A gas cell for stopping, storing and polarizing radioactive particles

Abstract

A radioactive beam of 20Na is stopped in a gas cell filled with Ne gas. The stopped particles are polarized by optical pumping. The degree of polarization that can be achieved is studied. A maximum polarization of 50% was found. The dynamic processes in the cell are described with a phenomenological model.Comment: 16 pages, 6 figure

Test of Lorentz invariance inβdecay of polarizedNa20

“…As we showed in Ref. [14] the polarization of the 20 Na sample can be characterized by a time τ pol ≈ 40 ms for each particle to become polarized after it enters the gas cell and a depolarization time τ depol ≈ 1-4 s. The latter depends on the gas condition and whether the beam was "on" or "off" (cf. Fig.…”

“…Fig. 4 of [14]). Therefore, a Monte Carlo simulation was done to find the effective polarization to be used with Eq.…”

“…The TRIµP dual separator removes the primary beam giving a beam of radioactive 20 Na [13] with 19 Ne as main contaminant. The 20 Na nuclei are stopped in a cell filled with Ne buffer gas, where they can neutralize to atoms [14]. The 19 Ne stops in the gas-cell window.…”

“…A detailed account of depolarization mechanisms is given in Ref. [14]. This reference also discusses why full polarization is not achieved.…”

Test of rotational invariance in β decay

“…The β asymmetry can be well described with a three parameter function. The time dependent polarization results from the dynamics of stopping and neutralization of fast particles in a buffer gas and the chemistry due to contaminants [11]. A time dependent description of the polarization is important to interpret the measured lifetimes in the 2 s periods in terms of the asymmetry defined in (3).…”