The 25 nsec Run

GENERAL INTRODUCTION

In May 2000 there will be a special run atthe CERN SPS with a RF time structure close to the one foreseen for the LHC. This means that the protons will arrive at the primary target in narrow bunches (few nanoseconds), separated by 25 nanoseconds. Every 23 microseconds there will be a 1.2 microseconds long train of 42 bunches, followed by some 21 microseconds without beam. The overall intensity in the machine will be more than 10 times lower than usual, possibly 2 10¹² protons per SPS cycle extracted. The overall spill structure may not be as flat as in normal conditions.
The intensity in the secondary beam lines is normally limited by radio-protection limits (10⁶ ppp in the West Area beams, slightly higher in some of the North Area beams). The number of bunches is close to 10⁷ in a 2.58 sec flat top, but can be decreased by reducing the flat top (which is planned for some time in the second half of the spill).

This special run is in principle intented for the LHC experiments. However, some low-intensity tests for other experiments may be possible, though at not quite the same conditions as usual.

OTHER INFORMATION

More detailed information can be found via the following links:

• The nominal 25 nsec beam time structure (PS) (PDF)
• The 25 nsec beam time structure measured (by CMS) in the X5 beam (JPEG) (GIF)
• The number of protons per bunch vs flat top length (PS) (PDF)
• The time smearing by T.O.F. in the secondary beam (PS) (PDF)
• A somewhat more detailed description of the 25 nsec condition, based on information received via E.Tsesmelis.