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Author: Asova, G. ×

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    Experimentally minimized beam emittance from an L-band photoinjector
    (College Park : American Institute of Physics Inc., 2012) Krasilnikov, M.; Stephan, F.; Asova, G.; Grabosch, H.-J.; Groß, M.; Hakobyan, L.; Isaev, I.; Ivanisenko, Y.; Jachmann, L.; Khojoyan, M.; Klemz, G.; Köhler, W.; Mahgoub, M.; Malyutin, D.; Nozdrin, M.; Oppelt, A.; Otevrel, M.; Petrosyan, B.; Rimjaem, S.; Shapovalov, A.; Vashchenko, G.; Weidinger, S.; Wenndorff, R.; Flöttmann, K.; Hoffmann, M.; Lederer, S.; Schlarb, H.; Schreiber, S.; Templin, I.; Will, I.; Paramonov, V.; Richter, D.
    High brightness electron sources for linac based free-electron lasers (FELs) are being developed at the Photo Injector Test facility at DESY, Zeuthen site (PITZ). Production of electron bunches with extremely small transverse emittance is the focus of the PITZ scientific program. The photoinjector optimization in 2008-2009 for a bunch charge of 1, 0.5, 0.25, and 0.1nC resulted in measured emittance values which are beyond the requirements of the European XFEL. Several essential modifications were commissioned in 2010-2011 at PITZ, resulting in further improvement of the photoinjector performance. Significant improvement of the rf gun phase stability is a major contribution in the reduction of the measured transverse emittance. The old TESLA prototype booster was replaced by a new cut disk structure cavity. This allows acceleration of the electron beam to higher energies and supports much higher flexibility for stable booster operation as well as for longer rf pulses which is of vital importance especially for the emittance optimization of low charge bunches. The transverse phase space of the electron beam was optimized at PITZ for bunch charges in the range between 0.02 and 2nC, where the quality of the beam measurements was preserved by utilizing long pulse train operation. The experimental optimization yielded worldwide unprecedented low normalized emittance beams in the whole charge range studied.
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    Detailed characterization of electron sources yielding first demonstration of European x-ray free-electron laser beam quality
    (College Park, Md. : APS, 2010) Stephan, F.; Boulware, C.H.; Krasilnikov, M.; Bähr, J.; Asova, G.; Donat, A.; Gensch, U.; Grabosch, H.J.; Hänel, M.; Hakobyan, L.; Henschel, H.; Ivanisenko, Y.; Jachmann, L.; Khodyachykh, S.; Khojoyan, M.; Kohler, W.; Korepanov, S.; Koss, G.; Kretzschmann, A.; Leich, H.; Ludecke, H.; Meissner, A.; Oppelt, A.; Petrosyan, B.; Pohl, M.; Riemann, S.; Rimjaem, S.; Sachwitz, M.; Schoneich, B.; Scholz, T.; Schulze, H.; Schultze, J.; Schwendicke, U.; Shapovalov, A.; Spesyvtsev, R.; Staykov, L.; Tonisch, F.; Walter, T.; Weisse, S.; Wenndorff, R.; Winde, M.; Vu, L.V.; Durr, H.; Kamps, T.; Richter, D.; Sperling, M.; Ovsyannikov, R.; Vollmer, A.; Knobloch, J.; Jaeschke, E.; Boster, J.; Brinkmann, R.; Choroba, S.; Flechsenhar, K.; Flottmann, K.; Gerdau, W.; Katalev, V.; Koprek, W.; Lederer, S.; Martens, C.; Pucyk, P.; Schreiber, S.; Simrock, S.; Vogel, E.; Vogel, V.; Rosbach, K.; Bonev, I.; Tsakov, I.; Michelato, P.; Monaco, L.; Pagani, C.; Sertore, D.; Garvey, T.; Will, I.; Templin, I.; Sandner, W.; Ackermann, W.; Arévalo, E.; Gjonaj, E.; Muller, W.F.O.; Schnepp, S.; Weiland, T.; Wolfheimer, F.; Ronsch, J.; Rossbach, J.
    The photoinjector test facility at DESY, Zeuthen site (PITZ), was built to develop and optimize photoelectron sources for superconducting linacs for high-brilliance, short-wavelength free-electron laser (FEL) applications like the free-electron laser in Hamburg (FLASH) and the European x-ray free-electron laser (XFEL). In this paper, the detailed characterization of two laser-driven rf guns with different operating conditions is described. One experimental optimization of the beam parameters was performed at an accelerating gradient of about 43 MV/m at the photocathode and the other at about 60 MV/m. In both cases, electron beams with very high phase-space density have been demonstrated at a bunch charge of 1 nC and are compared with corresponding simulations. The rf gun optimized for the lower gradient has surpassed all the FLASH requirements on beam quality and rf parameters (gradient, rf pulse length, repetition rate) and serves as a spare gun for this facility. The rf gun studied with increased accelerating gradient at the cathode produced beams with even higher brightness, yielding the first demonstration of the beam quality required for driving the European XFEL: The geometric mean of the normalized projected rms emittance in the two transverse directions was measured to be 1.260±13 mmmrad for a 1-nC electron bunch. When a 10% charge cut is applied excluding electrons from those phase-space regions where the measured phase-space density is below a certain level and which are not expected to contribute to the lasing process, the normalized projected rms emittance is about 0.9 mmmrad. © 2010 The American Physical Society.