Title :
X/γ-rays detection during streamer development
Author :
Nguyen, C.V. ; van Deursen, A.P.J.
Author_Institution :
Group EPS, Eindhoven Univ. of Technol., Eindhoven
Abstract :
X- or gamma-rays have been produced in the developing discharge of a 2 MV lightning surge generator. The generator provides a voltage waveform with 1.2/50 mus rise/fall time. The waveform is truncated by a spark gap: two sharply pointed electrodes placed horizontally at 0.7 m distance with one electrode grounded. Gap breakdown occurs at about 850 kV. High energies has been recorded with BaF2 and LaBr3(Ce) gamma detectors facing the surge. Aluminum windows limit the detection to gamma´s with energy above 17 keV. The scintillator- photomultiplier combination has been calibrated by the 662 keV line of a 137Cs source; the pulse output rise/fall time is 11/23 ns. With positive surges applied to the floating spark gap electrode, hard radiation is observed in 100% to 60% of the surges depending on the electrode´s distance to the measurement equipments. The radiation occurred in the leading edge, during the streamer development before a conducting channel was formed between the electrodes. The gamma signal consists of several pulses, well resolved in time. Gamma pulses equivalent to 2-3 MeV were detected. From absorption measurements we conclude that these high energy pulses are pile-up of multiple gamma-quanta, each over 100 keV. The pile-up occurs within the rise time of the detector response, 11 ns. The consistent timing with the HV-surge excluded background radiation as a source for these high intensity pulses. For negative discharges three things change: more surges resulted in gamma-pulses, more gamma-pulses per surge, and more gamma energy. Gamma-pulses up to the equivalent of 30 MeV have been recorded. The high equivalent energies are caused by streamers from the measurement cabinet, right in front of the detector. X-ray was also measured from streamer-corona plasma in a wire-plate reactor. No breakdown occurred during the experiment. A high repetition rate 15/25 ns high HV-pulse with 100 ns width was applied to the wire. The volta- - ge pulse´s amplitude was 65 kV with an additional DC offset of +20 kV. Energies equivalent to 45 keV have been recorded.
Keywords :
corona; plasma X-ray sources; plasma diagnostics; spark gaps; X-ray detection; absorption measurements; aluminum windows; conducting channel; electrodes; gamma detectors; gamma-ray detection; gap breakdown; hard radiation; lightning surge generator; scintillator-photomultiplier combination; spark gap; streamer-corona plasma; time 1.2 mus; time 15 ns; time 25 ns; time 50 mus; voltage 2 MV; wire-plate reactor; Electric breakdown; Electrodes; Energy measurement; Gamma ray detection; Gamma ray detectors; Lightning; Plasma measurements; Pulse measurements; Sparks; Surges;
Conference_Titel :
Plasma Science, 2008. ICOPS 2008. IEEE 35th International Conference on
Conference_Location :
Karlsruhe
Print_ISBN :
978-1-4244-1929-6
Electronic_ISBN :
0730-9244
DOI :
10.1109/PLASMA.2008.4591102