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In this article, we present a measurement of flow rate, yield and effusion time of a $^{23}$Ne production and transport system. We used an accelerator-driven Li(d,n) neutron source to produce neutrons up to 20 MeV. The radioactive atoms were produced by a $^{23}$Na(n,p) reaction at a NaCl target. Later, the atoms were diffused out from the NaCl crystals and effused from the production chamber via a 10 m hose to a measurement cell and their decay products were detected using high purity germanium (HPGe) and plastic scintillator detectors. The resulting flow rate was $6.9pm0.5cdot 10^4sfrac{atoms}{sec}$ and the total yield was $3.2pm0.4cdot10^{-9}sfrac{atoms}{deuteron}$. We summarize our methods and estimates of efficiencies, rates of production and effusion.
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We review the current status of the radioisotopes program at the Soreq Applied Research Accelerator Facility (SARAF), where we utilize an electrostatic-ion-beam trap and a magneto-optical trap for studying the nuclear $beta$-decay from trapped radioactive atoms and ions. The differential energy spectra of $beta$s and recoil ions emerging from the decay is sensitive to beyond standard model interactions and is complementary to high energy searches. The completed facility SARAF-II will be one of the worlds most powerful deuteron, proton and fast neutron sources, producing light radioactive isotopes in unprecedented amounts, needed for obtaining enough statistics for a high precision measurement.
The $^{22}$Ne(p,$gamma$)$^{23}$Na reaction is the most uncertain process in the neon-sodium cycle of hydrogen burning. At temperatures relevant for nucleosynthesis in asymptotic giant branch stars and classical novae, its uncertainty is mainly due to a large number of predicted but hitherto unobserved resonances at low energy. Purpose: A new direct study of low energy $^{22}$Ne(p,$gamma$)$^{23}$Na resonances has been performed at the Laboratory for Underground Nuclear Astrophysics (LUNA), in the Gran Sasso National Laboratory, Italy. Method: The proton capture on $^{22}$Ne was investigated in direct kinematics, delivering an intense proton beam to a $^{22}$Ne gas target. $gamma$ rays were detected with two high-purity germanium detectors enclosed in a copper and lead shielding suppressing environmental radioactivity. Results: Three resonances at 156.2 keV ($omegagamma$ = (1.48,$pm$,0.10),$cdot$,10$^{-7}$ eV), 189.5 keV ($omegagamma$ = (1.87,$pm$,0.06),$cdot$,10$^{-6}$ eV) and 259.7 keV ($omegagamma$ = (6.89,$pm$,0.16),$cdot$,10$^{-6}$ eV) proton beam energy, respectively, have been observed for the first time. For the levels at 8943.5, 8975.3, and 9042.4 keV excitation energy corresponding to the new resonances, the $gamma$-decay branching ratios have been precisely measured. Three additional, tentative resonances at 71, 105 and 215 keV proton beam energy, respectively, were not observed here. For the strengths of these resonances, experimental upper limits have been derived that are significantly more stringent than the upper limits reported in the literature. Conclusions: Based on the present experimental data and also previous literature data, an updated thermonuclear reaction rate is provided in tabular and parametric form. The new reaction rate is significantly higher than previous evaluations at temperatures of 0.08-0.3 GK.
In this Letter we report on the first inverse kinematics measurement of key resonances in the ${}^{22}text{Ne}(p,gamma)^{23}text{Na}$ reaction which forms part of the NeNa cycle, and is relevant for ${}^{23}$Na synthesis in asymptotic giant branch (AGB) stars. An anti-correlation in O and Na abundances is seen across all well-studied globular clusters (GC), however, reaction-rate uncertainties limit the precision as to which stellar evolution models can reproduce the observed isotopic abundance patterns. Given the importance of GC observations in testing stellar evolution models and their dependence on NeNa reaction rates, it is critical that the nuclear physics uncertainties on the origin of ${}^{23}$Na be addressed. We present results of direct strengths measurements of four key resonances in ${}^{22}text{Ne}(p,gamma)^{23}text{Na}$ at E$_{{text c.m.}}$ = 149 keV, 181 keV, 248 keV and 458 keV. The strength of the important E$_{{text c.m.}}$ = 458 keV reference resonance has been determined independently of other resonance strengths for the first time with an associated strength of $omegagamma$ = 0.439(22) eV and with higher precision than previously reported. Our result deviates from the two most recently published results obtained from normal kinematics measurements performed by the LENA and LUNA collaborations but is in agreement with earlier measurements. The impact of our rate on the Na-pocket formation in AGB stars and its relation to the O-Na anti-correlation was assessed via network calculations. Further, the effect on isotopic abundances in CO and ONe novae ejecta with respect to pre-solar grains was investigated.
The $^{22}$Ne(p,$gamma$)$^{23}$Na reaction is included in the neon-sodium cycle of hydrogen burning. A number of narrow resonances in the Gamow window dominates the thermonuclear reaction rate. Several resonance strengths are only poorly known. As a result, the $^{22}$Ne(p,$gamma$)$^{23}$Na thermonuclear reaction rate is the most uncertain rate of the cycle. Here, a new experimental study of the strengths of the resonances at 436, 479, 639, 661, and 1279 keV proton beam energy is reported. The data have been obtained using a tantalum target implanted with $^{22}$Ne. The strengths $omegagamma$ of the resonances at 436, 639, and 661 keV have been determined with a relative approach, using the 479 and 1279 keV resonances for normalization. Subsequently, the ratio of resonance strengths of the 479 and 1279 keV resonances was determined, improving the precision of these two standards. The new data are consistent with, but more precise than, the literature with the exception of the resonance at 661 keV, which is found to be less intense by one order of magnitude. In addition, improved branching ratios have been determined for the gamma decay of the resonances at 436, 479, and 639 keV.
Measurements of the beta-neutrino correlation coefficient (a$_{beta u}$) in nuclear beta decay, together with the Fierz interference term (b$_F$), provide a robust test for the existence of exotic interactions beyond the Standard Model of Particle Physics. The extraction of these quantities from the recoil ion spectra in $beta$-decay requires accurate knowledge, decay branching ratios, and high-precision calculations of higher order nuclear effects. Here, we report on a new measurement of the $^{23}$Ne $beta$-decay branching ratio, which allows a reanalysis of existing high-precision measurements. Together with new theoretical calculations of nuclear structure effects, augmented with robust theoretical uncertainty, this measurement improves on the current knowledge of a$_{beta u}$ in $^{23}$Ne by an order of magnitude, and strongly constrains the Fierz term in beta decays, making this one of the first extractions to constrain both terms simultaneously. Together, these results place bounds on the existence of exotic tensor interactions and pave the way for new, even higher precision, experiments.
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