Muons, Inc.

Who We Are

Muons, Inc. was formed in 2002 to participate in Small Business Innovation Research (SBIR) and Small Business Technology Transfer (STTR) programs which fund research on muon beam cooling and on applications such as neutrino factories, muon colliders, and stopping muon beams.

Muons, Inc. carries out innovative scientific research on topics of national and global interest, including development, design, and implementation.

We believe that muon accelerators and storage rings are inevitable, given the inherent advantages of muons over protons and electrons for collider applications and the fundamental interest in the muon itself. We believe that the ILC will eventually be upgraded to a muon collider, and our primary focus is to:

Develop concepts for a Muon Collider that can extend the energy frontier,
Demonstrate the technical feasibility of key components of such a collider, and
Energize the High Energy Physics community to make such a collider a reality.

What We Are Doing

The company has formed partnerships with Fermilab, Jefferson Lab, and the Illinois Institute of Technology (IIT) to invent new concepts for muon beam cooling and to develop the relevant technologies for their realization.

The scientific and technological expertise of the Muons, Inc. staff and our research partners includes:

• Numerical Simulations of Matter-Dominated Beam Lines, Accelerators, and Experiments
• Pressurized RF Cavities and Linacs for Muon Cooling and Acceleration
• RF Breakdown Phenomena and Mitigation
• Design of Innovative Muon Cooling Channels
• Helical Cooling Channels
• MANX, a six-dimensional Muon Cooling Demonstration Experiment
• High-Temperature Superconductor for use in High-Field Applications
• Superconducting Magnet Technology for Muon Cooling Applications
• Superconducting RF Technology for Muon Acceleration Applications
• Muon Collider Design
• Neutrino Factory Design
• Stopping Muon Beam Design

Muons, Inc. is very interested to form partnerships to study these and other cutting-edge technologies. We have openings for physics and engineering staff.

Strategic Mission and Design Concepts

Muons, Inc. has been participating in SBIR-STTR programs that fund research on muon beam cooling and on applications such as neutrino factories, muon colliders, and stopping muon beams.

Why a Muon Collider?

The Large Hadron Collider, now under construction at CERN, will permit the study of hadron-hadron collisions and will be a center for high energy physics research for decades to come. At the same time, physicists need to carry out the complementary detailed studies of lepton-lepton collisions, so the present plan of the physics community calls for the design and construction of the International Linear Collider (ILC), the purpose of which is the study of electron-positron collisions. We are striving to advance the science and technology of muon colliders, as an alternative or follow-on to the ILC, because muons have a significant advantage over electrons - muons are 200 times heavier, so muon beams are much less subject to energy loss from synchrotron radiation in magnetic fields. That is, very high energy muon beams (unlike similar electron beams) can be bent in beam lines and can be recirculated in an accelerator. Therefore, muon recirculating colliders can reach very high energies at a relatively low cost, when compared with electron linear colliders. The two disadvantages of using muons are (1) that muon beams originate from the decay of pion beams and are very diffuse (have large emittances), and (2) that muons are unstable particles with a lifetime of 2.2 microseconds. The concept of a muon collider requires the head-on collisions of very tiny muon beams (ones with very small emittances), so the central, and extremely-difficult challenge of designing a muon collider is the reduction of the muon beam size (i.e., the “cooling” of its six-dimensional emittance) in a very short time, before the muons decay away.

Why Ionization Cooling in Helical Channels?

Much of the scientific and technological innovation being developed by Muons, Inc. involves the extraordinarily rapid cooling of muon beams by ionization cooling in helical channels, so a brief and somewhat simplified explanation will be provided here. Ionization cooling works by a combination of two physical effects: (1) the particles in the beam lose kinetic energy in the direction of travel (longitudinal energy and transverse energy), when the beam passes through matter in the form of a high-pressure, low-Z gas, and (2) RF cavities restore the longitudinal energy that has been lost. The net result is that the transverse energy of beam particles is rapidly removed. When ionization cooling is applied aggressively, the normalized emittance of the muon beam can be reduced by many orders of magnitude in a remarkably short cooling channel. (Note that ionization cooling does not work for hadrons, which interact with the gas because of strong interactions, or for electrons, which produce electromagnetic showers because of their low mass.) Ionization cooling is inherently transverse cooling, but muon colliders require muon beams with small longitudinal emittances as well. Helical cooling channels are ionization cooling channels in which the beam is transported along a helical (i.e., corkscrew) path, such that emittance exchange occurs and beam cooling is provided in all six dimensions in phase space. One important innovation is that the helical cooling channel has momentum-dependent path length such that the beam momentum spread is reduced by dE/dx energy loss in a simple, continuous absorber that fills the channel.

Why Pressurized RF Cavities?

Ionization cooling requires a low-Z absorber and RF cavities, and the cooling channel should be as short as possible. Muons, Inc. has invented and is developing the concept of high-pressure RF cavities, new in the field of particle accelerators. This design concept takes advantage of the high-pressure region of the Paschen curve, by utilizing high-gradient RF cavities filled with high-pressure, low-Z gas, thereby combining the absorbers and the RF cavities in a cooling channel of minimum length.

What are the advantages of very cooled muon beams?

Beams that are cooled beyond the limits of the helical cooling channel can be used to create a muon collider with many advantageous characteristics. This Low Emittance Muon Collider concept, with fewer muons required for high luminosity, is being developed using new techniques described below. In addition, the small six-dimensional emittance that is envisioned generates a new possibility to use the accelerating structures that are being developed for the ILC. These structures can be used in recirculating Linacs to reduce costs of muon colliders and also neutrino factories based on muon storage rings.

Funding and Projects

In order to fund this research program, Muons, Inc. has succeeded in winning fifteen (nine Phase I and six Phase II) SBIR-STTR grants:

G4Beamline – Particle Tracking in Matter-Dominated Beam Lines

Phase I STTR: 4/2006
Most computer programs that calculate the trajectories of particles in accelerators assume that the particles travel in an evacuated chamber, but muon colliders and neutrino factories require muon beams, which are usually designed to pass through matter. Therefore, the development of muon beams has been limited by a lack of user-friendly numerical simulation codes that accurately calculate scattering and energy loss in matter. Geant4 is an internationally supported tracking toolkit that has been developed to simulate particle interactions in large detectors for high energy physics experiments, and it includes most of what is known about the interactions of particles with matter. Geant4 has been partially adapted in a program called G4Beamline (G4BL) for designing muon beam lines. We are continuing the development of G4BL to enhance its graphical user interface and to add other features to facilitate its use by a broader group of beam-line and accelerator designers. The goal of this collaboration with the Illinois Institute of Technology is to develop the very first particle simulation code with all of the following important capabilities:

• Reliable and verified scattering cross sections, angular distributions, and energy loss,
• An excellent accelerator physics interface.

6DMANX – Development and Demonstration of 6-Dimensional Muon Beam Cooling

Phase I STTR: 4/2006
The objective of this collaboration with the Technical Division of Fermilab is to develop the use of high-gradient hydrogen-filled RF cavities for simultaneous phase rotation and ionization cooling at the beginning of a muon beam line. The simulation codes G4BL and ICOOL are being used to model beam capture, phase rotation, and precooling as close to the pion production target as possible. MARS is being used to model the particle flux from the target through the RF cavities, in the effort to develop the relevant hardware, and the experimental data from ongoing high-pressure RF cavity development will be evaluated. We are designing a muon cooling experiment that will demonstrate six-dimensional cooling. (Current experiments can only demonstrate four-dimensional cooling.) This demonstration will use a helical cooling channel with a He absorber, but no RF.

Muon Capture, Phase Rotation, and Precooling in Pressurized RF Cavities

Phase I STTR: 4/2005, Phase II STTR: 7/2006
Phase-space rotation has been used for many years at Fermilab and CERN to improve antiproton capture in cooling rings. This phase rotation consists of taking a particle distribution that is broad in momentum but narrow in time, and rotating it so that it becomes narrower in momentum and broader in time - this increases the number of beam particles that fit into the momentum acceptance of the following system. Unfortunately, this scheme requires the circulation of the antiprotons in a cooling ring for several revolutions, so it will not work for muons, which have a short lifetime.

The goal of this collaboration with the Accelerator Division of Fermilab is to develop the use of high-gradient, hydrogen-filled RF cavities for simultaneous phase rotation and ionization cooling at the beginning of a muon beam line. The high-gradient RF cavities will provide the very rapid phase-space rotation that is required. Two additional exciting new ideas are now being incorporated into this work:

• Higher-energy capture will enhance the performance of the muon-beam capture process
• The use of lower-intensity muon bunches suitable for high-energy coalescing will reduce the performance requirements on the initial stages of a muon collider cooling and acceleration facility.

Reverse Emittance Exchange

Phase I STTR: 4/2005, Phase II STTR: 7/2006
Muon-collider luminosity depends on the intensity and the transverse size of the beams in collision. Ionization cooling as it is presently envisioned will not cool the beams as much as is desired, so extremely high muon-beam intensities are still required. These high intensities will drive up the collider cost, create neutrino-induced radiation, and hinder experiments in the collider ring. The purpose of this collaboration with Jefferson Lab is to design and to simulate a new method of decreasing the transverse emittance of a muon beam in the last cooling stages for a muon collider. This innovative emittance-exchange technique is similar to that proposed to achieve six-dimensional cooling using wedge-shaped energy absorbers. However, the direction of the emittance exchange is reversed, hence the name, “reverse emittance exchange.” Because the earlier cooling sections reduce the longitudinal emittance well below the actual requirements of a muon collider, exchanging emittance from transverse phase space into longitudinal phase space can significantly increase the luminosity of the collider. The goal of this emittance exchange, then, is to reduce the requirements for high beam intensity and to make the muon-collider concept much more viable. An important outcome of this project has been the concept of high-energy muon bunch coalescing, in which a dozen or so muon bunches are coalesced into one bunch at 20 to 30 GeV in a special ring. This approach overcomes limitations of beam loading, space-charge, and wakefield effects in the cooling and first acceleration stages of a collider. It also provides a way to use the same initial muon cooling techniques for both a neutrino factory and muon collider, making research for these machines more synergistic.

Hydrogen Cryostat

Phase I STTR: 4/2004, Phase II STTR: 7/2005
The purpose of this collaboration with the Technical Division of Fermilab is to design various aspects of the cryogenic system for a helical cooling channel. The novel solution we proposed is to use a single hydrogen system to provide ionization energy loss for muon beam cooling, breakdown suppression for pressurized high-gradient RF cavities, and refrigeration for superconducting magnets and cold RF cavities. Several cryostat design alternatives are being studied and optimized. Experimental investigations are being carried out on the temperature-dependent properties of the construction materials, along with design studies of the superconducting cable and coils, the RF cavities, and other cooling channel components. One important outcome of this project has been the initial investigation showing that high-temperature superconductor when operated at liquid helium temperature can be used to provide very high fields for exceptional muon beam ionization cooling. A remaining task is to design the cryostat for a six-dimensional muon beam cooling demonstration experiment.

Ionization Cooling Using Parametric Resonances

Phase I SBIR: 4/2004, Phase II SBIR: 7/2005
Muon-collider luminosity depends on the intensity and the transverse size of the beams in collision. Ionization cooling as it is presently envisioned will not cool the beams as much as is desired, so extremely high muon-beam intensities are still required. The purpose of this collaboration with Jefferson Lab is to design and simulate an innovative idea that will reduce the requirement for high beam intensity by enhancing the effectiveness of muon ionization cooling:

• By operating near a half-integer resonance in the beam transport lattice, artificially low betas can be achieved
• By placing the absorber for ionization cooling at such places the equilibrium emittance of the system can be lower than is otherwise possible.

MANX Demonstration Experiment – Gaseous H2 Absorber for Muon Beam Cooling

Phase I SBIR: 4/2004
The purpose of this collaboration with the Technical Division of Fermilab was to carry out the initial design of a muon cooling demonstration experiment using a helical cooling channel. This work has been superseded by the 6DMANX project.

Helical Cooling Channel – Six-Dimensional Beam Cooling in a Gas Absorber

Phase I SBIR: 4/2003, Phase II SBIR: 7/2004
The purpose of this collaboration with Jefferson Lab is to design and simulate a helical cooling channel. This helical cooling channel consists of solenoidal, helical dipole, and helical quadrupole magnetic fields, with a continuous gas or liquid absorber for muon ionization cooling, with or without RF cavities inside. This channel is capable of cooling in all 6 dimensions of phase space, rather than just the transverse dimensions of ordinary ionization cooling.

High Pressure RF Cavities

Phase I STTR: 4/2002, Phase II STTR: 7/2003
The purpose of this collaboration with IIT is to fabricate and test a high-pressure 805 MHz RF cavity. This cavity provides a significantly larger acceleration gradient than conventional vacuum cavities, because the Paschen effect suppresses emission and sparking. Measurements of breakdown gradient as a function of gas pressure have been made for both hydrogen and helium, using various surfaces (Cu, Mo, Cr, Be).

Papers and Reports

A list of our papers and reports; downloadable.

Job Openings

A list of our current job openings.

Computer Programs

The Low Emittance Muon Collider Workshop - 2009