RESUMO
The availability of high-efficiency volume phase holographic (VPH) gratings and intensified CCD (ICCD) cameras have motivated a simplified, compact spectrometer for Thomson scattering detection. Measurements of T(e) < 100 eV are achieved by a 2971 l∕mm VPH grating and measurements T(e) > 100 eV by a 2072 l∕mm VPH grating. The spectrometer uses a fast-gated (~2 ns) ICCD camera for detection. A Gen III image intensifier provides ~45% quantum efficiency in the visible region. The total read noise of the image is reduced by on-chip binning of the CCD to match the 8 spatial channels and the 10 spectral bins on the camera. Three spectrometers provide a minimum of 12 spatial channels and 12 channels for background subtraction.
RESUMO
By exploiting advances in high-energy pulsed lasers, volume phase holographic diffraction gratings, and image intensified CCD cameras, a new Thomson scattering system has been designed to operate from 532 - 592 nm on the Pegasus Toroidal Experiment. The system uses a frequency-doubled, Q-switched Nd:YAG laser operating with an energy of 2 J at 532 nm and a pulse duration of 7 ns FWHM. The beam path is < 7m, the beam diameter remains ≤ 3 mm throughout the plasma, and the beam dump and optical baffling is located in vacuum but can be removed for maintenance by closing a gate valve. A custom lens system collects scattered photons from 15 cm < R(maj) < 85 cm at ~F∕6 with 14 mm radial resolution. Initial measurements will be made at 12 spatial locations with 12 simultaneous background measurements at corresponding locations. The estimated signal at the machine-side collection optics is ~3.5 × 10(4) photons for plasma densities of 10(19) m(-3). Typical plasmas measured will range from densities of mid-10(18) to mid-10(19) m(-3) with electron temperatures from 10 to 1000 eV.
RESUMO
A new beam emission spectroscopy (BES) diagnostic is under development. Photon-noise limited measurements of neutral beam emissions are achieved using photoconductive photodiodes with a novel frequency-compensated broadband preamplifier. The new BES system includes a next-generation preamplifier and upgraded optical coupling system. Notable features of the design are surface-mount components, minimized stray capacitance, a wide angular acceptance photodiode, a differential output line driver, reduced input capacitance, doubling of the frequency range, net reduced electronic noise, and elimination of the need for a cryogenic cooling system. The irreducible photon noise dominates the noise up to 800 kHz for a typical input power of 60 nW. This new assembly is being integrated into an upgraded multichannel optical detector assembly for a new BES system on the NSTX experiment.
