446 research outputs found
Towards Laser Driven Hadron Cancer Radiotherapy: A Review of Progress
It has been known for about sixty years that proton and heavy ion therapy is
a very powerful radiation procedure for treating tumours. It has an innate
ability to irradiate tumours with greater doses and spatial selectivity
compared with electron and photon therapy and hence is a tissue sparing
procedure. For more than twenty years powerful lasers have generated high
energy beams of protons and heavy ions and hence it has been frequently
speculated that lasers could be used as an alternative to RF accelerators to
produce the particle beams necessary for cancer therapy. The present paper
reviews the progress made towards laser driven hadron cancer therapy and what
has still to be accomplished to realise its inherent enormous potential.Comment: 40 pages, 24 figure
Photon echo quantum memories in inhomogeneously broadened two level atoms
Here we propose a solid-state quantum memory that does not require spectral
holeburning, instead using strong rephasing pulses like traditional photon echo
techniques. The memory uses external broadening fields to reduce the optical
depth and so switch off the collective atom-light interaction when desired. The
proposed memory should allow operation with reasonable efficiency in a much
broader range of material systems, for instance Er3+ doped crystals which have
a transition at 1.5 um. We present analytic theory supported by numerical
calculations and initial experiments.Comment: 7 pages, 8 figure
Orbital electron capture by the nucleus
The theory of nuclear electron capture is reviewed in the light of current understanding of weak interactions. Experimental methods and results regarding capture probabilities, capture ratios, and EC/Beta(+) ratios are summarized. Radiative electron capture is discussed, including both theory and experiment. Atomic wave function overlap and electron exchange effects are covered, as are atomic transitions that accompany nuclear electron capture. Tables are provided to assist the reader in determining quantities of interest for specific cases
In Situ Characterisation of Permanent Magnetic Quadrupoles for focussing proton beams
High intensity laser driven proton beams are at present receiving much
attention. The reasons for this are many but high on the list is the potential
to produce compact accelerators. However two of the limitations of this
technology is that unlike conventional nuclear RF accelerators lasers produce
diverging beams with an exponential energy distribution. A number of different
approaches have been attempted to monochromise these beams but it has become
obvious that magnetic spectrometer technology developed over many years by
nuclear physicists to transport and focus proton beams could play an important
role for this purpose. This paper deals with the design and characterisation of
a magnetic quadrupole system which will attempt to focus and transport
laser-accelerated proton beams.Comment: 20 pages, 42 figure
Ultrahigh and persistent optical depths of caesium in Kagom\'e-type hollow-core photonic crystal fibres
Alkali-filled hollow-core fibres are a promising medium for investigating
light-matter interactions, especially at the single-photon level, due to the
tight confinement of light and high optical depths achievable by light-induced
atomic desorption. However, until now these large optical depths could only be
generated for seconds at most once per day, severely limiting the practicality
of the technology. Here we report the generation of highest observed transient
( for up to a minute) and highest observed persistent ( for
hours) optical depths of alkali vapours in a light-guiding geometry to date,
using a caesium-filled Kagom\'e-type hollow-core photonic crystal fibre. Our
results pave the way to light-matter interaction experiments in confined
geometries requiring long operation times and large atomic number densities,
such as generation of single-photon-level nonlinearities and development of
single photon quantum memories.Comment: Author Accepted versio
Highly multimode memory in a crystal
We experimentally demonstrate the storage of 1060 temporal modes onto a
thulium-doped crystal using an atomic frequency comb (AFC). The comb covers
0.93 GHz defining the storage bandwidth. As compared to previous AFC
preparation methods (pulse sequences i.e. amplitude modulation), we only use
frequency modulation to produce the desired optical pumping spectrum. To ensure
an accurate spectrally selective optical pumping, the frequency modulated laser
is self-locked on the atomic comb. Our approach is general and should be
applicable to a wide range of rare-earth doped material in the context of
multimode quantum memory
A concise patient reported outcome measure for people with aphasia: the aphasia impact questionnaire 21
Background: There are many validated and widely used assessments within aphasiology. Few, however, describe language and life with aphasia from the perspective of the person with aphasia. Across healthcare, patient experience and user involvement are increasingly acknowledged as fundamental to person-centred care. As part of this movement, Patient Reported Outcome Measures (PROMs) are being used in service evaluation and planning.
Aims: This paper reports the quantitative aspects of a mixed methods study that developed and validated a concise PROM, the Aphasia Impact Questionnaire (AIQ), co-produced with People with Aphasia (PWA).
Methods & Procedures: The AIQ was developed within the social model of disability and all stages of the development of the AIQ were performed in partnership with PWA. It was adapted from a pre-existing and lengthier PROM for PWA, the Communication Disability Profile. The first iterations of the AIQ focused on domains of communication, participation and well-being/emotional state. Subsequently the AIQ was extended to include additional items relating to reading and writing (AIQ-21). The research design was iterative. Initially, concurrent validity, internal consistency, and sensitivity of the AIQ-prototype were obtained. The AIQ-prototype was modified to become the AIQ-21. Statistical testing with a new group of PWA was performed, investigating internal consistency and concurrent validity of the AIQ-21.
Outcomes & Results: Results for both the AIQ-prototype and AIQ-21 showed statistically significant concurrent validity and good internal consistency. Repeated measurement using the AIQ-prototype demonstrated statistically significant change after PWA accessed a community intervention.
Conclusions: The AIQ-21 is a PROM that has great potential to be one of the core set of aphasia tests for clinical and research use. Results can be used alongside language assessment to enable person-centred goal setting and partnership working for people with aphasia
The nuclear AC-Stark shift in super-intense laser fields
The direct interaction of super-intense laser fields in the optical frequency
domain with nuclei is studied. As main observable, we consider the nuclear
AC-Stark shift of low-lying nuclear states due to the off-resonant excitation
by the laser field. We include the case of accelerated nuclei to be able to
control the frequency and the intensity of the laser field in the nuclear rest
frame over a wide range of parameters. We find that AC-Stark shifts of the same
order as in typical quantum optical systems relative to the respective
transition frequencies are feasible with state-of-the-art or near-future laser
field intensities and moderate acceleration of the target nuclei. Along with
this shift, we find laser-induced modifications to the proton root-mean-square
radii and to the proton density distribution. We thus expect direct
laser-nucleus interaction to become of relevance together with other
super-intense light-matter interaction processes such as pair creation.Comment: 10 pages, 2 eps figure
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