Optimierung und Charakterisierung des Free Electron Lasers am Speicherring DELTA

Free Electron Laser erzeugen hochbrillante, ultrakurze Laserpulse variabler Wellenlänge und kombinieren somit die Vorteile von Synchrotronstrahlung und Laser. Im Rahmen dieser Arbeit wurde der FEL-Oszillator am Speicherring DELTA hinsichtlich Geschwindigkeit und Reproduzierbarkeit der gesamten Justageprozedur optimiert, um einen stabilen FEL-Betrieb für beschleunigerphysikalische Experimente zu etablieren. Damit war erstmalig die Messung und Untersuchung der Zusammenhänge zwischen Gain, Ausgangsleistung und Pulsstruktur des Lasers, und des Strahlstroms, der Energiebreite und der longitudinalen Dynamik des Elektronenstrahls bei DELTA möglich. Zu diesem Zweck wurden neue Spiegelkammern und Spiegelsteuerungen für den optischen Resonator konstruiert. Der FEL konnte erfolgreich wieder in Betrieb genommen werden, so dass im zweiten Teil dieser Arbeit eine weitreichende Charakterisierung der erzeugten Laserstrahlung im sichtbaren Bereich erfolgte. Lasing wurde mit unterschiedlichen Füllstrukturen im Speicherring und unterschiedlichen Laserpulsstrukturen erzielt. Mithilfe des optischen Klystrons wurde die Energiebreite des Elektronenstrahls direkt, unabhängig von der Bunchlänge gemessen. Der Gain und die Leistung des FELs wurden gemessen und mit den theoretischen Modellen, insbesondere dem Low-Gain-Modell und dem Renieri-Limit, verglichen. Hierdurch konnte gezeigt werden, dass das Einsetzen des FEL-Prozesses eine dämpfende Wirkung auf die Energiebreite des Elektronenstrahls hat; die turbulente Bunchverlängerung wird ganz oder zum Teil außer Kraft gesetzt

Competition in the Workplace: An Experimental Investigation

We analyze competition between workers in a gift-exchange experiment where two workers are hired by the same employer. In the competition treatment the two employees simultaneously choose their effort whereas in the baseline treatment competition cannot occur since there is only one employee per employer. We find that in the competition treatment employers implicitly set tournament incentives by rewarding employees who choose higher effort levels than their co-workers. Here, employees' effort levels increase significantly faster, which can be explained by imitation learning. Furthermore we find that employers decrease their wage payments per unit of effort exerted over time when employing two workers

A short-pulse facility for time and angle-resolved photoe-mission experiments at the synchrotron light source DELTA

At the synchrotron light source DELTA (TU Dortmund), a short-pulsefacility is under commissioning. The U250 undulator of the storage ringis used to generate coherent sub-ps pulses at higher harmonics of aseeding laser. The VUV beamline BL5 operated by a group from PGI-6 (FZ Julich) ̈ guides those pulses into an end-station that is optimizedfor angle and spin-resolved photoemission spectroscopy experiments.A part of the seeding laser pulse is brought into the end-station via aseparate beamline and can be used as a pump beam for pump-probeexperiments. With those time and angle-resolved photoemission exper-iments that are now feasible with this unique setup we will, in the nearfuture, study magnetization dynamics of thin ferromagnetic films onmetal surfaces.The modifications of the photoemission setup that were necessaryto conduct time-resolved experiments and the current status of theshort-pulse facility will be described

Electronic Communication in C(4)-Bridged Binuclear Complexes with Paramagnetic Bisphosphane Manganese End Groups.

Building blocks for conducting polymers or NLO materials are the linear, unsaturated carbon chain bridged manganese complexes 1(n+) (n=0-2). All oxidation states were investigated spectroscopically and by X-ray structure determinations. The analytical data confirm a communication of the electrons over the C(4) chain-a prerequisite for electrical conductivity and NLO properties of oligo- or polymeric materials

Progress on the PITZ TDS

A transverse deflecting system (TDS) is under commissioning at the Photo Injector Test Facility at DESY, Zeuthen site (PITZ). The structure was designed and manufactured by the Institute for Nuclear Research (INR RAS, Moscow, Russia) as prototype for the TDS in the injector part of the European XFEL. Last year the deflection voltage was limited for safety reasons, but after thorough investigations of the waveguide system we are now able to operate the cavity close to design specifications. The PITZ TDS streaks the electron beam vertically, allowing measurements of the longitudinal bunch profile, and, in combination with a subsequent horizontal bending magnet, also of the longitudinal phase space and slice energy spread. Furthermore, several quadrupole magnets and screen stations can be employed for slice emittance measurements using the TDS. This paper describes the progress in commissioning of the hardware, measurement techniques and simulations, and outlines the prospects of reliable slice emittance measurements at 20 MeV/c, where space charge forces complicate the determination of transfer matrices