• D.J. Solley, D.E. Anderson, M. Wezensky
  ORNL, Oak Ridge, Tennessee
• C. Burkhart, M.A. Kemp, M.N. Nguyen
  SLAC, Menlo Park, California

The SNS at ORNL has been operational since 2006, during which time beam power to target has been ramping. As of September 2009, a sustainable 1 MW was achieved, continuing to make SNS the highest energy pulsed neutron source available for scientific research worldwide. Having achieved the design energy, the shift in focus is now towards increasing the availability for researchers using the facility. For example, a 25,000 hour MTBF together with a four hour MTTR goal for the High Voltage Converter Modulators (HVCMs) translates into a 99.98% availability figure. This ambitious goal requires careful engineering of system components, the ability to actively monitor and respond to fault conditions and employment of redundancy wherever possible. This paper outlines the features of the latest IGBT gate drivers that switch the 1200 A, 3300/4500V IGBT modules used in the modulator. The paper goes on to discuss how the signals monitored within each driver can be processed by a central controller to optimize and protect the power stage in a particularly hostile environment. Examples of how the new drivers can improve system availability and improve fault response will also be reported

• M.A. Kemp, A.L. Benwell, C. Burkhart, R.S. Larsen, D.J. MacNair, M.N. Nguyen, J.J. Olsen
  SLAC, Menlo Park, California

The SLAC National Accelerator Laboratory is leading an effort to design a prototype Marx modulator to meet the ILC klystron modulator specifications; a 120 kV (± 0.5%), 140A, 1.6 ms pulse at a 5 Hz prf. A first generation prototype, the P1 Marx, has been developed and is undergoing life testing*. The design of a second-generation Marx, P2, has been completed and most sub-systems have been tested**. The P2 advances the Marx topology demonstrated by the P1; eliminating single-point failures, incorporating advanced diagnostics/prognostics, and optimizing engineering margins to improve system availability. The P2 consists of 32 cells, which are individually regulated at an output of up to 4kV. This is in contrast to the P1 Marx which is collectively regulated by a series "Vernier" Marx. The 30 of 32 cell redundancy allows for up to two cell failures without degrading the modulator output. Failed cells can be quickly replaced and remotely-serviced. This paper presents the design of the P2 Marx. Specific topics discussed include the control architecture, mechanical layout, and power electronics design. Experimental results of both a single and array of cells are presented.

* C. Burkhart, et al., "ILC Marx modulator development status," LINAC, 2008.
** K. Macken, et al., "Towards a PEBB-Based Design Approach for a Marx-Topology ILC Klystron Modulator," PAC, 2009.