1. Materials in Extreme THz Fields Valery Dolgashev Hermann Duerr Shambhu Ghimire Hirohito Ogasawara Haidan Wen Aaron Lindenberg

2. 1. Short pulse dielectric breakdown in materials – in situ measurements THz pump / THz probe (perfect synchronization) THz pump / optical probe Post-mortem analysis 2. Initiation of chemical reactions on surfaces through low frequency mode resonant Excitation: C,H,O adsorbed on surfaces. Excite oxygen-metal bond for THz driven desorption: Dynamics of thermally-excited reactions (THz frequencies on the order of kT) Break bonds, reform bonds, controlling surface chemistry Electron and positron bunches as a new means of molecular manipulation. Requires GV/m fields 3. Magnetism research. Experiments with samples directly in beam and through extracted THz fields. -time-scales for magnetic switching -Electric field manipulation of magnetic materials -Damage mechanisms, electrical transport under high field conditions. Science:

3. -Electron/positron switching enabling reset of dynamics for averaging mode experiments. -Access dynamics through post-mortem analysis for different bunch time-delays -MOKE for optical measurements… THz emission studies through electro-optical sampling 4. Ferroelectric dynamics: Manipulation of polarization dynamics using intense fields. Optical/THz probing THz emission spectroscopy. Parallel ideas to magnetic samples. 5. Strong field electron dynamics in bulk solids: THz-driven high harmonic generation in solids. Earlier work probing effects at 4 micron wavelengths in wide-band-gap semiconductors. Need fields comparable to the atomic field. Bloch oscillations. Impact ionization. Mapping of field-dependent band structure Simple transmission measurements. Diagnostic: visible spectrometer. Transient absorption measurements…

4. Diagnostics and other comments: Spectrometers Bolometer Phase-locked oscillator (~10 fs) (and associated laser safety procedures) Timing signals THz beam splitters for pump-probe Mass spectrometer Known beam parameters (pulse duration, focus) Adjustment of bunch duration, bunch current at fixed pulse duration. Independently controllable electron and positron bunches with arbitrary separation? What is the jitter between the two beams? Extraction of THz from tunnel? FACET vs. LCLS: positrons. Control of beam parameters. Access. Samples in beam. Insertion of waveguide. X-ray generation? Single-cycle pulse isn’t always optimum: Wave guides as a means of generating longer pulses but narrow band for resonant excitation. Sub-cycle measurements possible so doesn’t compromise time resolution -FLASH method