[en] The primary subject of working group 7 at the 2012 Advanced Accelerator Concepts Workshop was muon accelerators for a muon collider or neutrino factory. Additionally, this working group included topics that did not fit well into other working groups. Two subjects were discussed by more than one speaker: lattices to create a perfectly integrable nonlinear lattice, and a Penning trap to create antihydrogen.

[en] EMMA is an experiment to study beam dynamics in fixed field alternating gradient accelerators (FFAGs). It accelerates the beam in about 10 turns using 1.3 GHz cavities in a mode like that used for muon accelerators. Many applications of FFAGs prefer to have slower acceleration, typically thousands of turns. To do so in EMMA would require the RF system to be replaced with a low-frequency, high-gradient system. This paper describes the motivation for studying slow acceleration in EMMA and the required parameters for an RF system to do that. It then describes the technology needed for the RF system.

[en] We describe a lattice for accelerating muons from 375 GeV to 750 GeV. The lattice is a fast-ramping synchrotron with a mixture of fixed-field superconducting dipoles and warm dipoles, so as to have a high average bending field while still being able to rapidly change the average bending field as the beam momentum increases. For a 1.5 TeV center of mass muon collider, muons must be rapidly accelerated to 750 GeV. To accomplish this efficiently, we wish to make as many passes through the RF cavities as possible, while keeping the average RF gradients sufficiently high to avoid excess muon decays. A synchrotron where the magnets are very rapidly ramped has been envisioned as one option to accomplish this. The entire acceleration cycle takes place in less than 1 ms, presenting a technological challenge for the magnets. Clearly superconducting magnets cannot be ramped on this time scale, so instead room-temperature magnets will be ramped. To keep losses low, dipoles can use grain-oriented silicon steel, but quadrupoles will probably need to use more conventional steel, giving a lower maximum field for these high ramping rates. If we want to have a large average RF gradient and simultaneously make a large number of passes through the RF cavities, the average bending field must be high. To achieve such a large bending field while rapidly ramping magnets, it has been proposed to use a hybrid lattice consisting of interleaved superconducting dipoles and bipolar ramped dipoles. Due to the large single-bunch current and the relatively small apertures we desire (both because we would like to use high-frequency RF, and because power requirements and heating will be more reasonable for smaller aperture ramped magnets), collective effects are expected to be very significant. To reduce their effects, we propose to have strong synchrotron oscillations (a synchrotron tune of over 1). To have such a high synchrotron tune, a large number of superperiods are needed. Putting together all of these requirements, a set of requirements for a final acceleration stage for a muon collider has been proposed in Table 1. These basic requirements and some basics of the lattice structure for such a machine were decided upon at a workshop in April 2011 at the University of Mississippi, Oxford. Each superperiod consists of 6 arc cells, two sets of 2-cell dispersion suppressors, and three straight cells, for a total of 13 cells. Every cell has a FODO lattice structure. Each cell has a phase advance of π/2 in both the horizontal and vertical planes. The magnets will have their fields ramped with time so as to keep the cell tunes constant. All dipole magnets are rectangular. The quadrupoles are split into two pieces to allow the eventual insertion of sextupoles for chromaticity correction. The arc cell is described, and its lattice functions are plotted. In the arc cells, the fields will be set to keep the on-energy closed orbit centered in the quadrupoles and in the drift at the center of each half cell. The behavior of the off-energy orbits is shown. At the energy extremes, the ramped fields take on the values given in Table 3.

[en] The paper sets out two techniques for the containment in situ of contaminated soils by adsorbing and solidifying the material. The material is first brought to a fluid in the form of a suspension and then mixed either by mechanical or hydraulic means depending on local conditions. The paper concludes by giving a case example on the use of the technique on a site with known concentrations of contaminates, describing the pre and post investigation. (au)

No abstract available

[en] Recent experiments have shown severe surface damage and a reduction of the maximum accelerating gradient for an rf cavity that is operating under external magnetic fields. This implies that serious problems may occur in lattices where rf cavities and external magnetic fields coexist, such as those of the proposed neutrino factory and muon collider. Although existing data suggest that this magnetic field dependent breakdown is associated with the emission of electrons from locally enhanced field regions on the cavity surface, the mechanism that drives this effect is not yet well understood. Here, we show that such field emitted electrons are accelerated by the cavity and focused by the magnetic field to the other side of the cavity where they heat its surface. We show that if the magnetic field is strong, significant surface deformation can occur that eventually could limit the accelerating gradient of the cavity. Results of our model are compared to the existing experimental data from an 805 MHz cavity. The geometry of the pillbox cavity in our case is more complicated, and the analysis depends on the electron energies, focused dimensions, and angle of impact, but damage may reasonably be expected with similar cyclical heating above 40 C. However, it is not yet known what the mechanism is for such surface damage to cause a cavity to breakdown. One possibility is that if electrons are focused on a location with a high surface gradient, then the local damage will generate new asperities with higher FN enhancement factors, thus initiating breakdown. While our preliminary analysis offers some quantification on the effects of the magnetic fields on the cavity's operation, other theoretical issues were not addressed. For instance, emission from secondary electrons was disregarded, the asperity was placed on axis, the magnetic field was assumed as uniform, the thermal-diffusion calculation ignored the shape of the rise time, and adopted an approximate calculation. On the theoretical level, it will be interesting to pursue additional simulations exploring these effects in detail. Experimentally, there is a clear need for more well-designed experiments to study, systematically, the effect of external fields on the cavity's operation.

[en] An observer study was performed to determine the optimum filter function for single-photon emission CT (SPECT) image processing. The observer study images were reconstructed from the simulated projection data of a uniform cylinder containing a cold, spherical lesion, 2 cm in diameter. The simulated data incorporated the effects of attenuation, collimator and scatter response functions and noise characteristics typical of clinical liver studies. The observer task was lesion detection in 2 AFC and ROC experiments. The Butterworth filter showed an optimum cut-off frequency at 0.23 cycles/cm, and this filter function scored significantly better than either the Hanning or Metz filters. This optimum filter size matched the lesion size

[en] In a further education meeting, for members of the public health service, on information on nuclear energy and environment, their problems as a competent authority are outlined, namely to enlighten the population by presenting the hazards in an objective way and thus being a mediator between technical experts and the population. (ORU)

[en] Safety requirements for hoists, cranes, winches, crane carriages, load lifting installations and fuel changing devices (LWR) (HP/LN)

[en] HeLa and Chinese hamster ovary cells capable of proliferating at O2 levels that are ordinarily lethal to cells in tissue culture were selected by chronic adaptation to stepwise increased oxygen tensions. A popular hypothesis, originally proposed by Gerschman et al., states that the toxic action of both hyperoxia and X rays is based on a common mechanism involving the formation of oxidizing free radicals. Contrary to what may be predicted from this hypothesis we found that our oxygen-resistant substrains were not cross-resistant to X rays, as determined by a clonogenic cell survival assay. These results show that cellular properties governing increased resistance to killing by O2 do not necessarily contribute to cellular X ray tolerance