D. Saez de Jauregui

The New Conduction-Cooled Superconducting Undulator for ANKA

Babcock Noell GmbH (BNG) is completing the fabrication of a 1.5 m long superconducting insertion device for the Karlsruhe Institute of Technology (KIT). The unit is planned to be installed in the ANKA storage ring at the end of 2010 to become the light source of the new beamline NANO for high resolution X-ray diffraction. The period length of the device is 15 mm for a total of 100.5 full periods plus an additional matching period at each end. The key specifications of the system are: a K value higher than 2 for a magnetic gap of 5 mm, the capability of withstanding a 4 W beam heat load and a phase error smaller than 3.5 degrees. The superconducting coils have been qualified by means of a vertical test in liquid helium at CERN and are ready to be installed in the cryostat. This paper describes the main features of the system.

Development of Superconducting Undulators at ANKA

In order to produce synchrotron radiation of the highest brilliance, third generation synchrotron sources make use of insertion devices (IDs). The state of the art available today for IDs is the permanent magnet technology with magnet blocks placed inside the vacuum (IVU) of the storage ring. Following an initial proposal at SPring-8 [1], the concept of Cryogenic Permanent Magnet Undulators (CPMU) is presently considered as a possible future evolution of in-vacuum undulators [2–5]. Superconducting undulators (SCUs) can reach, for the same gap and period length, even higher fields than CPMU devices, allowing increases in the spectral range and the brilliance. At ANKA we are running a research and development program to develop superconducting IDs. The proof of principle of SCU technology application in a storage ring has been demonstrated at ANKA with a device developed together with the company ACCEL Instr. GmbH and installed in the ANKA storage ring since March 2005 [6].

First Experimental Demonstration of Period Length Switching for Superconducting Insertion Devices

Superconducting insertion devices (IDs) are very attractive for synchrotron light sources since they offer the possibility to enhance the tuning range and functionality significantly by period length switching. Period length switching can be achieved by employing two or more individually powerable subsets of superconducting coils and reverse the current in a part of the windings. In this contribution we report the first experimental test of this principle demonstrated on a 70 mm NbTi mock-up coil with period tripling, allowing to switch between a 15 mm period length undulator and a 45 mm wiggler (SCUW 15/45).

Magnetic resonance of the new neutral Al cluster radical [Al7R6]

Static magnetometry and continuous-wave and pulsed-electron spin resonance (ESR) is used for the characterization of the neutral radical cluster [Al(Al3R3)2]• (R=N(SiMe2Ph)2). For temperatures below 25 K, we prove its monoradical character, a g-factor of 1.997–1.991, and a three time larger hyperfine interaction with the central than with the six outer 27Al nuclei of the [Al7R6]• cluster radical. Temperature dependence of the low-temperature spin-lattice relaxation is analysed. At temperatures above 30 K, the effective moment per cluster increases, and the hyperfine interaction with the seven 27Al nuclei is equalized.

Overview of the superconducting undulator development program at ANKA

Superconducting undulators (SCUs) have the potential to reach higher brilliance and flux with respect to the state of the art permanent magnet insertion devices. ANKA is collaborating with the industrial partner Babcock Noell GmbH (BNG) to realize NbTi conduction cooled planar devices for low emittance light sources, and is developing the instrumentation to characterize the magnetic field properties and to measure the beam heat load to a cold bore needed for the cryogenic design of SCUs. We present here: the most recent results obtained within the ANKA-BNG collaboration, the progress achieved in the development of the instrumentation, and the in house studies on the application of high temperature superconducting (HTS) tape to the SCU technology.

Magnetic Performance of a Laser Structured YBCO Tape Suitable for Insertion Devices Technology

Recent intensive development of high-temperature superconducting (HTS) materials resulted in the availability of various commercial HTS tapes, in particular coated conductors. Technological progress in this field and up-coming market will reduce the costs of the tape. One very promising application for free electron laser technology considers a new concept of meander-like structured stacked HTS tapes to provide the desired magnetic field pattern with periodic changing field orientation. For the first time, we report in this paper on the magnetic field performance of such an HTS tape, structured with picosecond laser pulses, which prevent damage of the superconducting layer by overheating and lead to very precise structure.

Field quality of 1.5 m long conduction cooled superconducting undulator coils with 20 mm period length

The Institute for Beam Physics and Technology (IBPT) at the Karlsruhe Institute of Technology (KIT) and the industrial partner Babcock Noell GmbH (BNG) are collaborating since 2007 on the development of superconducting undulators both for ANKA and low emittance light sources. The first full length device with 15 mm period length has been successfully tested in the ANKA storage ring for one year. The next superconducting undulator has 20 mm period length (SCU20) and is also planned to be installed in the accelerator test facility and synchrotron light source ANKA. The SCU20 1.5 m long coils have been characterized in a conduction cooled horizontal test facility developed at KIT IBPT. Here we present the local magnetic field and field integral measurements, as well as their analysis including the expected photon spectrum.

Characterization of 30-cm-Long Superconducting Undulator Coils With the Magnetic Measurement System CASPER II

The performance of superconducting insertion devices (IDs) in an electron storage ring strongly depends on their magnetic field quality. Therefore, it is essential to characterize the local field distribution and field integrals of the superconducting coils before installation in the final ID cryostat. The synchrotron radiation facility ANKA of the Karlsruhe Institute of Technology and Babcock Noell GmbH are collaborating on an R&D program on superconducting undulators (SCUs), which foresees the design, manufacturing, and characterization of an SCU with a 20-mm-period length (SCU20). Following this program, a magnetic measurement setup for conduction-cooled superconducting coils up to 2-m length (CASPER II) was built and commissioned. The system allows for performing training to maximum coil currents, measurements of the local field quality, and the first and second field integrals as well. In this contribution, we describe the measurement setup and, shortly, the magnet design and focus on the tests and measurement results of a 30-cm-long SCU20 coil package to highlight the potentiality of the test facility.

Cryogen—Free Setup for Local and Integral Magnetic Field Measurements of Superconducting Undulator Coils

Since in an undulator the photons add up coherently over the whole undulator length even small magnetic field errors can disturb the superposition of photons and reduce the intensity of the generated photon beam. Therefore, as in any other undulator, the magnetic field has to be measured with high accuracy. Precise measurements of the magnetic properties of conventional, i.e., permanent magnet based insertion devices (IDs) has undergone huge improvements over the past years and initiated a new era in synchrotron light sources worldwide. A similar breakthrough is now necessary in the field of superconducting insertion devices. Therefore, a part of our R&D program for superconducting insertion devices is to perform quality assessment of their magnetic field properties. In this contribution we describe the equipment to perform magnetic measurements of the local field and of the field integrals of superconducting undulator coils up to 2 m length in a cold in vacuum (cryogen free) environment with a focus on the results of the factory acceptance test.

A New Superconducting Undulator for the ANKA Synchrotron Light Source

Superconducting insertion devices (IDs) are very attractive for synchrotron light sources since they allow increasing the flux and/or the photon energy with respect to permanent magnet IDs. Babcock Noell GmbH (BNG) is completing the fabrication of a 1.5 m long unit for ANKA at the Research Center in Karlsruhe (FZK). The period length of the device is 15 mm for a total of 100.5 full periods plus an additional matching period at each end. The key specifications of the system are: a K-value higher than 2, the capability of withstanding a 4 W beam heat load and a phase error smaller than 3.5 degrees. The magnet is in the final stages of the winding process and will be soon tested at CERN in liquid helium in vertical configuration. This paper describes the main features of the system, the results of the prototyping phase and details of manufacturing process.