25 research outputs found
An Absolute Measurement of Neutron Flux Using Calorimetry
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Measurement of the Neutron Lifetime by Counting Trapped Protons
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Measurement of the Neutron Lifetime by Counting Trapped Protons
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Fast Neutron Detection with 6Li-loaded Liquid Scintillator
We report on the development of a fast neutron detector using a liquid
scintillator doped with enriched Li-6. The lithium was introduced in the form
of an aqueous LiCl micro-emulsion with a di-isopropylnaphthalene-based liquid
scintillator. A Li-6 concentration of 0.15 % by weight was obtained. A 125 mL
glass cell was filled with the scintillator and irradiated with fission-source
neutrons. Fast neutrons may produce recoil protons in the scintillator, and
those neutrons that thermalize within the detector volume can be captured on
the Li-6. The energy of the neutron may be determined by the light output from
recoiling protons, and the capture of the delayed thermal neutron reduces
background events. In this paper, we discuss the development of this 6Li-loaded
liquid scintillator, demonstrate the operation of it in a detector, and compare
its efficiency and capture lifetime with Monte Carlo simulations. Data from a
boron-loaded plastic scintillator were acquired for comparison. We also present
a pulse-shape discrimination method for differentiating between electronic and
nuclear recoil events based on the Matusita distance between a normalized
observed waveform and nuclear and electronic recoil template waveforms. The
details of the measurements are discussed along with specifics of the data
analysis and its comparison with the Monte Carlo simulation
Measurement of the Neutron Lifetime Using a Proton Trap
Abstract not availableJRC.D-Institute for Reference Materials and Measurements (Geel
Measurement of the Neutron Lifetime by Counting Trapped Protons in a Cold Neutron Beam
A measurement of the neutron lifetime Tn performed by the absolute clounting of in-beam neutrons and their decay protons has been completed. Protons confined in a quasi-Penning trap were accelerated onto a silicon detector held a a high potential and counted with nearly unit efficiency. The neutrons were counted by a device with an efficiency inversely proportional to neutron velocity, which cancels the dwell time of the neutron beam in trap. The result is Tn=(886.3 +/- 1.2 [stat] +/- 3.2 [sys])s, which is the most precise measurement of the lifetime using an in-beam method. The systematic technique and apparatus, data analysis, and investigation of systematic uncertainties are discussed in detail.JRC.D.2-Reference material
The significance of a positive cutaneous immunofluorescence test in systemic lupus erythematosus
International key comparison of neutron fluence measurements in monoenergetic neutron fields - CCRI(III)-K11
To ensure the validity of their national standards, National Metrology Institutes, NMIs, participate regularly in international comparisons. In the area of neutron metrology, Section III of the Consultative Committee for Ionizing Radiation is in charge of the organization of these comparisons. From September 2011 to October 2012, the eleventh key comparison, named CCRI(III)-K11, took place at the AMANDE facility of the LNE-IRSN, in France. Participants from nine NMIs came with their own primary reference instruments, or instruments traceable to primary standards, with the aim of determining the neutron fluence, at 1 m distance from the target in vacuum, per monitor count at four monoenergetic neutron fields: 27 keV, 565 keV, 2.5 MeV and 17 MeV. The key comparison reference values (KCRV) were evaluated as the weighted mean values of the results provided by seven participants. The uncertainties of each KCRV are between 0.9 % and 1.7 %. The degree of equivalence (DoE), defined as the deviation of the result reported by the laboratories for each energy from the corresponding KCRV, and the associated expanded uncertainty are also reported and discussed