Nitrogen dilution effect for small angle GDH experiment in JLab Hall-A

In the GDH sum rule measurement in JLab Hall-A, to obtain the cross section of electron scattering on polarized ³He and its asymmetry in different helicity states, the dilution effect from unpolarized nitrogen mixed in the polarized ³He target were calculated at different kinematic settings.     

Development of a Spin-Exchange Optical Pumping-Based Polarized ~3He System at the China Spallation Neutron Source(CSNS)

Polarized ~3He neutron spin filters(NSFs) can be used as a vital tool for neutron polarization production and analysis.The China Spallation Neutron Source(CSNS),as one of the major neutron facilities in China,has committed resources to the development of a polarized ~3He NSF program to support its growing polarized neutron research.A spin-exchange optical pumping(SEOP)-based polarized ~3He system and other necessary hardware for NSF transport has been recently developed.The performance of the system is benchmarked using an in-house developed cell named "Trident".Neutron beam measurements yield a ~3 He polarization of 77% with over 200 h of on-beam relaxation time.Combining this newly developed SEOP system with the recently reported cell fabrication station,CSNS is now capable of the fully self-sustained production of ~3He NSFs that shall support its future neutron polarization research.     

Thoughts on polarimetry for 3He beams at RHIC

The Relativistic Heavy Ions Collider (RHIC) has accelerated polarized proton beams for physics since 2001. As part of the future eRHIC program and in order to enhance access to the down quark, a program to accelerate polarized ³He in the AGS and RHIC is envisioned. To that end, a polarized ³He source is being built at MIT. This will be installed on the BNL EBIS source in preparation for injection into the booster and AGS. As an early exercise, in June 2012, unpolarized ³He beams have been accelerated in the AGS. This paper will peruse some potential ideas for ³He polarimetry and calibration that could be utilized at the AGS as well as RHIC. The current proton polarimetry program serves as a guide.     

Experiments with longitudinally polarized electrons in a storage ring using a siberian snake

We report on first measurements with polarized electrons stored in a medium-energy ring and with a polarized internal target. Polarized electrons were injected at 442 MeV (653 MeV), and a partial (full) Siberian snake was employed to preserve the polarization. Longitudinal polarization at the interaction point and polarization lifetime of the stored electrons were determined with laser backscattering. Spin observables were measured for electrodisintegration of polarized 3He, with simultaneous detection of scattered electrons, protons, neutrons, deuterons, and 3He nuclei, over a large phase space.     

Optimised adiabatic fast passage spin flipping for He neutron spin filters

We describe here a method of performing adiabatic fast passage (AFP) spin flipping of polarized ³He used as a neutron spin filter (NSF) to polarize neutron beams. By reversing the spin states of the ³He nuclei the polarization of a neutron beam can be efficiently reversed allowing for the transmission of a neutron beam polarized in either spin state. Using an amplitude modulated frequency sweep lasting 500 ms we can spin flip a polarized ³He neutron spin filter with only 1.8×10⁻⁵ loss in ³He polarization. The small magnetic fields (10-15 G) used to house neutron spin filters mean the ³He resonant frequencies are low enough to be generated using a computer with a digital I/O card. The versatility of this systems allows AFP to be performed on any beamline or in any laboratory using ³He neutron spin filters and polarization losses can be minimised by adjusting sweep parameters.     

Target mass correction on the 3He polarized structure function

Target mass correction (TMC) is employed to amend the polarized helium structure functions, ³He . The structure function can be obtained via the convolution of the light cone momentum distribution with the polarized structure of the proton and neutron. The calculation of the polarized structure function of the nucleon is based on the constituent quark model. The analytical result for ³He polarized structure function at low values of Q² is not in good agreement with the available experimental data. The reliability of calculations is increased using TMC effect. New comparison confirms a better agreement with the experimental data.     

A high-pressure polarized <Superscript>3</Superscript>He gas target for nuclear-physics experiments using a polarized photon beam

Following the first experiment on three-body photodisintegration of polarized ³He utilizing circularly polarized photons from High-Intensity Gamma Source (HIg \gamma S) at Duke Free Electron Laser Laboratory (DFELL), a new high-pressure polarized ³He target cell made of pyrex glass coated with a thin layer of sol-gel doped with aluminum nitrate nonahydrate has been built in order to reduce the photon beam-induced background. The target is based on the technique of spin exchange optical pumping of hybrid rubidium and potassium and the highest polarization achieved is ∼ 62% determined from both NMR-AFP and EPR polarimetries. The phenomenological parameter that reflects the additional unknown spin relaxation processes, X , is estimated to be ∼ 0.10 and the performance of the target is in good agreement with theoretical predictions. We also present beam test results from this new target cell and the comparison with the GE180 ³He target cell used previously at HIg \gamma S. This is the first time that the sol-gel coating technique has been used in a polarized ³He target for nuclear-physics experiments.     

Polarized fusion

Since more than 50 years it has been discussed to increase the gain of nuclear fusion reactors with the use of polarized fuel. For example, the total cross sections of the fusion reactions d + t → ⁴He + n or ³He + d → ⁴He + p are increased by a factor of about 1.5 if the spins of both incoming particles are aligned. But before polarized fuel can be used for energy production in the different types of reactors, a number of questions must be answered. In this contribution we give an overview on our various activities in this field of research.     

The generalized Gerasimov-Drell-Hearn sum of the neutron at low Q<Superscript>2</Superscript> using a polarized <Superscript>3</Superscript>He target

A recently finished experiment to evaluate the generalized Gerasimov-Drell-Hearn sum on ³He and the neutron in a Q² range between 0.03 GeV²/c² and 1.2 GeV²/c² will be discussed. The experiment was conducted in Hall A at Jefferson Lab using a polarized ³He target in combination with a highly polarized electron beam.     

Applications of He neutron spin filters at the NCNR

At the NIST Center for Neutron Research (NCNR), we have applied ³He neutron spin filters (NSFs) to the instruments where ³He NSFs are advantageous, such as thermal triple-axis spectrometry, small-angle neutron scattering, and diffuse reflectometry. We present the status of our development and application of this method, including polarized gas production by spin-exchange optical pumping, magnetostatic cavities for storage of the polarized gas on the beam line, and nuclear magnetic resonance (NMR)-based, on-line monitoring and reversal of the ³He polarization. We present the status of developing user-friendly interfaces incorporated into the instrument software to handle these ³He neutron spin filters while taking data and performing data analysis. Finally we discuss the status of development of a polarization capability on the multi-axis crystal spectrometer, which requires polarization analysis over a 220° angular range.     

Electron-Induced Breakup of 3He: Past Achievements, Ongoing Efforts, and a Wish List

The ³He nucleus is a calculable nuclear system (Carlson and Schiavilla in Rev Mod Phys 70:743, 1998) for which our theoretical understanding can be compared with data to an increasingly accurate degree. In turn, the theory faces extensive precise data sets from a series of experiments. Two laboratories are leading the way: MAMI/A1 and the Thomas Jefferson National Accelerator Facility (TJNAF). This paper reviews some of the outstanding current experimental efforts with (polarized or unpolarized) electron scattering on (polarized or unpolarized) ³He targets in these laboratories.     

采用超导量子干涉组件在微特斯拉磁场下获取超极化~3He的核磁共振波谱和影像(英文)

该文以超导量子干涉元件研究光激发氦三极化气体的低磁场磁共振与造影术.使用圆偏极化雷色光将氦三气体极化,超导量子干涉元件磁共振与造影之测量是以磁通耦合方式来进行,超导量子干涉元件是用铋锶钙铜氧高溫超导罐来隔离环境噪音.此方法测得的磁共振信号与影像相较于直接将样品置于杜瓦瓶下方有较高的信噪比,当样品无法靠近感测元件时,此装置具高信噪比特色.磁通耦合方式的超导量子干涉元件低磁场磁共振与造影术及其氦三极化气体的肺部造影在学术与应用上是相当有趣.     

Spin-spin correlation effect on the thermodynamic properties of the polarized liquid 3He at finite temperature

We have used the lowest order constrained variational (LOCV) method to calculate some thermodynamic properties of the polarized liquid ³He at finite temperature with the spin-dependent correlation function. For each value of the temperature and density we have shown that the main contribution to the potential energy comes from the spin-triplet state. For the polarized liquid ³He, we have seen that the differences between the thermodynamic properties of the spin-dependent and the spin-independent cases decrease by increasing both polarization and temperature. For all relevant temperatures and densities, our results do not show any ferromagnetic phase transition.     

Limits to the polarization for spin-exchange optical pumping of 3He

Based on measurements of the temperature dependence of 3He relaxation in a wide range of spin-exchange optical pumping cells, we report evidence for a previously unrecognized surface relaxation process. The relaxation rate was found to be linearly proportional to the alkali-metal density with a slope that exceeds the spin-exchange rate, which limits the polarization for current applications, including neutron spin filters, polarized targets, and polarized gas magnetic resonance imaging. We find that the magnitude of this excess relaxation can vary widely between cells, and that the variation is larger for cells of higher surface to volume ratio. We have observed 3He polarization as high as 81%, but further improvements require understanding the origin of this relaxation.     

Polarized He neutron spin filter program at the JCNS

Polarized neutron instruments will occupy about 80% of the Jülich Centre for Neutron Science (JCNS) instrument park. A successful polarized ³He program will be integral to many of these instruments. We have been focusing the developments on spin-exchange optical pumping (SEOP) to polarize the ³He gas in situ. Where possible, in situ polarization using the SEOP method will provide higher time averaged performance of the instruments. Further this allows a custom-built and independent source of polarized ³He to be developed optimized for each instruments demands. In this paper we will: present an argument for the advantages of in situ polarization; describe an in situ polarizer we have constructed, and initial tests of its performance; describe testing of polarization analysis for small angle neutron scattering on biological samples, and our plans for an in situ polarizer for this application.     

T-violation neutron experiment and polarized3He

An experimental scheme of the spin detailed balance in polarized neutron transmission through a polarized nuclear target is discussed for the T-violation test. The value of the spin detailed balance is estimated by using the data of the scattering amplitudes. The nuclear polarizations of proton,³He and¹³⁹La are discussed for the T-violation experiment.     

Wall relaxation of 3He in spin-exchange cells

The 3He longitudinal spin-relaxation rate T1-1 is crucial for production of highly polarized 3He by spin-exchange optical pumping. We show that T1-1 is increased by a factor of 2-20 solely by exposure of spin-exchange cells to a few-kG magnetic field. The original T1-1 can be restored by degaussing the cell. The effect is attributed to magnetic surface sites and has been observed in both Pyrex and aluminosilicate-glass cells. Our results both advance the understanding of wall relaxation and demonstrate the use of 3He as an extremely sensitive probe of surface magnetism.     

Spin polarized 3He: From basic research to medical applications

Polarization of ³He gas by means of optical pumping is well known since the early 1960s with first applications in fundamental physics. Some thirty years later it was discovered, that one can use hyperpolarized ³He as contrast agent for magnetic resonance imaging of the lung. The wide interest in this new method made it necessary to find ways of polarizing ³He in large quantities with high polarization degrees. A high performance polarizing facility has been developed at the University of Mainz, designed for centralized production of hyperpolarized ³He gas. We present the Mainz concept as well as some examples of numerous applications of spin polarized ³He in fundamental research and medical applications.     

Quark-hadron duality in neutron (3He) spin structure

We present experimental results of the first high-precision test of quark-hadron duality in the spin-structure function g_{1} of the neutron and 3He using a polarized 3He target in the four-momentum-transfer-squared range from 0.7 to 4.0 (GeV/c);{2}. Global duality is observed for the spin-structure function g_{1} down to at least Q;{2}=1.8 (GeV/c);{2} in both targets. We have also formed the photon-nucleon asymmetry A1 in the resonance region for 3He and found no strong Q2 dependence above 2.2 (GeV/c);{2}.     

Study on optical electron polarimeter and measurement of the relative Stokes parameters of weak light

In this paper, we present the research on an optical electron polarimeter, which is used to determine the polarization of an incident electron beam by measuring the relative Stokes parameters of the fluorescence emitted from the He gas following the impact excitation with the electron beam. The fundamental theory of the optical electron polarimeter is discussed with the 3³P→2³S transition of He. The structure and performance of the instrument are described, which are different in some aspects from previous works. The arrangement of the experiment for measuring the relative Stokes parameters of linearly polarized weak light is also investigated, which actually involves the same processes as the polarization measurement with the incident electron beam. The results obtained are in agreement with the theoretical prediction.