Accelerator Industrialization Research and Development. Muons, Inc. Dr. Rolland Johnson, Co-Principal Investigator. and

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1 Accelerator Industrialization Research and Development by NIU and MI Feb 17, 8 Accelerator Industrialization Research and Development by Muons, Inc. Dr. Rolland Johnson, Co-Principal Investigator and Northern Illinois University Professor David Hedin, Co-Principal Investigator Table of Contents/Overview Table of Contents/Overview... 1 Muon Collider and Neutrino Factory Research for Fermilab s Future... Motivation... Opportunity... Approach... 3 Deliverables... 4 C.V. Rolland P. Johnson... 5 Budget... 7 APPENDIX I: MANX Letter of Intent... 8 APPENDIX II: 8 DOE SBIR Achromatic Interaction Point Design Proposal... 9 Overview Muons, Inc. and Northern Illinois University will generate at least one proposal for federal funding to develop accelerator physics and physics detector technologies to enhance the probability that Fermilab will continue to flourish in Illinois. 1

2 Accelerator Industrialization Research and Development by NIU and MI Feb 17, 8 Muon Collider and Neutrino Factory Research for Fermilab s Future Motivation The Tevatron Collider at the Fermi National Accelerator Laboratory (Fermilab) is currently the highest-energy research tool in the world and Fermilab is the major high energy-physics facility in the United States, but without a new and sustainable project, Fermilab will be made obsolete by higher-energy machines in Europe and Japan. Without a new project, it is not clear that the federal funding of Fermilab would continue. Closure of Fermilab would lead to the loss to Illinois of over $3 million per year in direct federal support to Fermilab and would cost about 3 Illinois jobs. Alternatively, if Fermilab is the site of the next major accelerator project to be undertaken in the U.S., the continued existence of the laboratory is assured and, in addition, billions of dollars for the construction and use of the new accelerator would be added to the State economy. NIU and Muons, Inc. are particularly interested in the health and future prospects of Fermilab as Illinois institutions with close ties to Fermilab. NIU has used Fermilab resources for many research projects and counts heavily on it for collaborations as do many other institutions in Illinois, the US, and the world. Opportunity We believe that the next project at Fermilab will be largely built by industry. If Illinois is properly prepared, it could participate in this industrialization of the tools of basic science. The most likely near-term major project at Fermilab is likely to be a superconducting linear proton accelerator (now known as Project-X) that would be, among other things, a first step to a muon collider and a neutrino factory. While the Project-X will be less than 1B$, an energy-frontier muon collider could be ten times as much. Muon collider technology and its industrialization are the main thrusts of Muons, Inc. research and development. We have a long list of muon collider components that we are developing, some of them like High Field Superconductor, Helical Solenoid magnets, and RF cavities pressurized with dense hydrogen gas, are cutting-edge technologies that are almost ready for industrial partnerships. The NIU-Muons, Inc. collaboration is well suited to the MANX cooling experiment, which will be the demonstration of the sixdimensional muon beam cooling that is required for a muon collider. The design of the interaction regions is also a high-priority for muon collider development. These two potential projects are described below and in the appendices. They each require the beam physics expertise as well as high energy physics detector techniques that are strong points of the Northern Illinois Center for Accelerator and Detector Development.

3 Accelerator Industrialization Research and Development by NIU and MI Feb 17, 8 Approach Muons, Inc. has received almost $7M in DOE High-Energy Physics Small Business Innovation or Small Business Technology Transfer Research (SBIR-STTR) grants primarily to develop technology for a muon collider. Each project has had a research partner, either a university or national laboratory. The table below shows the projects that have been granted in the six years of since Muons, Inc. was started. Muons, Inc Funding and Commercialization History Year Project Title SBIR/STTR non-sbir/sttr Research Revenues source Revenues Partner Company founded Consulting for ICAR* $ 8, IIT -5 High Pressure RF Cavity Development* $ 6,** STTR IIT 3 Consulting for LSU CAMD Light Source* $ 1, LA State 3-6 Helical Cooling Channel Development* $ 85,** SBIR JLab 4-7 Phase Ionization Cooling* $ 745,** SBIR JLab 4-5 MANX Cooling Demo (Phase I only)* $ 95, SBIR Fermilab 4-7 Hydrogen Cryostat* $ 795,** STTR Fermilab 5-8 Reverse Emittance Exchange $ 85,** STTR JLab 5-8 Muon Capture, Phase Rotation, and Precool $ 85,** STTR $ 149,385 Fermilab 6-9 6D MANX Cooling Demo $ 85,** STTR $ 58,3 Fermilab 6-9 G4Beamline Simulation Software $ 85,** STTR IIT 7-8 Stopping Muon Beams $ 1, SBIR $ 1,99 Fermilab 7-8 HCC Magnets $ 1, SBIR $,99 Fermilab 7-8 Compact, Tunable RF $ 1, SBIR $ 1,99 Fermilab Total $ 6,785, $ 563,6 * Completed Projects as of January 8 ** Combined Phase I and Phase II funds (It is thanks to support from the State of Illinois and the Illinois Consortium for Accelerator Research (ICAR) that Muons, Inc. was formed as an Illinois company.) There are several other Federal agencies that could support the work described here. One of the goals of this proposal is to identify the best agencies and programs to use for future funding applications. Many relevant papers and reports can be seen at: 3

4 Accelerator Industrialization Research and Development by NIU and MI Feb 17, 8 Deliverables In the same style as Muons, Inc. has developed SBIR-STTR proposals with other research partners, we will develop at least one proposal for funding with NIU as a research partner to be submitted to the agency most likely to fund the activities as developed in collaboration with the NIU physics and NICADD staffs. Here are two examples that we have started to investigate: 1) An attractive example is to collaborate on the MANX experiment, which has been described as a letter of intent (LOI) to Fermilab and is attached as Appendix I to this document. MANX is a demonstration of a technique for cooling based on the new concept of a Helical Cooling Channel (HCC). Simulations of the HCC have indicated that it can be used to achieve a factor of more than five orders of magnitude reduction in the six-dimensional emittance of a muon beam. The success of the MANX demonstration experiment will lead to confidence that effective muon cooling is possible and that a muon collider is the next logical step toward the energy frontier. Since the LOI was submitted to Fermilab, a new DOE STTR grant has been put in place to develop the experiment and a four-coil prototype section of the magnet that is the heart of the experiment is being constructed at Fermilab to be tested later this year. In this case, a possibility for further funding could be from the DOE or NSF to participate in the experiment, which will be submitted both to Fermilab and to the Rutherford Appleton Laboratory in England. ) Another example is a project to develop the design of the interaction region of a highenergy, high luminosity muon collider and develop the corresponding detector technologies. This project would combine the skills of the NICADD accelerator experts with the physicists and engineers who have participated in the Fermilab D experiment. Because of new concepts that have been promoted by Muons, Inc., such as the low emittance muon collider approach where superior beam cooling allows high luminosity with fewer muons, the interaction region design is unexplored territory. Muons, Inc. has submitted a DOE SBIR-STTR Phase I grant application in collaboration with Yaroslav Derbenev and Thomas Jefferson National Accelerator Facility to start on the interaction region design. The proposal is attached below as Appendix II. Each of these examples involve NIU s accelerator group with their experience in phase space manipulations similar to those needed to cool the muon beam or to design the low beta interaction region of the collider and the NIU HEP group that would develop the detectors and experimental techniques for the MANX experiment or the low beta interaction regions. 4

5 Accelerator Industrialization Research and Development by NIU and MI Feb 17, 8 C.V. Rolland P. Johnson Address: 45 Jonquil Lane, Newport News, VA 366 (757) Roljohn@aol.com Academic Background: U. of California, Berkeley Ph.D., Physics, June 197 U. of California, Berkeley AB, Mathematics, June 1964 Work Experience: Particle accelerator design, construction, operation, and controls. Project Management. DOE funding of R and D. Experimental High Energy Physics Research. Teaching. Employment Background: -Present Scientist-Owner Muons, Inc. (- ) PI of 4 Phase II STTR grants and Phase II SBIR grants Consultant Consulting contracts with CAMD, DOE, DESY, Fermilab, IIT, SRRC Senior Staff Scientist, Thomas Jefferson National Accelerator Facility, (CEBAF) (94-96) On Detail to DOE Headquarters, Germantown MD. Program monitor for 11 university grants. Acting Technical Topic monitor for 1 SBIR grants. Project reviewer. Member SSC equipment reallocation team. (93-94) Head of Instrumentation and Controls Department, CEBAF Accelerator Division, Responsible for Control, Beam Instrumentation, and Safety Systems. Program coordinator for machine commissioning Senior Accelerator Physicist, MAXWELL LABS, Brobeck Division In charge of installation and commissioning the 1.4 GeV CAMD light source at LSU Physicist, FERMI NATIONAL ACCELERATOR LABORATORY (84-91) Tevatron Coordinator for Collider upgrades. Responsible for design, debugging of low beta inserts, e-s beam separation, diagnostics. Invented double-helix beam separation scheme. Discovered decay of persistent currents in superconducting accelerator magnets. Supervised software development. Wrote design programs for RF systems and lattice insertions. Directed machine commissioning. (9-9) Adj. Professor, NIU. Taught "Introduction to Particle Accelerators". (88-9) CDF Experimenter, responsible for CAMAC system, alarms and limits and high voltage control, and integration of the experiment into the accelerator control system. Contributor to luminosity and total cross-section analyses. (88-91) Chairman, Wilson Fellows Committee to recruit, select, nurture extraordinary physicists. Thesis supervisor for two Ph. D. students. Directed experimental accelerator research using the Tevatron. (83-84) Leader of a Tevatron commissioning team. Also wrote programs to control RF, excitation ramps, correction elements, closed orbit, monitor of cryogenics, vacuum. (8-83) Member of antiproton source design group. Coordinated the original design report. Specified energy, location, and stochastic cooling systems. Wrote RF control programs. (8-8) Assignment to CERN, Geneva, Switzerland. Participated in commissioning and initial operation of the Anti-proton Accumulator. Wrote the RF control programs. Improved 1 to GHz stochastic cooling systems. 5

6 Accelerator Industrialization Research and Development by NIU and MI Feb 17, 8 (79-8) Assistant Head of Accelerator Division, in charge of Linac, Booster, Main Ring, Switchyard and Operations Groups. Directed the activity of about 5 people to operate and improve the accelerator fixed target program. Had record intensity levels and reliability. (78-79) E3 experimenter. Leader of a group of Fermilab physicists who collaborated with Princeton and Berkeley to study deep inelastic muon scattering. (75-78) Leader of Booster Synchrotron Group. In charge of the development and operation of the 8 GeV rapid cycling synchrotron. Increased output current by a factor of 3. Built fast bunch-by-bunch transverse dampers to control head-tail instabilities. In charge of H - injection project. Directed RF cavity development projects. (74-75) Member, Main Ring group. Responsible for high field closed orbit of the 4 GEV MR synchrotron. In charge of the 8 GeV transfer line between Booster and MR Physicist, LAWRENCE BERKELEY LABORATORY (7-74) Postdoctoral Research Associate. Bevatron experiments: muon neutrino mass limit, muon range differences, and Kl3 form factors from muon polarization. (7-73) Visiting Scientist IHEP, Serpukhov, USSR. Experiments at the 7 GeV synchrotron on pion-proton interactions. Discovered h o meson. Worked in a Russian group. (67-7) Graduate Student Research Asst. Ph.D. thesis experiment on rare decays of the neutral K-meson at the Bevatron. (63-67) Research Apparatus Operator. Programmer, data analyst. Publications Over 5 references in Accelerator Topics and over 8 in High Energy Physics can be found at Some recent work relevant to this proposal can be found in the reference section of this proposal. COST AND PERFORMANCE OF RAPID-CYCLING PROTON SYNCHROTRONS, C. M. Ankenbrandt and R. P. Johnson, Proceedings of the 1 Particle Accelerator Conference, A LINAC AFTERBURNER TO SUPERCHARGE THE FERMILAB BOOSTER, C. M. Ankenbrandt, J. MacLachlan, M. Popovic, and R. P. Johnson, July, 1. AIP Conf.Proc.64:3-35,3 COMMISSIONING OF THE SYNCHROTRON LIGHT SOURCE AT LSU. R.P.Johnson, et al. Berlin:EPAC 199:197. COMPUTER CONTROL OF RF-MANIPULATIONS IN THE CERN ANTIPROTON ACCUMULATOR. R. Johnson, S. van der Meer, F. Pederson and G. Shering, IEEE Trans. Nucl. Sci. NS-3 No. 4,(1983)9. 6

7 Accelerator Industrialization Research and Development by NIU and MI Feb 17, 8 Applicant: Muons, Inc. GRANT APPLICATION BUDGET APPENDIX C PLEASE READ INSTRUCTIONS BEFORE FILLING OUT THIS FORM A. PERSONNEL (Employees) ROLE IN EST. HOURLY FRINGE TOTAL COST PROJECT HOURS NAME RATE BENEFITS Dr. Rolland Johnson PI 11 $6. 35.% $8,91. Dr. Charles Ankenbrandt Physicist 13 $6. 35.% $1,53. Dr. Richard Sah Physicist 7 $6. 35.% $1,87. Dr. Thomas Roberts Physicist 148 $6. 35.% $11,988. $. $. TOTAL PERSONNEL COST $53,98. B. CONSULTANTS ROLE IN EST. PROJECT HOURS HOURLY NAME RATE $. $. $. $. $. C. LEASED EQUIPMENT (Specify time and Rate, or Other B ITEM AMOUNT $. D. PURCHASED EQUIPMENT ITEM AMOUNT $. E. TRAVEL F. OTHER DIRECT COSTS $. 1. Materials and Supplies. Publication Costs 3. Testing Services (Including work at Government Installations) 4. Computer Services $5,. 5. Research Institution NIU student support $5,. 6. Other Subcontracts 7. Other G. TOTAL DIRECT COSTS (A through F) $58,98. H. INDIRECT COST (Specify Rate and Base).3% covers travel, materials, and all other incidentals. 7 DOE indirect rate. TOTAL INDIRECT COSTS $11, I. TOTAL COSTS (G plus H) $7,13.49 J. FEE OR PROFIT Enter percentage to calculate baed on TOTAL COST (Item I) 7.% $4, K. TOTAL AMOUNT OF THIS REQUEST (Item I plus J) $75,. 7

8 MANX Letter of Intent DRAFT 7/31/7 Updated Letter of Intent to Propose MANX, A 6D MUON BEAM COOLING EXPERIMENT Robert Abrams 1, Mohammad Alsharo a 1, Charles Ankenbrandt, Emanuela Barzi, Kevin Beard 3, Alex Bogacz 3, Daniel Broemmelsiek, Alan Bross, Yu-Chiu Chao 3, Mary Anne Cummings 1, Yaroslav Derbenev 3, Henry Frisch 4, Stephen Geer, Ivan Gonin, Gail Hanson 5, Martin Hu, Andreas Jansson *, Rolland Johnson 1*, Stephen Kahn 1, Daniel Kaplan 6, Vladimir Kashikhin, Sergey Korenev 1, Moyses Kuchnir 1, Mike Lamm, Valeri Lebedev, David Neuffer, David Newsham 1, Milorad Popovic, Robert Rimmer 3, Thomas Roberts 1, Richard Sah 1, Vladimir Shiltsev, Linda Spentzouris 6, Alvin Tollestrup, Daniele Turrioni, Victor Yarba, Katsuya Yonehara, Cary Yoshikawa, Alexander Zlobin 1 Muons, Inc. Fermi National Accelerator Laboratory 3 Thomas Jefferson National Accelerator Facility 4 University of Chicago 5 University of California at Riverside 6 Illinois Institute of Technology * Contact, rol@muonsinc.com, (757) * Contact, jansson@fnal.gov, (63)

9 MANX Letter of Intent DRAFT 7/31/7 Synopsis The Muon Collider and Neutrino Factory Experiment (MANX) that we will propose involves the construction of an innovative superconducting Helical Solenoidal (HS) magnet that is the major component of a momentum-dependent Helical Cooling Channel (HCC). The HCC will be filled with liquid helium ionization energy absorber, instrumented to measure incident and exiting momenta and trajectories, and placed in a muon beam where its six-dimensional (6D) beam cooling properties will be measured and compared to detailed Monte Carlo simulations. The primary goal of the experiment is to test the physics simulation programs to allow longer and more complex muon cooling channels to be designed and built with confidence. The experiment will also verify important new beam cooling and engineering concepts The HCC requires a magnetic field with a helical dipole component to provide dispersion, a solenoidal component to provide focusing, and a helical quadrupole component for increased acceptance. The theory of the HCC using a continuous, homogeneous energy absorber has been published [1] and many simulations have indicated its promise for fast ionization cooling of muon beams for many applications. When used with RF cavities to regenerate the energy lost in the ionization cooling process, the HCC becomes a very efficient cooling method to produce beams for a collider by virtue of its large acceptance and large average energy loss []. Without RF cavities, the magnetic fields of the HCC can be scaled with the momentum of the muon beam as it loses energy in the absorber to produce cooled beams for other uses, including a muon beam precooler, a stopping beam for rare muon decay studies [3], and the MANX demonstration experiment proposed here. The HCC, with and without momentum-dependent fields, the use of a continuous homogeneous absorber without shaped edges to provide emittance exchange to achieve 6D beam cooling, and the HS magnet are inventions of the proponents of MANX. These ideas have been developed under grants by the DOE HEP SBIR-STTR program, where there are two new Phase II grants to develop the MANX proposal including construction of HS prototype coils and to extend the G4Beamline simulation code. Several aspects of the experiment are still under intense development. These include the location (e.g. The Fermilab Mucool Test Area, Meson Lab, or KTeV area, or the Rutherford-Appleton Lab), the momentum of the incident muon beam and length of the HS magnet (5 to 35 MeV/c and 3 to 4 meters), and the up and downstream matching section and spectrometer design and instrumentation. Over the course of the next year while we aggressively develop the HS magnet by designing and constructing prototype coils, we will build a consensus of our collaboration on the most effective experimental design based on extensive simulation studies. The applications of the new techniques that will be developed and demonstrated by this experiment involve very bright muon beams for fundamental research using muon colliders, neutrino factories, and muon beams with new characteristics. The ultimate application will be an energy frontier muon collider which achieves high luminosity by virtue of small emittance rather than large muon flux. The small 6D emittance that is possible as shown by this experiment will allow high-frequency ILC RF accelerating structures to be used for such a collider and also for high flux muon beams for storage ring based neutrino factories. We believe that this experiment may have great significance in determining the future of accelerator science, especially at Fermilab.

10 MANX Letter of Intent DRAFT 7/31/7 MANX, A 6D MUON BEAM COOLING EXPERIMENT Table of Contents Cover Page... 1 Synopsis... Table of Contents... 3 Overview and History... 4 Experimental Goals... 6 Simulation Verification... 6 Emittance Exchange in a Continuous, Homogeneous Absorber... 7 High Pressure RF and the Continuous Absorber Concept... 8 Helical Cooling Channel...1 Recent HCC Simulations with Engineering Contraints Momentum-dependent HCC... 1 HCC Precooling Examples Stopping Muons Beams Helical Solenoid Magnet Technology Emittance Matching to the Helical Solenoid MANX Status Experimental Concept Simulations... G4Beamline... G4MANX... 1 HCC Magnet Development Coil test for the MANX HCC Location, Location... 5 Beamline Possibilities... 5 Detector Development ps Time of Flight... 6 SciFi in LHe... 7 SiPM... 7 Collaboration and Governance... 8 Conclusions... 8 Bibliography and References...8 3

11 MANX Letter of Intent DRAFT 7/31/7 Overview and History The theoretical description of the helical cooling channel (HCC) using a continuous homogeneous absorber [1] has guided several simulation efforts [] which have confirmed the utility of the HCC approach to six-dimensional muon beam cooling. These simulations have involved the use of pressurized RF cavities that continuously replace the energy lost in the ionization cooling process. The ultimate HCC will involve as-yet unproven technologies now under development, namely high-pressure RF cavities and high-temperature superconductor used to produce very high magnetic fields at low temperature. However, we believe that a strong case has already been made that the HCC will be an essential component of any future muon cooling effort and that an experimental demonstration of 6D cooling using a HCC with a continuous absorber is the next step. We call this experiment 6DMANX or simply MANX (Muon collider And Neutrino factory experiment). One innovative idea of the MANX approach of this proposal is to make a demonstration experiment without RF, measuring the 6D beam cooling in a HCC filled with a continuous liquid helium absorber, in terms of invariant emittance. Without RF cavities or the high-pressure hydrogen gas that would normally fill them, MANX is a simpler experiment that can be done relatively quickly and inexpensively. In parallel to the MANX program, we are supporting efforts to incorporate RF cavities into HCC designs for cooling channels where the muon beam momentum is almost constant. The momentum-dependent HCC, where the energy lost in the absorber is not immediately replaced by RF cavities and the magnetic fields are reduced to match the beam momentum, has been developed as a precooler and more recently as a way to increase the yield for stopping muon beams [3]. This momentum-dependent HCC is the basis for the MANX experiment that is the subject of this Updated Letter of Intent. The development of the MANX concept started with a Phase I STTR proposal by Muons, Inc. and Fermilab that was submitted in December of 5, granted and funded in June of 6, and has now been extended to Phase II for $75, and years starting in June of 7: The Phase II proposal [4] contains a description of the ongoing R&D by Muons, Inc. and collaborators on projects that are complementary to MANX as well as several documents that are alluded to below. Working under the Phase I MANX STTR grant and the Phase II funding of another grant with the Fermilab Technical Division, a very novel and strikingly simple design for a momentumdependent HCC magnet was invented. A paper comparing the new design with the conventional approach to such a magnet was given at the 6 Applied Superconductivity Conference. This new HS design based on displaced coils also works well for the original HCC concept, where RF imbedded in the HCC keeps the beam energy relatively constant. Engineering studies are now underway to investigate how to feed the RF wave guides through the HCC coils. Subsequent work on this novel magnet design and additional advances on the MANX matching magnets and the incorporation of RF cavities in the design was reported at PAC7 [5]. 4

12 MANX Letter of Intent DRAFT 7/31/7 A scheme to match the optics of up and downstream spectrometers to the HCC optics was also developed and reported at PAC7 [6]. In May of 6, collaborators from BNL, Fermilab, IIT, Jefferson Lab, and Muons, Inc. submitted a Letter of Intent (LoI) to propose a 6D Muon Cooling Demonstration Experiment to Fermilab. This LoI is included in the MANX STTR Phase II proposal, but is almost obsolete because of developments described below. It was largely composed of material from the Phase I proposal of the STTR project. In June 6, Fermilab Director Pier Oddone formed a Muon Collider Task Force (MCTF) with several tasks including the participation in planning for an experiment to test the HCC concept. (The charge to the MCTF is included in the Phase II proposal [4]). Since then, Muons, Inc. and collaborators have been working with the MCTF to develop a MANX proposal to submit to Fermilab. The MCTF has studied use of the Fermilab MTA as a site for a muon beam suitable to do the MANX experiment. (This is in addition to the 4 MeV proton beam to the MTA to measure the effects of passing beams through RF cavities and energy absorbers.) Other possible sites for the MANX experiment have also been studied, including several locations in the Meson area and the former KTeV area. Studies are also underway to evaluate spectrometer and detector requirements and types of detectors for measuring the effectiveness of the cooling channel in the MANX experiment, e.g. whether it is necessary to have detectors inside the cooling channel energy absorber volume or whether super-fast timing detectors can be used for momentum measurements. A technique to track aggregate ensembles of particles ( beamlets ) is being considered. We also continue to work with the MICE collaboration, and to explore the possibility of testing MANX in a later phase of the MICE experiment at RAL. The MANX experiment is a test of the HCC concept, so it is important to demonstrate the general practicality and effectiveness of the HCC. Significant progress has been made in the development of HCC schemes: a) The high-pressure RF cavity experiment had good results, showing no maximum gradient degradation even in a strong magnetic field [7]. b) The MuCool Test Area (MTA) beam line that will allow radiation testing of the high-pressure RF cavity has been funded and is expected to be installed and operational by the end of 7. c) The design of a series of HCC segments has been improved to operate with less stringent requirements on the magnetic and RF fields [8]. d) A new use of a HCC (which is very similar to the MANX design itself) is being developed to enhance the stopping beam for a muon to electron conversion experiment [3]. During the next year, the collaboration will continue the development of the MANX experiment. We will continue to improve the experimental simulations and carry out the prototyping of the helical solenoid magnet and particle detectors. We will continue to build a collaboration capable of carrying out a convincing, timely, and affordable experiment. We anticipate having a complete experimental proposal with convincing simulations and solid cost estimates in less than a year. 5

13 MANX Letter of Intent DRAFT 7/31/7 Simulation Verification Experimental Goals New ideas have emerged in the past six years that can make muon beams attractive options for future accelerators. Emittance exchange with a continuous homogeneous absorber, helical cooling channels, with and without RF, and the helical solenoid magnet are the explicit items of interest for the MANX project. However, each of these ideas has been tested using the G4Beamline and ICOOL simulation programs and shown to work, at least to the extent that the programs can be trusted and the simulation parameters correspond to physically realizable conditions. That the ICOOL and G4Beamline programs give the same results in those cases which have been closely compared is not surprising. ICOOL is based on the Geant3 (Fortran version) toolkit and G4Beamline is based on the Geant4 (C++ version) toolkit. The same physics processes are expected to be found in both simulation codes. However, it is not clear that there is consistency between versions of Geant that have been used or that the physics models are even good models of reality. Figure 1: Comparison of MuScat data from TRIUMF for scattering of 187 MeV/c muons off of a LH target with two versions of the Geant4 simulation program. As an example, figure 1 shows MuScat experimental results for muon scattering off of hydrogen that were shown in 5 comparing the then new results with two versions of the Geant4 6

14 MANX Letter of Intent DRAFT 7/31/7 simulation program. As can be seen in the figure, both versions of the Monte Carlo overestimate the amount of scattering in the tails. The Geant scattering models have been the subject of debate for some years, and although the resolution of the discussion seems to be settled, the best models are not yet included in the circulated Geant4 toolkit. The tails of the multiple scattering distributions are very important for long cooling channels; in one case of a HCC simulated with Geant4.7, a 6D emittance reduction factor of 5, was increased by a factor of 3 when a model closer to the experimental data was used. In any case, we believe that detailed checks of the simulation programs are the highest priority for the experiment, since the next steps for cooling channels beyond MANX will involve extrapolations in which any errors will be magnified. Emittance Exchange in a Continuous, Homogeneous Absorber The idea that is the basis of the HCC that we advocate is seen in a comparison of figures a and b. Figure a is a conceptual picture of the usual mechanism for reducing the energy spread in a muon beam. The dispersion of the beam generated by the dipole magnet in figure a creates an energy-position correlation at a wedge-shaped absorber. Higher energy particles pass through thicker parts of the absorber and so have more energy loss than particles of less energy. After the absorber the beam becomes more monoenergetic. This process is emittance exchange, as it is sometimes called, because the transverse emittance must grow to allow the longitudinal emittance to be cooled. In figure a, the beam is in vacuum except in the wedge absorber. Subsequent RF cavities, also in vacuum, replace the energy lost in the absorber. The process is limited by multiple scattering in the absorber and the high-z windows that isolate the evacuated RF cavities and that contain the absorbers. Figure.. a) Wedge Absorber Technique b) New Homogeneous Absorber Technique. In previous cooling plans, both the emittance exchange process and the transverse ionization beam cooling processes have been implemented by sequentially alternating absorbers and 7

15 MANX Letter of Intent DRAFT 7/31/7 evacuated RF cavities. Moreover, the usual 6D schemes require sequential use of wedge absorbers for emittance exchange followed by unshaped absorbers for transverse cooling followed by RF cavities to regenerate the lost energy. One idea to be tested in MANX, shown schematically in figure b, is that a simple scheme of a continuous absorber in a dispersive magnetic field can be used to perform longitudinal cooling. In this case the energy loss depends on the de/dx of the continuous absorber, where the longer path length of the higher momentum particles performs the same function as the wedge in figure a. The origin of this idea followed from the concept of pressurized RF cavities in which the hydrogen gas filling the cavity acts both as the energy absorber for ionization cooling and as an absorber for dark currents to allow higher accelerating gradients. High Pressure RF and the Continuous Absorber Concept Figure 3: Measurements of the maximum stable Test Cell gradient as a function of hydrogen gas pressure at 8 MHz with no magnetic field for three different electrode materials, copper (red), molybdenum (green), and beryllium (blue). As the pressure increases, the mean free path for ion collisions shortens so that the maximum gradient increases linearly with pressure. At sufficiently high pressure, the maximum gradient is determined by electrode breakdown and has little if any dependence on pressure. Unlike predictions for evacuated cavities, the Cu and Be electrodes behave almost identically while the Mo electrodes allow a maximum stable gradient that is 8% higher. The cavity was also operated in a 3 T solenoidal magnetic field with Mo electrodes (magenta); these data show no dependence on the external magnetic field, achieving the same maximum stable gradient as with no magnetic field. This can be compared with measurements of 85 MHz evacuated cavities that show the maximum surface gradient is reduced from 5 MV/m to about 15 MV/m at an external magnetic field of 3 T. 8

16 MANX Letter of Intent DRAFT 7/31/7 Figure 3 displays results from tests at the MTA that show that pressurized cavities have an advantage over usual cavities that operate in vacuum in the strong magnetic fields that provide the strong focusing required for effective beam cooling. In a 3 Tesla field, the maximum stable gradient of the Muons, Inc. 8 MHz test cell showed no maximum gradient degradation, while an evacuated cavity had reduced performance under similar conditions. Additionally, the dual use of the real estate for energy absorption by the hydrogen and for energy regeneration by the RF cavities can be an important feature for cooling channels requiring the highest muon flux where the muon lifetime is relevant. Experiments at the Fermilab Mucool Test Area are underway to test the concept of RF cavities pressurized with hydrogen gas. The next important step will be tests of pressurized RF in an intense radiation environment. A 4 MeV proton beam line is being installed in the MTA and an experimental program to develop pressurized RF suitable for operation in a muon cooling channel should start early in 8. In addition to the test cell used for the measurements in figure 3, a new pressurized RF cavity is being designed, which will be more like a conventional cavity with new features to mitigate breakdown and tune changes that may be caused by the bright beam in a muon cooling channel. This idea of filling RF cavities with gas is new for particle accelerators and is only possible for muons because they do not scatter as do strongly interacting protons or shower as do lessmassive electrons. Although the MANX experiment supports the use of a HCC filled with hydrogen-filled RF cavities, the experiment itself does not require RF cavities and, in addition, also supports an alternative to the gas filled RF cavity approach to 6D cooling, where HCC sections much like MANX would alternate with sections of conventional evacuated RF cavities. 9

17 MANX Letter of Intent DRAFT 7/31/7 Helical Cooling Channel In order to cool the 6D emittance of a beam, the longitudinal emittance must be transferred to transverse emittance where ionization cooling is effective. This emittance exchange is accomplished in the HCC by superimposing a transverse helical dipole magnet and a solenoidal magnet to make possible longitudinal as well as transverse cooling. The helical dipole magnet creates an outward radial force due to the longitudinal momentum of the particle while the solenoidal magnet creates an inward radial force due to the transverse momentum of the particle, or Fh dipole pz B ; b B F p B ; B B solenoid z z (1) where B is the field of the solenoid, the axis of which defines the z axis, and b is the field of the transverse helical dipole at the particle position. These Lorentz forces are the starting point for the derivations of the stability conditions for particle motion discussed in reference [1]. By moving to the rotating or helical frame of reference that moves with the field of the helical dipole magnet, a time and z-independent Hamiltonian is then developed to explore the characteristics of particle motion in the magnetic fields of the channel. After this, a continuous homogeneous energy absorber is added along with the continuous RF cavities needed to compensate for the energy loss and thus maintain the radius of the equilibrium orbit. Equations describing sixdimensional cooling in this channel are also derived, including explicit expressions for cooling decrements and equilibrium emittances. Figure 4: Illustration of motion of the beam about the z-axis (black), which coincides with the solenoid center. For a given momentum, muons (blue) oscillate about the periodic equilibrium orbit (red). This view in perspective shows muons as they oscillate about the equilibrium orbit for three helix periods. Some of the actual theoretical development of this cooling channel was worked out some years ago by Derbenev [9]. In that work, the absorber was seen as composed of a homogeneous part and a part with a density gradient. Since the thinking at the time was that the wedge absorber 1

18 MANX Letter of Intent DRAFT 7/31/7 scheme shown in Figure a should be dominant, especially in that discrete absorbers were always envisioned, the contributions from the homogeneous absorber were not considered as significant. The ideas and mathematical descriptions become more transparent in the case of a continuous homogeneous absorber. Much of the conceptual simplicity is lost in the case of discrete absorbers that must be carefully placed between magnetic coils and between RF cavities. For a given beam momentum, one can vary the solenoid field and the strength and period of the helical dipole field. (The hydrogen gas energy-absorber density is also a free parameter provided the density is sufficient to suppress RF breakdown at the required level.) The helical field that must be superimposed on the solenoidal field must have a quadrupole component in addition to the dipole component in order to give the beam additional stability. This component could be added with cos θ quadrupole magnets having the same twist period as, and superimposed on, the helical dipole coils. Or, as we have learned in the last year, all three components can be provided by a helical solenoid magnet. It is important to note that the direction of the solenoidal field does not change in the cooling channel described below. This is an essential difference between the helical dipole method and the solenoidal schemes with alternating field directions that have been envisioned up to now. This may also be some technical advantage to the extent that the large magnetic forces on the superconducting coils at the field reversal regions can be eliminated. Although a discussion of technical issues should follow the complete analysis of beam dynamics and cooling, we note that the use of continuous (or long) solenoids inherent in the helical concept should allow a higher maximum effective longitudinal field than that of schemes with alternating solenoidal field directions. Consequently, the helical scheme will achieve a smaller equilibrium emittance, faster cooling rate, and decreased particle loss from decay. The HCC incorporating hydrogen filled RF cavities will provide the fastest possible muon beam cooling because it will have the highest possible gradients due to the breakdown suppression of the dense gas in a magnetic field and because the same gas simultaneously acts as the energy absorber. Parametric-resonance Ionization Cooling and Reverse Emittance Exchange [1], new techniques for muon beams to get transverse emittances that are as small as those used in proton or electron colliders, are being investigated. In these schemes, a linear channel of dipoles and quadrupole or solenoidal magnets periodically provides dispersion and strong focusing at the positions of beryllium wedge absorbers. Very careful compensation of chromatic and spherical aberrations and control of space charge tune spreads is required for these techniques to work. And most important with respect to the MANX experiment being proposed here, the initial emittances at the beginning of the periodic focusing channel must be small in all dimensions. Thus the HCC is the key to extreme muon beam cooling and to the Low Emittance Muon Collider [11]. Recent HCC Simulations with Engineering Constraints The original HCC simulations assumed a MHz Pressurized Linac surrounded by coils to produce the required fields. No real engineering limitations were applied and the transverse acceptance was large (~4, mm-mr, normalized) and the 6D cooling factor for a large 11

19 MANX Letter of Intent DRAFT 7/31/7 absorber density and 5 MV/m RF gradient was better than 1 5. Recent simulations of cooling channels have been more realistic, with lower RF gradients, cavities that could fit inside buildable helical solenoidal coils, and magnetic fields that could be created by tested superconductors. An example was shown in the Low Emittance Muon Collider workshop [1] A new Phase I SBIR grant to Muons, Inc. and Fermilab starting in June 7 is to develop the magnet systems for a series of HCC segments that take advantage of the reduced size of the beam as it cools. As the beam becomes smaller, the HCC dimensions can be reduced allowing stronger magnetic fields and higher frequency RF. Momentum-dependent HCC As discussed in the section above, the results of analytical calculations and numerical simulations of 6D cooling based on a HCC are very encouraging. In these studies, a long HCC encompasses a series of contiguous RF cavities that are filled with dense hydrogen gas so that the beam energy is kept nearly constant, where the RF continuously compensates for the energy lost in the absorber. In this case, the strengths of the magnetic solenoid, helical dipole, and quadrupole magnets of the HCC are also held constant. This feature of the HCC channel is exploited in the mathematical derivation of its properties, where the transverse field is subject only to a simple rotation about the solenoid axis as a function of distance, z, along the channel. This rotational invariance leads to a z and time-independent Hamiltonian, which in turn allows the dynamical and cooling behavior of the channel to be examined in great detail. An important relationship between the momentum, p, for an equilibrium orbit at a given radius, a, and magnetic field parameters is derived in reference [1]: 1+ κ 1+ κ p( a) = B b k κ () where B is the solenoid strength, b is the helical dipole strength at the particle position, k is the helix wave number ( k = π / λ ), and κ ka = p / pz is the tangent of the helix pitch angle. Equation () is not just a description of the requirements for a simple HCC, but is also a recipe to manipulate field parameters to maintain stability for cases where one would like the momentum and/or radius of the equilibrium orbit to change for various purposes. Examples of these purposes that we have examined include: 1) a precooling device to cool a muon beam as it decelerates by energy loss in a continuous, homogeneous absorber, where the cooling can be all transverse, all longitudinal, or any combination; ) a device similar to a precooler, but used as a full 6-dimensional muon cooling demonstration experiment (this MANX idea is the subject of this proposal); 1

20 MANX Letter of Intent DRAFT 7/31/7 3) a transition section between two HCC sections with different diameters. For example, this can be used when the RF frequency can be increased once the beam is sufficiently cold to allow smaller and more effective cavities and magnetic coils; and 4) an alternative to the original HCC filled with pressurized RF cavities. In this alternate case, the muons would lose a few hundred MeV/c in a HCC section with momentum dependent fields and then pass through RF cavities to replenish the lost energy, where this sequence could be repeated several times. 5) a means to increase the rate of stopping muons for rare muon decay searches. 6) a muon decay channel. The HCC can be looked at as the equivalent of a synchrotron in that it has an effective gamma-t such that a momentum compaction factor is one of its characteristics. Studies that have just begun are aimed at taking advantage of this to limit the time spread of the muons at the end of a decay channel to improve the capture rate for muons that can be eventually gathered into a single bunch for a muon collider. Additional constraints to equation () are needed to determine the cooling properties of the channel. For example, to achieve equal cooling decrements in the two transverse and the longitudinal coordinates: k c 1+ κ q 1 = β k 3 β (3) where kc = B 1+ κ / p is related to the cyclotron motion, q is an effective field index, and β = v/ c. Another example, to achieve a condition where all the cooling is in the longitudinal direction, is to require that: ˆ pda 1 + κ D = and q =. adp κ HCC Precooling Examples Figure 5 shows the G4BL simulation of a combination decay (4 m) and precooler (5 m) HCC example. Pions and muons are created in the vacuum of the decay channel and captured in the HCC. At the end of the decay region, the muons pass through a thin aluminum window into a region of liquid energy absorber. By having a continuous HCC for the two sections, the problem of emittance matching into and out of the precooler has been avoided. Simulation studies of various precooler dimensions and magnet strengths have been done. Figure 6 shows the normalized average transverse, longitudinal, and 6D emittances plotted as a function of the distance down the channel indicating the effect of liquid hydrogen and liquid helium and the effects of the aluminum containment windows of a 6 m long precooler section. In this simulation, 4 MeV/c muons are degraded to less than MeV/c in making 6 turns in a HCC filled with liquid hydrogen or liquid helium, without or with 1.6 mm aluminum windows on each end of the section. Far above the equilibrium emittances, the cooling with liquid helium 13

21 MANX Letter of Intent DRAFT 7/31/7 absorber is almost as good as with liquid hydrogen and the aluminum windows do not significantly degrade the cooling. Figure 5: G4BL display of a pion decay HCC (light blue) followed by a 5 m precooling (white) HCC. The top display shows the whole layout, the lower left display is the beginning of the decay channel, and the lower right display shows the precooler end. The red and blue lines show the pion and muon tracks, respectively. The helix period is 1 meter. 14

22 MANX Letter of Intent DRAFT 7/31/7 The settings of the helical dipole and quadrupole magnets and the solenoid are chosen to give equal cooling decrements in all three planes. The combined 6D cooling factor is 6.5 for liquid helium and 8.3 for liquid hydrogen. The improved performance of this HCC simulation relative to designs in which short flasks of liquid absorber alternate with RF cavities comes from the effectiveness of the HCC, from the greater path length in the absorber ( 6/cos(45 ) = 8.5 m), and from less heating by the high-z windows. MICE, for example, has several aluminum windows for hydrogen containment and separation from RF cavities, while the two thin windows needed for this precooler design are negligible in their heating effect compared to the length of the liquid absorber. This precooling example inspired the idea of a 6D cooling demonstration experiment that is described below. In fact, the device that we propose to design as a 6D demonstration experiment also serves as a precooler prototype. Figure 6: Simulations showing normalized emittance evolution for particles that survive to 6 m for a HCC precooler filled with liquid hydrogen (blue) or liquid helium (red), with (dashed) and without (solid) 1.6 mm thick aluminum windows on each end. The reduced cooling factors of MANX designs discussed later relative to this precooling example reflect compromises in parameters such as initial momentum and length of the HCC and also less than perfect emittance matching. 15

23 MANX Letter of Intent DRAFT 7/31/7 Stopping Muons Beams Muons, Inc. and Fermilab have received a Phase I SBIR grant to study the use of cooling techniques to develop effective muon stopping beams. In the proposal for this grant a preliminary study indicated that a MANX-like HCC channel could increase the flux of stopping muons in the MECO experiment by a factor of five, essentially by shifting the higher flux region of the muon production spectrum downward to lower momentum. Simultaneous momentum cooling is required when the energy is degraded to prevent the natural momentum heating that is a consequence of the unfavorable slope of the de/dx as a function of momentum curve. A paper describing this study was reported at PAC7 [3]. The Phase I grant will be to develop the concept described above and to study mitigation approaches to suppress backgrounds for rare event searches. In the Phase II proposal we expect to be able to push the idea of beam cooling for better stopping beams further, where more beam cooling using RF regeneration in the cooling channel can produce even brighter stopping beams. Such a cooling channel would be a natural step to the cooling channels needed for a muon collider or high-energy neutrino factory. Helical Solenoid Magnet Technology Figure 7: Conceptual picture of a HCC segment using the helical solenoid, which provides solenoidal, helical dipole, and helical quadrupole fields. Although at first glance it looks like a slinky child s toy, the coils are independent rings. For the MANX simulation shown in the next figures below, each ring diameter is.5 m and ~6 coils are used for the 3. m long HCC that would fit in the MTA enclosure. 16

24 MANX Letter of Intent DRAFT 7/31/7 A very buildable magnetic coil arrangement, with only one quarter the field volume of the original HCC concept, has been invented that applies to all HCC designs, including MANX with its z-dependent field strengths. The simple scheme shown in figure 7 is sufficient to create the three essential HCC magnetic field components: solenoidal, helical dipole (as in the Siberian Snake), and helical quadrupole. (Although we have added a helical sextupole in some of the simulations, the sextupole typically improves the acceptance by only 1% and is not needed for MANX.) Emittance Matching to the Helical Solenoid A scheme to match the optics of the MANX HCC to any solenoidal beam transport system has been created and used to simulate the MANX experiment. The field profiles for the combined matching and HCC section from one of the studies is shown in figure 8. The factor of two 6D cooling performance for this configuration is shown in figure 9. This factor is less than the factor of 8.3 for the hydrogen filled or 6.5 of the helium-filled precooling examples discussed above which have perfect matching since they follow a HCC decay section. The 6D cooling factor shown bellow is also less than the 3.7 of earlier studies because the length of the HCC has been reduced to fit in the available space in the MTA location and the matching is not completely optimized. Figure 8: Field strength components along the reference orbit used in MANX cooling simulations. 17

25 MANX Letter of Intent DRAFT 7/31/7 Figure 9: Emittance evolution in the MANX emittance matching and cooling sections as simulated in G4Beamline. 18

26 MANX Letter of Intent DRAFT 7/31/7 Experimental Concept MANX Status The ultimate goal of the experiment is to build a HCC cooling channel magnet using available technology and to use it in a muon beam to make a striking demonstration that exceptional 6D beam cooling is technically feasible. MANX will demonstrate the use of a HCC with a continuous homogeneous absorber to achieve emittance exchange and 6D cooling. Contrary to previously described demonstration experiments, including MICE and a previous SBIR project using high-pressure hydrogen-filled RF cavities, we have eliminated the RF cavities altogether in order to reduce the cost and complexity of the experiment. Implicit in this approach is that the experiment need only demonstrate the reduction of the invariant normalized emittances. The elimination of the RF component of the experiment will ultimately simplify the analysis of the results and will demonstrate the effectiveness of the cooling plan without the added complication of RF acceleration. Without the RF cavities in the HCC, there is no reason to use the dense gas that was originally envisioned to allow high RF gradients. This means that we do not need to use cold, high pressure hydrogen. In fact, liquid hydrogen or helium will provide the continuous energy absorber that we need, without the need for thick windows that would be required for high-pressure gaseous absorber and would degrade the cooling performance of the demonstration. In the following discussion we assume that the measurements will be of single particles, using the same technique that has been adopted by the MICE collaboration. We note, however, that the beam cooling performance of the HCC should be good enough that we can consider measurements of ensembles of particles as another method that may be complementary to the single particle approach. Beam Spectrometer and Matching Section Liquid Helium filled HCC Spectrometer and Matching Section Calorimeter Figure 1: Generic diagram of the MANX experiment. A generic diagram of the MANX experiment is shown in figure 1. An incident beam of muons with momentum around 3 MeV/c passes through an upstream spectrometer where the trajectory, time, and momentum of each particle are measured. A matching section, which may be integrated with the spectrometer, then brings the beam to match the HCC acceptance. The beam then passes through a thin window that contains the liquid helium of the HCC. The beam passes through the liquid helium filled HCC where the momentum is degraded and 6D cooling occurs. The ~15 MeV/c beam exits the HCC through another thin window into the matching and spectrometer sections and is stopped in the calorimeter. Timing counters and Cherenkov 19

27 MANX Letter of Intent DRAFT 7/31/7 counters in the spectrometer sections and the calorimeter at the end of the channel will be used for particle identification. This spectrometer can be based on conventional quadrupole and dipole Cartesian coordinates or based on a solenoidal geometry as is done in MICE. The matching section then depends on which spectrometer type is chosen. Simulations G4Beamline Figure 11 shows the equivalent G4Beamline simulation result for the MTA version of the experiment as taken from the PAC7 paper [], where more details are available. Figure 11: G4Beamline display of the MANX cooling section (red) and the two emittance matching sections (blue). The helical solenoid magnets shown in red enclose the LHe ionization energy absorber, which is separated from the vacuum of the matching sections by thin Al windows. The beam is physically larger after cooling because it has less momentum than the incoming beam; the normalized emittance has been reduced.

28 MANX Letter of Intent DRAFT 7/31/7 G4MANX G4MANX is a program package cloned from G4MICE, the code used in the MICE experiment. We have capitalized on the work done by the MICE collaboration in implementing Geant4 into a framework for advanced accelerator and detector simulation and particle track reconstruction. G4MANX is being developed as a suite of packages which include simulation, digitization, reconstruction and analysis of muon events for a demonstration of 6D ionization cooling. The simulation package uses the CERN Geant4 toolkit and provides for the generation and tracking of muons through the MANX spectrometer and detectors. We will continue the development of the G4Beamline simulation program and use G4MANX to optimize experimental parameters by improving experimental statistical significance, understanding systematic errors, and exploring engineering simplifications and their ramifications. The Simulation package will be used to model the different scenarios for the implementation of MANX. A first case implementation models the experiment that could be performed at the Rutherford-Appleton Laboratory using the MICE beam line where the MICE absorber and RF units are replaced by the MANX helical cooling channel and its associated matching sections. Figure 1 shows a sketch of the layout for MANX at RAL. In the figure, the orange rectangles illustrate the MICE modules that would be used by MANX. These include the MICE spectrometer, TOF detectors and beam line magnets. Shown in the red and salmon colored rectangles are the modules added for MANX. A number of SciFi detector planes similar to those used in MICE spectrometers have been added to the HCC and the matching sections. The Digitization package takes the muon tracks from the Geant4 simulation and produces a simulated detector response. The Reconstruction package constructs the muon track from the digitization and produces a summary file that describes the track information which is to be used in the analysis. The initial track parameters can be obtained with reasonably good resolution in the MICE spectrometers. The track parameters at and inside the cooling channel are obtained by propagating the track through the non-uniform fields in the matching section and in the HCC using a Kalman filter [13]. The measurements from the planes inside the LHe-filled HCC will have good spatial resolution, but must rely on extrapolation for momentum determination because of multiple scattering. For Phase II we intend to model alternative MANX cases with the G4MANX packages to describe single particle and beamlet experiments that could be performed at Fermilab. We will also develop the Digitization and Reconstruction packages for the MANX experiment. These will be necessary to evaluate cooling channel and detector systematic errors, determine emittance measurement resolutions and optimize cooling performance for the MANX ionization cooling experimental proposal. 1

29 MANX Letter of Intent DRAFT 7/31/7 Figure 1: Sketch of RAL MICE muon beam line (violet) with MANX LHe-filled helical cooling channel (red) and evacuated matching sections (salmon) positioned between MICE spectrometers (brown). The dimensions are in cm. Figure 13 shows a picture of a typical muon in G4MANX that is traversing the matching and cooling sections of MANX. The red cooling section is filled with liquid helium. The magnetic channel, through which the muons travel, is made of short solenoid current rings. G4MANX forms the magnetic field from a field description of the individual rings. Figure 13: Graphics from G4MANX that show a muon (blue) traversing the MANX matching and cooling section shown in red and the MICE spectrometers in the blue boxes.

30 MANX Letter of Intent DRAFT 7/31/7 HCC Magnet Development The MANX collaboration is working with the Fermilab Technical Division to accomplish the engineering of the HCC and emittance-matching magnet systems, including construction and testing of a three-coil demonstration magnet for the superconducting helical solenoid. 3-Coil test for the MANX HCC. The 3-coil demonstration magnet program goals are to: 1) Build three model coils for a possible MANX Helical Solenoid. The geometry of the coils must satisfy the present design requirements for the MANX muon beam cooling experiment, and also fit within the dewar of the Technical Division Vertical Magnet Test Facility (VMTF). ) Build a mechanical support structure for the test coils that will simulate the geometry of the solenoids in the MANX configuration, again within the space constraints of the test facility cryostat. 3) Develop a magnetic measurement system for characterizing and validating the 3 coil field and monitoring field stability during current excitation. 4) Test the 3-coil system in liquid helium, utilizing the full test capabilities of the Fermilab VMTF. This program will have many benefits to the MANX program to build a full scale helical cooling channel. First, the tooling to make the coils and the coil manufacturing procedures of the engineering design will be directly applicable for the full scale MANX solenoid. The coil manufacturing process is a major time and cost driver for the full scale magnet and the 3-coil test will thus reduce the uncertainty and required contingency in the final project. Second, the mechanical support structures and the measuring system for the 3-coil test are directly applicable to full scale MANX. The mechanical structure is dominated by the forces from adjacent coils, with the end coils likely having the largest asymmetric forces. Finally, these coils can be used to do magnet studies that would be too costly or involve too much program risk for the full scale magnet. Studies include quench protection, complicated by strong field coupling of adjacent coils, and powering schemes for individual coils to compensate for the required momentum or z dependent field variation due to de/dx loss. It is also possible to safely study the magnet response due to certain error conditions such as quench detection failure. We will design the support structure so that the center coil of the 3 coils will be easily replaceable, allowing QA tests of production coils for the full scale MANX Helical Solenoid. Plan Details: Figures 14 and 15 show a schematic of the 3-coil test geometry. The coils will be modular and will operate in liquid helium. 3

31 MANX Letter of Intent DRAFT 7/31/7 Coil design manufacturing: We propose to use existing NbTi cable from the Fermilab cable inventory. Tooling will be designed to wind the cable on a stainless steel mandrel. Detailed mechanical/field calculations will guide the design of the coil mechanical structure, however, it is most likely that the coils will be potted, or a radial restraining ring will be needed to accommodate the expected hoop stress. Support structure: The support structure will be designed to accommodate the expected 3 kn longitudinal forces and ~ kn transverse restoring forces. The dewar dimensions are approximately 6 mm in diameter and 4 mm in length. Coil offset will be accomplished by mounting the rings perpendicular to the gravity/dewar axis. Figure 14: Geometry of the 3-coil test, configured for VMTF dewar. The insert shows predicted forces during operation. Test interface/magnetic field: Magnets tested in a vertical dewar cryostat are typically tested using a top hat, which serves as the room temperature interface of the helium volume. The magnet is hung from support rods from this top hat plate. Power leads and instrumentation feedthroughs come through top hat penetrations. For these tests we will use an existing top hat built for the VMTF. The modification to the plate and mechanical interfaces are financially supported through this proposal. As these coils have a very wide aperture and will be mounted transversely to the top hat, the traditional magnetic 4

32 MANX Letter of Intent DRAFT 7/31/7 measurement systems for accelerator magnets will not work well here. A new system, possibly an array of hall probes operating in liquid helium will be used. Tests will be performed in the Fermilab VMTF, using as much as possible of the existing test infrastructure, such as power supplies, quench detection and energy extraction circuitry, and helium refrigerator plant. The test program will take approximately weeks, depending on the quench performance of the magnet. The test will consist of the operation of the coils at full operational field. Magnetic measurements will be performed to determine field quality. Strain gauges will be used to determine the mechanical stress of the coils and coil support structure. Figure 15: Side view showing dimensions of coil structure for the VMTF test. Location, Location New collaborators were identified during the second Low Emittance Muon Collider Workshop (Feb 1-16, 7, The cover sheet of this updated LoI contains the names of those who have agreed to participate, although we anticipate that more will join before the experimental proposal is ready to submit. In the meantime we have looked for appropriate places to carry out the experiment at Fermilab, RAL, LANL, ANL, and Oak Ridge. Where the experiment will be done is an important aspect of forming a collaboration and we want to find the best site as soon as possible. Beamline Possibilities Muons, Inc. and the Fermilab MCTF have been investigating several possible beams at Fermilab that could be suitable for the MANX experiment. In addition Muons, Inc. has been a participant 5