| Paper | Title | Page |
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| MOPA008 | On the Feasibility of a Tripler Upgrade for LHC | 634 |
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Funding: This work is supported by the U.S. Dept. of Energy, grant #DE-FG03-95ER40924. Recent developments in the performance of superconductors and the design of high-field superconducting dipoles have opened the possibility to extend dipole field strength to ~25 Tesla in the arc dipoles of a future hadron collider. Design issues are presented for a concept of a Tripler upgrade of LHC, in which a second dual ring would be installed over the LHC ring in the same tunnel. Proton beams from LHC would be transferred to the Tripler midway through the LHC cycle and accelerated to ~20 TeV/beam for collisions. A number of obvious issues are explored. Synchrotron radiation power would be 80 times greater, but the critical energy would come as soft X-rays rather than hard UV, and so could be absorbed locally on ~150 K photon stops following each dipole so that total refrigeration power could perhaps be no more than that for LHC. Synchrotron damping would be dramatically enhanced in the Tripler compared to LHC, with damping times of ~one hour. Alternatives for beam transfer and low-beta insertions will be discussed. Like LHC, the Tripler would access new mass scales primarily through gluon fusion. The Tripler should reach about twice the mass scale attainable with LHC. |
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| TPAP046 | Towards an Optimization of the LHC Intersection Region using New Magnet Technology | 2920 |
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| An optimized design of the intersection region of LHC is presented. The starting point of the design is to move the quadrupole triplet to a minimum distance from the intersect – 12 m. The innermost quadrupole must accommodate substantial heat load from particles, and is designed using a structured cable that incorporates internal refrigeration with supercritical helium. Using the reduced aperture required by this closer spacing, Nb3Sn quadrupoles have been designed with gradients of 350-400 T/m for the triplet. The separation dipole utilizes a levitated-pole design that mitigates the extreme heat and radiation challenges for that application. The above technical elements have been incorporated into an optimized insertion design that minimizes ?* while significantly reducing sensitivities to errors in multipoles and alignment. The additional space that is opened in the lattice can be used to fully localize the optical design of the insertion so that it does not require corrections through the neighboring arcs. | ||
| TPAP047 | Killing the Electron Cloud Effect in the LHC Arcs | 2971 |
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| A getter/electrode assembly has been devised to suppress the regeneration mechanism of the electron cloud effect in the arc dipoles of LHC. The assembly consists of a copper foil electrode, supported through an insulating layer on a stainless steel skid, which would rest upon the flat bottom of the beam screen. The electrode is coated with NEG to provide effective pumping of all non-inert gases from the vacuum. Pumping should be enhanced by electron bombardment. By biasing the electrode ~+100 V secondary electrons produced on the surface would be fully re-absorbed, killing the regeneration mechanism. The NEG surface can be regenerated by passing a current through the electrode to heat it to ~240 C. The heat transfer (radiant + conductive) to the beam screen during regeneration is estimated ~10 W/m, within limits to maintain the beam screen at nominal 20 K temperature during regeneration. The entire assembly has been designed so that installation does not require modification of any hardware currently being built for the LHC arcs. The electrode assembly would occupy 1 mm in the vertical aperture of the beam screen. |