A hybrid surface arc discharge ion source to produce ultra pure Ca+2 beams for 40Ca(α,γ)44Ti reaction studies at ISAC/TRIUMF

Calcium 40


ISAC is an accelerator facility primarily dedicated to astrophysical studies. Off-line and online ion sources provide up to 65 keV of stable and radioactive beams to the ISAC accelerators. Initial acceleration is done via a constant velocity radio frequency quadrupole that requires 2 keV/u. Then the beam is further accelerated to 1.5 MeV/u at ISAC-I and 6.5 MeV/u at ISAC-II. To study radiative capture reactions relevant for astrophysics, the recoil mass spectrometer DRAGON was built in the experimental area. 40Ca(α,γ)44Ti is identified as one of the key reactions in supernovae to produce 44Ti and is given highest priority. For this experiment, an ultrapure Ca+2 beam was requested from the off-line ion source. Initial tests showed that, when using conventional ion sources, 40Ar and 40K are the impurities that are most difficult to eliminate. In order to overcome this problem, a new concept was needed and the hybrid surface arc discharge ion source was born. The hybrid surface ion source consists of a small surface ionizer and an arc discharge placed in a solenoid field. A very low ratio of 40Ar/40Ca=8 x10−5 was achieved with this new source and the experiment was completed successfully. The source is described in detail and its performance is discussed in this article.

Author: Jayamanna, K.; Vockenhuber, C.
Journal: Review of Scientific Instruments