Paul Andrew Vetter

Measurement of the beta-neutrino correlation of sodium-21 usingshakeoff electrons

The {beta}-{nu} correlation coefficient, a{sub {beta}}{sub {nu}}, is measured in {sup 21}Na by detecting the time of flight of the recoil nucleus detected in coincidence with the atomic electrons shaken off in {beta} decay. The sample of {sup 21}Na is confined in a magneto-optic trap. High detection efficiency allows low trap density, which suppresses the photoassociation of molecular sodium, which can cause a large systematic error. Suppressing the fraction of trapped atoms in the excited state by using a dark trap also reduces the photoassociation process, and data taken with this technique are consistent. The main remaining systematic uncertainties come from the measurement of the position and size of the atom trap and the subtraction of background. We find a{sub {beta}}{sub {nu}}=0.5502(60), in agreement with the Standard Model prediction of a{sub {beta}}{sub {nu}}=0.553(2), and disagreeing with a previous measurement, which was susceptible to an error introduced by the presence of molecular sodium.

Search for oscillation of the electron-capture decay probability of 142Pm

We have searched for time modulation of the electron capture decay probability of 142 Pm in an attempt to confirm a recent claim from a group at the Gesellschaft fur Schwerionenforschung (GSI). We produced 142 Pm via the 124 Sn( 23 Na, 5n) 142 Pm reaction at the Berkeley 88-Inch Cyclotron with a bombardment time short compared to the reported modulation period. Isotope selection by the Berkeley Gas-filled Separator is followed by implantation and a long period of monitoring the 142 Nd Kα x-rays from the daughter. The decay time spectrum of the x-rays is well-described by a simple exponential and the measured half-life of 40.68(53) seconds is consistent with the accepted value. We observed no oscillatory modulation at the proposed frequency at a level 31 times smaller than that reported by Litvinov et al. (Phys. Lett. B 664 (2008) 162). A literature search for previous experiments that might have been sensitive to the reported modulation uncovered another example in 142 Eu electron-capture decay. A reanalysis of the published data shows no oscillatory behavior.

A gas jet target for radioactive ion beam experiments

New radioactive ion beam (RIB) facilities, like FRIB in the US or FAIR in Europe, will push further away from stability and enable the next generation of nuclear physics experiments. Thus, the need for improved RIB targets is more crucial than ever: developments in exotic beams should coincide with developments in targets for use with those beams, in order for nuclear physics to remain on the cutting edge. Of great importance to the future of RIB physics are scattering, transfer and capture reaction measurements of rare, exotic, and unstable nuclei on light targets such as hydrogen and helium. These measurements require targets that are dense, highly localized, and pure, and conventional targets often suffer too many drawbacks to allow for such experimental designs. Targets must also accommodate the use of large area, highly-segmented silicon detector arrays, high-efficiency gamma arrays, and novel heavy ion detectors to efficiently measure the reaction products. To address this issue, the Jet Experiments...

New measurement of the {beta}-{gamma} directional correlation in {sup 22}Na

We have measured the {beta}-{gamma} directional correlation coefficient A{sub 22} in the decay of {sup 22}Na to the 2{sup +} 1275 keV excited state of {sup 22}Ne. We find A{sub 22}=(5.3{plus_minus}2.5){times}10{sup {minus}4}. This measurement has higher precision but disagrees with most previous experiments. The value for A{sub 22}, combined with other experimental inputs, gives recoil-order form factors in disagreement with theoretical estimates. This experiment demonstrates the capabilities of Gammasphere as an instrument for precise {beta}-{gamma} correlation measurements. {copyright} {ital 1999} {ital The American Physical Society}

Design and Construction of a Gas Jet Target for RIB Experiements

PNNL is now part of the JENSA collaboration to produce a gas jet system for the Facility for Rare Isotope Beams (FRIB). This document is a status report for the gas jet working group to be delivered to the FRIB scientific advisory council (SAC). It briefly describes PNNL’s capability at constructing cost efficient and high detection efficiency HPGe arrays.

Half-life of 14O

We have measured the half-life of 14 O, a superallowed (0 + ! 0 + ) � decay isotope. The 14 O was produced by the 12 C( 3 He,n) 14 O reaction using a carbon aerogel target. A low-energy ion beam of 14 O was mass separated and implanted in a thin beryllium foil. The beta particles were counted with plastic scintillator detectors. We find �1/2 = 70.696 ± 0.037 s. This result is 2.0� higher than an average value from six earlier experiments, but agrees more closely with the most recent previous measurment.

Half-life ofO14

We have measured the half-life of 14 O, a superallowed (0 + ! 0 + ) � decay isotope. The 14 O was produced by the 12 C( 3 He,n) 14 O reaction using a carbon aerogel target. A low-energy ion beam of 14 O was mass separated and implanted in a thin beryllium foil. The beta particles were counted with plastic scintillator detectors. We find �1/2 = 70.696 ± 0.037 s. This result is 2.0� higher than an average value from six earlier experiments, but agrees more closely with the most recent previous measurment.

Half-life of 14 O

We have measured the half-life of 14 O, a superallowed (0 + ! 0 + ) � decay isotope. The 14 O was produced by the 12 C( 3 He,n) 14 O reaction using a carbon aerogel target. A low-energy ion beam of 14 O was mass separated and implanted in a thin beryllium foil. The beta particles were counted with plastic scintillator detectors. We find �1/2 = 70.696 ± 0.037 s. This result is 2.0� higher than an average value from six earlier experiments, but agrees more closely with the most recent previous measurment.

Development of a low-energy oxygen 14 ion beam (abstract)

At the 88 Inch Cyclotron at the Lawrence Berkeley National Laboratory (LBNL) we have developed an intense (3×107 pps), low-energy 14O ion beam for precision tests of the standard model. The 70 s half-life of 14O requires on-line production of the isotope. 14O is produced in the form of 12C14O in a high-temperature carbon aerogel target using a 20 MeV 3He beam from the LBNL 88 Inch Cyclotron via the reaction 12C(3He,n)14O. In order to minimize the background radiation for the experiments, the 14O atoms must be separated from the other radioactive isotopes produced in the carbon target. For this purpose, we have developed an experimental setup including the target, transfer line, the electron cyclotron resonance ion source IRIS, and a low-energy ion beam transport line. The major components of the setup are described. The release and transport efficiency for the CO molecules from the target through the transfer line was measured for various target temperatures. The on-line and off-line ion source efficienci...

A lifetime measurement of 14O

At the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory we have developed an intense low energy 14O ion beam. During the last development run, an average beam intensity of 2×107 particles per second (pps) was achieved with a peak intensity of 3×107 pps. The 14O will be used to measure the shape of the beta decay spectrum of the Garnow-Teller branch as a test of the Conserved Vector Current Hypothesis. The half-life will also be measured and used to determine the Vud element of the Cabibbo-Kobayashi-Maskawa mixing matrix.