T. Haseyama

Manipulating ionization path in a Stark map: Stringent schemes for the selective field ionization in highly excited Rb Rydberg

We have developed a quite stringent method in selectivity to ionize the low angular-momentum (l) states which lie below and above the adjacent manifold in highly excited Rb Rydberg atoms. The method fully exploits the pulsed field-ionization characteristics of the manifold states in high slew-rate regime: Specifically the low l state below (above) the adjacent manifold is firstly transferred to the lowest (highest) state in the manifold via the adiabatic transition at the first avoided crossing in low slew-rate regime, and then the atoms are driven to a high electric field for ionization in high slew-rate regime. These extreme states of the manifold are ionized at quite different fields due to the tunneling process, resulting in thus the stringent selectivity. Two manipulation schemes to realize this method actually are demonstrated here experimentally.

A measurement of the absolute neutron beam polarization produced by an optically pumped 3He neutron spin filter

Abstract The capability of performing accurate absolute measurements of neutron beam polarization opens a number of exciting opportunities in fundamental neutron physics and in neutron scattering. At the LANSCE pulsed neutron source we have measured the neutron beam polarization with an absolute accuracy of 0.3% in the neutron energy range from 40 meV to 10 eV using an optically pumped polarized 3 He spin filter and a relative transmission measurement technique. 3 He was polarized using the Rb spin-exchange method. We describe the measurement technique, present our results, and discuss some of the systematic effects associated with the method.

Field-ionization electron detector at low temperature of 10 mK range

Selective field-ionization electron detector at low temperature of 10 mK range was developed with a channel electron multiplier. The field-ionization electrode system is attached to the bottom plate of the mixing chamber of a dilution refrigerator and ionized electrons are transported to a channel electron multiplier at the 1 K temperature pumping stage through a series of ring focusing electrodes. The channel electron multiplier is heated up to more than 20 K with a heating coil to maintain its long-term operational conditions, while keeping its environment temperature to 1 K. Rydberg states in Rb with 80≲n≲150 were successfully field ionized and detected with this system at the long-term operating temperature of 12–15 mK.

Apparatus for parity-violation study via capture γ-ray measurements

Abstract The Time Reversal and Parity at Low Energy (TRIPLE) Collaboration uses a short-pulsed longitudinally polarized epithermal neutron beam at the Los Alamos Neutron Science Center to study spatial parity violation (PV) in the compound nucleus. The typical PV experiment measures the longitudinal cross-section asymmetry by the neutron transmission method through thick samples. Neutron capture γ-ray measurement provides an alternative method for the study of PV, which enables the use of smaller amounts of isotopically pure target material. In 1995 TRIPLE commissioned a new neutron-capture detector consisting of 24 pure CsI scintillators arranged in a cylindrical geometry around the neutron beam. The characteristics and the performance of the detector and spin transport are described.

Erratum to: “Manipulating ionization path in a Stark map: Stringent schemes for the selective field ionization in highly excited Rb Rydberg atoms”: [Phys. Lett. A 303 (2002) 285]

We have developed a quite stringent method in selectivity to ionize the low angularmomentum (`) states which lie below and above the adjacent manifold in highly excited Rb Rydberg atoms. The method fully exploits the pulsed field-ionization characteristics of the manifold states in high slew-rate regime: Specifically the low ` state below (above) the adjacent manifold is firstly transferred to the lowest (highest) state in the manifold via the adiabatic transition at the first avoided crossing in low slew-rate regime, and then the atoms are driven to a high electric field for ionization in high slew-rate regime. These extreme states of the manifold are ionized at quite different fields due to the tunneling process, resulting in thus the stringent selectivity. Two manipulation schemes to realize this method actually are demonstrated here experimentally.

Parity nonconservation in neutron resonances

The TRIPLE Collaboration has performed measurements of the helicity dependence of the neutron resonance cross section for many nuclides. More than 70 statistically significant parity violations have been observed. Generic enhancements amplify the signal for symmetry breaking and the stochastic properties of the compound nucleus permit the strength of the symmetry-breaking interaction to be determined without knowledge of the wave functions of individual states. The measurements are concentrated in the regions of the 3p and 4p maxima of the neutron strength function-near A=110 and A=230. The results to date are summarized.