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Mokhov, N.V.

Paper Title Page
MPPT049 Optimization of Open Midplane Dipole Design for LHC IR Upgrade 3055
 
  • R.C. Gupta, M. Anerella, A. Ghosh, M. Harrison, J. Schmalzle, P. Wanderer
    BNL, Upton, Long Island, New York
  • N.V. Mokhov
    Fermilab, Batavia, Illinois
 
  Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-98CH10886.

The proposed ten-fold increase in Large Hadron Collider (LHC) luminosity requires high field (~15 T) magnets that are subjected to the high radiation power of ~9 kW/per beam directed towards each interaction region. This has a major impact in the design of first dipole in the "Dipole First" optics. The proposed design allows sufficient clear space between coils so that most of the particle showers from the interaction points (concentrated at the midplane due to strong magnetic field) can be transported outside the coil region to a warm absorber thus drastically reducing the peak power density in the coils and removing heat at a higher (nitrogen) temperature. The concept, however, presents several new technical challenges: (a) obtaining good field quality despite a large midplane gap, (b) minimizing peak fields on coil, (c) dealing with large vertical forces with no structure between the coils, (d) minimizing heat deposition in the cold region, (e) designing a support structure. Designs with different horizontal and vertical coil spacing are presented that offer significant savings in the operating and infrastructure cost of the cryo-system, providing reliable quench-stable operation with a lifetime of the critical components of at least ten years.

 
MPPT083 Radiation Damage to Advanced Photon Source Undulators 4126
 
  • S. Sasaki, C. Doose, E.R. Moog, M. Petra, I. Vasserman
    ANL, Argonne, Illinois
  • N.V. Mokhov
    Fermilab, Batavia, Illinois
 
  Funding: Supported by the U.S. DOE Office of Science under Contract No. W-31-109-ENG-38.

Radiation-induced magnetic field strength losses are seen in undulator permanent magnets in the two sectors with small-aperture (5 mm) vacuum chambers. Initially, simple retuning of the affected undulators could restore them to full operation. As the damage has accumulated, however, it has become necessary to disassemble the magnetic arrays and either replace magnet blocks or remagnetize and reinstall magnet blocks. Some of the damaged magnet blocks have been studied, and the demagnetization was found to be confined to a limited volume at the surface close to the electron beam. Models for the magnetic damage were calculated using RADIA* and were adjusted to reproduce the measurements. Results suggest that a small volume at the surface has acquired a weak magnetization in the opposite direction. Small magnet samples provided by NEOMAX and Shin-Etsu are being placed in the storage ring tunnel for irradiation exposure testing. Simulations of the radiation environment at the undulators have been performed.

*O. Chubar, P. Elleaume, J. Chavanne, J. Synchrotron Radiat. 5, 481 (1998).

 
TPAP035 Energy Deposition Issues at 8 GeV H- Beam Collimation and Injection to the Fermilab Main Injector 2372
 
  • A.I. Drozhdin, M.A. Kostin, N.V. Mokhov
    Fermilab, Batavia, Illinois
 
  The energy deposition and radiation issues at 8 GeV H- beam collimation in the beam transfer line and at stripping injection to the Fermilab Main Injector are analyzed. Detailed calculations with the STRUCT and MARS15 codes are performed on heating of collimators, stripping foils and other critical components, as well as on beam line and accelerator element radioactivation both at normal operation and accidental beam loss. Extraction of the unstripped part of the beam to the external beam dump and loss of the excited-state Ho atoms in the Main Injector are also studied.  
RPPP048 Beam Collimation and Machine-Detector Interface at the International Linear Collider 2995
 
  • N.V. Mokhov, A.I. Drozhdin, M.A. Kostin
    Fermilab, Batavia, Illinois
 
  Funding: Work supported by the Universities Research Association, Inc., under contract DE-AC02-76CH03000 with the U.S. Department of Energy.

Synchrotron radiation, spray from the dumps and extraction lines, beam-gas and beam halo interactions with collimators and other components in the ILC beam delivery system create fluxes of muons and other secondaries which can exceed the tolerable levels at a detector by a few orders of magnitude. It is shown that with a multi-stage collimation system, magnetized iron spoilers which fill the tunnel and a set of masks in the detector, one can hopefully meet the design goals. Results of modeling with the STRUCT and MARS15 codes of beam loss and energy deposition effects are presented in this paper. We concentrate on collimation system and mask design and optimization, short- and long-term survivability of the critical components (spoilers, absorbers, magnets, separators, dumps), dynamic heat loads and radiation levels in magnets and other components, machine-related backgrounds and damage in collider detectors, and environmental aspects (prompt dose, ground-water and air activation).