TELBE is the first operational super-radiant quasi-cw SRF accelerator-based user facility for selective THz control experiments. Ultrafast dynamics, selectively driven by tunable narrow-band THz pulses, can be studied at unprecedented repetition rates. Research opportunities of this new type of photon facility are discussed based on early-stage experiments at TELBE.
This talk advertises scattering-type scanning near-field infrared micro-spectroscopy (s-SNIM) in the spectral range of 75 to 1.3 THz , as provided by the free-electron laser FELBE, the narrow-band laser-light source at Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Germany. We demonstrate the -independent s-SNIM resolution of a few 10 nm by exploring structured Au samples, Graphene-transistors, meta-materials , and local ferroelectric phase-transitions down to LHe . s-SNIM secondly was integrated into a THz pump-probe experiment for the inspection of excited states in structured SiGe samples. We developed a novel demodulation technique with high temporal resolution  hence achieving an excellent Signal-to-Noise Ratio. Thirdly using the super-radiant TELBE light source , HZDR recently extended the wavelength range down to 100 GHz radiation. We adapted our s-SNIM to this TELBE photon-source as well, achieving an equally high spatial resolution as with FELBE. Moreover, the superb 30-fs temporal resolution of TELBE will allow us to study a multitude of physical phenomena with sub-cycle resolution [5,6], such as spin-structures, magnons and phonon polaritons.
 F. Kuschewski et al., Appl. Phys. Lett. 108 (2016) 113102.
 S.C. Kehr et al., ACS Photonics 3 (2016) 20.
 J. Döring et al., Appl. Phys. Lett. 105 (2014) 053109.
 F. Kuschewski et al., Sci. Rep. 5 (2015) 12582.
 B. Green et al., Sci. Rep. 6 (2016) 22256.
 S. Kovalev et al., Struct. Dyn. 4 (2017) 024301.
An overview is given about the state-of-the-art of superradiant THz sources with a particular emphasize on very recent developments towards compact facilities based on super-conducting RF accelerator technology which enable quasi-cw operation at high repetition rates.