The SwissFEL X-ray Free Electron Laser (XFEL) facility started construction at the Paul Scherrer Institute (Villigen, Switzerland) in 2013 and will be ready to accept its first users in 2018 on the Aramis hard X-ray branch. In the following sections we will summarize the various aspects of the project, including the design of the soft and hard X-ray branches of the accelerator, the results of SwissFEL performance simulations, details of the photon beamlines and experimental stations, and our first commissioning results.
The SwissFEL Injector Test Facility operated at the Paul Scherrer Institute between 2010 and 2014, serving as a pilot plant and testbed for the development and realization of SwissFEL, the X-ray Free-Electron Laser facility under construction at the same institute. The test facility consisted of a laser-driven rf electron gun followed by an S-band booster linac, a magnetic bunch compression chicane and a diagnostic section including a transverse deflecting rf cavity. It delivered electron bunches of up to 200 pC charge and up to 250 MeV beam energy at a repetition rate of 10 Hz. The measurements performed at the test facility not only demonstrated the beam parameters required to drive the first stage of an FEL facility, but also led to significant advances in instrumentation technologies, beam characterization methods and the generation, transport and compression of ultra-low-emittance beams. We give a comprehensive overview of the commissioning experience of the principal subsystems and the beam physics measurements performed during the operation of the test facility, including the results of the test of an in-vacuum undulator prototype generating radiation in the vacuum ultraviolet and optical range.
Abstract. In this paper we discuss the problem of synchronization in ZooKeeper, a fault-tolerant distributed coordination framework. One of the key features of ZooKeeper is to move away from blocking API such as locks, in order to avoid problems with slow or faulty clients. Instead, it provides an event like synchronization mechanism, allowing clients to be notified upon state change on the server. However, such a mechanism leads to very inefficient implementation of synchronization objects such as queues or barriers. We propose a new solution to this problem. The solution is to handle a sequence of client operations completely on the server. This means that the client implements the required sequence of operations as a single request, which is sent to the server for execution via a generic API. We present a prototype that shares some of the concepts of ZooKeeper but, contrary to ZooKeeper, allows a very efficient implementation of synchronization objects. The solution requires a deterministic multi-threaded server, which we implement thanks to a coroutine mechanism. Experiments show the significant gain in efficiency of our solution on producer-consumer queues and synchronization barriers.
Developed under the auspices of UNESCO, SESAME (Synchrotron light for Experimental Science and Application in the Middle East) will be a major international research centre in the Middle East / Mediterranean region. Most of the applications require hard x-rays up to 20 keV photons. SESAME will be a 2GeV 3 rd Generation Ligth Source with an emittance of 17 nmrad and 13 places for the installation of insertion devices with a length around 3 meter. The circumference of the machine will be 120m. As injector the 800 MeV Booster Synchrotron will be used with small changes. Furthermore also the BESSY I quadrupoles and sextupoles can be used. In a later stage these new ones will be replaced in order to increase the length of the straight sections and to introduce mini beta sections for the reduction of the beam cross section. At SESAME around 35 % of the circumference can be used for the installation of insertion devices.
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