Operational%20Experience%20at%20FNAL

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Operational Experience at FNALsAntiproton
Source Target Station

• Patrick Hurh
• BENE Meeting
• November 3, 2004

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Aerial photograph of Pbar Source
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Pbar Target Vault
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Workers in target vault
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Lithium Lens
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Single-turn 3-degree pulsed magnet
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Gear drive target assembly
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Target stack showing cooling disk
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Pbar target assembly presently in use
Graphite Tantalum Graphite
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Preparing for more protons on target

• Beam Studies
• Quantify spot size vs. pbar yield relationship
  for spot sizes below s0.15 mm
• Look for evidence of yield reduction due to
  melting
• Attempt to create single pulse damage to copper
  disk
• Alternative target material
• Identify target materials that are superior to
  Nickel in longevity while minimizing the loss of
  normalized yield
• Examine damage to old targets
• Beam Sweeping
• Create sweeping system to reduce peak energy
  deposition in the target
• Consider deferring final installation and
  commissioning of beam sweeping until it is
  necessary operationally

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Target material comparison
Target Material Iridium Rhenium Tungsten Nickel Copper
A1/3/r (m3/Kg) .255 .271 .295 .437 .445
A1/3/r (Normalized) 1.71 1.61 1.48 1 .98
Observed Yield (Normalized) 1.05 1 .99
Melting Point Energy (J/g) 460 610 630 1,250 770
Yield Strength (MPa) 160 270 500 230 72
Gruneisen parameter (MPa Kg/J) 80.6 66.0 31.0 15.8 17.2
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Energy deposition vs. peak target temperature
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Apparent target depletion due to melting
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Damage to Tungsten-Rhenium target
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Damage to Tungsten target
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Early target assembly
5e11 ppp s.35 mm
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Holes in Copper Target
1e12 ppp s.35 mm
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Bulges on titanium target cover
3e12 ppp s.2 mm
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Target damage to nickel target (entry)
3e12 ppp s.2 mm
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Target damage to nickel target (exit)
3e12 ppp s.2 mm
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Damage to titanium cover and nickel target
5e12 ppp s.15 mm
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Target R2 T2 with graphite cover and Stainless
304 damage
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Pbar yield and peak energy deposition vs. spot
size
McLens and CASIM Models
Nickel target, 5E12 protons
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Comparison of model and data yield curves
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Summary of target material endurance study
Material Spot size Starting Yield Ending Yield Protons On target Yield reduction Scaled to 1018 protons
Nickel 200 ?xy 0.15, 0.16 1.000 0.970 5.7 x 1017 5.3
Nickel 200 ?xy 0.22, 0.16 0.990 0.935 6.6 x 1017 8.3
Inconel? 600 ?xy 0.15, 0.16 0.995 0.970 10.6 x 1017 2.4
Inconel? 600 ?xy 0.22, 0.16 0.990 0.960 10.7 x 1017 2.8
Inconel? 625 ?xy 0.22, 0.16 0.980 0.970 6.6 x 1017 1.5
Inconel? X-750 ?xy 0.15, 0.16 0.985 0.965 5.7 x 1017 3.5
Inconel? 686 ?xy 0.15, 0.16 0.970 0.935 1.0 x 1017 38.2
Stainless 304 ?xy 0.15, 0.16 1.000 0.965 6.1 x 1017 5.8
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Upstream sweeping magnets installed in AP-1 line
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Present beam parameters for pbar target

• Proton beam energy is 120 GeV, pulse length 1.6
  µs
• Beam spot size is s 0.15 mm
• Duty cycle varies from 0.5 to 0.2 Hz
• Beam intensity continues to increase
• Average proton intensity on target 6.5E12, peak
  7.1E12
• Both Inconel 600 and Stainless 304 targets used
  at this intensity
• Estimated average energy deposition in Inconel
  600 1,600 J/g (189 J/cc)
• Target disk lifetime is about 2 months under
  these conditions
• Target assembly is made up of 6 target disks

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Tantalum target test summary (1)

• Goal was to create enough target damage to reduce
  pbar/p- yield
• Started with a proton intensity of 1.0E11 and a
  spot size of s 0.50 mm. Maximum energy
  deposition was attained with a proton intensity
  of 6.5E12 and a spot size of s 0.15 mm
• Target rotation was stopped so that beam pulses
  were accumulated in the same area
• After accumulating 100 beam pulses, energy
  deposition was increased by a factor of 2 and
  process repeated
• Target rotated 10 between data points

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Tantalum target test summary (2)

• Goal was to create enough target damage to reduce
  pbar/p- yield
• Target did not show appreciable pbar/p- yield
  reduction up to maximum energy deposition
• 1,100 pulses with proton intensities of
  5.8-6.5E12
• Energy deposition estimated at 2,300 J/g (38,300
  J/cc)
• Tantalum target had 8 lower pbar/ p- yield as
  compared with nickel (model predicted a few
  percent higher)

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Pbar target and beam sweeping, Summary

• Pbar Target and Beam Sweeping
• Inconel 600 identified as operational target
  material
• Although Stainless 304 is a close second
• There appears to be no benefit in reducing spot
  sizes to the original goal of s 0.10 mm
• Beam studies show spot sizes below s 0.15 mm
  produce little or no increase in antiproton yield
  (contrary to predictions from models)
• Target damage and yield reduction are not as
  severe as expected at small spot sizes

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Pbar target and beam sweeping, Summary

• Pbar Target and Beam Sweeping
• Single pulse target damage observed with copper
• Energy deposition a factor of 2.5 above that
  required for the onset of melting
• Yield reduction from target melting has not been
  observed
• Upstream beam sweeping system has been tested
  with beam (downstream system nearly ready for
  installation)