Specific instrumentation and diagnostics for high-intensity hadron beams

An overview of various typical instruments used for high-intensity hadron beams is given. In addition, a few important diagnostic methods are discussed which are quite special for these kinds of beams.Comment: 58 pages, contribution to the CAS - CERN Accelerator School: Course on High Power Hadron Machines; 24 May - 2 Jun 2011, Bilbao, Spai

RECOVERY ACT: MULTIMODAL IMAGING FOR SOLAR CELL MICROCRACK DETECTION

Undetected microcracks in solar cells are a principal cause of failure in service due to subsequent weather exposure, mechanical flexing or diurnal temperature cycles. Existing methods have not been able to detect cracks early enough in the production cycle to prevent inadvertent shipment to customers. This program, sponsored under the DOE Photovoltaic Supply Chain and Cross-Cutting Technologies program, studied the feasibility of quantifying surface micro-discontinuities by use of a novel technique, thermoreflectance imaging, to detect surface temperature gradients with very high spatial resolution, in combination with a suite of conventional imaging methods such as electroluminescence. The project carried out laboratory tests together with computational image analyses using sample solar cells with known defects supplied by industry sources or DOE National Labs. Quantitative comparisons between the effectiveness of the new technique and conventional methods were determined in terms of the smallest detectable crack. Also the robustness of the new technique for reliable microcrack detection was determined at various stages of processing such as before and after antireflectance treatments. An overall assessment is that the new technique compares favorably with existing methods such as lock-in thermography or ultrasonics. The project was 100% completed in Sept, 2010. A detailed report of key findings from this program was published as: Q.Zhou, X.Hu, K.Al-Hemyari, K.McCarthy, L.Domash and J.Hudgings, High spatial resolution characterization of silicon solar cells using thermoreflectance imaging, J. Appl. Phys, 110, 053108 (2011)

DEVELOPMENT OF SURFACE BASED PLATFORMS FOR BIOMOLECULAR RECOGNITION AND PROTEASE ASSAYS

The discovery of analytical tools for biomolecular recognition in the area of diagnostics is a research trend rich in innovative methods. Some of the main drivers found in this area are the constant need for low cost devices and biosensors, simplicity in design and operation, and time efficiency. In this thesis we present novel approaches for the development of protease activity assays. Our focus of study is the protease assay development process on two types of characterized platforms: microspheres and self-assembled monolayers (SAMs) on flat surfaces. The surface preparation and conjugation process with biological components of interest is presented along with surface plasmon resonance (SPR) and flow cytometry results. These platforms were engineered in order to develop assays for bacterial toxin activity. Bacterial toxins are comprised in part of proteases, which selectively cleave peptides bonds in proteins. In this thesis we present, protease assays from our main focus of studies, the Clostridium botulinum Neurotoxin type A Light Chain (BoNTA/LC) metalloprotease. Supplementary studies include assays performed involving the Bacillus anthracis Lethal factor metalloprotease. In the work described we have prepared active recombinant protease substrates in our laboratory, capable of binding with the surfaces of study. In addition, we present methods to on how to address non-specific binding issues inherited by the nature of these assays. Commercially available recombinant proteases have been utilized throughout these studies. These studies present novel methods for BoNT protease detection based on previous microsphere-based assays. Our biomimetic detection platforms show promise for further understanding BoNTs toxicity, the biological pathways of BoNTs substrates, and possible contributions to the discovery of protease inhibitors

Biocompatible plasmonic nanostructures for bio-imaging applications and novel functional plasmonic materials

Our work addresses a novel biocompatible plasmon-enhanced nanostructure approach based on the combination of metal nanoparticles, light emitting polymer-based nanostructures, and scalable cellulose nanofiber templates via a one-step facile electrospinning process that can easily be applied to biomedical devices. In collaboration with the Team of Prof. Lee Goldstein in the Boston University medical campus, we demonstrated light emission from small-size (below 200nm) polymer nanoparticles coupled to plasmonic nanoparticles and to light-emitting biocompatible molecules. In order to fully demonstrate the potential of our novel plasmonic nanostructures we developed Magnetic resonance imaging (MRI) reagent doped Polycaprolactone (Core)-Polyethylene glycol (shell) core-shell nanoparticles and studied their size distribution and dispersion properties in a phosphate buffered saline solution. Our materials were optimized in order to obtain no aggregation of the nanoparticles in solution. The presence of MRI reagent in nanoparticles were demonstrated via Inversion Recovery Sequences (IR) by characterizing the different T1 relaxation times. The concentration of Gd in the nanoparticles dispersion was estimated with different dilution of Gd commercial reagent as a reference. In addition, we combined facile electrospinning fabrication with top down nano-deposition and demonstrated a novel and scalable plasmonic resonant medium for rapid and reliable Raman scattering sensing of molecular monolayers and bacteria. Specifically, aided by PCA multivariate data analysis techniques, we demonstrated fingerprinting Surface Enhanced Raman Scattering (SERS) spectra of different bacteria strains (E. Coli K12, E. coli BL21 (DE3) and E. coli DH 5α) entrapped in our novel plasmonic networks. Finally, in this thesis we have also addressed the development of novel, Si-compatible and largely tunable plasmonic materials for biosensing applications in the mid-infrared spectral range and developed a novel type of transparent conductive oxide based on the Indium Silicon Oxide (ISO) material (Indium Silicon Oxide) that features enhanced surface smoothness and thermal stability compared to Indium tin oxide (ITO) and Titanium nitride (TiN) alternative plasmonic materials. In collaboration with our collaborators at Columbia University, we demonstrated the tunability of near-field plasmonic resonances from 1.8 to 5.0 μm as a function of different annealing temperature. This work provides an enabling first-step towards the development of novel Si-compatible materials with tunable plasmon resonances for metamaterials and sensing devices that operate across the infrared spectrum.2019-07-02T00:00:00

Design and performance analysis of a picosecond-pulsed laser raman spectrometer for fluorescence rejection in raman spectroscopy

Many attempts have been made to reduce fluorescence backgrounds in Raman spectra. A critical appraisal of fluoresence rejection techniques reveals that while many techniques are available which improve the Raman/fluorescence ratio (R/F), very few actually increase the spectral signal/noise (R/N), which is the most important parameter. Temporal-resolution of Raman and fluorescence photons was investigated in this laboratory, using a picosecond-laser system and gated photon detection. Two detection methods were evaluated. The first, an intensified diode array detector (DAD), could be gated "on" for periods of ca. 5 ns, at rates of up to 5kHz. This gave a 5-fold increase in R/F, but a slight reduction in R/N, for a fluorescor with τ(_f) ̴̱ 1O.5 ns. The R/N degradation arose as a result of the low laser output intensity at kHz pulse rates, rather than inefficiency in fluorescence rejection. The second method used a continuously-operated photomultiplie tube (PMT), and time-correlated photon counting with ca. 1 ns timing-resolution. This yielded R/F and R/N improvements of ca. 15 and 3 respectively (τ(_f) ̴̱ 12 ns).Although efficient fluorescence rejection was obtained with each system, the corresponding R/N enhancements were not practically significant. However, the development of theoretical models describing the performance of each system has identified modifications which should give valuable improvements. These include the use of a laser with MW peak powers at kHz pulse rates (DAD system), and use of a microchannel-plate PMT with 50 ps timing resolution. When these (and other) modifications are made, significant R/N enhancements (ca. 7 and 13 (DAD and PMT systems respectively)) are expected, thus enabling the study of the majority of "real world" samples. In addition, the limiting theoretical and practical performance of time-resolved rejection is considered, and several hitherto unreported aspects of the behaviour of the laser and detection systems are discussed. Other techniques were also evaluated, in particular utilising the differing Raman and fluorescence response to variations in laser intensity. While the non-linear fluorescence responseto intensity variations of cw lasers has been previously exploited, simple calculations indicate that the use of high-powered pulsed sources could allow discrimination at ca. 100- fold lower average powers. However, a satisfactory test of the calculations requires the construction of apparatus not presently available in this .laboratory

Diagnosis of Multiple Scan-Chain Faults in the Presence of System Logic Defects

We present a combined hardware-software based approach to scan-chain diagnosis, when the outcome of a test may be affected by system faults occurring in the logic outside of the scan chain. For the hardware component we adopt the double-tree scan (DTS) chain architecture, which has previously been shown to be effective in reducing power, volume, and application time of tests for stuck-at and delay faults. We develop a version of flush test which can resolve a multiple fault in a DTS chain to a small number of suspect candidates. Further resolution to a unique multiple fault is enabled by the software component comprising of fault simulation and analysis of the response of the circuit to test patterns produced by ATPG. Experimental results on benchmark circuits show that near-perfect scan-chain diagnosis for multiple faults is possible even when a large number of random system faults are injected in the circuit

High-Power Laser Systems for Driving and Probing High Energy Density Physics Experiments

This thesis describes the construction of a hybrid OPCPA and Nd:Glass based laser system to provide advanced diagnostic capabilities for the MAGPIE pulsed power facility at Imperial College London. The laser system (named Cerberus) is designed to provide one short pulse 500 fs beam for proton probing and two long pulse beams, one for x-ray backlighting and one for Thomson scattering. The aim of this project is to accurately determine plasma parameters in a range of demanding experimental environments. The thesis is split into two sections; the first section provides details about the design and implementation of the laser system while the latter chapters present experimental data obtained on the MAGPIE facilty. The front end for the laser system is based on optically synchronised Optical Parametric Chirped Puled Amplification (OPCPA) which is supplemented by large aperture flashlamp pumped Nd:Glass power amplifiers in the latter stages to increase the energy to the Joule level. The use of optical parametric amplifiers (OPAs) in the pre-amplifier stages reduces gain narrowing, B-integral and improves contrast. Simulations of the dispersive optics for the Chirped Pulse Amplification (CPA) system are described in detail. Spatially resolved Thomson scattering was used to measure temperature and velocity of ablation streams in aluminium and tungsten cylindrical wire arrays. The measurements show a peak ow velocity of 120 km/s and agree well with 3D MHD simulations for the case of aluminium. There is discrepancy with the tungsten data caused by the difficulty in handling of collisionality calculations. Novel data showing the self-emission of ions from tungsten radial wire arrays is presented as a key step towards laser driven proton probing of MAGPIE. It is observed that the bulk of the emission corresponds to low energy protons with energies of ~ 100 keV. Protons with energy > 600 keV were observed to emanate from the collapsing magnetic jet using a coded aperture camera. These results offer interesting new prospects in diagnosing wire arrays.Open Acces