Polarimetry Studies for the NPDGamma Experiment at the SNS
Polarimetry Studies for the NPDGamma Experiment at the SNS

Author: Mostafa Jon Dadras

Publisher:

Published: 2009

Total Pages: 72

ISBN-13:

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The NPDGamma collaboration aims to measure a parity_violating directional gamma-ray asymmetry from the capture of polarized cold neutrons on protons. The asymmetry, predicted to be on the order of 50 ppb, is a result of the weak interaction between mesons and nucleons during the neutron capture reaction. The experiment is designed to make a statistics limited measurement of the asymmetry at the level of about 20%. The experiment will be carried out at the Fundamental neutron Physics Beamline (FnPB) at the Spallation Neutron Source (SNS). The neutron beam is polarized by a super_mirror polarizer. A 9.5 G magnetic field guides the neutron spin to a liquid para-hydrogen target, where the neutrons capture forming a deuteron and a 2.2 MeV gamma-ray. The gamma_rays will be detected by a cylindrical array of CsI scintillating crystals. The beam polarization is reversed with the aid of a resonant RF Spin Rotator (RFSR). This thesis considers different methods for determining the beam polarization and efficiency of the RFSR.

Determination of the Gamma-ray Asymmetry in the Capture of Polarized Neutrons on Hydrogen and Deuterium
Determination of the Gamma-ray Asymmetry in the Capture of Polarized Neutrons on Hydrogen and Deuterium

Author:

Publisher:

Published: 2001

Total Pages: 4

ISBN-13:

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The n+p→d+[gamma] experiment measures the parity-violating directional gamma-ray asymmetry, A[gamma], with uncertainties of 0.5x10−8 when cold polarized neutrons are captured by para-hydrogen. This precision measurement will determine the long-range pion-nucleon weak coupling constant, H{sub {pi}}1, with a precision of 10% of its predicted value, and thus will help to clarify our understanding of the weak interaction between nucleons. The n+p→d+[gamma] experiment on the SNS beamline 14B is designed to take advantage of the high intensity of the source and its pulsed nature. The experiment requires a 30-Hz pulsed beam for optimal performance. In three months of run time the experiment will achieve a statistical uncertainty of 0.5x10−8.

A Liquid Helium Neutron Polarimeter and Its Application to the Reaction 28Si(d,n)29P
A Liquid Helium Neutron Polarimeter and Its Application to the Reaction 28Si(d,n)29P

Author: Sheung Tsing Lam

Publisher:

Published: 1967

Total Pages: 0

ISBN-13:

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A neutron time-of-flight system using a 5.5 MeV Van de Graaff with a Mobley compression magnet was set between the target and liquid helium polarimeter for the measurement of fast neutron polarization. The polarization system was calibrated with neutrons from the D(d,n) 3 He reaction at deuteron energies of 3.0, 4.0, 5.0 and 6.0 MeV and at a neutron emmision angle of 45°(c.m). Good agreement was found between the present measurements and those of Dubbeldam and Walter. The polarization angular distributions of neutrons to the ground, 1.38 and 1.96 MeV states of 29 P from the reaction 28 Si(d,n) 29 P were measured at a deuteron energy of 5.0 MeV. The polarization angular distribution corresponding to the ground state (£p=0) group is in good qualitative agreement with the derivative rule. Spin dependent effects are observed in the polarization distributions of the 1.38 (j=£ - -j) and the 1.96 (j=£p+ y) MeV states. The DWBA code written by B.E.F. Macefield was used in the calculation of neutron polarization. Fair agreement between the DWBA prediction and the polarization measurements to the ground state of 28 P is found, but there is very poor agreement for the 1.38 MeV state. As for the 1.96 MeV state there is some agreement in the shape of the polarization distribution in the forward angles.