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Sökning: WFRF:(Ericsson Göran)

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781.
  • Sjöstrand, Henrik, et al. (författare)
  • Gain stabilization control system of the upgraded magnetic protonrecoil neutron spectrometer at JET
  • 2009
  • Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 80:6, s. 063505-
  • Tidskriftsartikel (refereegranskat)abstract
    • Burning plasma experiments such as ITER and DEMO require diagnostics capable of withstanding the harsh environment generated by the intense neutron flux and to maintain stable operating conditions for times longer than present day systems. For these reasons, advanced control and monitoring (CM) systems will be necessary for the reliable operation of diagnostics. This paper describes the CM system of the upgraded magnetic proton recoil neutron spectrometer installed at the Joint European Torus focusing in particular on a technique for the stabilization of the gain of the photomultipliers coupled to the neutron detectors. The results presented here show that this technique provides good results over long time scales. The technique is of general interest for all diagnostics that employ scintillators coupled to photomultiplier tubes.
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782.
  • Sjöstrand, Henrik, et al. (författare)
  • Gain stabilization control system of the upgraded magneticproton recoil neutron spectrometer at JET
  • 2009
  • Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 80:6, s. 063505-
  • Tidskriftsartikel (refereegranskat)abstract
    • Burning plasma experiments such as ITER and DEMO require diagnostics capable of withstanding the harsh environment generated by the intense neutron flux and to maintain stable operating conditions for times longer than present day systems. For these reasons, advanced control and monitoring (CM) systems will be necessary forthe reliable operation of diagnostics. This paper describes the CM system of theupgraded magnetic proton recoil neutron spectrometer installed at the Joint European Torus focusing in particular on a technique for the stabilization of the gain of thephotomultipliers coupled to the neutron detectors. The results presented here show that this technique provides good results over long time scales. The technique is of general interest for all diagnostics that employ scintillators coupled to photomultiplier tubes.
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783.
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784.
  • Sjöstrand, Henrik, 1978- (författare)
  • Neutron Spectroscopy : Instrumentation and Methods for Fusion Plasmas
  • 2008
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • When the heavy hydrogen isotopes deuterium (D) and tritium (T) undergo nuclear fusion large amounts of energy are released. At the Joint European Torus (JET) research is performed on how to harvest this energy. Two of the most important fusion reactions, d+d→3He+n (En = 2.5 MeV) and d+t→4He+n (En = 14 MeV), produce neutrons. This thesis investigates how measurements of these neutrons can provide information on the fusion performance. The Magnetic Proton Recoil (MPR) neutron spectrometer has operated at JET since 1996. The spectrometer was designed to provide measurements on the 14 MeV neutron emission in DT operation, thereby conveying information on the state of the fuel ions. However, a majority of today’s fusion experiments are performed with pure D fuel. Under such conditions, the measurements with the MPR were severely hampered due to interfering background. This prompted an upgrade of the instrument. The upgrade, described in this thesis, included a new focal plane detector, a phoswich scintillator array, and new data acquisition electronics, based on transient recorder cards. This combination allows for pulse shape discrimination techniques to be applied and a signal to background of 5/1 has been achieved in measurements of the 2.5-MeV neutrons in D experiments. The upgrade also includes a new control and monitoring system, which enables the monitoring and correction of gain variations in the spectrometer’s photo multiplier tubes. Such corrections are vital for obtaining good data quality. In addition, this thesis describes a new method for determining the total neutron yield and hence the fusion power by using a MPR spectrometer in combination with a neutron emission profile monitor. The system has been operated at JET both during DT and D experiments. It is found that the systematic uncertainties are considerably lower (≈6 %) than for traditional systems. For a dedicated system designed for the next generation fusion experiments, i.e, ITER, uncertainties of 4 % could be attained. Neutron spectroscopy can also be an important tool for determining the neutron emission from residual tritium in D plasmas. This information is combined with other measurements at JET in order to determine the confinement of the 1 MeV tritons from the d+d→t+p reactions.
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785.
  • Sjöstrand, Henrik, et al. (författare)
  • Triton burn-up neutron emission in JET low current plasmas
  • 2008
  • Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 41:11, s. 115208-
  • Tidskriftsartikel (refereegranskat)abstract
    • The 14 MeV neutron emission from JET deuterium discharges is analysed on the basis of the information on all neutron diagnostics available on JET. This emission is due to the d + t → α + n reaction, mainly, the triton burn-up process, and is used to determine the fast triton confinement. A simplified model for triton burn-up neutron emission has been used and provides an adequate description of the 14 MeV emission. First orbit triton losses are found to amount to 50%, 20% and 10% at Ip = 1 MA, 2 MA and 3 MA, respectively. Neutron emission spectroscopy measurements with the magnetic proton recoil neutron spectrometer have detected a contribution to the 14 MeV emission due to residual tritium. For the selected (low impurity) discharges analysed in this paper 15% of the 14 MeV emission comes from the residual tritium reactions. It is also found that the residual tritium concentration tends to increase with increasing impurity content.
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786.
  • Skiba, Mateusz, 1985-, et al. (författare)
  • A prototype fully digital data acquisition system upgrade for the TOFOR neutron spectrometer at JET
  • 2016
  • Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : ELSEVIER. - 0168-9002 .- 1872-9576. ; 833, s. 94-104
  • Tidskriftsartikel (refereegranskat)abstract
    • A prototype of a fully digital data acquisition system upgrade for the TOFOR time-of-flight fusion neutron spectrometer at JET has been implemented and evaluated. The core of the system, is composed of five fast PXle waveform digitisers (1 GSPS, 12 bits) with large internal fast memory (1 GB). Due to the complexity and high requirements on timing precision of the spectrometer, the design and implementation of such a system poses numerous technical challenges, in particular regarding time alignment and synchronisation of signal paths and digitiser modules. These issues and their solutions, as pertaining to the TOFOR spectrometer, are presented in detail in the present paper. As a final assessment of the ability of the new data acquisition system to reproduce the capabilities of the original TOFOR system, a thorough comparison of results produced using both systems is presented. The comparison with TOFOR has been performed with satisfying results. Two immediate advantages of the new data acquisition system are significantly improved triggering dead time (from about 70 ns to 10 ns) and the ability to adjust the triggering thresholds as needed during the analysis step. The enhanced spectroscopic capabilities of the new data acquisition system will be reported on in future publications.
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787.
  • Skiba, Mateusz, et al. (författare)
  • Fully digital data acquisition system for the neutron time-of-flight spectrometer TOFOR at JET
  • 2012
  • Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 83:10, s. 10D907-
  • Tidskriftsartikel (refereegranskat)abstract
    • A prototype of a fully digital data acquisition system based on 1 Gsps 12 bit digitizers for the TOFOR fusion neutron spectrometer at JET is assessed. The prototype system enables the use of geometry-based background discrimination techniques, which are modeled, evaluated, and compared to experimental data. The experimental results are in line with the models and show a significant improvement in signal-to-background ratio in measured time-of-flight spectrum compared to the existing data acquisition system.
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788.
  • Skiba, Mateusz, et al. (författare)
  • Kinematic background discrimination methods using a fully digital data acquisition system for TOFOR
  • 2016
  • Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : ELSEVIER. - 0168-9002 .- 1872-9576. ; 838, s. 82-88
  • Tidskriftsartikel (refereegranskat)abstract
    • A fully digital, prototype data acquisition system upgrade for the TOFOR neutron time-of-flight neutron spectrometer at the JET experimental fusion reactor in Culham, England, has been constructed. This upgrade, TOFu (Time-of-Flight upgrade), enables digitization of associated time and energy deposition information from the TOFOR scintillator detectors, facilitating discrimination of spectral background due to unrelated neutron events based on kinematic considerations. In this publication, a kinematic background discrimination method is presented using synthetic data and validated with experimental results. It is found that an improvement in signal-to-background ratio of 500% in certain spectral regions is possible with the new DAQ system.
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789.
  • Skiba, Mateusz, 1985- (författare)
  • Making TOFu : Fusion Plasma Neutron Emission Spectrometry with a Fully Digital Data Acquisition System
  • 2016
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • TOFu (Time-Of-Flight upgrade) is a fully digital data acquisition system based on 1 GSPS, 12 bit digitisers for the TOFOR (Time-Of-Flight spectrometer Optimised for Rate) fusion neutron spectrometer at JET. The system has been assessed, developed and subsequently tested during experimental campaigns at JET. A detailed presentation is provided, describing the electronics setup, as well as solutions to challenges related to time-alignment and synchronisation of the signal lines and digitisers.The system enables kinematic discrimination of spectral background, based on associated time and energy measurements. This technique has been tested with synthetic data, evaluated, and compared to experimental results. The kinematic background discrimination method is shown to provide improvements in signal-to-background ratio of up to 500 % in certain spectral regions.TOFOR is optimised for spectrometry of deuterium-deuterium fusion neutron emission at JET. The primary purpose of TOFu is to enable TOFOR to retain these spectrometric capabilities in the presence of a strong background of high-energy deuterium-tritium fusion emission neutrons, in a forthcoming deuterium-tritium fusion plasma campaign at JET. However, the improvement in signal-to-background ratio also allows for detailed studies of low-intensity spectral components, such as the contribution due to neutrons scattering off the internal wall of the JET tokamak before impinging on the TOFOR sight line. Satisfying experimental results pertaining to this aspect of spectral analysis with TOFu data are shown.Finally, a conceptual backscattering time-of-flight spectrometer, based on deuterated scintillator detectors is presented. The backscattering time-of-flight technique is shown to be able to provide high-resolution spectrometric capabilities of deuterium-tritium fusion plasma neutron emission. Studies with synthetic data are used to demonstrate these capabilities and the effects of the developed background discrimination techniques on deuterium-tritium fusion neutron spectra obtained with the instrument.
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790.
  • Sommestad, Teodor, et al. (författare)
  • SCADA System Cyber Security - A Comparison of Standards
  • 2010
  • Ingår i: IEEE PES General Meeting, PES 2010. - 9781424483570 ; , s. 5590215-
  • Konferensbidrag (refereegranskat)abstract
    • Cyber security of Supervisory Control And Data Acquisition (SCADA) systems has become very important. SCADA systems are vital for operation and control of critical infrastructures, such as the electrical power system. Therefore, a number of standards and guidelines have been developed to support electric power utilities in their cyber security efforts. This paper compares different SCADA cyber security standards and guidelines with respect to threats and countermeasures they describe. Also, a comparison with the international standard ISO/IEC 17799 (now ISO/IEC 27002) is made. The method used is based on a comparison of use of certain key issues in the standards, after being grouped into different categories. The occurrences of the key issues are counted and comparisons are made. It is concluded that SCADA specific standards are more focused on technical countermeasures, such as firewalls and intrusion detection, whereas ISO/IEC 17799 is more focused on organizational countermeasures.
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