102555920
The LHC Lead Ion Injector Chain
55652058
A heavy ion linac for the CERN accelerator complex
The injector linac required by CERN for heavy ions. e.g. Pb28+. is being made in collaboration with several institutions in CERN member states. Starting with Pb28+ ions at 2.5 keV/u from an ECR source, the beam will be analyzed and matched into a Radio-Frequency Quadrupole (RFQ) which operates at 101.3 MHz and accelerated to 250 keV/u. After a matching section the beam is accelerated to 4.2 MeV/u by a three cavity Interdigital-H (IH) structure. Then follows stripping, beam analysis and debunching to produce a Pb53+ beam for the booster synchrotron. This paper summarizes lthe design. the technical solutions proposed and the present status.
55444273
Present Performance of the CERN Proton Linac
The original 1973 design specification of the CERN 50 MeV Proton Linac was for a 150 mA beam but this intensity was rarely used. Preliminary tests for the high brightness beam required for LHC indicated that 170 mA could be produced for short pulses (30 Ps). Since then further optimisation has enabled the 170 mA to be delivered reliably, within the nominal emittances and dispersion, in long pulses (120 Ps) to the user, the PS Booster (PSB), about 80 m downstream of the linac. The improvements will be described along with the steps envisaged to attain a goal of more than 180 mA.
115538459
Ion and electron sources
Although the acceleration of particle beams is understood by accelerator physicists, the source of the primary particles is often cloaked in mystery. This paper will attempt to shed some light on the principles and operation of basic lepton and hadron sources commonly used in accelerators.
54890488
Study of beam parameters of the CERN proton linac using a three dimensional bunch shape monitor
A Three Dimensional Bunch Shape Monitor (3D-BSM) has been developed for the CERN Proton Linac 2. A new area for beam studies at high intensities has been opened by this detector. Bunch density distributions in all three dimensions and their variations along the beam pulse can be obtained. Changing field gradients in linac quadrupoles, emittance variation along the bunch has been calculated. Measurements of beam halos become possible thanks to the large dynamic range of the device. Beam parameters at various linac settings have been measured and analysed. Introduction The new detector [1] allows the measurement of the three dimensional density distribution I(x,y,z) of a bunch and its evolution along the beam pulse. For example, using this distribution the first and second moments and the beam profiles in each direction (x,y,z) have been obtained. The CERN Linac 2 is a high intensity accelerator consisting of an RFQ and three Alvarez tanks producing 140 mA of protons at 50 MeV [2]. As proven during the detector commissioning, the 100 μm tungsten wire can operate safely with pulse lengths up to 145 μs. The insertion of the target in the beam does not disturb injection into the downstream booster synchrotron. Therefore the 3D-BSM can be used as a nondestructive beam diagnostic tool during linac operation. Bunch Shape Measurements of the 50 MeV Beam In Fig.1 the evolution of the longitudinal profile along the beam pulse is presented. The analysis of the figure as well as of the evolution of other beam parameters along the bunch shows that beam-loading is well compensated in Linac 2. There is no variation either of the bunch centre or the bunch shape along the entire pulse length. It has been demonstrated that the bunch shape changes along the pulse if beam-loading is not sufficiently compensated. This can be seen in Fig. 2 where the RF field in tank 3 has been increased by 4% while keeping the maximum power to the tank constant. 0.0 22.9 45.8 68.8 91.7 0 10 20 30 40 50 60 70
115300845
Status and first beam measurements on the CERN RFQ
118719894
Topological interactions in warped extra dimensions
Topological interactions will be generated in theories with compact extra dimensions where fermionic chiral zero modes have different localizations. This is the case in many warped extra dimension models where the right-handed top quark is typically localized away from the left-handed one. Using deconstruction techniques, we study the topological interactions in these models. These interactions appear as trilinear and quadrilinear gauge boson couplings in low energy effective theories with three or more sites, as well as in the continuum limit. We derive the form of these interactions for various cases, including examples of Abelian, non-Abelian and product gauge groups of phenomenological interest. The topological interactions provide a window into the more fundamental aspects of these theories and could result in unique signatures at the Large Hadron Collider, some of which we explore.
119877053
The dimension-5 Lorentz invariant operator system in QCD☆
We analyze the d = 5 operator mixing problem in the α gauge from the standpoint of illustrating various results in formal operator mixing theory. There is one physical gauge-invariant operator and also two unphysical “nuisance” operators. The anomalous dimension eigenvalue of the physical operator is shown to be explicitly gauge invariant; mixing to and between nuisance operators is α dependent and nuisance operators do not mix back to the physical sector. This is, perhaps the simplest system illustrating all of these features. We also discuss Higgs-boson induced d = 5 operators in the nonleptonic weak Hamiltonian.
120690224
{QCD} Prediction for the Structure Functions of the Photon
We compute the unpolarized deep inelastic structure functions of the photon in an asymptotically free gauge theory, including mass effects. We show that when the momentum squared of the struck photon is small relative to the contributing quark mass, m, the free quark model prediction is obtained to O(1/ln(Q2/m2)) and (g2ln(Q2/m2)). For the light quark contribution the perturbation expansion does not converge. For large momentum squared of the struck photon the free quark model result is renormalized by a finite amount computable in QCD. For forseeable experimental ranges ofQ2 this renormalization is small.
32908492
Topological Physics of Little Higgs Bosons
Topological interactions will generally occur in composite Higgs or Little Higgs theories, extra-dimensional gauge theories in which A5 plays the role of a Higgs boson, and among the pNGB's of technicolor. This phenomena arises from the chiral and anomaly structure of the underlying UV completion theory, and/or through chiral delocalization in higher dimensions. These effects are described by a full Wess-Zumino-Witten term involving gauge fields and pNGB's. We give a general discussion of these interactions, some of which may have novel signatures at future colliders, such as the LHC and ILC.
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.