RF gymnastics in synchrotrons

The RF systems installed in synchrotrons can be used to change the longitudinal beam characteristics. 'RF gymnastics' designates manipulations of the RF parameters aimed at providing such non-trivial changes. Some keep the number of bunches constant while changing bunch length, energy spread, emittance, or distance between bunches. Others are used to change the number of bunches. After recalling the basics of longitudinal beam dynamics in a hadron synchrotron, this paper deals with the most commonly used gymnastics. Their principle is described as well as their performance and limitations.Comment: 16 pages, contribution to the CAS - CERN Accelerator School: Specialised Course on RF for Accelerators; 8 - 17 Jun 2010, Ebeltoft, Denmar

Preliminary considerations about the injectors of the HE-LHC

A hadron collider operating at an energy much larger than the LHC ("HE-LHC") would be a logical successor to the LHC itself, especially if its cost can be minimized by reusing a significant part of the CERN infrastructure like the existing tunnels and/or accelerators. The injector complex must however be extended to reach a beam energy of ~1.2 TeV and. in view of the time span of the HE-LHC project, the replacement of ageing accelerators can also be necessary. The main possible options are outlined together with their specificities.Comment: 2 pages, contribution to the EuCARD-AccNet-EuroLumi Workshop: The High-Energy Large Hadron Collider, Malta, 14 -- 16 Oct 2010; CERN Yellow Report CERN-2011-003, pp. 99-10

Status of the Nominal Proton Beam for LHC in the PS

The RF systems which are necessary for the generation of the nominal proton beam for the LHC in the PS Complex have been installed in the PSB and in the PS during the shutdown 97-98. This has permitted the complete set of longitudinal operations required by this beam to be tested and adjusted. The hardware status and the results achieved so far are summarised in this paper. The subjects of study, the foreseen improvements and the expected beam characteristics in 1999 are also described

RF Gymnastics in Synchrotrons

The RF systems installed in synchrotrons can be used to change the longitudinal beam characteristics. "RF gymnastics" designates manipulations of the RF parameters aimed at providing such non-trivial changes. Some keep the number of bunches constant while changing bunch length, energy spread, emittance or distance between bunches. Others are used to change the number of bunches. After recalling the basics of longitudinal beam dynamics in a hadron synchrotron, this paper deals with the most commonly used gymnastics. Their principle is described as well as their performance and limitations

Bunch merging and splitting techniques in the injectors for high energy hadron colliders

One problem in the design of TeV hadron colliders arises from the choice of the radio frequency. To produce economically the short bunches needed during collision, a high frequency (400 MHz or more) is essential. On the other hand, in the injector chain at lower energies, lower frequencies are generally preferred to alleviate space charge and instability problems and, partially also, for historical reasons. The classical solution is to transform the bunch structure by passing via a debunched beam state, during which the whole machine circumference becomes filled with particles and the beam is subjected to induced parasitic fields and is often prone to microwave instabilities. Bunch merging and bunch splitting have therefore been developed as alternative methods that allow the number of bunches to be changed without passing via that state. Bunch merging has been used in the CERN-PS since 1989 for the anti-proton production beam. The reverse process of bunch splitting was first proposed in the frame of the CERN injector complex for LHC, as a means of quasi-adiabatically changing the time structure of the beam, increasing the number of bunches from four at low energy in the PS Booster to 16 at high energy in the PS. When the CERN accelerator complex re-started in March 1998, this technique became a routine operation. New plans are now being considered to replace the debunching-rebunching process that is still needed at 26 GeV/c in the PS to generate the train of 84 bunches required by the SPS and LHC. The experience gained in the application of bunch merging and splitting techniques is reviewed in this paper together with the extensions now envisaged and the analysis of the expected advantages with respect to the more classical process of debunching-rebunching

Status of European Studies for a Neutrino Factory at CERN

Studies for a Neutrino Factory at CERN have made remarkable progress during the last year, supported by specialists from numerous laboratories in Europe and in close connection with teams looking at similar projects in the USA and in Japan. Although many options are still open, a reference scheme is pursued and work has advanced on many on its components. The status of these studies is described, as well as the future plans. Potential evolutions of the reference scheme and the possibility of a staged realisation are also commented upon

Scenarios for upgrading the LHC injectors

The presence of a powerful accelerator complex that could serve as injector has been instrumental in the decision to build the LHC at CERN. This existing complex has now confirmed its capability, having demonstrated that it is able to deliver beam with the nominal characteristics as well as numerous other types of beams which will be essential for tuning-in, commissioning and operating the future collider for physics in its first years. However it is also clear that the existing LHC injectors will not be able to deliver beam with the ultimate characteristics and that they suffer from reliability problems due to their age. An analysis has therefore been done by the working group in charge of "Proton Accelerators of the Future" (PAF) to determine a logical evolution of the accelerator complex, considering the needs of LHC and of the other potential future physics experiments at CERN. As a result, scenarios for a staged upgrade have been proposed, involving the progressive replacement of all the low energy accelerator

SPL at CERN

The existing complex of accelerators at CERN is capable to provide the Large Hadron Collider (LHC) with the beam required to reach its nominal characteristics. Higher performance injectors will however be necessary to exceed this limit and maximize the physics reach of the LHC. As a first step, the construction of a new 160 MeV H- linac (Linac4) has started, and the study of a 4 GeV Superconducting Proton Linac (SPL) is being pursued in view of submitting a project proposal by mid-2012. The basic design choices of the SPL are described, as well as its potential interest for other physics programmes. The goals and plans of the on-going study are explained

Longitudinal limitations in the PS complex for the generation of the LHC proton Beam

The nominal operating scheme for feeding LHC with protons [1] makes use of the PS injectors complex. Many new manipulations are used in the longitudinal phase plane. The radio-frequency systems of the PS Booster (PSB) operate on harmonics 1 and 2, harmonic 10 being used for controlled emittance blow-up during acceleration. The PS accelerates on harmonics 8 and 16. Debunching takes place at 26 GeV followed by rebunching on harmonic 84 (40 MHz) and bunch compression before ejection to the SPS. Although certainly capable of providing the nominal type of beam, these processes are marginal in terms of performance and have not all been experimentally demonstrated. These limitations are described together with possible improvements. New directions of investigation including the SPS are encouraged