The Mu2e Experiment At Fermilab

This book contains an interdisciplinary selection of timely articles which cover a wide range of superconducting technologies ranging from high tech medicine (10-12 Gauss) to multipurpose sensors, microwaves, radio engineering, magnet technology for accelerators, magnetic energy storage, and power transmission on the 109 watt scale. It is aimed primarily at the non-specialist and will be suitable as an introductory course book for those in the relevant fields and related industries. As shown in the title several examples of high-c applications are included. While low-Tc is still the leading technology, for instance, in cables and SQUIDS, case studies in these areas are presented.

In this thesis we discuss the simulation and tests carried out for the optimization and design of the electromagnetic calorimeter for the Mu2e (Muon to electron conversion) experiment, which is a proposed experiment part of the Muon Campus hosted at Fermi National Accelerator Laboratory (FNAL) in Batavia, United States.

The mission of the Fermilab Mu2e experiment is to detect the conversion of muons into electrons in the field of a nucleus. This conversion process is known as Charged Lepton Flavor Violation (CLFV) in particle physics. The Mu2e sensitivity is expected to be four orders of magnitude beyond the SINDRUM II experiment at the Paul Scherrer Institute. To meet this expectation, the experiment requires a low energy muon beam and a high precision detector. The Fermilab accelerator complex will be utilized to generate a proton beam in which a production solenoid (PS) will receive to produce the desired muon beam. The beam will then travel through the transport solenoids (TS) to a detector solenoid (DS). The sensitive measurement components such as the proton absorber and calorimeter, simply called the DS train, rest on rails within the detector solenoid. During installation of the DS train, component positions must meet a +/-2 mm tolerance. To ensure this goal, DS train components will undergo a new design iteration and will be evaluated through finite element analysis (FEA). Axial couplers used to connect each component on the DS train, will be designed and analyzed to prevent buckling and minimize deflection from the 2000 lb compressive load. A support stand for the instrumentation feed-through bulkhead (IFB) will be modified to facilitate the expected installation forces in reference to the ASME Division II guidelines for pressure vessels. The DS train installation process will need to be reviewed to prevent failures. This includes analyzing the pallet lifter chosen to extract the external stands the DS train rests on. Analysis is necessary to confirm that the trench grating that is built into the floor below the DS train will not bend significantly under the loading from the extraction process. Critical review of the components and installation of the beamline system is vital to the success of Mu2e.

The Mu2e experiment at Fermilab requires acceleration and transport of intense proton beams in order to deliver stable, uniform particle spills to the production target. To meet the experimental requirement, particles will be extracted slowly from the Delivery Ring to the external beamline. Using Synergia2, we have performed multi-particle tracking simulations of third-integer resonant extraction in the Delivery Ring, including space charge effects, physical beamline elements, and apertures. A piecewise linear ramp profile of tune quadrupoles was used to maintain a constant averaged spill rate throughout extraction. To study and minimize beam losses, we implemented and introduced a number of features, beamline element apertures, and septum plane alignments. Additionally, the RF Knockout (RFKO) technique, which excites particles transversely, is employed for spill regulation. Combined with a feedback system, it assists in fine-tuning spill uniformity. Simulation studies were carried out to optimize the RFKO feedback scheme, which will be helpful in designing the final spill regulation system.

The Mu2e experiment at Fermi National Accelerator Laboratory seeks to observe the ultra-rare process of a lepton changing flavor from higher to lower fermion generations. This is known theoretically as a Charged Lepton Flavor Violation (CLFV), and finding evidence of such a process would provide insight into new areas of physics outside the Standard Model. Mu2e intends on achieving higher sensitivity than any other such experiment by employing state-of-the-art detectors and trackers to collect data, and minimize all background sources of error with unprecedented precision. One of these backgrounds comes from natural cosmic-ray muons, which can produce particles that appear to be created within the detector, or can themselves be misidentified as electrons. To eliminate this source of error, a detector capable of detecting penetrating cosmic muons will be utilized. This detector, named Cosmic Ray Veto (CRV), is designed as a set of sections of additional shielding to be mounted onto the concrete shielding. Each section is made up of several modules composed of four layers of long extrusions of scintillating polystyrene and aluminum panels bonded adhesively. To achieve the desired efficiency of 0.9999, the modules of each section are stepped at their ends and interlocked with millimeter precision. In the top section of the CRV, there is a need for the ability to move modules to access electronics and other components otherwise enclosed beneath them. To facilitate access to these components, a system of lifting mechanisms, which would support and raise modules using a centered platform, is being designed. Given that this loading scenario was unaccounted for when modules were being designed, their structural integrity, as well as the performance of the adhesive used to bond them, needs to be evaluated. Critical design constraints for these mechanisms, such as platform width, rise speed, load capacity, and material selection, will be determined by evaluating modules' stresses and deformations under this new loading scenario using FEA. Furthermore, shear and peel samples, made of aluminum and polystyrene bonded with the resin epoxy used to construct modules, will be built per ASTM codes D1002 and D3164 respectively. These samples will be subjected to thermal fluctuations and compression and loaded until failure. Gathered data for failure loads and modes will be evaluated to assess adhesive performance and quantify the effects of such pre-test conditions.

Proton bunch formation from the Fermilab proton sources for the mu2e experiment is discussed. In the initial scenario a single intense h=1 bunch is formed in the Accumulator/Debuncher, with slow extraction providing the required spill. However, the mu2e experiment could use h=4 bunching in the Accumulator rather than h=1, with the 4 bunches fed one at a time into the more isochronous Debuncher for slow extraction. The h=4 variant has several advantages and a few disadvantages, and can reduce peak beam intensities, and therefore improve space charge limits. The method can be extended to project X to enable high duty cycle extraction within space charge limits. A further extension should make possible an accumulator/buncher scenario that can provide 8 GeV short bunches for a neutrino factory and/or muon collider scenario.