Benchmarking electron-cloud simulations and pressure measurements at the LHC

During the beam commissioning of the Large Hadron Collider (LHC) with 150, 75, 50 and 25-ns bunch spacing, important electron-cloud effects, like pressure rise, cryogenic heat load, beam instabilities or emittance growth, were observed. A method has been developed to infer different key beam-pipe surface parameters by benchmarking simulations and pressure rise observed in the machine. This method allows us to monitor the scrubbing process (i.e. the reduction of the secondary emission yield as a function of time) in the regions where the vacuum-pressure gauges are located, in order to decide on the most appropriate strategies for machine operation. In this paper we present the methodology and first results from applying this technique to the LHC.Comment: 5 pages, 7 figures, presented at ECLOUD 12: Joint INFN-CERN-EuCARD-AccNet Workshop on Electron-Cloud Effects, La Biodola, Isola d Elba, Italy, 5-9 June 201

Beam-beam studies for the High-Energy LHC

LHC upgrades are being considered both towards higher luminosity (HL-LHC) and towards higher energy (HE-LHC). In this paper we report initial studies of the beam-beam effects in the HE-LHC [1]. The HE-LHC aims at beam energies of 16.5 TeV, where the transverse emittance decreases due to synchrotron radiation with a 2-hour damping time. As a result of this emittance, shrinkage the beam-beam parameter increases with time, during a physics store. The beam-beam limit in the HE-LHC is explored using computer simulations.Comment: 6 pages, contribution to the EuCARD-AccNet-EuroLumi Workshop: The High-Energy Large Hadron Collider, Malta, 14 -- 16 Oct 201

TLEP: A High-Performance Circular e+e- Collider to Study the Higgs Boson

The recent discovery of a light Higgs boson has opened up considerable interest in circular e+e- Higgs factories around the world. We report on the progress of the TLEP concept since last year. TLEP is an e+e- circular collider capable of very high luminosities in a wide centre-of-mass (ECM) spectrum from 90 to 350 GeV. TLEP could be housed in a new 80 to 100 km tunnel in the Geneva region. The design can be adapted to different ring circumference (e.g. LEP3 in the 27 km LHC tunnel). TLEP is an ideal complementary machine to the LHC thanks to high luminosity, exquisite determination of ECM and the possibility of four interaction points, both for precision measurements of the Higgs boson properties and for precision tests of the closure of the Standard Model from the Z pole to the top threshold.Comment: Contribution to IPAC13, 12-17 May 2013, Shanghai, Chin

Grain yield gains in three recurrent selection cycles in the CNA-IRAT 4 irrigated rice population.

One line of research on irrigated rice genetic breeding programs at Embrapa consists of synthesizing wide genetic base populations followed by recurrent selection. This strategy ensures systematic continuous gains for grain yield and other traits of interest. To estimate the gains observed in three recurrent selection cycles in the CNA-IRAT 4 population, the grain yield data from 924 S0:2 families in 14 experiments carried out in various Brazilian states in the 1992/93, 1994/95 and 1997/98 growing seasons were analyzed. A triple lattice (two 10 x 10 and two 8 x 8 lattices) expérimental design was used in the first cycle and Federer augmented blocks in the two subsequent cycles. A non -significant gain was observed in the first cycle (only 15.7 kg/ha (0.28%). The gain observed in the second cycle and the mean gain observed due the selection in the first and second cycles were significante and of high magnitude (369.9 kg/ha (6.65%) and 259.9 kg/ha (4.67%), respectively). Results showed that recurrent selection applied to genetically divergent populations can result in considerable gains for grain yield

Seletividde de agrotóxicos aos parasitoides de ovos Trichogramma pretiosum E Telenomus remus.

Os parasitoides de ovos destacam-se por atacarem a fase de ovo das pragas, controlando-as antes de causarem danos às plantas. Entretanto, a aplicação de agrotóxicos ainda é indispensável para garantir a boa produtividade das culturas. Neste contexto, em programas de manejo integrado de pragas (MIP), é recomendável utilizar diversas táticas para reduzir os danos dos insetos-praga e, portanto, a associação do controle químico e biológico é viável com a utilização de produtos seletivos aos inimigos naturais. Assim, avaliou-se a seletividade de espiromesifeno, flubendiamida, espirotetramate + imidacloprido, clorpirifós, cletodim, clorimurom-etílico, éster metílico de óleo de soja e a mistura deste último com espirotetramate + imidacloprido sobre os adultos de Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) e Telenomus remus (Nixon) (Hymenoptera: Scelionidae) e pupas de T. pretiosum segundo as normas padronizadas da “International Organization for Biological Control” (IOBC) em laboratório. Entre os tratamentos testados (g. ia/ha), os inseticidas espiromesifeno (144), flubendiamida (12) e espirotetramate (30) + imidacloprido (90) foram seletivos as fases dos parasitoides avaliadas. O adjuvante éster metílico de óleo de soja (360) também foi seletivo, entretanto, quando misturado com o espirotetramate (30) + imidacloprido (90) apresentou uma redução no parasitismo 2 e 5 dias após o início dos ensaios com T. remus e T. pretiosum, respectivamente. Flubendiamida (33,6) também foi seletivo para adultos de T. remus e pupas de T. pretiosum, mas reduziu a taxa de parasitismo após o segundo dia do ensaio com adultos de T. pretiosum. Os herbicidas cletodim (108) e clorimurom-etílico (20) foram seletivos a adultos de T. remus mas tiveram maior impacto sobre T. pretiosum reduzindo o parasitismo desse agente de controle biológico que se mostrou mais sensível a esses produtos. O inseticida clorpirifós (480) foi nocivo a todas as fases dos parasitoides avaliadas. Em geral, ocorreram diferenças na seletividade dos agrotóxicos avaliados aos inimigos naturais, além de diferenças na sensibilidade dos mesmos em relação aos produtos e doses testados. Portanto, em programas de MIP devem ser priorizados os agrotóxicos seletivos ao maior número de agentes de controle biológico.SICONBIOL 2011

Driven Rydberg atoms reveal quartic level repulsion

The dynamics of Rydberg states of a hydrogen atom subject simultaneously to uniform static electric field and two microwave fields with commensurate frequencies is considered in the range of small fields amplitudes. In the certain range of the parameters of the system the classical secular motion of the electronic ellipse reveals chaotic behavior. Quantum mechanically, when the fine structure of the atom is taken into account, the energy level statistics obey predictions appropriate for the symplectic Gaussian random matrix ensemble.Comment: 4 pages, 3 figures, accepted for publication in Phys. Rev. Let

Dynamics of a Bose-Einstein Condensate in an Anharmonic Trap

We present a theoretical model to describe the dynamics of Bose-Einstein condensates in anharmonic trapping potentials. To first approximation the center-of-mass motion is separated from the internal condensate dynamics and the problem is reduced to the well known scaling solutions for the Thomas-Fermi radii. We discuss the validity of this approach and analyze the model for an anharmonic waveguide geometry which was recently realized in an experiment \cite{Ott2002c}