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A storage ring with tunable momentum compaction has the advantage in achieving different RMS bunch length with similar RF capacity, which is potentially useful for many applications, such as linear collider damping ring and predamping ring where injected beam has a large energy spread and a large transverse emittance. A tunable bunch length also makes the commissioning and fine tuning easier in manipulating the single bunch instabilities. In this paper, a compact ring design based on a supercell is presented, which achieves a tunable momentum compaction while maintaining a large dynamic aperture.

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We have searched for the lepton-number violating processes B{sup +} {yields} h{sup -}{ell}{sup +}{ell}{sup +} with h{sup -} = K{sup -}/{pi}{sup -} and {ell}{sup +} = e{sup +}/{mu}{sup +}, using a sample of 471 {+-} 3 million B{bar B} events collected with the BABAR detector at the PEP-II e{sup +}e{sup -} collider at the SLAC National Accelerator Laboratory. We find no evidence for these decays and place 90% confidence level upper limits on their branching fractions B (B{sup +} {yields} {pi}{sup -}e{sup +}e{sup +}) < 2.3 x 10{sup -8}, {Beta}(B{sup +} {yields} K{sup -}e{sup +}e{sup +}) < 3.0 x 10{sup -8}, {Beta}(B{sup +} {yields} {pi}{sup -}{mu}{sup +}{mu}{sup +}) < 10.7 x 10{sup -8}, and {Beta}(B{sup +} {yields} K{sup -}{mu}{sup +}{mu}{sup +}) < 6.7 x 10{sup -8}.

In this contribution, we will give a brief overview of the progress that has been achieved in the field of combining matrix elements and parton showers. We exemplify this by focusing on the case of electron-positron collisions and by reporting on recent developments as accomplished within the SHERPA event generation framework.

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The presence of melanin pigments in organisms is implicated in radioprotection and in some cases, enhanced growth in the presence of high levels of ionizing radiation. An understanding of this phenomenon will be useful in the design of radioprotective materials. However, the protective mechanism of microbial melanin in ionizing radiation fields has not yet been elucidated. Here we demonstrate through the electrochemical techniques of chronoamperometry, chronopotentiometry and cyclic voltammetry that microbial melanin is continuously oxidized in the presence of gamma radiation. Our findings establish that ionizing radiation interacts with melanin to alter its oxidation-reduction potential. Sustained oxidation resulted in electric current production and was most pronounced in the presence of a reductant, which extended the redox cycling capacity of melanin. This work is the first to establish that gamma radiation alters the oxidation-reduction behavior of melanin, resulting in electric current production. The significance of the work is that it provides the first step in understanding the initial interactions between melanin and ionizing radiation taking place and offers some insight for production of biomimetic radioprotective materials.

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We have investigated the chemical interaction between a Au/V/Al/V layer structure and n-type AlN epilayers using soft x-ray photoemission, x-ray emission spectroscopy, and atomic force microscopy. To understand the complex processes involved in this multicomponent system, we have studied the interface before and after a rapid thermal annealing step. We find the formation of a number of chemical phases at the interface, including VN, metallic vanadium, aluminum oxide, and metallic gold. An interaction mechanism for metal contact formation on the entire n-(Al,Ga)N system is proposed.

The Positron Source for the International Linear Collider requires an optical matching device after the target to increase the capture efficiency for positrons. Pulsed flux concentrators have been used by previous machines to improve the capture efficiency but the ILC has a 1 ms long pulse train which is too long for a standard flux concentrator. A pulsed flux concentrator with a 40 ms flat top was created for a hyperon experiment in 1965 which used liquid nitrogen cooling to reduce the resistance of the concentrating plates and extend the lifetime of the pulse. We report on a design for a 1 ms device based on this concept.

The laser and optics system for the photon collider seeks to minimize the required laser power by using an optical stacking cavity to recirculate the laser light. An enhancement of between 300 to 400 is desired. In order to achieve this the laser pulses which drive the cavity must precisely match the phase of the pulse circulating within the cavity. We report on simulations of the performance of a stacking cavity to various variations of the drive laser in order to specify the required tolerances of the laser system. We look at the behavior of a simple four mirror cavity as shown in Fig. 1. As a unit input pulse is applied to the coupling mirror a pulse begins to build up in the interior of the cavity. If the drive pulses and the interior pulse arrive at the coupling mirror in phase the interior pulse will build up to a larger value. The achievable enhancement is a strong function of the reflectivity of the cavities. The best performance if attained when the reflectivities of the input coupler is matched to the internal reflectivities of the cavity. In Fig. 2 we show the build up of the internal pulse after …

In this paper, we analyze the bill savings from PV for residential customers of the California's two largest electric utilities, under existing net metering tariffs as well as under several alternative compensation mechanisms. We find that economic value of PV to the customer is dependent on the structure of the underlying retail electricity rate and can vary quite significantly from one customer to another. In addition, we find that the value of the bill savings from PV generally declines with PV penetration level, as increased PV generation tends to offset lower-priced usage. Customers in our sample from both utilities are significantly better off with net metering than with a feed-in tariff where all PV generation is compensated at long-run avoided generation supply costs. Other compensation schemeswhich allow customers to displace their consumption with PV generation within each hour or each month, and are also based on the avoided costs, yield similar value to the customer as net metering.

We present a combined experimental and theoretical work on the ionization energies of polyacetylene -- organic molecules considered as important building blocks to form polycyclic aromatic hydrocarbons (PAHs) in the proto planetary nebulae such as of CRL 618. This set of astrophysical data can be utilized with significant confidence in future astrochemical models of photon-dominated regions and also of the proto planetary nebulae CRL 618. We recommend ionization energies of polyacetylenes from diacetylene up to heptaacetylene with an experimental accuracy of +- 0.05 eV: 10.03 eV (diacetylene), 9.45 eV (triacetylene), 9.08 eV (tetraacetylene), 8.75 eV (pentaacetylene), 8.65 eV (hexaacetylene), and 8.50 eV (heptaacetylene); further, ionization energies and with an accuracy of +- 0.1 eV: 8.32 eV (octaacetylene) and 8.24 eV (nonaacetylene) were computed. Implications of these energies to the redox chemistry involved in the multiply charged metal-ion mediated chemistry of hydrocarbon-rich atmospheres of planets and their moons such as Titan are also discussed.

For more than 10 years, electron donor has been injected into the Snake River aquifer beneath the Test Area North site of the Idaho National Laboratory for the purpose of stimulating microbial reductive dechlorination of trichloroethene (TCE) in groundwater. This has resulted in significant TCE removal from the source area of the contaminant plume and elevated dissolved CH4 in the groundwater extending 250 m from the injection well. The delta13C of the CH4 increases from 56o/oo in the source area to -13 o/oo with distance from the injection well, whereas the delta13C of dissolved inorganic carbon decreases from 8 o/oo to -13 o/oo, indicating a shift from methanogenesis to methane oxidation. This change in microbial activity along the plume axis is confirmed by PhyloChip microarray analyses of 16S rRNA genes obtained from groundwater microbial communities, which indicate decreasing abundances of reductive dechlorinating microorganisms (e.g., Dehalococcoides ethenogenes) and increasing CH4-oxidizing microorganisms capable of aerobic co-metabolism of TCE (e.g., Methylosinus trichosporium). Incubation experiments with 13C-labeled TCE introduced into microcosms containing basalt and groundwater from the aquifer confirm that TCE co-metabolism is possible. The results of these studies indicate that electron donor amendment designed to stimulate reductive dechlorination of TCE may also stimulate …

We report the first observation of an anisotropy in the arrival direction of cosmic rays with energies in the multi TeV region in the Southern sky using data from the IceCube detector. Between June 2007 and March 2008, the partially-deployed IceCube detector was operated in a configuration with 1320 digital optical sensors distributed over 22 strings at depths between 1450 and 2450 meters inside the Antarctic ice. IceCube is a neutrino detector, but the data are dominated by a large background of cosmic ray muons. Therefore, the background data are suitable for high-statistics studies of cosmic rays in the Southern sky. The data include 4.3 billion muons produced by downgoing cosmic ray interactions in the atmosphere; these events were reconstructed with a median angular resolution of 3 degrees and a median energy of ~;; 20 TeV. Their arrival direction distribution exhibits an anisotropy in right ascension with a first harmonic amplitude of (6.4 +- 0.2 stat. +- 0.8 syst.) x 10-4.

We describe the scientific motivation for a new type of accelerator, the muon collider. This accelerator would permit an energy-frontier scientific program and yet would fit on the site of an existing laboratory. Such a device is quite challenging, and requires a substantial R&D program. After describing the ingredients of the facility, the ongoing R&D activities of the Muon Accelerator Program are discussed. A possible U.S. scenario that could lead to a muon collider at Fermilab is briefly mentioned.

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A Neutrino Factory requires an intense and well-cooled (in transverse phase space) muon beam. We discuss a hybrid approach for a linear 4D cooling channel consisting of high-pressure gas-filled RF cavities--potentially allowing high gradients without breakdown--and discrete LiH absorbers to provide the necessary energy loss that results in the required muon beam cooling. We report simulations of the channel performance and its comparison with the vacuum case; we also briefly discuss technical and safety issues associated with cavities filled with high-pressure hydrogen gas. Even with additional windows that might be needed for safety reasons, the channel performance is comparable to that of the original, all-vacuum Feasibility Study 2a channel on which our design is based. If tests demonstrate that the gas-filled RF cavities can operate effectively with an intense beam of ionizing particles passing through them, our approach would be an attractive way of avoiding possible breakdown problems with a vacuum RF channel.

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