# Presentation: 079951

## Pbar Target StationTarget and Beam SweepingHigh Gradient Lithium Lens

- Jim Morgan
- DOE Review
- July 22, 2003

## Pbar Target Vault

## Goals for Target Station upgrades

- Alternative target material
- Identify target materials that are superior to Nickel in longevity while minimizing the loss of normalized yield
- Undertake beam studies to confirm pbar yield improvements at small spot sizes predicted by model
- Beam Sweeping
- Build and commission sweeping system to reduce peak energy deposition in the target
- High Gradient Lithium Lens
- Disassemble and analyze lenses that have failed
- Create and refine a Finite Elements Analysis (FEA) model of Lens to better understand mechanical stresses
- Improve quality control in Lens production
- Develop a Lithium Lens that can operate at 1,000 T/m for 10,000,000 pulses

## Pbar yield and peak energy deposition vs. spot size

- Nickel target, 5E12 protons

- McLens and CASIM Models

## Comparison of model and data yield curves

## 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%
 |

## Pbar target assembly presently in use

## Upstream sweeping magnets installed in AP-1 line

## Pbar target and beam sweeping, Summary

- Pbar Target and Beam Sweeping
- Inconel® 600 identified as operational target material
- There may not be a benefit in reducing spot sizes to the original goal of σ = 0.10 mm
- Beam studies show spot sizes below σ = 0.15 mm produce little or no antiproton yield as much as models predict
- Target damage and yield reduction are not as severe as expected at small spot sizes
- Yield reduction from target melting has not been observed, although predicted by models
- Upstream beam sweeping magnets are installed in tunnel and power supply is nearly ready for  testing with beam
- Target station is ready for intensity increase from slip-stacking
- Spot size may need to be increased if slip-stacking is implemented prior to beam sweeping commissioning

## Lithium Lens gradient vs. Pbar yield

- MARS Model

## Observed Lens Lifetime

| Gradient
(T/m) | Average Number of
Pulses to Failure |
| --- | --- |
| 1,000 | <500,000 |
| 900 | 1,000,000 |
| 800 | 3,000,000 |
| 745 | 9,000,000 |
| 700 | >10,000,000 |

## Lithium Lens lifetime

## Lens autopsy results

- Progress of Lens disassembly and analysis
- Lenses 20, 21, and 26 have been finished
- Lenses 16, 17 and 18 are disassembled, awaiting analysis
- Lens 16 had a high pulse count, but no septum breach
- Lens 22 is being disassembled
- Example of high pulse count “pristine” failure
- General Results of Analysis
- Axial intergranular fracture followed by ductile fracture
- Intergranular nature of crack more consistent with corrosion
- Length of remaining tube wall prior to ductile fracture consistent with lower loads from ANSYS
- Circumferential channels burned through some septum
- Suggests internal arcing, possibly from Li/Ti separation
- Small cracks may be obliterated after arcing begins
- Multiple micro-cracks and pits found on the inside surfaces of septa

## Lens 21 septum after Lithium removal

## Lens #21, outside of inner septum

## Operational Lithium Lens

## Prototype Lens Summary

- Single piece Titanium septum and body
- Diffusion bonding
- Eliminates complicated seal between septum and body
- Only one joint in high stress region
- All joints bonded simultaneously
- Easier to maintain joint quality
- No residual stress
- Simplified construction and assembly
- Several lenses can be bonded at the same time
- Significantly fewer etching, welding and machining steps
- Lens septum construction costs may be reduced by a factor of two
- Additional water cooling to lens body
- Made possible by diffusion bonding process

## High gradient prototype Lithium Lens

## FEA and testing Summary

- FEA
- Viscoplastic and creep properties of lithium incorporated into full analysis
- Electromagnetic and thermal models complete up to 400 consecutive pulses
- Structural model being refined to optimize run times
- Material Testing
- Viscoplastic tensile lithium testing complete
- Lithium creep parameters quantified from pressurized tube testing
- Planning compression testing of Lithium
- Fatigue testing of diffusion bonded Ti 6-4 tube joints complete (joints as strong as parent material)
- Ti 10-2-3 diffusion bonding tests successful
- Ti 10-2-3 fatigue testing underway (coated and uncoated)

## Crack propagation on Lens septum

## Cross section of failed septa in Lenses #20 and #21

## Quality control Summary

- Lens Fill
- Improved data acquisition
- Changed strain gages to improve accuracy
- Pressure transducer upgrade
- Created dummy lens to calibrate instrumentation
- R&D of Lens seals and Lithium properties
- Lens Preparation
- Improved electron beam welding techniques
- Lithium handling procedures changed to minimize contamination
- Created new septum cleaning procedures to reduce the possibility of Hydrogen embrittlement/stress corrosion cracking

## Lithium Lens upgrade, Summary

- Lens Autopsy
- Lenses 20, 21, 26 have been disassembled and analyzed
- Lenses 16, 17 and 18 are disassembled and await analysis
- Lens 22 is being disassembled
- ANSYS Modeling
- Preliminary analysis complete on current and prototype I lens designs, full analysis in progress
- Full analysis of prototype II lens awaiting benchmarking of full analysis of current lens
- Quality Control
- Lenses 27 and 28 have been assembled and filled with new techniques
- Titanium embrittlement being investigated
- Prototype Lens
- First prototype is being prepared for fill, testing to follow
- Second prototype is in the design phase (awaiting completion of ANSYS tools and material tests)