Undulators

Mechanics overview
Mechanics overview

Undulator Developments

The present undulator developments focus on two large projects at DESY, the PETRA III upgrade towards a 3rd generation light source and the European XFEL project:

  • 14 undulators will be installed in PETRA III with a length of 2m, 5m, or 20m in one case. Besides planar IDs, also one APPLE2 and an In-Vacuum undulator are designated.
  • The XFEL project, which is presently in an extended R&D phase, will have 5 undulator systems consisting of 107 undulator segments with a length of 652m in total.

An extensive common development has been started previously for the planar undulators. The properties of these new insertion devices have to comply with the specifications of both projects, the XFEL setting more stringent requirements. Aside from minor differences in the specification of magnetic field properties, the undulator requirements in both projects have a lot in common. The time schedules of both projects suggest that the construction effort for PETRA III and XFEL prototyping can be combined.

The figure illustrates several characteristic features of the new mechanical support unit (upper left), which can have a variable length between 2 and 5m. A large girder cross section of 500 by 100mm is used to minimize shear deformation. Stainless steel will be used for the girders and support structures to cope with the deformation requirements of ~1μm for the XFEL case.
The girders are connected to massive guideways and lead screws integrated in the support columns using spherical supports. In this way the magnetic forces are transmitted, and a rotational degree of freedom is provided. The exact parallel alignment of top and bottom girder is achieved through a separate guiding system (right).
This system also integrates the linear encoders needed for the feedback of the motors. There are four motors, one for each spindle, which are electronically synchronized. An industrial control system will be implemented. It is based on bus terminals on a rail mount using an EtherCat fieldbus to drive the servo motor controllers and auxiliary hardware.
The mechanical design of the magnetic structure (lower left) is an advancement of the well proven concept used for the FLASH undulators at DESY. 90 cm long support segments for magnets and poles are clamped onto the girders. As previously, fine-tuning of the magnetic field will be made by individual pole height adjustment. This requires each pole to be height-adjustable by about ±100 μm.

Other Current Developments

- New measurement facility (Hall probe bench in 0.1K-stabilized hutch)
- Calibration stand for 3-dimensional Hall probes
- Phase shifter for the XFEL undulator intersection
- Permanent magnet quadrupoles for the XFEL undulator intersection

Operating Insertion Devices

Insertion Devices are installed in the different user facilities at HASYLAB, namely 9 undulators and wigglers at DORIS III, a hard X-ray undulator at PETRA II, as well as 6 undulators in the FLASH tunnel. For the seeding option to be installed at FLASH, 3 further undulator segments have been completed.