Abstract:The LCLS hard x-ray Free Electron Laser at SLAC reported first lasing in April of 2009. Since then two successful user runs have been completed at the two soft x-ray stations. The first hard x-ray station has started commissioning in July of 2010. Beam diagnostics play an essential role for tuning the machine and delivering the requested beam properties to the users. An overview of the LCLS photon diagnostics will be presented including some selected commissioning results. Plans for future improvements and upgrades will be briefly discussed.

The Linac Coherent Light Source is an x-ray free-electron laser that recently demonstrated lasing in the 1.5-15 Å wavelength range. We report on luminescence measurements of a molecular nitrogen gas irradiated by ∼2  mJ, 80 fs x-ray pulses at energies of 0.83, 2.7, and 8.3 keV. These results provide a direct test of our current understanding of photoabsorption, electron dynamics, and fluorescence processes for such intense, ultrashort x-ray pulses. At 0.83 keV, the duration of the fluorescence signal depends strongly on space-charge effects. At 8.3 keV, space-charge effects are weak, and the signal duration is determined by the Auger electron dynamics.

Abstructs p~r &wribes the design rmd fabrication of a vacuum pumping syswm for the APWLEDA (Low Energy Demons@ation Accelem@ RFQ (RadioFrequency Quadruple) linac [1]. Resultd from the lost proton beam, gas streamingfrom the LEBT (Low Energy BeamTransport)and out-gassingfrom the surface-s of the RFQ cavity and vacuumplumbing,the total gas load will be on the order of 7.2 x 104 Torr-lkerdsec, consisting mainly of hydrogen. The systemis designed to pump on a continual basis with redundancyto ensure that the minimal "operatingvacuum level" of 1 x 10-6Torr is maintainedeven under abnormal conditions. Details of the design,performance analysis and the preliminarytest results of the cryogenic pumps are presented.

AbsntzctThere are several regions in the PEF-ff B Factory at SLAC that rcquir'c dktributcd pumping to deal with large ptmtc-dmmbedgas loads or to prcduccvery low pressurcs(clO" Torr). These regions include the Low Energy Rkig WL@.r dump chambers, the transitions between the High Energy Ring arcs and straight sections, ml most impmtantl y the Interaction Region. We have designed a compact Non-Evapomble Getter pump using commercial getters that combks high pumping speed and high sorption capacity. We &cribs the design fcatm= of the NEG pumps,~Our t=t results from prototype pumps. In addition, we discuss future variations of this style of NEG pump.

The possibility of increasing the apertures of the LCLS gas attenuator/gas detector system is considered. It is shown that increase of the apertures from 3 to 6 mm, together with 4-fold reduction of the operation pressure does not adversely affect the vacuum conditions upstream or downstream. No change of the pump speed and the lengths of the differential pumping cells is required. One minor modification is the use of 1.5 cm long tubular apertures in the end cells of the differential pumping system. Reduction of the pressure does not affect performance of the gas attenuator/gas detector system at the FEL energies below, roughly, 2 keV. Some minor performance degradation occurs at higher energies.