Status of the Development of a HPGe-BGO Pair Spectrometer for ELI-NP

At the moment, the new european research facility called ELI-NP (The Extreme Light Infrastructure - Nuclear Physics) is being built in Bucharest-Magurele, Romania. ELI-NP offers unprecedented opportunities for photonuclear reactions with high intensity, brilliant and fully polarized photon beams at energies up to 19.5 MeV. The 8 HPGe CLOVER detectors of ELIADE are important instruments for the gamma spectroscopic study of photonuclear reactions. We investigate the possibility to operate an advanced version of an anti-Compton shield (AC shield) as escape γ-rays pair spectrometers for two of the ELIADE CLOVERS to extend the high-resolution spectroscopy to photon energies of several MeV where the pair production process dominates. The BGO shield operated as a stand-alone device can be used as intensity monitor too. The main tasks are to develop and test such an AC shield: a pair spectrometer consisting of BGO and CsI(Tl) crystals with APD (avalanche photodiode) or SiPM (silicon photomultiplier) readout. The results of prototype testing are reported.