INJECTION SYSTEM AND LAYOUT

In order to gain substantial saving of funds and construction time, the double ring collider and its injector system have been designed to cope with the buildings where ADONE was installed. After the final shut down in April 1993, the old storage ring, its injector Linac, the transfer lines from the Linac to the storage ring and all the experimental beamlines were dismantled and the buildings completely renovated to host the new accelerator complex.

The injection system of DAFNE consists of a Linac, an intermediate Accumulator Ring, and ~180 m of Transfer Lines from the Linac to the Accumulator and from the Accumulator to the Main Rings. This rather long and complicated arrangement was dictated by the necessity of utilising the existing buildings, keeping new civil constructions at a minimum. The new Linac and its power supplies are located in the old Linac building. The Accumulator with its transfer lines is installed in an experimental hall, where the old Linac beam was extracted and used for nuclear physics experiments. The Main Rings are assembled in the ADONE hall, where two large reinforced pits, decoupled from the accelerator floor, have been built to host the large and heavy magnetic detectors of KLOE and FINUDA.

The DAFNE injection system has been designed to fill in few minutes from scratch the large required current in the Main Rings in the single bunch mode in order to ensure the maximum flexibility in the stored bunch patterns. The whole system runs at the operating energy of the collider, so that the current decay (mainly due to the Touschek effect) can be compensated by refilling the rings on top of the already circulating current (this injection mode is called "topping up").

The injection scheme is the following:

• Positrons are accelerated in the Linac (converter target in) in 10 ns pulses at 50 Hz
• Positrons are injected into a single Accumulator bunch up to a pre-set current
• The positron beam is cooled down in the Accumulator by waiting for 5 damping times (~100 ms)
• The positron bunch is extracted from the Accumulator and injected into the positron Main Ring
• The sequence is repeated for all the bunches to be injected into the positron Main Ring
• Separators are switched on to separate the beams at the crossing point
• The converted target is extracted and the whole sequence is repeated for the electrons
• Separators are switched off and beams are brought into collision.