Low-cost, remote, bandpass radiometers are a powerful spectroscopic tool used in high temperature plasma physics experiments throughout the world, particularly for fusion energy devices, i.e. those producing high levels of radiation. Examples of the measurements made using these types of radiometers are for: A) Core parameters such as the effective ion charge of the plasma, Z e f f ; B) scrape-off-layer (SOL) plasma temperatures and densities; and C) plasma-wall interaction phenomenon. Over two decades ago, a version of such a radiometer system, the Filterscope, was developed by scientists at ORNL. The Filterscope extends the band-pass radiometer technique to make the instrument extremely modular/expandable, robust, and very-fast (with digitization up to 1 MHz) and has been deployed on fusion devices throughout the world. Additionally, a fast band-pass radiometer has other potential uses beyond fusion plasma diagnosis, e.g. LIDAR, X-ray medical diagnostics, radiation monitoring, and solar radiation measurement. This technical report is intended as a user's guide and a reference manual for the use of the ORNL filterscope system. It gives an overview of the diagnostic philosophy and design as well as details on the implementation and operation of the complete system. vii
A diagnostic system, which has a design goal of high-portability, has been designed at Oak Ridge National Laboratory (ORNL). This project aims at providing measurements of key plasma parameters (ne, Te, ni, Ti) for fusion-relevant devices, utilizing Thomson scattering (TS) and optical emission spectroscopy (OES). The innovative design employs mostly commercial off-the-shelf instrumentation and a traveling team of researchers to conduct measurements at various magnetic-confinement plasma devices. The TS diagnostic uses a Quantel Q-smart 1500 Nd:YAG laser with a 2ω harmonic generator to produce up to 850 mJ of 532 nm laser pulses at 10 Hz. Collection optics placed at the detection port consists of an 11 × 3 optical fiber bundle, where the TS diagnostic uses an 11 × 1 subset array of the fibers, the OES diagnostic uses another 11 fibers, and the remaining fibers are available to the host institution. The detection system is comprised of two separate IsoPlane-320 spectrometers with triple-grating turrets of various line spacing and two PI-MAX 4 intensified CCD detectors, used simultaneously to measure a broad range of ion, impurity, and electron parameters. The self-contained diagnostic package also includes a data processing and storage system. The design and initial implementation of the TS-OES diagnostic system are described. The experiments from the proof-of-principle operation of the portable package on a high density (∼2.5 × 1022 m−3) and low-temperature (∼5 eV) electrothermal arc source at ORNL are also discussed.
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