Showing papers by "Jörg Schmiedmayer published in 1989"

The equivalence of the gravitational and inertial mass of the neutron

Abstract: A comparison of the neutron scattering length of carbon evaluated from a high precision total cross section measurement and the scattering length as measured with the neutron gravity refractometer leads to the most accurate determination of the equivalence factor γ between the gravitational and inertial mass for the neutron γ = 100038∓000025 Using all available data on scattering lengths and taking into account all systematic errors one obtains γ = 100011∓000017 The relevance of this result to the search for a composition dependent fifth force and possible new experiments are discussed

The electric polarizability of the neutron

Abstract: In a strong electric field, the neutron, due to its internal charge structure, acquires an induced electric dipole moment. For the electric polarizability of the neutron a value of αn ⋍ 1 × 10−3fm3, similar to that of the proton, is expected from quark model calculations. The smallness of αn makes a measurement based on macroscopic electric fields available with present technology impossible, and a neutron Compton scattering experiment seems unfeasible without a free neutron target at least 5 to 10 orders of magnitude more dense than in the core of present day high flux reactors. In the strong electric field near the surface of heavy nuclei, effects due to the electric polarizability of the neutron contribute up to 1% of the total neutron atom scattering for αn ⋍ 1 × 10−3fm3. Here the 1r4 interaction potential gives a characteristic scattering contribution proportional to the momentum transfer hq which can be separated from nuclear and atomic effects in keV neutron scattering experiments. In a new neutron transmission experiment on Pb at energies < 50 keV at the HELIOS neutron source in Harwell, the electric polarizability of the neutron was determined from the energy dependence of the total scattering cross section to be αn = (1.2 ± 1.0) × 10−3 fm3, giving 90% confidence for a nonzero positive value of αn. This result and other recent experiments including future improvements will be discussed.

An analog and time digitizer for two-dimensional data acquisition for time-of-flight measurements

Abstract: A CAMAC module has been developed to record simultaneously the pulse height and the elapsed time of an event following a start signal. The module is based on an 8-bit (256-channel) 100 MHz fast analog to digital converter (FADC) and a 16-bit (65536-channel) time digitizer with a maximum time range of 4.9 ms and a minimum resolving time of 20 ns. A short dead time in the data acquisition equipment is required to keep count loss corrections to an acceptable level at high count rates. The processing of the signal including storage of the data in a 256-word buffer takes place during the 10 ns dead time of the module. A built-in digital to analog converter (DAC) can be used to set up and test the module. The unit can be used in several different ways, for example (a) as a multiparameter neutron time-of-flight spectrometer, (b) as a transient wave recorder with a continuous read-in, (c) as a transient wave recorder with a 16-block read-in and (d) as a self-triggering digital discriminator. In this report a description is given of the use of the system in neutron transmission measurements using the pulsed neutron source HELIOS at Harwell. In these measurements the count rates were several times the highest count rate previously recorded on such experiments at Harwell. The count loss and background were more easily and more accurately calculated from the information gained from the two-dimensional recording of the data.