James L. Turner

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PEP-II is an e + e-B-Factory Collider located at SLAC operating at the Upsilon 4S resonance (3.1 GeV x 9 GeV). PEP-II has delivered, over the past five years, an integrated luminosity to the BaBar detector of about 240 fb-1 and has reached a luminosity of 9.21x10 33 /cm 2 /s. Steady progress is being made in reaching higher luminosity. The goal over the(More)
The beam diagnostics in the linac for the Linac Coherent Light Source (LCLS) X-ray FEL project at SLAC includes optical transition radiation (OTR) screens for measurements of transverse and longitudinal beam properties. We report on observations of coherent light emission from the OTR screens (COTR) at visible wavelengths from the uncompressed and(More)
We measured the lengths of colliding e+e – bunches in the PEP-II B Factory at SLAC using various techniques. First, at several RF voltages and with both single-bunch and multibunch beams, a synchroscan streak camera measured synchrotron emission through a narrow blue filter. With 3.8 MV of RF, the length of a single positron bunch was 12 mm at low current,(More)
The PEP-II B-Factory at SLAC has recently experienced unexpected beam losses due to anomalously high radiation levels seen in the BaBar detector. The problem was traced to the occurrence of very high (>100 nTorr) pressure spikes that had a very short duration (a few seconds). We describe the events, show analysis predicting where in the vacuum system the(More)
A high-gradient-doping technique is applied to strained polarized photocathodes. A 5.0–7:5 nm p-type surface layer doped to 5 Â 10 19 cm À3 is found sufficient to overcome the surface charge limit while maintaining high beam polarization. This technique can be employed to meet the charge requirements of the Next Linear Collider with a polarization(More)
The X-ray free-electron laser has opened a new era for photon science, improving the X-ray brightness by ten orders of magnitude over previously available sources. Similar to an optical laser, the spectral and temporal structure of the radiation pulses can be tailored to the specific needs of many experiments by accurately manipulating the lasing medium,(More)
The Linac Coherent Light Source (LCLS) is a SASE x-ray Free-Electron Laser (FEL) project presently under construction at SLAC [1]. The injector section, from drive laser and RF photocathode gun through first bunch compressor chicane, was installed in fall 2006. Initial system commissioning with an electron beam was completed in August 2007, with the goal of(More)