To: File \430tx\newoptic.wpd

From: Jon Hagen

Date: 6-18-02 rev 8-6-02

Subject: Proposed modification to fiber optic control of 430 modulator

Instead of sending identical signals to the Floating Deck and Buffer Deck, we can easily send each deck the signal needed to turn it on. This will simplify the modulator in that the mod anode voltage sample will no longer be needed as an additional input to control the Buffer Deck. In addition, if the fiber to the Buffer Deck is out of order or not firmly plugged in, the modulator will no longer suffer from "shoot through" (both decks coming on simultaneously).

To the external control circuitry, the Floating Deck On command remains the same but the Buffer Deck On command will be derived from the Floating Deck On command as the output of a one-shot, triggered on the fall of the Floating Deck On command. This one-shot output will be Anded with Not Floating Deck On as shoot-through protection in the event that the one-shot becomes erratic. The one-shot will be set at just over the modulator turn-off time, about 2 microseconds. The one-shot now does the job of the mod anode voltage sample, keeping the Buffer Deck off except while actually tail clipping. As an additional precaution to prevent shoot- through, the Buffer Deck On command could be delayed about 1 uS from the Floating Deck On command.

Inside the modulator, the only change is on the fiber optic card in the Buffer Deck. This card will now have exactly the same logic as the card in the Floating Deck. Identical cards would be best, but the more complicated card now in the Buffer Deck could be easily modified by changing a couple of connections.