||A low energy photon beam in the energy range between 15 eV and
about 1 keV could be produced at MAMI with a short period
undulator. The feasibility has been demonstrated with a 10 period
prototype hybrid undulator (period length 12 mm, gap size 3 mm,
magnetic field on axis 1 Tesla).
Radiation up to the 7th harmonic
For a 100 period undulator
the spectral brilliance of the
first harmonic at 350 eV would amount to about
2*10^15 / (s mm^2 mrad^2 0.1% BW)
at a beam current of 0.1 mA.
A novel interferometer , consisting of
two undulators and a grating spectrometer, has been developed. It
allows the measurement of the complex index of refraction of thin
self supporting foils in the VUV
and soft X-ray region .