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
INFN-Ferrara, Ferrara, Italy
IHEP Protvino, Protvino, Moscow Region, Russia
PNPI, Gatchina, Leningrad District, Russia
The T-980 bent crystal collimation experiment at the Tevatron has recently acquired substantial enhancements. First, two new crystals - a 16-strip one manufactured and characterized by the INFN Ferrara group and a quasi-mosaic crystal manufactured and characterized by the PNPI group. Second, a two plane telescope with 3 high-resolution pixel detectors per plane along with corresponding mechanics, electronics, control and software has been manufactured, tested and installed in the E0 crystal region. The purpose of the pixel telescope is to measure and image channeled (CH), volume-reflected (VR) and multiple volume-reflected (MVR) beam profiles produced by bent crystals. Third, an ORIGIN-based system has been developed for thorough analysis of experimental and simulation data. Results of analysis are presented for different types of crystals used from 2005 to present for channeling and volume reflection including pioneering tests of two-plane crystal collimation at the collider, all in comparison with detailed simulations.
BNL, Upton, Long Island, New York, USA
CERN, Geneva, Switzerland
CINVESTAV, Mérida, Mexico
A major concern for the implementation of crab crossing in a future high-luminosity LHC (HL-LHC) is machine protection in an event of a fast crab-cavity failure. Certain types of abrupt crab-cavity phase and amplitude changes are simulated to characterize the effect of failures on the beam and the resulting particle-loss signatures. The time-dependent beam loss distributions around the ring and particle trajectories obtained from the simulations allow for a first assessment of the resulting beam impact on LHC collimators and on sensitive components around the ring. The simulation results are used to derive tolerances on the maximum rate of change in crab-cavity phase and amplitude which can be allowed with regard to machine safety.
Fermilab, Batavia, USA
CERN, Geneva, Switzerland
The LHC collimation upgrade foresees additional collimators installed in dispersion suppressor regions. To obtain the necessary space for the collimators, a solution based on the substitution of LHC main dipoles for stronger dipoles is being considered. CERN and FNAL have started a joint program to demonstrate the feasibility of Nb3Sn technology for this purpose. The goal of the first phase is the design and construction of a 2-m long single-aperture demonstrator magnet with a nominal field of 11 T at 11.85 kA with 20% margin. This paper describes the magnetic and mechanical design of the demonstrator magnet and summarizes its design parameters.
ORNL, Oak Ridge, Tennessee, USA
UMAN, Manchester, United Kingdom
Euclid TechLabs, LLC, Solon, Ohio, USA
LETI, Saint-Petersburg, Russia
CERN, Geneva, Switzerland
The current status of ILC and CLIC concepts require additional research on wakefield reduction in the collimator sections. New materials and new geometries have been considered recently*. Dielectric collimators for the CLIC Beam Delivery System have been discussed with a view to minimize the BDS collimation wakefields**. Dielectric collimator concepts for the linear collider are presented in this paper; cylindrical and planar collimators for the CLIC parameters have been considered, and simulations to minimize the beam impedance have been performed. The prototype collimator system is planned to be fabricated and experimentally tested at Facilities for Accelerator Science and Experimental Test Beams (FACET) at SLAC.
*J.R.Lopez. ILC-CLIC Beam Dynamics Workshop. CERN, Geneva, 23-25 June, 2009.
**R. Tomas. ILC-CLIC Beam Dynamics Workshop. CERN, Geneva, 23-25 June, 2009.
CLASSE, Ithaca, New York, USA
The relatively large horizontal emittance εx of CESR, an electron storage ring designed for colliding beam operation, does not limit its performance after its conversion into a frontier x-ray source, CESR-X. Its flexible lattice optics permits the production of hard x-ray beams competitive with any in the world by exploiting the fact that the conditions required for Liouville’s theorem to be valid are applicable to charged particle focusing but not to x-ray focusing. X-ray focusing (with currently available devices) causes an increase in electron beam “effective” emittance that would prevent even a fourth generation source, such as an ERL, from outperforming the existing CESR-X ring as a source of hard x-rays. As x-ray focusing devices are improved this will become less true and it will be important for CESR-X to keep pace. A plan for doing this is described.