arXiv subjects

K. K. H. Leung

Publications and source records attributed to K. K. H. Leung.

21 records · Page 2Linked to original sources

arXiv2014

New source for ultracold neutrons at the Institut Laue-Langevin

A new intense superthermal source for ultracold neutrons (UCN) has been installed at a dedicated beam line at the Institut Laue-Langevin. Incident neutrons with a wavelength of 0.89 nm are converted to UCN in a five liter volume filled with superfluid $^4$He at a temperature of about 0.7 K. The UCN can be extracted to room temperature experiments. We present the cryogenic setup of the source, a characterization of the cold neutron beam, and UCN production measurements, where a UCN density in the production volume of at least 55 per cm$^3$ was determined.

physics.ins-det↗

arXiv2009

A new method of measuring the half-life of ^{10}C

A new measurement of the half-life of the positron emitter 10C has been made. The 10C decay belongs to the set of superallowed 0+ -> 0+ beta-decays whose Ft values offer stringent tests of the Conserved Vector Current (CVC) hypothesis and which can be used in calculating |Vud|, the largest element of the Cabibbo-Kobayashi-Maskawa (CKM) quark mixing matrix of the Standard Model. The experimental method used four plastic scintillator detectors in a 3-fold coincidence mode in order to detect the unique 2x511keV+718keV gamma-ray decay signature of 10C. The half-life values obtained from the data were strongly dependent on the detector count rates, but a final value of 19.303 +/- 0.013 s was determined by extrapolating the dependence to zero count rate. This study highlights the significance of systematic errors due to high count rates in precision half-life experiments and raises doubts about both the two previously accepted values of the half-life of 10C.

nucl-ex↗

arXiv2008

Measuring the proton spectrum in neutron decay - latest results with aSPECT

The retardation spectrometer aSPECT was built to measure the shape of the proton spectrum in free neutron decay with high precision. This allows us to determine the antineutrino electron angular correlation coefficient a. We aim for a precision more than one order of magnitude better than the present best value, which is Delta_a /a = 5%. In a recent beam time performed at the Institut Laue-Langevin during April / May 2008 we reached a statistical accuracy of about 2% per 24 hours measurement time. Several systematic effects were investigated experimentally. We expect the total relative uncertainty to be well below 5%.

nucl-ex↗