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Melkonian, E.

doi:10.1103/physrev.76.1750

Cited by 105 publications

(23 citation statements)

References 22 publications

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“…The thermal and cold neutron total cross sections for scattering from gases have been the subject of earlier investigations for molecular [7] [8] and noble gases [9] and found in agreement with theoretical expectations. Recently the ultracold neutron scattering cross section for deuterium gas was measured [10] for better understanding of the mechanism of ultracold neutron production in gases, liquids and solids.…”

Section: Introductionsupporting

confidence: 64%

“…and ! data from [7] and used the result to estimate the cross section for air. For D2 gas, scattering cross sections have been measured down to UCN energies at 25 K [10], and we scale this to 300 K assuming that the cross section scales as .…”

Section: Theoretical Considerationsmentioning

confidence: 99%

“…For H2 and D2 the measured values from ref. [7] have been scaled to our energy; for D2 the measurements with UCN have been scaled from 20K D2 temperature. We estimated the upscattering cross section for air by scaling the results for O2 and N2 in Ref.…”

Section: Fittingmentioning

confidence: 99%

“…We estimated the upscattering cross section for air by scaling the results for O2 and N2 in Ref. [7] to our energies, and adding these according to the partial pressures of these gases in air.…”

Section: Fittingmentioning

confidence: 99%

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Upscattering of ultracold neutrons from gases

Seestrom¹,

Adamek²,

Barlow³

et al. 2015

Phys. Rev. C

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Abstract. We present measurements of the upscattering cross sections of ultracold neutrons (UCN) from room temperature hydrogen, deuterium, neon, argon, xenon, C 4 H 10 , CF 4 and air. The values of these cross sections are important for estimating the loss rate of trapped neutrons due to residual gas, and are therefore of importance for neutron lifetime measurements using UCN. Cross sections were obtained from a combined analysis of the UCN attenuation in a gas cell and direct measurement of the neutrons upscattered in the cell. The effects of the UCN velocity and path-length distributions were accounted for using a Monte Carlo transport code. Results are compared with measurements at higher neutron energy as well as with calculations.

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Section: Introductionsupporting

confidence: 64%

Section: Theoretical Considerationsmentioning

confidence: 99%

Section: Fittingmentioning

confidence: 99%

Section: Fittingmentioning

confidence: 99%

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Upscattering of ultracold neutrons from gases

Seestrom¹,

Adamek²,

Barlow³

et al. 2015

Phys. Rev. C

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“…For the case where molecules are of finite temperature, the cross section of hydrogen increases below 0.5 eV as the inverse of neutron energy, resulting in an average cross section of approximately 40 barns. 20,21 4. Postprocessing of Reconstructions.…”

Section: The Hydrogen Attenuation Coefficientmentioning

confidence: 99%

Neutron tomography developments and applications

Richards¹,

Gibbons²,

Shields³

2004

Applied Radiation and Isotopes

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Neutron radiography has been in use as a nondestructive testing technique for the past fifty years. The neutrons' unique ability to image certain elements and isotopes that are either completely undetectable or poorly detected by other NDI methods makes neutron radiography an important tool for the NDI community. Neutron radiography like other imaging techniques takes a number of different forms (i.e., film, radioscopic, transfer methods, tomography, etc.) This paper will describe the neutron tomography system developed at the University of California, Davis McClellan Nuclear Radiation Center (UC Davis/MNRC), and the applications for both research and commercial uses.The neutron radiography system at the UC Davis/MNRC has been under development for four years. The initial system was developed to find very low concentrations of hydrogen (i.e., < 200 ppm). In order to achieve these low detection levels, it was necessary to perform both pre-and post-processing of the tomographs.The pre-processing steps include corrections for spatial resolution and random noise effects. Images are corrected for systematic noise errors and beam hardening. From these data the attenuation coefficient is calculated.The post-processing steps include alignment of the collected images, determining the center of mass, and, finally, using the filtered back-projection routine from the Donner Algorithms Library to obtain the final images.Since its initial development, the tomography system has been used very successfully to find low levels of hydrogen in a metal matrix. Further uses of the system have been to verify the exact placement, in three dimensions, of "O -rings" in large metal valve bodies, and to map the location and extent of veins in porous and high-density rocks of various different kinds.These examples show that neutron tomography is becoming a needed inspection technique for the 21 st century.

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Magnetic form factor of molecular oxygen

Alikhanov

Ilyina

Smirnov

1972

Physica Status Solidi (b)

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Using neutron diffraction the magnetic form factor f of oxygen is investigated in the solid monoclinic cr-phase (2' < 23.88 OK). The antiferromagnetic reflections of cr-0, (001) and (loo), containing the purely spin magnetic scattering on x-electrons, may give the values of f for sin 012 equaling to 0.1047 and 0.1242, respectively. The data of magnetic diffraction on KO, are also considered: in the magnetic structure proposed the antiferromagnetic reflections (001) and (110) (sin O/A is equal to 0.0735 and 0.1260, respectively) are again due to the orientation of the Tc-orbital spin moments (orbital moment is frozen). The whole set of obtained values f for 0, and 0; are in reasonable agreement with the calculated dependences of f. MeTOHOM HII@paKUMkI HeiTPOHOB IICCJIeHyeTCR MarHLlTHbIn @OPM-#aKTOP KIICJIO-pOAa f B TBepHOn MOHOKJIHHHOfi Ct-@a3e (T < 23,88 O H ) . AHTH@ePPOMarHHTHbIe oTpameHm cr-0, (001) EI (loo), conepmawie WCTO cnmoBoe MarHmHoe pacceHm e Ha x -m e~~p o~a x IIO~BOJIIIJIH I I~B J I~Y~ 3~a q e~m f UJIH sin O/A, pamoro 0,1047 M 0,1242, COOTBeTCTBeHHO. TaK me PaCCMOTpeHM HaHHble MarklMTHOfi AH@paKUHU Ha KO, : B npe&llOHteHHOfi MaI' HATHOft CTPYKTYpe aHTPi@eppOMarHHTHbIe OTpa-HCetIIIR (001) II (110) (Sin e p paBeH 0,0735 M 0,1260, COOTBeTCTBeHHO) BHOBb o6ycno-BJIeHbI OpEIeHTaUMefi CnMHOBbIX MOMeHTOB (Op6MTaJIbHbIfi MOMeHT 3aMOpOMeH) x -o p 6~~a n e t .COBOKYnHOCTb IlOJIyqeHHbIX 3HaseHMfi f nJIH 0, M 0, YAOBJIeTBOPH-TeJIbHO COrJIaCyIOTCH C BbIWXCJIeHHbIMH 3aBMCHMOCTRMH &TIII f .

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Slow Neutron Velocity Spectrometer Studies ofO2,N2, A,

Cited by 105 publications

References 22 publications

Upscattering of ultracold neutrons from gases

Upscattering of ultracold neutrons from gases

Neutron tomography developments and applications

Magnetic form factor of molecular oxygen

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