Related Experiment Video
Updated: Nov 10, 2025

Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses
Published on: July 2, 2012
A 1D Lyman-alpha profile camera for plasma edge neutral studies on the DIII-D tokamak
A M Rosenthal1, J W Hughes1, A Bortolon2
1MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139, USA.
Abstract:
A one dimensional, absolutely calibrated pinhole camera system was installed on the DIII-D tokamak to measure edge Lyman-alpha (Ly-α) emission from hydrogen isotopes, which can be used to infer neutral density and ionization rate profiles. The system is composed of two cameras, each providing a toroidal fan of 20 lines of sight, viewing the plasma edge on the inboard and outboard side of DIII-D. The cameras' views lie in a horizontal plane 77 cm below the midplane. At its tangency radius, each channel provides a radial resolution of ∼2 cm full width at half maximum (FWHM) with a total coverage of 22 cm. Each camera consists of a rectangular pinhole, Ly-α reflective mirror, narrow-band Ly-α transmission filter, and a 20 channel AXUV photodetector. The combined mirror and transmission filter have a FWHM of 5 nm, centered near the Ly-α wavelength of 121.6 nm and is capable of rejecting significant, parasitic carbon-III (C-III) emission from intrinsic plasma impurities. To provide a high spatial resolution measurement in a compact footprint, the camera utilizes advanced engineering and manufacturing techniques including 3D printing, high stability mirror mounts, and a novel alignment procedure. Absolutely calibrated, spatially resolved Ly-α brightness measurements utilize a bright, isolated line with low parasitic surface reflections and enable quantitative comparison to modeling to study divertor neutral leakage, main chamber fueling, and radial particle transport.
More Related Videos
Related Concept Videos
Atomic Emission Spectroscopy: Lab
Inductively Coupled Plasma Atomic Emission Spectroscopy: Instrumentation
There are three main types of inductively coupled plasma atomic emission spectroscopy (ICP-AES) instruments: sequential, simultaneous multichannel, and Fourier transform instruments, with the latter being less commonly used....
Inductively Coupled Plasma–Mass Spectrometry (ICP–MS): Overview
Inductively Coupled Plasma Atomic Emission Spectroscopy: Principle
The ions and electrons produced interact with the fluctuating magnetic field created by a water-cooled...
Atomic Emission Spectroscopy: Instrumentation
Mass Analyzers: Common Types

