A new fast time of flight detector for single ion counting to high flux radioactive beams at ISOLDE

Beam diagnostics at the Isotope Separator On-Line DEvice (ISOLDE) consists mainly of wire SCanners and Faraday Cups (FC) coupled to charge sensitive picoammeters. Presented here is the design, simulations, and results of a new FC combined Secondary Electron Emission (SEE) multiplication detector for the beam energies found at ISOLDE (up to 60 keV). It expands the region of sensitivity from the current noise limit (≃0.25 pA) to individual ion counting. The detector is capable of counting rates of 105 ion ms−1 (≃10 pA) for DC or bunched beams with a high sensitivity timing resolution of σt = 0.10 ± 0.03 ns for individual ions. The device also operates as a conventional FC with integrated current measurements on the SEE plate for non-time sensitive operation with efficiency ε = 94% ± 1%. The detector was tested both at the ISOLDE Offline 2 facility and the high resolution separator beam line at the ISOLDE on-line facility where bunched and DC beams from ISCOOL were used.