48 research outputs found
A steel-scintillator counter to detect neutrons
A steel-scintillator sandwich counter was used as a simple and highly efficient detector for both neutrons and protons. The validity of simple approximations for the detection efficiency was investigated by experimental tests and a detailed Monte Carlo calculation of the nuclear and electromagnetic cascades in the counter.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32659/1/0000024.pd
Benchmarking of electro-optic monitors for femtosecond electron bunches
The longitudinal profiles of ultrashort relativistic electron bunches at the soft x-ray free-electron laser FLASH have been investigated using two single-shot detection schemes: an electro-optic (EO) detector measuring the Coulomb field of the bunch and a radio-frequency structure transforming the charge distribution into a transverse streak. A comparison permits an absolute calibration of the EO technique. EO signals as short as 60 fs (rms) have been observed, which is a new record in the EO detection of single electron bunches and close to the limit given by the EO material properties
Information Geometry of Quantum Entangled Gaussian Wave-Packets
Describing and understanding the essence of quantum entanglement and its
connection to dynamical chaos is of great scientific interest. In this work,
using information geometric (IG) techniques, we investigate the effects of
micro-correlations on the evolution of maximal probability paths on statistical
manifolds induced by systems whose microscopic degrees of freedom are Gaussian
distributed. We use the statistical manifolds associated with correlated and
non-correlated Gaussians to model the scattering induced quantum entanglement
of two spinless, structureless, non-relativistic particles, the latter
represented by minimum uncertainty Gaussian wave-packets. Knowing that the
degree of entanglement is quantified by the purity P of the system, we express
the purity for s-wave scattering in terms of the micro-correlation coefficient
r - a quantity that parameterizes the correlated microscopic degrees of freedom
of the system; thus establishing a connection between entanglement and
micro-correlations. Moreover, the correlation coefficient r is readily
expressed in terms of physical quantities involved in the scattering, the
precise form of which is obtained via our IG approach. It is found that the
entanglement duration can be controlled by the initial momentum p_{o}, momentum
spread {\sigma}_{o} and r. Furthermore, we obtain exact expressions for the IG
analogue of standard indicators of chaos such as the sectional curvatures,
Jacobi field intensities and the Lyapunov exponents. We then present an
analytical estimate of the information geometric entropy (IGE); a suitable
measure that quantifies the complexity of geodesic paths on curved manifolds.
Finally, we present concluding remarks addressing the usefulness of an IG
characterization of both entanglement and complexity in quantum physics.Comment: 37 pages, 3 figure
Time resolved single-shot measurments of transition radiation at the THz beamline of FLASH using electro-optic spectral decoding
Test structures for the characterisation of conductive carbon produced from photoresist
Conductive carbon films are highly attractive for use as electrodes in electrochemistry and biosensing applications. Patterned photoresist films can be transformed into carbon electrodes using standard photolithographic techniques followed by pyrolysation of the photoresist in a furnace under a reducing atmosphere. Previous studies have been made of the electrical properties of blanket carbon films created using this method of fabrication. However, there is a need to investigate pattern dependent effects, particularly the extent to which the dimensions of the patterned films shrink during the high temperature processing. This study applies microfabricated test structures to the process characterisation of conductive carbon produced from standard positive photoresists