X-ray self-emission imaging with spherically bent Bragg crystals on the Z-machine.

An x-ray imaging scheme using spherically bent crystals was implemented on the Z-machine to image x rays emitted by the hot, dense plasma generated by a Magnetized Liner Inertial Fusion (MagLIF) target. This diagnostic relies on a spherically bent crystal to capture x-ray emission over a narrow spectral range (<15 eV), which is established by a limiting aperture placed on the Rowland circle. The spherical crystal optic provides the necessary high-throughput and large field-of-view required to produce a bright image over the entire, one-cm length of the emitting column of a plasma. The average spatial resolution was measured and determined to be 18 µm for the highest resolution configuration. With this resolution, the radial size of the stagnation column can be accurately determined and radial structures, such as bifurcations in the column, are clearly resolved. The success of the spherical-crystal imager has motivated the implementation of a new, two-crystal configuration for identifying sources of spectral line emission using a differential imaging technique.

Radiation, optical, power flow, and electrical diagnostics at the Z facility: Layout and techniques utilized to operate in the harsh environment.

The Z machine is a current driver producing up to 30 MA in 100 ns that utilizes a wide range of diagnostics to assess accelerator performance and target behavior conduct experiments that use the Z target as a source of radiation or high pressures. We review the existing suite of diagnostic systems, including their locations and primary configurations. The diagnostics are grouped in the following categories: pulsed power diagnostics, x-ray power and energy, x-ray spectroscopy, x-ray imaging (including backlighting, power flow, and velocimetry), and nuclear detectors (including neutron activation). We will also briefly summarize the primary imaging detectors we use at Z: image plates, x-ray and visible film, microchannel plates, and the ultrafast x-ray imager. The Z shot produces a harsh environment that interferes with diagnostic operation and data retrieval. We term these detrimental processes "threats" of which only partial quantifications and precise sources are known. We summarize the threats and describe techniques utilized in many of the systems to reduce noise and backgrounds.

Background measurement methods for opacity experiments conducted at the Z facility.

Laboratory experiments typically test opacity models by measuring spectrally resolved transmission of a sample using bright backlight radiation. A potential problem is that any unaccounted background signal contaminating the spectrum will artificially reduce the inferred opacity. Methods developed to measure background signals in opacity experiments at the Sandia Z facility are discussed. Preliminary measurements indicate that backgrounds are 9%-11% of the backlight signal at wavelengths less than 10 Å. Background is thus a relatively modest correction for all Z opacity data published to date. Future work will determine how important background is at longer wavelengths.

Systematic Study of L-Shell Opacity at Stellar Interior Temperatures.

The first systematic study of opacity dependence on atomic number at stellar interior temperatures is used to evaluate discrepancies between measured and modeled iron opacity [J. E. Bailey et al., Nature (London) 517, 56 (2015)NATUAS0028-083610.1038/nature14048]. High-temperature (>180 eV) chromium and nickel opacities are measured with ±6%-10% uncertainty, using the same methods employed in the previous iron experiments. The 10%-20% experiment reproducibility demonstrates experiment reliability. The overall model-data disagreements are smaller than for iron. However, the systematic study reveals shortcomings in models for density effects, excited states, and open L-shell configurations. The 30%-45% underestimate in the modeled quasicontinuum opacity at short wavelengths was observed only from iron and only at temperature above 180 eV. Thus, either opacity theories are missing physics that has nonmonotonic dependence on the number of bound electrons or there is an experimental flaw unique to the iron measurement at temperatures above 180 eV.

A compact multi-plane broadband (0.5-17 keV) spectrometer using a single acid phthalate crystal.

Acid phthalate crystals such as KAP crystals are a method of choice to record x-ray spectra in the soft x-ray regime (E ∼ 1 keV) using the large (001) 2d = 26.63 Šspacing. Reflection from many other planes is possible, and knowledge of the 2d spacing, reflectivity, and resolution for these reflections is necessary to evaluate whether they hinder or help the measurements. Burkhalter et al. [J. Appl. Phys., 52, 4379 (1981)] showed that the (013) reflection has efficiency comparable to the 2nd order reflection (002), and it can overlap the main first order reflection when the crystal bending axis ( b -axis) is contained in the dispersion plane, thus contaminating the main (001) measurement in a convex crystal geometry. We present a novel spectrograph concept that makes these asymmetric reflections helpful by setting the crystal b -axis perpendicular to the dispersion plane. In such a case, asymmetric reflections do not overlap with the main (001) reflection and each reflection can be used as an independent spectrograph. Here we demonstrate an achieved spectral range of 0.8-13 keV with a prototype setup. The detector measurements were reproduced with a 3D ray-tracing code.

A Wolter imager on the Z machine to diagnose warm x-ray sources.

A new Wolter x-ray imager has been developed for the Z machine to study the emission of warm (>15 keV) x-ray sources. A Wolter optic has been adapted from observational astronomy and medical imaging, which uses curved x-ray mirrors to form a 2D image of a source with 5 × 5 × 5 mm3 field-of-view and measured 60-300-µm resolution on-axis. The mirrors consist of a multilayer that create a narrow bandpass around the Mo Kα lines at 17.5 keV. We provide an overview of the instrument design and measured imaging performance. In addition, we present the first data from the instrument of a Mo wire array z-pinch on the Z machine, demonstrating improvements in spatial resolution and a 350-4100× increase in the signal over previous pinhole imaging techniques.

X-ray intensity and source size characterizations for the 25 kV upgraded Manson source at Sandia National Laboratories.

At Sandia National Laboratories, the x-ray generator Manson source model 5 was upgraded from 10 to 25 kV. The purpose of the upgrade is to drive higher characteristics photon energies with higher throughput. In this work we present characterization studies for the source size and the x-ray intensity when varying the source voltage for a series of K-, L-, and M-shell lines emitted from Al, Y, and Au elements composing the anode. We used a 2-pinhole camera to measure the source size and an energy dispersive detector to monitor the spectral content and intensity of the x-ray source. As the voltage increases, the source size is significantly reduced and line intensity is increased for the three materials. We can take advantage of the smaller source size and higher source throughput to effectively calibrate the suite of Z Pulsed Power Facility crystal spectrometers.

Cross-calibration of Fuji TR image plate and RAR 2492 x-ray film to determine the response of a DITABIS Super Micron image plate scanner.

Fuji TR image plate is frequently used as a replacement detector medium for x-ray imaging and spectroscopy diagnostics at NIF, Omega, and Z facilities. However, the familiar Fuji BAS line of image plate scanners is no longer supported by the industry, and so a replacement scanning system is needed. While the General Electric Typhoon line of scanners could replace the Fuji systems, the shift away from photo stimulated luminescence units to 16-bit grayscale Tag Image File Format (TIFF) leaves a discontinuity when comparing data collected from both systems. For the purposes of quantitative spectroscopy, a known unit of intensity applied to the grayscale values of the TIFF is needed. The DITABIS Super Micron image plate scanning system was tested and shown to potentially rival the resolution and dynamic range of Kodak RAR 2492 x-ray film. However, the absolute sensitivity of the scanner is unknown. In this work, a methodology to cross calibrate Fuji TR image plate and the absolutely calibrated Kodak RAR 2492 x-ray film is presented. Details of the experimental configurations used are included. An energy dependent scale factor to convert Fuji TR IP scanned on a DITABIS Super Micron scanner from 16-bit grayscale TIFF to intensity units (i.e., photons per square micron) is discussed.

Measurement and models of bent KAP(001) crystal integrated reflectivity and resolution (invited).

The Advanced Light Source beamline-9.3.1 x-rays are used to calibrate the rocking curve of bent potassium acid phthalate (KAP) crystals in the 2.3-4.5 keV photon-energy range. Crystals are bent on a cylindrically convex substrate with a radius of curvature ranging from 2 to 9 in. and also including the flat case to observe the effect of bending on the KAP spectrometric properties. As the bending radius increases, the crystal reflectivity converges to the mosaic crystal response. The X-ray Oriented Programs (xop) multi-lamellar model of bent crystals is used to model the rocking curve of these crystals and the calibration data confirm that a single model is adequate to reproduce simultaneously all measured integrated reflectivities and rocking-curve FWHM for multiple radii of curvature in both 1st and 2nd order of diffraction.

Pinned, optically aligned diagnostic dock for use on the Z facility.

The pinned optically aligned diagnostic dock (PODD) is a multi-configuration diagnostic platform designed to measure x-ray emission on the Z facility. The PODD houses two plasma emission acquisition (PEA) systems, which are aligned with a set of precision machined pins. The PEA systems are modular, allowing a single diagnostic housing to support several different diagnostics. The PEA configurations fielded to date include both time-resolved and time-integrated, 1D spatially resolving, elliptical crystal spectrometers, and time-integrated, 1D spatially resolving, convex crystal spectrometers. Additional proposed configurations include time-resolved, monochromatic mirrored pinhole imagers and arrays of filtered x-ray diodes, diamond photo-conducting diode detectors, and bolometers. The versatility of the PODD system will allow the diagnostic configuration of the Z facility to be changed without significantly adding to the turn-around time of the machine. Additionally, the PODD has been designed to allow instrument setup to be completed entirely off-line, leaving only a refined alignment process to be performed just prior to a shot, which is a significant improvement over the instrument the PODD replaces. Example data collected with the PODD are presented.

A methodology for calibrating wavelength dependent spectral resolution for crystal spectrometers.

High quality absorption spectroscopy measurements were recently achieved at the Sandia National Laboratories Z facility in the soft x-ray range. Detailed spectral resolution knowledge is a key requirement for their interpretation. We present a methodology for measuring the wavelength dependent crystal spectral resolution, with a particular focus on the 7-17 Å range. We apply this procedure to the case of 1st order resolution of a potassium acid phthalate (KAP) convex crystal spectrometer. One calibration issue is that inferring the crystal resolution requires that the x-ray source emission feature widths and spectral profiles are known. To this aim, we resolve Manson x-ray source Si, Al, and Mg Kα line profiles using a KAP crystal spectrometer in 2nd order to achieve relatively high resolution. This information is exploited to measure 1st order KAP resolving powers λ∕Δλ∼1100-1300 in the 7-10 Å wavelength range.

Doppler measurement of implosion velocity in fast Z-pinch x-ray sources.

The observation of Doppler splitting in K-shell x-ray lines emitted from optically thin dopants is used to infer implosion velocities of up to 70 cm/µs in wire-array and gas-puff Z pinches at drive currents of 15-20 MA. These data can benchmark numerical implosion models, which produce reasonable agreement with the measured velocity in the emitting region. Doppler splitting is obscured in lines with strong opacity, but red-shifted absorption produced by the cooler halo of material backlit by the hot core assembling on axis can be used to diagnose velocity in the trailing mass.

Radiating shock measurements in the Z-pinch dynamic hohlraum.

The Z-pinch dynamic hohlraum is an x-ray source for high energy-density physics studies that is heated by a radiating shock to radiation temperatures >200 eV. The time-dependent 300-400 eV electron temperature and 15-35 mg/cc density of this shock have been measured for the first time using space-resolved Si tracer spectroscopy. The shock x-ray emission is inferred from these measurements to exceed 50 TW, delivering >180 kJ to the hohlraum.

Characterization of extracellular chitinolytic activity in biofilms.

Extracellular enzymes produced by bacterial biofilms tend to become an integral, permanent part of the biofilm/substratum system. Thus, characterizing extracellular enzyme activity is an essential component of understanding biofilm ecology. Methods have been presented for characterizing three aspects of extracellular enzyme activity in biofilms: promoter activity of the structural gene, local catalytic activity, and kinetics of collective substrate degradation. The abundance of intracellular transcript derived from a structural gene is only indirectly related to the magnitude of catalytic activity of the corresponding enzyme. This relationship may be particularly tenuous in the case of extracellular enzymes, which must be transported out of the cell in order to become active. Fluorogenic substrates that allow direct detection of an increasingly greater variety of enzyme activities are becoming available. There are technical problems, originating from surface roughness and intrinsic fluorescence, associated with microscopic examination of biofilms on natural materials. Thin films provide one option for acquiring data about biofilms colonizing relevant materials.

Therapeutic range of digoxin's efficacy in heart failure: what is the evidence?

Clinical studies have solidified the utility of digoxin in patients with left ventricular dysfunction and normal sinus rhythm. No definitive data have been published to clarify the range of serum digoxin concentrations associated with clinical benefit. The traditional therapeutic range of 0.8-2.0 ng/ml was developed originally to classify digoxin toxicity, not efficacy. In addition, this reference range was used before publication of the Digitalis Investigators Group trial. Clinical and neurohormonal studies have attempted to characterize serum concentrations that are associated with clinical efficacy.

Digoxin toxicity: an evaluation in current clinical practice.

BACKGROUND: Serum digoxin concentrations (SDCs) are frequently sampled before completion of drug distribution. If elevated, these concentrations may be misinterpreted, potentially leading to a misdiagnosis of digoxin toxicity. OBJECTIVES: To determine the frequency of elevated SDCs (>2.6 nmol/L [>2.0 ng/mL]) obtained at appropriate postdosing intervals and to evaluate the frequency of clinically defined digoxin toxicity in patients with elevated SDCs. METHODS: The medical records of adult patients with SDCs assayed at 5 general hospitals in North Carolina during a 3-month period (May 1 through July 31, 1996) were prospectively evaluated. Data on SDC, inpatient or outpatient status, and medical or surgical service were collected for all patients. Data on patient demographics, serum chemistry values, indication for digoxin treatment, clinical evidence of digoxin toxicity, and timing of the blood sample relative to administration of the last dose of digoxin were collected for patients with SDCs higher than 2.6 nmol/L (>2.0 ng/mL). RESULTS: Of 3434 SDCs assayed in 2009 patients, 320 (9.3%) were higher than 2.6 nmol/L (>2.0 ng/mL). Fifty-one (15.9%) of the 320 SDCs were drawn at 6 hours or less following a digoxin dose. Sampling time relative to the digoxin dose could not be determined in 70 (21.9%) of the 320 elevated SDCs, leaving 199 (62.2%) of 320 SDCs in 138 patients evaluable for digoxin toxicity. Eighty-three of the 138 patients had clinical evidence of digoxin toxicity for an overall incidence of 4.1%. CONCLUSIONS: Digoxin toxicity occurs less frequently than historically reported. Continued emphasis needs to be placed on obtaining appropriately timed SDCs.

Converting i.v. nitroglycerin therapy to nitroglycerin ointment therapy: a comparison of two methods.

BACKGROUND: Methods of converting treatment with i.v. nitroglycerin to treatment with nitroglycerin ointment 2% vary greatly and may affect the length of time patients remain in the ICU, nursing time, and possible recurrent angina. To date, no randomized, controlled studies have evaluated the methods used for conversion. OBJECTIVE: To evaluate two methods of conversion. METHODS: Two hundred patients receiving i.v. nitroglycerin at doses of 10 to 100 micrograms/min were randomized to two methods of conversion: (1) Apply nitroglycerin ointment and stop i.v. nitroglycerin 30 minutes later. (2) Decrease the dose of i.v. nitroglycerin by 10 micrograms/min every 15 minutes, apply one half the dose of nitroglycerin ointment when the original i.v. dose has been decreased by one half, and apply the full dose of the ointment when the i.v. nitroglycerin is stopped. The primary end point was the time patients remained in the ICU after the conversion. Secondary end points included time to hospital discharge, estimate of nursing time, and selected clinical end points. Kaplan-Meier and Cox regression analyses were used to evaluate time patients remained in the ICU and nursing time. Clinical outcomes were analyzed by using a chi-square test. RESULTS: Use of the first method reduced median time before transfer from the ICU by 23 minutes and median nursing time by 45 minutes. Analysis of all clinical outcomes showed no differences between the two methods. CONCLUSIONS: Use of the first method was associated with a reduction in the time patients remained in the ICU before transfer to another unit and savings in nursing time, but the two methods did not differ according to clinical outcomes.

Plasma concentrations of diltiazem and desacetyldiltiazem in an overdose situation.

OBJECTIVE: To describe the elimination of diltiazem and desacetyldiltiazem in an overdose situation. CASE SUMMARY: An 18-year-old woman ingested controlled delivery diltiazem 14.94 g in a suicide attempt. After arriving at the hospital unresponsive and hypotensive, her condition progressed to complete heart block, cardiogenic shock, asystole, and acute renal failure. Supportive care consisted of vasopressors, intravenous calcium, intravenous glucagon, charcoal hemoperfusion, temporary transvenous pacing, and an intraaortic balloon pump. After 12 days in the hospital, the patient recovered fully. DISCUSSION: We report a large, documented overdose of diltiazem and detail the pharmacokinetic profiles of both diltiazem and its active metabolite, desacetyldiltiazem. Nonlinear elimination of diltiazem appears to occur at higher concentrations. Although the patient improved clinically following charcoal hemoperfusion, no dramatic effects on diltiazem elimination were apparent. CONCLUSIONS: Survival following massive diltiazem overdose can be achieved with supportive care. Charcoal hemoperfusion had a limited effect on improving the clearance of diltiazem as evidenced by serial plasma concentrations.

The contralateral reduction of intraocular pressure by timolol.

Administration of timolol to one eye is associated with a decrease in intraocular pressure in both eyes. To further investigate this effect the contralateral decrease in intraocular pressure was measured in a three arm crossover study using a 0.1 mg dose of timolol given topically to an eye, a 0.1 mg dose of timolol given lingually, and a placebo given topically. Two hours after topical timolol administration the mean intraocular pressure reduction in the fellow eye was 3.1 mm Hg compared with baseline (p = 0.0007). Two hours after lingual timolol administration the mean intraocular pressure reduction was 3.9 mm Hg compared with baseline (p = 0.0004). Two hours after topical administration of placebo the mean intraocular pressure reduction in the fellow eye was only 0.33 mm Hg (p = 0.6). These findings suggest the contralateral reduction in intraocular pressure from timolol is caused by systemic absorption. The significant intraocular pressure reduction obtained from lingual timolol raises the possibility that this route of drug administration may be useful in selected patients who cannot use eye drops.

Clinical and pharmacokinetic profiles of digoxin immune Fab in four patients with renal impairment.

Minimal pharmacokinetic data on digoxin immune Fab are currently available, especially in patients with impaired renal function. The serum concentration-time profiles of total digoxin, free digoxin, and digoxin immune Fab in four patients with moderate to severe renal impairment who received digoxin immune Fab are presented. The calculated elimination half-life of digoxin immune Fab was 25-73 hours. The calculated elimination half-life of total digoxin was 24-72 hours. Free digoxin concentrations rebounded to a peak of 1-2.9 ng/mL 44-97 hours after the administration of digoxin immune Fab. The areas under the curve for digoxin immune Fab were 213-1026 micrograms.h/mL, and total body clearances were 2.3-7.1 mL/min. The total digoxin concentrations peaked at 14-33 times the pre-Fab digoxin concentrations 5-30 hours after digoxin immune Fab administration. In comparing these data with data available from patients with normal renal function, the half-life of digoxin immune Fab and total digoxin was longer, the peak total digoxin concentration occurred later, the ratio of the peak total digoxin concentration to pre-Fab digoxin concentration was larger, and the rebound in free digoxin occurred later in patients with renal impairment. The Fab dose should not be reduced in patients with renal impairment; however, post-Fab monitoring should be extended to compensate for the prolonged half-life of Fab and later rebound of free digoxin.