共查询到20条相似文献,搜索用时 31 毫秒
1.
《Physics letters. [Part B]》1999,461(4):307-314
Free neutron beta decay provides sensitive tests of the Standard Model of electroweak interaction. A particular class of experiments has now reached a limit set by the imperfect knowledge of the neutron polarisation and of the efficiency of a spin flipper. Standard techniques of polarisation analysis reach a precision of ≥0.25%. In a recent experiment it was shown that an accuracy on the level of a few times 10−4 can be reached within a classical scheme of polarisation analysis, using an opaque spin filter as analyser. In this letter a new scheme is given which takes advantage of a natural degree of freedom of spin filters, resulting in a more sensitive and simpler measurement of neutron polarisation and flipper efficiency. 相似文献
2.
T.J. McKetterickS. Boag J.R. StewartC.D. Frost M.W.A. SkodaS.R. Parnell E. Babcock 《Physica B: Condensed Matter》2011,406(12):2436-2438
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. 相似文献
3.
C.B. Fu T.R. GentileG.L. Jones W.C. Chen R. ErwinS. Watson C. Broholm J.A. Rodriguez-Rivera J. Scherschligt 《Physica B: Condensed Matter》2011,406(12):2419-2423
Polarized 3He neutron spin filters can operate over a wide neutron energy range and provide a large angular acceptance. A compact 3He neutron spin filter system has been developed for the Multi-Axis Crystal Spectrometer at the National Institute of Standards and Technology (NIST) Center for Neutron Research. Sealed 3He cells, polarized by spin-exchange optical pumping, are used as polarizer and analyzer. The polarization of the neutrons incident on the sample is inverted by flipping the polarization of the 3He gas in the polarizer, with only a small effect on the analyzer cells. The cell fabrication process, 3He spin flipper, and the holding magnetic field are discussed and we present the results of a first on-linetest. 相似文献
4.
E. Lelivre-Berna P. Bentley E. Bourgeat-Lami M. Thomas C. Pappas R. Kischnik E. Moskvin 《Physica B: Condensed Matter》2009,404(17):2624-2628
The changes in direction of the neutron spin that take place on scattering by a magnetic interaction vector are highly dependent on their relative directions. In some circumstances, without zero-field polarimeter, it is impossible to distinguish between a simple depolarisation and a rotation of the polarisation vector.Motivated by the investigation of chiral magnetic fluctuations, we have implemented the third-generation zero-field polarimeter Cryopad on the neutron spin-echo spectrometer SPAN at the Helmholtz Centre Berlin (HCB). We present the method and the limitations of this novel technique that is now available on IN15 at the ILL.The huge progress accomplished with 3He neutron spin filters/flippers are going to facilitate the exploitation of polarised beams at spallation sources. Zero-field polarimeters like Cryopad are used routinely at several steady-state sources but their design would be inefficient at a pulse source. We have investigated the possibility to implement a zero-field polarimeter on a time-of-flight spectrometer. We propose a design that would lead to a better efficiency and present the finite element calculations. 相似文献
5.
H. Sato Y. Masuda K. Sakai M. Doi K. Asahi Z. J. Zheng Y. Mori P. P. J. Delheij Y. Matsuda M. Iinuma H. M. Shimizu A. Masaike 《Hyperfine Interactions》1994,84(1):205-209
We have constructed an apparatus to polarize the3He nuclear spin, which will be used as a neutron spin analyzer in T- and P-violation neutron experiments. We report on principles and the present status of the method for the polarization of3He and the determination of its value.On leave from Tohoku University, Aoba-ku, Sendai 980, Japan. 相似文献
6.
W.C. Chen R. Erwin J.W. McIver III S. Watson C.B. Fu T.R. Gentile J.A. Borchers J.W. Lynn G.L. Jones 《Physica B: Condensed Matter》2009,404(17):2663-2666
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. 相似文献
7.
Y. Sakaguchi H. KiraT. Oku T. ShinoharaJ. Suzuki K. SakaiM. Nakamura K. SuzuyaK. Aizawa M. AraiM. Takeda S. WakimotoD. Yamazaki S. KoizumiY. Endoh L.J. Chang Y. ArimotoT. Ino H.M. ShimizuT. Kamiyama K. OhoyamaH. Hiraka K. TsutsumiK. Yamada K. OharaK. Kakurai 《Physica B: Condensed Matter》2011,406(12):2443-2447
Glass cells play an important role in polarized 3He neutron spin filters. To evaluate the scattering and absorption contribution from glass cells during neutron scattering experiments, we measured small-angle scattering and neutron transmission in GE180 and other glasses. The small-angle neutron scattering measurements revealed that the glasses used for 3He spin filters have acceptably lower scattering: dΣ(Q)/dΩ=4-7×10−4 cm−1 at Q=0.03-0.12 Å−1. The transmission measurement was performed at J-PARC. Neutron transmission of about 92% through empty GE180 cells was observed over a wide wavelength range 0.014-7.0 Å. To pursue the possibility of being a structural influence on 3He spin relaxation in GE180 glass cells, we performed precise X-ray diffraction measurement using synchrotron radiation at SPring-8. From these measurements, a structural difference was observed among GE180 glasses with different thermal treatments. 相似文献
8.
E. Babcock S. Boag K.H. Andersen M. Becker C. Beecham F. Bordenave J. Chastagnier W.C. Chen R. Chung T.E. Chupp S. Elmore P. Fouilloux T.R. Gentile D. Jullien E. Lelievre-Berna P. Mouveau A. Petoukhov M. Revert T. Soldner 《Physica B: Condensed Matter》2009,404(17):2655-2658
Polarized 3He has shown its unique characteristics in many areas of polarized neutron scattering, its ability to polarize neutrons at short wavelengths, accept wide-angle and divergent beams and low backgrounds enable new classes of experiments. While polarized 3He is not a steady state solution as commonly applied, the benefits have been shown to offset the drawbacks of polarizing and refreshing the polarization in the neutron spin filter cells. As an extension of this work, in-situ polarization using the spin-exchange optical pumping (SEOP) method was explored as a means to construct a system which could be used to polarize 3He in the state used for an effective neutron spin filter to constant polarization while on the neutron beam. An in-situ SEOP polarizer was constructed. This device utilized many devices and principles developed for neutron spin filters which are polarized off the beam line using either SEOP or metastability exchange optical pumping (MEOP) under the same research program. As a collimation of this work effects of extremely high neutron capture flux density incident on the in-situ polarizer were explored. 相似文献
9.
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. 相似文献
10.
H. Kira Y. Sakaguchi T. Oku J. Suzuki M. Nakamura M. Arai K. Kakurai Y. Endo Y. Arimoto T. Ino H.M. Shimizu T. Kamiyama K. Tsutsumi K. Ohoyama H. Hiraka K. Yamada L.-J. Chang 《Physica B: Condensed Matter》2011,406(12):2433-2435
We have begun the development of an in-situ spin-exchange optical pumping (SEOP) system aiming to use it as a neutron spin filter for incident beam polarization at the Japan Proton Accelerator Research Complex (J-PARC). To use it, it is recommended that the optics be adjusted easily, have high stability, and have a small size. In this paper we improved our previous SEOP system aiming to use it in J-PARC and performed a neutron beam test at the JRR-3 NOP beamline to see the performance of the neutron spin filter (NSF). The polarization of the 3He gas reached 73%. This paper gives the present status of the development of in-situ SEOP system in J-PARC. 相似文献
11.
Takashi Ino Mitsutaka Nakamura Takayuki Oku Takenao Shinohara Jun-ichi Suzuki Kenji Ohoyama Haruhiro Hiraka 《Physica B: Condensed Matter》2009,404(17):2667-2669
We have designed and demonstrated a prototype on-beam spin-exchange optical pumping (SEOP) 3He neutron spin filter (NSF). It is designed as the incident neutron polarizer for spallation neutron sources, where the installation space is limited due to thick radiation shielding. The size of the NSF is roughly 50 cm×50 cm×25 cm including the diode-laser optics with a frequency narrowing external cavity, and a cylindrical 3He cell as large as a diameter of 5 cm and a length of 10 cm can fit. A neutron beam test was performed at the NOP beamline of JRR-3 to see the performance of the NSF. 相似文献
12.
T. Ino Y. ArimotoT. Yoshioka K. MishimaK. Taketani S. MutoH.M. Shimizu H. KiraY. Sakaguchi T. OkuK. Sakai T. ShinoharaJ. Suzuki H. OtonoH. Oide S. YamashitaS. Imajo H. FunahashiM. Yamada Y. IwashitaM. Kitaguchi M. HinoZ. Suzuki T. SanukiT. Seki K. HirotaK. Ikeda H. SatoY. Otake H. OhmoriT. Morishima T. Shima 《Physica B: Condensed Matter》2011,406(12):2424-2428
We measured the neutron beam polarization of the BL05/NOP (Neutron Optics and Physics) beamline at J-PARC with an accuracy of less than 10−3 using polarized 3He gas as a neutron spin analyzer. Precise polarimetry of the neutron beam is necessary to understand the beamline optics as well as for the asymmetry measurements of the neutron beta decay, which are planned in this beamline. 相似文献
13.
Y. Masuda K. Asahi J. Kura Y. Mori H. Sato H. M. Shimizu 《Hyperfine Interactions》1992,74(1-4):149-157
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. 相似文献
14.
The poor knowledge of the spin-dependent neutron scattering length of 3He has until now handicapped nuclear four body theory and the interpretation of excitations in the quantum liquid. We have measured, for the first time directly, the real part of the bound incoherent neutron scattering length, bi′ of 3He. A neutron spin echo spectrometer was used to detect pseudomagnetic precession of polarised neutrons passing through polarised 3He gas. Any absolute calibrations of sample and beam parameters were avoided using simple transmission measurements with non-polarised neutrons. The only a priory information required was the spin-dependent neutron absorption cross section of 3He. The result is bi′ = -2.365(20) fm, which reduces the prior uncertainty by a factor 30. The corresponding new value of the bound incoherent scattering cross section is σi = 1.532(12) barn. Including the known value of the coherent neutron scattering length, we obtain new values for the real parts of the free triplet and singlet neutron scattering lengths, a-′ = 7.370(58) fm and a+′ = 3.278(53) fm. 相似文献
15.
The basic principle for the production of polarised thermal neutrons is discussed and the choice of various crystal monochromators
surveyed. Brief mention of broad-spectrum polarisers is made. The application of polarised neutrons to the study of magnetisation
density distributions in magnetic crystals, the dynamic concept of polarisation, principle and use of polarisation analysis,
the neutron spin-echo technique are discussed. 相似文献
16.
F. F. Karpeshin 《The European Physical Journal A - Hadrons and Nuclei》2010,45(2):251-255
The hard electric dipole radiation from fission fragments of 235U by thermal neutrons is predicted. The radiation arises due to the Strutinsky-Denisov-induced polarisation mechanism. The
probability of the radiation is at the level of 0.0025 per fission, which is in agreement with experiment. The angular distribution
exhibits left-right asymmetry with respect to the plane perpendicular to the neutron polarisation axis. That means that the
emission of gamma quanta at the given angle depends on the neutron polarisation. The asymmetry is at the level of 10-3. This effect is similar to that observed earlier for gamma quanta in binary and alphas in ternary fission. The study of this
effect will give information about dissipation of the collective energy of the surface vibration in fragments with large amplitude,
and gives a picture of the process of snapping back the nuclear surface. 相似文献
17.
B. van den Brandt H. Glättli I. Grillo P. Hautle H. Jouve J. Kohlbrecher J. A. Konter E. Leymarie S. Mango R. P. May A. Michels H. B. Stuhrmann O. Zimmer 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(2):157-165
We have investigated the process of dynamic proton polarisation by means of time-resolved polarised small-angle neutron scattering
(SANS) on frozen solutions of EHBA-CrV molecules in glycerol-water mixtures as a function of the concentration of EHBA-CrV and for different degrees of deuteration of the solvent. In the EHBA-CrV complex, the spins of the 20 protons which surround the paramagnetic CrV can be oriented using the method of dynamic nuclear polarisation (DNP), thereby offering the possibility to create locally
a nuclear spin-dependent contrast for SANS. The time constants which describe the build-up of polarisation around the paramagnetic
centre and the subsequent diffusion of polarisation in the solvent were determined by analysing the temporal evolution of
the nuclear polarisation, which in turn was obtained by fitting a core-shell model to the time-dependent SANS curves. The
results on the spin dynamics obtained using the scattering function of a core-shell could be independently confirmed by evaluating
the integrated SANS intensity. A thermodynamic one-centre model is presented which is able to reproduce the observed dependence
of the proton polarisation times on the proton concentration of the solvent. 相似文献
18.
The project to upgrade the existing single-crystal diffractometer Heisses Einkristal Diffractometer (HEiDi) at FRM II with a polarised neutron option, enabling the investigation of magnetic ground states in single crystals has been ongoing since autumn 2004. After a detailed investigation of the possible options it has been decided to develop and rebuild the secondary spectrometer and keep the HEiDi monocromator. The new instrument has been named POLI-HEiDi as an abbreviation of Polarisation Investigator at HEiDi. Two different zero-field polarimeters will be made available for spherical neutron polarimetry, Cryoapad and MuPAD. Both, polarisation and analysis will be performed with polarised 3He spin filters. Several new and important components of the instrument have recently been commissioned. In this report we present these components and show how they fit with the design of the whole instrument. 相似文献
19.
20.
Zhao-Ming Zeng Hui Gong Jian-Min Li Qian Yue Zhi Zeng Jian-Ping Cheng 《中国物理C(英文版)》2017,41(5):056002-056002
A low background thermal neutron flux detection system has been designed to measure the ambient thermal neutron flux of the second phase of the China Jinping Underground Laboratory(CJPL-Ⅱ),right after completion of the rock bolting work.A ~3He proportional counter tube combined with an identical ~4He proportional counter tube was employed as the thermal neutron detector,which has been optimised in energy resolution,wall effect and radioactivity of construction materials for low background performance.The readout electronics were specially designed for long-term stable operation and easy maintenance in an underground laboratory under construction.The system was installed in Lab Hall No.3 of CJPL-Ⅱ and accumulated data for about 80 days.The ambient thermal neutron flux was determined under the assumption that the neutron field is fully thermalized,uniform and isotropic at the measurement position. 相似文献