Design of luminescent detectors for the TJ-II device

Abstract

We outline designs for several rare-earth-based phosphor powder detector systems for monitoring the broadband VUV plasma radiation in the TJ-II torsatron device. These include a global radiation detector, a detector with temporal and spectral resolution, and a third with radial scanning capabilities. We describe the selection of a phosphor powder for this application having good response from the soft x ray to the VUV, a fast response time, and the capability of operation at high temperatures. In addition, we give details of a method developed in-house for depositing thin uniform layers of powder on glass substrates for use as phosphor screens. Finally, we present some detector test results obtained in the plasma of the TJ-I U torsatron.

Characterization of the response of chromium-doped alumina screens in the vacuum ultraviolet using synchrotron radiation

“…4 This, as well as their immunity to electromagnetic interference and ground loops, as well as their compactness ͑only a thin screen is required͒, make them especially suited for use as broadband radiation detectors in the harsh environments encountered in plasma fusion devices. 5 In previous articles we characterized the response of thin screens of the phosphors Y 3 Al 5 O 12 :Ce and Y 2 O 3 :Eu ͑also known as P-46 and P-22, respectively͒ using synchrotron radiation between 13.8 and 620 eV and the relative response of Al 2 O 3 :Cr and other luminescent materials to broadband vacuum ultraviolet ͑VUV͒ radiation ͑15-80 eV͒ and to hard x rays ͑5-50 keV͒. 6,7 The work was motivated by their application as radiation monitors for the TJ-II fusion plasma stellarator device.…”

Preparation and characterization of pixelated phosphor screens for high-resolution linear imaging in the vacuum ultraviolet and x-ray ranges

“…The sedimentation technique employed for filling the capillaries with phosphor material is the same as that used previously to deposit uniform phosphor layers onto quartz plates. 12 Indeed, similar approaches for depositing phosphor layers by sedimentation are to be found in the literature. 13 Moreover, they are very popular methods that can be performed with limited resources.…”

Conceptual designs of fast-ion loss detectors for the TJ-II stellarator

“…7 Furthermore, by coating this plate prior to sedimentation with a thin layer of aluminum to avoid charge buildup effects, an absolute measure of the total number of ions detected is possible. 3 Another possibility is the use of a planar silicon photodiode.…”