IPNS Third RF Cavity Status Report

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IPNS Third RF Cavity Status Report
G.E. McMichael Accelerator Facilities Manager
Presentation at the Ninth SHRF/LOIA
Collaboration Meeting June 14, 2004
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IPNS ACCELERATOR OVERVIEW

• Accelerator delivers a short (70 ns) intense
• (3 x 1012 protons/pulse) pulse of 450 MeV
  protons to the depleted-uranium target 30 times
  per second
• Each proton produces about 15 neutrons
• IPNS is a user facility. Sole purpose of the
  accelerator is to produce neutrons (99 for the
  neutron-scattering instruments in Bldg. 375,
  remainder for an exotic-beam source for ATLAS)

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IPNS ACCELERATOR FACILITY

• Three accelerators in series
• 750 keV Preaccelerator
• 50 MeV Linac
• 450 MeV Rapid Cycling Synchrotron (RCS)
• Ancillary Systems
• RF (Variable Frequency Beam Feedback controlled)
• Magnets and power supplies (Pulsed DC)
• Control, diagnostics and data acquisition
• Vacuum
• Safety (Personnel Equipment)
• Buildings and Utilities
• AC Power
• Water Systems
• Air Conditioning

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HISTORY

• Preaccelerator and linac entered service in 1961
  as injector to the 12.5 GeV ZGS (Zero Gradient
  Synchrotron) high-energy physics accelerator
• RCS developed in mid 1970's as a proposed booster
  for ZGS. Excess beam would have been available
  for a spallation neutron source
• ZGS was shut down in 1979. RCS initially
  (1977-1980) provided beam into the ZING
  experimental target. First beam to IPNS target
  was in 1981
• Eight-billionth pulse 16 April, 2004

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ION SOURCE PREACCELERATOR

• Magnetron-type H- ion source, cesium getter
• Extraction at 20 keV, magnet to separate
  electrons
• Cockcroft-Walton generator, 750 Kv
• Output H- beam, 30 mA peak, 70 µs pulses, 30 Hz

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LINAC

• Alvarez-type drift-tube linac
• Copper-clad steel tank, 33.5 m long, 0.93 m
  diameter
• 124 drift tubes, each with a dc quadrupole magnet
• 200 MHz rf transmitter, triode amplifier tube,
  3.5 MW
• Output H- beam 50 MeV, 10 mA peak, 70 µs pulses,
  30 Hz

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50 MEV TRANSPORTATION LINE

• 8 Dipole horizontal bending magnets
• 6 Dipole vertical steering magnets
• 16 Quadrupole focusing magnets
• 12 Wire scanners, 6 Beam position monitors
• Transports H- beam 40 m from linac to RCS

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RAPID CYCLING SYNCHROTRON RCS

• 43 m circumference strong-focusing,
  combined-function synchrotron
• 6-sector machine, magnet structure D00FDF0
• Betatron tune correction provided by two pairs of
  sextupole magnets
• Multi-turn injection (? 130 turns, 3 mile
  string)
• Single-turn extraction by two ferrite-loaded
  kicker magnets and two septum magnets

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RAPID CYCLING SYNCHROTRON RCS

• Ring magnets are part of a biased 30 Hz resonant
  circuit. Generate a magnetic field that varies
  from 0.28 to 1 Tesla during the accelerating
  cycle
• Thin carbon foil strips off the two electrons
• Two rf cavities to bunch and accelerate the
  proton beam
• Third rf cavity will be installed in L6 section
• Output proton beam 450 MeV, 70-80 ns pulse, 30
  Hz, 3 x 1012 protons/pulse

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PTS BEAMLINE

• 4 Dipole horizontal bending magnets
• 2 Dipole vertical steering magnets
• 15 Quadrupole focusing magnets
• 6 Segmented secondary emission monitors, 1
  Segmented wire ion chamber
• Transports H- beam 45 m from RCS to
  neutron-generating target

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ACCELERATOR OPERATIONS

• OPERATING PERIODS
• Typically two to four weeks on and one to two
  weeks off
• Six-hours reserved each Tuesday for machine
  research and moderator regeneration
• Two longer shutdowns (Christmas and summer) for
  installations and larger maintenance jobs

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THIRD RF STATION

• Cavity almost identical to two existing
• Redesigned rf amplifier systems
• Pre-driven and final use new tubes
• Driver is an updated version of existing systems
• New low-level system
• Provide second-harmonic rf for capture and
  initial acceleration
• Provide additional fundamental at mid-cycle
• Can function as on-line spare for existing
  fundamental systems
• Installation to start in 6 months

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2nd HARMONIC RF

• Propose to enhance 3rd rf system to operate at
  2nd harmonic throughout the acceleration cycle
• Principal addition will be a new cavity with
  different ferrite
• Funding and schedule uncertain

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SUMMARY

• IPNS continues to have a moving 10-year window
  to ensure reliable operation for the next 10
  years
• Recent budget problems have slowed the
  upgrade/assurance program.
• Our interest in the collaboration remains strong
  - Shaoheng Wang will be joining our program