M. Sohani

Development of a thermal ionizer as ion catcher

An effective ion catcher is all important part of a radioactive beam Facility that is based on in-flight production. The catcher stops fast radioactive products and emits them as singly charged slow ions. Current ion catchers are based on stopping in He and H-2 gas. However, with increasing intensity of the secondary beam the amount of ion-electron pairs created eventually prevents the electromagnetic extraction of the radioactive ions front the gas cell. In contrast, such limitations are not present in thermal ionizers used with the ISOL production technique. Therefore, at least for alkaline and alkaline earth elements, a thermal ionizer should then be preferred. An important use of the TRI mu P facility will be for precision measurements using atom traps. Atom trapping is particularly possible for alkaline and alkaline earth isotopes. The facility call produce up to 10(9) s(-1) of various Na isotopes with the in-flight method. Therefore, we have built and tested a thermal ionizer. An overview of the operation, design, construction, and commissioning of the thermal ionizer for TRI mu P will be presented along with first results for Na-20 and Na-21. (c) 2008 Elsevier B.V. All rights reserved.

Measurement of the Half-Life of the T=1/2 Mirror Decay of Ne-19 and its Implication on Physics Beyond the Standard Model

The 1+/2 -> 1+/2 superallowed mixed mirror decay of Ne-19 to F-19 is excellently suited for high precision studies of the weak interaction. However, there is some disagreement on the value of the half-life. In a new measurement we have determined this quantity to be T-1/2 = 17.2832 +/- 0.0051((stat)) +/- 0.0066((syst)) s, which differs from the previous world average by 3 standard deviations. The impact of this measurement on limits for physics beyond the standard model such as the presence of tensor currents is discussed.

The beta-gamma decay of Na-21

A new and independent determination of the Gamow-Teller branching ratio in the beta-decay of 21Na is reported. The value obtained of 5.13 +- 0.43 % is in agreement with the currently adopted value and the most recent measurement. In contrast to previous experiments, the present method was based on the counting of the parent 21Na ions and the resulting 351 keV gamma-rays without coincident beta-particle detection.A new and independent determination of the Gamow–Teller branching ratio in the β-decay of 21Na is reported. The value 5.13 ± 0.43% obtained is in agreement with the currently adopted value and the most recent measurement. In contrast to previous experiments, the present method was based on the counting of the parent 21Na ions and the resulting 351 keV γ-rays without coincident β-particle detection.

The β-decay approach for studying 12C

The β-decays of the mirror nuclei 12B and 12N both populate states in 12C and they are therefore a precious source of information about this nucleus. Due to the selection rules of β-decay only 0+, 1+ and 2+ states are populated. This allows a very clean study of unbound states just above the 3α-threshold with those spin and parities. This probe has been applied in two experiments using two complementary experimental techniques: in the first the three α-particles emitted after β-decay are measured in coincidence in separate detectors using the ISOL method, while in the second method 12B and 12N are implanted in a detector and the summed energy of the three α-particles is measured directly. Preliminary results from the two approaches are presented.

STUDIES OF C-12 USING beta-DECAYS

The nuclear structure of states in C-12 have been a subject of interest for both theory and experiment since the early days of nuclear physics. Many open questions remain, especially concerning the existence and properties of 0(+) and 2(+) states in the triple alpha continuum. A series of experiments have been performed using beta-decay of N-12 and B-12 to probe these states. The latest experiment was performed at KVI using an implantation method, measuring the sum energy of the three alpha-particles directly. Preliminary results from this experiment will be presented.