SPPS and Multiphoton Processes

The Sub‐Picosecond Photon Source (SPPS), in operation since May 2003, makes x‐ray pulses of 100 fs. Spontaneous radiation originates from a short pulsed electron beam that passes through an undulator at the Stanford Linear Accelerator Center. New techniques characterize the x‐rays, the electrons, and the timing jitter in real time. These results provide a framework for discussion of possible strong field experiments at SPPS and at future fourth‐generation photon sources like the recently funded Linac Coherent Light Source.