Brian Fujikawa

Performance of the prototype LANL solid deuterium ultra-cold neutron source

A prototype of a solid deuterium (SD 2 ) source of Ultra-Cold Neutrons (UCN) is currently being tested at LANSCE. The source is contained within an assembly consisting of a 4 K polyethylene moderator surrounded by a 77 K beryllium #ux trap in which is embedded a spallation target. Time-of-#ight measurements have been made of the cold neutron spectrum emerging directly from the #ux trap assembly. A comparison is presented of these measurements with results of Monte Carlo (LAHET/MCNP) calculations of the cold neutron #uxes produced in the prototype assembly by a beam of 800 MeV protons incident on the tungsten target. A UCN detector was coupled to the assembly through a guide system with a critical velocity of 8 m/s (58Ni). The rates and time-of-#ight data from this detector are compared with calculated values. Measurements of UCN production as a function of SD 2 volume (thickness) are compared with predicted values. The dependence of UCN production on SD 2 temperature and proton beam intensity are also presented. ( 2000 Elsevier Science B.V. All rights reserved.

A Geoneutrino Experiment at Homestake

A significant fraction of the 44TW of heat dissipation from the Earth’s interior is believed to originate from the decays of terrestrial uranium and thorium. The only estimates of this radiogenic heat, which is the driving force for mantle convection, come from Earth models based on meteorites, and have large systematic errors. The detection of electron antineutrinos produced by these uranium and thorium decays would allow a more direct measure of the total uranium and thorium content, and hence radiogenic heat production in the Earth. We discuss the prospect of building an electron antineutrino detector approximately 700xa0m3 in size in the Homestake mine at the 4850’ level. This would allow us to make a measurement of the total uranium and thorium content with a statistical error less than the systematic error from our current knowledge of neutrino oscillation parameters. It would also allow us to test the hypothesis of a naturally occurring nuclear reactor at the center of the Earth.

A New Measurement of the Strength of the Superallowed Fermi Branch in the Beta Decay of {sup 10}C with GAMMASPHERE

Abstract We report a new measurement of the strength of the superallowed 0 + →0 + transition in the β -decay of 10 C. The experiment was done at the LBNL 88-inch cyclotron using forty-seven GAMMASPHERE germanium detectors. The technique used in this measurement was similar to that of an earlier experiment, but the systematic corrections were significantly different. The measured branching ratio: 1.4665±0.0038×10 −2 is used to compute the superallowed Fermi f t, which gives the weak vector coupling constant and the u to d element of the Cabibbo–Kobayashi–Maskawa quark mixing matrix.

Time Reversal in Polarized Neutron Decay - The emiT Experiment

The standard electro-weak model predicts negligible violation of time-reversal invariance in light quark processes. We report on an experimental test of time-reversal invariance in the beta decay of polarized neutrons as a search for physics beyond the standard model. The emiT collaboration has measured the time-reversal-violating triple-correlation in neutron beta decay between the neutron spin, electron momentum, and neutrino momentum often referred to as the D coe

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

cient. The rst run of the experiment produced 14 million events which are currently being analyzed. However, a second run with improved detectors should provide greater statistical precision and reduced systematic uncertainties. ( 2000 Elsevier Science B.V. All rights reserved.

Half-life of 14O

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}

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

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.

A lifetime measurement of 14O

At the 88 Inch Cyclotron at the Lawrence Berkeley National Laboratory (LBNL) we have developed an intense (3×107u200apps), 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...

Recoil ion charge state distribution following the beta(sup +) decay of {sup 21}Na

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 3×107u2009pps. 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.