LowEnergy Linac Upgrade Scenarios

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Low-Energy Linac Upgrade Scenarios

• Elliott McCrory
• BD/Proton/Linac
• 21 November 2003

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Why Another Linac Upgrade?

• The supply of 7835 power amplifiers may end soon
• Ingrid Bergman as Mike Witherell "You're saying
  this only to make me spend money."
• Humphrey Bogart as Elliott "I'm saying it
  because it's true. Inside of us, we both know
  Burle will go out of business someday. If that
  happens and you're not prepared, you'll
  regret it - maybe not today, maybe not tomorrow,
  but soon, and for the rest of your life."
• Modulator switch tubes are no longer available
• We have a 5-10 year supply of these tube
• Activation in the Linac may become a problem
• Matching between 201 MHz and 805 MHz portions is
  not ideal
• particles/day is 6X higher in FY03 than FY00
• And MiniBooNE and NUMI want 4X more than this
• Many 33-year-old components are difficult
  expensive to maintain
• LEL Quad Power supplies (1M to replace, ASAP)
• LEL LLRF, driver amplifiers, etc., etc.
• Technical staff that built LEL are nearing
  retirement

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Linac Upgrade Possibilities

• Replace the Cockcroft-Walton prototype tank 1
  with a 201 MHz RFQ to 10 MeV
• But only solves the activation issue
• Replace the 201 MHz portion of the Linac with a
  402 MHz Linac
• Solves all issues
• Similar to SNS
• Several possible scenarios
• Add more accelerating modules at the end
• Solves no issues, but would help Booster
• Conventional SCC modules, like existing Module 7,
  or
• Superconducting modules, similar (identical?) to
  8 GeV Linac injector

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New 402 MHz Low-Energy Linac

• Original Don Young, PD Study 1 (2002)
• Commercial partner
• AccSys Technologies, Pleasanton, CA
• 80 owned by Hitachi
• Potential collaborations with
• New Proton Driver efforts
• Foster and/or Chou
• Fermilabs NTF (Arlene Lennox)
• Fermi Institute of Hadron Therapy
• 50M from Hastert?!
• National Taiwan University Hospital, Hsinchu
  Biomedical Science Park
• Taipei, Taiwan
• Has 100M ready to spend NOW

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From AccSys Web page

• Synchrotron Injector Linac Systems
• The LINSTAR series of proton linac systems are
  designed to provide moderate-energy proton beams
  (typically from 2 to 7 MeV) for  injection into
  high energy proton synchrotrons that are used for
  proton beam cancer therapy or physics research.
  These fully integrated systems typically consist
  of a carefully designed and selected combination
  of a radiofrequency quadrupole (RFQ) linac, a
  drift tube linac (DTL) for injection energies of
  gt3 MeV, AccSys' standard rf power system, a high
  energy beam transport system tailored to the
  specific requirements of the facility and an
  optional debuncher cavity. They can accelerate
  either H or H- ion beams and are also available
  for polarized H or H- beams. Standard LINSTAR
  units can provide pulsed beam currents up to 25
  mA at pulse widths from 3 to 300 µsec. Operation
  at pulse repetition rates from 0.1 to 30 pulses
  per second have been demonstrated, including
  on-demand pulsing for breath-mode synchronization
  in proton cancer therapy.
• LINSTAR systems are currently in use at several
  facilities around the world 
• A Model PL-2i has been operating at Loma Linda
  University Medical Center since 1990 as the
  injector to the high energy proton synchrotron
  cancer treatment facility. The synchrotron system
  operates 24 hours a day, 6 days a week and has
  been described in a number of technical
  publications. Complete proton therapy systems
  based on the Loma Linda installation are
  commercially available from Optivus Technology,
  Inc.  Two systems are being commissioned
  in Japan a Model PL-3i is the injector to the
  proton synchrotron cancer treatment facility at
  the Shizouka Cancer Center, being built by
  Mitsubishi Electric Company, and a Model PL-7i is
  the injector for the proton synchrotron cancer
  treatment facility being installed at the Tsukuba
  Medical Center by Hitachi, Ltd.  A Model
  PL-7i has been operating at the Indiana
  University Cyclotron Facility since 1997 as the
  injector for the CIS compact synchrotron which is
  in turn the injector for the high energy physics
  cooler ring. 

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Two Scenarios Commonalities

• Replace Cockroft-Walton with two redundant RFQs
• Available from AccSys technologies
• 3 MeV
• New LEBT
• including the Double Alpha idea invented by Del
  Larson
• No need for a buncher cavity.
• New DTL from 3 to 70 or 89 MeV
• Tank 1 Ramped Gradient Drift Tube Linac
• RGDTL available from AccSys technologies
• Three or four new 402 MHz DTLs
• New Transition section
• We can do it right this time
• One or two new SCC modules to 116 MeV
• Extra room at 400 MeV to add more acceleration

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Basic Parameters of Today
SCC Side Coupled Cavity LEL Low
Energy Linac
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Three Scenarios

• Modest
• 2 RFQ, RGDTL, 4 DTL, 2 LE SCC
• Luxury
• 2 RFQ, RGDTL, 5 DTL, 1 LE SCC, 2 new modules at
  400 MeV
• Shift existing SCC modules upstream by 18 m
• More aggressive ideas (not explored here)
• 800 MeV??
• Move everything upstream into C-W pit ( 100m?)
• Add Superconducting accelerating cavities at end

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Schematic Layout of 2
Solid NEW
Hatched Existing
RGDTL
DTL Tank 2
DTL Tank 5
DTL Tank 3
DTL Tank 4
RFQ 2
RFQ 1
89 MeV

Trans0
TransV
New Module 1
Existing Module 1
To Booster at 480 MeV
Existing Module 7
New Module 8
New Module 9
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Benefits of a new LE Linac

• Replaces all 33-year-old Linac equipment
• SOA technology
• NO MORE 7835s!
• Increase beam brightness
• Probably 2 to 4 X smaller transverse emittance
• Existing technical staff Days are numbered
• New technical staff can own this new machine
• New machinery and new people might last another
  30 years
• 402 MHz Klystrons exist
• And our 805 MHz klystrons last forever
• Significantly shorter than existing LEL
• Could add more modules at the end to give an
  energy boost
• Higher injection energy into Booster is better
• Reduced losses/activation throughout the Linac
• Transition section is our predominant loss now
• Lower emittance would mean lower 400 MeV-line
  losses

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Higher Energy Linac Benefits

• The space charge limit for constant aperture at
  Booster injection scales like ß2?3

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Pet Project (1996)
RFQs
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Double a Magnet Del Larson
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MEBT Parameters
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Trace-3D Run of PET MEBT
Longitudinal
RFQ 1
RFQ 2
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From Larsons 96 MEBT paper

• 6.1. Longitudinal Control.
• some control over the longitudinal phase
  space can be exercised by using the trim quads
  located in the cross over arm. The MEBT has been
  designed to have a high dispersion in this
  region, and quadrupole variations in this region
  therefore have a large effect on the dispersion
  function. The dispersion is introduced in the
  first alpha magnet, and the magnet and optics
  have been nominally designed so that the
  dispersion function has zero gradient in the
  middle of the cross over arm. With zero
  dispersion gradient and transverse waists in the
  center of the cross over arm, the beam will have
  symmetric optics about this point, leading to
  zero dispersion and zero dispersion gradient at
  the end of the second alpha magnet. While the
  first goal of the trim quads is to ensure a
  symmetric dispersion function, so as to eliminate
  dispersion at the end of the MEBT, a second
  function can be to control the position of the
  longitudinal waist. Since small trim quad
  variations have a large effect on the dispersion
  and a small effect on the transverse beam optics,
  the longitudinal control exercised by the trim
  quads is largely independent of the transverse
  optics.
• 6.2. Transverse Control.
• Once dispersion has been minimized (by arranging
  for symmetric optics within and between the
  dipoles) the quadrupoles placed downstream of the
  dipoles will have no effect on the longitudinal
  optics and can therefore be used solely for
  transverse optics matching. Since there are three
  such quads, one can in principle exercise control
  over three linear combinations of the four
  independent transverse phase space variables.

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Linac Upgrade Params (1)
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Linac Upgrade Params (2)
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Rough Cost Estimate
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Final Thoughts

• Collaborators galore!
• NTF/Lennox
• Taiwan
• AccSys (but not for free)
• How much longer can we get 7835 power amplifiers?
• How much longer can we maintain the old Linac?
• The time is right to proceed on this