A possible redesign of the SLAC SLC damping rings

Abstract

rings. The energy is constrained by the required rotation of We describe a possible replacenaent for the SLC damp-tile electron polarization before injection into the ring, the ing rings that would generate beams with normalized imri-damping times are needed to damp the injected enfittances zontal emittances of'_q-= 9 x 10-6 m-rad when uncoupled; while operating at. 120 Hz, and /.he circumference is deterthis is more than three times smaller than tllat generated mined by' the size of the damping ring vaults. Thus, thore by the current rings. The primary difference between the are only three possible ways of reducing the emit.lances: (1) new design and the current ring is the arc cell structure; the use damping wigglers to decrease both the damping times insertion regions, the kickers, and the RF are essentially and the emittances, (2) use combined function bending unchanged. The new cell uses a single combined rune-magnets to change the horizontal damping partition, also tion bending magnet, roughly 70 cna in length, to replace decreasing the damping times and the emittances, and (3) the two bends, defocusing quadrupole, and defocusing sex-use a more efficient, cell structure with smaller dispersion tupoles in the current FODO cell; the focusing quadrupole to reduce the quantum excitation and thus the emittance. and sextupoles, used in the current cell, are also used in Unfortunately, wigglers are not very effective at rethe new structure. The length of the new cell is identical ducing the emittance. Roughly four meters of 5T superto that of the current cell and thus nine of these new cells conducting wiggler with a 15 cm period would be needed would simply replace the nine FODO cells in each arc of to reduce the damping time and emittance by a factor of lhc rings, two. In addition to the severe operational difficulties with such a device, tile wigglers would incre_e the longitudinal ' "

Autophasing and lattice scaling in high energy linear accelerators

“…The dynamics of these processes have been studied in numerous Refs. [2][3][4][9][10][11][12][13][14]. We will consider the first order solution of the equation of motion which assumes that the driving particles (bunches) do not feel transverse wakefields and undergo free betatron oscillations with nonzero initial beam offset.…”

“…Then, neglecting the chromatic phase advance and quickly varying terms, the autophasing condition in the nth cell will read as [3] …”

“…For comparison we cite also the autophasing solution for beta scaled as the squared root of energy [3] …”

“…The well-known scaling of the betatron wave number (beta function), with constant phase advance per cell, satisfies the autophasing conditions in each FODO cell (F focusing quadrupole, D defocusing quadrupole, O drift space) if the beta function grows with the square root of the energy along the linear accelerator [3]. If multiple bunches are used in the linear collider to increase the luminosity, the long range wakefields become the source of the multibunch beam instability [4].…”

Plans to increase source brightness of NSLS X-ray ring

“…Both before and after the skew quadlupoles were adjusted to reduce the vertical orbit shifts, the calculated vertical emittance was found to exhibit the approximate dependence Q(A) x .002 < Ay2(m) , 4 (ml 'HH, >, where < ?& > is the average value of the CourantSnyder invariant in the bending magnets. In reference [7] the author shows that < %, > is approximately equal to 2 < $ >, so for the X-Ray ring (p = 6.9m and y = 5057) the v&tical emittance from dispersion is given by…”