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Insertion Devices

The Insertion Device Group develops insertion devices for use at accelerator and synchrotron facilities. The group pioneered the development of superconductive undulators and was the first worldwide to test them with beam.

Since 2007 the insertion device group activities are focused on the development of superconducting planar insertion devices in collaboration with the industrial partner Babcock Noell GmbH . The group efforts concentrate as well in developing instruments and tools for quality assessment of the magnetic field of superconducting undulators and for understanding the beam heat load mechanisms in a cold bore. In order to fulfill this last task the group is leading a large collaboration, with Babcock Noell GmbH , CERN, Diamond Light Source, Frascati National Laboratory, Rome University “La Sapienza,” STFC Daresbury Laboratory, STFC Rutherford Appleton Laboratory, University of Manchester, Cockcroft Institute of Science and Technology, and Lund University MAX-Lab all participating for the project COLDDIAG, a cold vacuum chamber for diagnostics. The group is also responsible of integrating the new superconducting insertion devices in the storage ring and synchrotron at Karlsruhe Institute of Technology (KIT).

Within KIT close collaborations are ongoing with the Institute for Technical Physics on applications of new superconducting materials to insertion devices.

SCU Insertion Device ANKA
Motivation R&D of superconducting insertion devices
In order to produce synchrotron radiation of 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 of the storage ring. Following an initial proposal at SPRING8 [1], the concept of cryogenic permanent magnet undulators (CPMU) is presently considered as a possible future evolution of in-vacuum undulators (IVU) [2-5]. Superconducting undulators can reach, for the same gap and period length, higher fields even with respect to CPMU devices, allowing to increase the spectral range and the brilliance.

Below is shown the comparison of the performance of a SCU, a CPMU [5] and an IVU considering the same magnetic length and the same vacuum gap. A given photon energy can be reached by the SCU with lower order harmonic: 20 keV can be reached with the 5th harmonic of the SCU, with the 7th harmonic of the CPMU and with the 9th harmonic of the IVU. Therefore, it is possible with a SCU to relax the beam properties and/or the magnetic field quality.
Insertion Devices ANKA Insertion Devices ANKA

Insertion Devices ANKA

References
[1] T. Hara, T. Tanaka, H. Kitamura, T. Bizen, X. Marchal, T. Seike, T. Kohda, and Y. Matsuura, Phys. Rev. ST Accel. Beams 7, 050702 (2004).
[2] C. Kitegi, J. Chavanne, D. Cognie, P. Elleaume, F. Revol,C. Penel, B. Plan, and M. Rossat, in Proceedings of the10th European Particle Accelerator Conference, Edinburgh, Scotland, 2006 (EPS-AG, Edinburgh, Scotland, 2006).
[3] T. Tanabe, D. A. Harder, G. Rakowsky, T. Shaftan, and J. Skaritka, in Proceedings of the 2007 Particle Accelerator Conference, Albuquerque, New Mexico (IEEE, Albuquerque, New Mexico, 2007).
[4] C. Benabderrahmane, N. Bchu, P. Berteaud, M. E. Couprie, J. M. Filhol, C. Herbeaux, C. Kitegi, J. L. Marlats, K. Tavakoli, and A. Mary, in Proceedings of the 11th European Particle Accelerator Conference, Genoa, 2008 (EPS-AG, Genoa, Italy, 2008).
[5] J. Chavanne, M. Hahn, R. Kersevan, C. Kitegi, C. Penel, and F. Revol, in Proceedings of the 11th European Particle Accelerator Conference, Genoa, 2008 (EPS-AG, Genoa, Italy, 2008).

Activities

SCU15 - SCUW - CASPER I - CASPER II - COLDDIAG - New Materials

SCU15
A 1.5 m long superconducting undulator  with a period length of 15 mm has been successfully developed, installed, and tested in collaboration with the company Babcock Noell GmbH 

Thanks to high-precision components, SCU15 fulfills stringent demands on the accuracy of the magnetic field. This makes SCU15 the first full-length superconducting device to reach higher peak magnetic fields than comparable cryogenic permanent magnet undulators.
SCU15 ANKA
SCUW

Aim of the collaboration with the company Babcock Noell GmbH is also to develop superconducting undulators with switchable period length.

The tunability of an insertion device can be increased by period length switching, which in superconducting IDs can be achieved by reversing the current in a separately powered subset of the superconducting windings.


A superconducting undulator-wiggler, which allows to switch between undulator and wiggler mode, will be built to be tested at the IMAGE beamline.

SCUW
We have demonstrated the feasibility of period length switching using a 9 pole mock-up designed and manufactured by Babcock Noell GmbH and showed that there is no need to retrain the magnet after each switch.

CASPER I

is an operating vertical cryostat where mock up coils with maximum dimensions of 35 cm length and 30 cm diameter can be tested in liquid helium.

The magnetic field along the beam axis is measured by Hall probes fixed to a sledge moved by a linear stage with the following precision ∆B/B=0.015% and ∆z/z<10-5.

With CASPER I we can test new winding schemes, new superconducting materials and wires and new field correction techniques.

Casper1
CASPER II

CASPER II is a horizontal, cryogen-free test stand that will be used to perform quality certification (max. length 1500 mm, max. diameter 500 mm) of new superconducting IDs [18]. It will also serve to test small prototype coils in a cryogen-free environment. CASPER II is under construction.

The magnetic field along the beam axis will be measured by Hall probes fixed to a sledge moved by a linear stage. The precisions are ΔB<1 mT and Δz<1 μm. Field integral measurements will be performed using the stretched wire technique.

In order to allow local and integral field measurements in the same thermal cycle, the wire will be stored in the guiding rails of the Hall probe sledge when the Hall probe is in use. When the Hall probe is fully retracted and clear of the gap, the stretched wire can be pulled out.

CASPER2

CASPER2 Daigram

COLDDIAG

With the aim of measuring the beam heat load on a cold bore and in order to gain a deeper understanding in the beam heat load mechanisms, a cold vacuum chamber for diagnostics (COLDDIAG) is under construction.

COLDDIAG consists of a cold vacuum chamber located between two warm sections. This will allow observation of the influence of synchrotron radiation on the beam heat load and a direct comparison between the cryogenic and room temperature regions, with and without a cryosorbed gas layer, respectively.

The inner vacuum chamber will be removable in order to test different geometries and materials. COLDDIAG is built to fit in a short straight section at ANKA, but we are proposing its installation in different synchrotron light sources with different energies and beam characteristics.

The vacuum chamber is being designed and fabricated in collaboration with Babcock Noell GmbH.

COLDIAG
COLDIAG sheme
New materials
The working horse for superconducting magnets are multifilament NbTi wires, which are nowadays also used for superconducting insertion devices. We investigate the possible application of conductors with enhanced critical current density, as the NbTi wire with artificial pinning centres, developed by SupraMagnetics, Inc.

Another alternative to NbTi under study are high temperature superconducting tapes (HTS). The engineering current density of commercial HTS materials is rapidly increasing in performance making them more and more attractive. In addition HTS tapes can be operated at higher temperatures than NbTi allowing to sustain higher beam heat loads, and therefore simplifying the cryostat design for the final device.

NbTi artificial pinning center wire

 

HTS solenoids and undulator mockup

NbTi artificial pinning center wire from Supramagnetics, Inc.
Optical image at microscope
Courtesy: Th. Schneider and M. Kläser (ITeP, KIT)
  Tests at CASPER I of HTS solenoids and undulator mockup from Babcock Noell GmbH.