D. Wollmann

CASPER- A magnetic measurement facility for superconducting undulators

For a given gap and a given period length superconductive cold-bore undulators have a higher field strength compared to permanent magnet undulators. The measurement of the field and the field quality in the cold bore is demanding since the position of the Hall-probes have to be precise within a few microns over a distance of one to two meters. At the Forschungszentrum Karlsruhe two measuring facilities are under construction which allow to measure short mock-ups and undulators with a length of up to two meters. In this paper the two devices called CASPER (ChAracterization Setup for Phase Error Reduction) are described.

Magnetic Field Test Facility for Superconductive Undulator Coils

Superconducting undulators and wigglers are developed for synchrotron light sources, damping rings for linear colliders and polarized positron sources. In an undulator the emitted photons along the trajectory have to interfere. In order to do so the magnetic field in all periods has to be almost identical. The field strength over one or several hundred periods is not allowed to deviate by more than 1%. Translated into mechanical accuracy the position of the wire and the poles has to be more accurate than about 5 over 1 to 2 m. High quality measurement of the field is an essential requirement. In this paper we present two field measuring systems, one is under construction and another one is under design phase at the Forschungszentrum Karlsruhe.

Performance of the First Superconducting Cold-Bore Undulator in an Electron Storage Ring

In March 2005 a superconducting cold-bore undulator was installed in ANKA (ANSTROEM SOURCE IN KARLSRUHE) and since that time has been in operation. The purpose of the installation was to evaluate if such a device can be operated in a heavy duty synchrotron radiation user facility like ANKA without problems. In order to demonstrate this the generated spectra were measured and the heat load induced by the beam was investigated. It was shown that the heat deposited by the beam in the 8 mm gap is less than 1 W per 100 mA at 2.5 GeV and can be cooled by cryocoolers. Finally, reference is made to the spectra produced by sub-picosecond X-rays using a special ANKA optics.

Superconducting In-Vacuum Undulators

During the last years the Research Center Karlsruhe developed novel high-field superconducting in-vacuum undulators with period lengths of 3.8 and 14 mm. The undulators were tested with beam, both in linac type accelerators (Mainzer Microtron MAMI) and storage rings (ANKA). Based on this experience a new generation of superconducting undulators is planned: undulators capable of electrical field error compensation, undulators with electrically variable polarization direction and high brilliance for various accelerators

Measurements of the beam heat load in the cold bore superconductive undulator installed at ANKA

The beam heat load in the cold bore superconductive undulator installed at ANKA has been monitored for almost two years. The possible sources of the observed heat load as synchrotron radiation from upstream magnets, image currents, photo-excited electrons and ions will be discussed and compared with the experimental results.

Measurements of the Beam Induced Heat Load at the ANKA Superconductive Undulator

Several theoretical papers tried to estimate the magnitude of the different possible effects heating a cold‐bore small gap undulator: synchrotron radiation from upstream magnets, image currents and synchrotron radiation produced in the undulator. Measurements performed with the superconducting undulator installed in ANKA show that the dominating heating mechanism is diffuse synchrotron radiation generated in the upstream magnets: about 1 W/ 100 mA stored current at 2.5 GeV at a gap height of 8 mm. This rather low level can presumably be reduced further by modifying the collimating system at the entrance of the undulator.

Technical Report: First Beam Tests of a Superconductive Undulator in a Storage Ring at ANKA

In 2005 a test superconductive undulator was installed in the ANKA storage ring. Since then the undulator has been constantly in operation as the first cold-bore, small-gap superconducting undulator ever installed in a storage ring. The aim of this experiment was to demonstrate that such a device can be operated under normal user conditions. Compared with permanent magnet undulators, superconducting undulators have a higher magnetic field strength (for a given period length and a given gap width) and can be tuned electrically. The higher field strength allows the production of photon beams with higher brilliance and higher photon energy.

Operation of the ANKA Synchrotron Light Source with Superconductive Undulators

Following the successful performance of a beam test with a superconductive undulator at the synchrotron light source ANKA there are plans to equip most of the straight sections with superconductive undulators. In this paper the first results of the measurements are presented and future plans are summarized.

Superconductive damping wigglers for the CLIC project

The CLIC damping ring requires wigglers with both high on-axis fields and short periods. The present design foresees a superconductive wiggler with a period length of 5 cm, a peak on-axis field of 2.5 T and a full aperture of 12 mm. In this paper we explore the performance improvements of the damping ring when these parameters are pushed to 2.7 T at a period length of 2 cm with the expense of a reduced aperture of 5 mm. A design for a prototype for testing the field quality of such a wiggler is presented in this paper and the possibility to test this wiggler with beam in the storage ring ANKA is described.

One Year Operation of a Superconductive Undulator in the Storage Ring ANKA

In spring 2005 the worldwide first cold‐bore superconductive undulator was installed in the storage ring ANKA. In this paper the obtained results concerning the measured spectra and the heat load from the beam are described. Future developments in the field on superconductive undulators at ANKA are summarized.