On the influence of the cosmological constant on gravitational lensing in small systems

The cosmological constant Lambda affects gravitational lensing phenomena. The contribution of Lambda to the observable angular positions of multiple images and to their amplification and time delay is here computed through a study in the weak deflection limit of the equations of motion in the Schwarzschild-de Sitter metric. Due to Lambda the unresolved images are slightly demagnified, the radius of the Einstein ring decreases and the time delay increases. The effect is however negligible for near lenses. In the case of null cosmological constant, we provide some updated results on lensing by a Schwarzschild black hole.Comment: 8 pages, 1 figure; v2: extended discussion on the lens equation, references added, results unchanged, in press on PR

THE PRELIMINARY CHOICE OF DESIGN PARAMETERS FOR NEUTRON CHOPPERS

Some of the factors affecting the counting rate achieved by a neutron chopper spectrometer are investigated. It is shown that in a chopper of optimum design the counting rate per channel at any given energy is proportional both to the slit width and to the square of the resolution in mu sec/m, as well as to the cutoff velocity vc of the rotor; this last is because a larger number of bursts per second become possible as vc is increased. For an idealized cutoff function, it is shown that the total running time for measuring a spectrum is minimum when the ratio of cutoff velocity to peripheral velocity of the rotor is such that approximately 1.67 runs per energy decade are required; this means that the chopper speed and the time-channel width are changed by a factor of two from one run to the next. (auth

ESTIMATING THE PERFORMANCE OF NEUTRON TIME-OF-FLIGHT SPECTROMETERS

Analogy with optical instruments is used to develop formulas for estimating the counting rate achieved by a neutron time-of-flight system. lnput data consist of the flux at the spectrometer entrance and some of the physical characteristics of the spectrometer. Convenient relations for the comparison of different systems are presented. (auth

Direct hodoscope monitoring of flux and power-coupling at TREAT

The most important parameter in calibrating reactor-safety experiments at TREAT is test-fuel energy deposition during irradiation transients. The coupling of the reactor power to the test fuel depends on conditions that vary from experiment to experiment and vary during the transient. In order to more accurately determine the power coupling and better understand its time and space dependencies, data has been obtained by the fast-neutron hodoscope and compared to experiment calibrations, reactor instrumentation data, and theoretical calculations

Final report of fuel dynamics Test E7

Test data from an in-pile failure experiment of high-power LMFBR-type fuel pins in a simulated $3/s transient-overpower (TOP) accident are reported and analyzed. Major conclusions are that (1) a series of cladding ruptures during the 100-ms period preceding fuel release injected small bursts of fission gas into the flow stream; (2) gas release influenced subsequent cladding melting and fuel release (there were no measurable FCI's (fuel-coolant interactions), and all fuel motion observed by the hodoscope was very slow); (3) the predominant postfailure fuel motion appears to be radial swelling that left a spongy fuel crust on the holder wall; (4) less than 4 to 6 percent of the fuel moved axially out of the original fuel zone, and most of this froze within a 10-cm region above the original top of the fuel zone to form the outlet blockage. An inlet blockage approximately 1 cm long was formed and consisted of large interconnected void regions. Both blockages began just beyond the ends of the fuel pellets