Simulations on a potential hybrid and compact attosecond X-ray source based on RF and THz technologies

We investigate through beam dynamics simulations the potential of a hybrid layout mixing RF and THz technologies to be a compact X-ray source based on Inverse Compton Scattering (ICS), delivering few femtoseconds to sub-femtosecond pulses. The layout consists of an S-band gun as electron source and a dielectric-loaded circular waveguide driven by a multicycle THz pulse to accelerate and longitudinally compress the bunch, which will then be used to produce X-ray pulses via ICS with an infrared laser pulse. The beam dynamics simulations we performed, from the photocathode up to the ICS point, allows to have an insight in several important physical effects for the proposed scheme and also in the influence on the achievable bunch properties of various parameters of the accelerating and transverse focusing devices. The study presented in this paper leads to a preliminary layout and set of parameters able to deliver at the ICS point, according to our simulations, ultrashort bunches (around 1 fs rms), at 15 MeV, with at least 1 pC charge and transversely focused down to around 10 um rms or below while keeping a compact beamline (less than 1.5 m), which has not yet been achieved using only conventional RF technologies. Future studies will be devoted to the investigation of several potential ways to improve the achieved bunch properties, to overcome the limitations identified in the current study and to the definition of the technical requirements. This will lead to an updated layout and set of parameters.Comment: To be published in Nucl. Inst. Meth. A as proceedings of the EAAC17 conference 9 pages, 11 figure

Measurements of heavy ion beam losses from collimation

The collimation efficiency for Pb ion beams in the LHC is predicted to be lower than requirements. Nuclear fragmentation and electromagnetic dissociation in the primary collimators create fragments with a wide range of Z/A ratios, which are not intercepted by the secondary collimators but lost where the dispersion has grown sufficiently large. In this article we present measurements and simulations of loss patterns generated by a prototype LHC collimator in the CERN SPS. Measurements were performed at two different energies and angles of the collimator. We also compare with proton loss maps and find a qualitative difference between Pb ions and protons, with the maximum loss rate observed at different places in the ring. This behavior was predicted by simulations and provides a valuable benchmark of our understanding of ion beam losses caused by collimation.Comment: 12 pages, 20 figure

Beam Commissioning Plan For LHC Collimation

The Large Hadron Collider extends the present state-of-the-art in stored beam energy by 2-3 orders of magnitude. A sophisticated system of collimators is implemented along the 27 km ring and mainly in two dedicated cleaning insertions, to intercept and absorb unavoidable beam losses which could induce quenches in the superconducting (sc) magnets. 88 collimators for the two beams are initially installed for the so called Phase 1. An optimized strategy for the commissioning of this considerable number of collimators has been defined. This optimized strategy maximizes cleaning efficiency and tolerances available for operation, while minimizing the required beam time for collimator setup and ensuring at all times the required passive machine protection. It is shown that operational tolerances from collimation can initially be significantly relaxed

LHC Cleaning Efficiency with Imperfections

The performance reach of the LHC depends on the magnitude of beam losses and the achievable cleaning efficiency of its collimation system. The ideal performance reach for the nominal Phase 1 collimation system is reviewed. However, unavoidable imperfections affect any accelerator and can further deteriorate the collimation performance. Multiple static machine and collimator imperfections were included in the LHC tracking simulations. Error models for collimator jaw flatness, collimator setup accuracy, the LHC orbit and the LHC aperture were set up, based to the maximum extent possible on measurements and results of experimental beam tests. It is shown that combined “realistic” imperfections can reduce the LHC cleaning efficiency by about a factor 11 on average

Produção de gado de corte e acúmulo de matéria seca em sistemas de integração lavoura: pecuária em presença e ausência de trevo branco e nitrogênio.

O trabalho foi conduzido com o objetivo de verificar a influência da adubação nitrogenada em uma pastagem de azevém (Lolium multiflorium L.) e aveia (Avena strigosa Scherb) em presença e ausência de trevo branco (Trifolium repens L.), conferida pelo acúmulo e produção de matéria seca, ganho médio diário, ganho de peso vivo e carga animal no sistema de integração lavoura-pecuária sob sistema de plantio direto. A cultura antecessora da pastagem foi a soja (Glycine Max L.). O delineamento experimental foi em blocos completos ao acaso, com parcelas subdivididas e três repetições. Nas parcelas, foram testadas quatro doses de nitrogênio (0, 100, 200 e 300 kg.ha-1) e nas subparcelas, a combinação de presença e ausência de trevo branco. A elevação das doses crescentes de N aumentaram de forma linear crescente o acúmulo e a produção de matéria seca da pastagem. A carga animal e o ganho de peso vivo por hectare de bovinos aumentaram com o incremento de nitrogênio. Os resultados demonstram o efeito da adubação nitrogenada no acúmulo diário, na produção de matéria seca, carga animal e no ganho de peso vivo

Accelerator physics concept for upgraded LHC collimation performance

The LHC collimation system is implemented in phases, in view of the required extrapolation by 2-3 orders of magnitude beyond Tevatron and HERA experience in stored energy. All available simulations predict that the LHC proton beam intensity with the "Phase I" collimation system may be limited by the impedance of the collimators or cleaning efficiency. Maximum efficiency requires collimator materials very close to the beam, generating the dominant resistive wall impedance in the LHC. Above a certain intensity the beam is unstable. On the other hand, even if collimators are set very close to the beam, the achievable cleaning efficiency is predicted to be inadequate, requiring either beam stability beyond specifications or reduced intensity. The accelerator physics concept for upgrading cleaning efficiency, for both proton and heavy ion beams, and reducing collimator-related impedance is described. Besides the "Phase II" secondary collimators, new collimators are required in a few super-conducting regions

Measurements of the effect of collisions on transverse beam halo diffusion in the Tevatron and in the LHC

Beam-beam forces and collision optics can strongly affect beam lifetime, dynamic aperture, and halo formation in particle colliders. Extensive analytical and numerical simulations are carried out in the design and operational stage of a machine to quantify these effects, but experimental data is scarce. The technique of small-step collimator scans was applied to the Fermilab Tevatron collider and to the CERN Large Hadron Collider to study the effect of collisions on transverse beam halo dynamics. We describe the technique and present a summary of the first results on the dependence of the halo diffusion coefficient on betatron amplitude in the Tevatron and in the LHC.Comment: 4 pages, 2 figures. Submitted to the Proceedings of the ICFA Mini-Workshop on Beam-beam Effects in Hadron Colliders (BB2013), Geneva, Switzerland, 18-22 March 201