The European XFEL is a hard X-ray free-electron laser (FEL) based on a high-electron-energy superconducting linear accelerator. The superconducting technology allows for the acceleration of many electron bunches within one radio-frequency pulse of the accelerating voltage and, in turn, for the generation of a large number of hard X-ray pulses. We report on the performance of the European XFEL accelerator with up to 5,000 electron bunches per second and demonstrating a full energy of 17.5 GeV. Feedback mechanisms enable stabilization of the electron beam delivery at the FEL undulator in space and time. The measured FEL gain curve at 9.3 keV is in good agreement with predictions for saturated FEL radiation. Hard X-ray lasing was achieved between 7 keV and 14 keV with pulse energies of up to 2.0 mJ. Using the high repetition rate, an FEL beam with 6 W average power was created. The first operation of the European X-ray free-electron laser facility accelerator based on superconducting technology is reported. The maximum electron energy is 17.5 GeV. A laser average power of 6 W is achieved at a photon energy of 9.3 keV.

At the ring cyclotron facility of the Research Center for Nuclear Physics (RCNP) Osaka University, Osaka, Japan a series of measurement campaigns had been continued with quasi mono-energetic neutron beams in November 2014. A 7 Li target was bombarded with 100 and 300 MeV protons and the generated neutron beams were directed into a long time-of-flight tunnel at 0 and 25 degrees deflection angle with respect to the proton beam. At a distance of 41 m the cross section of the neutron beam was large enough for the illumination of square meter sized objects like extended range rem-counters. The research institutes SPring-8/RIKEN, Japan, and DESY, Germany, participated in this campaign for the calibration of 4 different types of active ambient dose rate monitors: LB 6411, LB 6411-Pb, LB 6419 and LB 6420. The measurements of their responses are reported and compared with the calculated values.

Commensuratemagnetoresistance periodic oscillations generated by transversal electron snake orbits are found experimentally. A two-dimensional electron gas is exposed to a magnetic field that changes sign along the current longitudinal direction and is homogeneous in the transverse direction. The change in sign of the magnetic field directs the electron flow along the transversal direction, in snake orbits. This generates resistance oscillations with a predictable periodicity that is commensurate with the width of the electron gas. Numerical simulations are used to reveal the character of the oscillations.

Extreme-ultraviolet to x-ray free-electron lasers (FELs) in operation for scientific applications are up to now single-user facilities. While most FELs generate around 100 photon pulses per second, FLASH at DESY can deliver almost two orders of magnitude more pulses in this time span due to its superconducting accelerator technology. This makes the facility a prime candidate to realize the next step in FELs-dividing the electron pulse trains into several FEL lines and delivering photon pulses to several users at the same time. Hence, FLASH has been extended with a second undulator line and self-amplified spontaneous emission (SASE) is demonstrated in both FELs simultaneously. FLASH can now deliver MHz pulse trains to two user experiments in parallel with individually selected photon beam characteristics. First results of the capabilities of this extension are shown with emphasis on independent variation of wavelength, repetition rate, and photon pulse length.

In accelerator environments there are for radiation protection two major challenges in accurate dose measurement: high energies and pulsed fields. Especially dead time effects cannot be easily overcome without the design of new technology [1]. Therefore BERTHOLD Technologies together with DESY and STRUCK Innovative Systems in Hamburg developed the new area dose meter BERTHOLD LB 6419 for pulsed and continuous neutron and gamma radiation. The concept for pulsed neutron measurement is based on activation of short-lived nuclides in the detector materials or in their surroundings. We use several convenient nuclear reactions with carbon as target material.

In the framework of the EURADOS working group 11, an intercomparison of active neutron survey meters was performed in a pulsed neutron field (PNF). The aim of the exercise was to evaluate the performances of various neutron instruments, including commercially available rem-counters, personal dosemeters and instrument prototypes. The measurements took place at the cyclotron of the Helmholtz-Zentrum Berlin für Materialien und Energie GmbH. The cyclotron is routinely used for proton therapy of ocular tumours, but an experimental area is also available. For the therapy the machine accelerates protons to 68MeV. The interaction of the proton beam with a thick tungsten target produces a neutron field with energy up to about 60MeV. One interesting feature of the cyclotron is that the beam can be delivered in bursts, with the possibility to modify in a simple and flexible way the burst length and the ion current. Through this possibility one can obtain radiation bursts of variable duration and intensity. All instruments were placed in a reference position and irradiated with neutrons delivered in bursts of different intensity. The analysis of the instrument response as a function of the burst charge (the total electric charge of the protons in the burst shot onto the tungsten target) permitted to assess for each device the dose underestimation due to the time structure of the radiation field. The personal neutron dosemeters were exposed on a standard PMMA slab phantom and the response linearity was evaluated.

The extension of the FLASH facility at DESY (Hamburg, Germany) – FLASH II Project – is under way. The extension includes a second undulator line with variable gap undulators to allow a more flexible operation, and a new experimental hall for photon experiments. The present FLASH linac will drive the both undulator beamlines. Civil construction of the new buildings has been started in autumn 2011 continuing in several steps until spring 2013. The design of the new electron beamline including the extraction from the FLASH linac and the undulator section is mostly finished, and the manufacturing of the components is under way. Design of the photon beamline and layout of the experimental hall is in an advanced stage. The beamline mounting starts end of 2012, and the commissioning with beam is scheduled for the second half of 2013.

FLASH has been a user facility since 2005, delivering radiation in the wavelength range between 7 and 47 nm using the SASE principle. After the present upgrade, the wavelength range is extended to 4.45 nm. With the third harmonic accelerating module in place to linearize the longitudinal phase space, the stability and reproducibility of the machine is substantially improved. The user requests for beam time by far exceeds the time available. In order to increase user beam time and to improve the radiation properties delivered to users, a major extension of the user facility called FLASH II has been proposed by DESY in collaboration with the HZB. FLASH II is a seeded FEL in the parameter range of FLASH. As logical continuation, the seeding with HHG which started with sFLASH will result in direct seeding. Because in the foreseeable future there will probably not be HHG seed lasers available at high repetition rates down to wavelengths of 4 nm, a cascaded HGHG scheme is proposed to produce short wavelengths.After a first design report, the project now enters its technical design phase. During this time, the FLASH beam parameters after the present upgrade 2009/2010 will be characterized and the present design will be re-evaluated and adjusted. In addition, start-to-end simulations will complete the simulations which have been performed so far, including a design of the extraction area. (C) 2010 Elsevier B.V. All rights reserved.

Many active radiation detectors exhibit severe limitations in pulsed radiation fields, which cannot be easily overcome without the design of new technology. Therefore a new area dose monitor for the measurement of pulsed and continuous neutron and gamma radiation fields was developed. The measurement of pulsed radiation is based on activation of short-lived nuclides in the detector materials or in the surroundings. The instrument comprises a thermal neutron detector in a moderator for neutron detection and a plastic scintillator for beta and gamma detection. These detectors are measuring direct radiation and also decay particles from the instable activated nuclei. The data are time-resolved acquired by a fast FADC module and the delayed decay products are identified by analyzing their timing characteristics. Measurements with pulsed and with continuous radiation are reported.

Complex radiation fields at workplaces at European high-energy accelerators and fusion facilities

The project status for the reconstruction of the 2304 m long existing storage ring PETRA II into a third generation low emittance synchrotron radiation source is presented. To reach the design emittance of 1 nmrad at an energy of 6 GeV together with a beam current of at least 100 mA and a supply of 14 straight sections for the installation of undulators, several fundamental measures are foreseen. For the emittance of 1 nmrad a FODO lattice in seven arcs together with damping wiggler sections in two long straights are envisaged. One eighth of the ring gets new magnets arranged to DBA cells to provide space and the required optics for the undulators. A complete new separately supported vacuum system reduces drastically movements of beam position monitors and magnetic elements due to synchrotron radiation heat load. This is an important precondition for the orbit stabilization system. To beat multi bunch instabilities in order to get a high beam current a powerful wideband feedback system will be established. The planned topping up mode guarantees stable beam current and therefore stable thermal conditions for the experiments.

The European Commission is funding within its Sixth Framework Programme a three-year project (2005-2007) called CONRAD, COordinated Network for RAdiation Dosimetry. The organisational framework for this project is provided by the European Radiation Dosimetry Group EURADOS. One task within the CONRAD project, Work Package 6 (WP6), was to provide a report outlining research needs and research activities within Europe to develop new and improved methods and techniques for the characterisation of complex radiation fields at workplaces around high-energy accelerators, but also at the next generation of thermonuclear fusion facilities. The paper provides an overview of the report, which will be available as CERN Yellow Report.

An analysis is presented of scaling violations of the proton structure function F 2 (x; Q 2) measured with the H1 detector at HERA in the range of Bjorken x values between x = 310 ?4 and 10 ?2 for four-momentum transfers Q 2 larger than 8.7 GeV 2. The structure function F 2 (x; Q 2) is observed to rise linearly with lnQ 2. Under the assumption that the observed scaling violations at small x 0:01 are described correctly by perturbative QCD, an estimate is obtained of the gluon distribution function G(x; Q 2 o) at Q 2 o = 20 GeV 2 .