P.F. Harrison

A high precision Q-meter for the measurement of proton polarization in polarised targets

A Q-meter system for the measurement of the proton polarisation in polarised targets is described, in which the real part of the output signal, rather than its magnitude, is used to obtain the polarisation. It uses a radio frequency phase sensitive detection technique. Calculations are presented which show that a very high linearity is obtained with this system when used under the experimental conditions obtained in typical polarised targets. A description of the electronic circuits used to implement such a system is given, together with measurements of their performance.

A rapid reflectance anisotropy spectrometer

A 16 channel reflectance anisotropy (RA) spectrometer capable of simultaneously acquiring reflectance spectra and real and imaginary RA spectra on the 0.1 s time-scale is reported. Its performance was evaluated by monitoring the electrolytic deposition/growth and removal of copper on a gold(110) surface. The slow deposition enabled very low noise spectra to be obtained, which served as the yardstick with which the spectra obtained during the rapid removal could be compared. The spectra obtained over the 15 s removal mirrored those obtained during the 500 s deposition period. The spectra are discussed in terms of the copper growth being in the form of aligned islands.

The influence of high intensity terahertz radiation on mammalian cell adhesion, proliferation and differentiation.

Understanding the influence of exposure of biological systems to THz radiation is becoming increasingly important. There is some evidence to suggest that THz radiation can influence important activities within mammalian cells. This study evaluated the influence of the high peak power, low average power THz radiation produced by the ALICE (Daresbury Laboratory, UK) synchrotron source on human epithelial and embryonic stem cells. The cells were maintained under standard tissue culture conditions, during which the THz radiation was delivered directly into the incubator for various exposure times. The influence of the THz radiation on cell morphology, attachment, proliferation and differentiation was evaluated. The study demonstrated that there was no difference in any of these parameters between irradiated and control cell cultures. It is suggested that under these conditions the cells are capable of compensating for any effects caused by exposure to THz radiation with the peak powers levels employed in these studies.

'Near-field optical microscopy with an infra-red free electron laser applied to cancer diagnosis'

We show that the combination of a scanning near field optical microscope and an infra-red free electron laser yields chemical images with sub-cellular spatial resolution that have the potential to provide a diagnostic for oesophageal adenocarcinoma.

Detection of DNA hybridisation on a functionalised diamond surface using reflection anisotropy spectroscopy

The analysis of single-stranded DNA attached to a polycrystalline diamond surface by reflection anisotropy spectroscopy (RAS) demonstrates that the DNA is oriented essentially vertically to the surface. RAS is able to detect the hybridisation between the attached strand and the homologous sequence.

Azimuthal dependent reflection anisotropy spectroscopy of Ag(110) near the plasmon resonance energy

The reflection anisotropy (RA) of Ag(110) has been investigated near 3.9 eV as a function of azimuthal angle θ using a photoelastically modulated spectrometer. At 3.9 eV the RA signal was small and varied as sin 4θ. At photon energies away from 3.9 eV the signal increased and varied as cos 2θ. Jones vector modeling of the system showed that in addition to the commonly observed cos 2θ dependence, which disappears when the reflection is isotropic, there is a sin 4θ dependence that occurs when the underlying dielectric function is anisotropic; in cubic materials this term is small but for other materials it may be very large.

A new UV reflection anisotropy spectrometer and its application to the Au(1 1 0)/electrolyte surface

The development of a UV reflection anisotropy spectrometer has extended the current range of the reflection anisotropy spectrometry (RAS) technique to 7.0 eV. The extra range has been used to obtain the RAS of the Au(1 1 0)/electrolyte interface to 7.0 eV. The RA spectrum obtained for this interface is significantly different in the range 4.6 to 5.5 eV from the results obtained with the conventional instrument.

A streamer tube detector for operation at high rates in the CPLEAR experiment at CERN

Abstract The design and instrumentation of a streamer tube detector for operation in the high rate environment of the CPLEAR experiment at CERN is described. A study of gas mixtures for use in the streamer tube is discussed. The final mixture of 46% argon, 50% isobutane, 4% methylal and 0.01% freon produces an axial resolution of 1.5 cm with an efficiency of 98% per layer.