Bucket shaking stops bunch dancing in Tevatron

Bunches in Tevatron are known to be longitudinally unstable: their collective oscillations, also called "dancing bunches," persist without any signs of decay. Typically, a damper is used to stop these oscillations, but recently, it was theoretically predicted that the oscillations can be stabilized by means of small bucket shaking. Dedicated measurements in Tevatron have shown that this method does stop the dancing.Comment: 3 pp. Particle Accelerator, 24th Conference (PAC'11) 2011. 28 Mar - 1 Apr 2011. New York, US

The FNAL injector upgrade

The present FNAL H- injector has been operational since the 1970s and consists of two magnetron H- sources and two 750 keV Cockcroft-Walton Accelerators. In the upgrade, both slit-type magnetron sources will be replaced with circular aperture sources, and the Cockcroft-Waltons with a 200 MHz RFQ (radio frequency quadrupole). Operational experience at BNL (Brookhaven National Laboratory) has shown that the upgraded source and RFQ will be more reliable, improve beam quality and require less manpower than the present system.Comment: 3 pp. Particle Accelerator, 24th Conference (PAC'11) 2011. 28 Mar - 1 Apr 2011. New York, US

Empirical investigation of relational social capital in a virtual community for website programming

A virtual community of interest has a specific and narrow topic of discussion. Therefore, these communities attract registered members who are focused on knowledge sharing. The current research examines whether network ties, which are an aspect of structural social capital that can be categorized into strong and weak social ties, can provide a non-trivial explanation for members? trust, reciprocity, and identification in a virtual community for website programming interest. This relationship enables us to examine a context in which members share a common goal of resolving programming problems through knowledge sharing in contrast with other community settings where only general topics are discussed (e.g., societal and emotional issues). Data were collected through a survey of a virtual community for website programming composed of 69 members. Affirming conventional perception, results of the study indicate that weak ties affect the level of generalized trust and facilitate group identification. Remarkably, the number of members? strong ties is not significantly related to the degree of their perceived norms regarding generalized reciprocity. Reciprocity refers to a mutual expectation that a benefit granted at present should be repaid in the future. The results suggest two key points. First, even for a virtual community of interest, weak ties overshadow strong ties in explaining the outcome variables. Second, reciprocity is not guaranteed even in a focused form of discussion with a non-social topic that involves specialized knowledge. Therefore, virtual community members should be cautious even if ties are strong. Overall, results imply that virtual community administrators, particularly those who manage specialized communities, should be attentive to the strong and weak ties that exist among the community members

A data acquisition system for longitudinal beam properties in a rapid cycling synchrotron

A longitudinal beam properties, data acquisition system has been commissioned to operate in the Fermilab booster ring. This system captures real time information including beam synchronous phase, bunch length, and coupled bunch instability amplitudes as the beam is accelerated from 400 MeV to 8 GeV in 33 ms. The system uses an off-the-shelf Tektronix oscilloscope running Labview software and a synchronous pulse generator. This paper describes the hardware configuration and the software configuration used to optimize the data processing rate.Comment: 3 pp. Particle Accelerator, 24th Conference (PAC'11) 2011. 28 Mar - 1 Apr 2011. New York, US

The Information Systems Academic Discipline in Singapore

The global downturn in demand for IT skills has not left Singapore unscathed. While the demand for information systems graduates has not been as adversely affected as that for traditional computer science ones, there appears to be a drop in the entry quality of students seeking to do information systems degrees. While there appears to be some turnaround on the horizon, to better prepare for the future it is timely to examine the current state of IS as a discipline in Singapore and understand what might be the driving forces that shape it. Using Whitley\u27s theory of scientific change as a theoretical framework [1984a, 1984b], this case study seeks to explore the degree of professionalization and the maturity of IS as a discipline in Singapore through analysis of data gathered from in-depth interviews and secondary data sources. It is found that of the four constructs proposed by Whitley for determining if a discipline is a mature, distinct scientific one, the IS discipline in Singapore clearly satisfies three: the discipline has a high level of professionalization, strong scientific reputation, and well-established research competence and skills. While the IS researchers agree that the discipline has a common vocabulary with which to communicate with one another, they also agree that it is not unknown to the researchers outside the discipline and thus, in this aspect, the discipline only satisfies part of the fourth construct in Whitley\u27s theory

Tune tracking with a PLL in the Tevatron

The Tevatron tune tracker is based on the idea that the phase of the transverse frequency response of the beam can be measured quickly and accurately enough so that the phase at the betatron tune resonance can be tracked by a phase locked loop (PLL). In this paper, a mathematical model of this idea is discussed and is used as the basis for the realization of the tune tracker hardware. The tune tracker has been successfully tested under different beam conditions and is now operational in the Tevatron

Investigating task coordination in globally dispersed teams:a structural contingency perspective

Task coordination poses significant challenges for globally dispersed teams (GDTs). Although various task coordination mechanisms have been proposed for such teams, there is a lack of systematic examination of the appropriate coordination mechanisms for different teams based on the nature of their task and the context under which they operate. Prior studies on collocated teams suggest matching their levels of task dependence to specific task coordination mechanisms for effective coordination. This research goes beyond the earlier work by also considering additional contextual factors of GDT (i.e., temporal dispersion and time constraints) in deriving their optimal IT-mediated task coordination mechanisms. Adopting the structural contingency theory, we propose optimal IT-mediated task coordination portfolios to fit the different levels of task dependence, temporal dispersion, and perceived time constraint of GDTs. The proposed fit is tested through a survey and profile analysis of 95 globally dispersed software development teams in a large financial organization. We find, as hypothesized, that the extent of fit between the actual IT-mediated task coordination portfolios used by the surveyed teams and their optimal portfolios proposed here is positively related to their task coordination effectiveness that in turn impacts the team's efficiency and effectiveness. The implications for theory and practice are discussed

Chromaticity tracking using a phase modulation technique

In the classical chromaticity measurement technique, chromaticity is measured by measuring the change in betatron tune as the RF frequency is varied. This paper will describe a novel way of measuring chromaticity: we will phase modulate the RF with a known sine wave and then phase demodulate the betatron frequency. The result is a line in Fourier space which corresponds to the frequency of our sine wave modulation. The peak of this sine wave is proportional to chromaticity. For this technique to work, a tune tracker PLL system is required because it supplies the betatron carrier frequency. This method has been tested in the Tevatron and we will show the results here

Chromaticity tracking with a phase modulation/demodulation technique in the Tevatron

The Tevatron chromaticity tracker (CT) has been successfully commissioned and is now operational. The basic idea behind the CT is that when the phase of the Tevatron RF is slowly modulated, the beam momentum is also modulated. This momentum modulation is coupled transversely via chromaticity to manifest as a phase modulation on the betatron tune. And so by phase demodulating the betatron tune, the chromaticity can be recovered. However, for the phase demodulation to be successful, it is critical that the betatron tune be a coherent signal that can be easily picked up by a phase detector. This is easily done because the Tevatron has a phase locked loop based tune tracker which coherently excites the beam at the betatron tune