Neutron Beam Effects on Spin-Exchange-Polarized<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi>He</mml:mi><mml:mprescripts /><mml:none /><mml:mn>3</mml:mn></mml:mmultiscripts></mml:math>

Sharma, M.; Babcock, Earl; Andersen, K.H.; Barrón‐Palos, L.; Becker, M.; Boag, S.; Chen, Wangchun; Chupp, T. E.; Danagoulian, Areg; Gentile, Thomas R.; Klein, A.; Penttilä, S. I.; Petoukhov, A.; Söldner, T.; Tardiff, E. R.; Walker, Thad; Wilburn, W. S.

doi:10.1103/physrevlett.101.083002

Cited by 20 publications

(8 citation statements)

References 27 publications

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“…However, neutron absorption by 3 He yields an energetic triton and proton that produce ionization in the gas. Studies revealed that the decrease in 3 He polarization was due to decreased alkali-metal polarization [83]. In later experiments with two orders of magnitude higher neutron flux obtained on the PF1b beam line [84] at the Institut Laue-Langevin (ILL), the alkali-metal spin relaxation rate was found to be proportional to square root of the neutron flux density, consistent with expectations for relaxation induced by ionization [85].…”

Section: Pos(pstp 2013)022supporting

confidence: 73%

Polarized 3He spin filters for neutron science

Gentile¹

2014

Proceedings of XVth International Workshop on Polarized Sources, Targets, and Polarimetry — PoS(PSTP2013)

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The large spin dependence of the absorption cross section for neutrons by 3 He gas provides a method to polarize neutron beams. For certain applications, such polarized 3 He-based neutron "spin filters" have advantages over conventional neutron optical polarizing methods. Spin filters operate at all neutron wavelengths, can cover a large angular range and/or a large energy range, and decouple neutron polarization from energy selection. Both spin-exchange optical pumping (SEOP) and metastability-exchange optical pumping (MEOP) are currently being employed to polarize 3 He spin filters at various neutron facilities worldwide. We focus on the development and application of SEOP-based neutron spin filters at the National Institute of Standards and Technology (NIST), Center for Neutron Research (NCNR). The combination of long relaxation time spin filter cells, high power spectrally narrowed diode lasers, and the use of Rb/K mixtures have allowed us to reach 3 He polarizations up to 85 % in spin filter cells ≈1 liter in volume. Studies have revealed limits to the achievable polarization from temperature-dependent relaxation and unexplained magnetic field dependence for relaxation in SEOP cells. Applications include neutron scattering methods such as triple-axis spectrometry and small angle neutron scattering, and fundamental neutron physics. In most neutron scattering applications, cells are transported to the beam line and stored in a magnetically shielded solenoid or box. A recent focus has been apparatus for wide-angle neutron polarization analysis. A measurement of the spin-dependence of the neutron-3 He scattering length was performed with a small, polarized 3 He cell located inside a neutron interferometer. A precision measurement of the neutron polarization for this experiment was also performed with a 3 He spin filter. Use of spin filters in high flux neutron beams have revealed beam-induced alkali-metal relaxation and long term effects on SEOP spin filter cells.

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Section: Pos(pstp 2013)022supporting

confidence: 73%

Polarized 3He spin filters for neutron science

Gentile¹

2014

Proceedings of XVth International Workshop on Polarized Sources, Targets, and Polarimetry — PoS(PSTP2013)

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“…An alternative polarizer is a steady-state polarized 3 He spin filter [49]. Intense cold neutron beams have been shown to affect the rubidium and 3 He polarization [50]; however, this appears to be a solvable technical challenge [51]. The 560 µT guide field can be reduced by using an adiabatic-fast-passage neutron spin flipper and effective shimming of the magnetic field along with shielding of external field perturbations.…”

Section: A Potential Improvementsmentioning

confidence: 99%

Search for aT-odd,P-even triple correlation in neutron decay

et al. 2012

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Background Time-reversal-invariance violation, or equivalently CP violation, may explain the observed cosmological baryon asymmetry as well as indicate physics beyond the Standard Model. In the decay of polarized neutrons, the triple correlation D Jn · (pe × pν ) is a parity-even, time-reversal-odd observable that is uniquely sensitive to the relative phase of the axial-vector amplitude with respect to the vector amplitude. The triple correlation is also sensitive to possible contributions from scalar and tensor amplitudes. Final-state effects contribute at the level of 10 −5 and can be calculated with a precision of 1% or better.Purpose We have improved the sensitivity to T-odd, P-even interactions in nuclear beta decay.Methods We measured proton-electron coincidences from decays of longitudinally polarized neutrons with a highly symmetric detector array designed to cancel the time-reversal-even, parity-odd Standard-Model contributions to polarized neutron decay. Over 300 million proton-electron coincidence events were used to extract D and study systematic effects in a blind analysis.Results We find D = [−0.94 ± 1.89(stat) ± 0.97(sys)] × 10 −4 . This differs from our recent paper (Phys. Rev. Lett. 107 102301 (2011)) due to refinement of corrections for background and backscattering.Conclusions This is the most sensitive measurement of D in nuclear beta decay. Our result can be interpreted as a measurement of the phase of the ratio of the axial-vector and vector coupling constants (CA/CV = |λ|e iφ AV ) with φAV = 180.012• ± 0.028 • (68% confidence level). This result can also be used to constrain time-reversal violating scalar and tensor interactions that arise in certain extensions to the Standard Model such as leptoquarks.

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“…The guide is used in its non-polarising configuration with Bender 2. A 3 He spin filter cell is installed in the beam definition area, either a MEOP cell which can already stand the neutron intensity or a SEOP cell if the performance losses in high flux [31] can be compensated. An adiabatic fast passage spin flipper for 3 He allows inverting the spin direction in-situ which provides possibilities for systematic checks.…”

Section: Polarisation With Analytical Wavelength Dependencementioning

confidence: 99%

ANNI – A pulsed cold neutron beam facility for particle physics at the ESS

et al. 2019

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Pulsed beams have tremendous advantages for precision experiments with cold neutrons. In order to minimise and measure systematic effects, they are used at continuous sources in spite of the related substantial decrease in intensity. At the European Spallation Source ESS these experiments will profit from the pulse structure of the source and its 50 times higher peak brightness compared to the most intense reactor facilities, making novel concepts feasible. Therefore, the cold neutron beam facility for particle physics ANNI was proposed as part of the ESS instrument suite. The proposed design has been re-optimised to take into account the present ESS cold moderator layout. We present design considerations, the optimised instrument parameters and performance, and expected gain factors for several reference experiments.

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Neutron Beam Effects on Spin-Exchange-PolarizedHe3

Cited by 20 publications

References 27 publications

Polarized 3He spin filters for neutron science

Polarized 3He spin filters for neutron science

Search for aT-odd,P-even triple correlation in neutron decay

ANNI – A pulsed cold neutron beam facility for particle physics at the ESS

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