Fermilab, Batavia, Illinois, USA
To provide 700 kW proton beams for neutrino production in the NuMI facility, we employ slip stacking in the Recycler with transfer to the Main Injector for recapture and acceleration. Slip stacking with 12 Booster batches per 1.33 sec cycle of the Main Injector has been implemented and extensive operation with 8 batches and 10 batches per MI cycle has been demonstrated. Operation in this mode since 2013 shows that loss localization is an essential component for long term operation. Beam loss in the Recycler will be localized in a collimation region with design capability for absorbing up to 2 kW of lost protons in a pair of 20-Ton collimators (absorbers). This system will employ a two stage collimation with a thin Mo scattering foil to define the bottom edge of both the injected and decelerated-for-slipping beams. Optimization and engineering design of the collimator components and radiation shielding are based on comprehensive MARS15 simulations predicting high collimation efficiency as well as tolerable levels of prompt and residual radiation. The system installation during the Fermilab 2016 facility shutdown will permit commissioning in the subsequent operating period.
Fermilab, Batavia, Illinois, USA
Using Synergia accelerator modeling package and Dynamic Mode Decomposition technique, the properties of the first transverse dipole mode in Gaussian bunches with space charge are compared at transverse coupling resonance and off-resonance. The Landau damping at coupling resonance and in the strong space charge regime is a factor of two larger, while the mode's tune and shape are nearly the same. While the damping mechanism in the off-resonance case fits well with the classical Landau damping paradigm, the enhancement at coupling resonance is due to a higher order mode-particle coupling term which is modulated by the amplitude oscillation of the resonance trapped particles.
Fermilab, Batavia, Illinois, USA
The Recycler is an 8 GeV/c proton storage ring at Fermilab. To achieve the 700 MW beam power goals for the NOvA neutrino oscillation experiment, the Recycler accumulates 12 batches of 80-bunch trains from the Booster using slip-stacking. One set of bunch trains are injected into the ring and decelerated, then a second set is injected at the nominal momentum. The trains slip past each other longitudinally due to their momenta difference. We have recently extended the multi-bunch portion of the Synergia beam simulation program to allow co-propagation of bunch trains at different momenta. In doing so, we have expanded the applicability of the massively parallel multi-bunch physics portion of Synergia to include new categories of bunch-bunch interactions. We present results from our first application of these capabilities to batch-on-batch slip stacking in the Recycler.
