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Title: A Liquid Parahydrogen Target for the Measurement of a Parity-violating Gamma Asymmetry in Polarized Neutron Capture on Protons

Abstract

A 16 l liquid parahydrogen target has been developed for a measurement of the parity-violating {gamma}-asymmetry in the capture of polarized cold neutrons on protons in the {rvec n} + p {yields} d + {gamma} reaction by the NPDGamma collaboration. The target system was carefully designed to meet the stringent requirements on systematic effects for the experiment and also to satisfy hydrogen safety requirements. The target was designed to preserve the neutron polarization during neutron scattering on liquid hydrogen (LH{sub 2}), optimize the statistical sensitivity to the {rvec n} + p {yields} d + {gamma} reaction, minimize backgrounds coming from neutron interaction with the beam windows of the target cryostat, minimize LH{sub 2} density fluctuations which can introduce extra noise in the gamma asymmetry signal, and control systematic effects. The target incorporates two mechanical refrigerators, two ortho-para convertors, an aluminum cryostat, an aluminum target vessel shielded with {sup 6}Li-rich plastic, a hydrogen fill/vent line with a passive recirculation loop to establish and maintain the equilibrium ortho-para ratio, a hydrogen relief system coupled to a vent stack, a gas handling system, and an alarm and interlock system. Low Z, nonmagnetic materials were used for the target vessel and cryostat. Pressure andmore » temperature sensors monitored the thermodynamic state of the target. Relative neutron transmission measurements were used to monitor the parahydrogen fraction of the target. The target was thoroughly tested and successfully operated during the first phase of the NPDGamma experiment conducted at the FP12 beam line at Los Alamos Neutron Science Center (LANSCE). An upgraded version of the target system will be used in the next stage of the experiment, which will be performed at the Fundamental Neutron Physics Beam (FnPB) line of the Spallation Neutron Source at Oak Ridge National Laboratory.« less

Authors:
 [1];  [2];  [2]
  1. Indiana University
  2. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
988255
DOE Contract Number:  
DE-AC05-00OR22725
Resource Type:
Journal Article
Journal Name:
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Additional Journal Information:
Journal Volume: 620; Journal Issue: 40212; Journal ID: ISSN 0168-9002
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ALUMINIUM; ASYMMETRY; CAPTURE; COLD NEUTRONS; FLUCTUATIONS; HYDROGEN; INTERLOCKS; MONITORS; NEUTRON SOURCES; NEUTRONS; POLARIZATION; PROTONS; REFRIGERATORS; SAFETY; SCATTERING; SENSITIVITY; SPALLATION; TARGETS; THERMODYNAMICS

Citation Formats

Santra, S, Bowman, James D, and Penttila, Seppo I. A Liquid Parahydrogen Target for the Measurement of a Parity-violating Gamma Asymmetry in Polarized Neutron Capture on Protons. United States: N. p., 2010. Web. doi:10.1016/j.nima.2010.04.135.
Santra, S, Bowman, James D, & Penttila, Seppo I. A Liquid Parahydrogen Target for the Measurement of a Parity-violating Gamma Asymmetry in Polarized Neutron Capture on Protons. United States. https://doi.org/10.1016/j.nima.2010.04.135
Santra, S, Bowman, James D, and Penttila, Seppo I. Sat . "A Liquid Parahydrogen Target for the Measurement of a Parity-violating Gamma Asymmetry in Polarized Neutron Capture on Protons". United States. https://doi.org/10.1016/j.nima.2010.04.135.
@article{osti_988255,
title = {A Liquid Parahydrogen Target for the Measurement of a Parity-violating Gamma Asymmetry in Polarized Neutron Capture on Protons},
author = {Santra, S and Bowman, James D and Penttila, Seppo I},
abstractNote = {A 16 l liquid parahydrogen target has been developed for a measurement of the parity-violating {gamma}-asymmetry in the capture of polarized cold neutrons on protons in the {rvec n} + p {yields} d + {gamma} reaction by the NPDGamma collaboration. The target system was carefully designed to meet the stringent requirements on systematic effects for the experiment and also to satisfy hydrogen safety requirements. The target was designed to preserve the neutron polarization during neutron scattering on liquid hydrogen (LH{sub 2}), optimize the statistical sensitivity to the {rvec n} + p {yields} d + {gamma} reaction, minimize backgrounds coming from neutron interaction with the beam windows of the target cryostat, minimize LH{sub 2} density fluctuations which can introduce extra noise in the gamma asymmetry signal, and control systematic effects. The target incorporates two mechanical refrigerators, two ortho-para convertors, an aluminum cryostat, an aluminum target vessel shielded with {sup 6}Li-rich plastic, a hydrogen fill/vent line with a passive recirculation loop to establish and maintain the equilibrium ortho-para ratio, a hydrogen relief system coupled to a vent stack, a gas handling system, and an alarm and interlock system. Low Z, nonmagnetic materials were used for the target vessel and cryostat. Pressure and temperature sensors monitored the thermodynamic state of the target. Relative neutron transmission measurements were used to monitor the parahydrogen fraction of the target. The target was thoroughly tested and successfully operated during the first phase of the NPDGamma experiment conducted at the FP12 beam line at Los Alamos Neutron Science Center (LANSCE). An upgraded version of the target system will be used in the next stage of the experiment, which will be performed at the Fundamental Neutron Physics Beam (FnPB) line of the Spallation Neutron Source at Oak Ridge National Laboratory.},
doi = {10.1016/j.nima.2010.04.135},
url = {https://www.osti.gov/biblio/988255}, journal = {Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment},
issn = {0168-9002},
number = 40212,
volume = 620,
place = {United States},
year = {2010},
month = {5}
}