A Delay Line Based Time, Position, and Velocity Determination System for a Time of Flight Plasma Spectrometer
Abstract
Time and position sensing are critical measurements for time of flight plasma spectrometers. Integral to this is the velocity determination and therefore the species identification of the incoming ions. An innovative technique based on discrete LC delay line anodes, dramatically simplifies the time and position measurements by keeping the number of preamplifiers / discrim-inators to maximum four independent of the number of positions. Thus all the measurements are reduced to time-only, and they are achieved by the use of the high resolution and low power time of flight (TOF) chip. The delay line anode is highly custom in shape and size a prop-erty that greatly simplifies the application to odd geometries. The Hot Plasma Composition Analyzer (HPCA) on the MMS NASA mission is an instrument that requires time of flight resolutions of ¡250ps at 16 look angles and velocity determination in 512 bins at ion rates up to 2 Meg-cps. Furthermore it employs time of flight path correction with the measurement of 16 stop positions, to improve the separation of H, He+, He++ and O, due to scattering at the foil. The delay line technique well exceeds all the science requirements with 4 preamplifiers and 3 TOF chips compared to a traditional system that would require 34 preamplifier / discriminator chains, combiners, separate time measurement.
- Publication:
-
38th COSPAR Scientific Assembly
- Pub Date:
- 2010
- Bibcode:
- 2010cosp...38.1968P