High resolution transmission grating spectrometer for edge toroidal rotation measurements of tokamak plasmas

Abstract

We present a high throughput ͑f /3͒ visible ͑3500-7000 Å͒ Doppler spectrometer for toroidal rotation velocity measurements of the Alcator C-Mod tokamak plasma. The spectrometer has a temporal response of 1 ms and a rotation velocity sensitivity of ϳ10 5 cm/ s. This diagnostic will have a tangential view and map out the plasma rotation at several locations along the outer half of the minor radius ͑r / a Ͼ 0.5͒. The plasma rotation will be determined from the Doppler shifted wavelengths of D ␣ and magnetic and electric dipole transitions of highly ionized impurities in the plasma. The fast time resolution and high spectral resolving power are possible due to a 6 in. diam circular transmission grating that is capable of / ⌬ ϳ 15 500 at 5769 Å in conjunction with a 50 µm slit.

Single order x-ray diffraction with binary sinusoidal transmission grating

“…Transmission gratings ͑TGs͒ presently used in soft x-ray spectroscopy, for observing both laboratory-generated and astrophysical plasmas, [1][2][3][4][5][6][7][8][9] are the so-called black-white TGs. 10 They consist of a series of parallel slits on an opaque screen and have a binary transmission function as a square wave, and therefore behave as multiorder diffractors as described by the grating equation.…”

Passive Spectroscopic Diagnostics for Magnetically-confined Fusion Plasmas

“…313 The spectrometer has a temporal response of 1 ms and a rotation velocity sensitivity of ~10 3 m/s. The fast time resolution and high spectral resolution are possible due to a 0.15 m diameter transmission grating that provides a resolving power of λ/Δλ ~ 15,500 at 576.9 nm.…”