High-brightness, compact soft x-ray source based on Cherenkov radiation

Cherenkov radiation in the soft x-ray region is generated in narrowband regions at inner-shell absorption edges. Mainly low-Z elements are suitable Cherenkov sources, which emit in a photon energy range from 30 eV to 1 keV and require moderate electron energies up to 25 MeV. Generally, in the soft x-ray region materials are highly absorbing and therefore the Cherenkov radiation theory is discussed for absorbing media. A detailed description includes transition radiation that is generated at the interface when the relativistic electron exits the material. We show that the transition radiation yield equation, when it is adopted for an absorbing medium, includes Cherenkov radiation. Based on this approach it is shown that the spectral intensity of Cherenkov radiation in the soft x-ray region is large compared to transition radiation for moderate electron energies. First measurements of soft x-ray Cherenkov radiation in the water-window spectral region, generated in titanium and vanadium foils, are discussed in detail. The measured spectral and angular distribution of the radiation, and the measured total yield (≈ 10 -4 photon per electron) are in agreement with theoretical predictions based on the refractive index data. We show that the brightness that can be achieved using a small electron accelerator is sufficient for practical x-ray microscopy in the water window.</p

High-brightness, compact soft x-ray source based on Cherenkov radiation

\u3cp\u3eCherenkov radiation in the soft x-ray region is generated in narrowband regions at inner-shell absorption edges. Mainly low-Z elements are suitable Cherenkov sources, which emit in a photon energy range from 30 eV to 1 keV and require moderate electron energies up to 25 MeV. Generally, in the soft x-ray region materials are highly absorbing and therefore the Cherenkov radiation theory is discussed for absorbing media. A detailed description includes transition radiation that is generated at the interface when the relativistic electron exits the material. We show that the transition radiation yield equation, when it is adopted for an absorbing medium, includes Cherenkov radiation. Based on this approach it is shown that the spectral intensity of Cherenkov radiation in the soft x-ray region is large compared to transition radiation for moderate electron energies. First measurements of soft x-ray Cherenkov radiation in the water-window spectral region, generated in titanium and vanadium foils, are discussed in detail. The measured spectral and angular distribution of the radiation, and the measured total yield (≈ 10 \u3csup\u3e-4\u3c/sup\u3e photon per electron) are in agreement with theoretical predictions based on the refractive index data. We show that the brightness that can be achieved using a small electron accelerator is sufficient for practical x-ray microscopy in the water window.\u3c/p\u3

Observation of narrow-band Si L-edge Cherenkov radiation generated by 5 MeV electrons

Narrow-band Cerenkov radiation at 99.7 eV has been generated by 5 MeV electrons in a silicon foil, with a yield similar to 1x10(-3) photon/electron. These measurements demonstrate the feasibility of a compact, narrow-band, and intense soft x-ray source based on small electron accelerators. The observed yield and dependence of the photon spectrum on emission angle are in agreement with theoretical predictions for Cerenkov radiation based on refractive index data of silicon. (C) 2001 American Institute of Physics

High-brightness, compact soft x-ray source based on Cherenkov radiation

Cherenkov radiation in the soft x-ray region is generated in narrowband regions at inner-shell absorption edges. Mainly low-Z elements are suitable Cherenkov sources, which emit in a photon energy range from 30 eV to 1 keV and require moderate electron energies up to 25 MeV. Generally, in the soft x-ray region materials are highly absorbing and therefore the Cherenkov radiation theory is discussed for absorbing media. A detailed description includes transition radiation that is generated at the interface when the relativistic electron exits the material. We show that the transition radiation yield equation, when it is adopted for an absorbing medium, includes Cherenkov radiation. Based on this approach it is shown that the spectral intensity of Cherenkov radiation in the soft x-ray region is large compared to transition radiation for moderate electron energies. First measurements of soft x-ray Cherenkov radiation in the water-window spectral region, generated in titanium and vanadium foils, are discussed in detail. The measured spectral and angular distribution of the radiation, and the measured total yield (≈ 10 -4 photon per electron) are in agreement with theoretical predictions based on the refractive index data. We show that the brightness that can be achieved using a small electron accelerator is sufficient for practical x-ray microscopy in the water window

Soft X-ray monochromatisation using a multilayer-single crystal combination

A method of monochromatising soft X-rays by using multilayers in combination with organic crystals is presented. An energy resolution of 0.1% has been achieved at ca. 800 eV. The combination can be used for high resolution studies in the energy range 500-800 eV, which is difficult to cover using either inorganic double crystals or grating monochromator

Spectral characteristics of an advanced x-ray generator at the KIPT based on compton back-scattering

An international co-operative project to develop an advanced X-ray source on the basis of Compton back-scattering is described. The goal is the re-configuration of the Kharkov Institute of Physics and Technology (KIPT) N-100 storage ring to support the efficient interaction of its electron beam with a high power pulsed-laser cavity. At equilibrium both the electron and X-ray beams' phase space characteristics are determined by a balance of stochastic photon cooling and emission. In this paper the operating parameters and fundamental spectral and temporal properties of the novel source are summarized and the potential for its development into an ultra-short pulse source is discussed.</p

Nasal gene expression differentiates COPD from controls and overlaps bronchial gene expression

Background: Nasal gene expression profiling is a promising method to characterize COPD non-invasively. We aimed to identify a nasal gene expression profile to distinguish COPD patients from healthy controls. We investigated whether this COPD-associated gene expression profile in nasal epithelium is comparable with the profile observed in bronchial epithelium.Methods: Genome wide gene expression analysis was performed on nasal epithelial brushes of 31 severe COPD patients and 22 controls, all current smokers, using Affymetrix Human Gene 1.0 ST Arrays. We repeated the gene expression analysis on bronchial epithelial brushes in 2 independent cohorts of mild-to-moderate COPD patients and controls.Results: In nasal epithelium, 135 genes were significantly differentially expressed between severe COPD patients and controls, 21 being up-and 114 downregulated in COPD (false discovery rate &lt;0.01). Gene Set Enrichment Analysis (GSEA) showed significant concordant enrichment of COPD-associated nasal and bronchial gene expression in both independent cohorts (FDRGSEA &lt;0.001).Conclusion: We identified a nasal gene expression profile that differentiates severe COPD patients from controls. Of interest, part of the nasal gene expression changes in COPD mimics differentially expressed genes in the bronchus. These findings indicate that nasal gene expression profiling is potentially useful as a non-invasive biomarker in COPD.</p

Spectral characteristics of an advanced x-ray generator at the KIPT based on compton back-scattering

An international co-operative project to develop an advanced X-ray source on the basis of Compton back-scattering is described. The goal is the re-configuration of the Kharkov Institute of Physics and Technology (KIPT) N-100 storage ring to support the efficient interaction of its electron beam with a high power pulsed-laser cavity. At equilibrium both the electron and X-ray beams' phase space characteristics are determined by a balance of stochastic photon cooling and emission. In this paper the operating parameters and fundamental spectral and temporal properties of the novel source are summarized and the potential for its development into an ultra-short pulse source is discussed

Additional file 1: of Nasal gene expression differentiates COPD from controls and overlaps bronchial gene expression

Supplement details on study design and additional results. (PDF 1068 kb