BNL, Upton, Long Island, New York
Operational experience on crossing RHIC transition as well as observed beam dynamics effects are described. The techniques to provide the successful transition crossing without beam losses and deterioration of the beam quality in both transverse and longitudinal plane are reviewed. Presently the ion beam intensity is limited by the transverse instability happenning at the transition region. It was observed that the threshold of the instability was significantly affected by the presence of the electron cloud. The results of recent studies of the intensity limiting instability are presented.
Fermilab, Batavia, Illinois
If large enough the beam space charge strongly affects the beam stability in a circular accelerator. It results in a separation of coherent and incoherent tunes and, consequently, instability. Effects of space charge on the beam stability are considered in application to Fermilab Booster, Main injector and Recycler.
Fermilab, Batavia, Illinois
Obit Response Matrix (ORM) Fit method has been successfully used to calibrate linear optics at Recycler Ring at Fermilab. The linear model of the Recycler optics ring has been significantly improved. Based on the build-up model, lattice measurement of the Recycler ring has been done several times, each after some magnets move and the tunes change. Large beta-wave(~20%) has been found in horizontal plane after the working point was moved from (0.424,0.434) to (0.456, 0.467) for the reason of lowering the beam instabilities. The source of the beta-wave, and the correction will be presented in this paper. In addition, we found an easy way to extend the tuning range in the recycler lattice. A new application program for adjusting the tunes operationally was introduced and the measured results will be presented.
GSI, Darmstadt
Resonant effects caused by space charge may occur in circular as well as linear accelerators for high intensity. In the present work we focus on the so-called space charge structure resonances in 2D approximation, where the driving force is induced by space charge only (emittance exchange, fourth and sixth order structure resonances) and show that they can be described by a common class of scaling laws. A distinctive feature is the presence or absence of trapping of particles, which is also reflected in the power of the scaling law. An important requirement is the fully self-consistent modeling, which describes correctly the evolution of beam core as well as halo.
BNL, Upton, Long Island, New York
Intra-beam scattering (IBS) is the limiting factor of the luminosity lifetime for RHIC operation with heavy ions. Over the last few years the process of IBS was carefully studied in RHIC with dedicated IBS measurements and their comparison with the theoretical models. Recently, in order to suppress transverse IBS growth, a new lattice was designed and implemented in RHIC, which lowered the average arc dispersion by 30%. This lattice became operational during RHIC Run-8. We review the IBS suppression mechanism, IBS measurements before and after the lattice change, and comparisons with predictions.
ORNL, Oak Ridge, Tennessee
Beam phase synchronous oscillations and the damping curves of the SNS linac are investigated with linac models and measured with all the linac beam phase monitors. It provides a useful beam diagnostic solution to detect RF cavity phase and/or field amplitude errors in the linac with many independently phased cavities. And the phase damping curves predicted in the longitudinal model could also be utilized to analyze the longitudinal lattice of the superconducting linac, in which each cavity gradient varies widely from the nominal design and smooth the beam longitudinal focusing is very important to preserve beam emittance.
ORNL, Oak Ridge, Tennessee
Most recent beam dynamic studies of the Spallation Neutron Source linac, including the major beam loss reduction efforts in the normal conducting (nc) linac and in the superconducting linac (SCL), simulations and measurements of the longitudinal beam halos and the longitudinal acceptance at the entrance of the SCL are discussed. Oscillation of beam centroid around the linac synchronous phase and the beam phase adiabatic damping curves in the SNS linac are investigated with the linac longitudinal models and measured with all the linac beam phase monitors.
IAP, Frankfurt am Main
GSI, Darmstadt
The 'Combined Zero-Degree Structure' ('Kombinierte Null Grad Struktur - KONUS') beam dynamics concept is described in detail. A KONUS period consists of a quadrupole triplet or a solenoid lens, a rebuncher section at negative synchronous phase and a multi cell zero degree synchronous particle main acceleration section. This concept is especially effective when applied for accelerator designs using H-mode resonators with ‘slim’ drift tubes which carry no focusing elements. The definition and typical ranges of KONUS lattice parameters are discussed on a general level, as well as on the basis of examples for realized or planned high current accelerators, like the GSI High Current Injector (HSI), the 70 mA, 3-70 MeV Proton Injector for the FAIR Facility and our proposal of a 125 mA D+, 5-40 MeV superconducting CH-DTL section for the International Fusion Materials Irradiation Facility (IFMIF).
Soreq NRC, Yavne
In this study we examine a lattice for the SARAF superconducting (SC) linac at the low velocity β range. The SC Half Wave Resonator cavities in the first cryostat have been optimized for a geometric β=0.09 and hence the β=0.0567 ions coming from the RFQ are mismatched. We developed a semi adiabatic tuning method for the low β side of the SC linac. The guidelines were derived from a study of two linac lattices that were considered for the SARAF 40 MeV proton and deuteron linac, extended up to 60 MeV for the low energy part of the EURISOL driver. Simulations were made using the TRACK and GPT codes. The lattices were tested for energy gain along the linac, emittance growth and acceptance. Further, error runs in GPT using a tail emphasis technique to enhance statistics by focusing on the bunch tail allowed us to examine compatibility of the lattices with hands-on maintenance requirements. We find our study relevant for other linacs that start with SC cavities right after the RFQ, such as SPIRAL2, and maybe IFMIF too, which are designed to start with similar β mismatch at the low β range.
CERN, Geneva
UPC, Barcelona
A 50 GeV proton synchrotron machine to replace the current PS (PS2) is foreseen in the framework of the LHC complex upgrade. For high intensity beams, losses constitute a great concern in terms of hands-on maintenance and radioactivation. To minimize the uncontrolled losses all around the ring a collimation system is required. Lattice design and collimation studies are carried out in parallel in order to optimize the cleaning efficiency. To this end the robustness of the system is tested for different lattice configurations against orbit errors and optics distortions.
ORNL, Oak Ridge, Tennessee
The paper describes a parallel flow of the Spallation Neutron Source (SNS) linac and ring commissioning and development of commissioning tools. An evolution of the physics control system, its features, problems and solutions are presented. The peculiarities of the SNS project such as a collaboration between six Department of Energy laboratories, an absence of previous experience in large accelerator construction and operation in Oak Ridge National Laboratory, an original upper level of a control system (physics applications) and their effect on SNS commissioning are discussed. SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
CERN, Geneva
BNL, Upton, Long Island, New York
In view of the CERN Proton Synchrotron replacement with a new ring (PS2), a detailed optics design is undertaken following several options, which cross or avoid transition. The different lattices are compared with respect to their linear optics flexibility, acceptance and chromatic properties. The effect of magnet misalignments in the beam orbit and linear optics functions are reviewed and correction schemes are proposed. Finally, the different lattice options are compared with respect to single particle non-linear dynamics.
BNL, Upton, Long Island, New York
ORNL, Oak Ridge, Tennessee
The charge to this working group was the following:
- Summarize the state of the art in H- charge-exchange injection.
- Summarize recent developments and future possibilities for novel injection techniques.
- Summarize the problems encountered, the needs for further development and improvements in injection and extraction of high-intensity beams.
- Summarize the state-of-the art in collimation system design.
- Summarize the status of benchmarking of collimation system efficiency and performance.