Conceptual design of a heavy ion beam probe diagnostic for the Wendelstein 7-X Stellarator.

This article describes the current state of the design of the heavy ion beam probe (HIBP) for Wendelstein 7-X (W7-X). It will be the first HIBP diagnostic on an optimized stellarator and is designed to study electric fields and ion scale turbulence in all W7-X reference magnetic configurations. The use of an existing 2 MV accelerator, located outside of the torus hall, results in the need for a circuitous primary beamline. This increases the complexity of the ion optics design to deliver a focused beam to the plasma. To access most of the magnetic configuration space of W7-X, the secondary beamline and an energy analyzer are designed to pivot, thereby redirecting a wider range of secondary beam trajectories. Signal level estimates indicate that the equilibrium potential can be measured at all radii and that the radial coverage for potential and density fluctuations measurements depends on the plasma density.

Improvement in the spatial resolution of heavy ion beam probe measurements through application of ion optics.

A technique for more accurately modeling and improving the spatial resolution of heavy ion beam probe measurements is described. We use a set of particle trajectories to numerically determine the focusing properties of a complicated three-dimensional magnetic field and characterize these properties with a transfer matrix. We then modify the transfer matrix approach of traditional ion optics to include a parameter that describes the ionization location of the detected ions. The ion optics model calculated using this technique enables a more accurate description of the particle trajectories than previously feasible. The model also allows one to easily determine an initial beam focus that could be used during experimental operation to optimize the spatial resolution of measurements. The technique has been applied to the design of a heavy ion beam probe diagnostic for the Wendelstein 7-X stellarator, and improvements in the modeled spatial resolution by a factor of about 2 over previous estimates are possible. The improved spatial resolution will enable measurements of plasma fluctuations with smaller wavelengths than would otherwise be possible.

The surgical management of sarcomas of the chest wall: A 13-year single institution experience.

INTRODUCTION: Chest wall sarcomas are rare. Resection and reconstruction pose significant anatomical and functional challenges. We present our experience of managing these tumours as plastic surgeons working within a specialist sarcoma MDT. METHODS: All cases of chest wall sarcoma in which a plastic surgeon took part were analysed (2003-2016). Tumours of the breast, abdomen and groin were excluded. Demographics, surgical details and outcomes were analysed. RESULTS: Forty-seven patients were identified. Median age at presentation was 61 years (range 7-91). Thirty-three were male and 14 were female. Chondrosarcoma (n = 16) was the most frequently occurring tumour, followed by myxofibrosarcoma (n = 6), leiomyosarcoma (n = 5) and unclassified sarcomas (n = 5). The majority of tumours were of high (n = 16) or intermediate grade (n = 17) histologically. Wide local excision was carried out in all cases. Twenty-two cases required a mesh and cement reconstruction of the chest wall. Soft tissue reconstruction involved pedicled LD flap +-skin graft (n = 17), direct closure (n = 13), pedicled VRAM (n = 7), free ALT flap (n = 6), and others (n = 4). Clear resection margins were achieved in 32 patients (68%). Fourteen patients underwent adjuvant radiotherapy and four adjuvant chemotherapy. Nine patients (19%) developed a local recurrence, and the median duration from resection to recurrence was 17 months (range 3-72). Nine patients (19%) developed metastasis. Eleven patients died (23.4%), and the median duration of survival 30 months (range 3-92). Thirty-six patients remain well, with a median duration of follow up 57.5 months (range 6-141). Estimated 5 year disease specific survival is 74.2%. CONCLUSION: Plastic surgeons have a vital role in the management of chest wall sarcomas. We present a reconstructive algorithm, which has enabled us to achieve good oncological and functional outcomes and a low complication profile .

Noise mitigation methods for ion detectors operating with a direct view of high temperature plasmas.

We have developed an ion current measurement instrument with a direct view of a plasma that reduces the particle and radiation-induced noise current it detects by over three orders of magnitude, from tens of microamps to tens of nanoamps. This is accomplished using electric fields, magnetic fields, and physical shielding that limit the flux of particles and radiation into the instrument and suppress the secondary electrons produced within it by particle and radiation impact. Operation of this detector in various configurations, without an ion beam, has allowed identification of the sources of noise current. In our experimental setup, the largest noise contributors were found to be plasma ions and photoelectric emission due to UV radiation.

The surgical management of head and neck sarcoma: The Newcastle experience.

INTRODUCTION: Head and neck sarcomas are rare and difficult to manage surgically. Factors that influence the prognosis include the type and grade of tumour, resection margins, the anatomical site and patient-specific parameters. We review our experience as plastic surgeons working in a bone and soft-tissue tumour multidisciplinary team (MDT) in managing these tumours surgically. METHODS: Data on all patients with sarcoma of the head or neck managed surgically from 2004 to 2015 was reviewed. Demographics, surgical details and outcomes were analysed. RESULTS: Forty-nine patients underwent surgery for sarcoma of the head or neck. The mean age at presentation was 53.1 years (range 0.5-92). Histological diagnosis was varied. Leiomyosarcoma (n = 6), angiosarcoma (n = 9), synovial sarcoma (n = 4), sarcoma of no specific type (n = 5) and rhabdomyosarcoma (n = 5) were the most frequently seen tumours. All sarcomas were treated by wide excision. Excision margins were histologically complete in the vast majority (n = 43). Reconstruction was undertaken as follows: direct closure (n = 12), local flap ± skin graft (n = 12), free tissue transfer (n = 21), pedicled flap ± skin graft (n = 3) and skin graft (n = 1). Twelve patients received adjuvant chemotherapy and fifteen patients received adjuvant radiotherapy. Eleven patients developed local recurrence and 10 patients developed metastasis. Twelve patients died of their disease: mean survival period was 17 months (range 8-28 months). The mean duration of follow-up was 78 months (range 18-137 months). Estimated 5-year disease-specific survival for this cohort was 72% and overall estimated survival was 61% (Kaplan-Meier equation). CONCLUSION: Head and neck sarcomas are rare and challenging to manage. Successful outcomes can be achieved by early, aggressive resection and appropriate reconstruction within the specialist MDT setting.

Control of secondary electrons from ion beam impact using a positive potential electrode.

Secondary electrons emitted when an ion beam impacts a detector can amplify the ion beam signal, but also introduce errors if electrons from one detector propagate to another. A potassium ion beam and a detector comprised of ten impact wires, four split-plates, and a pair of biased electrodes were used to demonstrate that a low-voltage, positive electrode can be used to maintain the beneficial amplification effect while greatly reducing the error introduced from the electrons traveling between detector elements.

Development of a beam ion velocity detector for the heavy ion beam probe.

In an axisymmetric plasma, the conservation of canonical angular momentum constrains heavy ion beam probe (HIBP) trajectories such that measurement of the toroidal velocity component of secondary ions provides a localized determination of the poloidal flux at the volume where they originated. We have developed a prototype detector which is designed to determine the beam angle in one dimension through the detection of ion current landing on two parallel planes of detecting elements. A set of apertures creates a pattern of ion current on wires in the first plane and solid metal plates behind them; the relative amounts detected by the wires and plates determine the angle which beam ions enter the detector, which is used to infer the toroidal velocity component. The design evolved from a series of simulations within which we modeled ion beam velocity changes due to equilibrium and fluctuating magnetic fields, along with the ion beam profile and velocity dispersion, and studied how these and characteristics such as the size, cross section, and spacing of the detector elements affect performance.

Bacterial colonisation of the burn wound: a UK experience.

OBJECTIVE: Bacterial colonisation of the burn wound remains a major source of morbidity and mortality in burns patients. This study aimed to determine the presence of different micro-organisms in a UK regional burns centre and to examine the relationships between bacterial colonisation, burn size, length of hospital stay and delayed referral. METHOD: A retrospective review of microbiology surveillance swab results on all adult patients admitted to a regional burns centre over a 12-month period was performed. RESULTS: 139 adult patients were included in the study. Approximately 68% of patients showed evidence of burn wound colonisation at some point during their inpatient stay. The remaining 32% had negative microbiology swabs throughout their hospital stay. A total of 202 micro-organisms were isolated. Staphylococcus aureus was found to be the most common micro-organism, found in 79% of patients with positive swab results. A direct link was found between an increased incidence of bacterial colonisation and delay in referral of >24 hours, larger burn size and length of hospital stay. CONCLUSION: By understanding the potential sources of bacteria and the effect of patient factors on their susceptibility to bacterial colonisation, we can form better management and treatment strategies to reduce morbidity and mortality from burns wound sepsis.

Iliopsoas abscess--a review and update on the literature.

Iliopsoas abscess is a rare condition with a varied symptomology and aetiology. Patients with this condition often present in different ways to different specialities leading to delays in diagnosis and management. Recent advances in the radiological diagnosis of this traditionally rare abscess have highlighted that there is a lack of evidence relating to its aetiology, symptomology, investigation and management. This article reviews the currently available literature to present a concise and systematic review of iliopsoas abscess.

Spontaneous auricular seroma.

We present a case of spontaneous seroma of the ear, which can be encountered in the plastic surgery clinic. We describe our management and briefly review the literature regarding this interesting condition.

Core electrostatic fluctuations and particle transport in a reversed-field pinch.

Potential and electron-density fluctuation profiles, phi(r) and ñ(e)(r)/n(e), are measured for the first time in the core of a reversed-field pinch using a heavy ion beam probe. It is found that the fluctuations are broadband and correlated with the core resonant m/n=1/6 tearing mode. The electrostatic-fluctuation-induced particle transport in the core of standard RFP plasmas, estimated from measured <ñ(e)phi>, is small compared to the total particle flux. Measurements of fluctuations and estimates of fluctuation induced particle transport in improved confinement RFP discharges are also presented.