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Neutron emission profiles and energy spectra measurements at JET L. Giacomelli 1, 2, S. Neutron emission profiles and energy spectra measurements at JET L. Giacomelli 1, 2, S. Conroy 1, 3, F. Belli 4, G. Gorini 2, 5, L. Horton 1, E. Joffrin 1, E. Lerche 1, A. Murari 1, S. Popovichev 1, M. Riva 4, B. Syme 1 and JET EFDA Contributors* JET-EFDA, Culham Science Centre, Abingdon, OX 14 3 DB, UK Department of Physics, Università degli Studi di Milano-Bicocca, Milano, Italy Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden 4 Associazione EURATOM-ENEA sulla Fusione, Roma, Italy 5 Istituto di Fisica del Plasma "Piero Caldirola“, Milan, Italy See the Appendix of F. Romanelli et al. , Proceedings of the 24 th IAEA Fusion Energy Conference 2012, San Diego, USA 1 2 JET shot 84747 3 Abstract The Joint European Torus (JET, Culham, UK) is the largest tokamak in the world. It is devoted to nuclear fusion experiments of magnetic confined Deuterium (D)/Deuterium-Tritium (DT) plasmas. JET has been upgraded over the years and recently it has also become a test facility of the components designed for ITER, the next step fusion machine under construction in Cadarache (France). JET makes use of many different diagnostics to measure the physical quantities of interest in plasma experiments. Concerning D/DT plasmas neutron production, various types of detectors are implemented to provide information upon the total neutron yield, the neutron emission profile and energy spectrum. The total neutron yield is measured by six fission chambers located around the tokamak. Three of them dedicated to D plasma experiments have been recently calibrated during JET shutdown using a high activity Californium source. The neutron emission profile emitted from plasma poloidal section is reconstructed using the neutron camera (KN 3). It consists in two sets of detectors, 10 with horizontal and 9 with vertical radial lines of sight, based on organic liquid scintillating material. In 2010 KN 3 was equipped with a new digital data acquisition system capable of high rate neutron measurements (<0. 5 MCps). A similar instrument will be implemented on ITER and it is currently in its design phase. Various types of neutron spectrometers with different view lines are also operational on JET. One of them is a new compact spectrometer (KM 12) based on organic liquid scintillating material which was installed in 2010 and implements a similar digital data acquisition system as for KN 3. This article illustrates the measurement results of KN 3 neutron emission profiles and KM 12 neutron energy spectra from the latest JET D experimental campaign C 31. KN 3 H phs Auxiliary power Total neutron rate KN 3 profile of detected events KN 3 H count rate Neutron diagnostics KM 12 neutron phs KN 3 V count rate KN 3 KM 12 count rate Ref. [2] Ref. [1] KM 12 Teff ~ 17 ke. V Ref. s[8, 9] JET shot 84806 NEW DAQ Ref. [3] 14 bit; 0. 2 GSample/s Ref. [4] Data analysis method (Short / Long)|Energy Double Rayleigh function fit and Cash statistics minimization Measured digital pulse shapes Short Long KN 3 H phs KN 3 V phs Auxiliary power Total neutron rate Ref. [5] KN 3 V phs KN 3 profile of detected events separatrix KN 3 H count rate Tomographic analysis of Short / Long vs. Energy distribution separatrix Ref. s[6, 7] Conclusions The tomographic analysis of the Short/Long vs. Energy distribution based on the minimization of a double Rayleigh function fit with Cash statistics allow for detailed identification of neutron and gamma events. From this analysis, the measured neutron and gamma pulse height spectra ( phs) are determined such that: 1) the plasma emission neutron and gamma profiles can be obtained from KN 3 measurements; 2) information upon the plasma emission neutron energies, the effective plasma temperature Teff and the gamma background can be obtained from KM 12 measurements. Outlook Determination of KN 3 NE 213 detectors efficiencies and attenuation coefficients. Investigation on analysis methods to extract more information on the neutron energy spectra obtained from KM 12 data. Possible implementation of an LED control and monitoring system for KN 3 NE 213 scintillator detectors to compensate for possible photomultiplier gain drifts induced by count rate variations. KN 3 V count rate KM 12 count rate Ref. s[8, 9] Teff ~ 18 ke. V References [1] M. J. Loughlin et al. , Rev. Sci. Instrum. 70 1 (1999) 1123. [2] L. Bertalot et al. , in 32 nd EPS Conference on Plasma Phys. Tarragona, 27 June-1 July 2005, ECA 29 C P-1. 078 (2005). [3] M. Riva et al. , Fusion Engineering and Design 86 (2011) 1191. [4] F. Belli et al. , IEEE TRANSACTIONS ON NUCLEAR SCIENCE 59 5 (2012) 2512. [5] L. Giacomelli et al. , Rev. Sci. Instrum. 82 (2011) 123504. [6] L. Giacomelli et al. , to be submitted to Rev. Sci. Instrum. . [7] W. Cash, The Astrophysical Journal 228 (1979) 939. [8] F. Gagnon-Moisan et al. , 2 nd INTERNATIONAL WORKSHOP ON FAST NEUTRON DETECTORS AND APPLICATIONS, 6 -11 Nov. 2011, EIN GEDI, ISRAEL. [9] M. Reginatto et al. , Nuclear Instruments and Methods A 476, Issues 1 -2(2002) 242 -246. Acknowledgment The authors are grateful to colleagues of ENEA Frascati (Italy) and PTB Braunschweig (Germany) laboratories for the precious work and fruitful collaboration and to D. Simpson, P. Blanchard, M. Beldishevski and P. Heesterman for their support at JET. This work was supported by EURATOM and carried out within the framework of the European Fusion Development Agreement. The views and opinions expressed herein do not necessarily reflect those of the European Commission. 3 rd International Conference Frontiers in Diagnostic Technologies 25 -27 November 2013 Laboratori Nazionali di Frascati (Italy) KM 12 neutron phs