Pbar Source Options at Fermilab

1
Pbar Source Options at Fermilab

• Keith Gollwitzer
• Antiproton Source Department
• Accelerator Division
• Fermilab

2
Outline

• Quick History
• Current Pbar Operations
• E760/E835
• Accelerator Operations
• Technique
• Apparatus
• Future Pbar Ring Plans
• Charmonium Experiment?
• Improvements
• Accelerator Work
• Interest Proposal ??

3
Quick History

• The Fermilab Antiproton Source was built for the
  Tevatron proton-antiproton collider program in
  the 1980s
• Key to Tevatron total integrated luminosity
• While Fermilab ran fixed target programs, the
  Antiproton Source would have sat idle except for
  the Charmonium program (E760/E835) which ran in
  1990-1, 1996-7 2000
• Circulating antiprotons with internal Hydrogen
  gas jet target
• Study of pbar-p annihilations into cbar-c states

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Stacking 120GeV Protons

• Slip Stacking in Main Injector
• Extracted out of MI into 700m Beam line
• Hit Nickel alloy
  target
• gt2s cycle

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Stacking 8GeV Secondaries

• Secondaries from target are
  focused using the
  Lithium Lens
• Pulsed Magnet bends 8GeV
  negatives into AP2
• AP2 transports secondaries to
  Debuncher
• Designed admittance gt35? mm-mrad
• Accepted beam emittance
  gt330? mm-mrad
• Left bend momentum selects 5
• 1 of the secondaries are antiprotons at the end
  of the 290m line

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Stacking Debuncher

• Designed admittance is 35? mm-mrad
• Bunch Rotation in 50 turns reduces the momentum
  spread
• Stochastic Cooling
• 4-8 GHz
• Liquid He cooled slotted waveguide pickups
• Factor of 10 in longitudinal phase space
• Factor of 7-10 in both transverse phase space
  dimensions

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Stacking Accumulator

• Beam is transferred from Debuncher via a short
  beam line
• RF system decelerates from injection to
  deposition orbit
• Stochastic Cooling
• 2-4 GHz stacktail, 2-4 4-8 GHz core momentum
• 4-8 GHz transverse slotted waveguide pickups

-Preserve Longitudinal phase space -Increase
particle density by factor of 5000 -Factor of 3-5
in both transverse phase space dimensions
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Recycler Ring

• After 4-5hrs of stacking, 60-70e10 pbars are
  transferred to Recycler Ring via 1km beam line
  and Main Injector
• In Recycler (permanent magnets), stochastic
  cooling keeps the transverse phase space while
  electron cooling allows for a further increase in
  particle density by a factor of 5
• Holds 3 times more pbars than Accumulator
• Allows Accumulator to concentrate on stacking and
  not large stacks
• Eventually sent to Tevatron, via Main Injector,
  for collider program

9
Recycler Electron Cooling

• Longitudinal stochastic cooling of 8 GeV
  antiprotons in the Recycler has been replaced by
  Electron Cooling
• Electron beam 4.34 MeV 0.5 Amps DC 200mrad
  angular spread
• Max beam current 730 mA Circulated in cooling
  section
• In U-Bend mode currents of 1500 mA has been
  obtained.

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Operation During E760/E835

• Stack up to 60-100e10 antiprotons
• Up to 4e10 pbars/hr
• Stacking time 1 days
• 1-2 hr to decelerate and prepare beam
• Run experiment 2-4 days
• Luminosity 5e31 cm-2s-1
• Capable of gt 1e32 cm-2s-1-- detector not capable
• 1 hr to re-establish stacking
• No Recycler Ring

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E760/E835 Technique

• Antiproton-proton annihilation via 2 or 3 gluons
  to form a specific cbarc state
• Accumulator is the spectrometer
• Change beam energy
• Ecm lt 4.3GeV
• Detector is for counting final states from
  Charmonium decay
• Detector stability and understanding the
  efficiency as a function of stack/time
• See G. Stancari Presentation

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E760/E835 Detector

• Emphasized ability to separate electromagnetic
  states from large hadronic background
• Identify ee- from J/? and ? decays or
• cbarc ? ?? or all photon final states ?0?0 ?0?
  ??
• Good ability to identify high energy ?0
• Non-magnetic
• Trigger/DAQ had to handle dc interactions
• No bunch structure of the beam

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Antiproton Rings after 2009

• Originally was to supply beam for BTeV
• Since BTevs cancellation
• Ideas have been discussed informally
• Some have been presented to Fermilab management
• In one case, manpower has been assigned and more
  formal plans are being made
• Work has started!!

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Antiproton Rings after 2009

• Recycler Ring
• Convert to proton accumulator while the Main
  Injector ramps and extracts
• Main Injector fill time reduces from 0.75s to
  12µs
• More protons per year for neutrino program
• A team is turning this into a project

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Antiproton Rings after 2009

• Several ideas for the Debuncher Accumulator
  have been tossed about
• Proton stacker to possibly increase protons by
  25 for neutrino program
• Separate proton experiment area
• MECO like experiment
• Antiproton experiments
• Charmonium
• Low energy/stopping experiments
• NO Manpower has been assigned !!!!

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More Charmonium?

• Improvements since E760/E835 ran
• Detector advances
• Calorimetery
• Tracking
• Digitization at detector
• Computation power trigger/DAQ
• Accelerator advances
• Can stack at 20e10 pbars/hr
• Plans for gt 30e10 pbars/hr

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Stacking Performance
Best stacking for 1 hour for each day Average
Stacking rate for a week
1mA is 1e10 pbars circulating in Accumulator
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Near Term Accelerator Work

• Slip Stacking (7)
• At 7.5x1012 protons on target on average
• Design average 8.0x1012
• Lithium Lens (0 15)
• Lens Gradient from 760T/m to 1000 T/m
• AP2 Line (5-30)
• Lens Steering
• AP2 Steer to apertures
• AP2 Lattice
• Debuncher Aperture (13)
• Currently 30-32? mm-mrad
• Design to 35? mm-mrad

• Debuncher Bunch Rotation Voltage (5)
• Were running on old tubes at 4.0 MeV for RF
  cavities
• Need to be at 5.3 MeV
• Accumulator and D/A Aperture (20)
• Currently at 2.4 sec
• Design to 2.0 sec
• Stacktail Efficiency
• Can improve core 4-8 GHz bandwidth by a factor of
  2
• Timeline Effects
• SY120 eats 7 of the timeline

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Accelerator Work for an Antiproton Program

• Re-establish deceleration capability
• Controls upgrade for Tevatron Run II
• Design and develop deceleration ramps to reach
  the necessary beam momentum for whatever
  experiment
• Determine/implement scheme to longitudinally cool
  on the Accumulator central orbit while an
  experiment runs

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Interest Proposal

• Is there Physics Interest?
• Must besince there is FAIR/PANDA proposal
• Is there interest to do a Charmonium experiment
  at the existing Fermilab Antiproton Source?
• 10 people Wednesday during dinner discussed
  possibilities
• Propose Charmonium program
• Many topics for pbarp annihilation see R. Mussa
  presentation
• Design Apparatus
• Non-magnetic detector (another E760/E835) OR
• Magnetic tracking detector
• Build experiment for data taking starting in 2011

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Summary Existing Pbar Source
22
Summary
Experiment?