The implementation and further improvements of superconducting undulators are part of the European XFEL facility development program. Within this program, a magnetic field test facility is being developed. Named SUNDAE2 (Superconducting UNDulAtor Experiment 2), it aims to perform in-vacuum magnetic field measurements of superconducting undulators (SCUs) with three techniques: Hall probe, moving wire, and pulsed wire. This contribution presents the updates and status of SUNDAE2.

Superconducting Undulators (SCUs) can produce higher photon flux and cover a wider photon energy range compared to permanent magnet undulators (PMUs) with the same vacuum gap and period length. To build the know-how to implement superconducting undulators for future upgrades of the European XFEL facility, the test stand SUNDAE1 for the characterization of SCU is being developed. The purpose of SUNDAE1 is the training, tuning and development of new SCU coils by means of precise magnetic field measurements. The experimental setup will allow the characterization of magnets up to 2m in length. These magnets will be immersed in a Helium bath at 4K or 2K temperature. In this article, we describe the experimental setup and highlight its expected performances.

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.

The X-ray free-electron laser European XFEL [1] will generate extremely intense, ultra-short pulses of laser light in the X-ray range and open up highly promising research opportunities for almost all the natural sciences. In the LINAC of the XFEL electrons get accelerated by superconducting cavities. The RF-power required by these cavities is generated at 27 RF-stations. An important part of a RF-station is the HV-pulse modulator, which has to supply 12kV pulses at up to 1.8kA for max. 1.7ms pulse duration and up to 30Hz pulse repetition rate. This pulse is conducted by means of a special HV pulse cable to a pulse transformer, which converts it to typical 120kV/140A. This pulse drives a klystron which feeds the cavities of the LINAC with RF-power. Although experience exists from the test facilities FLASH (DESY, Hamburg site) and PITZ (DESY, Zeuthen site) a dedicated modulator test facility has been constructed for testing and investigating the modulator prototypes in a real setup similar to that of the future RFstation at XFEL. The result of these tests will influence the final design of the XFEL modulators and the process of modulator procurement for XFEL.

The superconducting XFEL machine will be built in a single tunnel. The RF stations provide RF power of up to 10 MW at 1.3 GHz. The modulators will produce high-voltage pulses of up to 120 kV, 140 A with a pulse length of 1.54 ms. These will be installed in a service hall at ground level. The klystrons will be positioned near the cavities inside of the tunnel. The energy will be transported via pulse cables of up to 1.5 km length between the pulse generating units of the modulators located in the halls and the pulse transformers in the tunnel. Since the transformers have a transformer ratio of 1:12, pulses of 10 kV and 1.6 kA must be transmitted. Tests with pulse cables have been made with an existing modulator and klystron of the FLASH-Linac. The results showed that the internal construction of the modulator had to be changed to improve EMI behaviour. In order to prove that the beam in the accelerator is not disturbed by the operation of the cables a set of pulse cables was installed inside the tunnel of the FLASH-Linac in parallel to the beam line. An existing pulse transformer/ klystron unit was supplied via these 1.5 km long cables by a new prototype of a modulator taking into account EMI considerations. The FLASH-Linac has been operated for a longer period of time with this set up proving reliable and stable operation.

The FLASH linac at DESY in Hamburg is a superconducting linear accelerator which provides an electron beam to generate laser light in the nm-regime. Five RF stations provide RF power up to 10 MW to generate and accelerate an electron beam up to lGeV in an RF gun and forty-eight superconducting nine-cell cavities, respectively. Several bouncer type modulators produce HV-pulses up to 130 kV, 140 A at 1.5 ms and up to 10 Hz for the 1.3 GHz klystrons and multi-beam klystrons of the linac. The first modulators have been constructed and delivered several years ago by FNAL to the TESLA Test Facility at DESY, which is now the FLASH linac. Later additional modulators have been assembled at DESY from subsystems, which have been constructed and manufactured by industrial companies. Two additional systems are in operation at PITZ at DESY in Zeuthen. This paper reports on the layout of the modulators, the major changes and improvements and the operation experience.

The European XFEL, an X-ray free electron laser, is planned as an European project with a strong connection to the DESY research center in Hamburg. Construction started in summer 2007 and commissioning will begin at the end of 2013. The LINAC of the XFEL incorporates 27 RF stations, which supply the RF power required by the superconducting cavities. In order to generate the RF pulses (1.3GHz, 10MW) HV pulse modulators are required to operate the klystrons. Each modulator has to supply 12kV pulses at 1.8kA for 1.7ms pulse duration. A 1:12 pulse transformer converts these pulses to a level of 120kV at 140A required at the cathode of the klystrons. Although extensive experience exists from the test facilities FLASH (DESY, Hamburg site) and PITZ (DESY, Zeuthen site) a dedicated modulator test stand has been setup to test and investigate new modulator prototypes developed by different companies. The test stand setup is similar to the setup of the future XFEL RF-stations.

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.

Electronic measurement and control instruments incorporating sophisticated micro and macro electronic components operating in the radiation environment of high-energy particle accelerators are prone to radiation induced malfunctions. Many of such devices are now been installed in the containment tunnel of the high-energy electron linac driving the FLASH (Free Electron Laser at Hamburg) facility at DESY. We have developed an efficient concrete material for constructing highly compact shielding walls to protect the electronic devices from the energetic neutrons. This report highlights the Monte Carlo Simulation technique we have used for the optimised shielding calculations.

To feed the superconducting correction magnets of the HERA proton ring, switched mode power supplies have been developed at DESY (Deutsches Elektronen-Synchrotron). The nominal power is up to 35 kW. The current is in a range from 60 A to 360 A. The choppers work as buck converters, switching a primary voltage with a pulse width modulation (PWM). MOSFET transistors are used as switches. The primary voltage is delivered by six pulse diode rectifiers. One rectifier supplies up to 32 choppers. To achieve bipolar behavior of the unipolar units, mechanical polarity switchers are mounted. Dynamic zero crossing can thus be done with an error less than 800 ppm of the nominal current within 300 ms. Afterwards the error is less than 100 ppm. The load time constants (L/R) are between 0.01 and 9.4 s, with superconducting inductances between 1 mH and 4.5 H

For TESLA a lot of equipment will be installed inside the accelerator tunnel which is not accessible during the four week run periods. During the following maintenance day time consuming trouble shooting is not possible and equipment will be exchanged instead of being repaired in place. Therefore the equipment has to be installed in electronic racks inside a container frame. This container will have a docking system to allow a quick exchange of the whole assembly via a monorail that will be installed inside the tunnel. In the TESLA Test Facility this principle will be investigated. The magnet power supplies will be installed in the tunnel. For this purpose the container frames with the electronic racks and a special docking system for quick exchange have been designed, and prototypes are being developed. The power supplies are modified to fit in the electronic racks.

The HERA machine delivered good results in 1996. This was possible due to a higher availability of the technical subsystems than in the years before. Here the failures of the power supplies during 1996 will be analysed and a statistic of the failures of the accelerators will be shown. This will be compared to the failures of the last few years to see what improvements had the most success. A preview onto the next changes will be given and the introduction of new tools (software and hardware) will be explained

Massimo Altarelli, Reinhard Brinkmann, Majed Chergui, Winfried Decking, Barry Dobson, Stefan Düsterer, Gerhard Grübel, Walter Graeff, Heinz Graafsma, Janos Hajdu, Jonathan Marangos, Joachim Pflüger, Harald Redlin, David Riley, Ian Robinson, Jörg Rossbach, Andreas Schwarz, Kai Tiedtke, Thomas Tschentscher, Ivan Vartaniants, Hubertus Wabnitz, Hans Weise, Riko Wichmann, Karl Witte, Andreas Wolf, Michael Wulff, Mikhail Yurkov