Session B07: Accelerator Applications, Beam Dynamics, Diagnostics, and Colliders

Ultrafast Electron Diffraction with Stray Sextupole Field Correction

Ultrafast Electron Diffraction (UED) is a technique which allows for the study of atomic and molecular scale dynamics at the picosecond timescale and below.  In order to use UED on a material, it is necessary to create a periodic structure large enough that the probing electron beam can create a coherent diffraction image.  For some materials, it is difficult to do this at length scales larger than a few microns.  These simultaneous constraints on both the physical size and the momentum spread require an electron beam with an emittance near the single nanometer scale.  To achieve this, we use a photocathode with the capability of producing beams with a mean transverse energy on the scale of tens of meV.  A series of focusing magnets are then used to bring the beam to a focus just before the sample location.  These focusing elements also create stray fields, which increase the emittance of the beam.  We use a series of corrector magnets, which correct stray magnetic fields up to and including the sextupole field, which allow us to preserve the beam quality throughout the beamline.   

Fixed Field Fast Cycling 1.3KHz Permanent Magnet 30-250 MeV Synchrotron

We present a novel concept of the Fixed-Field-Alternating (FFA) small racetrack proton accelerator with kinetic energy range between 30-250 MeV made of permanent magnets. The horizontal and vertical tunes are fixed within the energy range providing very fast cycling with a frequency of 1.3 KHz. The injector is 30 MeV commercially available cyclotron with RF frequency of 65 MHz. The permanent magnet synchrotron RF frequency is 390 MHz and acceleration uses the phase jump scheme.   

Electron cooling of proton beams with intense space-charge at IOTA

Electron cooling as a method of creating intense ion beams has a practical upper limit when it comes to the peak phase space density of ion beams which can be achieved in practice. We describe a new experiment to study electron cooling of 2.5 MeV protons at the intensity limit using the Integrable Optics Test Accelerator (IOTA), which is a storage ring dedicated to beam physics research at Fermilab. This system will enable the study of magnetized electron cooling of a proton beam with transverse incoherent tune shifts approaching -0.5 due to the presence of intense space-charge forces. We present an overview of the hardware design, simulations and specific experiments planned for this project.   

Beam Dynamics simulations for the Fermilab E989 Muon $g-2$ Experiment

The E989 Muon $g-2$ Experiment at Fermilab (FNAL) recently determined the anomalous magnetic moment of the positive muon to be $a_{\mu}(\mathrm{FNAL})=116592040(54) \times 10^{-11}(\qty{0.46}{ppm})$. This result combined with the previous Brookhaven National Laboratory E821 measurement sets a new experimental average of $a_{\mu}(\mathrm{Exp})=116592061(41) \times 10^{-11}(\qty{0.35}{ppm})$. This result is 4.2 standard deviations greater than the standard model prediction. For the Muon $g-2$ Experiment at Fermilab, \qty{3.094}{\GeV/ c} muons are injected into the storage ring through a magnetic inflector. The storage ring has a 1.45 T magnetic dipole field. Right after the injection, the beam is moved to the nominal equilibrium orbit by using magnetic kickers during the first turn, and the electric field generated on the quadrupole plates shift the beam radially and vertically to move the edges of the beam into the collimators. After this, the quadrupole plates provide a focusing electric field so the stored muons will travel inside the storage ring until they decay into positrons. These will be detected by calorimeters to reconstruct the anomalous frequency $\omega_a$. The described elements affect the motion of the muons in the storage ring and can bias the extraction of $\omega_a$. Detailed simulations have been implemented to study the dynamics of the beam and estimate the size and nature of these systematic effects. This talk will present some studies and strategies used in simulations.   

Numi Beam Monitoring Simulation and Data Analysis

With the Main Injector Neutrino Oscillation Search (MINOS) experiment decommissioned, muon and hadron monitors became an important diagnostic tool for the NuMI Off-axis $v_\mu$ Appearance (NOvA) experiment at Fermilab to monitor the Neutrinos at the Main Injector (NuMI) beam. The goal of this study is to maintain the quality of the monitor signals and to establish correlations with the neutrino beam profile. And we carry out a systematic study of the response of the muon monitors to the changes in the parameters of the proton beam and lattice parameters. Moreover, we combine individual pixel information of muon monitors and pattern recognition algorithms with measurement data to build a  machine learning-based predictions of the muon monitor response and neutrino flux.   

Optimizing the Mu2e Proton Beam Position on the Production Target

Mu2e is a flagship muon experiment, currently under construction at Fermilab. Its muon beam will be generated via a precise collision of 8 GeV protons with a tungsten production target. In order to maximize the number of muons, Mu2e must align the proton beam with the production target to within ±0.5 mm. However, the requirements of the target, and the conditions under which it will operate, make direct instrumentation of the production target unfeasible. Instead, we describe a system of multiwire proportional chambers (MWPC’s), which record how the beam evolves before and after interacting with the target. These MWPC’s will be used in a beam-scanning procedure during experiment start-up to optimize the beam-target alignment to ensure high muon yield and maximum target lifetime.   

Muon Colliders: An International Effort to Drive Particle Physics Discovery

Muon colliders offer a unique path to multi-TeV, high-luminosity lepton collisions.  Muon collisions with a center-of-mass energy of 10 TeV or above would offer significant discovery potential where the constituent collision energies exceed those of the LHC program by an order of magnitude.  Significant progress on the fundamental R&D and design concepts for such a machine has led to a new international effort to assemble a conceptual design within the next few years.  This effort will assess the viability of such a machine as a successor to the LHC program.  The remaining challenges and the R&D required to deliver a complete machine description will be described.   

Beam backgrounds at SuperKEKB

We will review the study and mitigation of beam-induced backgrounds at the SuperKEKB electron-positron collider, which serves the Belle II experiment in Tsukuba, Japan. The experiment seeks New Physics beyond the Standard Model, which requires high beam currents and a luminosity of order 10³⁵ cm^-2s^-1. Currently, the backgrounds are not limiting the beam currents, and the machine has achieved a world record luminosity of about 3.6 x 10³⁴ cm^-2s^-1. This success required a good understanding of the beam loss mechanisms in the machine, comprehensive background monitoring, targeted mitigation, machine tuning and simulation. We will discuss computational and experimental techniques used for studying and mitigating the backgrounds, the current background status in Belle II, and our expectations for the challenges ahead on the road towards even higher luminosities.