A. KRASNYKH (SLAC)
Major changes to the Next Linear Collider (NLC) design were facilitated by the experimental testing of the 75 MW PPM X-band klystron (XP1) at a 3.05 microsecond pulse width and new component development allowing the DLDS system to operate with eight bins instead of four. This change has a direct effect on the design of the klystron modulator. The conventional base line modulator with two klystrons, a Hybrid version of the baseline with a solid state ON/OFF switch, a solid state induction type modulator that drives eight klystrons, and a solid state direct switch modulator are the general concepts that are being studied intensively. Some form of pulse transformer is the matching element between the klystron beam and the energy storage in the all of the concepts except the direct switch. The volume and cost of this large magnetic element is proportional to the peak pulse power and pulse width of the output. The recent change in the NLC design could require the pulse transformer to double its effective core area increasing both size and cost. In the direct switch model there is no pulse transformer and the klystron beam potential is practically equal to the potential of the energy storage element. Here the solid state switch blocks the 500 kV DC voltage of the storage element during the interpulse period. These design approaches are briefly discussed, specifically the implication of the wider double energy klystron pulse. A new transformerless modulator concept is presented based upon a Marx method of voltage multiplication using ON/OFF IGBTms instead of spark gaps. This approach has similar advantages to the direct switch except the DC Power Supply can be at a much lower voltage. The preliminary experimental results of a traveling wave tube pulse modulator using this approach are described. A 10 cell modulator produces an effective pulse flatness of 0.05% at a 10 kV output level with a 1kV DC supply. Current component analysis and development for a solid state Marx type modulator to power the NLC klystrons (X,S, C-bands) are discussed .
* Work supported by Department of Energy contract DE-AC03-76SF00515
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