Commissioning and first results of the Fermilab Muon Campus

In the following years the Fermilab Muon Campus will deliver highly polarized muon beams to the storage ring of the Muon g-2 Experiment. The Muon Campus contains a target section wherein secondaries are produced, the Delivery Ring which separates the muons from the rest of the beam and a straight section that transports them to the storage ring. Here, we report the first experimental results and experience gained from commissioning the Muon Campus, including the interaction of the proton beam with the target, the transport of secondary beam over long sections, the monitoring of muons from the available diagnostics and the development of techniques for measuring the beam optics. We present detailed comparisons between experimental data and simulation and discuss the similarities and differences observed. INTRODUCTION The Muon g-2 Experiment, at Fermilab, will measure the muon anomalous magnetic moment, �� to unprecedented precision: 0.14 parts per million. To perform the experiment, a polarized beam of positive muons is injected into a storage ring with a vertical uniform magnetic field. Details can be found elsewhere [1]. The Muon g-2 Experiment will be running in the new Fermilab Muon Campus [2]. Simulation studies [3] have shown that the Muon Campus has the potential to deliver highly polarized muons with 21 times the statistics of the equivalent Brookhaven experiment [4]. For the Fermilab Muon Campus operations, protons accelerated in the Linac and Booster are adiabatically re-bunched in the Recycler and led to a Inconel target. Secondary beam pions then travel around the Delivery Ring (DR) where the pions decay into muons, and finally the beam continues into the storage ring. The passage through the DR is very beneficial as it will provide enough time for pions to decay into muons and most importantly will increase the gap between the “light” muons and “heavy” protons. Here report the first experimental results of the Fermilab Muon Campus with emphasis on the experimental milestones that have demonstrated the Muon Campus capability of delivering beam to the Muon g-2 Experiment. These milestones included the interaction of primary proton beam with the target, the generation and transport of muons over long sections, the monitoring of secondaries from the available diagnostics and the development of techniques for measuring the beam optics. We also compare the experimental data with predictions from simulations and show that our model can describe the physics of the experiment within a reasonable level of agreement. MUON CAMPUS COMMISIONING Commissioning of the Fermilab Muon Campus begun on April 2017. In the first phase, a 8-GeV proton beam from the Recycler bypassed the target, entered the DR via the M3 line and finally was extracted into the M4 line. The beam intensity was by two orders of magnitudes higher compared to the secondary beam. As a result, this part of the commissioning provided a good testbed from crosschecking the optics and available instrumentation along the Muon Campus. For the second part of commissioning, the primary proton beam was sent to the target with the goal to commission the new-born 3.1-GeV secondary beam. To save experimental time, the secondary beam did not travel around the DR but rather passed straight through, then propagated down the M4/M5 lines, and into the g-2 storage ring. In the last phase, the primary beam was sent to the target and the 3.1 GeV secondary beam was passed through the DR, protons were removed after the fourth turn and the beam was sent in the storage ring via the M4M5 lines. This scenario is illustrated in Fig. 1 and will be the primary focus of this paper. Figure 1: Muon Campus sketch: (a) During operation, and (b) initial commissioning plan. In that case, revolutions of the beam around the DR will be omitted. MUON CAPTURE AND TRANSPORT The spot size of the primary beam impacting the production target is a key parameter that governs the final pion ___________________________________________ * Operated by Fermi Research Alliance, LLC under Contract No. DeAC02-07CH11359 with the United States Department of Energy. † diktys@fnal.gov 10th Int. Particle Accelerator Conf. IPAC2019, Melbourne, Australia JACoW Publishing ISBN: 978-3-95450-208-0 doi:10.18429/JACoW-IPAC2019-MOZZPLM3 MC4: Hadron Accelerators A09 Muon Accelerators and Neutrino Factories MOZZPLM3 41 Co nt en tf ro m th is w or k m ay be us ed un de rt he te rm so ft he CC BY 3. 0 lic en ce (© 20 19 ). A ny di str ib ut io n of th is w or k m us tm ai nt ai n at tri bu tio n to th e au th or (s ), tit le of th e w or k, pu bl ish er ,a nd D O I