Numerical Studies on Locally Damped Structures
In the JLC/NLC X-band linear collider, it is essential to reduce the long-range dipole wakefields in the accelerator structure to prevent beam break up (BBU) and emittance degradation. The two methods of reducing the long-range wakefields are detuning and damping. Detuning reduces the wakefields rapidly as the dipole modes de-cohere but, with a finite number of modes, the wakefield will grow again as the modes re-cohere. In contrast, damping suppresses the wakefields at a longer distance. There are two principal damping schemes: synchronous damping using HOM manifolds such as that used in the RDDS1 structure and local damping similar to that used in the CLIC structure. In a locally damped scheme, one can obtain almost any Q value, however, the damping can have significant effects on the accelerating mode. In this paper, we present a medium local-damping scheme where the wakefields are controlled to meet the BBU requirement while minimizing the degradations of the fundamental rf parameters. We will address the load design and pulse heating issues associated with the medium damping scheme.
Progress with the JLC/NLC X-Band Linear Collider Design
An electron/positron linear collider with a center-of-mass energy between 0.5 and 1 TeV would be an important complement to the physics program of the LHC in the next decade. The Next Linear Collider (NLC) is being designed by a US collaboration (FNAL, LBNL, LLNL, and SLAC) which is working closely with the Japanese collaboration that is designing the Japanese Linear Collider (JLC). This paper will discuss the technical difficulties encountered as well as the changes that have been made to the NLC design over the last year. These changes include improvements to the X-band rf system as well as modifications to the beam delivery system. The net effect has been to reduce the length of the collider from about 32 km to 25 km and to reduce the number of klystrons and modulators by a factor of two. Together these lead to significant cost savings.
Snapshots of the Balkans through ethnographic investigation of the linguistic landscape
This paper investigates the linguistic landscape of Dubrovnik and Kotor on the Southeastern Adriatic coast, and Mytilene in the north Aegean attempting a theorization of its findings at the intersection of (socio)linguistics, ethnography, and semiotics, which has gained ground as the platform of choice in linguistic landscape (LL) research. I argue that the influx of both tourists and refugees, despite the obvious differences between the two groups, has had radical consequences for the LL which have so far attracted virtually no attention in the relevant literature. And yet, tourism and the arrival of new populations have considerable and lasting effects on the LL which can only be adequately investigated by systematic ethnographic studies of the semiotic means employed in inscribing it. Nevertheless, ethnography, as a methodological sociolinguistic tool, cannot substitute or supersede cognitive aspects of language. If doing LL research means doing semiotic landscape research, then we also have to consider semiosis and higher-order indexicality qua categorization. I understand ethnographic LL research as contributing to a better comprehension of the dynamic indexical relation between language and physical space (turned into place through human agency). Just as a certain accent and particular morphosyntactic choices may index the place of origin of a speaker, a specific LL may index populations and their socioeconomic relations at a certain historical moment. Focusing on these dynamic indexical relations may have far-reaching consequences for superdiversity as a way of making sense of language-in-society.