Effect of Synchrotron Radiation in the Proposed 4-GeV Argonne Microtron
Synchrotron radiation in the sector magnets of the 4 GeV microtron designed at the Argonne National Laboratory produces a small but noticeable distortion of the closed orbits of the system and a very significant growth of the horizontal and longitudinal phase space emittances. Because of the small apertures in the three 25 meter linacs, it is important that the expected growth of the beam be calculated as accurately as possible. The dynamical problem has been solved using a computer program which follows the motions of individual electrons in the four dimensional horizontal and longitudinal phase space as they are accelerated in the system. In this paper the authors call attention to the fact that there are 3 long 28 m linac sections separated by sector magnets from 3 dispersion sections where the orbits for different energies are separated. The interaction of the linac rf systems with the synchrotron energy loss in the sector magnets produces different orbit effects in the downstream and upstream linac sector magnets. The average synchrotron radiation energy loss per sector magnet is given.
Final-focus system and collision schemes for a 5-TeV W-band linear collider
A 3-km long high-gradient W-band switched matrix linac may, in parallel channels, accelerate multiple electron and positron bunches to an energy of 2.5 TeV, with a tight control on the intra-bunch energy spread. In this report, we describe a final-focus system for such an accelerator, whose length is restrained by eliminating chromatic correction. The interaction point (IP) spot size is limited by synchrotron radiation in the last quadrupole (Oide effect). The energy loss due to beamstrahlung is optionally suppressed by combining bunches of opposite charge and colliding the neutral beams. We present two different high-luminosity multiple-collision schemes, which can provide a luminosity of up to 1035cm-2s-1, with only about 1 MW average beam power. In the first scheme, batches of equally-charged bunches are combined into superbunches which, possibly after charge compensation, are collided head-on with the opposing beam. In the second scheme, 25 charge-neutral electron-positron bunch pairs of one beam are each collided with 25 neutral bunch pairs of the other beam. These multiplexed collisions are facilitated by a crossing angle and by crab cavities upstream of the electron-positron combiner; however they also require focusing channels (e.g., a crystal) preserving IP beam size between the collision points, a difficult if not impossible construct. We describe the challenges posed by each approach.
Effect of Extended Fringing Fields on Ion-Focusing Properties of Deflecting Magnets
This paper presents the result of calculations on ion deflection and focusing in magnets that have realistic, extended fringing fields rather than sharply cutoff fringing fields. The most important effects of the change from sharp cutoff to extended fringing fields are (a) displacements of the beam center line at entrance and exit (a ``zeroth‐order'' effect), and (b) reduction of first‐order z‐direction (``vertical'') focusing. When the pole boundaries are curved or an effective curvature is caused by the proximity of pole‐piece corners, there are further first‐order effects on the trajectories. These effects can be minimized, and in practice made negligible, by correct centering of the beam relative to the pole‐piece corners at entrance and exit.