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in creator/contributor: "Kauffman, R L"

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Review of x-ray spectroscopy from laser-produced plasmas

Recent progress in x-ray spectroscopy from laser plasmas is reviewed. Advances in the use of K-shell spectra as a diagnostic tool is discussed. Much activity in understanding complex spectra especially from Ne I and Ni I isoelectronic series have been made. Much of the progress has been due to observation of amplification from ..delta..n = O transitions from these configurations. The spectroscopy will be discussed and examples of spectra of the amplified lines will be shown. Finally, recent wor… more

Date: September 1, 1987

Creator: Kauffman, R.L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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X-ray spectroscopy of laser-produced plasmas

A brief discussion is given of the importance of x-ray spectroscopy as a diagnostic tool for laser-produced plasma. Of particular note is the role of opacity and time dependence. (MOW)

Date: August 1, 1984

Creator: Kauffman, R.L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Absolutely calibrated soft-x-ray streak camera for laser-fusion applications

The intensity output of a soft-x-ray streak camera was calibrated (SXRSC) in order to make absolute flux measurements of x rays emitted from laser-produced plasmas. The SXRSC developed at LLNL is used to time-resolve x-ray pulses to better than 20 ps. The SXRSC uses a Au photocathode on a thin carbon substrate which is sensitive to x rays from 100 eV to greater than 10 keV. Calibrations are done in the dynamic mode using a small laser-produced x-ray source. The SXRSC is calibrated by comparing … more

Date: January 1, 1982

Creator: Kauffman, R.L.; Medecki, H. & Stradling, G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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X-ray streak crystal spectography

We have built an x-ray streaked crystal spectrograph for making time-resolved x-ray spectral measurements. This instrument can access Bragg angles from 11/sup 0/ to 38/sup 0/ and x-ray spectra from 200 eV to greater than 10 keV. We have demonstrated resolving powers, E/..delta..E > 200 at 1 keV and time resolution less than 20 psec. A description of the instrument and an example of the data is given.

Date: July 1, 1983

Creator: Kauffman, R.L.; Brown, T. & Medecki, H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Time-resolved spectral measurements above 80 A

We have made time-resolved spectral measurements above 80 A from laser-produced plasmas. These are made using a transmission grating spectrograph whose primary components are a cylindrically-curved x-ray mirror for light collection, a transmission grating for spectral dispersions, and an x-ray streak camera for temporal resolution. A description of the instrument and an example of the data are given.

Date: July 1, 1983

Creator: Kauffman, R.L.; Ceglio, N. & Medecki, H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Progress Toward Ignition on the National Ignition Facility

The principal approach to ignition on the National Ignition Facility (NIF) is indirect drive. A schematic of an ignition target is shown in Figure 1. The laser beams are focused through laser entrance holes at each end of a high-Z cylindrical case, or hohlraum. The lasers irradiate the hohlraum walls producing x-rays that ablate and compress the fuel capsule in the center of the hohlraum. The hohlraum is made of Au, U, or other high-Z material. For ignition targets, the hohlraum is {approx}0.5 … more

Date: October 17, 2011

Creator: Kauffman, R L

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Review of hohlraum coupling

Extensive experiments have been done to characterize laser-heated hohlraum targets for indirect drive inertial fusion. Scattered light and fast electrons from laser-plasma instabilities have been found not to be significant for short wavelength light. Scaling of radiation temperature with laser power has been studied at several Laboratories and can be represented by a simple power balance scaling for experiments using short wavelength light. Measurements of x-ray production and energy loss in h… more

Date: January 30, 1995

Creator: Kauffman, R.L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Pulsed calibration of the soft x-ray streak camera

In order to better understand laser plasma interactions an effort is being made to obtain quantitative temporally and spectrally resolved measurements in the low energy x-ray region using a soft x-ray streak camera. X-ray mirrors and absorption filters are employed to perform broad band spectroscopy measurements. The components of these systems have now been calibrated and the results of these measurements will be reported. The calibration of the x-ray streak camera, needed to make absolute flu… more

Date: November 1, 1979

Creator: Kauffman, R. L.; Medecki, H. & Pierce, E. L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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X-ray-transport effects in laser-irradiated disks

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 co… more

Date: October 6, 1981

Creator: Kauffman, R.L.; Matthews, D.L. & Lee, R.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Picosecond x-ray measurements from 100 eV to 30 keV

Picosecond x-ray measurements relevant to the Livermore Laser Fusion Program are reviewed. Resolved to 15 picoseconds, streak camera detection capabilities extend from 100 eV to higher than 30 keV, with synchronous capabilities in the visible, near infrared, and ultraviolet. Capabilities include automated data retrieval using charge coupled devices (CCD's), absolute x-ray intensity levels, novel cathodes, x-ray mirror/reflector combinations, and a variety of x-ray imaging devices.

Date: October 15, 1980

Creator: Attwood, D.T.; Kauffman, R.L. & Stradling, G.L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Diagnostics for an XUV/soft x-ray laser

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 im… more

Date: March 3, 1984

Creator: Kauffman, R.L.; Matthews, D.L.; Ceglio, N. & Medecki, H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Quantitative measurements using soft-x-ray streak cameras

A Soft X-Ray Streak Camera (SXRSC) is a fast timing instrument sensitive to x rays from 100 eV to 300 keV. The instrument has excellent time resolution (approx. 15 ps) and large dynamic range (approx. 10/sup 3/) which are well suited for measuring x-ray pulses produced by laser-fusion targets. The SXRSC uses a thin transmission photocathode to convert x-rays to a secondary electron signal which is accelerated, focused, and deflected onto a phosphor producing an image of the x-ray pulse time his… more

Date: August 1, 1981

Creator: Kauffman, R. L.; Stradling, G. L.; Pierce, E. L. & Medecki, H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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

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 ti… more

Date: January 1, 1982

Creator: Kauffman, R.L.; Matthews, D.L.; Kilkenny, J.D. & Lee, R.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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X-ray conversion physics

We have performed a series of experiments to study the physics of the conversion of 0.35-..mu..m laser light to soft x-rays in high-Z materials. The efficiency of soft x-ray and M-band radiation production as a function of laser intensity (5 /times/ 10/sup 13/ to 3 /times/ 10/sup 15/ W/cm/sup 2/) was measured. At fixed intensity 5 /times/ 10/sup 14/ W/cm/sup 2/, the time-resolved and time-integrated thermal x-ray (E < 1.5 keV) conversion efficiency increased with the laser pulse length for up t… more

Date: October 1, 1988

Creator: Kauffman, R.L.; Kania, D.R.; Langer, S.; Kornblum, H. & Ze, F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

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

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 p… more

Date: November 1, 1982

Creator: Matthews, D.L.; Kauffman, R.L.; Kilkenny, J.D. & Lee, R.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

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

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 … more

Date: November 1, 1982

Creator: Kauffman, R.L.; Matthews, D.L.; Kilkenny, J.D. & Lee, R.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Dynamics of gas-filled hohlraums

In order to prevent high-Z plasma from filling in the hohlraum in indirect drive experiments, a low-Z material, or tamper is introduced into the hohlraum. This material, when fully ionized is typically less than one-tenth of the critical density for the laser light used to illuminate the hohlraum. This tamper absorbs little of the laser light, thus allowing most of the laser energy to be absorbed in the high-Z material. However, the pressure associated with this tamper is sufficient to keep the… more

Date: April 24, 1995

Creator: Orzechowski, T.J.; Kauffman, R.L. & Kirkwood, R.K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Improved gas-filled hohlraum performance on Nova with beam smoothing

Gas-filled hohlraums are presently the base line ignition target design for the National Ignition Facility. Initial Nova experiments on gas-filled hohlraums showed that radiation temperature was reduced due to SBS and SRS scattering losses and that implosion symmetry had shifted compared with vacuum hohlraums and calculations. Subsequent single beam experiments imaging thermal x-ray emission showed the shift is due to laser-plasma heating dynamics and filarnentation in a flowing plasma. Experim… more

Date: December 2, 1997

Creator: Kauffman, R. L.; Powers, L. V. & Dixit, S. N.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Radiation drive in laser heated hohlraums

Nearly 10 years of Nova experiments and analysis have lead to a relatively detailed quantitative and qualitative understanding of radiation drive in laser heated hohlraums. Our most successful quantitative modelling tool is 2D Lasnex numerical simulations. Analysis of the simulations provides us with insight into the details of the hohlraum drive. In particular we find hohlraum radiation conversion efficiency becomes quite high with longer pulses as the accumulated, high Z blow-off plasma begin… more

Date: November 3, 1995

Creator: Suter, L.J.; Kauffman, R.L. & Darrow, C.B.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Comparison of cesium iodide and gold photocathodes for x-ray streak cameras

X-ray streak cameras at Lawrence Livermore Laboratory use gold transmission photocathodes for x-ray detection. Other photocathode materials which might provide improved sensitivity without loss of temporal resolution are of interest. Of particular interest are dielectrics such as cesium iodide. Simultaneous measurements of the sensitivity to 500 eV x-rays of both gold and cesium iodide photocathodes in the LLL Soft X-ray Streak Camera were made. Enhanced sensitivity with the Csl photocathodes i… more

Date: January 1, 1979

Creator: Stradling, G.L.; Medecki, H.; Attwood, D.T.; Kauffman, R.L. & Henke, B.L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Line intensities for diagnosing laser-produced plasmas

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… more

Date: October 31, 1983

Creator: Kauffman, R.L.; Matthews, D.L.; Lee, R.W.; Whitten, B.L. & Kilkenny, J.D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Characterization of nova plasmas using an x-ray spectrometer with temporal and spatial resolution

Spectroscopic diagnostics have great potential to obtain high temperature measurements of plasmas created in ICF targets. The plasmas may be over 1 mm in size and therefore, one of the first steps in making accurate spectroscopic measurements has been to improve the resolution of the instrument. A spectrograph is now available for Nova experiments which takes advantage of gated technology by coupling a Bragg crystal to a microchannel plate that can record data over a 250 ps time frame. The crys… more

Date: May 1, 1994

Creator: Back, C. A.; Kauffman, R. L.; Bell, P. & Kilkenny, J. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Efficient production of 2--10 keV x-rays by laser heated ``underdense radiators``

The next generation of high power lasers offers the prospect of creating multi-kilovolt x-rays with {gt}10% efficiency. Such efficiencies are achieved with ``underdense radiators``, a non- traditional source of laser generated x-rays. Applications of these sources with the proposed National Ignition Facility (NIF) include volume preheating of experiments; bright, multi-keV backlighting; pumps for fluorescent imaging of capsule dopants and Doppler velocimetry; uniform irradiation of large test o… more

Date: May 22, 1996

Creator: Suter, L. J.; Kauffman, R. L.; Maxon, M. S. & Davis, J. F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Self Thomson Scattering in Laser Produced Plasmas

The NIF Power Conditioning System (PCS) resides in four Capacitor Bays, supplying energy to the Master and Power Amplifiers which reside in the two adjacent laser bays. Each capacitor bay will initially house 48 individual power conditioning modules, shown in Figure 2, with space reserved for expansion to 54 modules. The National Ignition Facility (NIF) Power Conditioning System (PCS) is a modular capacitive energy storage system that will be capable of storing nearly 400 MJ of electrical energ… more

Date: August 22, 2003

Creator: Niemann, C; Glenzer, S H; Kauffman, R L; Meezan, N B; Oades, K; Slark, G et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department