Beam halo formation from space-charge dominated beams in uniform focusing channels

In space-charge dominated beams the nonlinear space-charge forces produce a filamentation pattern, which results in a 2-component beam consisting of an inner core and an outer halo. The halo is very prominent in mismatched beams, and the potential for accelerator activation is of concern for a next generation of cw, high-power proton linacs that could be applied for intense neutron generators to process nuclear materials. We present new results about beam halo and the evolution of space-charge dominated beams from multiparticle simulation of initial laminar beams in a uniform linear focusing channel, and from a model consisting of single particle interactions with a uniform-density beam core. We study the energy gain from particle interactions with the space-charge field of the core, and we identify the resonant characteristic of this interaction as the basic cause of the separation of the beam into the two components. We identify three different particle-trajectory types, and we suggest that one of these types may lead to continuous halo growth, even after the halo is removed by collimators

Corporate Diversification and Firm Value: Evidence from Post-1997 Data-super-

In 1997, SFAS 131 established a new segment-reporting standard for US public companies. Using measures of diversification based on the diversity in segment-industry characteristics and controlling for endogeneity of the diversification decision, we document a diversification premium in our post-1997 period. We find significant positive effects of cash flow diversity, leverage diversity and profitability diversity on excess value, consistent with the efficient internal capital market hypothesis. We also find that the size of the diversification premium in the post-1997 data is negatively correlated with the degree of diversification and positively correlated with firm size. In contrast, we find that the pre-1998 data typically generates a diversification discount, but the effect is statistically less significant when endogeneity is controlled for. Thus, the diversification discount documented in earlier studies can be an artifact of the pre-1998 data or a failure to control for endogeneity. Copyright (c) 2009 The Authors. Journal compilation (c) International Review of Finance Ltd. 2009.