23 research outputs found
Effect of Electron Traps on Scintillation of Praseodymium Activated Lu3Al5O12
No full textIn this paper we present the studies performed on a set of Lu3Al5O12:Pr (LuAG:Pr) crystals with praseodymium concentration between 1.5 and 10%, grown by the micro-pulling-down (muPD) technique. The research comprises the measurements of X-ray excited emission spectra and 137Cs gamma-ray pulse height spectra in a range from 78 to 600 K, and thermoluminescence glow curves. Based on experimental data we discuss the dependence of scintillation properties of Lu3Al5O12:Pr on praseodymium content and temperature. The main attention is focused on a distinct increase of scintillation yield with temperature, which we attribute to existence of shallow electron traps and their temperature-dependent contribution to scintillation of LuAG:Pr. An active role of traps is demonstrated by a novel experiment combining X-ray and laser excitation.Radiation, Radionuclides and ReactorsApplied Science
Imaging of charge trapping in distorted carbon nanotubes by x-ray excited scanning probe microscopy
No full textWe have observed the distribution of electron trapping centers on distorted carbon nanotubes (CNTs) by a unique x-ray analysis technique that has both elemental and spatial selectivities. This technique involves the use of scanning probe microscopy (SPM) under synchrotron radiation excitation of the inner shell of carbon. The probe detects the Coulomb force that results from the relaxation of an electron bound to a defect site into the core hole state created by x-ray photon absorption. This results in a change in charge state of the defect. At the spatial resolution provided by the SPM technique, we observed the electron trapping centers distributed on the compressed and torsionally distorted CNTs. This direct association of mechanical distortion with defect sites indicates a potential risk of deterioration of electric properties during the fabrication and processing of CNT networks.Applied Science
Direct evidence for the participation of band-tails and excited-state tunnelling in the luminescence of irradiated feldspars
No full textThe significance and extent of band-tail states in the luminescence and dosimetry properties of natural aluminosilicates (feldspars) is investigated by means of studies using low temperature (10 K) irradiation and optically stimulated luminescence (OSL) stimulation spectroscopy, and thermoluminescence (TL) in the range 10–200 K, made in comparison with high temperature (300 K) irradiation and photo-transferred OSL and TL investigations undertaken at low temperature. These measurements allow mappings of the band-tails to be made; they are found to be ?0.4 eV in extent in the typical materials studied. Furthermore, by populating charge trapping centres at high temperature (300 K) and monitoring the OSL stimulation spectra at temperatures in the range 10–300 K, clear evidence is presented for the presence of both thermally activated and non-thermally activated OSL processes; it is argued that the former result from thermally activated hopping through the band-tail states, whilst the latter are due to tunnelling processes, either from the excited state of the OSL centres or through the tail states. The spectral measurements are supported by analysis of the temporal dependence of the OSL signals, which correspond to either tunnelling or general order kinetic decay processes.RRR/Radiation, Radionuclides and ReactorsApplied Science
Carrier recombination processes and divalent lanthanide spectroscopy in YPO4:Ce3+;L3+ (L=Sm,Dy,Tm)
No full textWe studied charge carrier trapping, detrapping, and recombination phenomena in Ce3+ doped YPO4, codoped with Sm3+, Dy3+, or Tm3+. Ce ions trap the holes and Sm, Dy, and Tm trap electrons created during x-ray irradiation. By means of red to infrared stimulation, the trapped electrons can be back transferred to Ce leading to shorter wavelength Ce3+?5d-4f luminescence. Excitation spectra for this recombination luminescence were recorded from 10 K to room temperature. It provides information on the excited state energies of divalent Sm, Dy, and Tm with respect to the lanthanide ground state energy and with respect to the mobility edge energy of YPO4. From the temperature dependence, insight is obtained on the carrier recombination pathways. We will identify temperature independent tunneling recombination, recombination by thermal excitation to the conduction band, and phonon-assisted delocalization of electrons from impurity states within the conduction band.QN/Quantum NanoscienceApplied Science
Micro-imaging synchrotron-laser interactions in wide band-gap luminescent materials
No full textApplied Science
Development of a target imaging system for the European Spallation Source
No full textAt the European Spallation Source (ESS) neutrons will be produced by a proton beam impinging on a rotating target wheel. The technology of the target wheel, which comprises a large number of closely spaced tungsten bricks and is cooled by helium, is largely untested. The durability of the target wheel and hence the overall ESS neutronic performance depend on the integrity of the tungsten bricks. In order to monitor whether the target geometry is preserved over the expected 5 year lifetime of the target wheel, we propose a Target Imaging System (TIS). The TIS consists of a scintillator array detecting the collimated single photon emission (decay gammas) from the activated tungsten bricks. Preliminary Monte Carlo simulations support the feasibility of this imaging system. As a proof-of-principle, an experimental test-rig is being constructed allowing to test the main aspects of the imaging system under conditions relevant to ESS
Optical dating in a new light: A direct, non-destructive probe of trapped electrons
No full textAbstractOptical dating has revolutionized our understanding of Global climate change, Earth surface processes, and human evolution and dispersal over the last ~500 ka. Optical dating is based on an anti-Stokes photon emission generated by electron-hole recombination within quartz or feldspar; it relies, by default, on destructive read-out of the stored chronometric information. We present here a fundamentally new method of optical read-out of the trapped electron population in feldspar. The new signal termed as Infra-Red Photo-Luminescence (IRPL) is a Stokes emission (~1.30 eV) derived from NIR excitation (~1.40 eV) on samples previously exposed to ionizing radiation. Low temperature (7–295 K) spectroscopic and time-resolved investigations suggest that IRPL is generated from excited-to-ground state relaxation within the principal (dosimetry) trap. Since IRPL can be induced even in traps remote from recombination centers, it is likely to contain a stable (non-fading), steady-state component. While IRPL is a powerful tool to understand details of the electron-trapping center, it provides a novel, alternative approach to trapped-charge dating based on direct, non-destructive probing of chronometric information. The possibility of repeated readout of IRPL from individual traps will open opportunities for dating at sub-micron spatial resolution, thus, marking a step change in the optical dating technology.</jats:p
Golf swing technician Jim Christine: Bridging the gap between the science of the golf swing and the art of golf coaching: A Commentary
No full textThe stimulus article, “Golf swing technician Jim Christine: Bridging the gap between the science of the golf swing and the art of golf coaching”, and the accompanying commentaries present some key issues in golf coaching, especially coach development, technology, coaching methods, and critical thinking.
The first two commentaries provide insight about Jim Christine’s development as a coach. International golf coach Peter Green discusses the legendary John Jacobs, who Jim accepted an invitation from to shadow him at one of his golf schools; and John Stirling, who Jim had coaching from on his own golf game. PGA Master Professional Luther Blacklock discusses Alex Hay, who also coached Jim. Both Stirling and Hay were pioneers in the training programme of the Professional Golfers’ Association (PGA) of Great Britain and Ireland in which Jim became highly influential as an author of training resources and as a tutor.
There are commentaries from three distinguished members of the PGA of America, the world’s largest working sports organisation: David Wright, John Callahan and Eric Alpenfels. John Callahan shares how he took up opportunities to shadow leading golf coaches such as TJ Tomasi, Craig Shankland and Paul Runyan during his PGA apprenticeship under Frank Cardi. Callahan advocates the use of launch monitors as a technological aid, more staunchly so than Jim Christine who is aware of the limitations in the algorithms involved in providing the output from a radar device like TrackMan for measuring impact factors. Chris Bertram refers to his own empirical research on the use of another technological aid, video feedback, to indicate that “just because technical information is readily available, it does not mean that more information is necessarily serving the interests of the student” (p. 37). Drawing on his doctoral research on operant conditioning, David Wright discusses backward chaining, which is one of the coaching methods used by Jim Christine. Eric Alpenfels discusses Jim’s use of coaching methods in terms of “focus of attention – internal/external swing cues” (p. 33). Researchers Thomas Hawkins et al., suggest that “[the clock analogy], one of Christine’s favoured coaching tools may result in performance and learning benefits [through external focus of attention] because it allows the body to organise movement better than it would if conscious control was either requested or triggered by an internally focused coaching instruction” (p. 35). In a similar vein, Nicky Lumb, a PGA coach “who specialises in golf practice management, skill development and peak performance” (p. 40), indicates that several of Jim’s coaching tools give the golfer an external focus of attention. There is overlap in what Nicky does with Edward Coughlan, a sports scientist whose “main job for players involves asking questions about how they practice, what they practice and inevitably, whether their practice transfers to the competition arena” (p. 42).
While two PGA of Great Britain and Ireland professionals, Will Shaw and Gordon Morrison discuss some of Jim’s coaching methods from an Information-Processing perspective, a third one – Noel Rousseau – advocates an Ecological Dynamics/Constraints-led Approach. Rousseau presents the case that “Jim’s coaching methods are staunchly embedded in the Information Processing camp yet he simultaneously highlights some of the shortcoming of coaching this way” (p. 50), especially on the matter of sloping lies (p. 51).
Jim describes himself as a “swing technician” (p. 17). Researchers Liam Thomas et al. discuss the notion of a ‘model golf swing’ or ‘technical blue print’ and highlight the challenge of distinguishing between ‘technical faults’ and “the inherent variability both within and between individuals in response to changes in constraints” (p. 54). Tour pro coach, Hugh Marr argues, “Every coach has a picture in their head of what a great swing looks like. It’s not the model that makes coaches great, it’s the understanding of what George Gankas calls ‘match-ups’ – if a player displays one particular swing characteristic, they need to match it with another swing characteristic that complements it” (p. 57).
The final two commentaries, by research professor David Grecic and performance coach Jon Roy, both emphasize the development of critical thinking in coaches, with the latter arguing that “Jim’s critical faculties comprise dialectics, scepticism, and innovation” (p. 63)
Optically detected x-ray absorption spectroscopy measurements as a means of monitoring corrosion layers on copper
No full textXANES and EXAFS information is conventionally measured in transmission through the energy-dependent absorption of X-rays or by observing X-ray fluorescence, but secondary fluorescence processes, such as the emission of electrons and optical photons (e.g., 200-1000 nm), can also be used as a carrier of the XAS signatures, providing complementary information such as improved surface specificity. Where the near-visible photons have a shorter range in a material, the data will be more surface specific. Moreover, optical radiation may escape more readily than X-rays through liquid in an environmental cell. Here, we describe a first test of optically detected X-ray absorption spectroscopy (ODXAS) for monitoring electrochemical treatments on copper-based alloys, for example, heritage metals. Artificially made corrosion products deposited on a copper substrate were analyzed in air and in a 1% (w/v) sodium sesquicarbonate solution to simulate typical conservation methods for copper-based objects recovered from marine environments. The measurements were made on stations 7.1 and 9.2 MF (SRS Daresbury, UK) using the mobile luminescence end station (MoLES), supplemented by XAS measurements taken on DUBBLE (BM26 A) at the ESRF. The ODXAS spectra usually contain fine structure similar to that of XAS spectra measured in X-ray fluorescence. Importantly, for the compounds examined, the ODXAS is significantly more surface specific, and > 98% characteristic of thin surface layers of 0.5-1.5-mu m thickness in cases where X-ray measurements are dominated by the substrate. However, EXAFS and XANES from broadband optical measurements are superimposed on a high background due to other optical emission modes. This produces statistical fluctuations up to double what would be expected from normal counting statistics because the data retain the absolute statistical fluctuation in the original raw count, while losing up to 70% of their magnitude when background is removed. The problem may be solved in future through optical filtering to isolate the information-containing band, combined with the use of higher input X-ray fluxes available on third-generation light sources
Golf swing technician Jim Christine: Bridging the gap between the science of the golf swing and the art of golf coaching: A Commentary
No full textThe stimulus article, “Golf swing technician Jim Christine: Bridging the gap between the science of the golf swing and the art of golf coaching”, and the accompanying commentaries present some key issues in golf coaching, especially coach development, technology, coaching methods, and critical thinking.
The first two commentaries provide insight about Jim Christine’s development as a coach. International golf coach Peter Green discusses the legendary John Jacobs, who Jim accepted an invitation from to shadow him at one of his golf schools; and John Stirling, who Jim had coaching from on his own golf game. PGA Master Professional Luther Blacklock discusses Alex Hay, who also coached Jim. Both Stirling and Hay were pioneers in the training programme of the Professional Golfers’ Association (PGA) of Great Britain and Ireland in which Jim became highly influential as an author of training resources and as a tutor.
There are commentaries from three distinguished members of the PGA of America, the world’s largest working sports organisation: David Wright, John Callahan and Eric Alpenfels. John Callahan shares how he took up opportunities to shadow leading golf coaches such as TJ Tomasi, Craig Shankland and Paul Runyan during his PGA apprenticeship under Frank Cardi. Callahan advocates the use of launch monitors as a technological aid, more staunchly so than Jim Christine who is aware of the limitations in the algorithms involved in providing the output from a radar device like TrackMan for measuring impact factors. Chris Bertram refers to his own empirical research on the use of another technological aid, video feedback, to indicate that “just because technical information is readily available, it does not mean that more information is necessarily serving the interests of the student” (p. 37). Drawing on his doctoral research on operant conditioning, David Wright discusses backward chaining, which is one of the coaching methods used by Jim Christine. Eric Alpenfels discusses Jim’s use of coaching methods in terms of “focus of attention – internal/external swing cues” (p. 33). Researchers Thomas Hawkins et al., suggest that “[the clock analogy], one of Christine’s favoured coaching tools may result in performance and learning benefits [through external focus of attention] because it allows the body to organise movement better than it would if conscious control was either requested or triggered by an internally focused coaching instruction” (p. 35). In a similar vein, Nicky Lumb, a PGA coach “who specialises in golf practice management, skill development and peak performance” (p. 40), indicates that several of Jim’s coaching tools give the golfer an external focus of attention. There is overlap in what Nicky does with Edward Coughlan, a sports scientist whose “main job for players involves asking questions about how they practice, what they practice and inevitably, whether their practice transfers to the competition arena” (p. 42).
While two PGA of Great Britain and Ireland professionals, Will Shaw and Gordon Morrison discuss some of Jim’s coaching methods from an Information-Processing perspective, a third one – Noel Rousseau – advocates an Ecological Dynamics/Constraints-led Approach. Rousseau presents the case that “Jim’s coaching methods are staunchly embedded in the Information Processing camp yet he simultaneously highlights some of the shortcoming of coaching this way” (p. 50), especially on the matter of sloping lies (p. 51).
Jim describes himself as a “swing technician” (p. 17). Researchers Liam Thomas et al. discuss the notion of a ‘model golf swing’ or ‘technical blue print’ and highlight the challenge of distinguishing between ‘technical faults’ and “the inherent variability both within and between individuals in response to changes in constraints” (p. 54). Tour pro coach, Hugh Marr argues, “Every coach has a picture in their head of what a great swing looks like. It’s not the model that makes coaches great, it’s the understanding of what George Gankas calls ‘match-ups’ – if a player displays one particular swing characteristic, they need to match it with another swing characteristic that complements it” (p. 57).
The final two commentaries, by research professor David Grecic and performance coach Jon Roy, both emphasize the development of critical thinking in coaches, with the latter arguing that “Jim’s critical faculties comprise dialectics, scepticism, and innovation” (p. 63)
