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V N Shlyaptsev - One of the best experts on this subject based on the ideXlab platform.

  • high power density capillary discharge plasma columns for Shorter Wavelength discharge pumped soft x ray lasers
    Physical Review E, 2002
    Co-Authors: Juan Jose Gonzalez, M Frati, J J Rocca, V N Shlyaptsev, A L Osterheld
    Abstract:

    : We report the generation of plasma columns in gas-filled capillary channels using discharge excitation powers that exceed those of previous studies by one to two orders of magnitude. Current pulses up to 200 kA and 10-90 % rise time of about 10 ns (current increase rate equivalent to 1.5 x 10(13) A/s) were utilized to excite plasmas in 3.3 and 4 mm diameter channels. Time resolved soft-x-ray spectra and pinhole images of the plasma were obtained. The experimental data and its comparison with model computations suggest that dense argon plasma columns 300 mum in diameter with electron temperatures >250 eV have been obtained. These characteristics make these plasmas of interest for extending discharge-pumped lasers to Shorter Wavelengths.

  • high power density capillary discharge plasma columns for Shorter Wavelength discharge pumped soft x ray lasers
    Physical Review E, 2002
    Co-Authors: Juan Jose Gonzalez, M Frati, J J Rocca, V N Shlyaptsev, A L Osterheld
    Abstract:

    We report the generation of plasma columns in gas-filled capillary channels using discharge excitation powers that exceed those of previous studies by one to two orders of magnitude. Current pulses up to 200 kA and 10--90 % rise time of \ensuremath{\sim}10 ns (current increase rate $\ensuremath{\sim}1.5\ifmmode\times\else\texttimes\fi{}{10}^{13}\mathrm{A}/\mathrm{s})$ were utilized to excite plasmas in 3.3 and 4 mm diameter channels. Time resolved soft-x-ray spectra and pinhole images of the plasma were obtained. The experimental data and its comparison with model computations suggest that dense argon plasma columns 300 \ensuremath{\mu}m in diameter with electron temperatures g250 eV have been obtained. These characteristics make these plasmas of interest for extending discharge-pumped lasers to Shorter Wavelengths.

  • generation of plasma columns for Shorter Wavelength capillary discharge soft x ray lasers utilizing a high power blumlein generator
    SPIE's International Symposium on Optical Science Engineering and Instrumentation, 1999
    Co-Authors: Juan Jose Gonzalez, M Frati, J J Rocca, V N Shlyaptsev
    Abstract:

    Capillary discharge plasmas were generated with current pulses up to 200 kA and 10 - 90% rise time of about 10 ns using a water dielectric Blumlein generator. Time resolve spectra and pinhole images of the plasma columns generated in ceramic capillaries are presented. The data indicates that the plasma obtain in ceramic capillaries are hotter than those generated in polyacetal capillaries. The maximum degree of ionization, plasma dimensions and time evolution are in general agreement with model computations and show the generation of plasma columns 250 - 300 micrometers diameter with temperatures is congruent to 250 eV.

A L Osterheld - One of the best experts on this subject based on the ideXlab platform.

  • high power density capillary discharge plasma columns for Shorter Wavelength discharge pumped soft x ray lasers
    Physical Review E, 2002
    Co-Authors: Juan Jose Gonzalez, M Frati, J J Rocca, V N Shlyaptsev, A L Osterheld
    Abstract:

    : We report the generation of plasma columns in gas-filled capillary channels using discharge excitation powers that exceed those of previous studies by one to two orders of magnitude. Current pulses up to 200 kA and 10-90 % rise time of about 10 ns (current increase rate equivalent to 1.5 x 10(13) A/s) were utilized to excite plasmas in 3.3 and 4 mm diameter channels. Time resolved soft-x-ray spectra and pinhole images of the plasma were obtained. The experimental data and its comparison with model computations suggest that dense argon plasma columns 300 mum in diameter with electron temperatures >250 eV have been obtained. These characteristics make these plasmas of interest for extending discharge-pumped lasers to Shorter Wavelengths.

  • high power density capillary discharge plasma columns for Shorter Wavelength discharge pumped soft x ray lasers
    Physical Review E, 2002
    Co-Authors: Juan Jose Gonzalez, M Frati, J J Rocca, V N Shlyaptsev, A L Osterheld
    Abstract:

    We report the generation of plasma columns in gas-filled capillary channels using discharge excitation powers that exceed those of previous studies by one to two orders of magnitude. Current pulses up to 200 kA and 10--90 % rise time of \ensuremath{\sim}10 ns (current increase rate $\ensuremath{\sim}1.5\ifmmode\times\else\texttimes\fi{}{10}^{13}\mathrm{A}/\mathrm{s})$ were utilized to excite plasmas in 3.3 and 4 mm diameter channels. Time resolved soft-x-ray spectra and pinhole images of the plasma were obtained. The experimental data and its comparison with model computations suggest that dense argon plasma columns 300 \ensuremath{\mu}m in diameter with electron temperatures g250 eV have been obtained. These characteristics make these plasmas of interest for extending discharge-pumped lasers to Shorter Wavelengths.

Holekere R Chandrasekhar - One of the best experts on this subject based on the ideXlab platform.

  • 3518 use of a Shorter Wavelength autofluorescence band in barrett s esophagus effect of dysplasia and inflammation
    Gastrointestinal Endoscopy, 2000
    Co-Authors: Bhaskar Banerjee, Sangeeta Agarwal, Shreenivasa Jonnalagada, Holekere R Chandrasekhar
    Abstract:

    INTRODUCTION: Most work on autofluorescence spectroscopy has been done at emission Wavelengths greater than 450 nm. The use of a Shorter Wavelength emission band was studied in Barrett’s esophagus to observe the effects of dysplasia and inflammation. METHODS: Endoscopically obtained tissue samples were were snap frozen inliquid Nitrogen and stored at -70 Celcius. Prior to measurements, samples were thawed over ice and moistened over phosphate buffered saline at pH 7.4 (PBS). A spectrometer with a Xenon lamp and excitation and emission spectrometers (Shimatzu RF-5301 PC Columbia,MD) was used, with a specially constructed tissue holder placed in its measuring chamber. Tissue was excited below 350 nm and the maximum intensity of an emission peak below 450 nm was measured. Emission intensity in arbitrary units (y-axis) was plotted against Wavelength (x-axis). The intensities of intestinal metaplasia (n= 21 ) low grade dysplasia (n= 12) and esophagitis (n= 10)were expressed as a ratio of the corresponding emission intensity of normal squamous mucosa (n= 43) in each patient. RESULTS:The ratios of mean emission intensity ± SE were: 0.63 ± 0.06 (intestinal metaplasia); 2.07 ± 0.26 (low grade dysplasia); 0.62 ± 0.03 (esophagitis). The differences between groups (by ANOVA) were significant (p ≤ 0.0001). CONCLUSIONS: Changes in the intensity of this emission band can differentiate between low grade dysplasia (increased intensity) and inflammation (decreased intensity) when compared to normal squamous mucosa. This emission band also allows columnar epithelium to be distinguished from squamous epithelium. Further work with a hand held portable fiberoptic spectrometer is planned.

  • 4491 use of a Shorter Wavelength autofluorescence band to separate adenomatous from hyperplastic polyps of the colon
    Gastrointestinal Endoscopy, 2000
    Co-Authors: Bhaskar Banerjee, Sangeeta Agarwal, Holekere R Chandrasekhar, Brent Miedema, Rodney Perez
    Abstract:

    INTRODUCTION: The majority of work on autofluorescence has been at emission Wavelengths greater than 450 nm. A short wavelentgh emission band was investigated to see if it could distinguish hyperplastic from adenomatous polyps of the colon. METHODS: Endoscopically obtained tissue samples were snap frozen in liquid Nitrogen and stored at -70 Celcius. For each specimen, a sample of normal colonic mucosa from the same patient served as control. Prior to spectroscopy, all samples were thawed over ice and moistened in PBS at pH of 7.4. A spectrofluorometer with a Xenon lamp and excitation and emission spectrometers (Shimatzu RF- 5301 PC Columbia, MD)was used, with a specially constructed tissue holder placed in its measuring chamber. Tissue samples were excited at wavelengts below 350 nm and the maximum intensity of an emission peak below 450 nm digitally recorded. Intensity in arbitrary units (y- axis) were plotted against Wavelength (x- axis). All tissue samples were fixed in Formalin and submitted for histology. The emission intensities of hyperplastic polyps (n= 15) and adenomatous polyps (n= 22) were expressed as a ratio of the corresponding fluorescence intensity of normal colonic mucosa (n= 37) in each patient. RESULTS: The ratios of mean emission intensity ± SE were: 1.35 ± 0.07 (hyperplastic) and 2.22 ± 0.12 (adenomatous). The difference between groups (unpaired t test) was significant (p ≤ 0.0001). CONCLUSIONS: The intensity of this emission band increses with adenomatous change, with significant separation between histologic groups. The use of this autofluorescence band during screening flexible sigmoidoscopy may help to distinguish adenomatous polyps from hyperplastic ones in real time. The need to wait for biopsy results could be avoided. Patients with hyperplastic polyps could be advised not to have a colonoscopy at the end of screening flexible sigmoidoscopy, without the need to wait for biopsy results. Unlike chromoendoscopy, this technique will not require any dye or exogenous chemicals. Further work using a hand held, portable fiberoptic spectrometer is being planned.

Juan Jose Gonzalez - One of the best experts on this subject based on the ideXlab platform.

  • high power density capillary discharge plasma columns for Shorter Wavelength discharge pumped soft x ray lasers
    Physical Review E, 2002
    Co-Authors: Juan Jose Gonzalez, M Frati, J J Rocca, V N Shlyaptsev, A L Osterheld
    Abstract:

    : We report the generation of plasma columns in gas-filled capillary channels using discharge excitation powers that exceed those of previous studies by one to two orders of magnitude. Current pulses up to 200 kA and 10-90 % rise time of about 10 ns (current increase rate equivalent to 1.5 x 10(13) A/s) were utilized to excite plasmas in 3.3 and 4 mm diameter channels. Time resolved soft-x-ray spectra and pinhole images of the plasma were obtained. The experimental data and its comparison with model computations suggest that dense argon plasma columns 300 mum in diameter with electron temperatures >250 eV have been obtained. These characteristics make these plasmas of interest for extending discharge-pumped lasers to Shorter Wavelengths.

  • high power density capillary discharge plasma columns for Shorter Wavelength discharge pumped soft x ray lasers
    Physical Review E, 2002
    Co-Authors: Juan Jose Gonzalez, M Frati, J J Rocca, V N Shlyaptsev, A L Osterheld
    Abstract:

    We report the generation of plasma columns in gas-filled capillary channels using discharge excitation powers that exceed those of previous studies by one to two orders of magnitude. Current pulses up to 200 kA and 10--90 % rise time of \ensuremath{\sim}10 ns (current increase rate $\ensuremath{\sim}1.5\ifmmode\times\else\texttimes\fi{}{10}^{13}\mathrm{A}/\mathrm{s})$ were utilized to excite plasmas in 3.3 and 4 mm diameter channels. Time resolved soft-x-ray spectra and pinhole images of the plasma were obtained. The experimental data and its comparison with model computations suggest that dense argon plasma columns 300 \ensuremath{\mu}m in diameter with electron temperatures g250 eV have been obtained. These characteristics make these plasmas of interest for extending discharge-pumped lasers to Shorter Wavelengths.

  • generation of plasma columns for Shorter Wavelength capillary discharge soft x ray lasers utilizing a high power blumlein generator
    SPIE's International Symposium on Optical Science Engineering and Instrumentation, 1999
    Co-Authors: Juan Jose Gonzalez, M Frati, J J Rocca, V N Shlyaptsev
    Abstract:

    Capillary discharge plasmas were generated with current pulses up to 200 kA and 10 - 90% rise time of about 10 ns using a water dielectric Blumlein generator. Time resolve spectra and pinhole images of the plasma columns generated in ceramic capillaries are presented. The data indicates that the plasma obtain in ceramic capillaries are hotter than those generated in polyacetal capillaries. The maximum degree of ionization, plasma dimensions and time evolution are in general agreement with model computations and show the generation of plasma columns 250 - 300 micrometers diameter with temperatures is congruent to 250 eV.

J J Rocca - One of the best experts on this subject based on the ideXlab platform.

  • high power density capillary discharge plasma columns for Shorter Wavelength discharge pumped soft x ray lasers
    Physical Review E, 2002
    Co-Authors: Juan Jose Gonzalez, M Frati, J J Rocca, V N Shlyaptsev, A L Osterheld
    Abstract:

    : We report the generation of plasma columns in gas-filled capillary channels using discharge excitation powers that exceed those of previous studies by one to two orders of magnitude. Current pulses up to 200 kA and 10-90 % rise time of about 10 ns (current increase rate equivalent to 1.5 x 10(13) A/s) were utilized to excite plasmas in 3.3 and 4 mm diameter channels. Time resolved soft-x-ray spectra and pinhole images of the plasma were obtained. The experimental data and its comparison with model computations suggest that dense argon plasma columns 300 mum in diameter with electron temperatures >250 eV have been obtained. These characteristics make these plasmas of interest for extending discharge-pumped lasers to Shorter Wavelengths.

  • high power density capillary discharge plasma columns for Shorter Wavelength discharge pumped soft x ray lasers
    Physical Review E, 2002
    Co-Authors: Juan Jose Gonzalez, M Frati, J J Rocca, V N Shlyaptsev, A L Osterheld
    Abstract:

    We report the generation of plasma columns in gas-filled capillary channels using discharge excitation powers that exceed those of previous studies by one to two orders of magnitude. Current pulses up to 200 kA and 10--90 % rise time of \ensuremath{\sim}10 ns (current increase rate $\ensuremath{\sim}1.5\ifmmode\times\else\texttimes\fi{}{10}^{13}\mathrm{A}/\mathrm{s})$ were utilized to excite plasmas in 3.3 and 4 mm diameter channels. Time resolved soft-x-ray spectra and pinhole images of the plasma were obtained. The experimental data and its comparison with model computations suggest that dense argon plasma columns 300 \ensuremath{\mu}m in diameter with electron temperatures g250 eV have been obtained. These characteristics make these plasmas of interest for extending discharge-pumped lasers to Shorter Wavelengths.

  • generation of plasma columns for Shorter Wavelength capillary discharge soft x ray lasers utilizing a high power blumlein generator
    SPIE's International Symposium on Optical Science Engineering and Instrumentation, 1999
    Co-Authors: Juan Jose Gonzalez, M Frati, J J Rocca, V N Shlyaptsev
    Abstract:

    Capillary discharge plasmas were generated with current pulses up to 200 kA and 10 - 90% rise time of about 10 ns using a water dielectric Blumlein generator. Time resolve spectra and pinhole images of the plasma columns generated in ceramic capillaries are presented. The data indicates that the plasma obtain in ceramic capillaries are hotter than those generated in polyacetal capillaries. The maximum degree of ionization, plasma dimensions and time evolution are in general agreement with model computations and show the generation of plasma columns 250 - 300 micrometers diameter with temperatures is congruent to 250 eV.