Positron-electron pair spectrometry with selective mini-orange devices

Pair spectrometers have been developed with mini-orange filters and adaptedSi(Li) detectors. They have been employed in searches for resonant Bhabha scattering and viable axions. They are of implicit value for studies of pair creation with the high resolution of solid state detectors, with the high acceptance of mini-orange filters and with high specificity for recognition of e +e − 1090 1568 V 3 pairs. The latter is due to the first-order magnetic focusing and can be further enhanced (optional) by observation of annihilation quanta after detection of a position. Special emphasis is devoted to a fourfold arrangement for Bhabha spectrometry, introducing coincident e +e −-pair observations with a central four-segmented Si(Li) counters in sideways positions for detection of correlated positrons.