Professor of Physics
Texas A&M University
Elementary particle physics:
Collider Detector at Fermilab (CDF). CDF is studying the collisions of protons and antiprotons at 2 TeV collision energy - the highest energy ever attained. In 1995, the CDF experiment and its sister experiment D0 discovered the top quark, thought to be the heaviest fermion in nature. Today CDF is seeking signals for the Higgs boson, the particle carrying the scalar field that gives mass to gauge particles, and Supersymmetry, a new field of nature that would provide a natural link from the Standard Model to the unification of the interactions of nature.
Supersymmetry at the Tripler. The proposed Tevatron Tripler would access new physics (eg. Higgs and supersymmetry) primarily through the annihilation of a valence quark and a valence antiquark. By contrast the LHC will access such physics through more indirect channels - gluon fusion and diagrams involving radiated weak bosons. Because of its more direct use of valence quarks, the discovery limit for the Higgs is ~600 GeV, and that for most SUSY channels is ~1,000 GeV, nearly as great as that for the LHC with its much higher beam energy and luminosity. The Tripler would provide a window on new physics that is both competitive with and complimentary to LHC through the coming decade.
Superconducting magnet technology:
12 Tesla superconducting dipoles for Very Large Hadron Collider (VLHC). We are developing a 14 Tesla Nb3Sn dipole suitable for use in a future 50 TeV/beam hadron collider. The dipole contains several innovations: stress management to limit the mechanical stress on the superconducting cable and insulation; conductor optimization in which pure copper strands are cabled with the superconductor to provide quench protection; natural suppression of persistent magnetization, in which a close-coupled steel boundary is used to suppress multipoles generated at injection field from persistent currents in the superconducting strands; and hydraulic preload in which the preload of the coils and the flux return is delivered by pressurizing a bladder filled with low-melt metal and cooling it while maintaining the pressure. The Texas A&M design uses the least amount of superconductor of any high-field design.
Testing of TAMU1: a NbTi model of the VLHC design. A first model of above high-field dipole design has been built and successfully tested at 6.5 Tesla field strength. The dipole reached short-sample limit without training, and exhibited excellent AC loss characteristics. The several construction features needed for the high-field designs were put into practice successfully in this first dipole.
2004 DOE Renewal Proposal
Structured cable using the high-temperature superconductor Bi-2212. We are developing a cable-in-conduit in which 6 mullti-filament strands of Bi-2212 are cabled around a thin hollow Inconel tube, then drawn within a thicker Inconel outer tube. The cable is being developed to make it feasible to wind coils using this fragile material in a wind-and react strategy, without degradation due to strain during operation of the coil. The structured cable protects the fragile strands from mechanical stress during coil winding and operation, permits the strands to re-orient when the cable is bent around small radius bends in a coil, and accommodates closed-circuit refrigeration of the coil.
Particle size sorting for superconducting precursor powders. The performance of multi-filament powder-in-tube superconductors improves as filament size decreases. A controlling technology is the removal of large particles from the powder prior to loading it into the tubes. We are developing a technique to remove all particles larger than ~1 micron from precursor powders, using virtual impact sizing.
Accelerator physics and technology:
The Tevatron Tripler. Fermilab's Tevatron is the highest energy hadron collider in the world today. We have designed a 12 Tesla Nb3Sn dipole, suitable for replacement of the Tevatron's 4 Tesla magnets. The upgrade would triple the collision energy. The Tripler would use the same antiproton source, injector accelerators, cyrogenics, and detectors as the Run II Tevatron. The cost and schedule for a Tripler upgrade would be a small fraction of that for any of the proposed new facilities (NLC, muon collider, VLHC).
Muon Collider. The intense beams of TeV muons in a muon collider beta decay while orbiting, producing a serious problem for heat in the superconducting coils of the storage ring and intense backgrounds in the detectors from muons produced by Bethe-Heitler scattering. We have devised a novel design of the superconducting magnets, in which the decay electrons enter a slot aperture where they are actually transported to the end of each dipole and absorbed at room temperature, making a sufficient angle that secondaries cannot channel through the lattice to the detectors.
Accelerator-driven thorium-cycle fission power. We have developed a conceptual design for an accelerator-driven thorium cycle (ADTC) power reactor which addresses the issues of accelerator performance, reliability, and neutronics that limited earlier designs. It has the virtues that it operates well below criticality, it has sufficient thermal mass that meltdown is impossible, it eats its own long-lived radioactive waste, it cannot produce bomb-capable isotopes, and there are sufficient reserves of thorium to run the Earth's energy economy for a thousand years. In our design, a flux-coupled stack of 7 isochronous cyclotrons is used to deliver a pattern of 800 MeV proton beams. The beams produce fast neutrons by spallation on lead, transmute thorium fuel into U-233, which in turn produces ~GW thermal power.
SiC-Steel metal-matrix composites for reacor fuel rod cladding. In a collateral development, we have developed a concept for a fiber-reinforced stainless steel tube that could survive as a fuel cladding tube for the ADTC reactor (and for other Generation IV reactor technologies). We have succeeded with the first phase of materials development and are planning to increase the scope of development during the coming year.
The Hybrid Dipole and the LHC Tripler. We have applied our techniques of stress management to design a hybrid dipole, with both Bi-2212 and Nb3Sn windings. The dipole would have a short-sample field of 24 Tesla, and would make it feasible to triple the energy of LHC by installing a new ring above the LHC itself in the same tunnel.