[en] The feasibility of spatial and temporal power density flattening in fusion-fission hybrid reactors was investigated by varying the concentration of /sup 239/Pu within a set of zones in the fission region and by examining two different fuel management schemes. Blanket designs with no /sup 239/Pu typically had a spatial maximum-to-average power density ratio of approximately 2.5, but this value was reduced to between 1.26 and 1.67, depending on the design and fuel management scheme selected. Unfortunately, however, significant impact occurs only with relatively high fissile concentrations, with the outer zones approaching equilibrium values. Thus, either an impractically large fissile inventory for startup or long operating histories would be required. 9 refs

[en] The cross-section for phi meson photoproduction on the proton has been measured at a photon energy E_gamma = 3.6 GeV up to a four-momentum transfer -t = 4 GeV². A measurement of the differential cross-section at such high transfers, down to 100 pb/GeV², was only made possible thanks to the combination of the 100% duty cycle of CEBAF and the use of the large acceptance detector CLAS. At low four-momentum transfer, the differential cross-section is in agreement with previous measurements and is well accounted for by the exchange of the Pomeron. At large four-momentum transfer, above -t = 1 GeV², no previous data exist, and our results support a model where the Pomeron is resolved into its simplest component, two gluons. Taking into account the coupling of these gluons to any quark in the proton and the phi reproduces quite well the dependence in t of our cross-sections.

[en] The feasibility of spatial and temporal power density flattening in fusion-fission hybrid reactors was investigated by varying the concentration of ²³⁹Pu within a set of zones in the fission region and by examining two different fuel management schemes. Blanket designs with no ²³⁹Pu typically had a spatial maximum-to-average power density ratio of about 2.5, but this value was reduced to between 1.26 and 1.67, depending on the design and fuel management scheme selected. Unfortunately, however, significant impact occurs only with relatively high fissile concentrations, with the outer zones approaching equilibrium values. Thus, either an impractically large fissile inventory for startup or long operating histories would be required

[en] Measurements on the Belousov-Zhabotinskii reaction in a stirred flow reactor reveal, beyond a period-doubling cascade, a sequence of periodic states different from the ''U (universal) sequence'' found in recent experiments on diverse systems. Particular periodic states occur in three different parameter ranges rather than one range as in the U sequence. However, the order of periodic states found here is in accord with a one-dimensional single-parameter map constructed from the laboratory data

[en] This paper reports on results from various mitigation approaches to the skyshine interference problem as it affects radiation detection systems

[en] Superconducting electronics and spectral-spatial holography have the potential to revolutionize digital communications, but must operate at cryogenic temperatures, near 4 K. Liquid helium is undesirable for military missions due to logistics and scarcity, and commercial low temperature cryocoolers are unable to meet size, weight, power, and environmental requirements for many missions. To address this need, Creare is developing a reverse turbo-Brayton cryocooler that provides refrigeration at 4.2 K and rejects heat at 77 K to an upper-stage cryocooler or through boil-off of liquid nitrogen. The cooling system is predicted to reduce size, weight, and input power by at least an order of magnitude as compared to the current state-of-the-art 4.2 K cryocooler. For systems utilizing nitrogen boil-off, the boil-off rate is reasonable. This paper reviews the design of the cryocooler, the key components, and component test results. (paper)

[en] During the 1997/98 luminosity run of the Stanford Linear Collider (SLC) two novel RF-based detectors were brought into operation, in order to monitor the interaction-point (IP) bunch lengths and fluctuations in the relative arrival time of the two colliding beams. Both bunch length and timing can strongly affect the SLC luminosity and had not been monitored in previous years. The two new detectors utilize a broad-band microwave signal, which is excited by the beam through a ceramic gap in the final-focus beam pipe and transported outside of the beamline vault by a 160-ft long X-Band waveguide. We describe the estimated luminosity reduction due to bunch-length drift and IP timing fluctuation, the monitor layout, the expected responses and signal levels, calibration measurements, and beam observations

[en] X-band accelerator structures meeting the Next Linear Collider (NLC) design requirements have been found to suffer damage due to Radio Frequency (RF) breakdown when processed to high gradients [F. Le Pimpec, et al., in: LINAC 2002, Korea, SLAC-PUB-9526, 2002 [1]]. Improved understanding of these breakdown events is desirable for the development of structure designs, fabrication procedures, and processing techniques that minimize structure damage. Acoustic sensors attached to an accelerator structure can detect both normal and breakdown RF pulses [M. Gangeluk, et al., Acoustic monitoring system of RF breakdowns inside the electrodynamics structure at Kurchatov SR source accelerator, in: EPAC, P.1986, 1994 [2]]. Using an array of acoustic sensors, we have been able to pinpoint both the cell and azimuth location of individual breakdown events. This permits studies of breakdown in time and in space, so that underlying causes can be determined. This technique provided a significant understanding of breakdown in the structure input coupler

[en] ARIADNE is a 1-ton (330 kg fiducial mass) dual-phase liquid argon (LAr) time projection chamber (TPC) featuring a novel optical readout. Four electron-multiplying charge-coupled device (EMCCD) cameras are mounted externally, and these capture the secondary scintillation light produced in the holes of a thick electron gas multiplier (THGEM) . Track reconstruction using this novel readout approach is demonstrated. Optical readout has the potential to be a cost effective alternative to charge readout in future LArTPCs. In this paper, the technical design of the detector is detailed. Results of mixed particle detection using a secondary beam from the CERN PS (representing the first ever optical images of argon interactions in a dual-phase LArTPC at a beamline) and cosmic muon detection at the University of Liverpool are also presented.

[en] Radiative blast waves were created by irradiating a krypton cluster source from a supersonic jet with a high intensity femtosecond laser pulse. It was found that the radiation from the shock surface is absorbed in the optically thick upstream medium creating a radiative heat wave that travels supersonically ahead of the main shock. As the blast wave propagates into the heated medium, it slows and loses energy, and the radiative heat wave also slows down. When the radiative heat wave slows down to the transonic regime, a secondary shock in the ionization precursor is produced. This paper presents experimental data characterizing both the initial and secondary shocks and numerical simulations to analyze the double-shock dynamics