| 1. |
- Heinzl, Thomas, et al.
(författare)
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Detecting radiation reaction at moderate laser intensities
- 2015
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Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - 1539-3755 .- 1550-2376. ; 91:2
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Tidskriftsartikel (refereegranskat)abstract
- We propose a new method of detecting radiation reaction effects in the motion of particles subjected to laser pulses of moderate intensity and long duration. The effect becomes sizable for particles that gain almost no energy through the interaction with the laser pulse. Hence, there are regions of parameter space in which radiation reaction is actually the dominant influence on charged particle motion.
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| 2. |
- Lindholm, Daniel, 1982-, et al.
(författare)
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Biomarker-Based Risk Model to Predict Cardiovascular Mortality in Patients With Stable Coronary Disease
- 2017
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Ingår i: Journal of the American College of Cardiology. - : Elsevier. - 0735-1097 .- 1558-3597. ; 70:7, s. 813-826
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Tidskriftsartikel (refereegranskat)abstract
- Background Currently, there is no generally accepted model to predict outcomes in stable coronary heart disease (CHD).Objectives This study evaluated and compared the prognostic value of biomarkers and clinical variables to develop a biomarker-based prediction model in patients with stable CHD.Methods In a prospective, randomized trial cohort of 13,164 patients with stable CHD, we analyzed several candidate biomarkers and clinical variables and used multivariable Cox regression to develop a clinical prediction model based on the most important markers. The primary outcome was cardiovascular (CV) death, but model performance was also explored for other key outcomes. It was internally bootstrap validated, and externally validated in 1,547 patients in another study.Results During a median follow-up of 3.7 years, there were 591 cases of CV death. The 3 most important biomarkers were N-terminal pro–B-type natriuretic peptide (NT-proBNP), high-sensitivity cardiac troponin T (hs-cTnT), and low-density lipoprotein cholesterol, where NT-proBNP and hs-cTnT had greater prognostic value than any other biomarker or clinical variable. The final prediction model included age (A), biomarkers (B) (NT-proBNP, hs-cTnT, and low-density lipoprotein cholesterol), and clinical variables (C) (smoking, diabetes mellitus, and peripheral arterial disease). This “ABC-CHD” model had high discriminatory ability for CV death (c-index 0.81 in derivation cohort, 0.78 in validation cohort), with adequate calibration in both cohorts.Conclusions This model provided a robust tool for the prediction of CV death in patients with stable CHD. As it is based on a small number of readily available biomarkers and clinical factors, it can be widely employed to complement clinical assessment and guide management based on CV risk. (The Stabilization of Atherosclerotic Plaque by Initiation of Darapladib Therapy Trial [STABILITY]; NCT00799903)
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| 3. |
- Behm, K. T., et al.
(författare)
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A spectrometer for ultrashort gamma-ray pulses with photon energies greater than 10 MeV
- 2018
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 89:11
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Tidskriftsartikel (refereegranskat)abstract
- © 2018 Author(s). We present a design for a pixelated scintillator based gamma-ray spectrometer for non-linear inverse Compton scattering experiments. By colliding a laser wakefield accelerated electron beam with a tightly focused, intense laser pulse, gamma-ray photons up to 100 MeV energies and with few femtosecond duration may be produced. To measure the energy spectrum and angular distribution, a 33 × 47 array of cesium-iodide crystals was oriented such that the 47 crystal length axis was parallel to the gamma-ray beam and the 33 crystal length axis was oriented in the vertical direction. Using an iterative deconvolution method similar to the YOGI code, modeling of the scintillator response using GEANT4 and fitting to a quantum Monte Carlo calculated photon spectrum, we are able to extract the gamma ray spectra generated by the inverse Compton interaction.
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| 4. |
- Cole, J. M., et al.
(författare)
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Experimental Evidence of Radiation Reaction in the Collision of a High-Intensity Laser Pulse with a Laser-Wakefield Accelerated Electron Beam
- 2018
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Ingår i: Physical Review X. - 2160-3308. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of energetic particles in strong electromagnetic fields can be heavily influenced by the energy loss arising from the emission of radiation during acceleration, known as radiation reaction. When interacting with a high-energy electron beam, today's lasers are sufficiently intense to explore the transition between the classical and quantum radiation reaction regimes. We present evidence of radiation reaction in the collision of an ultrarelativistic electron beam generated by laser-wakefield acceleration (μ 500 MeV) with an intense laser pulse (a0 > 10). We measure an energy loss in the postcollision electron spectrum that is correlated with the detected signal of hard photons (γ rays), consistent with a quantum description of radiation reaction. The generated γ rays have the highest energies yet reported from an all-optical inverse Compton scattering scheme, with critical energy > 30 MeV.
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| 5. |
- Dinu, Victor, et al.
(författare)
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Quantum Radiation Reaction: From Interference to Incoherence
- 2016
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 116:4
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Tidskriftsartikel (refereegranskat)abstract
- We investigate quantum radiation reaction in laser-electron interactions across different energy and intensity regimes. Using a fully quantum approach which also accounts exactly for the effect of the strong laser pulse on the electron motion, we identify in particular a regime in which radiation reaction is dominated by quantum interference. We find signatures of quantum radiation reaction in the electron spectra which have no classical analogue and which cannot be captured by the incoherent approximations typically used in the high-intensity regime. These signatures are measurable with presently available laser and accelerator technology.
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| 6. |
- Harvey, Christopher, 1982, et al.
(författare)
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Focusing effects in laser-electron Thomson scattering
- 2016
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Ingår i: Physical Review Special Topics - Accelerators and Beams. - 1098-4402. ; 19:9
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Tidskriftsartikel (refereegranskat)abstract
- We study the effects of laser pulse focusing on the spectral properties of Thomson scattered radiation. Modeling the laser as a paraxial beam we find that, in all but the most extreme cases of focusing, the temporal envelope has a much bigger effect on the spectrum than the focusing itself. For the case of ultrashort pulses, where the paraxial model is no longer valid, we adopt a subcycle vector beam description of the field. It is found that the emission harmonics are blue shifted and broaden out in frequency space as the pulse becomes shorter. Additionally the carrier envelope phase becomes important, resulting in an angular asymmetry in the spectrum. We then use the same model to study the effects of focusing beyond the limit where the paraxial expansion is valid. It is found that fields focussed to subwavelength spot sizes produce spectra that are qualitatively similar to those from subcycle pulses due to the shortening of the pulse with focusing. Finally, we study high-intensity fields and find that, in general, the focusing makes negligible difference to the spectra in the regime of radiation reaction.
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| 7. |
- Harvey, Christopher, 1982, et al.
(författare)
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High-energy gamma-ray beams from nonlinear Thomson and Compton scattering in the ultra-intense regime
- 2015
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9781628416305 ; 9509, s. 950908-
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Konferensbidrag (refereegranskat)abstract
- We consider the Thomson and Compton scattering of high-energy electrons in an intense laser pulse. Our simulations show that energy losses due to radiation reaction cause the emitted radiation to be spread over a broader angular range than the case without these losses included. We explain this in terms of the effect of these energy losses on the particle dynamics. Finally, at ultra-high intensities, i.e. fields with a dimensionless parameter a(0)similar to 200, the energy of the emission spectrum is significantly reduced by radiation reaction and also the classical and QED results begin to differ. This is found to be due to the classical theory overestimating the energy loss of the electrons. Such findings are relevant to radiation source development involving the next generation of high-intensity laser facilities.
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| 8. |
- Harvey, Christopher, 1982
(författare)
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In situ characterization of ultraintense laser pulses
- 2018
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Ingår i: Physical Review Accelerators and Beams. - 2469-9888. ; 21:11
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Tidskriftsartikel (refereegranskat)abstract
- We present a method for determining the characteristics of an intense laser pulse by probing it with a relativistic electron beam. After an initial burst of very high-energy γ-radiation the electrons proceed to emit a series of attosecond duration x-ray pulses as they leave the field. These flashes provide detailed information about the interaction, allowing us to determine properties of the laser pulse: something that is currently a challenge for ultrahigh intensity laser systems.
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| 9. |
- Harvey, Christopher, 1982, et al.
(författare)
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Narrowing of the emission angle in high-intensity Compton scattering
- 2016
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Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - : American Physical Society. - 2469-9926 .- 2469-9934 .- 1050-2947 .- 1094-1622. ; 93:2
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Tidskriftsartikel (refereegranskat)abstract
- We consider the emission spectrum of high-energy electrons in an intense laser field. At high intensities (a_0 \sim 200) we find that the QED theory predicts a narrower angular spread of emissions than the classical theory. This is due to the classical theory overestimating the energy loss of the particles, resulting in them becoming more susceptible to reflection in the laser pulse.
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| 10. |
- Harvey, Christopher, 1982, et al.
(författare)
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Numerical modelling of Compton scattering in ultra-intense laser pulses
- 2015
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 594:1
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Konferensbidrag (refereegranskat)abstract
- We examine current methods of numerically implementing Compton scattering in the context of intense laser-matter interactions. In a recent publication [1] it has been shown that a commonly used approach generates the correct spectra in nearly all cases, except those when the harmonic structure is important. Here we provide an explanation for this using an alternative, classical argument.
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