In the present article a new diagnostic device in the soft x-ray range, for magnetic fusion plasmas, is proposed based on a gas electron multiplier detector with 2.5x2.5 cm active area, equipped with a true two-dimensional readout system. The readout printed circuit board, designed for these experiments, has 128 pads. Each pad is 2 mm square and covers a roughly circular area. The operational conditions of the detector are settled to work in the x-ray range 3-15 keV at very high counting rates, with a linear response up to 2 MHz/pixel. This limitation is due to the electronic dead time. Images of a wrench and two pinholes were done at rates of 2.5 MHz/pixel with a powerful x-ray laboratory source showing an excellent imaging capability. Finally preliminary measurements of x-ray emission from a magnetic fusion plasma were performed on the Frascati tokamak upgrade experiment. The system was able to image the plasma with a wide dynamic range (more than a factor of 100), with a sampling frequency of 20 kHz and with counting rates up to 4 MHz/pixel, following the changes of the x-ray plasma emissivity due to additional radio frequency heating. The spatial resolution and imaging properties of this detector have been studied in this work for conditions of high counting rates and high gain, with the detector fully illuminated by very intense x-ray sources (laboratory tube and tokamak plasma). (C) 2001 American Institute of Physics.
Ultrafast soft x-ray two-dimensional plasma imaging system based on gas electron multiplier detector with pixel readout
MASSAI, MARCO MARIA;
2001-01-01
Abstract
In the present article a new diagnostic device in the soft x-ray range, for magnetic fusion plasmas, is proposed based on a gas electron multiplier detector with 2.5x2.5 cm active area, equipped with a true two-dimensional readout system. The readout printed circuit board, designed for these experiments, has 128 pads. Each pad is 2 mm square and covers a roughly circular area. The operational conditions of the detector are settled to work in the x-ray range 3-15 keV at very high counting rates, with a linear response up to 2 MHz/pixel. This limitation is due to the electronic dead time. Images of a wrench and two pinholes were done at rates of 2.5 MHz/pixel with a powerful x-ray laboratory source showing an excellent imaging capability. Finally preliminary measurements of x-ray emission from a magnetic fusion plasma were performed on the Frascati tokamak upgrade experiment. The system was able to image the plasma with a wide dynamic range (more than a factor of 100), with a sampling frequency of 20 kHz and with counting rates up to 4 MHz/pixel, following the changes of the x-ray plasma emissivity due to additional radio frequency heating. The spatial resolution and imaging properties of this detector have been studied in this work for conditions of high counting rates and high gain, with the detector fully illuminated by very intense x-ray sources (laboratory tube and tokamak plasma). (C) 2001 American Institute of Physics.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
