16 research outputs found

    Liquid Hydrogen Target Experience at SLAC

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    Liquid hydrogen targets have played a vital role in the physics program at SLAC for the past 40 years. These targets have ranged from small "beer can" targets to the 1.5 m long E158 target that was capable of absorbing up to 800 W without any significant density changes. Successful use of these targets has required the development of thin-wall designs, liquid hydrogen pumps, remote positioning and alignment systems, safety systems, control and data acquisition systems, cryogenic cooling circuits and heat exchangers. Detailed operating procedures have been created to ensure safety and operational reliability.This paper surveys the evolution of liquid hydrogen targets at SLAC and discusses advances in several of the enabling technologies that made these targets possible

    Esquemas de conducta, procesos de pensamiento, actos de habla

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    La investigaci贸n psicol贸gica de los procesos cognitivos y su configuraci贸n especifica a partir del lenguaje se encuentra en el l铆mite de la pregunta filos贸fica acerca de la relaci贸n lenguaje-pensamiento-realidad y de la preocupaci贸n epistemol贸gica por esclarecer la interconexi贸n de las teorias cient铆ficas y los datos observacionales o experimentales, la l贸gica interna del proceso cient铆fic0 y las posibilidades de elaboraci贸n de una heur铆stica que facilite el establecimiento de patrones de descubrimiento. Aunque conviene delimitar los distintos campos, la perspectiva global de esta problem谩tica permite fecundar nuevos proyectos de estudio. La Escuela de W眉rzburg nos ofrece un buen ejemplo de investigaciones diversas sobre estos temas, en las que se procede unas veces intensivamente (de forma muy especifica) y otras veces de manera extensiva. En el articulo se da una informaci贸n general de 10s principales autores de la Escuela, se entra en la consideraci贸n de las tesis centrales que K眉lpe expuso en su libro Die Realisierung y se destaca la importancia concedida a 10s trabajos de Karl B眉hler por parte de te贸ricos de la ciencia como Popper y Hans Albert

    Scaling of thermoacoustic refrigerators

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    The possibility of scaling-down thermoacoustic refrigerators is theor. investigated. Standing-wave systems are considered as well as traveling-wave. In the former case, a ref. system is taken that consists of a resonator tube (50 cm) with a closed end and a PVC stack (length 5 cm). Helium is used at a mean pressure of 10 bar and an amplitude of 1 bar. The resulting operating frequency is 1 kHz. The variation of the performance of the refrigerator when scaled down in size is computed under the prerequisites that the temp. drop over the stack or the energy flux or its d. are fixed. The anal. results show that there is a limitation in scaling-down a standing-wave thermoacoustic refrigerator due to heat conduction. Similar scaling trends are considered in traveling-wave refrigerators. The traveling-wave ref. system consists of a feedback inertance tube of 0.567 m long, inside diam. 78 mm, a compliance vol. of 2830 cm3 and a 24 cm thermal buffer tube. The regenerator is sandwiched between two heat exchangers. The system is operated at 125 Hz and filled with 30 bar helium gas. Again, the thermal conductance forms a practical limitation in down-scaling

    Availability and Failure Modes of the BaBar Superconducting Solenoid

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    Wall shape optimization for a thermosyphon loop featuring corrugated pipes

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    In the present paper we address the problem of optimal wall-shape design of a single phase laminar thermosyphon loop. The model takes the buoyancy forces into account via the Boussinesq approximation. We focus our study on showing the effects of wall shape on the flow and on the temperature inside the thermosyphon. To this extend we determine the dependency of the flow rate and the increase in temperature, on the geometrical characteristics of the loop. The geometry considered is a set of axially symmetric corrugated pipes described by a set of parameters; namely the pipe inner radius, the period of the corrugation, the amplitude of the corrugation, and the ratio of expansion and contraction regions of a period of the pipe. The governing equations are solved using the Finite Element Method, in combination with an adaptive mesh refinement technique in order to capture the effects of wall shape. We characterize the effects of the amplitude and of the ratio of expansion and contraction. In particular we show that for a given fixed amplitude it is possible to find an optimal ratio of expansion and contraction that minimizes the temperature inside the thermosyphon. The results show that by adequately choosing the design parameters, the performance of the thermosyphon loop can be improved
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