| 1. |
- Ziemann, Ingvar, et al.
(författare)
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Noninvasively improving the orbit-response matrix while continuously correcting the orbit
- 2021
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Ingår i: Physical Review Accelerators and Beams. - : American Physical Society (APS). - 2469-9888. ; 24:7
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Tidskriftsartikel (refereegranskat)abstract
- Based on continuously recorded beam positions and corrector excitations from, for example, a closedorbit feedback system we describe an algorithm that continuously updates an estimate of the orbit response matrix. The speed of convergence can be increased by adding very small perturbations, so-called dither, to the corrector excitations. Estimates for the rate of convergence and the asymptotically achievable accuracies are provided.
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| 2. |
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| 3. |
- Adli, E., et al.
(författare)
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X-band rf power production and deceleration in the two-beam test stand of the Compact Linear Collider test facility
- 2011
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Ingår i: Physical Review Special Topics - Accelerators and Beams. - 1098-4402. ; 14:8, s. 081001-
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Tidskriftsartikel (refereegranskat)abstract
- We discuss X-band rf power production and deceleration in the two-beam test stand of the CLIC test facility at CERN. The rf power is extracted from an electron drive beam by a specially designed power extraction structure. In order to test the structures at high-power levels, part of the generated power is recirculated to an input port, thus allowing for increased deceleration and power levels within the structure. The degree of recirculation is controlled by a splitter and phase shifter. We present a model that describes the system and validate it with measurements over a wide range of parameters. Moreover, by correlating rf power measurements with the energy lost by the electron beam, as measured in a spectrometer placed after the power extraction structure, we are able to identify system parameters, including the form factor of the electron beam. The quality of the agreement between model and reality gives us confidence to extrapolate the results found in the present test facility towards the parameter regime of CLIC.
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| 4. |
- Ali, Hasan, 1985-, et al.
(författare)
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An electron energy loss spectrometer based streak camera for time resolved TEM measurements
- 2017
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Ingår i: Ultramicroscopy. - : Elsevier BV. - 0304-3991 .- 1879-2723. ; 176, s. 5-10
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Tidskriftsartikel (refereegranskat)abstract
- We propose an experimental setup based on a streak camera approach inside an energy filter to measure time resolved properties of materials in the transmission electron microscope (TEM). In order to put in place the streak camera, a beam sweeper was built inside an energy filter. After exciting the TEM sample, the beam is swept across the CCD camera of the filter. We describe different parts of the setup at the example of a magnetic measurement. This setup is capable to acquire time resolved diffraction patterns, electron energy loss spectra (EELS) and images with total streaking times in the range between 100 ns and 10 μs.
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| 5. |
- Andersson Sundén, Erik, et al.
(författare)
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Citizen Science and Radioactivity
- 2019
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Ingår i: Nuclear Physics News. - : Informa UK Limited. - 1050-6896 .- 1061-9127 .- 1931-7336. ; 29:2, s. 25-28
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 6. |
- Angelova, G., et al.
(författare)
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Observation of two-dimensional longitudinal-transverse correlations in an electron beam by laser-electron interactions
- 2008
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Ingår i: Physical Review Special Topics - Accelerators and Beams. - 1098-4402. ; 11:7
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Tidskriftsartikel (refereegranskat)abstract
- During the preparatory work for the optical-replica synthesizer experiment in the free-electron laser FLASH at DESY, we were able to superimpose a short, approximately 200 fs long pulse from a frequencydoubled mode-locked erbium laser with titanium-sapphire amplifier and an approximately 20 ps long electron bunch in an undulator. This induces an energy modulation in a longitudinal slice of the electron bunch. A magnetic chicane downstream of the undulator converts the energy modulation into a density modulation within the slice that causes the emission of coherent optical transition radiation from a silver-coated silicon screen. Varying the relative timing between electron and laser, we use a camera to record two-dimensional images of the slices as a function of the longitudinal position within the electron bunch.
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| 7. |
- Angelova, Gergana, et al.
(författare)
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Results from the optical replica experiment at Flash
- 2008
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Ingår i: 30th International Free Electron laser Conference in Gyeongju, Agust 24-29, 2008.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Experimental results from the optical replica synthesizer (ORS) at FLASH (DESY, Hamburg) are presented.The ORS is a novel method to determine the longitudinal structure of sub-ps electron bunches by creating a coherent optical pulse at 775 nm wavelength that has th same shape as the electron bunch and can be analyzed using a FROG (frequency-resolved optical gating) device. The ORS hardware was installed in 2007, comprising a Ti:Sapphire laser system, two undulators and optical equipment. During first experimetns, the spatial and temporal overlap of an uncompressed electron bunch and a 200 fs laser pulse in an undulator was achieved, modulating the electron energy and density. Coherent transition radiation from micro-bunched electrosn was observed varying the timing between electrons and laser pulse and producing two-dimensional images of slices within the electron bunch. In a second experiment, alser pulses were overlapped with compressed electron bunches in the undulator and coherent radiation from a second undulator was observed and analyzed using the FROG device.
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| 8. |
- Angelova, Gergana, et al.
(författare)
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Results from the Optical Replica Experiment in FLASH
- 2008
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Ingår i: Proceedings of the European particle Accelerator Conference EPAC08.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We present experimental results from the optical replica synthesizer, a novel device to diagnose sub-ps electron bunches by creating a coherent optical pulse in the infrared that has the envelope of the electron bunch and analyzing the latter by frequency resolved optical gating methods. Such a device was recently installed in FLASH at DESY. During a first experiment period the spatial and temporal overlap of a several ps long electron bunch and a 200\,fs laser pulse were achieved within an undulator. Coherent transitionradiation due to the induced micro-bunching was observed on a silver-coated silicon screen and varying the timing between electrons and laser pulse produced two-dimensional images of the slices as a function of the longitudinal position within the electron bunch. During a second experiment period the strongly compressed electron bunch is modulated by the laser pulse and replica pulses that are emitted from a second undulator are observed by frequency resolved optical gating methods.
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| 9. |
- Angelova, Gergana, et al.
(författare)
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The XFEL Laser Heater
- 2008
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Ingår i: Proceedings of the European particle Accelerator Conference EPAC08.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The high-brilliance photo-cathode gun foreseen for the X-FEL will provide beams with extremely small momentum spread that will make the beam susceptible to micro-bunching instabilities which will spoil SASE operation. It is therefore desirable to increase the momentum spread to a level that prevents these instabilities but still is compatible with SASE operation. The laser heater will achieve this by superimposing a transversely polarized laser and the electron beam in a properly tuned undulator, thereby producing a momentum modulation that is smeared out in a dogleg chicane to obtain the desired momentum spread increase. We present the initial design and layout of the laser heater system for the X-FEL in Hamburg.
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| 10. |
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