Speaker
Description
The demand for new beams at the ISOLDE facility is constantly growing. For refractory elements such as the actinides, experiments face challenging or unknown yield and beam purity. More beam composition information in the actinide region is needed, and further target and ion source developments may be required. Forming volatile molecules has been explored as an avenue to improving the surface desorption process of refractory elements, potentially allowing them to be extracted and delivered as ion beams [1][2]. Volatilization has been successfully shown for carbon [3] and boron [4]. Molecular extraction additionally shifts the mass of interest, changing the isobaric contamination situation. Here we present preliminary results of beam developments for extraction of actinide elements at ISOLDE from thick uranium carbide (UCx) targets with surface ion sources. Two-step resonant ionization laser schemes were used to study laser-ionized atomic actinide beams of the light actinides Ac, Pa, U, Np, and Pu. Beam composition was studied with the ISOLTRAP Multi-Reflection Time-of-Flight Mass Spectrometer (MR-ToF MS) [5], giving identification by ToF mass measurements. CF4 gas was used as a candidate for molecular sideband extraction of the actinide elements via injection of reactive gases and formation of volatile molecules.
Atomic beams of Ac, U, Np and Pu were identified by laser resonance or ToF. Atomic laser-ionized Pa was not observed, and Th was not attempted. Several surface-ionizable actinide fluoride molecules were stable enough to survive the high-temperature surface ion source and were identified with ToF mass measurements at the ISOLTRAP MR-ToF MS. These studies give information on some actinide molecules with low ionization potentials and identify some of the surface-ionized background and challenges involved for experiments interested in these beams. The results serve to facilitate delivery of actinide and actinide molecular beams at ISOLDE.
References
[1] R. Eder et al. Nucl. Inst. and Meth. B 62.4 (1992), pp. 535–540.
[2] R. Kirchner, Nucl. Inst. and Meth. B 126.1-4 (1997), pp. 135–140.
[3] Hanna Franberg. PhD thesis. Bern U., (2008).
[4] Ballof J, Seiffert Ch. et al., Eur. Phys. J. A 55.5 (2019).
[5] R. N. Wolf et al., Int. J. Mass Spec. 349-350.1 (2013), pp. 123–133.
