TRIUMF's Electromagnetic Mass Analyzer (EMMA) is a recoil mass spectrometer undergoing commissioning in the ISAC-II experimental hall (see Figure 2). In December 2016 it achieved a major breakthrough when it was tested for the first time with a heavy ion beam. A thick gold foil was bombarded with an 80 MeV 36Ar (argon) beam and elastically scattered 36Ar ions were transmitted through the spectrometer to the focal plane. Ions were dispersed according to their mass/charge ratios and 36Ar ions in the 13+ and 14+ charge states were detected (See Figure 1) in a position-sensitive parallel grid avalanche counter before stopping in a silicon detector. The measured mass/charge dispersion and resolving power were found to agree precisely with ion optical calculations.
Subsequently, the spectrometer was set for 197Au (gold) in the 9+ charge state and a single peak was observed in the focal plane with no background after an hour long measurement with a billion Ar ions per second incident on the target. This performance demonstrated a hardware beam suppression factor of at least 1012 for this reaction.
Following this encouraging initial test, the intention is to complete commissioning EMMA in 2017 and to perform the first radioactive beam experiments in 2018.
Congratulations to Barry Davids and the rest of the EMMA team!
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Figure 1: Focal plane mass/charge spectrum obtained during EMMA's first test in December 2016. 36Ar ions multiply scattered by a thick gold foil were dispersed according to their mass/charge ratios and detected in a position-sensitive parallel grid avalanche counter, resulting in the spectrum shown here.
Figure 2: The TRIUMF's Electromagnetic Mass Analyzer (EMMA) in the ISAC-II experimental hall during assembly.