Design of a custom insertable probe platform for measurements of C-2W inner divertor plasma parameters

A custom motor controlled probe system has been designed to make spatially resolved measurements of temperature, density, flow, and plasma potential in the C-2W inner divertors. Measurements in the inner divertors, which have a 1.7 m radius and are located on either end of the confinement vessel, are critical in order to gauge exactly how local settings affect the plasma conditions, confinement, and stability in the field-reversed configuration core. The inner Divertor Insertable Probe Platform (iDIPP) system consists of a custom motor controlled linear rack and pinion transporter that has a 1.9 m travel length in order to reach the center of the divertor. Mounted to the end of the transporter is a 1 m long segmented probe shaft made of individually floating stainless steel rings to prevent shorting out the electrode plates, which are biased up to 5 kV/m. A variety of interchangeable probe tips, including a triple Langmuir probe, a baffled probe, and a Gundestrup probe, can plug into the end of the probe shaft. Custom UHV coiled cabling comprised of 9 shielded conductors expands/retracts with the motion of the transporter in/out of the divertor. The physics motivating plasma parameter measurements in the inner divertors and the details of the design of the iDIPP system will be discussed.

Integrated diagnostic and data analysis system of the C-2W advanced beam-driven field-reversed configuration plasma experiment

The new C-2W experiment (also called Norman) at TAE Technologies, Inc. studies the evolution of field-reversed configuration (FRC) plasmas sustained by neutral beam injection. Data on the FRC plasma performance are provided by a comprehensive suite of diagnostics that includes over 700 magnetic sensors, four interferometer systems, multi-chord far-infrared polarimetry, two Thomson scattering systems, ten types of spectroscopic measurements, multiple fast imaging cameras with selectable atomic line filters, bolometry, reflectometry, neutral particle analyzers, and fusion product detectors. Most of these diagnostic systems are newly built using experience and data from the preceding C-2U experiment to guide the design process. A variety of commercial and custom acquisition electronics collect over 4000 raw signals from the C-2W diagnostics. These data are processed into physics results using a large-scale database of diagnostics metadata and analysis software, both built using open-source software tools.

Calibration and applications of visible imaging cameras on the C-2U advanced beam-driven field-reversed configuration device

Two filtered, fast-imaging instruments, with radial and axial views, respectively, were used on the C-2U device to visualize line emission from impurities and hydrogenic neutrals. Novel calibration techniques needed to be developed for these instruments because the accelerated pace of C-2U operations precluded access to the interior of the vacuum vessel, targets used in typical calibration methods were not available, and in order to account for effects which have not been sufficiently addressed in the literature. Spatial calibration involved optimizing parameters in a generic camera model: ex situ using a checkerboard target and in situ using the vacuum vessel port geometry. Radiometric calibration was performed ex situ in three stages. First, the camera relative response function was mapped using an algorithm developed for high dynamic-range imaging. Second, the non-uniformity of the optical system was measured using a large LCD monitor with a characterized angular emission pattern. Finally, the absolute photon efficiency of each interference filter was determined using a calibrated uniform radiance source while also accounting for reduction in the filter transmission for off-normal rays. Periodically during the run campaign, line emission from neutral beams fired into a gas target was used as an in situ reference to check for degradation of viewport transmission. One application using calibrated camera data was tomographic reconstruction of passive impurity emission, which provided a sanity check to the excluded-flux radius inferred from wall-mounted magnetic sensors.

Thomson scattering systems on C-2W field-reversed configuration plasma experiment

TAE Technologies' newly constructed C-2W experiment aims to improve the ion and electron temperatures in a sustained field-reversed configuration plasma. A suite of Thomson scattering systems has been designed and constructed for electron temperature and density profile measurements. The systems are designed for electron densities of 1 × 10¹² cm^-3 to 2 × 10¹⁴ cm^-3 and temperature ranges from 10 eV to 2 keV. The central system will provide profile measurements of T_e and n_e at 16 radial locations from r = -9 cm to r = 64 cm with a temporal resolution of 20 kHz for 4 pulses or 1 kHz for 30 pulses. The jet system will provide profile measurements of T_e and n_e at 5 radial locations in the open field region from r = -5 cm to r = 15 cm with a temporal resolution of 100 Hz. The central system and its components have been characterized, calibrated, installed, and commissioned. A maximum-likelihood algorithm has been applied for data processing and analysis.

Jet outflow and open field line measurements on the C-2W advanced beam-driven field-reversed configuration plasma experiment

Accurate operation and high performance of the open field line plasma surrounding the field reversed configuration is crucial to achieving the goals of successful temperature ramp up and confinement improvement on C-2W. Knowledge and control of the open field line plasma requires extensive diagnostic efforts. A suite of diagnostics, which consists of microwave interferometry, dispersive spectroscopy, and spatial heterodyne spectroscopy, is being developed to measure electron density, ion temperature, and particle outflow velocity at various locations along the open magnetic field lines. A detailed overview of these diagnostics is presented.

Magnetic diagnostic suite of the C-2W field-reversed configuration experiment

A fundamental component of any magnetically confined fusion experiment is a firm understanding of the magnetic field. The increased complexity of the C-2W machine warrants an equally enhanced diagnostic capability. C-2W is outfitted with over 700 magnetic field probes of various types. They are both internal and external to the vacuum vessel. Inside, a linear array of innovative in-vacuum annular flux loop/B-dot combination probes provide information about plasma shape, size, pressure, energy, temperature, and trapped flux when coupled with established theoretical interpretations. A linear array of B-dot probes complement the azimuthally averaged measurements. A Mirnov array of 64 3D probes, with both low and high frequency resolution, detail plasma motion and MHD modal content via singular value decomposition analysis. Internal Rogowski probes measure axial currents flowing in the plasma jet. Outside, every feed-through for an internal probe has an external axial field probe. There are many external loops that measure the plasma formation dynamics and the total external magnetic flux. The external measurements are primarily used to characterize eddy currents in the vessel during a plasma shot. Details of these probes and the data derived from their signals are described.

Characterization and calibration of the Thomson scattering diagnostic suite for the C-2W field-reversed configuration experiment

The new C-2W Thomson scattering (TS) diagnostic consists of two individual subsystems for monitoring electron temperature (T_e) and density (n_e): one system in the central region is currently operational, and the second system is being commissioned to monitor the open field line region. Validating the performance of the TS's custom designed system components and unique calibration of the detection system and diagnostic as a whole is crucial to obtaining high precision T_e and n_e profiles of C-2W's plasma. The major components include a diode-pumped Nd:YAG laser which produces 35 pulses at up to 20 kHz, uniquely designed collection lenses with a fast numerical aperture, and uniquely designed polychromators with filters sets to optimize a T_e ranging from 10 eV to 2 keV. This paper describes the design principles and techniques used to characterize the main components of the TS diagnostic on C-2W, as well as the results of Rayleigh scattering calibrations performed for the whole system response.

Development of a Z eff diagnostic using visible and near-infrared bremsstrahlung light for the C-2W field-reversed configuration plasma

In C-2W, an elevated impurity concentration can lead to significant degradation of plasma performance and energy losses through radiation. To gauge plasma contamination from impurities, the effective ion charge (Z _eff) can be determined from measurements of bremsstrahlung continuum radiation over a small spectral range free from line radiation. To this end, a diagnostic system including visible and near-infrared bremsstrahlung detectors was deployed in C-2W to measure time-dependent radial distributions of Z _eff. The system is complemented by an array of survey spectrometers which enable full-range spectroscopic measurements of impurity emission lines from the vacuum ultraviolet to the near infrared, providing a good picture of the plasma composition. Here, the design scheme for this integrated diagnostic system is presented and discussed.

Particle and heat flux diagnostics on the C-2W divertor electrodes

A suite of diagnostics was developed to measure particle and heat fluxes arriving at the divertor electrodes of the C-2W experiment at TAE Technologies. The divertor electrodes consist of 4 concentric rings, each equipped with a bolometer, electrostatic energy analyzer, and thermocouple mounted at two opposing azimuthal locations. These probes provide measurements of the power flux to the divertor electrodes as well as measurements of the ion current density, ion energy distribution, and total energy deposition. The thermocouples also provide calibration points for inferring the heat deposition profile via thermographic imaging of the electrodes with a fast infrared camera. The combined measurements enable the calculation of the energy lost per escaping electron/ion pair, which is an important metric for understanding electron heat transport in the open field lines that surround the field-reversed configuration plasma in C-2W.

High sensitivity far infrared laser diagnostics for the C-2U advanced beam-driven field-reversed configuration plasmas

A high sensitivity multi-channel far infrared laser diagnostics with switchable interferometry and polarimetry operation modes for the advanced neutral beam-driven C-2U field-reversed configuration (FRC) plasmas is described. The interferometer achieved superior resolution of 1 × 10¹⁶ m^-2 at >1.5 MHz bandwidth, illustrated by measurement of small amplitude high frequency fluctuations. The polarimetry achieved 0.04° instrument resolution and 0.1° actual resolution in the challenging high density gradient environment with >0.5 MHz bandwidth, making it suitable for weak internal magnetic field measurements in the C-2U plasmas, where the maximum Faraday rotation angle is less than 1°. The polarimetry resolution data is analyzed, and high resolution Faraday rotation data in C-2U is presented together with direct evidences of field reversal in FRC magnetic structure obtained for the first time by a non-perturbative method.

The upgrade of the Thomson scattering system for measurement on the C-2/C-2U devices

The C-2/C-2U Thomson scattering system has been substantially upgraded during the latter phase of C-2/C-2U program. A Rayleigh channel has been added to each of the three polychromators of the C-2/C-2U Thomson scattering system. Onsite spectral calibration has been applied to avoid the issue of different channel responses at different spots on the photomultiplier tube surface. With the added Rayleigh channel, the absolute intensity response of the system is calibrated with Rayleigh scattering in argon gas from 0.1 to 4 Torr, where the Rayleigh scattering signal is comparable to the Thomson scattering signal at electron densities from 1 × 10¹³ to 4 × 10¹⁴ cm^-3. A new signal processing algorithm, using a maximum likelihood method and including detailed analysis of different noise contributions within the system, has been developed to obtain electron temperature and density profiles. The system setup, spectral and intensity calibration procedure and its outcome, data analysis, and the results of electron temperature/density profile measurements will be presented.

End loss analyzer system for measurements of plasma flux at the C-2U divertor electrode

An end loss analyzer system consisting of electrostatic, gridded retarding-potential analyzers and pyroelectric crystal bolometers was developed to characterize the plasma loss along open field lines to the divertors of C-2U. The system measures the current and energy distribution of escaping ions as well as the total power flux to enable calculation of the energy lost per escaping electron/ion pair. Special care was taken in the construction of the analyzer elements so that they can be directly mounted to the divertor electrode. An attenuation plate at the entrance to the gridded retarding-potential analyzer reduces plasma density by a factor of 60 to prevent space charge limitations inside the device, without sacrificing its angular acceptance of ions. In addition, all of the electronics for the measurement are isolated from ground so that they can float to the bias potential of the electrode, 2 kV below ground.

Diagnostic suite of the C-2U advanced beam-driven field-reversed configuration plasma experiment

The C-2U experiment at Tri Alpha Energy studies the evolution of field-reversed configuration (FRC) plasmas sustained by neutral beam injection. Data on the FRC plasma performance are provided by a comprehensive suite of diagnostics that includes magnetic sensors, interferometry, Thomson scattering, spectroscopy, bolometry, reflectometry, neutral particle analyzers, and fusion product detectors. While many of these diagnostic systems were inherited from the preceding experiment C-2, C-2U has a variety of new and upgraded diagnostic systems: multi-chord far-infrared polarimetry, multiple fast imaging cameras with selectable atomic line filters, proton detector arrays, and 100 channel bolometer units capable of observing multiple regions of the spectrum simultaneously. In addition, extensive ongoing work focuses on advanced methods of measuring separatrix shape and plasma current profile that will facilitate equilibrium reconstruction and active control of the FRC plasma.

Enhanced magnetic field probe array for improved excluded flux calculations on the C-2U advanced beam-driven field-reversed configuration plasma experiment

External flux conserving coils were installed onto the exterior of the C-2U [M. W. Binderbauer et al., Phys. Plasmas 22, 056110 (2015)] confinement vessel to increase the flux confinement time of the system. The 0.5 in. stainless steel vessel wall has a skin time of ∼5 ms. The addition of the external copper coils effectively increases this time to ∼7 ms. This led to better-confined/longer-lived field-reversed configuration (FRC) plasmas. The fringing fields generated by the external coils have the side effect of rendering external field measurements invalid. Such measurements were key to the previous method of excluded flux calculation [M. C. Thompson et al., Rev. Sci. Instrum. 83, 10D709 (2012)]. A new array of B-dot probes and Rogowski coils were installed to better determine the amount of flux leaked out of the system and ultimately provide a more robust measurement of plasma parameters related to pressure balance including the excluded flux radius. The B-dot probes are surface mountable chip inductors with inductance of 33 μH capable of measuring the DC magnetic field and transient field, due to resistive current decay in the wall/coils, when coupled with active integrators. The Rogowski coils measure the total change in current in each external coil (150 A/2 ms). Currents were also actively driven in the external coils. This renders the assumption of total flux conservation invalid which further complicates the analysis process. The ultimate solution to these issues and the record breaking resultant FRC lifetimes will be presented.

Jet outflow and open field line measurements on the C-2U advanced beam-driven field-reversed configuration plasma experiment

Knowledge and control of the axial outflow of plasma particles and energy along open-magnetic-field lines are of crucial importance to the stability and longevity of the advanced beam-driven field-reversed configuration plasma. An overview of the diagnostic methods used to perform measurements on the open field line plasma on C-2U is presented, including passive Doppler impurity spectroscopy, microwave interferometry, and triple Langmuir probe measurements. Results of these measurements provide the jet ion temperature and axial velocity, electron density, and high frequency density fluctuations.

Structure of a novel 13 nm dodecahedral nanocage assembled from a redesigned bacterial microcompartment shell protein

We report the crystal structure of a novel 60-subunit dodecahedral cage that results from self-assembly of a re-engineered version of a natural protein (PduA) from the Pdu microcompartment shell. Biophysical data illustrate the dependence of assembly on solution conditions, opening up new applications in microcompartment studies and nanotechnology.

Utilization of Cavity Vortex To Delay the Wetting Transition in One-Dimensional Structured Microchannels

Frictional resistance across rough surfaces depends on the existence of slip on the liquid-gas interface; therefore, prolonging the existence of liquid-gas interface becomes relevant. In this work, we explore manipulation of the cavity shape in order to delay the wetting transition. We propose that liquid-driven vortices generated in the air cavity dissipate sufficient energy to delay the Cassie-Wenzel transition. Toward this, we fabricated cavities on the side walls of a polydimethylsiloxane-based microchannel for easy visualization and analysis of the dynamics of the liquid-gas interface. Two distinct flow regimes are identified in the experimental envelope. In the first regime, the liquid-gas interface is found to be protruding into the flow field, thus increasing the pressure drop at low Reynolds number. In the second regime, flow rate and geometry-based wetting transitions are established at moderate to high Reynolds numbers. We then investigate the effect of different cavity shapes (square, trapezoidal, and U-shape) in delaying the wetting transition by manipulating liquid-driven vortices. Out of the shapes considered in this study, trapezoidal cavities perform better than cavities with vertical walls in delaying the wetting transition due to geometrical squeezing of vortices toward the liquid-gas interface. Numerical simulations corroborate the experimental findings in that cavities with inclined walls exert more force on the liquid-gas interface, thus delaying their wetting transition. The proposed method being passive in nature appears more attractive than previous active methods.

Overview of C-2 field-reversed configuration experiment plasma diagnostics

A comprehensive diagnostic suite for field-reversed configuration (FRC) plasmas has been developed and installed on the C-2 device at Tri Alpha Energy to investigate the dynamics of FRC formation as well as to understand key FRC physics properties, e.g., confinement and stability, throughout a discharge. C-2 is a unique, large compact-toroid merging device that produces FRC plasmas partially sustained for up to ∼5 ms by neutral-beam (NB) injection and end-on plasma-guns for stability control. Fundamental C-2 FRC properties are diagnosed by magnetics, interferometry, Thomson scattering, spectroscopy, bolometry, reflectometry, and NB-related fast-ion/neutral diagnostics. These diagnostics (totaling >50 systems) are essential to support the primary goal of developing a deep understanding of NB-driven FRCs.

Magnetic diagnostic suite of the C-2 field-reversed configuration experiment confinement vessel

Magnetic measurements are a fundamental part of determining the size and shape of field-reversed configuration (FRC) plasmas in the C-2 device. The magnetic probe suite consists of 44 in-vessel and ex-vessel probes constructed using various technologies: ultra-high vacuum compatible mineral-insulated cable, nested triple axis coils hand-wound on ceramic bobbins, and commercial chip inductors mounted on printed circuit boards. Together, these probes measure the three-dimensional excluded flux profile of the FRC, which approximates the shape of the separatrix between the confined plasma volume and the scrape-off layer. High accuracy is achieved by using the extensive probe measurements to compensate for non-ideal effects such as flux leakage through the vacuum vessel and bulk motion of the FRC towards the wall. A subset of the probes is also used as a set of Mirnov arrays that provide sensitive detection of perturbations and oscillations of the FRC.

Internal magnetic field measurement on C-2 field-reversed configuration plasmas

A long-lived field-reversed configuration (FRC) plasma has been produced in the C-2 device by dynamically colliding and merging two oppositely directed, highly supersonic compact toroids (CTs). The reversed-field structure of the translated CTs and final merged-FRC state have been directly verified by probing the internal magnetic field structure using a multi-channel magnetic probe array near the midplane of the C-2 confinement chamber. Each of the two translated CTs exhibits significant toroidal fields (B(t)) with opposite helicity, and a relatively large B(t) remains inside the separatrix after merging.

Measurements of neutral density profiles using a deuterium Balmer-alpha diagnostic in the C-2 FRC plasma

In C-2 field-reversed configuration (FRC) device, low neutral density outside the FRC separatrix is required to minimize the charge exchange loss of fast particles. Titanium gettering is used in C-2 to reduce the wall recycling and keep the neutral density low in plasma edge. The measurements of neutral density radial profile are desirable to understand the plasma recycling and the effects of titanium gettering. These measurements are also needed to study the interaction of neutral beams with FRC plasma and confinement of fast ions. Diagnostic based on absolute deuterium Balmer-alpha (D-alpha) radiation measurements is developed and deployed on C-2 device to measure the radial profile of neutral density. Simultaneous measurements of electron density and temperature are done using CO(2) interferometer, Thomson scattering, and triple probes diagnostics along with absolute D-alpha radiation. Abel inversion was performed to get the time dependent radial profile of the local D-alpha emission density. Neutral density profiles are obtained under different machine conditions of titanium deposition.

Field reversed configuration confinement enhancement through edge biasing and neutral beam injection

Field reversed configurations (FRCs) with high confinement are obtained in the C-2 device by combining plasma gun edge biasing and neutral beam injection. The plasma gun creates an inward radial electric field that counters the usual FRC spin-up. The n = 2 rotational instability is stabilized without applying quadrupole magnetic fields. The FRCs are nearly axisymmetric, which enables fast ion confinement. The plasma gun also produces E × B shear in the FRC edge layer, which may explain the observed improved particle transport. The FRC confinement times are improved by factors 2 to 4, and the plasma lifetimes are extended from 1 to up to 4 ms.

The all-ceramic, inlay supported fixed partial denture. Part 3. Experimental approach for validating the finite element analysis

In a previous study, the authors used a finite element analysis (FEA) to evaluate the stresses developed during the loading of an all-ceramic, inlay supported fixed partial denture and compared it with the more traditional full crown supported prosthesis. To date there has been little research into correlating the responses of the numerical model against physical mechanical tests; such validation analysis is crucial if the results from the FEA are to be confidently relied upon. This study reports on the experimental methods used to compare with the FEA and thereby to validate the predictive fracture behaviour of the numerical model. This study also outlines the methods for manufacture and testing of the ceramic structure along with observations of the fracture tests. In addition the procedure used for developing the FEA model for the test system is outlined.

The all-ceramic, inlay supported fixed partial denture. Part 2. Fixed partial denture design: a finite element analysis

The clinical use of all-ceramic crowns and fixed partial dentures has seen widespread adoption over the past few years due to their increasing durability and longevity. However, the application of inlays as an abutment design has not been as readily embraced because of their relatively high failure rates. With the use of an idealized inlay preparation design and prosthesis form which better distributes the tensile stresses, it is possible to utilize the inlay as support for an all-ceramic fixed partial denture. Utilizing a three-dimensional finite element analysis, a direct comparison of the inlay supported all-ceramic bridge against the traditional full crown supported all-ceramic bridge is made. The results demonstrate that peak stresses in the inlay bridge are around 20% higher than in the full crown supported bridge with von Mises peaking at about 730 MPa when subjected to theoretical average maximum bite force in the molar region of 700 N, which is similar to the ultimate tensile strengths of current zirconia based ceramics.

Dynamic formation of a hot field reversed configuration with improved confinement by supersonic merging of two colliding high-β compact toroids

A hot stable field-reversed configuration (FRC) has been produced in the C-2 experiment by colliding and merging two high-β plasmoids preformed by the dynamic version of field-reversed θ-pinch technology. The merging process exhibits the highest poloidal flux amplification obtained in a magnetic confinement system (over tenfold increase). Most of the kinetic energy is converted into thermal energy with total temperature (T{i}+T{e}) exceeding 0.5 keV. The final FRC state exhibits a record FRC lifetime with flux confinement approaching classical values. These findings should have significant implications for fusion research and the physics of magnetic reconnection.

Breakdown limits on Gigavolt-per-meter electron-beam-driven wakefields in dielectric structures

First measurements of the breakdown threshold in a dielectric subjected to GV/m wakefields produced by short (30-330 fs), 28.5 GeV electron bunches have been made. Fused silica tubes of 100 microm inner diameter were exposed to a range of bunch lengths, allowing surface dielectric fields up to 27 GV/m to be generated. The onset of breakdown, detected through light emission from the tube ends, is observed to occur when the peak electric field at the dielectric surface reaches 13.8+/-0.7 GV/m. The correlation of structure damage to beam-induced breakdown is established using an array of postexposure inspection techniques.

Effects of ion motion in intense beam-driven plasma wakefield accelerators

Recent proposals for using plasma wakefield accelerators (PWFA) as a component of a linear collider have included intense electron beams with densities many times in excess of the plasma density. The beam's electric fields expel the plasma electrons from the beam path to many beam radii in this regime. We analyze here the motion of plasma ions under the beam fields, and find for a proposed PWFA collider scenario that the ions completely collapse inside of the beam. Simulations of ion collapse are presented. Implications of ion motion on the feasibility of the PWFA-based colliders are discussed.

Plaque removal efficacy of two electric toothbrushes with different brush head designs

OBJECTIVES.: To compare the safety and plaque removal efficacy of two electric toothbrushes, one a rechargeable oscillating/pulsating toothbrush with a small round brush head (Oral-B ProfessionalCaretrade mark 7000; PC 7000), the other a battery-operated toothbrush with a dual moving brush head (Crest(R) SpinBrushtrade mark Pro; SBP). METHODS.: The study had a randomised, examiner-blind, two-arm crossover design. All subjects received an oral prophylaxis and used both toothbrushes on alternating days for a two-week practice period. After abstaining from all oral hygiene procedures for 23-25 hours, subjects received an oral tissue examination and those with pre-brushing whole mouth mean plaque scores >/=0.60 measured by the Rustogi et al. Modified Navy Plaque Index were randomly assigned to treatment sequence. Subjects brushed with their assigned toothbrush for 2 minutes using a commercially available dentifrice. Oral tissues were then re-examined and post-brushing plaque scores recorded. After a brief washout period, the above procedures were repeated with the alternate toothbrush. One examiner, blinded to the treatment sequence, performed all clinical measurements. RESULTS.: A total of 70 subjects (24 males and 46 females) were enrolled and completed the study. Each toothbrush was found to be safe and significantly reduced plaque levels after a single brushing. The PC 7000 was significantly more effective in plaque removal than the SBP at all tooth areas, reducing whole mouth plaque by 61% versus 58% and plaque from approximal surfaces by 69% versus 65%, respectively. CONCLUSIONS.: The action of the oscillating/pulsating toothbrush with a small round brush head, Oral-B ProfessionalCare 7000, is more effective in plaque removal than the battery-operated Crest SpinBrush Pro toothbrush with a larger dual moving brush head.

Single-use plaque removal efficacy of three power toothbrushes

OBJECTIVES.: To compare the safety and plaque removal efficacy of two oscillating/rotating/pulsating toothbrushes (Oral-B ProfessionalCaretrade mark 7000 [PC 7000] and Oral-B 3D Excel [3DE]) and a high-frequency toothbrush (Sonicare(R) Advance, Philips Oral Healthcare; SA) in a single-use, examiner-blind, three period crossover study. METHODS.: After refraining from all oral hygiene procedures for 23-25 hours, subjects received an oral tissue examination and those with pre-brushing whole mouth mean plaque scores 0.6 based on the Rustogi et al. Modified Navy Plaque Index were randomly assigned to treatment sequence. After brushing with the assigned toothbrush and a commercially available dentifrice for 2 minutes, oral tissues were then re-examined and post-brushing plaque scores recorded. Following a brief washout period between two additional visits, the above procedures were repeated with the two alternate toothbrushes. One examiner, blinded to the treatment sequence, performed all clinical measurements. RESULTS.: A total of 79 subjects (28 males and 51 females) were enrolled and completed the study. Each toothbrush was found to be safe and significantly reduced plaque levels after a single brushing. The PC 7000 and 3DE were equally more effective in plaque removal than the SA, at all tooth areas, reducing plaque by 59.0%, 59.7% and 51.8%, respectively on whole mouth surfaces, and by 67.5%, 67.8% and 59.4%, respectively on approximal surfaces. CONCLUSIONS.: The action of the oscillating/rotating/pulsating toothbrushes (Oral-B ProfessionalCare 7000 and Oral-B 3D Excel) was more effective in plaque removal than the high-frequency toothbrush (Sonicare Advance).

Efficacy of a novel brush head in the comparison of two power toothbrushes on removal of plaque and naturally occurring extrinsic stain

OBJECTIVES

To compare the safety and efficacy of an oscillating/pulsating power toothbrush (Oral-B ProfessionalCareTM 7000; PC 7000) fitted with either the standard FlexiSoft (PC 7000/EB17) brush head or the novel Pro Polisher (PC 7000/ EB-Prophy) and a high-frequency toothbrush (Philips Sonicare Elite; SE), in their relative ability to remove plaque and naturally occurring extrinsic dental stain over a six-week period.

METHODS

This randomised, examiner-blind, parallel group study involved 90 healthy subjects from a general population. All subjects received a baseline plaque (Turesky et al. modified Quigley-Hein Plaque Index), stain (Lobene Stain Index) and tooth shade (VITAPAN Shade Guide) [Vita] assessment and an oral tissue examination. After training in the use of their randomly assigned device, subjects were instructed to brush twice daily for 2 min and returned after 3, 4 and 6 weeks of product use for a repeat of each clinical assessment.

RESULTS

Reductions from baseline in mean plaque and extrinsic dental stain scores were significant at Weeks 3, 4 and 6 in all three treatment groups. By Week 6, mean reductions from baseline in whole mouth plaque scores were 32%, 27% and 14% in the PC 7000/EB-Prophy, PC 7000/EB17 and SE groups, respectivety. For the body of the tooth, mean reductions from baseline at Week 6 in total stain were 89%, 89% and 80%, respectively. Between treatment group comparisons consistently revealed that the PC 7000 toothbrush plus the EB-Prophy or EB17 brush head removed significantly more plaque and extrinsic stain (total stain, stain area and stain intensity) than the SE toothbrush at 3, 4 and 6 weeks. The EB-Prophy group had a greater proportion of subjects showing a 2-3+ change in Vita shade scores at each time point compared to the other two brushes; at Week 6 the proportions were 67% in the PC 7000/EB-Prophy group, 30% in the PC 7000/EB17 group, and 7% in the SE group. The PC 7000/EB17, PC 7000/EB-Prophy and the SE were found to be safe as used in the study.

CONCLUSIONS

The oscillating/rotating/pulsating PC 7000 (fitted with either the standard EB17 or novel EB-Prophy brush head) is more effective at removal of plaque and naturally occurring extrinsic tooth stain, and the PC 7000 plus EB-Prophy in the improvement of tooth shade, than the high-frequency SE toothbrush.

Single-use plaque removal efficacy of three power toothbrushes

OBJECTIVES

To compare the safety and plaque removal efficacy of two oscillating/rotating/pulsating toothbrushes (Oral-B ProfessionalCare 7000 [PC 7000] and Oral-B 3D Excel [3DE]) and a high-frequency toothbrush (Sonicare Advance, Philips Oral Healthcare; SA) in a single-use, examiner-blind, three period crossover study.

METHODS

After refraining from all oral hygiene procedures for 23-25 hours, subjects received an oral tissue examination and those with pre-brushing whole mouth mean plaque scores > or = 0.6 based on the Rustogi et al. Modified Navy Plaque Index were randomly assigned to treatment sequence. After brushing with the assigned toothbrush and a commercially available dentifrice for 2 minutes, oral tissues were then re-examined and post-brushing plaque scores recorded. Following a brief washout period between two additional visits, the above procedures were repeated with the two alternate toothbrushes. One examiner, blinded to the treatment sequence, performed all clinical measurements.

RESULTS

A total of 79 subjects (28 males and 51 females) were enrolled and completed the study. Each toothbrush was found to be safe and significantly reduced plaque levels after a single brushing. The PC 7000 and 3DE were equally more effective in plaque removal than the SA, at all tooth areas, reducing plaque by 59.0%, 59.7% and 51.8%, respectively on whole mouth surfaces, and by 67.5%, 67.8% and 59.4%, respectively on approximal surfaces.

CONCLUSIONS

The action of the oscillating/rotating/pulsating toothbrushes (Oral-B ProfessionalCare 7000 and Oral-B 3D Excel) was more effective in plaque removal than the high-frequency toothbrush (Sonicare Advance).

Three-month assessment of safety and efficacy of two electric toothbrushes

OBJECTIVE.: This randomised, examiner-blind parallel group study was designed to evaluate the safety and efficacy of a rechargeable oscillating/pulsating toothbrush (Oral-B ProfessionalCaretrade mark 7000, Oral-B Laboratories; PC 7000) and a battery-operated toothbrush (Crest(R) SpinBrushtrade mark Pro, Procter & Gamble Company; SBP) in the reduction of gingivitis, bleeding and plaque over a 3-month period. METHODS.: After 12-18 hours of no oral hygiene, subjects had oral tissue examinations, and gingival and plaque assessments to determine eligibility in the study. Subjects were stratified and randomised into treatment groups based on initial whole mouth mean plaque (Turesky modification of Quigley Hein Plaque Index) and gingivitis (Löe & Silness Gingival Index) scores and gender. Subjects were instructed to brush twice daily with their assigned toothpaste and toothbrush. Clinical parameters were assessed at baseline, and after 1 and 3 months of use. Within treatment comparisons from baseline were analysed using t-test; between treatment comparisons were analysed using ANOVA. RESULTS.: Data were obtained from 92 subjects (PC 7000 n=45; SBP n=47). No significant differences were found in baseline plaque, gingivitis and bleeding between groups. Both treatment groups had significant reductions from baseline in plaque, gingivitis and bleeding scores. PC 7000 demonstrated significantly greater reductions compared to SBP in whole mouth plaque at 1 month: 0.39+/-0.43 vs. 0.16+/-0.42 and 3 months: 0.32+/-0.48 vs. 0.04+/-0.41. PC 7000 also demonstrated significant reductions compared to SBP in gingivitis at 3 months for whole mouth: 0.14+/-0.09 vs. 0.10+/-0.10 and approximal areas: 0.11+/-0.08 vs. 0.08+/-0.09. There were no significant differences between toothbrushes in bleeding at either time point. Safety examinations revealed no apparent difference in soft and hard tissue abnormalities between groups. CONCLUSION.: The PC 7000 toothbrush demonstrated significantly greater reductions in plaque and gingivitis compared to the SPB over a 3-month period.

Efficacy of a novel brush head in the comparison of two power toothbrushes on removal of plaque and naturally occurring extrinsic stain

OBJECTIVES.: To compare the safety and efficacy of an oscillating/pulsating power toothbrush (Oral-B ProfessionalCaretrade mark 7000; PC 7000) fitted with either the standard FlexiSoft (PC 7000/EB17) brush head or the novel Pro Polisher (PC 7000/EB-Prophy) and a high-frequency toothbrush (Philips Sonicare(R) Elite(R); SE), in their relative ability to remove plaque and naturally occurring extrinsic dental stain over a six-week period. METHODS.: This randomised, examiner-blind, parallel group study involved 90 healthy subjects from a general population. All subjects received a baseline plaque (Turesky et al. modified Quigley-Hein Plaque Index), stain (Lobene Stain Index) and tooth shade (VITAPAN(R) Shade Guide) [Vita] assessment and an oral tissue examination. After training in the use of their randomly assigned device, subjects were instructed to brush twice daily for 2 min and returned after 3, 4 and 6 weeks of product use for a repeat of each clinical assessment. RESULTS.: Reductions from baseline in mean plaque and extrinsic dental stain scores were significant at Weeks 3, 4 and 6 in all three treatment groups. By Week 6, mean reductions from baseline in whole mouth plaque scores were 32%, 27% and 14% in the PC 7000/EB-Prophy, PC 7000/EB17 and SE groups, respectively. For the body of the tooth, mean reductions from baseline at Week 6 in total stain were 89%, 89% and 80%, respectively. Between treatment group comparisons consistently revealed that the PC 7000 toothbrush plus the EB-Prophy or EB17 brush head removed significantly more plaque and extrinsic stain (total stain, stain area and stain intensity) than the SE toothbrush at 3, 4 and 6 weeks. The EB-Prophy group had a greater proportion of subjects showing a 2-3+ change in Vita shade scores at each time point compared to the other two brushes; at Week 6 the proportions were 67% in the PC 7000/EB-Prophy group, 30% in the PC 7000/EB17 group, and 7% in the SE group. The PC 7000/EB17, PC 7000/EB-Prophy and the SE were found to be safe as used in the study. CONCLUSIONS.: The oscillating/rotating/pulsating PC 7000 (fitted with either the standard EB17 or novel EB-Prophy brush head) is more effective at removal of plaque and naturally occurring extrinsic tooth stain, and the PC 7000 plus EB-Prophy in the improvement of tooth shade, than the high-frequency SE toothbrush.

Three-month assessment of safety and efficacy of two electric toothbrushes

OBJECTIVE

This randomised, examiner-blind parallel group study was designed to evaluate the safety and efficacy of a rechargeable oscillating/pulsating toothbrush (Oral-B ProfessionalCare 7000, Oral-B Laboratories; PC 7000) and a battery-operated toothbrush (Crest SpinBrush Pro, Procter & Gamble Company; SBP) in the reduction of gingivitis, bleeding and plaque over a 3-month period.

METHODS

After 12-18 hours of no oral hygiene, subjects had oral tissue examinations, and gingival and plaque assessments to determine eligibility in the study. Subjects were stratified and randomised into treatment groups based on initial whole mouth mean plaque (Turesky modification of Quigley Hein Plaque Index) and gingivitis (Löe & Silness Gingival Index) scores and gender. Subjects were instructed to brush twice daily with their assigned toothpaste and toothbrush. Clinical parameters were assessed at baseline, and after 1 and 3 months of use. Within treatment comparisons from baseline were analysed using t-test; between treatment comparisons were analysed using ANOVA.

RESULTS

Data were obtained from 92 subjects (PC 7000 n=45; SBP n=47). No significant differences were found in baseline plaque, gingivitis and bleeding between groups. Both treatment groups had significant reductions from baseline in plaque, gingivitis and bleeding scores. PC 7000 demonstrated significantly greater reductions compared to SBP in whole mouth plaque at 1 month: 0.39 +/- 0.43 vs. 0.16 +/- 0.42 and 3 months: 0.32 +/- 0.48 vs. 0.04 +/- 0.41. PC 7000 also demonstrated significant reductions compared to SBP in gingivitis at 3 months for whole mouth: 0.14 +/- 0.09 vs. 0.10 +/- 0.10 and approximal areas: 0.11 +/- 0.08 vs. 0.08 +/- 0.09. There were no significant differences between toothbrushes in bleeding at either time point: Safety examinations revealed no apparent difference in soft and hard tissue abnormalities between groups.

CONCLUSION

The PC 7000 toothbrush demonstrated significantly greater reductions in plaque and gingivitis compared to the SPB over a 3-month period.

Plaque removal efficacy of two electric toothbrushes with different brush head designs

OBJECTIVES

To compare the safety and plaque removal efficacy of two electric toothbrushes, one a rechargeable oscillating/pulsating toothbrush with a small round brush head (Oral-B ProfessionalCare 7000; PC 7000), the other a battery-operated toothbrush with a dual moving brush head (Crest SpinBrush Pro; SBP).

METHODS

The study had a randomised, examiner-blind, two-arm crossover design. All subjects received an oral prophylaxis and used both toothbrushes on alternating days for a two-week practice period. After abstaining from all oral hygiene procedures for 23-25 hours, subjects received an oral tissue examination and those with pre-brushing whole mouth mean plaque scores > or = 0.60 measured by the Rustogi et al. Modified Navy Plaque Index were randomly assigned to treatment sequence. Subjects brushed with their assigned toothbrush for 2 minutes using a commercially available dentifrice. Oral tissues were then re-examined and post-brushing plaque scores recorded. After a brief washout period, the above procedures were repeated with the alternate toothbrush. One examiner, blinded to the treatment sequence, performed all clinical measurements.

RESULTS

A total of 70 subjects (24 males and 46 females) were enrolled and completed the study. Each toothbrush was found to be safe and significantly reduced plaque levels after a single brushing. The PC 7000 was significantly more effective in plaque removal than the SBP at all tooth areas, reducing whole mouth plaque by 61% versus 58% and plaque from approximal surfaces by 69% versus 65%, respectively.

CONCLUSIONS

The action of the oscillating/pulsating toothbrush with a small round brush head, Oral-B ProfessionalCare 7000, is more effective in plaque removal than the battery-operated Crest SpinBrush Pro toothbrush with a larger dual moving brush head.

Horizontal phase-space distortions arising from magnetic pulse compression of an intense, relativistic electron beam

We report detailed measurements of the transverse phase space distortions induced by magnetic chicane compression of a high brightness, relativistic electron beam to subpicosecond length. A strong bifurcation in the phase space is observed when the beam is strongly compressed. This effect is analyzed using several computational models and is correlated to the folding of longitudinal phase space. The impact of these results on current research in collective beam effects in bending systems and implications for future short wavelength free-electron lasers and linear colliders are discussed.

Anatomic study of the medial neurovascular structures in relation to calcaneal osteotomy

Medial displacement osteotomy of the calcaneous is commonly performed for stage II posterior tibial tendon insufficiency in an effort to improve the valgus deformity of the hindfoot. We performed an anatomic study examining the medial neurovascular anatomy and its relation to the osteotomy in an attempt to determine which structures may be at risk during the procedure. Calcaneal osteotomies were performed through a lateral approach on 22 fresh-frozen cadaver below-knee specimens. Dissection was then performed medially to identify the Medial Plantar Nerve (MPN), the Lateral Plantar Nerve (LPN), the Posterior Tibial Artery (PTA), and their respective branches. Measurements determined either 1) where the structure crossed the osteotomy or 2) if the structure did not cross, the closest perpendicular distance from the osteotomy and at which point along its length this occurred. Perpendicular distances were recorded in millimeters and position along the osteotomy as a percentage of the total length from the posterosuperior aspect. An average of four neurovascular structures crossed each osteotomy site (range 2 to 6), most of which were branches of the LPN or the PTA. The MPN did not cross in any of the specimens studied, the LPN crossed in one specimen, and the PTA crossed in two specimens. The MPN distributed no crossing branches. The calcaneal sensory branch of the LPN was identified and crossed in 86% of the cadavers at 19% (+/- 15%) along the osteotomy length. A more distal second branch of the LPN (Baxter's nerve) was identified and crossed in 95% of the specimens at 61% (+/ 20%) along the osteotomy length. A third crossing branch existed in one specimen. Each PTA distributed from zero to three branches which variably crossed the osteotomy at a point from 2% to 100% along its length. The PTA bifurcated in 77% of the specimens at 49% (+/- 9%) along the osteotomy length. A consistent finding in every specimen was the presence of two veins accompanying the PTA with one on either side. A number of medial neurovascular structures may be at risk when perfoming a calcaneal osteotomy through a lateral approach. A minimum of two structures crossed the osteotomy site at variable positions in this study, although most of these structures represented branches off of the LPN or the PTA, with the LPN and the PTA themselves crossing only infrequently. The authors recommend that the completion of the osteotomy through the medial calcaneal cortex be performed in a carefully controlled manner to reduce the risk of post-operative complications including pain, numbness, and hematoma formation.