The measurement of beam emittances by extracting the quadrupole mode signal from a 4 plate beam position monitor (BPM) was published at least 40 years ago. Unfortunately, in practice, this method suffers from poor signal to noise ratio and requires a lot of tuning to extract out the emittances. In this paper, an improved method where multiple BPMs are used together with better mathematical analysis is described. The BPM derived emittances are then compared with those measured by the Ion Profile Monitor (IPM). Surprisingly, the BPM measured emittances behave very well and are more realistic than those measured by the IPM.

The Fermilab Proton-Improvement-Plan-II (PIP-II) is being implemented in order to support the precision neutrino oscillation measurements at the Deep Underground Neutrino Experiment, the U.S. flagship neutrino experiment. The PIP-II LINAC is presently under construction and is expected to provide 800 MeV protons with 2 mA current. This white paper summarizes the outcome of the first workshop on May 10 through 13, 2023, to exploit this capability for new physics opportunities in the kinematic regime that are unavailable to other facilities, in particular a potential beam dump facility implemented at the end of the LINAC. Various new physics opportunities have been discussed in a wide range of kinematic regime, from eV scale to keV and MeV. We also emphasize that the timely establishment of the beam dump facility at Fermilab is essential to exploit these new physics opportunities.

DUNE/LBNF constitutes an international multi-decadal physics program for leading-edge neutrino science and proton decay studies [1] and is expected to serve as the flagship particle experiment based at Fermilab.

The Fermi National Accelerator Laboratory (FNAL) Linac has been in operation for 52 years. In approximately four years, it will be replaced by a new 800 MeV superconducting machine, the PIP-II SRF Linac. In the current configuration, the Linac delivers H- ions at 400 MeV and injects protons by charge exchange into the Booster synchrotron. Despite its age, the Linac is the most stable accelerator in the FNAL complex, reliably sending 22 mA in daily operations. We will discuss the status of the operation, beam studies, and plans.

The FNAL accelerator complex is poised to reach MW neutrino beams on target for the exploration of the dark sector physics and rare physics program spaces. Future operations of the complex will include CW linac operations at beam intensities that have not been seen before \cite{PIP2,RCS_LOI}. The ambitious beam program relies on multi-turn H$^{-}$ injection into the FNAL Booster and then extracted into delivery rings or the Booster Neutrino Beam (BNB) 8 GeV HEP program. A new rapid-cycling synchrotron (RCS) will be required to reach the LBNF goal of 2.4 MW because of intense space-charge limitations. There are many accelerator engineering challenges that are already known and many that will be discovered. This proposal calls for an intermediate step that will both facilitate the operation of Booster in the PIP-II era and gain operational experience associated with high power injection rings. This step includes the design, construction and installation of a 0.8 GeV accumulator ring (upgradeable to 1+ GeV) to be located in the PIP-II Booster Transfer Line (BTL). The PIP-II accumulator ring (PAR) may be primarily designed around permanent magnets or use standard iron core magnet technology with an aperture selected to accommodate the desired high intensity protons at 0.8 GeV.

Within the Lab Directed R&D Program at Fermilab, and in partnership with National Magnetics, we have recently begun to study and attempt to improve the loss parameter in garnet material. This could be used for fast tuner applications such as in rapid cycling synchrotrons.

The Fermilab Booster uses multi-turn beam injection with all its cavities phased such that beam sees a net zero RF voltage even when each station is at the same maxi-mum voltage. During beam capture the RF voltage is increased slowly by using its paraphase system. At the end of the capture the feedback is turned on for beam acceleration. It is vital for present operations as well as during the PIP-II era that both the HLRF and LLRF systems provide the proper intended phase and RF voltage to preserve the longitudinal emittance from injection to extraction. In this paper, we describe the original architecture of the cavity phase distribution, our recent beam-based RF phase measurements, observed significant deviation in the relative phases between cavities and correction effort. Results from the improved capture for high intensity beam are also presented.

At the Fermilab Booster, and many other proton facili-ties, an intense proton beam is accumulated by multi-turn injection of an H- beam through a stripping foil. The circu-lating beam scatters off the injection foil and large-angle Coulomb scattering leads to uncontrolled losses concen-trated in the first betatron period. We measure the foil scat-tering loss rate in the Fermilab Booster as a function of LINAC current, number of injection turns, and time on the injection foil. We find that current Booster operation has ~1% foil scattering loss and we make projections for the Proton Improvement Plan II (PIP-II) injector upgrade. Here we present the results from our recent beam measure-ments and a foil scattering model analyses.

As the main $H^{-}$ ion source for the accelerator complex, magnetron ion sources have been used at Fermilab since the 1970s. At the offline test stand, new R&D is carried out to develop and upgrade the present magnetron-type sources of $H^{-}$ ions of up to 80 mA and 35 keV beam energy in the context of the Proton Improvement Plan. The aim of this plan is to provide high-power proton beams for the experiments at FNAL. In order to reduce the amount of tuning and monitoring of these ion sources, a new electronic system consisting of a current-regulated arc discharge modulator allow the ion source to run at a constant arc current for improved beam output and operation. A solenoid-type gas valve feeds $H_{2}$ gas into the source precisely and independently of ambient temperature. This summary will cover several studies and design changes that have been tested and will eventually be implemented on the operational magnetron sources at Fermilab. Innovative results for this type of ion source include cathode geometries, solenoid gas valves, current controlled arc pulser, cesium boiler redesign, gas mixtures of hydrogen and nitrogen, and duty factor reduction, with the aim to improve source lifetime, stability, and reducing the amount of tuning needed. In this summary, I will highlight the advances made in ion sources at Fermilab and will outline the directions of the continuing R&D effort.

A second harmonic RF cavity which uses perpendicularly biased garnet for frequency tuning is currently being constructed for use in the Fermilab Booster. The cavity will operate at twice the fundamental RF frequency, from ~76 106 MHz, and will be turned on only during injection, and transition or extraction. Its main purpose is to reduce beam loss as required by Fermilab’s Proton Improvement Plan (PIP). After three years of optimization and study, the cavity design has been finalized and all constituent parts have been received. We discuss the design aspects of the cavity and its associated systems, component testing, and status of the cavity construction.

A second harmonic tunable RF cavity is being developed for the Fermilab Booster. This device, which promises reduction of the particle beam loss at the injection, transition, and extraction stages, employs perpendicularly biased garnet material for frequency tuning. The required range of the tuning is significantly wider than in previously built and tested tunable RF devices. As a result, the magnetic field in the garnet comes fairly close to the gyromagnetic resonance line at the lower end of the frequency range. The chosen design concept of a tuner for the cavity cannot ensure uniform magnetic field in the garnet material; thus, it is important to know the static magnetic properties of the material to avoid significant increase in the local RF loss power density. This report summarizes studies performed at Fermilab to understand variations in the magnetic properties of the AL800 garnet material used to build the tuner of the cavity.

A perpendicularly biased 2nd harmonic cavity is being designed and built for the Fermilab Booster. Its purpose is to flatten the bucket at injection and thus change the longitudinal beam distribution to decrease space charge effects. It can also help at extraction. The cavity frequency range is 76 - 106 MHz. The power amplifier will be built using the Y567B tetrode, which is also used for the fundamental mode cavities in the Fermilab Booster. We discuss recent progress on the cavity, the biasing solenoid design and plans for testing the tuner's garnet material.

This is a status report on the 2nd harmonic cavity for the Fermilab Booster as part of the Proton Improvement Plan (PIP) for increasing beam transmission efficiency, and thus reducing losses. A set of tuner rings has been procured and is undergoing quality control tests. The Y567 tube for driving the cavity has been successfully tested at both injection and extraction frequencies. A cooling scheme for the tuner and cavity has been developed after a thorough thermal analysis of the system. RF windows have been procured and substantial progress has been made on the mechanical designs of the cavity and the bias solenoid. The goal is to have a prototype cavity ready for testing by the end of 2017.

A perpendicularly biased tuneable 2nd harmonic cavity is being constructed for use in the Fermilab Booster. The cavity's tuner uses National Magnetics AL800 garnet as the tuning media. For quality control, the magnetic properties of the material and the uniformity of the properties within the tuner must be assessed. We describe two tests which are performed on the rings and on their corresponding witness samples.

Electron cloud beam instabilities are an important consideration in virtually all high-energy particle accelerators and could pose a formidable challenge to forthcoming high-intensity accelerator upgrades. Dedicated tests have shown beampipe coatings dramatically reduce the density of electron cloud in particle accelerators. In this work, we evaluate the performance of titanium nitride, amorphous carbon, and diamond-like carbon as beampipe coatings for the mitigation of electron cloud in the Fermilab Main Injector. Altogether our tests represent 2700 ampere-hours of proton operation spanning five years. Three electron cloud detectors, retarding field analyzers, are installed in a straight section and allow a direct comparison between the electron flux in the coated and uncoated stainless steel beampipe. We characterize the electron flux as a function of intensity up to a maximum of 50 trillion protons per cycle. Each beampipe material conditions in response to electron bombardment from the electron cloud and we track the changes in these materials as a function of time and the number of absorbed electrons. Contamination from an unexpected vacuum leak revealed a potential vulnerability in the amorphous carbon beampipe coating. We measure the energy spectrum of electrons incident on the stainless steel, titanium nitride and amorphous carbon beampipes. We find the electron cloud signal is highly sensitive to stray magnetic fields and bunch-length over the Main Injector ramp cycle. We conduct a complete survey of the stray magnetic fields at the test station and compare the electron cloud signal to that in a field-free region.

A new test stand at Fermi National Accelerator Laboratory (FNAL) is being constructed to carry out experiments to develop and upgrade the present magnetron-type sources of H(-) ions of up to 80 mA at 35 keV in the context of the Proton Improvement Plan. The aim of this plan is to provide high-power proton beams for the experiments at FNAL. The technical details of the construction and layout of this test stand are presented, along with a prospective set of diagnostics to monitor the sources.

The Fermilab Booster is being upgraded under the Proton Improvement Plan (PIP) to be capable of providing a proton flux of $2.25^{17}$ protons per hour. The intensity per cycle will remain at the present operational $4.3^{12}$ protons per pulse, however the Booster beam cycle rate is going to be increased from 7.5 Hz to 15 Hz. One of the biggest challenges is to maintain the present beam loss power while the doubling the beam flux. Under PIP, there has been a large effort in beam studies and simulations to better understand the mechanisms of the beam loss. The goal is to reduce it by half by correcting and controlling the beam dynamics and by improving operational systems through hardware upgrades. This paper is going to present the recent beam study results and status of the Booster operations.

A high-current (>50 mA) dimpled H- magnetron source has been built at Fermilab for supplying H- beam to the entire accelerator complex. Despite many decades of expertise with slit H- magnetron sources at Fermilab, we were faced with many challenges from the dimpled H- magnetron source, which needed to be overcome in order to make it operational. Dimpled H- sources for high-energy physics are not new: Brookhaven National Laboratory has operated a dimpled H- source for more than two decades. However, the transference of that experience to Fermilab took about two years because a cookbook for building this type of source did not exist and seemingly innocuous or undocumented choices had a huge impact on the success or failure for this type of source. Therefore, it is the goal of this paper to document the reasons for these choices and to present a cookbook for building and operating dimpled H- magnetron sources.

The new FNAL Injector Line with a circular dimple magnetron ion source has been operational since December of 2012. Since the new injector came on line there have been variations in the H-beam current flattop observed near the downstream end of the Linac. Several different cathode geometries including a hollow cathode suggested by Dudnikov [1] were tried. Previous studies also showed that different mixtures of hydrogen and nitrogen had an effect on beam current noise [2]. We expanded on those studies by trying mixtures ranging from (0.25% nitrogen, 99.75% hydrogen) to (3% nitrogen, 97% hydrogen). The results of these studies in our test stand will be presented in this paper.