Social and Behavioral Sciences Commons^™

X-Tream Quality Assurance In Synchrotron X-Ray Microbeam Radiation Therapy, Pauline Fournier, Iwan Cornelius, Mattia Donzelli, Herwig Requardt, Christian Nemoz, Marco Petasecca, Elke Brauer-Krisch, Anatoly B. Rosenfeld, Michael L. F Lerch

Faculty of Engineering and Information Sciences - Papers: Part A

Microbeam radiation therapy (MRT) is a novel irradiation technique for brain tumours treatment currently under development at the European Synchrotron Radiation Facility in Grenoble, France. The technique is based on the spatial fractionation of a highly brilliant synchrotron X-ray beam into an array of microbeams using a multi-slit collimator (MSC). After promising pre-clinical results, veterinary trials have recently commenced requiring the need for dedicated quality assurance (QA) procedures. The quality of MRT treatment demands reproducible and precise spatial fractionation of the incoming synchrotron beam. The intensity profile of the microbeams must also be quickly and quantitatively characterized prior to each …

Comparing And Evaluating The Efficacy Of The Tor18fg Leeds Test X-Ray Phantom For T-Rays, Elise Maree Pogson, Joanne Macnamara, Peter Metcalfe, R A. Lewis

Faculty of Engineering and Information Sciences - Papers: Part A

The commercially available X-ray fluoroscopy quality assurance phantom, the Leeds test object TOR18FG, was found to be suitable to assess T-ray image quality in the range (0.1-0.4) THz at a depth of 0.5 cm. Previous to this only custom made phantoms, made especially for the T-ray region, assessed T-ray spatial resolution. However, if sub-wavelength techniques are used, the Leeds test phantom may be implemented to measure the T-ray systems spatial resolution, allowing us to directly compare X-ray and T-ray spatial resolution. The systems compared include a Gulmay Orthovoltage machine (X-ray), the On Board Imager (OBI) of a Varian linear accelerator …

A Systematic Study Of Radio-Induced X-Ray Cavities In Clusters, Groups, And Galaxies, L Birzan, D A. Rafferty, B R. Mcnamara, M W. Wise, Paul E. J Nulsen

Faculty of Engineering and Information Sciences - Papers: Part A

We present an analysis of 16 galaxy clusters, one group, and one galaxy drawn from the Chandra Data Archive. These systems possess prominent X-ray surface brightness depressions associated with cavities or bubbles that were created by interactions between powerful radio sources and the surrounding hot gas. The central galaxies in these systems harbor radio sources with luminosities ranging between ∼2 × 10 38 and 7 × 10 44 ergs s -1. The cavities have an average radius of ∼10 kpc, and they lie at an average projected distance of ∼20 kpc from the central galaxy. The minimum energy associated with …

The Soft X-Ray Background: Evidence For Widespread Disruption Of The Gas Haloes Of Galaxy Groups, K K S Wu, A C. Fabian, Paul E. J Nulsen

Faculty of Engineering and Information Sciences - Papers: Part A

Almost all of the extragalactic X-ray background (XRB) at 0.25 keV can be accounted for by radio-quiet quasars, allowing us to derive an upper limit of 4 keV cm⁻² s⁻¹ sr⁻¹ keV⁻¹ for the remaining background at 0.25 keV. However, the XRB from the gas haloes of groups of galaxies, with gas removal resulting from cooling accounted for, exceeds this upper limit by an order of magnitude if non-gravitational heating is not included. We calculate this using simulations of halo merger trees and realistic gas density profiles, which we require to reproduce the observed gas fractions …

Chandra X-Ray Observations Of The 3c 295 Cluster Core, S W. Allen, G B. Taylor, Paul E J Nulsen, R M. Johnstone, L P. David, S Ettori, A C. Fabian, W R. Forman, C Jones, B Mcnamara

Faculty of Engineering and Information Sciences - Papers: Part A

We examine the properties of the X-ray gas in the central regions of the distant (z=0.46), X-ray luminous cluster of galaxies surrounding the powerful radio source 3C 295, using observations made with the Chandra Observatory. Between radii of 50 and 500 kpc, the cluster gas is approximately isothermal with an emission-weighted temperature, kT∼5 keV. Within the central 50-kpc radius this value drops to kT∼3.7 keV. The spectral and imaging Chandra data indicate the presence of a cooling flow within the central 50-kpc radius of the cluster, with a mass deposition rate of approximately 280 M_{⊙ …}

On The Soft X-Ray Spectrum Of Cooling Flows, A C. Fabian, R F. Mushotzky, Paul E. J Nulsen, J R. Peterson

Faculty of Engineering and Information Sciences - Papers: Part A

Strong evidence for cooling flows has been found in low-resolution X-ray imaging and spectra of many clusters of galaxies. However, high-resolution X-ray spectra of several clusters from the Reflection Grating Spectrometer on XMM-Newton now show a soft X-ray spectrum inconsistent with a simple cooling flow. The main problem is a lack of the emission lines expected from gas cooling below 1–2 keV. Lines from gas at about 2–3 keV are observed, even in a high-temperature cluster such as A1835, indicating that gas is cooling down to about 2–3 keV, but is not found at lower temperatures. Here we discuss several …

Non-Gravitational Heating In The Hierarchical Formation Of X-Ray Clusters, K K S Wu, A C. Fabian, Paul E J Nulsen

Faculty of Engineering and Information Sciences - Papers: Part A

The strong deviation in the properties of X-ray clusters from simple scaling laws highlights the importance of non-gravitational heating and cooling processes in the evolution of protocluster gas. We investigate this from two directions: by finding the amount of ‘excess energy’ required in intracluster gas in order to reproduce the observed X-ray cluster properties, and by studying the excess energies obtained from supernovae in a semi-analytic model of galaxy formation. Using the insights obtained from the model, we then critically discuss possible ways of achieving the high excess specific energies required in clusters. These include heating by supernovae and active …

A Physical Model For The Hard X-Ray Background, R J. Wilman, A C. Fabian, Paul E J Nulsen

Faculty of Engineering and Information Sciences - Papers: Part A

We combine a semi-analytic galaxy formation model with a prescription for the obscured growth of massive black holes, to reproduce the hard X-ray background (XRB), the local 2–10 keV active galactic nuclei (AGN) luminosity function and the source counts, including recent Chandra results. The model also complies with constraints on the AGN contribution to the far-infrared and submillimetre backgrounds.

The comoving density of luminous AGN [L(2-10keV) > 10⁴⁴ erg s^-1, in the unabsorbed rest-frame] in the model declines sharply since z=2, mimicking the observed evolution of the quasar population. The abundance of lower luminosity AGN simultaneously increases, and …