Accelerator technology for the VLHC

Accelerator technologies useful or necessary for the construction of the VLHC (Very Large Hadron Collider) are discussed. The VLHC workshop on this subject (held in February 1999 at Jefferson Lab) is summarized. (6 refs)

Ion Trapping in the Accumulator

The beam space charge (- for {bar p}'s) will attract positive ions. In the absence of additional fields (clearing electrodes, e.g.) these ions will be trapped in the beam potential well. The depth of this potential well has been calculated for some geometries relevant for the accumulator

Common Mode Rejection of Stack Tail Kicker Hybrids

The betatron heating of the core is commonly agreed to be due to a undesired difference mode in the kickers. This could be due to tolerances and mistakes in the kickers or in the hydrids which ideally drive the kickers in the sum mode. The purpose of this note is to estimate the effect of the latter. The hydrids, by the nature of their construction, have systematic errors. These errors appear to be larger than the errors which come from construction tolerances

Stability of Coastin Beams in the Debuncher

The stability of high intensity beams has been a matter of some concern. While anti-proton operation uses beam currents of 10 a or less, it is sometimes useful to have proton beams with currents of the order of 1 ma and narrow (booster sized) momentum spreads. This note describes calculations of what can be expected for coasting beam instabilities and, in particular, the effect of the (high impedance) 53 MHz cavities. This note specifically does not describe transverse instabilities, bunched beam instabilities, or turbulence in the debunching process. The stability limit can be calculated using standard formulae (van der Meer CERN/PS/AA/80-4 and many others). The result of this calculation is the 'stability plot' shown in figure 1a. This calculation assumes a 1 ma beam with a {Delta}p ({sigma}) of 2 MeV/c. The curve (allowed impedance) scales inversely with beam current and {Delta}p{sup 2}. The momentum spread was assumed to be gaussian. Figures 1b and 1c are the same plot but with different scales. The interpretation of this plot is that if the impedance of any device (or devices) is outside this curve, then the assumed beam distribution is unstable. More rigorously one can make a so-called 'Nyquist plot' where one plots Z{sub w}(w)/Z{sub b}(w) where Z{sub w} is some wall impedance and Z{sub b} is the beam response (or beam impedance) shown in figure 1. These Nyquist plots are shown in figures 2abcd for different cavity tunes. Figure 2a shows the Nyquist plot for the 1 ma of beam assumed above assuming only 1 cavity which is tuned to resonance. The cavity has a shunt impedance of 1.8M{Omega} and a Q of 10,000. The assumed beam distribution is unstable if the curve circles the point (1,0) {approx} quite close in figure 2a. Figure 2b is the same except that 6 cavities are assumed. In figure 2c the 6 cavities are tuned 100 kHz below the beam revolution frequency (capacitive). In figure 2d they are tuned 100 kHz above (inductive). The inductive tuning is preferred, but either case should be stable. The standard theory of the stability of coasting beams indicates that the high impedance 53 MHz Debuncher cavities do not upset the stability of moderate beam currents (1 ma) and narrow momentum spreads ({sigma} = 2 Mev) provided that they are detuned

Beam instabilities in Very Large Hadron Collider

The Very Large Hadron Collider (VLHC) is a supercon-ducting proton-proton collider with approximately 100 TeV cm and approximately 10{sup 34} s{sup -1}cm{sup -2} luminosity [1]. Currently, beam dynamics in this future accelerator is the subject of intensive studies within the framework of the US-wide VLHC R&D program. This presentation sum-marizes recent developments in the field. Besides general discussion on relevant VLHC parameters, we consider various beam instabilities and ways to avoid them. Finally, we outline possibilities for theoretical and experimental R&D

The Fermilab Proton-Antiproton Collider Upgrades

The plans for increases in the Tevatron proton-antiproton collider luminosity in the near future (Run II) and the more distant future (TeV33) are described. While there are many important issues, the fundamental requirement is to produce more antiprotons and to use them more efficiently

Search for antiproton decay at the Fermilab Antiproton Accumulator

A search for antiproton decay has been made at the Fermilab Antiproton Accumulator. Limits are placed on thirteen antiproton decay modes. The results include the first explicit experimental limits on the muonic decay modes of the antiproton, and the first limits on the decay modes e- gamma gamma, and e- omega. The most stringent limit is for the decay mode pbar-> e- gamma. At 90% C.L. we find that tau/B(pbar-> e- gamma) > 7 x 10^5 yr. The most stringent limit for decay modes with a muon in the final state is for the decay pbar-> mu- gamma. At 90% C.L. we find that tau/B(pbar-> mu- gamma) > 5 x 10^4 yr.Comment: 20 pages, 8 figures. Submitted to Phys. Rev. D. Final results on 13 channels (was 15) are presente