CASPER I, located at Campus North of KIT, is used as a test facility for superconducting undulator technology. CASPER I is an operating vertical cryostat where coils with maximum dimensions of 35 cm length and 30 cm diameter can be immersed in liquid helium for testing (quench tests and local field measurements).

With CASPER I we can test new winding schemes, new superconducting materials and wires and new field correction techniques. The most relevant tests performed: short mockups in collaboration with industry, superconducting joints and short mockups with switchable period length, short transverse gradient undulator (TGU) for laser wake-field accelerators, and high-temperature superconducting (HTS) tapes for novel undulator concepts, switchable-period-length undulator for ultra-low-emittance light sources and so on.

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.