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Collisional quenching of metastable x-ray emitting states in a fast beam of He-like fluorine

Description: High resolution x-ray spectral measurements are used to determine the relative intensity of He-like fluorine x-ray transitions, 2 $sup 3$P$sub 1$ $Yields$ 1 $sup 1$S$sub 0$ and $sup 1$P$sub 1$ $Yields$ $sup 1$S$sub 0$, produced in fluorine collisions with Ne, Ar, and Kr gas targets at various pressures and in thin carbon foils and a thick carbon slab. The relative intensities are observed to be strong functions of both target density and incident charge Z. These effects are attributed to strong collisional quenching of both initial states by subsequent large impact parameter collisions. The data permit extraction for the first time of the total quenching cross sections (sigma/sub Q/ ) for fast fluorine ions in both states. A strong enhancement of the relative intensity of the 2 $sup 3$P$sub 1$ is observed for F$sup 7+$ projectiles. This strong enhancement is attributed to selective excitation of metastable states in the beam, i.e., 1s2s $sup 3$S$sub 1$, into the 1s2p $sup 3$P$sub 1$ state. Finally, the data for foil and solid targets are used to obtain new information on the excitation states of ions moving in solids. High resolution measurements of the radiative electron capture (REC) peak are reported and analyzed for the first time. 3 figs, 1 table (auth)
Date: September 1, 1975
Creator: Matthews, D. L. & Fortner, R. J.
Partner: UNT Libraries Government Documents Department

Experiments to study the feasibility of making an x-ray laser at the Novette laser facility

Description: We will discuss a set of experiments which are designed to study approaches to and search for the existence of amplified spontaneous emission at photon energies of 42.3, 53.6, 119.0, and 153.0 eV. The schemes utilize pumping from the Novette laser operated with cylindrical optics at 5 TW/beam and 100 psec.
Date: May 17, 1983
Creator: Matthews, D.L.; Hagelstein, P. & Kauffman, R.
Partner: UNT Libraries Government Documents Department

Using spectral line profiles as a diagnostic of the plasma electron density

Description: A description of a simple interactive fitting procedure is given which uses line profiles calculated for highly stripped ions, i.e., hydrogenic, helium-like and lithium-like species. Information on the calculation of these profiles is provided. The experimental data is read from disk, so any appropriately formatted data can be referenced.
Date: August 1, 1981
Creator: Lee, R.W. & Matthews, D.L.
Partner: UNT Libraries Government Documents Department

X-ray-transport effects in laser-irradiated disks

Description: X-ray emission spectra are important diagnostics for studying laser-coupling and energy transport. We have begun exploring the sensitivity of such measurements to the plasma density and temperature profiles. The one-dimensional radiation transport equation is solved for various temperature and density profiles. Spectra are calculated in both the LTE and CRE approximations, bracketing the relevant ionization regimes. Their applicability to real plasmas is discussed. The calculated spectra are compared with measurements from different Z targets. This comparison explores the possible temperature and density parameters. Such comparisons can be used to interpret present experimental results as well as guide the design of future experiments.
Date: October 6, 1981
Creator: Kauffman, R.L.; Matthews, D.L. & Lee, R.W.
Partner: UNT Libraries Government Documents Department

X-ray backlighting characterization experiments performed with laser wavelengths of 1. 06, 0. 53, and 0. 35. mu. m

Description: We report the conversion efficiency, xi/sub x/, for production of x-ray backlighting line sources from 1.4 keV to 8.6 keV as a function of laser wavelength, -pulselength and intensity. For K-shell x-ray line emission we observed only a moderate increase in xi/sub x/ when using a 0.35..mu..m (instead of 1.06 ..mu..m) wavelength laser.
Date: January 1, 1982
Creator: Matthews, D.L.; Campbell, E.M. & Ceglio, N.
Partner: UNT Libraries Government Documents Department

X-ray backlighting sources of 4 to 10 keV for laser-fusion targets

Description: High-intensity, short-duration x-ray pulses are necessary to diagnose the compression of laser film targets. Present target designs are such that backlighting sources ranging from a few thousand electron volts to 100 keV will be necessary. The desired source durations range from a few tens of picoseconds for flash radiography to several nanoseconds for streaked backlighting, and the source occurrence must be tightly synchronized to that of the target-irradiating laser pulse. For the latter reason, a laser-induced x-ray pulse is preferred. An initial study of the K lines of Ti, Ni, and Zn as possible backlighting sources was conducted. The conversion efficiency of laser light into line radiation was obtained as a function of laser intensity, pulse length, and wavelength. A threshold laser intensity for x-ray line production was identified. Information was obtained on the size and duration of the x-ray emission source, in relation to laser parameters. The experimental results, and their impact on backlighting capability for high-density laser function targets, are discussed.
Date: May 12, 1981
Creator: Rupert, V.C.; Matthews, D.L. & Koppel, L.N.
Partner: UNT Libraries Government Documents Department

Progress and prospects for soft x-ray lasing driven by high power optical lasers

Description: We will describe our optical laser pumped xuv Laser Program. To date, we have concentrated our efforts on exploding foil amplifier designs using Ne-like n=3p to 3s inversion schemes. We will describe our latest modeling results as well as measurements which demonstrate output power near the 1 MW level at 206 and 209 A and lasing at wavelengths as short as 106 A.
Date: July 3, 1986
Creator: Rosen, M.D.; Matthews, D.L. & Hagelstein, P.L.
Partner: UNT Libraries Government Documents Department

Spectroscopic analysis of the density and temperature gradients in the laser-heated gas jet

Description: We have performed an analysis of the x-ray spectra produced by a 1.0TW, lambda/sub L/-0.53..mu..m laser-irradiated gas jet. Plasmas produced by ionization of neon, argon and N/sub 2/ + SF/sub 6/ gases were included in those measurements. Plasma electron density and temperature gradients were obtained by comparison of measured spectra with those produced by computer modeling. Density gradients were also obtained using laser interferometry. The limitations of this technique for plasma diagnosis will be discussed.
Date: January 1, 1981
Creator: Matthews, D.L.; Lee, R.W. & Auerbach, J.M.
Partner: UNT Libraries Government Documents Department

Experiments with polymer coated microspheres irradiated by the Shiva laser system

Description: Polymer coated spherical targets have been irradiated by the Shiva laser system in an effort to compress the contained 10 mg/cc DT fuel to super liquid densities. Glass microspheres of 140 ..mu..m ID and 5 ..mu..m wall thickness with polymer coatings 15 ..mu..m to 100 ..mu..m thick have been irradiated with laser pulses of 4 kilojoules in 200 psec FWHM. Target performance was diagnosed with neutron yield measurements, radiochemistry, Argon line imaging, and x-ray imaging techniques. Ball in plate targets achieved greater implosion symmetry than free-standing ball targets. With yields of 10/sup 7/ to 10/sup 8/ neutrons, targets reached DT fuel compressions of several times liquid density.
Date: November 10, 1979
Creator: Auerbach, J.M.; Manes, K.R. & Matthews, D.L.
Partner: UNT Libraries Government Documents Department

Diagnostics for an XUV/soft x-ray laser

Description: We have begun investigating the production of an XUV/soft x-ray laser, using our high-powered glass lasers as drivers. A major diagnostic for lasing is the measure of the absolute power produced in the lasing line. I have developed a spectrograph to time-resolved lasing lines in the energy range from 50 eV to greater than 200 eV. the spectrograph combines a transmission grating and x-ray streak camera to produce a flat field instrument. A cylindrical mirror is used in front of the grating to image the source and act as a collecting optic. The efficiency of the components is calibrated so that absolute intensities can be measured. I will compare the performance of this instrument with reflection grating systems. I will also discuss planned improvements to the system which should increase total throughput, image quality, and resolving power.
Date: March 3, 1984
Creator: Kauffman, R.L.; Matthews, D.L.; Ceglio, N. & Medecki, H.
Partner: UNT Libraries Government Documents Department

Measurement of x-rays emitted from projectiles moving in solid targets

Description: The results of three separate experiments all dealing with the production of x-rays in projectiles moving in solids are discussed. The first experiment deals with the measurement of line widths of x-rays emitted from projectiles moving in solid targets. The effect of collisional broadening of x- rays is found to dominate the line widths giving greater than an order of magnitude increase in the measured line widths. The second experiment studies ''solid target effects'' in producing non-binomial distributions of characteristic K x-ray spectra in heavy ion-atom collisions. The third experiment studies aluminum K x-ray production in Ar$sup +$ $Yields$ Al collisions in very thin aluminum foils as a function of foil thickness. Parameterization of the observed non-linear dependence enables the lifetime of the argon 2p vacancy and total ionization cross sections for the argon L-shell in Ar $Yields$ Al collisions to be measured. (auth)
Date: January 1, 1975
Creator: Fortner, R.J.; Matthews, D.L.; Feldman, L.C.; Garcia, J.D. & Oona, H.
Partner: UNT Libraries Government Documents Department

Line intensities for diagnosing laser-produced plasmas

Description: We have measured relative line intensities of the K x-ray spectra of Si, Cl, and Ca from laser-produced plasmas to assess their usefulness as a plasma diagnostic. The different elements are added at low concentrations to CH disks which are irradiated at 5 x 10/sup 14/ W/cm/sup 2/ with a 0.53 ..mu..m laser pulse of 20 Joules at 1 nsec. The concentration of each element is kept low in order not to change the Z of the plasma, and therefore the plasma dynamics. The various spectra are measured with a time-resolved spectrograph to obtain line intensities as a function of time over the length of the laser pulse. These relative intensities of various He-like and H-like lines are compared with calculations from a steady-state level population code. The results give good consistency among the various line ratios. Agreement is not as good for analysis of the Li-like satellite lines. Modelling of the Li-like lines need further investigation. 10 references, 9 figures.
Date: October 31, 1983
Creator: Kauffman, R.L.; Matthews, D.L.; Lee, R.W.; Whitten, B.L. & Kilkenny, J.D.
Partner: UNT Libraries Government Documents Department

Time-resolved x-ray line diagnostics of laser-produced plasmas

Description: We have examined the underdense plasma conditions of laser irradiated disks using K x-rays from highly ionized ions. A 900 ps laser pulse of 0.532 ..mu..m light is used to irradiate various Z disks which have been doped with low concentrations of tracer materials. The tracers whose Z's range from 13 to 22 are chosen so that their K x-ray spectrum is sensitive to typical underdense plasma temperatures and densities. Spectra are measured using a time-resolved crystal spectrograph recording the time history of the x-ray spectrum. A spatially-resolved, time-integrated crystal spectrograph also monitors the x-ray lines. Large differences in Al spectra are observed when the host plasma is changed from SiO/sub 2/ to PbO or In. Spectra will be presented along with preliminary analysis of the data.
Date: January 1, 1982
Creator: Kauffman, R.L.; Matthews, D.L.; Kilkenny, J.D. & Lee, R.W.
Partner: UNT Libraries Government Documents Department

Time-resolved x-ray line diagnostics of laser-produced plasmas

Description: We have examined the underdense plasma conditions of laser irradiated disks using K x-rays from highly ionized ions. A 900 ps laser pulse of 0.532 ..mu..m light is used to irradiate various Z disks which have been doped with low concentrations of tracer materials. The tracers, whose Z's range from 13 to 22, are chosen so that their K x-ray spectrum is sensitive to typical underdense plasma temperatures and densities. Spectra are measured using a time-resolved crystal spectrograph recording the time history of the x-ray spectrum. A spatially-resolved, time-integrated crystal spectrograph also monitors the x-ray lines. Large differences in Al spectra are observed when the host plasms is changed from SiO/sub 2/ to PbO or In. Spectra will be presented along with preliminary analysis of the data.
Date: November 1, 1982
Creator: Kauffman, R.L.; Matthews, D.L.; Kilkenny, J.D. & Lee, R.W.
Partner: UNT Libraries Government Documents Department

Studying electron distributions using the time-resolved free-bound spectra from coronal plasmas

Description: Absorption of laser light in a plasma by inverse bremsstrahlung, I.B., can lead to a non-Maxwellian velocity distribution provided the electron-elecron collision frequency is too low to equilibrate the velocity distribution in the coronal plasma region of a laser heated aluminum disk by measuring the radiation recombination continuum. The experiments are performed using lambda/sub L/ = 0.532 ..mu..m laser light at intensities of approx. 10/sup 16/ W/cm/sup 2/. Such parameters are predicted to produce conditions suitable for a non-thermal electron distribution. The shape of the K-shell recombination radiation has been measured using a time-resolved x-ray spectrograph. The electron distribution can be determined from deconvolution of the recombination continuum shape.
Date: November 1, 1982
Creator: Matthews, D.L.; Kauffman, R.L.; Kilkenny, J.D. & Lee, R.W.
Partner: UNT Libraries Government Documents Department

Autofluorescence dynamics during reperfusion following long-term renal ischemia in a rat model

Description: Optical properties of near-surface kidney tissue were monitored in order to assess response during reperfusion to long (20 minutes) versus prolonged (150 minutes) ischemia in an in vivo rat model. Specifically, autofluorescence images of the exposed surfaces of both the normal and the ischemic kidneys were acquired during both injury and reperfusion alternately under 355 nm and 266 nm excitations. The temporal profile of the emission of the injured kidney during the reperfusion phase under 355 nm excitation was normalized to that under 266 nm as a means to account for changes in tissue optical properties independent of ischemia as well as changes in the illumination/collection geometrical parameters in future clinical implementation of this technique using a hand-held probe. The scattered excitation light signal was also evaluated as a reference signal and found to be inadequate. Characteristic time constants were extracted using fit to a relaxation model and found to have larger mean values following 150 minutes of injury. The mean values were then compared with the outcome of a chronic survival study where the control kidney had been removed. Rat kidneys exhibiting longer time constants were much more likely to fail. This may lead to a method to assess kidney viability and predict its ability to recover in the initial period following transplantation or resuscitation.
Date: February 8, 2008
Creator: Raman, R N; Pivetti, C D; Matthews, D L; Troppmann, C & Demos, S G
Partner: UNT Libraries Government Documents Department

Optical Spectroscopy Approach for the Predictive Assessment of Kidney Functional Recovery Following Ischemic Injury

Description: Tissue that has undergone significant yet unknown amount of ischemic injury is frequently encountered in organ transplantation and trauma clinics. With no reliable real-time method of assessing the degree of injury incurred in tissue, surgeons generally rely on visual observation which is subjective. In this work, we investigate the use of optical spectroscopy methods as a potentially more reliable approach. Previous work by various groups was strongly suggestive that tissue autofluorescence from NADH obtained under UV excitation is sensitive to metabolic response changes. To test and expand upon this concept, we monitored autofluorescence and light scattering intensities of injured vs. uninjured rat kidneys via multimodal imaging under 355 nm, 325 nm, and 266 nm excitation as well as scattering under 500 nm illumination. 355 nm excitation was used to probe mainly NADH, a metabolite, while 266 nm excitation was used to probe mainly tryptophan to correct for non-metabolic signal artifacts. The ratio of autofluorescence intensities derived under these two excitation wavelengths was calculated and its temporal profile was fit to a relaxation model. Time constants were extracted, and longer time constants were associated with kidney dysfunction. Analysis of both the autofluorescence and light scattering images suggests that changes in microstructure tissue morphology, blood absorption spectral characteristics, and pH contribute to the behavior of the observed signal which may be used to obtain tissue functional information and offer predictive capability.
Date: February 11, 2010
Creator: Raman, R N; Pivetti, C D; Rubenchik, A M; Matthews, D L; Troppmann, C & Demos, S G
Partner: UNT Libraries Government Documents Department

Traveling wave pumping of ultra-short pulse x-ray lasers

Description: Pumping of proposed inner-shell photo-ionized (ISPI) x-ray lasers places stringent requirements on the optical pump source. We investigate these requirements for an example x-ray laser (XRL) in Carbon lasing on the 2p-1s transition at 45 A. Competing with this lasing transition is the very fast Auger decay rate out of the upper lasing state, such that the x-ray laser would self-terminate on a femto- second time scale. XRL gain may be demonstrated if pump energy is delivered in a time short when compared to the Auger rate. The fast self-termination also demands that we sequentially pump the length of the x-ray laser at the group velocity of the x-ray laser. This is the classical traveling wave requirement. It imposes a condition on the pumping source that the phase angle of the pump laser be precisely de- coupled from the pulse front angle. At high light intensities, this must be performed with a vacuum grating delay line. We will also include a discussion of issues related to pump energy delivery, i.e. pulse-front curvature, temporal blurring and puke fidelity. An all- reflective optical system with low aberration is investigated to see if it fulfills the requirements. It is expected that these designs together with new high energy (>1J) ultra-short pulse (< 40 fs) pump lasers now under construction may fulfill our pump energy conditions and produce a tabletop x-ray laser.
Date: November 10, 1997
Creator: Snavely, R.A.; Da Silva, L.B.; Eder, D.C.; Matthews, D.L. & Moon, S.J.
Partner: UNT Libraries Government Documents Department

Two-color mid-infrared thermometer using a hollow glass optical fiber

Description: A non-invasive two-color infrared thermometer has been developed for low-temperature biomedical applications. Mid-infrared radiation from the target is collected via a single 700 {mu}m-bore hollow glass optical fiber, simultaneously split into two paths and modulated by a gold-coated reflective optical chopper, and focused onto two thermoelectrically-cooled HgCdZnTe photoconductors (bandpasses of 2- 6 {mu}m and 2-12 {mu}m, respectively) by gold-coated spherical mirrors. The small numerical aperture of the hollow glass fiber provides high spatial resolution (is less than 1 mm), and the hollow bore eliminates reflective losses. The modulated detector signals are recovered using lock-in amplification, permitting measurement of small low-temperature signal buried in the background. A computer algorithm calculates the true temperature and emissivity of the target in real time based on a previous blackbody (emissivity equal to 1) calibration, taking into account reflection of the ambient radiation field from the target surface.
Date: June 30, 1997
Creator: Small, W., IV.; Celliers, P.M.; Da Silva, L.D. & Matthews, D.L.
Partner: UNT Libraries Government Documents Department

Spatially resolved x-ray laser spectra and demonstration of gain in nickel-like systems

Description: A recent series of experiments have provided spatially resolved near field images of several candidate x-ray lasing transition in neon-like, nickel-like, and hydrogen-like ions from laser-produced plasmas. From these time-gated, spatially, and spectrally resolved measurements the source size for the J = 0 - 1 and the J = 2 - 1 transitions in Ne-like selenium have been determined. Source regions as small as 50 ..mu..m have been observed on transitions with gain-length products >9. In addition, we have obtained the first experimental evidence for the amplification of spontaneous emission in the nickel-like ions of europium and ytterbium. Gains of order 1 cm/sup -1/ and gain-length products of up to 3.8 are observed on the J = 0 - 1, 4d-4p transitions in Eu + 35 at 65.26 and 71.00 A. Analogous transitions in Yb = +42 have been identified and some evidence for ASE has been observed. 7 refs., 11 figs.
Date: September 25, 1987
Creator: Whelan, D.A.; Keane, C.J.; MacGowan, B.J.; Matthews, D.L.; Trebes, J.E. & Eckart, M.J.
Partner: UNT Libraries Government Documents Department

Fabrication and In Vitro Deployment of a Laser-Activated Shape Memory Polymer Vascular Stent

Description: Vascular stents are small tubular scaffolds used in the treatment of arterial stenosis (narrowing of the vessel). Most vascular stents are metallic and are deployed either by balloon expansion or by self-expansion. A shape memory polymer (SMP) stent may enhance flexibility, compliance, and drug elution compared to its current metallic counterparts. The purpose of this study was to describe the fabrication of a laser-activated SMP stent and demonstrate photothermal expansion of the stent in an in vitro artery model. A novel SMP stent was fabricated from thermoplastic polyurethane. A solid SMP tube formed by dip coating a stainless steel pin was laser-etched to create the mesh pattern of the finished stent. The stent was crimped over a fiber-optic cylindrical light diffuser coupled to an infrared diode laser. Photothermal actuation of the stent was performed in a water-filled mock artery. At a physiological flow rate, the stent did not fully expand at the maximum laser power (8.6 W) due to convective cooling. However, under zero flow, simulating the technique of endovascular flow occlusion, complete laser actuation was achieved in the mock artery at a laser power of {approx}8 W. We have shown the design and fabrication of an SMP stent and a means of light delivery for photothermal actuation. Though further studies are required to optimize the device and assess thermal tissue damage, photothermal actuation of the SMP stent was demonstrated.
Date: April 25, 2007
Creator: Baer, G M; Small IV, W; Wilson, T S; Benett, W J; Matthews, D L; Hartman, J et al.
Partner: UNT Libraries Government Documents Department