Alternative principle and method in x-ray diagnostics for plasma electron temperatures

Hirata

et al. 2004

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Significant effects of sheared transverse electric fields in plasmas on both turbulent fluctuations and drift waves are experimentally demonstrated with improvement in plasma confinement for the first time in the tandem mirror GAMMA 10. These electric-shear effects are performed on the basis of a factor of 2 advance in ion-confining potential formation. For analyzing these phenomena in detail, we develop a novel electrostatic ion-energy spectrometer array consisting of five spectrometer units. The spectrometer arrays have the characteristic advantage of having no disturbances from potential-producing electron-cyclotron wave heated energetic electrons. Totally four array arms having each a 90°separation located on each GAMMA 10 end wall make it possible to observe two-dimensionally resolved radial-distribution profiles of plug and/or central potentials as well as radially produced shear of electric fields along with the earlier-described fluctuation signals simultaneously.

Section: Effects Of Sheared Transverse Electric Fields In Plasmasmentioning

confidence: 85%

Observations of sheared radial electric-field effects on turbulence suppression

Yoshida

Hirata

et al. 2004

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“…12,13 Its electron yield currents I Au are utilized for monitoring photon flux. A photodiode 14,15 having an 80 Å dead layer ͑IRD XUV300͒ is also employed as another I 0 monitor. The output current from each detector is measured with an electropicoammeter and its output voltage is converted into digital pulses with a voltage-to- ͑b͒ The quantum efficiency of the ULE Ge detector normalized by the incident x-ray energy.…”

Section: Calibration Of An Ultralow-energy Measurable Pure-germamentioning

confidence: 99%

X-ray diagnostics for investigating electron distribution functions in the central cell of the GAMMA 10 tandem mirror

Kohagura

Hirata

et al. 2006

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The quantum efficiency of an ultralow-energy-sensitive pure-Ge ͑ULE Ge͒ detector is investigated using synchrotron radiation from the storage ring at AIST especially for x-ray pulse-height analyses ͑PHAs͒, down to a few hundred eV. Several types of x-ray diagnostics such as x-ray PHA, x-ray absorption methods, and x-ray tomography using the ULE Ge detector, a NaI͑Tl͒ detector, as well as a microchannel-plate tomography system are employed for investigating electron distribution functions and electron temperature profiles with preliminary central electron-cyclotron heating in the central cell of the GAMMA 10 tandem mirror. These measurements play an important role in studying an essential physics scaling of the electron temperature as a function of electron confining potential in tandem mirror plasmas.

“…3(c) trace the experimental data by the use of 17 and 20 m as the detector sensitive length (see our theory in Refs. [11][12][13][14].…”

Section: Characterization Of Newly Developed X-ray Tomography Detmentioning

confidence: 99%

X-ray tomography systems for observations of the effects of radially sheared electric fields on fluctuations in plasmas

Kohagura

Numakura

et al. 2004

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Experimental verification of the effects of radially sheared electric-field (or potential) formation in plasmas is one of the most critical issues to understand the physics basis for plasma confinement improvements. In the GAMMA 10 tandem mirror, recent experimental results show shear formation effects on the suppression of not only coherent drift waves but turbulence-like fluctuations without any coherent phasing relation during the ion-confining potential formation period. Contours of the central-cell soft x-ray brightness show spatially and temporally fluctuated structures during a weak sheared period by the use of the 50 channel microchannel plate system. A new x-ray tomography system is developed for analyzing temporally and spatially resolved plasma behavior in the presence or absence of these shear formation effects in GAMMA 10. The system consists of two 48-channel silicon semiconductor detector arrays with different viewing angles. X-ray energy responses of the new detector arrays along with response uniformity of detector channels have been characterized using synchrotron radiation at the Photon Factory.