Recent progress on SLED, the SLAC energy doubler

The recent discovery of psi particles has added further incentive to the search for ways of increasing the beam energy at SLAC. Several schemes for achieving higher energies have been explored in recent years. The system which has become known as SLED (SLAC Energy Doubler) has received ERDA approval for gradual installation, using Accelerator Improvement Funds. As presently conceived, SLED has the advantage that it will not increase the average power consumed by the accelerator, and is therefore compatible with national energy-conservation goals. Peak rf power will be enhanced at the expense of rf pulse length, so that the accelerator will deliver shorter pulses of higher-energy electrons with a duty cycle a factor of ten lower than at present. The system is described, and it is shown that SLED raises the accelerator peak energy by 40 percent if the present 2.7 μs rf pulse length is used. The energy increase is 80 percent if the pulse length is extended to 5 μs. Performance at both pulse lengths is discussed. (auth)