MHz sample delivery system for a seeded X-ray oscillator

The demonstration of an x-ray laser oscillator (XLO) relies on pumping a gain medium with intense x-ray pulses and generating fresh samples of medium after exposure. Prior attempts to replenish gain medium used liquid jets, but the ultimate velocity was limited. A thin solid target (25µm) can provide order of magnitude more atoms for population inversion than a liquid target and provides more consistency during experimental operations. Solid targets in rotary spindles can move at high rotation speeds for sample replenishment, yet signiSicant engineering is required to meet the requirements of a XLO system. A rapid moving spindle with a copper foil thin disk can attain high tangential speed to provide fresh samples for population inversion in the XLO scheme. At the Linac Coherent Light Source, operations in multi-bunch modalities deliver x-ray pulses separated in time by 35 ns. In order, to guarantee a fresh spot is illuminated on the copper foil, the target should have a tangential speed near 150m/s (corresponding to a 18k rpm for a 150mm disk). This sets the target performance for a rotating spindle for use in an XLO. In Phase I, we developed a physics model of the rotary spindle with copper disk, addressing timing considerations for use in the XLO experiment at the LCLS. The target speciSications were translated to engineering design goals, and a prototype target delivery system was developed. The prototype underwent signiSicant bench tests and was validated up to 20,000 rpm for a sustained period of >2 hours. Subsequent tests pushed the rotation rate to 25,000 rpm, which is far beyond necessary for the XLO demonstration. In Phase II, we will build off the results in Phase I and continue to reSine the design with simulations and conduct bench tests to further validate the design. The comprehensive package will include mechanical design and engineering of the target mounting and retention system, packaging into a testing chamber, and validation tests on the device up to the speciSied velocity. The ancillary work includes development of user-friendly controls and redundant diagnostics (thermocouples, infrared detectors, photodiodes, etc.) for in-situ monitoring of the spindle.