Wake fields in HCS accelerator and CTS power line of the CLIC Test Facility (CTF II): simulation with program wake

One of the two parallel beam lines of the CTF II, (the 'Drive Beam') is providing the other (the accelerator) with 30 GHz power. Experimentation was performed in 98 and later with a CTF layout to study acceleration of a train of bunches with beam loading compensation, bunch length compression and 30 GHz conversion of the Drive Beam power [1]. This conversion is limited by the difficulty of transmitting the beam through the structures extracting the beam power (CTS). A large transverse wake loss factor is associated with the necessary high longitudinal wake loss factor in CTS. Therefore the limitation of transmission should come mainly from transverse wakes in CTS. Dynamics in HCS and in the bunch compression device was studied with codes GPT [2] and PARMELA [3], [4] using beam parameters input derived from calculations of the beam in the RF gun with code MAFIA. Code WAKE is used to verify that the influence of the wake-fields in HCS is small, to follow the beam along the 4 CTS of the drive linac, and to give results for the transmission, which can be compared with the experimental ones

Neutrino factory plans at CERN

The considerable interest raised by the discovery of neutrino oscillations and recent progress in studies of muon colliders has triggered interest in considering a neutrino factory at CERN. This paper explains the reference scenario, indicates the other possible choices and mentions the R&D that are foreseen

Modular perverse sheaves on flag varieties I: tilting and parity sheaves

In this paper we prove that the category of parity complexes on the flag variety of a complex connected reductive group is a "graded version" of the category of tilting perverse sheaves on the flag variety of the dual group, for any field of coefficients whose characteristic is good. We derive some consequences on Soergel's modular category O, and on multiplicities and decomposition numbers in the category of perverse sheaves.Comment: 42 pages; with a joint appendix with Geordie Williamso

Dynamics in isochronous machine of FFAG type

Machines of FFAG type are considered for the different stages of a neutrino factory: ionization cooling, phase rotation and acceleration of the muons. Ionization cooling and phase rotation of the muons are performed at low energy. One could match the accelerating field frequency with the variation of the revolution frequency if the energy dispersion of the injected beam was small. But efficiency requires the acceptance of a large energy spread of the injected muons. Therefore a machine isochronous for all energies is an attractive solution. Isochronisms can be provided as the result of two effects: a magnetic field variation with the distance to the machine centre and a variation of the azimuthal separation between the magnets with the distance to the centre [1]. A suitable combination of these effects may give the best results in geometry and focusing properties. Because of the lifetime constraints, high accelerating gradients are required and one may accept crossing betatron resonances because their effects cannot build up much in a limited number of turns. The purpose is to follow the trajectories by direct intergration of the action of the fields

Tracking particles with wake fields and space charge effects

A simple and precise way to account for beam cavity interactions is the use of delta wake potentials known from RF calculations or measurements. When this procedure is introduced in a tracking program following super-particles such as in PARMELA, besides the effect of the space charge, the evolution of the charge distribution within the bunches of a train can be determined. The interesting application is for non-rigid bunches at intermediate or low energy, as for the study of Compact Linear Collider beams in the CLIC Test Facility at CERN

A code for multibunched beams with wakefields, group velocities and space charge

Tracking multiparticle bunches with PIC codes is possible, but limited to very short distances. Using the modal description these codes provide, PARMTRACK can calculate detailed intra bunch dynamics, and bunch to bunch dynamics for travelling in relatively long beam lines. Macro-particle simulation allows for permanent redistribution in longitudinal as well as in transverse space, without any limiting approximations. Care is taken of group velocities associated with each frequency of the wakefield description. Applications are shown for the part of the CLIC two-beam test facility producing the 30 GHz power

The Drive Beam Decelerator of CLIC

In the Compact Linear Collider (CLIC) a high-current, low-energy beam will be decelerated in a chain of power extraction structures to produce the RF-power necessary to accelerate a low-current, high-energy beam in the main linac. The transverse dynamics of the decelerated beam is discussed, based on results of the programs WAKE [1] and PLACET [2]. The very large energy spread and strong transverse wakefields as well as the high group velocity of these fields and the considerable length of the bunch train are important factors. Static and dynamic imperfections are considered including ground motion. The choice of parameters for the structures is investigated. A promising beam-based alignment technique is presented that makes use of a low emittance beam

The Theatre of the Absurd and Psychoanalysis: E. Albee’s The Zoo Story as a Study Case.

This article aims at showing the link between Psychology/ Psychoanalysis and The Theatre of the Absurd. An attempt is made to study the postmodern anti-hero in Edward Albee’s absurd tragedy in order to show the way new thoughts, beliefs, and morals are oppressed by the old certainties of the mainstream cultural discourse. The study puts emphasis on one major psychological aspect-for instance the transference process- coined by Julia Kristeva to demonstrate the psychical obstacles, traumas, fears, and desires of the self in his never completed identity stability. This transference process should move through a three-dimensional temporality to ensure a well-balanced identity of the self. The first time is called the linear time; the second is the zero time, and the third is the resurrection time. In order to conduct this issue, I have proposed to analyze Edward Albee’s The Zoo Story as a sample of the postmodern struggle for achieving identity stability. As a conclusion, I have reiterated that unlike any other theatre of any other previous age, The Theatre of the Absurd-with its complex language and its literary devices- is much closer to Psychoanalysis and much concerned with an individual’s inner struggle that seeks to secure a position of respect and dignity within the symbolic order of the world.     

Fast algorithm for border bases of Artinian Gorenstein algebras

Given a multi-index sequence $$\sigma$$, we present a new efficient algorithm to compute generators of the linear recurrence relations between the terms of $$\sigma$$. We transform this problem into an algebraic one, by identifying multi-index sequences, multivariate formal power series and linear functionals on the ring of multivariate polynomials. In this setting, the recurrence relations are the elements of the kerne l$I$\sigma of the Hankel operator $H$\sigma associated to $$\sigma$$. We describe the correspondence between multi-index sequences with a Hankel operator of finite rank and Artinian Gorenstein Algebras. We show how the algebraic structure of the Artinian Gorenstein algebra $A$\sigma$$associated to the sequence$$\sigma yields the structure of the terms $\sigma\alpha$for all$$\alpha$ $\in$ N n$. This structure is explicitly given by a border basis of$A$\sigma$$, which is presented as a quotient of the polynomial ring$K[x 1 ,. .. , xn$] by the kernel$I$\sigma$$of the Hankel operator$H$\sigma$$. The algorithm provides generators of$I$\sigma$$constituting a border basis, pairwise orthogonal bases of$A$\sigma$$ and the tables of multiplication by the variables in these bases. It is an extension of Berlekamp-Massey-Sakata (BMS) algorithm, with improved complexity bounds. We present applications of the method to different problems such as the decomposition of functions into weighted sums of exponential functions, sparse interpolation, fast decoding of algebraic codes, computing the vanishing ideal of points, and tensor decomposition. Some benchmarks illustrate the practical behavior of the algorithm

Impacts of G x E x M on Nitrogen Use Efficiency in Wheat and Future Prospects

Globally it has been estimated that only one third of applied N is recovered in the harvested component of grain crops (Raun and Johnson 1999). This represents an incredible waste of resource and the overuse has detrimental environmental and economic consequences. There is substantial variation in nutrient use efficiency (NUE) from region to region, between crops and in different cropping systems. As a consequence, both local and crop specific solutions will be required for NUE improvement at local as well as at national and international levels. Strategies to improve NUE will involve improvements to germplasm and optimized agronomy adapted to climate and location. Essential to effective solutions will be an understanding of genetics (G), environment (E) and management (M) and their interactions (G x E x M). To implement appropriate solutions will require agronomic management, attention to environmental factors and improved varieties, optimized for current and future climate scenarios. As NUE is a complex trait with many contributing processes, identifying the correct trait for improvement is not trivial. Key processes include nitrogen capture (uptake efficiency), utilization efficiency (closely related to yield), partitioning (harvest index: biochemical and organ-specific) and trade-offs between yield and quality aspects (grain nitrogen content), as well as interactions with capture and utilization of other nutrients. A long-term experiment, the Broadbalk experiment at Rothamsted, highlights many factors influencing yield and nitrogen utilization in wheat over the last 175 years, particularly management and yearly variation. A more recent series of trials conducted over the past 16 years has focused on separating the key physiological sub-traits of NUE, highlighting both genetic and seasonal variation. This perspective describes these two contrasting studies which indicate G x E x M interactions involved in nitrogen utilization and summarizes prospects for the future including the utilization of high throughput phenotyping technology