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Powdery scab of potato caused by Spongospora subterranea is one of the main disease problems in many potato production regions of the world. However, no efficient and economically sound control method is currently available. Host resistance will be a key component of the integrated management of powdery scab, but there are discrepancies in published powdery scab resistance ratings of cultivars between countries. In order to identify the main factors causing such discrepancies, 10 reference cultivars thought to have a range of susceptibility to powdery scab and potato mop-top virus were cropped over 4 years in four to six locations across Europe and disease levels on roots and tubers were assessed using standardized scoring scales. Soil contamination was tested using real-time PCR and ELISA. The cultivars performed as expected according to previous characterization, with one exception. No relationship was found between tuber and root susceptibility. Assessment of powdery scab symptoms 1 month before harvest gave results comparable to those assessed 2 months after harvest. Neither real-time PCR nor ELISA soil test results were closely related to disease index data. The field trial results indicate that different scoring methods are the main factor for the discrepancy in resistance ratings, and that environmental conditions and/or soil inoculum level play a minor role. Furthermore, there was either no difference between the pathogen populations in each location or the resistance of most of the cultivars is polygenic.

MERIT is a proof‐of‐principle experiment which demonstrates the key target concepts for the production of muons required for a muon collider or a neutrino factory. The experiment was run at CERN utilizing 14 and 24 GeV proton beams from the PS. The key elements of the experiment include the impact of the proton beam with a free flowing mercury jet within the confines of a 15‐T solenoid field. Results from the experiment are reported.

MERIT is a proof‐of‐principle experiment of a target station suitable as source for future muon colliders or neutrino factories. When installed at the CERN (European Organization for Nuclear Research) PS (Proton Synchrotron) complex fast‐extracted high‐intensity proton beams intercepted a free mercury jet inside a normal‐conducting, pulsed 15‐T capture solenoid magnet cooled with liquid nitrogen. Up to 25 MJ of Joule heat was dissipated in the magnet during a pulse. The fully automated, remotely controlled cryogenic system of novel design permitted the transfer of nitrogen by the sole means of differential pressures inside the vessels. This fast cycling system permitted several hundred tests in less than three weeks during the 2007 data taking campaign.

Potato mop-top virus (PMTV; genus Pomovirus; family Virgaviridae) is transmitted bythesoil-borneSpongosporasubterraneaf.sp.subterranea,aprotoctistthatcauses powdery scab on potato. PMTV is distributed widely in the potato growing areas in South and North America, Japan and northwestern Europe. This article reviews the current knowledge on detection, distribution and control of PMTV with focus on the Baltic Sea region. Since the 1980s, PMTV has caused great economic losses to potato production in the Nordic countries (Norway, Sweden, Denmark and Finland), but its occurrence in other countries of the Baltic Sea region remained unknown. To fill this knowledge gap, harmonised sampling and virus detection procedures including bioassays and serological and molecular methods were employed by 21 research institutions to detect PMTV in potato tubers and soil samples in 2005‐2008. Potato growing areas were widely contaminated with PMTV in the Nordic countries. Only the main seed potato production area in northern Sweden and the High Grade seed potato production zone in Finland were negative for PMTV. Intensive and

Picosecond laser pulses at a wavelength of 266 nm have been focused onto a solid metal cathode in coincidence with high gradient electric fields to produce high brightness electron beams. At power densities exceeding 109 W/cm2, a solid density plasma is formed and intense bursts of electrons are emitted from the target accompanied by macroscopic surface damage. An inferred ∼1 μC of integrated charge with an average current of ∼20 A is emitted from a radio‐frequency cavity driven at electric field gradients of ∼80 MV/m. In another experiment, where a dc extraction field of ∼6 MV/m is used, we observed an electron charge of ∼0.17 μC. Both results are compared with the Schottky effect and the Fowler–Nordheim field emission. We found that this laser‐induced intense electron emission shares many features with the explosive electron emission processes. No selective wavelength dependence is observed in the production of the intense electron emission in the dc extraction field. The integrated electrons give an ap...

A proof-of-principle experiment to investigate the interaction of a proton beam, high magnetic field, and high-Z target is planned for testing at CERN in 2007. The experiment is a multi-laboratory, international endeavor underwritten by the Muon Collider Collaboration. A free-jet mercury target system that interacts with a high-power (1-MW) proton beam in a high magnetic field (15 T) is being designed. The mercury jet target is configured for insertion into the 15-cm-diameter bore of a high-field solenoid. The target features a hermetically sealed primary-containment volume that is enclosed in a secondary containment to ensure isolation of mercury vapors from the surrounding environment. The jet diameter is 1 cm, and the jet velocity will be up to 20 m/s. An optical diagnostic is incorporated into the target design to permit observation of the dispersal of the mercury as a result of interaction with a 24-GeV proton beam with up to 20 x 1012protons per pulse. The target system also includes titanium alloy beam windows for the primary and secondary containments.

Differential cross-sections are presented for the inclusive production of charged pions in the momentum range 0.1 to 1.2 GeV/c in interactions of 12.3 and 17.5 GeV/c protons with Be, Cu, and Au targets. The measurements were made by Experiment 910 at the Alternating Gradient Synchrotron in Brookhaven National Laboratory. The cross-sections are presented as a function of pion total momentum and production polar angle $\theta$ with respect to the beam.

Ionization cooling is the preferred method for reducing the emittance of muon beams in a muon collider. The method described here uses passive liquid hydrogen absorbers and rf acceleration in an alternating lattice of solenoids. We consider the basic principles of ionization cooling, indicating our reasons for selecting various parameters. Tracking simulations are used to make detailed examinations of effects on the beam, such as transmission losses, transverse cooling, bunch lengthening, and introduction of energy spread. The system reduces the overall 6-dimensional emittance to 44% of its initial value.

The muon collider requires intense, cooled muon bunches to reach the required luminosity. Due to the limited lifetime of the muon, the cooling process must take place very rapidly. Ionization cooling seems to be our only option, given the large emittances of the muon beam from pion decay. However, this ionization cooling method has been found quite difficult to implement in practice. We describe a scheme based on the use of liquid hydrogen absorbers followed by RF cavities ("pillbox" or "open iris" type), embedded in a transport lattice based on high field solenoids. These solenoidal fields are reversed periodically in order to suppress the growth of the canonical angular momentum. This channel has been simulated in detail with independent codes, featuring conventional tracking in e.m. fields and detailed simulation of multiple scattering and straggling in the the absorbers and windows. These calculations show that the 15 Tesla lattice cools in 6D phase space by a factor /spl ap/2 over a distance of 20 m.

The muon beams in a high luminosity muon collider are produced with a very large emittance. The process of ionization cooling offers a method for reducing the 6-dimensional normalized emittance of the beam by a factor of {approx} 10{sup 6}. A simple analytic theory has been developed that demonstrates the dependence of the net cooling on various experimental parameters. The simple theory has been checked and realistic arrangements have been examined using Monte Carlo simulations. Transverse cooling of the initial beam can be achieved using passive Li absorbers in a FOFO lattice. The last factor of 10 in transverse cooling probably requires the use of current-carrying Li lenses. Efficient longitudinal cooling requires the use of wedge shaped absorbers in a dispersive section of the beam line. An example, multi-stage cooling scenario has been developed that meets the requirements of the muon collider. Preliminary designs have been made of solenoids for use in the FOFO lattice and of solenoids and dipoles for use in the emittance exchange sections. Detailed simulation work, farther optimization, and preparations for experimental demonstrations of critical components are currently in progress.

Ionization cooling may play an important role in reducing the phase space volume of muons for a future muon‐muon collider. We describe a possible experiment to demonstrate transverse emittance cooling using a muon beam at the AGS at Brookhaven National Laboratory. The experiment uses device dimensions and parameters and beam conditions similar to what is expected in an actual muon‐muon collider.

Beam aberrations are a special 3‐dimensional dynamic problem for the Cluster Klystron. Since the multiple‐beam section is immersed in a single focusing solenoid, electron beams have to travel off the axis of the solenoid and so they encounter non‐uniform and non‐axisymmetric electric and magnetic fields. Those external fields and space charge forces can cause beam aberrations. Some calculations and simplified simulations are presented in this paper. The results give a guideline for the mechanical design for the Cluster Klystron and show that the current design for a 3‐beam klystron is practical.

A general description is given of the status of the cluster klystron project. This paper is chiefly concerned with the mechanical design, magnetic field, plasma wavelength analyses, and beam dynamics. Finally, an idea for a new type of output window is presented.

The code POISSON is used to determine the longitudinal extent of the good field region of the cluster klystron solenoid. The field shape as a function of end-coil current enhancements is determined.

We describe the design parameters and expected performance of the analysis spectrometer for beamline 1 at the BNL Accelerator Test Facility. The spectrometer should be well suited for measuring the change in energy caused by the first generation laser acceleration experiments.

This Proposal is an updated version of FWP submitted in March 1992. Significant work has been done since the original proposal, and much of this is reported on in this update. In addition there have been several changes made, some in response to suggestions made by the three reviews sent to us in December, 1992. The new information and changes include: Technical information on the proposed design of the magnetron gun, the magnet, acceleration gap, and electrical system (including a comment on efficiency loss due to high-voltage leakage current). Modification of the phase I and II tests to allow operation of the gun and klystron off the axis of the magnet, thus simulating the magnet situation when multiple beams are used. Modification of phases III and IV to test a cluster of three beams: first a three beam gun, and then three beams with a klystron on one of them. We have added a phase V which would be the testing of a full three-beam demonstration klystron. The mod-anode pulser would now be located on the high voltage deck instead of externally. Power for the pulser and other high voltage components would now be provided by an isolation transformer insteadmore » of from a lead battery. We believe these changes have improved the proposed program and thank the reviewers for their constructive suggestions. The design is still evolving. Relatively little work has been done on the detailed klystron design, and none on the beam dump.« less

The components and experimental programs at the Brookhaven Accelerator Test Facility are discussed. The linac, rf gun, and Co2 laser system are briefly described. Research includes the production of high‐power coherent radiation sources. (AIP)

We propose to investigate new methods of particle acceleration using a short-pulse CO{sub 2} laser as the power source and grating-like structures as accelerator cavities''. Phase I of this program is intended to demonstrate the principle of the method. We will focus the laser light to a 3 mm line on the surface of the microstructure. The structure is used to transform the electric field pattern of the incoming transversely polarized laser beam to a mode which has a component along the electron beam direction in the vicinity of the surface. With 6 mJ of laser energy and a 6 ps pulse length, the electric field in the spot will be around 1 GV/m. The electron beam from the Brookhaven Accelerator Test Facility (ATF) will be focused transversely within the few micron transverse dimension of the microstructure. The maximum expected acceleration for a 1 GV/m field and a 3 mm acceleration length is 3 MeV. 17 refs., 11 figs., 2 tabs.