Gas bremsstrahlung from the phi-Factory presently under construction at the INFN Frascati National Laboratories (Italy) has been studied using the Monte Carlo FLUKA code. Photon spectrum and quantitative estimates of fluence rates and tissue absorbed dose rates are given. On the basis of the obtained results the precautions to be taken are discussed.

The absolute bremsstrahlung intensity generated by the interaction of the electron beam of the Adone storage ring of LNF has been measured as a function of angle and distance from the emitting straight section. Absorbed doses have been measured at various distances from the straight section by means of thermoluminescent dosimeters for a 1.5 GeV electron beam. The experiment has been simulated using the most recent version of the FLUKA code which includes a very accurate treatment of bremsstrahlung. In spite of the considerable uncertainties on the experimental value of the pressure, it has been found that the computed results are in satisfactory agreement with the results of the measurements. The experiment provided also evidence for the angular distribution of the bremsstrahlung intensity at energies in excess of 1 GeV.

Following experiments performed with deuterided high-temperature superconductors (HTSCs) at the underground Gran Sasso Laboratory, the capacity of these materials to absorb deuterium and the role played by nonequilibrium conditions in neutron burst emissions in the framework of cold fusion have been determined.Taking into account that HTSC materials such as Y1Ba2Cu3O7-delta (YBCO) are able to absorb deuterium without destroying the crystalline structure, deuterated YBCO pellets were placed in a neutron radiation field, and thermal cycles were operated. In this double nonequilibrium condition, neutron rate enhancement was sought by selecting "time-correlated" burst-like events. The pellets and high-pressure D2 gas were enclosed in a stainless steel vessel, and thermal cycles (300 to 77 to 300 K) were performed, moreover, for comparison, background and blank runs were performed. A specific acquisition system, able to detect multiple neutron signals in defined time windows, was set up.One thermal cycle run showed a large increase (seven times more, corresponding to >30 standard deviations) of time-correlated events with respect to the blanks. In another run, although no relevant mean value increase in events was detected, one interesting multiple (triple) neutron signal occurred at a temperature (approximately 95 K) close to the transition from superconducting to the normal state. These multiple events were sporadic (detected twice during four thermal cycles lasting approximately 3 h), although the probability that these events were simulated by the background was quite low (one incident expected in 80 h). Similar runs produced no relevant values.Another experiment, at constant temperature (300 K), characterized by a heavy D2 gas refill, showed both some increase in time-correlated events and a few triple neutron signals.

In order to analyze the diamagnetic properties of weakly coupled structures in high T(c) ceramic superconductors, the Josephson junction array model is used. We suppose that the coupling is strong enough to allow magnetic flux trapping inside non superconducting regions surrounded by superconducting loops closed by Josephson junctions. We remark that the presence of currents flowing through the junctions has to be taken explicity into account in the Hamiltonian. This description leads to a creep model of the Josephson junction array. Indeed we have: 1) pinning centers generated by non superconducting regions into the loops, 2) pinning potentials determined by fluxon motion barriers due to the Josephson junctions, 3) absence of degeneracy of the states corresponding to a different number of fluxons in the loops, 4) a reduction of the barrier height due to measuring currents or to diamagnetic shielding currents. The last effect is equivalent to the Lorentz force effect in type-II superconductors. In this way we believe that this picture deeply modifies the usual superconducting glass model.

Several experiments were performed at the INFN Underground Gran Sasso Laboratory (Italy) in order to detect nuclear signals, if any, coming from deuterated materials in the framework of so called ‘‘Cold Fusion.’’ We followed three, quite different, lines of experimental researches.In the first set of experiments we used electrolytic solutions of heavy water and 0.1 M LiOH with some addition of gaseous CO2, using as cathode a rod of pure Pd or Ti alloys and as anode a Pt net. We detected several intense bursts of gamma rays, lasting up to 15 minutes of duration time, with energy less than 300 KeV.In the second set of experiments we used pellets of sintered High Temperature Superconductors (HTSC) that underwent deuteration by high pressure (∼30 Bar) and temperature (∼370 K) gas loading procedure. The deuterated samples were several times cycled down to liquid nitrogen temperature and we detected by two independent 3He moderated neutron detectors (1.2% total efficiency), sporadic emission of signals mainly during these thermal cycles.Later on similar tests were performed independently by S. E. Jones and collaborators (Provo Univ., Utah) in a deep underground mine and a very intense and short neutron burst was detected by 16 independent 3He moderated neutron detectors (32% efficiency).In the third set of experiments some additional tests were performed using a low activity Am‐Be neutron source, in order to study possible phenomena of enhanced neutron emission by radiation stimulation in these HTSC deuterated compounds. We detected excess counts of 2 static standard deviations, pointing to increased D‐D cross section due to the effect of ceramic lattice.

In this paper we analyze the weakly coupled structure of high Tc superconducting granular samples in terms of a Josephson junctions network. We start from the well known results on superconducting loops closed by Josephson junctions, and show that the energy barrier for entrapping or detrapping flux quanta is essentially determined by the shielding currents crossing the junctions which remove the states degeneration. This effect corresponds to the absence of degeneration of the thermodynamic potential as a function of different number of flux quanta trapped in the superconducting loops. Following this approach we remark that the superconducting glass model neglects the effects of shielding currents and may be a poor approximation. On the contrary a correct description of superconducting granular systems leads to a model very similar to the usual flux creep model.

We analyse the diamagnetic behaviour of high Tc superconducting granular samples by mean of an equivalent network of Josephson junctions and inductances. The range of validity of the current approaches is determined by considering the complete expression for the Gibbs thermodynamic potential and by identifying two characteristic parameters β1 and β2 for these systems. A graphical representation of the validity limits of various current approaches and in particular of the superconducting glass model is given in a β1-β2 plane.

Several experiments were performed at the Gran Sasso Laboratory on an 0.8-cm-diam × 5-cm-long, hyperpure, high-temperature vacuum-annealed palladium rod used as a cathode for electrolytic infusion of D2O and 0.1 M LiOH with regular additions of gaseous CO2 at a current density of 60 mA/cm2. In the very low background radiation environment, several gamma bursts lasting up to 15 min were detected whose intensity, in terms of cold fusion, was > 10−20 fusion/(deuteron pair · s). Under normal background conditions, none of these burst signals would have been detected with statistical significance. The shape and intensity of these signals are quite similar to those detected previously.

Sintered samples of Y1Ba2Cu3O7-δ prepared with a modified citrate pyrolysis and annealed in an ozone atmosphere are tested with a.c. screening current in a geometrical configuration able to detect a true bulk superconductivity. A picture of the main features of diamagnetic behaviour of sintered high Tc superconductors is given to explain the a.c. susceptibility measurements in such materials. Comparisons among samples respectively annealed with and without ozone atmosphere have been performed as a function of the amplitude of the a.c. magnetic field. At small fields ozone samples just 2K below the superconducting transition temperature have a complete shielding while, with the same a.c. magnetic field, oxygen samples show the complete shielding at lower temperature. For samples with simple geometrical shape the absolute reference, corresponding to the 100 % shielding is obtained by using Nb or Pb superconducting samples with identical shapes. In the absence of an absolute reference for arbitrary shapes, the complete diamagnetic shielding can be inferred by the absence of the frequency dependence in the a.c. susceptibility. Such analysis clearly shows the better quality of the ozone samples.

A.C. low frequency susceptibility measurements, using the “inductance variation” method, have been performed on sintered YBCO pellets fabricated using a new process. This process is based on a modified citrate pyrolysis method and on the use of ozone in all the thermal treatments. The diamagnetic behavior of this material have been studied as a function of the temperature changing both the amplitude of the a.c. magnetic field (0.2, 2, 8 Gauss) and the test frequency (120, 1K, 10K Hertz). At 0.2 Gauss the width (10%-90%) of the diamagnetic transition of the ozone samples is as low as 2K with a diamagnetic Tc of 98K. This width value obviously enlarges with the increase of the applied field: at 2 Gauss, with almost the same Tc, δTc increases up to 6K. The behaviour at 8 Gauss clearly shows the contributions to the diamagnetic signal due both to the intergrain Jj coupling and to the isolated grains. The ozone annealed samples are compared with both oxygen annealed samples and samples made following the conventional calcination - retiring procedure: the last two show larger transition widths and a lower stability against water.

YBCO sintered samples have been fabricated by the citrate pyrolysis method. The annealing, with the usual thermal processes, but using a mixture of oxygen and ozone, generates large microcrystals. Samples fabricated with this process have been characterized by measuring the a.c. susceptibility. Low field measures show a very narrow transition width, while high field measures performed both at 50 and 100 Gauss denote the higher strength of the intergranular junctions in the ozone made samples.

The charge response of streamer tubes has been measured as a function of ionization power by exposure to relativistic ions. The results are discussed in view of the use of streamer tubes in the search for magnetic monopoles.