Accelerator Technology

Target Technology

Paper Title Page
RPPE018 Material Damage Test with 450 GeV LHC-Type Beam 1607
  • V. Kain, J. Ramillon, R. Schmidt, K.V. Vorderwinkler, J. Wenninger
    CERN, Geneva
  The design of LHC protection elements is based on assumptions on damage levels, which are derived from simulations. A dedicated experiment was prepared and carried out to cross-check the validity of this approach by trying to damage material in a controlled way with beam. The impact of a 450 GeV beam extracted from the SPS on a specially designed high-Z target with a simple geometry, comprising several typical materials used for LHC equipment, was simulated. The beam intensities for the test were chosen to exceed the damage limits of parts of the target. Results of the simulations are presented and compared with test results.  
RPPE026 Operating Experience with Meson Production Targets at TRIUMF 1919
  • E.W. Blackmore, A.S. Dowling, R. Ruegg, M.C. Stenning
    TRIUMF, Vancouver
  High power targets are now required for operation at beam powers in excess of 1 MW for spallation neutron sources and neutrino factories. TRIUMF has been operating beryllium and graphite meson production targets for many years. Although the proton beam power of 100 kW at 500 MeV is lower, the beam densities and fluences are higher than most operating solid targets as other accelerators use rotating targets or larger beam spots. The beam size on the TRIUMF targets is maintained at 0.15 cm2 and this beam density leads to proton fluences of 1·1023 protons/cm2 per year. The beryllium targets are rectangular rods immersed in a water-cooled stainless steel jacket. The pyrolytic graphite targets consist of pie-shaped segments bonded to a water-cooled copper saddle. Operating experience shows that the graphite targets suffer thermal damage above beam currents of 120 uA but will operate for long periods at 100 uA. The beryllium targets can operate to 200 uA and appear to survive radiation damage beyond 10 dpa although some targets have failed due to structural damage. This paper will describe the operating experience with these targets and present some thermal and radiation calculations.  
RPPE027 High Intensity High Energy E-Beam Interacting with a Thin Solid State Target: First Results at AIRIX 1982
  • M. Caron, F. Cartier, D.C. Collignon, L.H. Hourdin, E. Merle, M. Mouillet, C. Noel, D.P. Paradis, O.P. Pierret
    CEA, Pontfaverger-Moronvilliers
  • O. Mouton, N. Pichoff
    CEA/DAM, Bruyères-le-Châtel
  Funding: CEA, Polygone d’Expérimentation de Morronvilliers, LEXA F-51 475 Pontfaverger (France).

AIRIX is a 2 kA, 20 MeV, 60 ns linear accelerator dedicated to X-ray flash radiography. During a regular running phase, the primary electron beam is accelerated to and focused on a high atomic number target in order to generate X-rays by brembtrahlung mainly. The huge energy density deposited into the material is such that temperature rises up to 15000°K and that clusters and particles are violently ejected from the surface. In that mechanism, the backward emission speed can reach 5 km.s-1 and the debris can gradually accumulate and subsequently contaminate some sensitive parts of the machine. In order to protect the whole accelerating line from the detrimental effect of back-ejected particles, we have investigated the technical feasibility of a thin foil implementation upstream the X-ray converter.

RPPE029 Rotating Aperture Deuterium Gas Cell Development for High Brightness Neutron Production 2074
  • B. Rusnak, M. Hall, S. Shen
    LLNL, Livermore, California
  Funding: This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

A project is underway at LLNL to design and build a system for fast neutron imaging. The approach being pursued will use a 7 MeV deuterium linac for producing high-energy neutrons via a D(d,n)3He reaction. To achieve a high-brightness neutron source, a windowless rotating aperture gas cell approach is being employed. Using a series of close-tolerance rotor and stator plates, a differential pumping assembly has been designed and built that contains up to 3 atmospheres of deuterium gas in a 40 mm long gas cell. Rarefaction of the gas due to beam-induced heating will be addressed by rapidly moving the gas across the beam channel in a crossflow tube. The design and fabrication process has been guided by extensive 3D modeling of the hydrodynamic gas flow and structural dynamics of the assembly. Summaries of the modeling results, the fabrication and assembly process for the rotating aperture system, and initial measurements of gas leakage shall be presented.

RPPE030 Corrugated Thin Diamond Foils for SNS H- Injection Stripping 2152
  • R.W. Shaw, V.A. Davis, R.N. Potter, L.L. Wilson
    ORNL, Oak Ridge, Tennessee
  • C.S. Feigerle, M.E. Peretich
    University of Tennessee, Knoxville, Tennessee
  • C.J. Liaw
    BNL, Upton, Long Island, New York
  Funding: MEP acknowledges a SURE fellowship, supported by Science Alliance, a UT Center of Excellence. RNP acknowledges an appointment to the U.S. DOE SULI Program at the Oak Ridge National Laboratory. SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a collaboration of six US National Laboratories: ANL, BNL, TJNAF, LANL, LBNL, and ORNL.

We have prepared and tested corrugated, thin diamond foils for use in stripping the SNS H- Linac beam. Diamond has shown promise for providing ca. 10X increased lifetime over traditional carbon foils. The preferred foil geometry is 10.5 by 20 mm at 350 microgram/cm2, mechanically supported on preferably one, but no more than two, edges. The foils are prepared by chemical vapor deposition (CVD) on a patterned silicon substrate, followed by chemical removal of the silicon. This yields a foil with trapezoidal corrugations to enhance mechanical strength and foil flatness. Both micro- and nano-crystalline diamond foils have been grown. Microwave plasma CVD methods that incorporate high argon gas content were used to produce the latter. Sixteen foils of a variety of characteristics have been tested using the BNL 750 keV RFQ H- beam to simulate the energy deposition in the SNS foil. Long foil lifetimes, up to more than 130 hours, have been demonstrated. Characterization of the foils after beam testing indicates creation of sp2 defects within the ion beam spot. Current efforts are centered on development of corrugation patterns that will enhance flatness of single-edge supported foils.

RPPE031 Target and Horn Cooling for the Very Long Baseline Neutrino Experiment 2209
  • S. Bellavia, S.A. Kahn, H.G. Kirk, H. Ludewig, D. Raparia, N. Simos
    BNL, Upton, Long Island, New York
  Funding: This work is performed under the auspices of the US DOE.

Thermodynamic studies have been performed for the beam target and focusing horn system to be used in a very long baseline neutrino oscillation experiment. A 2mm rms beam spot with power deposition of over 18 KW presents challenging material and engineering solutions to this project. Given that the amount of heat transferred by radiation alone from the target to the horn is quite small, the primary mechanism is heat removal by forced convection in the annular space between the target and the horn. The key elements are the operating temperature of the target, the temperature of the cooling fluid and the heat generation rate in the volume of the target that needs to be removed. These working parameters establish the mass flow rate and velocity of the coolant necessary to remove the generated heat. Several cooling options were explored using a carbon-carbon target and aluminum horn. Detailed analysis, trade studies and simulations were performed for cooling the horn and target with gaseous helium as well as water.

RPPE032 Measurement of the Secondary Emission Yield of a Thin Diamond Window in Transmission Mode 2251
  • X.Y. Chang, I. Ben-Zvi, A. Burrill, S. Hulbert, P.D.J. Johnson, J. Kewisch, T. Rao, Z. Segalov, J. Smedley, Y. Zhao
    BNL, Upton, Long Island, New York
  The secondary emission enhanced photoinjector (SEEP) is a promising new approach to the generation of high-current, high-brightness electron beams. A low current primary electron beam with energy of a few thousand electron-volts strikes a specially prepared diamond window which emits secondary electrons with a current two orders of magnitude higher. The secondary electrons are created at the back side of the diamond and drift through the window under the influence of a strong electrical field. A hydrogen termination at the exit surface of the window creates a negative electron affinity (NEA) which allows the electrons to leave the diamond. An experiment was performed to measure the secondary electron yield and other properties. The results are discussed in this paper.  
RPPE033 Engineering the SNS RTBT/Target Interface for Remote Handling 2278
  • M. Holding, C.M. Hammons, B.R. Lang, G.R. Murdoch, K.G. Potter, R.T. Roseberry
    ORNL, Oak Ridge, Tennessee
  The SNS facility is designed for a 1.4MW 1.0GeV proton beam and the interface region of this beam with the Hg spallation target will be highly activated. This installation is located about fifteen feet below the access floor and the activity levels in the RTBT/Target interface are sufficiently high to warrant the application of Remote Handling techniques. The installed components are manufactured from radiation hard materials with serviceability beyond the lifetime of the machine, and all connections and mechanisms have been simplified to allow remote handling. The application of pneumatics to facilitate the assembly of major components and to the operation of moveable diagnostics has produced some unique design solutions.  
RPPE034 Measurements of the Energy Deposition Profile for 238U Ions with Energy 500 and 950 MEV/U in Stainless Steel and Copper Targets 2318
  • E. Mustafin, I. Hofmann, D. Schardt, K. Weyrich
    GSI, Darmstadt
  • A. Fertman, A. Golubev, A. Kantsyrev, V. Luckjashin
    ITEP, Moscow
  • A. Gnutov, A. Kunin, Y. Panova, V. Vatulin
    VNIIEF, Sarov (Nizhnii Gorod)
  • L.N. Latysheva, N. Sobolevskiy
    RAS/INR, Moscow
  Funding: Supported by the grant of the GSI-INTAS #03-54-3588.

Sub-millimeter wall thickness is foreseen for the vacuum tubes in the magnets of the superconducting dipoles of the SIS100 and SIS300 of the FAIR Project. The Bragg peak of the energy deposition by the U ions in these walls may lie dangerously close to the superconducting cables. Thus the precise knowledge of the dE/dx profile is essential for estimating the heat load by the lost ions in the vicinity of the superconducting wires. Here we present the results of the measurement of the U ion beam energy deposition profile in Cu and stainless steel targets and compare the measured data with the Monte-Carlo simulation using the SHIELD code.