

After the successful exploitation of electron cooling in several heavy ion storage rings the possibility of generating crystalline ion beams gained the interest of particle accelerator physicists. New cooling methods, such as laser cooling, give further opportunity to reach ultra cold system of particles necessary for the state transition to the crystalline configuration. Crystalline beams will give insight into a completely new research field, reaching higher standards in precision measurements and techniques. The applicative potentialities of crystalline beams justify a careful investigation on this subject. The conceptual design of a low-energy heavy-ion storage ring, called CRYSTAL, proposed for the experimental demonstration of crystalline beams at Legnaro LNL is presented. This revised version was published online in August 2006 with corrections to the Cover Date.     

Quality management of preanalytical phase: impact of lithium heparin vacuum tubes changes on clinical chemistry tests

The validation process is essential in accredited laboratory medicine, but is rarely regarded as an issue in the preanalytical management. The aim of this study was to validate five kinds of lithium heparin vacuum tubes for routine clinical chemistry laboratory testing. Blood specimens from 100 volunteers in five different plasma vacuum tubes (Tube I: VACUETTE^®, Tube II: LABOR IMPORT^®, Tube III: S-Monovette^®, Tube IV: PST^® and Tube V: PST II^®) were collected by a single expert phlebotomist. The routine clinical chemistry tests were performed on a Cobas^® 6000 <c501> module. The significance of the differences between samples was statistically assessed at p < 0.005. The biases from the different tubes were compared with the current desirable quality specifications. Basically, significant differences could be confirmed by RM ANOVA for the results of the clinical chemistry tests on the following components: glucose, urea, creatinine, alkaline phosphatase, amylase, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, total bilirubin, phosphate, Ca, Mg, Fe and K. Clinically significant variations as compared with the current desirable quality specifications were found for glucose, creatinine, amylase, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, Ca, Mg and K. In conclusion, our results do not support arbitrary interchange among brands of plasma vacuum tubes. Future investigations are needed to understand the reasons of these observations; in the meantime, we suggest that laboratory managers standardize the procedures and frequently evaluate the quality of in vitro diagnostic devices.     

Experimental analysis and modeling of self-standing curved crystals for focusing of X-rays

Novel applications can be attained through the usage of bent crystals as optical components for the challenge of focusing hard X and γ rays by Bragg diffraction. Nuclear astrophysics, nuclear medicine and homeland security would highly benefit from such optics, because they all share the same need for efficient X- and γ-ray focusing systems. With this aim, self-standing bent silicon crystals have been reproducibly attained thanks to the method of surface grooving. An extensive study has been worked out to understand the process of substrate deformation. By adjusting experimental parameters, very good control of the curvature is afforded. Process of deformation has been modeled in terms of irreversible compression occurring in the material close to the grooves. The underlying silicon was treated as an anisotropic medium elastically reacting to the state of stress provided by the grooves. Comparison between experimental results and theoretical expectations was satisfactorily achieved.     

PRESS-MAG-O: A new facility to probe materials and phenomena under extreme conditions

In the recent years, several experiments performed under high magnetic fields (HMFs), at high pressure (HP) and/or at low temperature (LT) have led to spectacular discoveries in condensed matter. In many new systems, although challenging, it is strategic to perform a magneto-optical analysis, to investigate the phonon behavior in the far infrared (IR) domain. By combining HMF and HP in a wide temperature (T) range to perform concurrently IR magneto-optics and ac-magneto-dynamic experiments, it will be possible to achieve unique information on systems and/or new phenomena, almost impossible to obtain with standard spectroscopic methods. Here we present PRESS-MAG-O, a new facility under construction that will perform HP experiments under HMF in a wide T range. The system is expected to be operational by the end of 2008 and will be tested at SINBAD, the IR synchrotron radiation beamline operational since 2001 at DAΦNE (Double Annular Φ-factory for Nice Experiments), the storage ring of the INFN Frascati National Laboratory (LNF). While for IR experiments an interferometer will be used, for the magneto-dynamic experiments a SQUID magnetometer in the 10 Hz-2 KHz frequency range will be utilized. HP will be applied to samples by a Cu-Be diamond anvil cell (DAC), so that the device will be able to collect FTIR spectra and high harmonic ac susceptibility data in a dc magnetic field up to 8 T and to about 20 GPa in a wide temperature range (4.2-200 K).     

The magnetic phase in 2-2-1-2 superconducting materials

Three related aspects of the magnetic phase diagram are presented here: the first deals with the disruption of the antiferromagnetic order in the electron rich phase obtained by Ce doping, the second concern the role of Bi planes as a sink-buffer of carriers, the third focuses the magnetization vs. temperature curves in a variety of different bilayer materials as seen by the muons and discusses the “anomalous” behaviour in relation to theoretical predictions and neutron scattering data.     

First demonstration of “white-light” laser cooling of a stored ion beam

“White-light” cooling of an ion beam confined in a storage ring has been demonstrated at Test Storage Ring in Heidelberg. Measurements aimed at comparing “white-light” with single-mode laser cooling show that “white-light” cooling gives lower temperatures at higher ion densities both in a coasting and in a bunched beam. This revised version was published online in July 2006 with corrections to the Cover Date.     

Steering of Sub-GeV electrons by ultrashort Si and Ge bent crystals

We report the observation of the steering of 855 MeV electrons by bent silicon and germanium crystals at the MAinzer MIkrotron. Crystals with 15 \(\upmu \)m of length, bent along (111) planes, were exploited to investigate orientational coherent effects. By using a piezo-actuated mechanical holder, which allowed to remotely change the crystal curvature, it was possible to study the steering capability of planar channeling and volume reflection vs. the curvature radius and the atomic number, Z. For silicon, the channeling efficiency exceeds 35%, a record for negatively charged particles. This was possible due to the realization of a crystal with a thickness of the order of the dechanneling length. On the other hand, for germanium the efficiency is slightly below 10% due to the stronger contribution of multiple scattering for a higher-Z material. Nevertheless this is the first evidence of negative beam steering by planar channeling in a Ge crystal. Having determined for the first time the dechanneling length, one may design a Ge crystal based on such knowledge providing nearly the same channeling efficiency of silicon. The presented results are relevant for crystal-based beam manipulation as well as for the generation of e.m. radiation in bent and periodically bent crystals.     

Volume reflection of a proton beam in a bent crystal

Volume reflection predicted in the mid-1980s by Taratin and Vorobiev has been observed for the first time in the interactions of a 70 GeV proton beam with a short bent crystal. Incident protons deviate from convex atomic planes in the bulk of the crystal as a result of coherent interaction with bent lattice around the tangency point of particle trajectory with a curved atomic plane. The deflection angle 2theta(R) was found to be (39.5+/-2.0) microrad, or (1.65+/-0.08)theta(c) in terms of the critical angle for channeling. The process has a large probability with respect to channeling and takes place in the angular range equal to the bend angle of atomic planes. It could possibly open new fields of application of crystals in high-energy particle beam optics.