Low-noise, high-speed detector development for optical turbulence fluctuation measurements for NSTX


Schoenbeck N. L. , Ellington S. D. , Fonck R. J. , Jaehnig K., McKee G. R. , Smith D., ...More

REVIEW OF SCIENTIFIC INSTRUMENTS, vol.81, no.10, 2010 (Journal Indexed in SCI) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 81 Issue: 10
  • Publication Date: 2010
  • Doi Number: 10.1063/1.3483196
  • Title of Journal : REVIEW OF SCIENTIFIC INSTRUMENTS

Abstract

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. (C) 2010 American Institute of Physics. [doi:10.1063/1.3483196]