Final report. Part I, experimental equipment

Includes bibliographical references (page 20).August 1956.CER No. 56 ACS 12.The experimental equipment used in an investigation of turbulent diffusion of momentum and heat from a smooth, plane boundary with zero pressure gradient is described in Part I of this Final Report. A 10 ft long, 6 ft wide heated boundary, maintained at uniform temperature, formed part of the floor of the 6-ft square test section of a recirculating, low-velocity wind tunnel. Hot-wire anemometers were used for the measurement of mean velocities, intensities of turbulence, and turbulent shearing stress distributions in the momentum and the thermal boundary layers. Mean temperatures were measured with copper-constantan thermocouples. For the measurement of temperature fluctuations, a constant-temperature resistance thermometer was developed and used. The heat transferred from the boundary was determined from the electrical power input to the heater strips.The research reported in this document has been sponsored by the Geophysics Research Directorate of the Air Force Cambridge Research Center, Air Research and Development Command, under contract AF19(604)-421

Tests on Models of Nuclear Reactor Elements - Head Losses in Core Sub-Assemblies

Losses have been determined for flow through models of various proposed core sub-assemblies as part of a study of the elements of a nuclear reactor. Six core sections and two? axial blanket sub-assemblies have been compared on the basis of drop in piezometric. head or pressure drop. The core sub-assemblies are composed of an entrance nozzle, a lower axial blanket section, the core section, an upper axial blanket section, and a short section for the handling lug. The four parts of the sub-assembly other than the core section are designated as the axial blanket sub-assembly. In each core section there are 144 rods within a container which has a square cross-section. The primary differences between one core section and another are the means qf supporting and spacing the rods. Bars or wires wrapped in spirals around the rods were used as well as a series of grids made up of wires and supported at the four corners. Also, in one core an, inner wall was used to provide an annular flow passage which helps to reduce the difference in temperature at the inner and outer walls of the core. The two axial blanket sub-assemblies tested are similar except ?that the second model is characterized by more gradual transitions in changes of cross section. Other parts of this study of the elements of a nuclear reactor have been described in two previous reports dealing with head losses in complete blanket subassemblies and with diffusion studies

Tests on Models of Nuclear Reactor Elements - Head Losses in Core Sub-Assemblies

Losses have been determined for flow through models of various proposed core sub-assemblies as part of a study of the elements of a nuclear reactor. Six core sections and two? axial blanket sub-assemblies have been compared on the basis of drop in piezometric. head or pressure drop. The core sub-assemblies are composed of an entrance nozzle, a lower axial blanket section, the core section, an upper axial blanket section, and a short section for the handling lug. The four parts of the sub-assembly other than the core section are designated as the axial blanket sub-assembly. In each core section there are 144 rods within a container which has a square cross-section. The primary differences between one core section and another are the means qf supporting and spacing the rods. Bars or wires wrapped in spirals around the rods were used as well as a series of grids made up of wires and supported at the four corners. Also, in one core an, inner wall was used to provide an annular flow passage which helps to reduce the difference in temperature at the inner and outer walls of the core. The two axial blanket sub-assemblies tested are similar except ?that the second model is characterized by more gradual transitions in changes of cross section. Other parts of this study of the elements of a nuclear reactor have been described in two previous reports dealing with head losses in complete blanket subassemblies and with diffusion studies

Measurement of Angular Distributions and R= sigma_L/sigma_T in Diffractive Electroproduction of rho^0 Mesons

Production and decay angular distributions were extracted from measurements of exclusive electroproduction of the rho^0(770) meson over a range in the virtual photon negative four-momentum squared 0.5< Q^2 <4 GeV^2 and the photon-nucleon invariant mass range 3.8< W <6.5 GeV. The experiment was performed with the HERMES spectrometer, using a longitudinally polarized positron beam and a ^3He gas target internal to the HERA e^{+-} storage ring. The event sample combines rho^0 mesons produced incoherently off individual nucleons and coherently off the nucleus as a whole. The distributions in one production angle and two angles describing the rho^0 -> pi+ pi- decay yielded measurements of eight elements of the spin-density matrix, including one that had not been measured before. The results are consistent with the dominance of helicity-conserving amplitudes and natural parity exchange. The improved precision achieved at 47 GeV, reveals evidence for an energy dependence in the ratio R of the longitudinal to transverse cross sections at constant Q^2.Comment: 15 pages, 15 embedded figures, LaTeX for SVJour(epj) document class Revision: Fig. 15 corrected, recent data added to Figs. 10,12,14,15; minor changes to tex

Inclusive Electron Scattering from Nuclei at x≃1x \simeq 1

The inclusive A(e,e') cross section for $x \simeq 1$ was measured on $^2$H, C, Fe, and Au for momentum transfers $Q^2$ from 1-7 (GeV/c)$^2$. The scaling behavior of the data was examined in the region of transition from y-scaling to x-scaling. Throughout this transitional region, the data exhibit $\xi$-scaling, reminiscent of the Bloom-Gilman duality seen in free nucleon scattering.Comment: 4 pages, RevTeX; 4 figures (postscript in .tar.Z file

A-dependence of nuclear transparency in quasielastic A(e,e'p) at high Q^2

The A-dependence of the quasielastic A(e,e'p) reaction has been studied at SLAC with H-2, C, Fe, and Au nuclei at momentum transfers Q^2 = 1, 3, 5, and 6.8 (GeV/c)^2. We extract the nuclear transparency T(A,Q^2), a measure of the average probability that the struck proton escapes from the nucleus A without interaction. Several calculations predict a significant increase in T with momentum transfer, a phenomenon known as Color Transparency. No significant rise within errors is seen for any of the nuclei studied.Comment: 5 pages incl. 2 figures, Caltech preprint OAP-73

Beam-Induced Nuclear Depolarisation in a Gaseous Polarised Hydrogen Target

Spin-polarised atomic hydrogen is used as a gaseous polarised proton target in high energy and nuclear physics experiments operating with internal beams in storage rings. When such beams are intense and bunched, this type of target can be depolarised by a resonant interaction with the transient magnetic field generated by the beam bunches. This effect has been studied with the HERA positron beam in the HERMES experiment at DESY. Resonances have been observed and a simple analytic model has been used to explain their shape and position. Operating conditions for the experiment have been found where there is no significant target depolarisation due to this effect.Comment: REVTEX, 6 pages, 5 figure

Measurement of the Proton Spin Structure Function g1p with a Pure Hydrogen Target

A measurement of the proton spin structure function g1p(x,Q^2) in deep-inelastic scattering is presented. The data were taken with the 27.6 GeV longitudinally polarised positron beam at HERA incident on a longitudinally polarised pure hydrogen gas target internal to the storage ring. The kinematic range is 0.021<x<0.85 and 0.8 GeV^2<Q^2<20 GeV^2. The integral Int_{0.021}^{0.85} g1p(x)dx evaluated at Q0^2 of 2.5 GeV^2 is 0.122+/-0.003(stat.)+/-0.010(syst.).Comment: 7 pages, 3 figures, 1 table, RevTeX late

The Flavor Asymmetry of the Light Quark Sea from Semi-inclusive Deep-inelastic Scattering

The flavor asymmetry of the light quark sea of the nucleon is determined in the kinematic range 0.02<x<0.3 and 1 GeV^2<Q^2<10 GeV^2, for the first time from semi-inclusive deep-inelastic scattering. The quantity (dbar(x)-ubar(x))/(u(x)-d(x)) is derived from a relationship between the yields of positive and negative pions from unpolarized hydrogen and deuterium targets. The flavor asymmetry dbar-ubar is found to be non-zero and x dependent, showing an excess of dbar over ubar quarks in the proton.Comment: 7 Pages, 2 figures, RevTeX format; slight revision in text, small change in extraction of dbar-ubar and comparison with a high q2 parameterizatio

Observation of a Single-Spin Azimuthal Asymmetry in Semi-Inclusive Pion Electro-Production

Single-spin asymmetries for semi-inclusive pion production in deep-inelastic scattering have been measured for the first time. A significant target-spin asymmetry of the distribution in the azimuthal angle phi of the pion relative to the lepton scattering plane was observed for pi+ electro-production on a longitudinally polarized hydrogen target. The corresponding analyzing power in the sin(phi) moment of the cross section is 0.022 +/- 0.005 +/- 0.003. This result can be interpreted as the effect of terms in the cross section involving chiral-odd spin distribution functions in combination with a time-reversal-odd fragmentation function that is sensitive to the transverse polarization of the fragmenting quark.Comment: 5 pages of RevTex, 3 ps figures, 2 table