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Attaining high luminosity in linear e sup + e sup minus colliders

Description: The attainment of high luminosity in linear colliders is a complex problem because of the interdependence of the critical parameters. For instance, changing the number of particles per bunch affects the damping ring design and thus the emittance; it affects the wakefields in the linac and thus the momentum spread; the momentum spread affects the final focus design and thus the final {beta}*; but the emittance change also affects the final focus design; and all these come together to determine the luminosity, disruption and beamstrahlung at the intersection. Changing the bunch length, or almost any other parameter, has a similar chain reaction. Dealing with this problem by simple scaling laws is very difficult because one does not know which parameter is going to be critical, and thus which should be held constant. One can only maximize the luminosity by a process of search and iteration. The process can be facilitated with the aid of a computer program. Examples can then be optimized for maximum luminosity, and compared to the optimized solutions with different approaches. This paper discusses these approaches.
Date: November 1, 1990
Creator: Palmer, R.B.
Partner: UNT Libraries Government Documents Department

Wakefield measurements of SLAC linac structures at the Argonne AATF

Description: Damped and detuned linac structures designed to minimize the effects of wakefields excited by e{sup {plus minus}} bunch trains in future linear colliders are presently under investigation at SLAC. This paper describes the results of measurements of both longitudinal and transverse wakefields performed at the ANL Advanced Accelerator Test Facility with two SLAC-built X-Band disk-loaded waveguides: a conventional 30-cavity long constant-impedance structure and a non-conventional 50-cavity long structure along which the iris and spacer diameters have been varied so as to stagger-tune the HEM{sub 11} mode frequency by 37%. The results are shown to be in excellent agreement with computations made by KN7C, TRANSVRS, TBCI, and LINACBBU. 8 refs., 5 figs.
Date: May 1, 1991
Creator: Wang, J.W.; Loew, G.A. (Stanford Linear Accelerator Center, Menlo Park, CA (USA)); Simpson, J.; Chojnacki, E.; Gai, W.; Konecny, R. et al.
Partner: UNT Libraries Government Documents Department

Tangent map analysis of the beam-beam interaction

Description: We studied the tangent map of the beam-beam interaction and found no evidence of beam-beam instability for /epsilon/ = 0.04. Tracking study with tune modulation shows however large emittance growth due to the sum resonances. The emittance growth is due to the multiple crossing of the sum resonances. 12 refs., 7 figs.
Date: January 1, 1989
Creator: Lee, S.Y. & Tepikian, S.
Partner: UNT Libraries Government Documents Department

Collimation systems in the next linear collider

Description: Experience indicates that beam collimation will be an essential element of the next generation e{sup +}E{sup {minus}} linear colliders. A proposal for using nonlinear lenses to drive beam tails to large amplitudes was presented in a previous paper. Here we study the optimization of such systems including effects of wakefields and optical aberrations. Protection and design of the scrapers in these systems are discussed. 9 refs., 7 figs.
Date: February 1, 1991
Creator: Merminga, N.; Irwin, J.; Helm, R. & Ruth, R.D.
Partner: UNT Libraries Government Documents Department

On asymmetric collisions with large disruption parameters

Description: Collisions between a weak electron bunch and a strong positron bunch are studied within a flat model. Electrons are tracked through the transverse space charge field of the positron bunch, and it is shown that positrons in a storage ring may remain stable after asymmetric collisions with a weak electron bunch in spite of large values of the electron disruption parameter. The plasma oscillations that affect collisions with large disruption parameters may be suppressed by properly matching the electrons. 8 refs., 5 figs.
Date: June 1, 1990
Creator: Heifets, S.A.; Krafft, G.A. & Fripp, M.
Partner: UNT Libraries Government Documents Department

Limitations on anti p-p luminosity with direct injection and stacking of antiprotons

Description: If protons of very high energy impinge on a target, a large part of the resulting antiprotons are sufficiently collimated to be injectible into a stacking and accelerating ring. They can then be stacked and injected into the main proton accelerator so as to produce anti p-p collisions without low energy antiproton cooling. A scheme is presented for the VBA, where 20 TeV protons produce 9 x 10/sup -4/ antiprotons per proton at 100 GeV, which are then stacked, accelerated to 1 TeV, and injected into the main ring. With 16 proton pulses of 10/sup 15/ protons, one obtains a luminosity of the order of 10/sup 32/ cm/sup -2/ sec/sup -1/ with a beam-beam tune shift of 10/sup -3/ per interaction region. The beams are bunched into 1000 bunches; the orbits are separated by means of relatively modest electostatic electrodes.
Date: January 1, 1979
Creator: Courant, E D & Teng, L C
Partner: UNT Libraries Government Documents Department

Plasma compensation effects with relativistic electron beams

Description: A sufficiently dense plasma can neutralize the current of a high energy lepton beam propagating through it. We have studied an e/sup +/-e/sup /minus// linear collider design with this plasma compensation and found that high luminosities can be obtained without going to nanometer beam sizes currently being discussed. We have also studied the consequence of compensation on B-factory design. One severe limitation on such plasma based device which has not been thoroughly examined is the background due to the interaction of the high energy beams with the plasma ion nuclei. 8 refs., 1 fig., 1 tab.
Date: March 1, 1989
Creator: Autin, B.; Sessler, A.M. & Whittum, D.H.
Partner: UNT Libraries Government Documents Department

Quantum effects in linear collider scaling laws

Description: Compared to classical calculations, quantum corrections greatly reduce the radiation emitted when the e/sup +/ and e/sup -/ beams collide in a linear collider. This allows a given luminosity to be obtained with much lower beam powers by making the beam size smaller.
Date: February 1, 1985
Creator: Himel, T. & Siegrist, J.
Partner: UNT Libraries Government Documents Department

Accelerator prospects for photon-photon physics

Description: This paper provides an overview of the accelerators in the world where two-photon physics could be carried out in the future. The list includes facilities where two-photon physics is already an integral part of the scientific program but also mentions some other machines where initiating new programs may be possible.
Date: May 1, 1992
Creator: Hutton, A.
Partner: UNT Libraries Government Documents Department

Depolarization due to beam-beam interaction in electron-positron linear colliders

Description: We investigate two major mechanisms which induce depolarization of electron beams during beam-beam interaction in linear colliders. These are the classical spin precession under the collective field of the oncoming beam, and the spin-flip effect from beamstrahlung. Analytic formulas are derived for estimating these depolarization effects. As examples, we estimate the depolarization in the Stanford Linear Collider (SLC) and a possible future TeV linear collider (TLC). The effects are found to be negligibly small for SLC and not very large for TLC. 7 refs., 1 fig.
Date: September 1, 1988
Creator: Yokoya, Kaoru & Chen, Pisin
Partner: UNT Libraries Government Documents Department

Controlling multibunch beam breakup in TeV linear colliders

Description: To obtain luminosities near 10TUcm/sup /minus/2/sec/sup /minus/1/ in a TeV linear collider, it will probably be essential to accelerate many bunches per RF fill in order to increase the energy transfer efficiency. In this paper we study the transverse dynamics of multiple bunches in a linac, and we examine the effects of several methods of controlling the beam blow-up that would otherwise be induced by transverse dipole wake fields. The methods we study are: damping the transverse modes, adjusting the frequency of the dominant transverse modes so that bunches may be placed near zero-crossings of the transverse wake, and bunch-to-bunch variation of the transverse focusing. We study the utility of these cures in the main linacs of an example of a TeV collider. 16 refs., 4 figs., 2 tabs.
Date: January 1, 1989
Creator: Thompson, K.A. & Ruth, R.D.
Partner: UNT Libraries Government Documents Department