“…[ [26] or 0.6 ppb [25]. Revel et al [28] found this contribution of 28Si (n,pa) 24Na to be less than 0.4 ppb. Haas et al [32] warned against the common use of wrapping the sample for irradiation in A1 foil, as they showed that there is a recoil of 24Na from the A1 wrapping to the sample, due to the high recoil energy from the 27Al (n, a) 24Na reaction, In many other uses it is not important, but due to the very low concentrations of Na in pure Si, this contribution might be a considerable one.…”