Synchroscan streak camera imaging at a 15-MeV photoinjector with emittance exchange

At the Fermilab A0 photoinjector facility, bunch-length measurements of the laser micropulse and the e-beam micropulse have been done in the past with a fast single-sweep module of the Hamamatsu C5680 streak camera with an intrinsic shot-to-shot trigger jitter of 10-20ps. We have upgraded the camera system with the synchroscan module tuned to 81.25MHz to provide synchronous summing capability with less than 1.5ps FWHM trigger jitter and a phase-locked delay box to provide phase stability of ~1ps over 10s of minutes. These steps allowed us to measure both the UV laser pulse train at 263nm and the e-beam via optical transition radiation (OTR). Due to the low electron beam energies and OTR signals, we typically summed over 50 micropulses with 0.25-1nC per micropulse. The phase-locked delay box allowed us to assess chromatic temporal effects and instigated another upgrade to an all-mirror input optics barrel. In addition, we added a slow sweep horizontal deflection plug-in unit to provide dual-sweep capability for the streak camera. We report on a series of measurements made during the commissioning of these upgrades including bunch-length and phase effects using the emittance exchange beamline and simultaneous imaging of a UV drive laser component, OTR, and the 800nm diagnostics laser.Comment: 26 p

Single-shot electro-optic sampling of coherent transition radiation at the A0 Photoinjector

Future collider applications and present high-gradient laser plasma wakefield accelerators operating with picosecond bunch durations place a higher demand on the time resolution of bunch distribution diagnostics. This demand has led to significant advancements in the field of electro-optic sampling over the past ten years. These methods allow the probing of diagnostic light such as coherent transition radiation or the bunch wakefields with sub-picosecond time resolution. Potential applications in shot-to-shot, non-interceptive diagnostics continue to be pursued for live beam monitoring of collider and pump-probe experiments. Related to our developing work with electro-optic imaging, we present results on single-shot electro-optic sampling of the coherent transition radiation from bunches generated at the A0 photoinjector.Comment: 3 p

PEANUT QUOTA MARKETS AND PEANUT PRODUCTION AFTER FAIR

The U.S. peanut program has limited peanut production since 1949. Unlike the programs for grains, cotton, and rice, the 1996 FAIR Act left the peanut program largely intact. As before FAIR (and since 1977) the right to grow peanuts for the domestic edible market is embodied in marketing quota, which can be leased and sold. The FAIR Act for the first time allowed quota movement across county lines. We now have four years of experience with peanut quota markets post-FAIR. In some parts of the country, quota has moved as much as the regulatory caps allow. But in most of the traditional peanut-growing areas of the Southeast there has been little cross-county movement. In this paper we analyze a large county-level panel of pre- and post-FAIR data to assess the effects of these changes in policy. We have compiled from USDA-FSA sources data on quota movements for virtually every peanut-producing county in the seven major peanut-producing states. We use these data to test microeconomic predictions of the effects of the loosening of transfer restrictions. Analysis of the data shows large quota movements in areas where observations on additionals production and lease rates would have predicted such. We find that movements in production, as distinct from movements in quota, cannot be explained entirely by FAIR, but can reasonably be attributed to changes in the profitability of growing competing crops such as cotton. The reduced profitability of the latter might itself be attributed in part to the elimination of cotton deficiency payments.Agricultural and Food Policy,

AN EMPIRICAL ANALYSIS OF HONEYBEE POLLINATION MARKETS

Pollination by honeybees plays an important role in modern agriculture. Some crops are greatly dependent on honeybees (almonds, apples, avocados, blueberries, and cherries are examples) while the yields and quality of other crops are significantly enhanced by honeybee pollination. The importance of understanding pollination markets has increased recently due to changes brought on by the twin scourges of Varroa and tracheal mites. Both are infestations of feral and domestic bees that imply greater future reliance on domesticated bees at higher cost. In the United States a complex market has evolved that connects itinerant beekeepers and their bee colonies with farmers who demand their services. While the fields of entomology and crop science have developed a large literature on general principles of beekeeping and its application to particular crops, there has been little economic analysis of pollination markets. In this paper, we begin to remedy this lack of attention by analyzing an extensive panel data set of individual pollination transactions for Oregon beekeepers. The Oregon panel constitutes a considerably larger and richer data set on pollination markets than the data set examined by Cheung (1973), which is our only empirical precedent. Using cross-sectional time series regression models, we find results that are consistent with Cheungs earlier findings on the consistency of pollination market outcomes with economic theory. Fees charged for placing colonies on crops that yield marketable honey are found to be less than for crops that yield no honey income to the beekeeper: the pollination fee for crops that produce honey is about $17 per colony less than for crops that produce no honey. Pollination fees also vary over time in response to changes in both crop prices and honey prices. Because bees are paid according to their value of marginal product in the production of crops, pollination fees should vary positively with crop prices. We find that a ten percent increase in crop prices causes pollination fees to increase by about$.40 per colony. With respect to honey prices, we find that a ten percent increase is estimated to decrease pollination fees by about $2.50 per colony. This estimated effect is a previously unexplored link between the now-defunct honey program and its longstanding public policy rationale, the encouragement of honeybee pollination. Insofar as the honey program successfully maintained the price of honey above levels that would otherwise have been observed, our analysis suggests that elimination of the program has resulted in a reduction in pollination services and an increase in pollination fees.Marketing,

THE END OF SUPPLY CONTROLS: THE ECONOMIC EFFECTS OF RECENT CHANGE IN FEDERAL PEANUT POLICY

The paper analyzes recent changes in U.S. peanut policy as enacted in the 2002 Farm Security Act. A model representing the impact of the 2002 farm bill on the domestic and foreign prices of edible peanuts is constructed and the gains and losses to peanut producing states are measured.Agricultural and Food Policy,

Conversion of a transverse density modulation into a longitudinal phase space modulation using an emittance exchange technique

We report on an experiment to produce a train of sub-picosecond microbunches using a transverse-to-longitudinal emittance exchange technique. The generation of a modulation on the longitudinal phase space is done by converting an initial horizontal modulation produced using a multislits mask. The preliminary experimental data clearly demonstrate the conversion process. To date only the final energy modulation has been measured. However numerical simulations, in qualitative agreement with the measurements, indicate that the conversion process should also introduce a temporal modulation.Comment: 4 pages, 6 figures. Submitted to the proceedings of the Physics and Applications of High-Brightness Electron Beams (HBEB09), Nov. 16-19, 2009, Maui H

Asymptotic analysis of displaced lunar orbits

The design of spacecraft trajectories is a crucial task in space mission design. Solar sail technology appears as a promising form of advanced spacecraft propulsion which can enable exciting new space science mission concepts such as solar system exploration and deep space observation. Although solar sailing has been considered as a practical means of spacecraft propulsion only relatively recently, the fundamental ideas are by no means new (see McInnes1 for a detailed description). A solar sail is propelled by reflecting solar photons and therefore can transform the momentum of the photons into a propulsive force. Solar sails can also be utilised for highly non-Keplerian orbits, such as orbits displaced high above the ecliptic plane (see Waters and McInnes2). Solar sails are especially suited for such non-Keplerian orbits, since they can apply a propulsive force continuously. In such trajectories, a sail can be used as a communication satellite for high latitudes. For example, the orbital plane of the sail can be displaced above the orbital plane of the Earth, so that the sail can stay fixed above the Earth at some distance, if the orbital periods are equal (see Forward3). Orbits around the collinear points of the Earth-Moon system are also of great interest because their unique positions are advantageous for several important applications in space mission design (see e.g. Szebehely4, Roy,5 Vonbun,6 Thurman et al.,7 Gomez et al.8, 9). Several authors have tried to determine more accurate approximations (quasi-Halo orbits) of such equilibrium orbits10. These orbits were first studied by Farquhar11, Farquhar and Kamel10, Breakwell and Brown12, Richardson13, Howell14, 15.If an orbit maintains visibility from Earth, a spacecraft on it (near the L2 point) can be used to provide communications between the equatorial regions of the Earth and the lunar poles. The establishment of a bridge for radio communications is crucial for forthcoming space missions, which plan to use the lunar poles.McInnes16 investigated a new family of displaced solar sail orbits near the Earth-Moon libration points.Displaced orbits have more recently been developed by Ozimek et al.17 using collocation methods. In Baoyin and McInnes18, 19, 20 and McInnes16, 21, the authors describe new orbits which are associated with artificial Lagrange points in the Earth-Sun system. These artificial equilibria have potential applications for future space physics and Earth observation missions. In McInnes and Simmons22, the authors investigate large new families of solar sail orbits, such as Sun-centered halo-type trajectories, with the sail executing a circular orbit of a chosen period above the ecliptic plane. We have recently investigated displaced periodic orbits at linear order in the Earth-Moon restricted three-body system, where the third massless body is a solar sail (see Simo and McInnes23). These highly non-Keplerian orbits are achieved using an extremely small sail acceleration. It was found that for a given displacement distance above/below the Earth-Moon plane it is easier by a factor of order 3.19 to do so at L4=L5 compared to L1=L2 - ie. for a fixed sail acceleration the displacement distance at L4=L5 is greater than that at L1=L2. In addition, displaced L4=L5 orbits are passively stable, making them more forgiving to sail pointing errors than highly unstable orbits at L1=L2.The drawback of the new family of orbits is the increased telecommunications path-length, particularly the Moon-L4 distance compared to the Moon-L2 distance