Operating Experience The Stanford Two-Mile Linear Accelerator has been

The purpose of this paper is to describe recent developments at SLAC which have contributed to improvements in beam operation. The paper will be divided into two parts. The first will summarize overall beam performance and operational efficiency in delivering beams to various experiments. The second will be devoted to specific developments such as the achievement of higher energies, increasingly narrow energy spectra, higher beam breakup current thresholds, chopped beams and improvements in pulse-to-pulse operation. The discussion will include a description of various new pulsed devices such as pulsed quadrupoles, improvements in the positron source and new beam loading measurements obtained for very short pulses. Operating Experience The Stanford Two-Mile Linear Accelerator has been in operation since April, 1966 and has been engaged in physics research since November, 1966. A general trend during the past nine quarters has been an increase in the fraction of the available shifts devoted to particle physics research and a decrease in the fraction used for machine physics. An operations summary giving the percentages of manned operating time devoted to particle physics and to machine physics and the percentages required to satisfy various functions and contingencies is shown in Table I. Fortunately, it has been possible to reduce the non-productive portion of the manned hours in a reasonably steady manner during operations to date. Table II is a display of machine operations giving the actual hours devoted to productive and non-productive categories of work. Because of multiple-beam cpera-tions whereby several experiments can be conducted simultaneously , the total experimental hours exceed the 'total beam hours by a factor which has increased more or less steadily during the past six quarters. In the most recent quarter reported this factor is 3.4. Performance and life of the SLAC high power klys-trons are reported in a separate report1 to this conference. At this date, 122 of the 245 tubes attached to the accelerator still perform satisfactorily after 10,000 hours of operation. Mean life of all tubes is predicted to be 12,000 to 15,000 hours. Electron Beam Performance Overall beam performance is summarized in Table III. The maximum energy of 21 GeV was reached on an TABLE m ,n,ectur O. " O4 " (y) ,cm) k!sY 0.01n to o.om (y) (CI,,) experimental performance run on September 13, 1968. It corresponds to a contribution of about 90 MeV per $2 klystron. Typical physics runs require simultaneous interlaced beams between 5 …