> **R[ecycler]{.smallcaps}**

**19.d. [Background]{.underline}**

The Recycler is a fixed 8 GeV kinetic energy storage ring. The Run II
Luminosity Upgrade Plan requires the Recycler to play a key role,
starting mid-2005, as the repository of large stacks of antiprotons (600
x 10^10^) to be used in the collider stores. In order to maximize the
stacking efficiency of the antiproton accumulator, small stacks of
antiprotons will be transferred to the Recycler frequently. In the
Recycler, the stacks are initially cooled by stochastic cooling and then
stored and cooled by electron cooling until the antiprotons are ready to
be used in Tevatron shots.

The Run II upgrade plan foresees the Recycler fully integrated into
collider operations in two major steps. First, the Recycler is
commissioned to bring its performance to the level that it is ready to
begin the implementation of electron cooling. This milestone was
achieved in June 2004 (FY04). In the second phase, the installation of
electron cooling and its commissioning takes place. The electron cooling
is expected to be operational by June 1, 2005 (FY05).

An R&D effort to facilitate the electron-cooling project is underway at
the Wide-band Lab at Fermilab. The facility with a 5 MV Van de Graaff
accelerator (Pelletron) and proto-type electron beamlines is being used
to develop and demonstrate the required system parameters for the
electron beam that would be used in the cooling of antiprotons in the
Recycler.

###### **19.f. Accomplishments in FY04**

The Recycler commissioning plan includes seven major milestones. The
technical requirements of the three milestones to date have all been met
and they have been achieved ahead of schedule. These milestones were (a)
demonstrating adequate vacuum performance, (b) demonstrating adequate
vacuum and machine admittance, and (c) effecting transfers of
antiprotons from the Main Injector into the Recycler and back into the
Main Injector with greater than 85% overall efficiency and less than 3Π
mm-mr transverse emittance growth. The remaining milestones include the
commissioning of transfers into the Recycler, the operational
commissioning of extraction, and the demonstration that the Recycler is
ready for the installation of electron cooling.

**19.g.1. [Accomplishments Expected in FY05]{.underline}**

The Recycler will start its integration into the Fermilab Accelerator
complex during later part of FY05 and should become an integral part by
the end of FY05. It is expected that the major accomplishment will be
the commissioning of the electron cooling system. The Recycler
performance will be optimized.

The Recycler will need an injection and transverse damper. Additional
improvements will become clear as the Recycler and its electron cooling
system continue to be commissioned and integrated into the complex.

### 19.g.2. Future Accomplishments Expected in FY06 and Beyond

When electron cooling is operational and the Accumulator is producing
antiprotons at the rate of \~ 40 x 10^10^/ hr, it is planned to operate
the complex in the following manner. Every thirty minutes 20 x 10^10^
antiprotons will leave the Accumulator with 10 eV-s, 10Π mm-mrad
emittance and arrive at the Recycler with 13 eV-s and 15Π mm-mrad
emittances. This newly transferred beam of 20 x 10^10^ antiprotons will
be kept in its own holding bucket to be transversely cooled by a gated
stochastic cooling system to below 10Π mm-mrad before it is merged with
the cooled stack. The cooled stack is located between barriers that have
an internal spacing of two to six microseconds and the equilibrium 90%
longitudinal emittance of 36 eV-s. After 15 hours or so there will be a
stack of 600 x 10^10^ antiprotons ready to inject into the Tevatron.
While the Recycler stochastic cooling cools the newly transferred
antiprotons all cooling of the main stack, longitudinal and transverse,
is performed by the electron cooling system.