Speaker
Description
We present the details and status of a new experiment commissioned at Weizmann Institute of Science, Israel for a high precision study of the Weak Interaction via the beta-neutrino correlation in radioactive decay of short lived 6He. The facility consists of a 14 MeV d + t neutron generator to produce atomic 6He via the 9Be(n,alpha)6He reaction. The Be target was in the form of 40 porous BeO discs of 2 mm thickness and 80 mm diameter [1]. After extraction from the target, the 6He atoms are to be ionized and bunched in an electron beam ion source, and subsequently injected into an electrostatic ion beam trap. The ion storage time inside the trap for stable ions was found to be about 1.2 s at the chamber pressure of 7 x 10-10 mbar. This provides sufficient time for the measurement of the angular correlation coefficient of beta decay from trapped 6He ions. electrons are measure in a plastic position sensitive detectors and the recoiling 6Li in an annular position sensitive micro-channel-plate (MCP) detector. The present results yield the production probability of 6He atoms to be 1.5x10-44 per 14 MeV neutron and the transport efficiency to be about 4%, in good agreement to simulations, demonstrating that most of the 6He atoms emerged from the BeO disc assembly in a time considerably shorter than the 0.8 s half-life of 6He. The test results of the facility demonstrate a novel method for production of light radioactive atoms for the precision measurement. This is an important result for the present scale-up of the earlier ISOLDE experiment [1] and bodes well for even larger scale-ups of such production set up.
The entire system is being presently transferred to the newly constructed target room at the SARAF accelerator at the Soreq Research Center, Israel [2]. At the SARAF, an orders-of-magnitude improvement in the 6He yield is expected due to a much higher n flux from the 7Li(d,n)4He reaction on the LiLiT liquid lithium target [3], larger number of BeO discs and improved transportation efficiency.
References
1) T. Stora, E. Noah, R. Hodak, T. Y. Hirsh, M. Hass, V. Kumar,
K. Singh, S. Vaintraub, P. Delahaye, H. Franberg-Delahaye, M.-G. Saint-Laurent, G. Lhersonneau, A high intensity 6He beam for the beta -beam neutrino oscillation facility, EPL (Europhysics
Letters) 98 (3) (2012) 32001.
2) I. Mardor, D. Berkovits, S. Halfon, T. Hirsh, Y. Mishnayot, S. Vaintraub, L. Weissman, M. Hass, I. Mukul, B. Ohayon, M. Paul, G. Ron, M. Tessler, Research programs and plans at the Soreq Applied Research Accelerator Facility - SARAF, Proceedings of Science INPC2016 (2017) 109.
3) S. Halfon et al., High-power liquid-lithium jet target for neutron production, Rev. Sci. Inst. 84, 123507 (2013)
