Fermilab Accelerator R&d Program towards Intensity Frontier Accelerators : Status and Progress*

The 2014 P5 report indicated the accelerator-based neutrino and rare decay physics research as a centrepiece of the US domestic HEP program at Fermilab. Operation, upgrade and development of the accelerators for the nearterm and longer-term particle physics program at the Intensity Frontier face formidable challenges. Here we discuss key elements of the accelerator physics and technology R&D program toward future multi-MW proton accelerators and present its status and progress. INTENSITY FRONTIER ACCELERATORS The 2014 Particle Physics Project Prioritization Panel (P5) report [1] identified the top priority of the domestic intensity frontier high-energy physics for the next 20-30 years to be a high energy neutrino program to determine the mass hierarchy and measure CP violation, based on the Fermilab accelerator complex which needs to be upgraded for increased proton intensity. To this end, a new beam line the Long Baseline Neutrino Facility (LBNF) – and new experiment the Deep Underground Neutrino Experiment (DUNE), located in the Sanford Underground Research Facility (SURF) are being planned [2]. Figure 1: Fermilab Booster performance vs intensity: beam emittance (red line, right axis) and fractional beam loss now (black, left axis) and after anticipated upgrades (blue). Courtesy W.Pellico. The P5 physics goals require about 900 kt·MW·years of the total exposure (product of the neutrino detector mass, average proton beam power on the neutrino target and data taking period) and that can be achieved assuming a 40 kton Liquid Argon detector and accelerator operation with the eventual multi MW beam power. At present, after commissioning of the 6+6 batch slipstacking in the Recycler and reduction the Main Injector cycle time to 1.33s from 2.2s during the MINOS/Collider Run II era. Due to these improvements, in 2016 the Main Injector achieved world-record 615 kW average proton beam power over one hour to the NuMI beam line. On that way, the operations team increased number of batches slipstacked in Recycler in steps (just 6 batches in late 2014, then 2+6, 4+6 and, finally, 6+6 batches in mid-2016). At each step, the increase intensity was followed by tuning for efficiency and minimization of losses. Finally, the peak power of 700 kW for one minute was demonstrated in June 2016 [3]. Sustainable routine operation at that level is expected in 2017 after an upgrade of the Recycler beam collimation system which is going to take place during the Summer 2016 shutdown. ONGOING STUDIES AND PIP-II There are a number of ongoing experimental beam studies, theoretical investigations, modelling and simulation efforts dedicated to understanding beam dynamics issues with high intensity beams in the existing accelerators. Those include studies of the space-charge effects in the Booster [4] – see Fig.1, theory and experiments on the coherent beam stability in the Booster, Recycler and Main Injector [5-9], electron-cloud studies which include in situ SEY measurements, micro-wave measurements in the Main Injector and development of the most effective vacuum pipe coating and scrubbing methods [10]; evaluation need of a transition crossing optimization in the Booster and Main Injector; investigations of beam losses and efficiency of collimation systems employed in all accelerators [11, 12]. We advance our simulation and modelling capabilities for high-intensity beams by development of a flexible beam dynamics framework on base of SYNERGIA [13] with fully 3D PIC capabilities which include space-charge and impedance, both single and multi-bunch effects, single-particle physics with full dynamics and which could run on desktops, clusters and supercomputers. Continuous development of the MARS-based energy deposition modelling tools [14] includes updates related to recent developments in nuclear interaction models; implementation of polarized particle transport and interaction, developments of radiation damage models and transfer matrix algorithms in accelerator material-free regions; and further enhancement of the geometry modules. Numerous beam studies and upgrades are taking place in the Booster as part of the Proton Improvement Plan (PIP) [15]. They include studies of advanced injection schemes, efficient cogging, collimation efficiency, laser ___________________________________________ *Fermi Research Alliance, LLC operates Fermilab under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy #[email protected] FERMILAB-CONF-16-537-APC