Active fast ion charge exchange measurements using a neutral particle analyzer and multiple beam species in C-2W.

In order to measure the fast ion using neutral particle analyzers (NPAs) in the low neutral density core region of a magnetic confinement fusion device, active change exchange measurements are often performed using a neutral beam (NB) as a charge-exchange (CX) target. One of the complications with this approach is that an NB injected as a CX target can also contribute to the total fast ion source. C-2W has a unique solution to this difficulty in that it is equipped with both eight NB injectors, which can inject beams of different particle species, and an electro-magnetic NPA (EM-NPA), which can measure multiple ion species simultaneously. This enables the active and passive fast ion CX components to be clearly distinguished. The decrease in amplitude of the CX spectra when a hydrogen NB is terminated was clearly observed by the EM-NPA in both hydrogen and deuterium channels. This reduction of observed fast ion flux was mainly caused by the diminished fast ion source, not crosstalk or a general reduction in fast ion confinement. As an example application of this technique on C-2W, fast ion behavior during a periodic density drop is explored. The large difference between the active and passive CX components of the EM-NPA signals clearly demonstrates the usefulness of the active fast ion CX measurement.

A novel technique for in situ calibration of the C-2W electromagnetic neutral particle analyzer utilizing machine learning.

In TAE Technologies' current experimental device, C-2W, neutral beam injection creates a large fast ion population that sustains a field-reversed configuration (FRC) plasma. Diagnosis of these fast ions is therefore critical for understanding the behavior of the FRC. Neutral Particle Analyzers (NPAs) are used to measure the energy spectrum of fast ions that charge exchange on background or beam neutrals and are lost from the plasma. To ensure correct diagnosis of the fast ion population, a calibration check of the NPAs was performed. A novel, generally applicable method for an in situ relative calibration of diagnostics on an unknown source with a small dataset was developed. The method utilizes a machine learning technique, Generalized Additive Models (GAMs), to reconstruct the diagnostic source distribution, and Stochastic Gradient Descent (SGD) to determine the NPA channel calibration factors. The results on both synthetic and experimental datasets are presented.

A mass resolved, high resolution neutral particle analyzer for C-2U.

C-2U is a high-confinement, advanced beam driven field-reversed configuration plasma experiment which sustains the configuration for >5 ms, in excess of typical MHD and fast particle instability times, as well as fast particle slowing down times. Fast particle dynamics are critical to C-2U performance and several diagnostics have been deployed to characterize the fast particle population, including neutron and proton detectors. To increase our understanding of fast particle behavior and supplement existing diagnostics, an E ∥ B neutral particle analyzer was installed, which simultaneously measures H0 and D0 flux with large dynamic range and high energy resolution. Here we report the commissioning of the E ∥ B analyzer, confirm the instrument has energy resolution ΔE/E≲0.1 and a dynamic range Emax/Emin∼30, and present measurements of initial testing on C-2U.

Absolute calibration of neutron detectors on the C-2U advanced beam-driven FRC.

In the C-2U fusion energy experiment, high power neutral beam injection creates a large fast ion population that sustains a field-reversed configuration (FRC) plasma. The diagnosis of the fast ion pressure in these high-performance plasmas is therefore critical, and the measurement of the flux of neutrons from the deuterium-deuterium (D-D) fusion reaction is well suited to the task. Here we describe the absolute, in situ calibration of scintillation neutron detectors via two independent methods: firing deuterium beams into a high density gas target and calibration with a 2 × 107 n/s AmBe source. The practical issues of each method are discussed and the resulting calibration factors are shown to be in good agreement. Finally, the calibration factor is applied to C-2U experimental data where the measured neutron rate is found to exceed the classical expectation.

Fusion proton diagnostic for the C-2 field reversed configuration.

Measurements of the flux of fusion products from high temperature plasmas provide valuable insights into the ion energy distribution, as the fusion reaction rate is a very sensitive function of ion energy. In C-2, where field reversed configuration plasmas are formed by the collision of two compact toroids and partially sustained by high power neutral beam injection [M. Binderbauer et al., Phys. Rev. Lett. 105, 045003 (2010); M. Tuszewski et al., Phys. Rev. Lett. 108, 255008 (2012)], measurements of DD fusion neutron flux are used to diagnose ion temperature and study fast ion confinement and dynamics. In this paper, we will describe the development of a new 3 MeV proton detector that will complement existing neutron detectors. The detector is a large area (50 cm(2)), partially depleted, ion implanted silicon diode operated in a pulse counting regime. While the scintillator-based neutron detectors allow for high time resolution measurements (∼100 kHz), they have no spatial or energy resolution. The proton detector will provide 10 cm spatial resolution, allowing us to determine if the axial distribution of fast ions is consistent with classical fast ion theory or whether anomalous scattering mechanisms are active. We will describe in detail the diagnostic design and present initial data from a neutral beam test chamber.

A photodiode-based neutral particle bolometer for characterizing charge-exchanged fast-ion behavior.

A neutral particle bolometer (NPB) has been designed and implemented on Tri Alpha Energy's C-2 device in order to spatially and temporally resolve the charge-exchange losses of fast-ion populations originating from neutral beam injection into field-reversed configuration plasmas. This instrument employs a silicon photodiode as the detection device with an integrated tungsten filter coating to reduce sensitivity to light radiation. Here we discuss the technical aspects and calibration of the NPB, and report typical NPB measurement results of wall recycling effects on fast-ion losses.

Modulated active charge exchange fast ion diagnostic for the C-2 field-reversed configuration experiment.

A diagnostic technique for measuring the fast-ion energy distribution in a field-reversed configuration plasma was developed and tested on the C-2 experiment. A deuterium neutral beam modulated at 22 kHz is injected into the plasma, producing a localized charge-exchange target for the confined fast protons. The escaping fast neutrals are detected by a neutral particle analyzer. The target beam transverse size (∼15 cm) defines the spatial resolution of the method. The equivalent current density of the target beam is ≤0.15 A/cm(2), which corresponds to a neutral density (∼6 × 10(9) cm(-3)) that highly exceeds the background neutral density in the core of C-2. The deuterium fast-ions due to the target beam (E ∼27 keV), are not confined in C-2 and thus make a negligible contribution to the measured signals.

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.

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

A hot stable field-reversed configuration (FRC) has been produced in the C-2 experiment by colliding and merging two high-ß 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.

Improved spiral tube assembly for high-speed counter-current chromatography.

The original spiral tube support (STS) assembly is improved by changing the shape of the tubing, with 1-cm presses perpendicularly along the length. This modification interrupts the laminar flow of the mobile phase. The tubing in the four return grooves to the center of the rotor is flattened by a specially made pressing tool to increase the number of spiral layers and decrease the dead space volume, thus increasing the column efficiency. The performance of this spiral tube assembly was tested in separations of dipeptides and proteins with suitable polar two-phase solvent systems. The results revealed that the present system yields high partition efficiency with a satisfactory level of stationary phase retention in a short elution time. The present high-speed counter-current chromatographic (HSCCC) system will be efficiently applied to a broad spectrum of two-phase solvent systems including aqueous-aqueous polymer phase systems (TPAS) which are used for separation of biopolymers such as proteins and nucleic acids.

Spiral Tube Assembly for High-Speed Countercurrent Chromatography: Choice of Elution Modes for Four Typical Two-Phase Solvent Systems.

Optimal elution modes were determined for four typical two-phase solvent systems each with different physical parameters to achieve the best peak resolution and retention of the stationary phase by spiral tube high-speed countercurrent chromatography using a suitable set of test samples. Both retention of the stationary phase and partition efficiency are governed by an interplay between two forces, i.e., Archimedean Screw force and radial centrifugal force gradient of the spiral channel. In the polar solvent system represented by 1-butanol./acetic acid/water (4:1:5, v/v/v) with settling time of over 30 s, the effect by the radial centrifugal gradient force dominates giving the best separation of dipeptides either by pumping the lower phase from the inner terminal or the upper phase from the outer terminal of the spiral channel. In the moderately hydrophobic two-phase solvent system represented by hexane/ethyl acetate/methanol/0.1 M HCl (1:1:1:1) with settling time of 19 s, and two hydrophobic solvent systems of hexane/ethanol/water (5:4:1, v/v/v) and non-aqueous binary system of hexane/acetonitrile both having settling time of 9, the effect of the Archimedean screw force play a major role in hydrodynamic equilibrium, giving the best separations by pumping the lower phase from the head or the upper phase from the tail of the spiral channel.

SRM 2460/2461 Standard Bullets and Casings Project.

The National Institute of Standards and Technology Standard Reference Material (SRM) 2460/2461 standard bullets and casings project will provide support to firearms examiners and to the National Integrated Ballistics Information Network (NIBIN) in the United States. The SRM bullet is designed as both a virtual and a physical bullet profile signature standard. The virtual standard is a set of six digitized bullet profile signatures originally traced from six master bullets fired at the Bureau of Alcohol, Tobacco and Firearms (ATF) and the Federal Bureau of Investigation (FBI). By using the virtual signature standard to control the tool path on a numerically controlled diamond turning machine, 40 SRM bullets were produced. A profile signature measurement system was established for the SRM bullets. The profile signature differences are quantified by the maximum of the cross correlation function and by the signature difference between pairs of compared profile signatures measured on different SRM bullets. Initial measurement results showed high reproducibility for both the measurement system and production process of the SRM bullets. A traceability scheme has been proposed to establish the measurement traceability for nationwide bullet signature measurements to NIST, ATF and FBI. Prototype SRM casings have also been developed.

Bacteria in the middle ear and nasopharynx during tympanostomy tube insertion.

PURPOSE: To evaluate the efficacy of nasopharyngeal cultures in identifying pathogens in middle-ear effusions as an alternative to cultures obtained through tympanocentesis. MATERIALS AND METHODS: The study population consisted of 203 children with middle-ear effusions at the time of placement of tympanostomy tubes for recurrent otitis media or persistent otitis media with effusion. Isolates from the nasopharynx were compared with those from the middle ear to determine sensitivity, specificity, and predictive values for each of the three main pathogens. RESULTS: The predominant bacterial isolates from both ear and nasopharynx were Streptococcus pneumoniae, Moraxella catarrhalis, and Haemophilus influenzae. Eighty-one percent (42% highly, 39% relatively) S pneumoniae nasopharyngeal isolates were resistant to penicillin. The negative predictive value of the nasopharyngeal cultures was at least 97% for each of these predominant bacteria. CONCLUSION: This study supports the conclusion that tympanocentesis is the most useful means of identifying pathogens in otitis media.

Utility of conventional radiography in the diagnosis and management of pediatric airway foreign bodies.

Pediatric airway foreign bodies are potentially life-threatening situations. The otolaryngologist is often consulted to aid in the diagnosis and management of these difficult cases. Although radiographic studies are often obtained, the decision for surgical intervention is usually based on a suspicious history and physical examination. Our hypothesis is that radiographic imaging should not alter the decision for surgical intervention. We retrospectively reviewed the cases of pediatric airway foreign bodies managed by the otolaryngology department at St Louis Children's Hospital between December 1990 and June 1996 with both radiographic imaging and operative intervention. Ninety-three cases of potential aspiration were identified, with a median patient age of 20 months. The most common presenting signs and symptoms were aspiration event (n = 82), wheezing (n = 76), decreased breath sounds (n = 47), cough (n = 39), respiratory distress (n = 17), fever (n = 16), pneumonia (n = 14), and stridor (n = 7). At the time of endoscopy, 73 patients were found to have an airway foreign body. The sensitivity and specificity of the imaging studies in identifying the presence of an airway foreign body in the 93 patients were 73% and 45%, respectively. Our decision for operative intervention was based on the history and physical examination, and was not changed in the presence of a negative radiographic study. The routine use of radiography should not alter the management of airway foreign bodies, providing that there is a well-equipped endoscopic team familiar with airway foreign bodies.

Identification of noise sources that influence distortion product otoacoustic emission measurements in human neonates.

OBJECTIVE: The objective of this study was to identify individual sources of noise and their contribution to the overall noise that influences valid measurement of otoacoustic emissions in neonates. The hypothesis was that careful selection of eliciting signals and signal processing parameters, unique analysis of measured results, and control of certain subject characteristics would allow isolation of these individual noise sources and determine their relative influence. DESIGN: Eliciting signal parameters were optimized and held constant to minimize equipment noise. Analysis of noise floors in relation to signal level was used to identify equipment-related noise associated with changes in signal parameters. Analysis of noise floor distributions was used to determine whether environmental noise entered the measurements via inadequate coupling of the probe to the ear. The acoustic characteristics of the middle ear were varied via subject selection to determine the influence of middle-ear characteristics on noise floor levels. RESULTS: The two sources of noise associated with the measurement equipment need not contribute to the noise floor for biologically relevant otoacoustic emissions measurements (eliciting signal levels between 30 and 75 dB SPL). Of the two pathways identified for environmental noise, the pathway resulting from an inadequate seal between the probe and the ear canal can be eliminated. One of the two sources of noise related to the subject, noise resulting from biologic activity unrelated to the ear can be minimized. However, the remaining factor, the status of the middle ear, has been shown to contribute as much as 6 dB to the overall noise floor. CONCLUSIONS: Careful selection of signal parameters and additional data analyses and procedural variables can isolate or control several sources of noise that influence distortion product otoacoustic emission measurements in neonates. Tight coupling between the probe unit and the external ear canal should be maintained for all measurements. Middle ear abnormalities can increase noise floors up to 6 dB.

Analysis of voice outcomes in pediatric patients following surgical procedures for laryngotracheal stenosis.

OBJECTIVE: To evaluate long-term (> 2 years) voice function and corresponding anatomical features in children who have undergone augmentation procedures for laryngotracheal stenosis. DESIGN: Follow-up survey assessment. SETTING: Academic pediatric referral center. PATIENTS OR OTHER PARTICIPANTS: The families of 50 patients were contacted by mail, and completed home questionnaires. Of these 50 patients, 33 agreed to participate in a comprehensive hospital-based voice assessment, and 28 of these underwent fiberoptic endoscopy. INTERVENTIONS: Hospital-based evaluation and parental questionnaire. MAIN OUTCOME MEASURES: (1) Perceptual voice assessment from taped samples by using the Vocal Profile Analysis protocol performed by 3 speech and language therapists, (2) fiberoptic laryngeal endoscopy assessment performed by 3 otolaryngologists, and (3) parental assessment of voice by questionnaire. The conditions of the patients were categorized by etiology, the degree of stenosis, coexisting laryngeal lesions, and the type of surgical procedure that was done based on a review of medical records. RESULTS: Eight of 33 patients were judged perceptually by using an amended version of the Vocal Profile Analysis scheme to have "normal" voices. In the remaining 25 patients, abnormalities were demonstrated in the parameters, including harshness (52%), whisper (36%), ventricular band phonation (21%), continuity (27%), mean pitch (27%), and falsetto voice (12%). By using endoscopy, 3 of 25 larynges were judged to be anatomically normal. Abnormalities that were found in the other patients included altered vocal fold mobility (42%), abnormal subglottis (38%), supraglottic vibration (31%), and anterior commissure blunting (31%). Supraglottic vibration corresponded with the perceptual judgment "ventricular band phonation type," and was seen in children with glottic insufficiency. Only 12% of parents indicated by questionnaire that deterioration of voice and dissatisfaction with voice function occurred after surgical procedures were performed. CONCLUSIONS: A substantial proportion of children who have undergone laryngotracheal surgical procedures for stenosis demonstrate chronic voice and endoscopic abnormalities. The effects of these surgical procedures and preexisting laryngeal abnormalities on voice continue to be difficult to establish in the pediatric population. Careful management by speech and language therapists who are familiar with such children is essential for optimal voice function.

Auricular cartilage versus costal cartilage as a grafting material in experimental laryngotracheal reconstruction.

Auricular cartilage has been used clinically as an alternative material to costal cartilage for implantation during laryngotracheal reconstructive surgery. Little information is available concerning the healing characteristics or the durability of these two types of graft. The authors of this study examined the rate of epithelialization and the survival of cartilage in a rabbit model of anterior tracheal wall reconstruction and directly compared auricular and costal cartilage grafts. Auricular cartilage was found to epithelialize faster than costal cartilage. Both types of graft survived well after implantation. The superior healing characteristics of auricular cartilage make it a desirable material for laryngotracheal reconstruction.