  Next-generation gamma beams beams from laser Compton-backscattering
facilities like ELI-NP (Bucharest)] or MEGa-Ray (Livermore) will drastically
exceed the photon flux presently available at existing facilities, reaching or
even exceeding 10^13 gamma/sec. The beam structure as presently foreseen for
MEGa-Ray and ELI-NP builds upon a structure of macro-pulses (~120 Hz) for the
electron beam, accelerated with X-band technology at 11.5 GHz, resulting in a
micro structure of 87 ps distance between the electron pulses acting as mirrors
for a counterpropagating intense laser. In total each 8.3 ms a gamma pulse
series with a duration of about 100 ns will impinge on the target, resulting in
an instantaneous photon flux of about 10^18 gamma/s, thus introducing major
challenges in view of pile-up. Novel gamma optics will be applied to
monochromatize the gamma beam to ultimately Delta E/E~10^-6. Thus
level-selective spectroscopy of higher multipole excitations will become
accessible with good contrast for the first time. Fast responding gamma
detectors, e.g. based on advanced scintillator technology (e.g. LaBr3(Ce))
allow for measurements with count rates as high as 10^6-10^7 gamma/s without
significant drop of performance. Data handling adapted to the beam conditions
could be performed by fast digitizing electronics, able to sample data traces
during the micro-pulse duration, while the subsequent macro-pulse gap of ca. 8
ms leaves ample time for data readout. A ball of LaBr3 detectors with digital
readout appears to best suited for this novel type of nuclear photonics at
ultra-high counting rates.
