446 research outputs found
The Bunch Injection Controller for the PEP-II Storage Rings
The PEP-II storage rings at SLAC each have 3492 'buckets' into which
electrons and positrons can be injected into the high- and low-energy rings.
Equipment to measure the currents of all the individual buckets was originally
provided by the Lawrence Berkeley Laboratory and is implemented in VXI-based
hardware. Data from this equipment as well as high precision direct current
measurement provide the hard data for the Bunch Injection Controller. A large
number of parameters determined by injection design considerations as well as
set by operators for different circumstances are also used by the software
algorithms to determine the desired bucket injection order and charge quantity
for each injection pulse. These requests are then passed on to the venerable
SLAC master pattern generator, which provides beams for other applications as
well. This highly visible and highly successful system is implemented using the
EPICS toolkit, and fits well into the merged SLAC EPICS/SLC control system. The
Bunch Injection Controller hardware is a VME-based EPICS IOC, which makes
extensive use of shared memory for communicating with the VXI measurement
equipment and the SLAC master pattern generator.Comment: 4 page
Ultrafast Raman laser mode-locked by nanotubes
We demonstrate passive mode-locking of a Raman fiber laser using a nanotube-based saturable absorber coupled to a net normal dispersion cavity. This generates highly chirped 500 ps pulses. These are then compressed down to 2 ps , with 1.4 kW peak power, making it a simple wavelength-versatile source for various applications
Prey of reintroduced fishers and their habitat relationships in the Cascades T Range, Washington
Conservation and recovery of forest carnivores requires an understanding of their habitat requirements, as well as requirements of their prey. In much of the western United States, trapping and habitat loss led to extirpations of fishers (Pekania pennanti) by the mid-20th century, and reintroductions are ongoing to restore fishers to portions of their former range. Fisher recovery in Washington State has been limited by isolation from other populations, but other potentially important factors, such as diet of fishers in this region and prey availability, have not been thoroughly investigated. We collected hair samples from potential prey and fishers for stable isotope analysis to identify important prey items for fishers within a reintroduction area in southern Washington. We then estimated the abundance of prey species at 21 sites across a gradient of forest structural classes within the fisher reintroduction area, and assessed the effects of forest age and vegetation on the prey community using permutational multivariate analysis of variance and non-metric multidimensional scaling. Stable isotopes revealed that larger prey items, including snowshoe hares (Lepus americanus) and/or mountain beavers (Aplodontia rufa), were the most important prey item(s) for fishers in the southern Cascades. We found distinct but equally diverse prey communities in old-growth (unmanaged) and young (heavily managed) forest stands, with snowshoe hares and mountain beavers most common in young forests, while chipmunks (Neotamius spp.) and small mammals were more common in older forests. Our results suggest a discrepancy between the habitats where important fisher prey are most abundant and habitat requirements of fishers. Snowshoe hares and mountain beavers were most abundant in young forests, whereas fishers are associated with landscapes dominated by older forest stands or those that provide large woody structures, which fishers use for denning and resting. Our results add to growing evidence that forest landscape mosaics provide valuable habitat for fishers in the Pacific Northwest, suggesting that both mature and younger forest stands are important for fishers and fisher recovery
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