Brian Tipton

Measurements of ultracold-neutron lifetimes in solid deuterium.

We present the first measurements of the survival time of ultracold neutrons (UCNs) in solid deuterium (SD2). This critical parameter provides a fundamental limitation to the effectiveness of superthermal UCN sources that utilize solid ortho-deuterium as the source material. These measurements are performed utilizing a SD2 source coupled to a spallation source of neutrons, providing a demonstration of UCN production in this geometry and permitting systematic studies of the influence of thermal up-scatter and contamination with para-deuterium on the UCN survival time.

A solenoidal electron spectrometer for a precision measurement of the neutron β-asymmetry with ultracold neutrons

We describe an electron spectrometer designed for a precision measurement of the neutron β-asymmetry with spin-polarized ultracold neutrons. The spectrometer consists of a 1.0-T solenoidal field with two identical multiwire proportional chamber and plastic scintillator electron detector packages situated within 0.6-T field-expansion regions. Select results from performance studies of the spectrometer with calibration sources are reported.

Status of the new Los Alamos UCN source

Ultra-cold neutrons (UCN) have been produced at reactors over the last 30 years. Although very successful, experiments often suffer from low UCN statistics—as limited by the traditional production scheme. A new type of UCN source has been developed at Los Alamos. The source combines a spallation target, a cold neutron flux trap, and a solid deuterium converter for the down-scattering of cold neutrons into the ultra-cold regime. The breakthroughs of the last year include the theoretical understanding of the production mechanism and its experimental verification. The new technique is capable of delivering orders of magnitude higher densities of UCN. The highest UCN density ever stored in an experiment is reported.

Novel technique for ultra-sensitive determination of trace elements in organic scintillators

A technique based on neutron activation has been developed for an extremely high sensitivity analysis of trace elements in organic materials. Organic materials are sealed in plastic or high purity quartz and irradiated at the HFIR and MITR. The most volatile materials such as liquid scintillator (LS) are first preconcentrated by clean vacuum evaporation. Activities of interest are separated from side activities by acid digestion and ion exchange. The technique has been applied to study the liquid scintillator used in the KamLAND neutrino experiment. Detection limits of <2.4×10 15 g 40 K/g LS, <5.5×10 15 g Th/g LS, and <8×10 15 g U/g LS have been achieved.

A proposed measurement of the ß asymmetry in neutron decay with the Los Alamos Ultra-Cold Neutron Source

This article reviews the status of an experiment to study the neutron spin-electron angular correlation with the Los Alamos Ultra-Cold Neutron (UCN) source. The experiment will generate UCNs from a novel solid deuterium, spallation source, and polarize them in a solenoid magnetic field. The experiment spectrometer will consist of a neutron decay region in a solenoid magnetic field combined with several different detector possibilities. An electron beam and a magnetic spectrometer will provide a precise, absolute calibration for these detectors. An A-correlation measurement with a relative precision of 0.2% is expected by the end of 2002.