Schematic layout of the DAFNE accelerator complex.
In order to gain substantial saving of funds and construction time, the double ring collider and its injector system have been installed in the ADONE buildings after the final shut down in April 1993.
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 Main Rings are assembled in the ADONE hall. At present only one detector, KLOE-2 is installed in the IR1 Interaction Region.
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 ~50 ms (2.5 damping times)
- The positron bunch is extracted from the Accumulator and injected into the positron Main Ring at 2 Hz
- The sequence is repeated for all the bunches to be injected into the positron Main Ring
- The converter target is extracted and the transfer line magnets are changed to transport the electrons
- The whole sequence is repeated for the electrons