Application of an omegatron type high resolution mass spectrometer for the analysis of mixtures of hydrogen and helium isotopes

Engelmann, U.; Glugla, M.; Penzhorn, R.-D.; Ache, Hans J.

doi:10.1016/0168-9002(91)90420-u

Cited by 21 publications

(5 citation statements)

References 8 publications

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“…This technology can usually achieve separation of 4He and D2 peaks, provided they do not prevail too much over each other. More recently, quadrupole mass spectrometers operating in the second stability region of the Mathieu diagram [2,12] have been developed, featuring a resolving power at mass 4 of up to -755.…”

Section: State Of the Artmentioning

confidence: 99%

“…However, during a leak test, the wall of the plasma chamber will release large quantities of deuterium, so that a conventional helium leak detector will not be able to discriminate a small amount of leaked 4He in such a high background. High field magnetic sector mass spectrometers, such as the Omegatron used at JET [ 1,2], have been claimed to have sufficient resolving power for this purpose. However, these analyzers feature a rather slow response time and require large and heavy magnets (0.3-0.5 T) in order to achieve the necessary resolution.…”

Section: Introductionmentioning

confidence: 99%

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A powerful tool to quantitatively detect tiny amounts of 4He in a deuterium rich background for fusion research

Frattolillo

Ninno

2007

2007 IEEE 22nd Symposium on Fusion Engineering

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The detection of tiny amounts of 4He in a deuterium rich atmosphere (as well as of 3He in a tritium background) is of great relevance in fusion research. One of the main concerns in a d-t fusion experiment is to prevent significant accumulation of 4He ashes in the core plasma, since this would result in a dilution of the d-t fuel and in a consequent reduction of the fusion power output. In order to control the impurity concentration in the core plasma and to sustain the fuel density, several active pumping methods for 4He (and other impurities) have been proposed, such as divertors or pump limiters. A quantitative analysis of the exhausts of such devices can provide a useful evaluation of the effectiveness of different methods and configurations, by comparing the related 4He content. Helium leak detection is a further major problem in fusion research. Vacuum tightness of the large torus vessel is indeed a rigorous requirement, in order to minimize the impurity content of the plasma. However, due to the strong deuterium release by the wall of the vacuum vessel, a conventional helium leak detector would not be able to discriminate a small amount of leaked 4He in such a high deuterium background. Determination of tritium activity by 3He in-growth method also requires a mass spectrometric analysis system capable to detect small changes of 3He content in a tritium background. A new method has been developed at ENEA Frascati, allowing quantitative detection of extremely small amounts of Helium isotopes (and other inert gases) in a deuterium rich atmosphere using a conventional (i.e. normal resolution) quadrupole mass spectrometer. This is accomplished by means of two non-evaporable getter (NEG) pumps, the first one operating at high temperature (300 . 450 IC) and the second one at room temperature, which effectively and quickly remove to a high degree all active components in the original gas mixture, with particular regard to hydrogen isotopes. Obviously, noble gases are preserved. The results of extensive tests carried out with such a facility are reported. A high-resolution quadrupole mass spectrometer was used during tests with 4He-D2 mixtures, just to provide evidence for the absence of deuterium in the final gaseous mixture. The minimum detectable peak ratio 4He/D2 has been found to be less than 10-6.

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Section: State Of the Artmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A powerful tool to quantitatively detect tiny amounts of 4He in a deuterium rich background for fusion research

Frattolillo

Ninno

2007

2007 IEEE 22nd Symposium on Fusion Engineering

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“…Consequently, the light is to be focused by condenser lens. (6) The currents of PMT are converted to voltage signal by I/V unit. (7) At last with the assistance of computer and calibration formulas the pressure of helium and deuterium could be generated by the voltage signals of He-I and D-α.…”

Section: System Setupmentioning

confidence: 99%

“…The main reason is that both the measured gas helium and the working gas deuterium have almost the same atomic mass [m ( 4 He)=4.003 amu, m(D 2 )=4.028 amu]. Omegatrons is one kind of particular design analyzer to overcome this difficulty [6]. However, it could not be applied in EAST, because it is quite sensitive to magnetic field turbulence, and it works only below 10 −4 Pa, last but not the least, the time resolution is as low as about 60 s [7].…”

Section: Introductionmentioning

confidence: 99%

Higher resolution helium measuring system for deuterium plasma on EAST tokamak via normal Penning gauge

Wang¹,

Hu²,

Yu³

et al. 2016

Plasma Sci. Technol.

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Although the deuterium and helium have almost the same mass, a Penning Optical Gas Analyzer (POGA) system on the basis of the spectroscopic method and Penning discharging has been designed on EAST, since 2014. The POGA system was developed successfully in 2015, it was the first time that EAST could detect helium partial pressure in deuterium plasma (wall conditioning and plasma operation scenario). With dedicated calibration and proper adjustment of the parameters, the minimum concentration of helium in deuterium gas can be measured as about 0.5% instead of 1% on the other tokamak devices. Moreover, the He and D 2 partial pressures are measured simultaneously. At present, the measurable range of deuterium partial pressure is 1×10 −7 mbar to 1×10 −5 mbar, meanwhile the range of helium is 1×10 −8 mbar to 1×10 −5 mbar. The measurable range can be modified by means of the adjustment of POGA system's parameters. It is possible to detect the interesting part of the gas with a time resolution of less than 5 ms (the 200 ms because of conductance of transfer pipe at present). The POGA system was routinely employed to wall conditioning and helium enrichment investigation in 2015. Last but not the least, the low temperature plasma of POGA is generated by normal penning gauge Pfeiffer IKR gauge instead of Alcatel CF2P, which has been suspended for a few years and was used for almost all the POGA systems in the world.

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“…However, the deuterium and tritium in trimers can be taken into account if the ratio of atomic, molecular, associated, and trimer peaks of protium, deuterium, and tritium is studied when calibrating an apparatus using standard mixtures. The ratios of trimer and molecular mass lines for protium or deuterium range from 2·10 -5 [7] to 1·10 -3 [8,9], and the ratios of the atomic and molecular peaks in the mass spectra of gas mixtures containing hydrogen isotopes are 0.01-0.03 and depend on the measurement conditions, specifically, the energies of the ionizing electrons, the degree of cleaning and flushing of the mass analyzer, heating, evacuation, and so forth [3,7,8].…”

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confidence: 99%

Resolution and calibration requirements for a time-of-flight mass spectrometer for analyzing gaseous fuel mixtures of a thermonuclear reactor

Aruev

Pilyugin

Kozlovskiĭ³

et al. 2008

At Energy

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It is shown that to a large extent the isotopic and chemical analysis of gas mixtures can be performed using a time-of-flight mass spectrometer (mass reflectron), operating in a mode of synchronous detection to eliminate or substantially reduce the background current due to the beta decay of tritium nuclei. To this end, a mass reflectron with resolution ~600 at 10% height of the peak near 3-4 amu has been developed and built and is now under investigation. Such resolution makes it possible to calibrate instruments by using special gas mixtures, study the relations of the atomic, molecular, associated, and trimer peaks of hydrogen isotopes under different conditions, and on this basis to develop a method for calculating the composition of real fuel mixtures from the experimental mass spectra. The apparatus also permits determining the composition of impurities over a wide range of their concentration in the entire mass range to a high degree of accuracy.Continual chemical and isotopic analysis of a deuterium-tritium or a deuterium-helium mixture and the impurities present in such a mixture is necessary for developing thermonuclear reactors and, specifically, the ITER. The most universal, accurate, and reliable existing method for analyzing gas mixtures is mass spectrometry.As Fig. 1 shows, to separate completely the multiplets of ions with the same mass-to-charge ratio M/q the resolving power of a mass spectrometer must be approximately 3·10 3 . In this case, the doublet 3 He + -3 T + will not be resolved, since the resolving power required to do so is ~1.5·10 5 [1]. The impurities in a fuel mixture are protium, 4 He, oxygen, oxides of various elements, nitrogen and its derivatives, hydrocarbons, neon, argon, and others. Since the purity concentration can range from 10 -3 % to several percent, the sensitivity of mass spectrometers must also be high.The use of mass spectrometry for the analysis of gas mixtures containing radioactive tritium is complicated by the fact that the β electrons which are formed when the tritium nuclei on all surfaces in the detector zone decay can increase many-fold the background currents of the detecting systems, which include VÉU-1, -2, and -6 secondary-electron multipliers or multichannel plates [2]. The background current permits detecting only the main components of the gas mixture but not trace impurities. The detector in the MI-3305 static magnetic apparatus [3,4], specially developed for analyzing tritiumcontaining gas mixtures, and its modifications MI-1201 is a Faraday cylinder, which cannot detect trace impurities. In the

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Application of an omegatron type high resolution mass spectrometer for the analysis of mixtures of hydrogen and helium isotopes

Cited by 21 publications

References 8 publications

A powerful tool to quantitatively detect tiny amounts of 4He in a deuterium rich background for fusion research

A powerful tool to quantitatively detect tiny amounts of 4He in a deuterium rich background for fusion research

Higher resolution helium measuring system for deuterium plasma on EAST tokamak via normal Penning gauge

Resolution and calibration requirements for a time-of-flight mass spectrometer for analyzing gaseous fuel mixtures of a thermonuclear reactor

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