ORNL, Oak Ridge, Tennessee
Solid-state based high-power modulators utilize new technology, yet must meet the operational needs of a high reliability facility. This modulator technology is in use at SNS, and is under consideration and development for future machines, such as the ILC and PEFP. Through operational experience and a sustained development effort, a number of improvements have been deployed in the SNS modulator system to meet the high availability demands of operating facilities. The operating experience and development effort of the world-wide community will also be reviewed.
ORNL, Oak Ridge, Tennessee
Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy
The Spallation Neutron Source (SNS) is a second generation pulsed-neutron source and designed to provide a 1-GeV, 1.44-MW proton beam to a mercury target for neutron production. Since the initial commissioning of accelerator complex in 2006, the SNS has begun neutron production operation and beam power ramp-up has been in progress toward the design goal. Since the design beam power is almost an order of magnitude higher compared to existing neutron facilities, all subsystems of the SNS were designed and developed for substantial improvements compared to existing accelerators and some subsystems are first of a kind. Many performance and reliability aspects were unknown and unpredictable, for which it takes time to understand the systems as a whole and/or needs additional performance improvements. A power ramp-up plan has been revised based on the operation experiences and understandings of limits and limiting conditions through extensive studies with an emphasis on machine availability. In this paper the operational experiences of SNS Superconducting Linac (SCL), the power ramp-up status and plans will be presented including related subsystem issues.
SLAC, Menlo Park, California
ORNL, Oak Ridge, Tennessee
Funding: Work supported by the Department of Energy under contract No. DE-AC02-76SF00515.
The 1-MW High Voltage Converter Modulators* have operated in excess of 250,000 hours at the Spallation Neutron Source. Increased demands on the accelerator performance require increased modulator reliability. An effort is underway at SLAC National Accelerator Laboratory to redesign the modulator H-bridge switch plate with the goals of increasing reliability and performance**. The major difference between the SLAC design and the existing design is the use of press-pack IGBTs. Compared to other packaging options, these IGBTs have been shown to have increased performance in pulsed-power applications, have increased cooling capability, and do not fragment and disassemble during a fault event. An overview of the SLAC switch plate redesign is presented. Design steps including electrical modeling of the modulator and H-bridge, development of an integrated IGBT clamping mechanism, and heat sink performance validation are discussed. Experimental results will be presented comparing electrical performance of the SLAC switch plate to the existing switchplate under normal and fault conditions.
*W. A. Reass, et al., “Design, Status, and First Operations of the Spallation Neutron Source Polyphase
”, PAC, 2003
**M.A. Kemp, et al., “Next Generation IGBT Switch Plate
,” LINAC, 2008.
SLAC, Menlo Park, California
ORNL, Oak Ridge, Tennessee
Funding: Work supported by the Department of Energy under contract No. DE-AC02-76SF00515.
SLAC National Accelerator Laboratory is developing a next generation H-bridge switch plate*, a critical component of the SNS High Voltage Converter Modulators**. As part of that effort, a new IGBT gate driver has been developed. The drivers are an integral part of the switch plate, which are essential to ensuring fault-tolerant, high-performance operation of the modulator. The redesigned drivers improve upon the existing gate drives in several ways. The new gate driver has improved fault detection and suppression capabilities; suppression of shoot-through and over-voltage conditions, monitoring of excess di/dt and Vce,sat, and redundant power isolation are some of the added features. Also, triggering insertion delay is reduced by a factor of four compared to the existing driver. This presentation details the design and performance of the new IGBT gate driver. A detailed schematic and description of the construction are included. Operation of the fast over-current detection circuits, active IGBT over-voltage protection circuit, shoot-through prevention and control power isolation breakdown detection circuit are discussed.
*W. A. Reass, et al., “Design, Status, and First Operations of the Spallation Neutron Source Polyphase
”, PAC, 2003
**M.A. Kemp, et al., “Next Generation IGBT Switch Plate
,” LINAC, 2008.