The use of magnetic pulse compression circuits (magnetic modulators) to create high voltage, high current, short duration electrical pulses has been well described (see for example W. S. Melville, "The use of Saturable Reactors as Discharge Devices for Pulse Generators," Radio Section, Paper No. 1034, pp. 185-207, Sep. 15, 1950). Particularly, magnetic modulators have been applied advantageously to drive pulsed gas discharges for excimer lasers and other pulsed gas discharge lasers (see for example Ball et al. U.S. Pat. No. 5,177,754, Jan. 5, 1993.
Pulse propagation delay in a magnetic modulator depends upon the characteristic volt-second product(s) required to saturate the core(s) of the individual magnetic switch element(s). Since the volt-second product is nearly invariant for any individual core, operation at different voltage levels typically results in different pulse propagation or throughput delays relative to a trigger signal from master trigger (a shorter delay at higher voltages and a longer delay at lower voltages). However, in some applications, it is important to maintain a constant propagation delay, regardless of variable operating voltage levels, such that measurement events can be timed relative to a trigger signal from the master trigger. Jitter or variation in timing of the output pulse relative to th e trigger signal from the master trigger can also be important in these applications. Additionally, temperature fluctuations can lead to variations in propagation delay and/or jitter in timing of pulses.
Although circuit have been used previously to control pulse propagation delay and jitter in magnetic modulators, they have typically been complex, inflexible, and/or relatively crude and inaccurate in the compensation that they allow (see for example Hill et al. AReliable High Repetition Rate Thyratron Grid Driver Used with a Magnetic Modulator,@ 8th IEEE International Pulsed Power Conference, San Diego, Calif., 1991, IEEE Catalog #91CH3052-8).
A voltage timing compensation circuit in the prior art (see for example Cymer ELS5600 Data DOC. ID: ICLACY00.EPS) compensates for the delay variation at different voltages by adding a low level delay to a trigger signal from a master trigger when the magnetic modulator operates at higher voltages.
The prior art voltage timing compensation circuit operates by sampling the voltage of the initial operating stage of a magnetic modulator just prior to master trigger initiation. The sampled voltage is then digitized and used to drive a digital delay generator, which adds to the low level trigger signal a timing delay proportional to the sampled voltage. Thus according to the prior art cited above, delay compensation is linear relative to operating voltage, whereas the actual dependence of pulse propagation delay on voltage is non-linear.
Because the characteristic volt-second product of the magnetic switch element(s) is temperature dependent, some prior art implementations comprise a temperature timing compensation circuit to correct for variations in delay caused by fluctuations in operating temperature relative to a nominal design ambient temperature.
In accordance with certain prior art embodiments, this temperature timing compensation circuit comprises RC components that synthesize the approximate thermal characteristics of the system.
What is needed in the art is a simple, reliable circuit for timing compensation of a magnetic modulator that more accurately compensates for effects of voltage and/or temperature than does the prior art. Further needed in the art is a circuit for pulse timing control of a magnetic modulator in response to other independent variables, that is simple, accurate, and reliable.