Fermilab, Batavia, USA
The performance of the Tevatron collider demonstrated continuous growth over the course of Run II, with the peak luminosity reaching 4·1032 cm-2 s-1 and the weekly integration rate exceeding 70 pb-1. This report presents a review of the most important advances that contributed to this performance improvement, including beam dynamics modeling, precision optics measurements and stability control, implementation of collimation during low-beta squeeze. Algorithms employed for optimization of the luminosity integration are presented and the lessons learned from high-luminosity operation are discussed. Studies of novel accelerator physics concepts at the Tevatron are described, such as the collimation techniques using crystal collimator and hollow electron beam, and compensation of beam-beam effects.
Fermilab, Batavia, USA
At the Tevatron collider, we studied the feasibility of suppressing the antiproton head-on beam-beam tune spread using a magnetically confined 5-keV electron beam with Gaussian transverse profile overlapping with the circulating beam. When electron cooling of antiprotons is applied in regular Tevatron operations, the head-on beam-beam effect on antiprotons is small. Therefore, we first focused on the operational aspects, such as beam alignment and stability, and on fundamental observations of tune shifts, tune spreads, lifetimes, and emittances. We also attempted two special collider stores with only 3 proton bunches colliding with 3 antiproton bunches, to suppress long-range forces and enhance head-on effects. We present here the results of this study and a comparison between numerical simulations and observations, in view of the planned application of this compensation concept to RHIC.
Fermilab, Batavia, USA
Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable material damage. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and tested at Fermilab for this purpose. It was installed in one of the Tevatron electron lenses in the summer of 2010. We present the results of the first tests of the hollow-beam collimation concept on individual 980-GeV antiproton bunches in the Tevatron.
Fermilab, Batavia, USA
Ionization profile monitors (IPMs) are used in the Fermilab Main Injector (MI) for injection lattice matching and to measure transverse emittance of the beam during acceleration. The IPMs provide a periodic, non-destructive means for emittance measurements where other techniques are not applicable. As Fermilab is refocusing its attention on the intensity frontier, non-intercepting diagnostics such as IPMs are expected to become even more important. This paper gives an overview of the operational use of IPMs for emittance measurements and injection lattice matching measurements at Fermilab, and summarizes the future plans.
Fermilab, Batavia, USA
The brightness of the antiproton beam in Fermilab’s 8 GeV Recycler ring is limited by a transverse instability. This instability has occurred during the extraction process to the Tevatron for large stacks of antiprotons even with dampers in operation. This paper describes observed features of the instability, introduces the threshold phase density to characterize the beam stability, and finds the results to be in agreement with a resistive wall instability model. Effective exclusion of the longitudinal tails from Landau damping by decreasing the depth of the RF potential well is observed to lower the threshold density by up to a factor of two.
MPI-K, Heidelberg, Germany
JINR/DLNP, Dubna, Moscow region, Russia
Aarhus University, Aarhus, Denmark
JINR, Dubna, Moscow Region, Russia
The University of Liverpool, Liverpool, United Kingdom
Cockcroft Institute, Warrington, Cheshire, United Kingdom
At present, the only place in the world where experiments utilising low-energy antiprotons can be performed is the AD at CERN. The MUSASHI trap, as part of the ASACUSA collaboration, enables access to antiproton energies in the order of a few hundreds of eV. Whilst MUSASHI produces cutting-edge research, the available beam quality and luminosity is not sufficient for collision experiments on the level of differential cross sections. A small electrostatic ring, and associated electrostatic acceleration section, is being designed and developed by the QUASAR Group. It will serve as a prototype for the future ultra-low energy storage ring (USR), to be integrated at the facility for low-energy antiproton and ion research (FLAIR). This small AD recycler ring will be unique due to its combination of size, electrostatic nature and energy of the circulating particles. In this contribution, the design of the ring is described and details about the injection section are given.
BSU, Minsk, Belarus
Fermilab, Batavia, USA
In Fermilab’s electron cooler, a 0.1A, 4.3MeV DC electron beam propagates through the 20 m cooling section, which is immersed in a weak longitudinal magnetic field. A proper adjustment of 200 dipole coils, installed in the cooling section for correction of the magnetic field imperfections, can create a helix-like trajectory with the wavelength of 1-10 m. The longitudinal cooling force is measured in the presence of such helices at different wavelengths and amplitudes. The results are compared with a model calculating the cooling force as a sum of collisions with small impact parameters, where the helical nature of the coherent angle is ignored, and far collisions, where the effect of the coherent motion is neglected. A qualitative agreement is found.
FZJ, Jülich, Germany
BINP SB RAS, Novosibirsk, Russia
FZJ, Jülich, Germany
Cockcroft Institute, Warrington, Cheshire, United Kingdom
MPI-K, Heidelberg, Germany
UNM, Albuquerque, New Mexico, USA
The University of Liverpool, Liverpool, United Kingdom
Ions offer an increased precision in radiotherapy due to their specific depth-dose properties. This precision can only be fully exploited if exact knowledge of the particle beam properties, as well as the exact range of the particles in the inhomogeneous target, is available. The QUASAR Group has addressed the key issues in a number of different ways: Using a monolithic active pixel sensor, designed for dead time-free operation, we have developed a beam monitoring system capable of monitoring pulsed and continuous beams at typical therapeutic energies and intensities in real time during patient treatment; using a non-intrusive detector system based on the VELO detector, we will measure variations in beam properties without intersecting the beam core altogether; using liquid ionization chambers, we aim at obtaining information on the biological quality of the beam; using a simple set-up based on a silicon pixel detector, developed for the ALICE experiment, we have demonstrated the feasibility of detecting the distal edge of the Bragg peak in antiproton beams by detecting the pions resulting from pbar-nucleon annihilations. This paper gives an overview of these studies.