123523434
Effect of a biased probe on the afterglow operation of an ECR4 ion source
Various experiments have been performed on a 14.5 GHz ECR4 in order to improve the ion yield. The source runs in pulsed afterglow mode, and provides currents ∼120 eμA of Pb27+ to the CERN Heavy Ion Facility on an operational basis. In the search for higher beam intensities, the effects of a pulsed biased disk on axis at the injection side were investigated with different pulse timing and voltage settings. No proof for absolute higher intensities was seen for any of these modifications. However, the yield from a poorly tuned/low-performing source could be improved and the extracted pulse was less noisy with bias voltage applied. The fast response on the bias implies that increases/decreases are not due to ionization processes. A good tune for high yield of high charge states during the afterglow coincides with a high plasma potential.
115300845
Status and first beam measurements on the CERN RFQ
55729922
Experiments on a 14.5 GHz ECR Source
A device for measuring the speed of the wind at medium altitude by the Doppler effect within the visible frequency range comprises a laser which emits pulses of light, a telescope which receives a scattered light and an interferometer used to measure the spectral shift of the scattered light in relation to the emitted pulse of light. The interferometer is a Fabry-Perot interferometer in which a part of one of the two mirrors of the interferometer is covered with an excess thickness of silica to form two separate filters. The spacing of the two mirrors and the excess thickness of silica are determined in such a manner that the pass bands of each one of the two filters thus constructed are centered on the flanks of the spectral distribution of the backscattered light.
119401628
The Electron Cooling Device for LEAR
The experiments1,2,3 in which low energetic protons were cooled by a “cold” electron beam have proved that this method is a very powerful technique to improve low energy beams and to increase their phase space density by several orders of magnitude in short times. The theoretical understanding of the cooling process is well advanced4,5,6. The applications of this technique, which was invented and developed in Novosibirsk, are manifold7. It seems to be clear that its main domain is the cooling of non-relativistic ions. However, also at extremely high energies, cooling of protons and antiprotons with stored electrons (cooled themselves by synchrotron radiation) can be contemplated8,9.
121894301
Studies on ECR4 for the CERN ion program
The CERN heavy ion community, and some other high energy physics experiments, are starting to demand other ions, both heavy and light, in addition to the traditional lead ions. Studies of the behavior of the afterglow for different operation modes of the ECR4 at CERN have been continued to try to understand the differences between pulsed afterglow and continuous operation, and their effect on ion yield and beam reproducibility. The progress in adapting the source and ion beam characteristics to meet the new demands will be presented, as will new information on voltage holding problems in the extraction.
102555920
The LHC Lead Ion Injector Chain
119634910
Energy-density fluctuations in de Sitter space
Abstract Quantum fluctuations in de Sitter space or in the de Sitter phase of an inflationary universe give rise to a spectrum of classical energy-density perturbations which is scale invariant. The analysis presented in this letter is based on a consistent expansion in powers of ħ, and on the functional Schrodinger approach to quantum field theory in de Sitter space. The result holds for a large class of initial states of the quantum field, including the Bunch-Davies vacuum.
123324722
Status of the top‐quark
A brief review of current predictions and bounds on the mass of the t-quark is presented. Most involve new ideas based on Grand Unification.
119530771
Acceleration in the linear non-scaling fixed-field alternating-gradient accelerator EMMA
In a fixed-field alternating-gradient (FFAG) accelerator, eliminating pulsed magnet operation permits rapid acceleration to synchrotron energies, but with a much higher beam-pulse repetition rate. Conceived in the 1950s, FFAGs are enjoying renewed interest, fuelled by the need to rapidly accelerate unstable muons for future high-energy physics colliders. Until now a ‘scaling’ principle has been applied to avoid beam blow-up and loss. Removing this restriction produces a new breed of FFAG, a non-scaling variant, allowing powerful advances in machine characteristics. We report on the first non-scaling FFAG, in which orbits are compacted to within 10 mm in radius over an electron momentum range of 12–18 MeV/c. In this strictly linear-gradient FFAG, unstable beam regions are crossed, but acceleration via a novel serpentine channel is so rapid that no significant beam disruption is observed. This result has significant implications for future particle accelerators, particularly muon and high-intensity proton accelerators.
119039939
Topology in the bulk: Gauge field solitons in extra dimensions
Certain static soliton configurations of gauge fields in 4+1 dimensions correspond to the instanton in 4 Euclidean dimensions “turned on its side”, becoming a monopole in 4+1. The periodic instanton solution can be used with the method of images to construct solutions satisfying D-brane boundary conditions. The θ-term on the brane becomes a topological current source, yielding an emission amplitude for monopoles into the bulk. Instantons have a novel reinterpretation in terms of monopole exchange between branes.
122741754
Are There Significant Gravitational Corrections to the Unification Scale
Abstract Higher dimension operators may be induced in the lagrangian of a unified theory by gravity. We find that c tr( G μv G μv H )/ M Planck can lead to substantial corrections to the unification scale. For ordinary SU(5) a second solution unifying at 10 17 GeV can exist which has no observable proton decay but an unacceptable value of sin 2 θ w . Analogous effects in supersymmetry, however, can lead to enormous corrections. We find that supersymmetric SU(5) can unify anywhere between 5 × 10 16 M X 18 GeV with an acceptable sin 2 θ w for | c | ⩽ 1.0.