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No description available.

Detection of B-mode polarization from the cosmic microwave background would provide compelling evidence for the inflationary paradigm and has thus become a principal goal for experimental cosmologists during the last 5-10 years. A number of high sensitivity experiments have been developed and many are under construction, including the E and B EXperiment (EBEX), a balloon-borne experiment scheduled to take data in 2010. The design of EBEX is presented here, including the scientific motivation for the experiment, and an overview of all its components, with particular attention paid to the read out electronics for its array of over 1300 biometries detectors. In the read out of such a large array of bolometers, which must be kept at ∼250mK, running many signals down the same wire (i.e. multiplexing) is vital. The digital frequency multiplexing (dfmux) electronics designed and tested at McGill addresses this as well as providing the control required to tune the bolometers and super conducting quantum interference devices (SQUIDs) used in readout. How these electronics accomplish both of these goals is described with an in-depth description of the recently designed tuning algorithms required to take the detectors from initialization to fully-operational. Finally, some tests of the readout system on cold bolometers in a test cryostat are presented. These measurements are encouraging with 98% success rate of automated tuning on a test sample of 47 bolometers. Improvements to achieve a 100% success rate have been proposed and will be implemented for the upcoming integration of the bolometer camera with the telescope in November 2008. A test-flight for the experiment is planned for spring 2009, and the science flight for 2010 from Antarctica.

The frequency variation of various nuclear interactions under lead has been studied by comparing the number of different kinds of stars produced in Ilford G5 emulsion exposed directly to the air, and under 15.1cm and 10.lcm of lead. From these observations the attenuation lengths in lead are found to be: 320 +/- 12g. per cm^2 for all stars; 274 +/- 27g. per cm^2 for stars with charged primaries; 200 +/- 35g. per cm^2 for stars with uncharged primaries, excluding simple evaporation stars. The size-frequency distribution of stars and its relation to the composition of the emulsion is discussed.

No description available.

No description available.

One of the main harbingers of the modern age of precision cosmology, the Cosmic Microwave Background (CMB) has proven itself to be a veritable trove of cosmological information. With the aid of experiments such as the WMAP satellite, precision measurements of the CMB anisotropy spectra are now being made. / This work will first explore the physics of the Vishniac effect, a small-scale CMB temperature anisotropy created by the Compton scattering of CMB photons by free electrons caught in a line-of-sight bulk flow. The Vishniac effect arises due to a density enhancement in the electrons caused by gravitational potentials in both the linear and nonlinear regimes and contributes significant power to the CMB temperature anisotropy power spectrum on small scales. This effect is strongly dependent upon cosmology and as such this dependence is investigated for all experimentally-allowed values of the fundamental cosmological parameters. This analysis is performed for both the linear Vishniac effect as well as its nonlinear extension. Following this analysis a fitting function, capable of predicting the power generated by the Vishniac effect over a range of scales for any allowed cosmology, is investigated. This function proves to be an accurate and efficient way of computing the Vishniac effect for any input cosmology. / The next small-scale phenomenon to be explored is the small-scale CMB polarization anisotropies generated by Thomson scattering of the local photon quadrupole anisotropy during reionization. The underlying physics behind this effect are studied along with the observational information it potentially contains. Observational data of the remote quadrupole is capable of improving constraints in the CMB temperature anisotropy spectrum on scales of ℓ ∼ 11 as well as offering information concerning the reconstruction of the primordial density perturbations on gigaparsec scales in our local universe.

We investigate the effect of allowing freedom in the primordial power spectrum of curvature perturbations upon the measurement of other cosmological parameters, in particular the Thomson optical depth due to cosmic reionisation which is present in cosmic microwave background (CMB) observations. We find that the constraint on the optical depth from Wilkinson Microwave Anisotropy Probe (WMAP) data broadens by approximately 10% upon allowing spectral freedom on large scales, and by a slightly larger factor when considering data from future experiments with lower noise in measurements of CMB polarisation. We also present a reconstruction of the primordial power spectrum on the largest scales from WMAP, which is jointly obtained from this analysis.

Previous work on the muon component of extensive air showers is described and reviewed with particular reference to the muon heights of origin with respect to the main cascade. Thu mechanical and operating details of a specialist experiment to determine the heights of origin of muons are described together with the results from detailed computer simulations which are tailored to resemble the characteristics of the equipment. The raw experimental data are examined in detail as a precursor to interpreting the data from the equipment. The final results from the experiment are given in detail and their relevance to air shower cascade development discussed. Suggestions are made for future work in this and related fields.

This thesis is concerned with the measurement of the longitudinal cascade development of large cosmic-ray showers from observations of atmospheric Cerenkov radiation. The purpose of the measurements is to obtain information on the mass composition of the primary cosmic rays and on the gross features of the high-energy hadronic interactions. The characteristics of the Cerenkov light signal which are strongly coupled to the longitudinal shower development are described with reference to computer simulation results. An experiment designed to measure these characteristics was deployed in Dugway, Utah, U.S.A. between October 1977 and March 1980. Measurements were made in showers of primary energy 10(^15) – 10(^18) eV. Existing data analysis techniques have been refined and new procedures developed in order to optimise the reduction of the digital data. A detailed analysis is given of two aspects of the time structure of the Cerenkov light signal in showers of mean primary energy ~ 2 x 10(^17) eV. The measurements are interpreted in terms of the mean depth of electron cascade maximum and the fluctuations occurring between showers. The many results on the cascade development currently available from the Dugway data are summarised. Interpretation of the results is found to be possible in the framework of scaling-based models of the high energy hadronic interactions which incorporate an enhancement of the central-region multiplicity. This allows certain inferences to be made concerning the primary mass composition. Specifically, primaries of energy ~ 10(^16) eV appear to be predominantly heavy nuclei, and the mass composition becomes lighter with increasing primary energy until at least ~ 2 x 10(^17) eV. While no other single experiment has yet been in a position to corroborate these results, broad consistency is found between the Dugway results and the combined results from a number of other experiments.