Design and offline test of dual-MCP time-of-flight detector with forward-backward secondary electron collection for isochronous mass spectrometry at HIAF-SRing

摘要: Isochronous mass spectrometry (IMS) conducted with a heavy-ion storage ring has been proven to be a powerful tool for precision mass measurements of short-lived nuclei in the past decades. However, the achieved mass precision in the IMS experiments strongly depends on the efficiency of the detector. This leads to a poorer mass resolving power for light nuclei with smaller proton numbers. To overcome this limitation, we developed a dual-microchannel plate (MCP) time-of-flight (TOF) detector capable of collecting secondary electrons (SEs) emitted in both forward and backward directions when ions pass through a thin carbon foil. Meanwhile, the time resolution was improved by increasing the electric field strength E, in which the homogeneity was also optimized through varying the potential of equalizing ring. From offline tests with an α-source, a total detection efficiency of 94% and a best time resolution of 29.62 ± 0.80 ps at E = 300 V/mm were achieved. These results show a substantial efficiency gain for light ions and meet the stringent timing performance required for Bρ-defined IMS at HIAF-SRing.