Transverse self-fields within an electron bunch moving in an arc of a circle

As a consequence of motions driven by external forces, self-fields (which are different from the static case) originate within an electron bunch. In the case of magnetic external forces acting on an ultrarelativistic beam, the longitudinal self-interactions are responsible for CSR (Coherent Synchrotron Radiation)-related phenomena, which have been studied extensively. On the other hand, transverse self-interactions are present too. At the time being, existing theoretical analysis of transverse self-forces deal with the case of a bunch moving along a circular orbit only, without considering the situation of a bending magnet with a finite length. In this paper we propose an electrodynamical analysis of transverse self-fields which originate, at the position of a test particle, from an ultrarelativistic electron bunch moving in an arc of a circle. The problem will be first addressed within a two-particle system. We then extend our consideration to a line bunch with a stepped density distribution, a situation which can be easily generalized to the case of an arbitrary density distribution. Our approach turns out to be also useful in order to get a better insight in the physics involved in the case of simple circular motion and in order to address the well known issue of the partial compensation of transverse self-force.Comment: 23 pages, 14 figure

Genecology of Thurber's Needlegrass (Achnatherum thurberianum [Piper] Barkworth) in the Western United States

Thurber's needlegrass (Achnatherum thurberianum [Piper] Barkworth) is a key restoration species in the Great Basin and surrounding areas, yet comprehensive studies of how climate relates to genetic variation and seed zones for restoration projects are lacking. Potentially adaptive phenotypic traits of 66 diverse populations of Thurber's needlegrass were measured in common gardens at Central Ferry, Washington and Reno, Nevada in 2012 and 2013. Extensive genetic variation was observed among phenology, morphology, and production traits (P < 0.01), and canonical correlation was used to relate traits to source climate variables. Only with the first two canonical variates were F values significant (P < 0.05), explaining 42% and 18% of the variation, respectively. For variates 1 and 2, strong canonical correlations of 0.97 and 0.94 linked genetic variationwith source climates, providing evidence for climate-driven evolution. Pearson linear correlations indicated that populations from warmer, drier locations generally had earlier blooming and longer awns than those from cooler, wetter locations. Plants from warmer, drier locations also had higher survival at Central Ferry and higher leaf length to width (narrower leaves) at Reno in 2012. Regression of the canonical variates 1 and 2 for traits with source climate variables produced very strongmodels, explaining 94% and 87% of the variation in plant traits. Thesemodelswere used to map 12 seed zones encompassing 465 079 km2 in the Great Basin and surrounding areas with six seed zones representing 90% of the mapped area. We recommend using these seed zones to guide restoration of Thurber's needlegrass. © Published by Elsevier Inc. on behalf of The Society for Range Management.The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information

CLARA conceptual design report

This report describes the conceptual design of a proposed free electron laser test facility called CLARA that will be a major upgrade to the existing VELA accelerator test facility at Daresbury Laboratory in the UK. CLARA will be able to test a number of new free electron laser schemes that have been proposed but require a proof of principle experiment to confirm that they perform as predicted. The primary focus of CLARA will be on ultra short photon pulse generation which will take free electron lasers into a whole new regime, enabling a new area of photon science to emerge

Genecology of Thurber’s Needlegrass ( Achnatherum thurberianum [Piper] Barkworth) in the Western United States

Thurber's needlegrass (Achnatherum thurberianum [Piper] Barkworth) is a key restoration species in the Great Basin and surrounding areas, yet comprehensive studies of how climate relates to genetic variation and seed zones for restoration projects are lacking. Potentially adaptive phenotypic traits of 66 diverse populations of Thurber's needlegrass were measured in common gardens at Central Ferry, Washington and Reno, Nevada in 2012 and 2013. Extensive genetic variation was observed among phenology, morphology, and production traits (P < 0.01), and canonical correlation was used to relate traits to source climate variables. Only with the first two canonical variates were F values significant (P < 0.05), explaining 42% and 18% of the variation, respectively. For variates 1 and 2, strong canonical correlations of 0.97 and 0.94 linked genetic variationwith source climates, providing evidence for climate-driven evolution. Pearson linear correlations indicated that populations from warmer, drier locations generally had earlier blooming and longer awns than those from cooler, wetter locations. Plants from warmer, drier locations also had higher survival at Central Ferry and higher leaf length to width (narrower leaves) at Reno in 2012. Regression of the canonical variates 1 and 2 for traits with source climate variables produced very strongmodels, explaining 94% and 87% of the variation in plant traits. Thesemodelswere used to map 12 seed zones encompassing 465 079 km2 in the Great Basin and surrounding areas with six seed zones representing 90% of the mapped area. We recommend using these seed zones to guide restoration of Thurber's needlegrass. © Published by Elsevier Inc. on behalf of The Society for Range Management.The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information