Charakterisierung einer Nicht-Neutralen-Plasmawolke : Art und Verzerrung der Intensitätsverteilung

Weiterentwicklung von Auswertealgorithmen für die Symetrieklassifizierung von 2D Intensitätsverteilunge

Wakefield Studies for a Bunch Arrival-Time Monitor Concept with Rod-Shaped Pickups on a Printed Circuit Board for X-Ray Free-Electron Lasers

The European XFEL (EuXFEL) and other notable X-ray Free-Electron Laser facilities rely on an all-optical synchronization system with electro-optical bunch arrival-time monitors (BAM). The current BAMs were benchmarked with a resolution of 3.5 fs for nominal 250 pC bunches at the EuXFEL, including jitter of the optical reference system. The arrival-time jitter could be reduced to about 10 fs with a beam-based feedback system. For future experiments at the EuXFEL the bunch charge will be decreased to a level where the existing system’s accuracy will no longer be sufficient. In simulations a concept based on rod-shaped pickups mounted on a printed circuit board indicated its potential for such low charge applications. For the feasibility of the proposed design, its contribution to the total impedance is essential. In this work the design and an intermediate version are compared to state-of-the-art BAM regarding their wake potential. Furthermore, measures to mitigate wakefields are discussed

Bunch Arrival-Time Measurement with Rod-Shaped Pickups on a Printed Circuit Board for X-Ray Free-Electron Lasers

The all-optical synchronization system implemented in the European X-ray free-electron laser (EuXFEL) is to receive an upgrade. The modifications are intended to allow operation with consistently high accuracy in a 1 pC mode, which is required for various user experiments. The lower charges, e.g. a factor of 20, lead to a reduced signal strength at the pickups and thus to a decreased resolution. A significant potential for improvement has been identified in a modified pickup structure and transmission network, which provide the transient voltage signal to subsequent parts of the synchronization system. One solution for a broadband pickup structure with short signal paths, large active surfaces and minimum aperture diameter could be achieved by connecting rod-shaped pickups to a combination network on a printed circuit board, which will be mounted in the beamline. In this contribution the proposed design is introduced and analyzed by electromagnetic field simulations

Evaluation of a Novel Pickup Concept for Ultra-Low Charged Short Bunches in X-Ray Free-Electron Lasers

The all-optical synchronization systems used in various Xray free-electron lasers (XFEL) such as the European XFEL depend on transient fields of passing electron bunches coupled into one or more pickups in the Bunch Arrival Time Monitors (BAM). The extracted signal is then amplitude modulated on reference laser pulses in a Mach-Zehnder type electro-optical modulator. With the emerging demand of the experimenters for future experiments with ultra-short FEL shots, fs precision is required for the synchronization systems even with 1 pC bunches. Since the sensitivity of the BAM depends in particular on the slope of the bipolar signal at the zero crossing and thus, also on the bunch charge, a redesign with the aim of a significant increase by optimized geometry and bandwidth is inevitable. In this contribution a possible new pickup concept is simulated and its performance is compared to the previous concept. A significant improvement of slope and voltage is found. The improvement is mainly achieved by the reduced distance to the beam and a higher bandwidth

Pickup Development for Short Low-Charge Bunches in X-Ray Free-Electron Lasers

The all-optical synchronization systems used in various x-ray free-electron lasers (XFEL) such as the European XFEL usually include bunch arrival-time monitors (BAM), which observe the transient fields of passing electron bunches through their pickups. The extracted signal is used to modulate the amplitude of a reference laser pulse in a Mach-Zehnder type electro-optical modulator. The laser pulse is typically much shorter than the voltage signal and interacts only with an instantaneous value of the applied signal. With the emerging demand for future experiments with short FEL shots, fs precision is required for the synchronization systems even with 1 pC bunches. Since the sensitivity of the BAM depends in particular on the slope of the bipolar signal at the zero crossing and thus, also on the bunch charge, a redesign with the aim of a significant increase by optimized geometry and bandwidth is inevitable. In this contribution the theoretical foundations of the pickup signal are aggregated and treated with a focus on short bunches as well as a general formulation. The analytical treatment reveals design limitations and suggests several approaches for further development. Based on these considerations a new pickup concept with possible advantages in manufacturing and temporal resolution is simulated and its performance is compared to the previous concept. The design offers good potential and a significant improvement of slope and voltage is found. Nevertheless the target set for 1 pC operation was not fully reached yet and further optimization is necessary. The observed improvement is mainly achieved by the reduced distance to the beam and a higher bandwidth

Modeling and Experimental Evaluation of a Bunch Arrival-Time Monitor with Rod-Shaped Pickups and a Low-Pi-Voltage Ultra-Wideband Traveling Wave Electro-Optic Modulator for X-Ray Free-Electron Lasers

X-ray Free-Electron Laser (XFEL) facilities, such as the 3.4-km European XFEL, use all-optical links with electro-optic bunch arrival-time monitors (BAM) for a long-range synchronization. The current BAM systems achieve a resolution of 3.5 fs for 250 pC bunches. Precise bunch arrival timing is essential for experiments, which study ultra-fast dynamical phenomena with highest temporal resolution. These experiments will crucially rely on femtosecond pulses from bunch charges well below 20 pC. The state-of-the-art BAMs are not allowing accurate timing for operation with such low bunch charges. Here we report on the progress in development of an advanced BAM (system) based on rod-shaped pickups mounted on a printed circuit board and ultra-wideband travelling-wave electro-optic modulators with low operating voltages. We perform modeling and experimental evaluation for the fabricated pickups and electro-optic modulators and analytically estimate timing jitter for the advanced BAM system. We discuss an experimental setup to demonstrate joint operation of new pickups and wideband EO modulators for low bunch charges less than 5 pC

Clinical management of large adrenal cystic lesions

The widespread use of ultrasonography and computed tomography has resulted in an increased diagnosis of large sized adrenal cysts with diameters of more than 5 cm. Most of these adrenal cystic lesions are clinically silent and are therefore often diagnosed incidentally. Since up to 7% of adrenal cysts are malignant, a careful hormonal, morpho-functional and instrumental evaluation is mandatory. In particular, functioning adrenal carcinomas or pheochromocytomas have to be ruled out. Fine needle aspiration cytology as well as examination of a punch biopsy specimen of the cystic wall are of limited value, as there is considerable overlap in cytologic and histologic features of benign and malignant adrenal cystic lesions. Immediate surgical excision is indicated in the presence of symptoms, suspicion of malignancy, increase in the size or detection of a functioning adrenal cyst. En bloc adrenalectomy, preferably by a laparoscopic approach, has become the treatment of choice