Thermoplastic Modulator Development.
Abstract
An analytical and experimental research effort was performed to investigate the application of an existing breadboard thermoplastic modulator to wideband spectrum analysis by means of real-time optical data processing. The objectives of the research were identification of an approach for increasing the cycling rate of the modulator to 10 frames per second and improvement of the modulator bandwidth to 100 MHz. A computer model was established to predict the transient thermal behavior of the thermoplastic substrate under conditions of continuous rapid cycling. The computer analysis revealed that the key parameters are the thermal conductivity of the substrate, the substrate thickness, and the length of the heat pulses. Based on results of the computer model,the recommended design employs a 6 mm thick sapphire substrate that is heated with 1 msec pulses and that is liquid cooled on the rear surface. The system bandwidth was analyzed in terms of the impulse responses of the subsystems, including the electron beam modulation, the electron beam spot size, and the thermoplastic response. An analysis of the recording duty cycle led to recommended changes to the deflection circuits to increase the recording duty cycle, with a goal of 97%. Modifications to the breadboard thermoplastic modulator included installation of a new input to reduce the impedance mismatch and redesign of the cathode support structure to accommodate new cathodes. Although limited by a 25 micron spot size, thermoplastic recordings were achieved at input frequencies of up to 120 MHz. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1978
- Accession Number
- ADA062660
Entities
People
- C. C. Aleksoff
- I. Cindrich
- W. S. Colburn
Organizations
- Environmental Research Institute of Michigan