The Stanford Linear Collider (SLC) is the first and only high-energy e/sup +/e/sup -/ linear collider in the world. Its most remarkable features are high intensity, submicron sized, polarized (e/sup -/) beams at a single interaction point. The main challenges posed by these unique characteristics include machine-wide emittance preservation, consistent high intensity operation, polarized electron production and transport, and the achievement of a high degree of beam stability on all time scales. In addition to serving as an important machine for the study of Z/sup 0/ boson production and decay using polarized beams, the SLC is also an indispensable source of hands-on experience for future linear colliders. Each new year of operation has been highlighted with a marked improvement in performance. The most significant improvements for the 1994-95 run include new low impedance vacuum chambers for the damping rings, an upgrade to the optics and diagnostics of the final focus systems, and a higher degree of polarization from the electron source. As a result, the average luminosity has nearly doubled over the previous year with peaks approaching 10/sup 30/ cm/sup -2/ s/sup -1/ and an 80% electron polarization at the interaction point. These developments as well as the remaining identifiable performance limitations will be discussed.

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The Stanford Linear Collider

The Stanford Linear Collider (SLC) was the first prototype of a new type of accelerator, the electron-positron linear collider. Many years of dedicated effort were required to understand the physics of this new technology and to develop the techniques for maximizing performance. Key issues were emittance dilution, stability, final beam optimization and background control. Precision, non-invasive diagnostics were required to measure and monitor the beams throughout the machine. Beam-based feedback systems were needed to stabilize energy, trajectory, intensity and the final beam size at the interaction point. A variety of new tuning techniques were developed to correct for residual optical or alignment errors. The final focus system underwent a series of refinements in order to deliver sub-micron size beams. It also took many iterations to understand the sources of backgrounds and develop the methods to control them. The benefit from this accumulated experience was seen in the performance of the SLC during its final run in 1997-98. The luminosity increased by a factor of three to 3*10**30 and the 350,000 Z data sample delivered was nearly double that from all previous runs combined.

SLC Final Performance and Lessons

The minimum /spl beta/ achievable at the interaction point (/spl beta/*) with the current design of the SLC final focus is limited to /spl sim/5 mm by third order optical aberrations, most notably the U/sub 1266/ and U/sub 3466/ terms (using the notation of K. Brown). A new lattice is presented which effectively zeros these terms. The remaining third order terms which accrue from the interleaved sextupole pairs in the chromatic correction section (CCS) can be cancelled by the inclusion of five octupoles (two in the CCS, and three in the final telescope). The resulting final focus system is corrected to third order for any usable range of /spl beta/* (given the constraints on the beam divergence at the interaction point). The potential luminosity obtainable from such a system is also presented. >

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Third-order corrections to the SLC final focus

The 1992 running cycle of the Stanford Linear Collider (SLC) showed that the orientation of the electron polarization vector at the interaction point was very sensitive to the vertical orbit in the north collider arc. We point out the reason for this sensitivity-the spin tune is equal to the vertical betatron tune. We devise a scheme of closed vertical orbit bumps which provide arbitrary manipulations of the polarization vector at the IP. We have developed an analytical model for the tuning of this 'arc spin rotator' and have performed a detailed numerical analysis to show its effectiveness. We present experimental results. >

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The north arc of the SLC as a spin rotator

The Stanford Linear Collider (SLC) was recently converted to flat beam operation (/spl gammaspl epsivsub x/=10 /spl gammaspl epsivsub y/), producing a factor of two increase in luminosity. In this paper we review the results of flat beam studies in the SLC Linac. In summary, the injected beams from the damping rings had invariant horizontal emittances as low as 30 mm-mrad and invariant vertical emittances as low as 2 mm-mrad. The emittances measured at the end of the linac after tuning for 3/spl times/10/sup 10/ particles are about 5 to 8 mm-mrad vertically and 40 to 50 mm-mrad horizontally. Flat beam operation began 3/17/93. >

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Flat beam studies in the SLC Linac

The Stanford Linear Collider was designed to operate with round beams; horizontal and vertical emittance made equal in the damping rings. The main motivation was to facilitate the optical matching through beam lines with strong coupling elements like the solenoid spin rotator magnets and the SLC arcs. Tests in 1992 showed that 'flat' beams with a vertical to horizontal emittance ratio of around 1/10 can be successfully delivered to the end of the linac. Techniques developed to measure and control the coupling of the SLC arcs allow these beams to be transported to the Interaction Point (IP). Before flat beams could be used for collisions with polarized electrons, a new method of rotating the electron spin orientation with vertical arc orbit bumps [4] had to be developed Early in the 1993 run, the SLC was switched to 'flat' beam operation. Within a short time the peak luminosity of the previous running cycle was reached and then surpassed. The average daily luminosity is now a factor of about two higher than the best achieved last year. In the following we present an overview of the problems encountered and their solutions for different parts of the SLC. >

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M. Hildreth

Papers

Flat beams in the SLC