High spectral resolution, photon counting detector for Doppler temperature measurements in magnetically confined plasmas
This paper describes the design, construction, and performance of a single-stage microchannel-plate image intensifier used as a photon counting detector over the wavelength range from 1150 to --2000 A. The intensifer incorporates three high strip current (--300 ..mu..A) microchannel plates, constructed with 12-..mu..-diam channels and 15-..mu.. center--center spacing, in a ''Z'' configuration. The use of high strip current MCPs requires gating the power supply to protect the plates from thermal runaway of the strip current. The output pulses are proximity focused onto a P-46 phosphor screen, which is fiber-optically coupled to a linear, self-scanning photodiode array. Maximum frame rates for the photodiode array are -- 125,000 frames/s, with maximum count rates of --25 000 photoevents/s. The detector was placed at the focal plane of a 1-m focal length Ebert--Fastie spectrometer and the performance characteristics of the spectrometer-detector system were evaluated using a hollow cathode Pt lamp. The linewidths measured during this evaluation demonstrate that the spatial resolution of the detector is better than 50 ..mu... The spectrometer-detector system was then used to determine ion temperatures from Doppler broadened impurity lines emitted from plasmas of the Alcator C tokamak. This detector demonstrated more than an order of magnitude increase in sensitivity compared to a photon-counting photomultiplier tube with a vibrating mirror previously used for these measurements with the same spectrometer.
- Research Organization:
- Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218
- OSTI ID:
- 6651479
- Journal Information:
- Rev. Sci. Instrum.; (United States), Vol. 58:4
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
47 OTHER INSTRUMENTATION
ALCATOR DEVICE
PLASMA DIAGNOSTICS
PHOTODETECTORS
DESIGN
OPERATION
OPTICAL SPECTROMETERS
COUNTING RATES
COUNTING TECHNIQUES
DOPPLER EFFECT
FABRICATION
IMAGE INTENSIFIERS
MICROCHANNEL ELECTRON MULTIPLIERS
PLASMA CONFINEMENT
CLOSED PLASMA DEVICES
CONFINEMENT
ELECTRON MULTIPLIERS
ELECTRON TUBES
MEASURING INSTRUMENTS
SPECTROMETERS
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
700102* - Fusion Energy- Plasma Research- Diagnostics
440300 - Miscellaneous Instruments- (-1989)