High Power Proton Beam Shocks and Magnetohydrodynamics in a Mercury Jet Target for a Neutrino Factory

The feasibility of liquid metal jet targets for secondary particle production with high power proton beams has been studied. The main aspects of the thesis were benchmark experiments covering the behaviour of liquid targets under thermal shock waves induced by high power proton beams, and also magnetohydrodynamic effects. Severe challenges were imposed by safety issues and the restricted beam time to the tests in ISOLDE at CERN and at the High Magnetic Field Laboratory at Grenoble. Restricted access times in high radiation level areas were of the order of minutes and in this short time span, the complete experimental setup had to be performed and verified. The involvement of mercury as liquid target material and its activation during beam tests demanded special confinement precautions. The setup for both experiments was based on the use of a high speed camera system for observation of the mercury target. The presence of high radiation or high magnetic field required the installation of the sensitive camera system at distances up to 15 m. The method of shadow photography had to be used because of the highly reflective surface of mercury. During proton beam tests at the CERN ISOLDE facility and at Brookhaven AGS, the behaviour of a mercury target as a function of various proton beam parameters was analysed. The experimental results allow for extrapolation from the present data by one order of magnitude to the final design of a high power jet target foreseen for a neutrino factory. Observed velocities of the mercury splash were up to 45 m/s. The experimental setup used at the High Magnetic Field Laboratory allowed a successful demonstration of injecting a 12 m/s mercury jet with a diameter d=4 mm into a 20 T solenoidal field. The results of this experiment revealed the magnetohydrodynamic effects, which occur in the free jet and in the supplying mercury circuit, and serve as benchmark for numerical codes. The extrapolation to the nominal parameters of a neutrino factory shows that the concept of a jet target is a valid option

A meta-analysis of demographic characteristics and learning by deaf students

This study is designed to identify those educational, communication and demographic characteristics which serve as predictors of student performance on college entrance exams as well as their comprehension learning via interpreted lectures at the college level. A database was created for 509 deaf students using information from 33 different demographic areas. A series of statistical analyses including multiple regressions were performed, none of which yielded statistically significant findings, despite their considerable power. These results indicate that deaf students\u27 academic success is not pre-determined by anyone characteristic or combination of easily identifiable characteristics

Development of ultrafast UTE imaging for granular systems

Ultrashort echo time (UTE) imaging is commonly used in medical MRI to image 'solid' types of tissue; to date it has not been widely used in engineering or materials science, in part due to the relatively long imaging times required. Here we show how the acquisition time for UTE can be reduced to enable a preliminary study of a fluidized bed, a type of reactor commonly used throughout industry containing short T$_{2}$$^{∗}$ material and requiring fast imaging. We demonstrate UTE imaging of particles with a T$_{2}$$^{∗}$ of only 185μs, and an image acquisition time of only 25ms. The images are obtained using compressed sensing (CS) and by exploiting the Hermitian symmetry of k-space, to increase the resolution beyond that predicted by the Nyquist theorem. The technique is demonstrated by obtaining one- and two-dimensional images of bubbles rising in a model fluidized bed reactor.HTF would like to acknowledge the financial support of the Gates Cambridge Trust. All authors would like to acknowledge the financial support of the EPSRC (EP/K008218/1, EP/F047991/1 and EP/K039318/1)

Comparison of Options for the Injector of PS2

In its report, the SPC Review Panel has highlighted that the construction of a 4 MW SPL has to be motivated by the needs of a well-defined and approved physics programme, and that it should be compared with a Rapid Cycling Synchrotron (RCS) when considering only the needs of LHC. This report is meant to answer these remarks by describing the version of the SPL that would be built for the needs of LHC alone (the Low Power SPL or LP-SPL) and by making a preliminary comparison with an RCS

The radiation field in the Gamma Irradiation Facility GIF++ at CERN

The high-luminosity LHC (HL-LHC) upgrade is setting now a new challenge for particle detector technologies. The increase in luminosity will produce a particle background in the gas-based muon detectors that is ten times higher than under conditions at the LHC. The detailed knowledge of the detector performance in the presence of such a high background is crucial for an optimized design and efficient operation after the HL-LHC upgrade. A precise understanding of possible aging effects of detector materials and gases is of extreme importance. To cope with these challenging requirements, a new Gamma Irradiation Facility (GIF++) was designed and built at the CERN SPS North Area as successor of the Gamma Irradiation Facility (GIF) during the Long Shutdown 1 (LS1) period. It features an intense source of 662 keV photons with adjustable intensity, to simulate continuous background over large areas, and, combined with a high energy muon beam, to measure detector performance in the presence of the background. The new GIF++ facility has been operational since spring 2015. In addition to describing the facility and its infrastructure, the goal of this work is to provide an extensive characterization of the GIF++ photon field with different configurations of the absorption filters in both the upstream and downstream irradiation areas. Moreover, the measured results are benchmarked with Geant4 simulations to enhance the knowledge of the radiation field. The absorbed dose in air in the facility may reach up to 2.2 Gy/h directly in front of the irradiator. Of special interest is the low-energy photon component that develops due to the multiple scattering of photons within the irradiator and from the concrete walls of the bunker

Estimation of Decay Losses and Dynamic Vacuum for the Beta-beam Accelerator Chain

The beta-beam is based on the acceleration and storage of radioactive ions. Due to the large number of ions required and their relatively short lifetime, beam losses are a major concern. This paper estimates the decay losses for the part of the accelerator chain comprising the CERN PS and SPS machines. For illustration purposes, the power deposition in these accelerators is compared to that expected for nominal CNGS proton operation. The beam losses induced vacuum dynamics is simulated and the consequences for machine operation are discussed

Ultrashort echo time (UTE) imaging using gradient pre-equalization and compressed sensing.

Ultrashort echo time (UTE) imaging is a well-known technique used in medical MRI, however, the implementation of the sequence remains non-trivial. This paper introduces UTE for non-medical applications and outlines a method for the implementation of UTE to enable accurate slice selection and short acquisition times. Slice selection in UTE requires fast, accurate switching of the gradient and r.f. pulses. Here a gradient "pre-equalization" technique is used to optimize the gradient switching and achieve an effective echo time of 10μs. In order to minimize the echo time, k-space is sampled radially. A compressed sensing approach is used to minimize the total acquisition time. Using the corrections for slice selection and acquisition along with novel image reconstruction techniques, UTE is shown to be a viable method to study samples of cork and rubber with a shorter signal lifetime than can typically be measured. Further, the compressed sensing image reconstruction algorithm is shown to provide accurate images of the samples with as little as 12.5% of the full k-space data set, potentially permitting real time imaging of short T2(*) materials.HTF would like to acknowledge the financial support of the Gates-Cambridge Trust and all authors of the EPSRC (EP/K008218/1). In addition, we would like to thank SoftPoint Industries Inc. for providing samples of rubber.This version is final published version, distributed under a Creative Commons Attribution License 2.0. This can also be viewed on the publisher's website at: http://www.sciencedirect.com/science/article/pii/S1090780714001840