1. Mike Jenkins Lancaster University and The Cockcroft Institute

2. Presentation Overview Positron source requirements of future colliders Undulator based positron source design Current undulator developments Update on Target material measurements 06/04/2011IOP NPPD Glasgow2

3. Requirements of a Positron Source There are currently three proposed designs for particle accelerators which require a positron production rate of >10 14 e + /s Conventional solutions to produce positrons have a production limit of 6 x 10 12 e + /s ColliderPositron Production Rate (number of e + /s) ILC3.9 x 10 14 CLiC1.1 x 10 14 LHeC3.1 x 10 15

4. Future Positron Source Designs Current proposed designs for the positron source at future colliders include: laser-Compton based source Undulator based Hybrid Target (crystalline target and amorphous target) 06/04/2011IOP NPPD Glasgow4

5. Undulator Based Positron Source Schematic of ILC RDR Positron Source 06/04/2011IOP NPPD Glasgow5 Length of Undulator Number of γ / e - Heat Load on Target Number of e + /e - ~150m to 250m200~20 kW (beam) Up to 20 kW (eddy currents) 2

6. Undulator Developments Currently the superconducting undulator planned for use in the positron source is made using NbTi conductors NbTi undulator prototype for ILC is currently being tested at RAL Simulations into different superconductors are on going, the work presented here is based on Nb 3 Sn conductors ParameterDesign Value Test Results Period11.5 mm11.6 mm Field on Axis0.86 T0.88 T

7. Undulator Developments OPERA 3D Simulation of Undulator Flux Density: 0.070 T to 4.85 T

8. Undulator Developments 06/04/2011IOP NPPD Glasgow8

9. Positron Source Target Courtesy of Ken Davies, Daresbury Lab Courtesy of Jim Rochford, RAL 0.5 to 1.5 T Dipole Magnet 1 m Titanium Target

10. Eddy Current Results Peak Torque (Carmen) Average Torque (Carmen) Min Torque (Carmen) Courtesy of Ian Bailey, Lancaster Preliminary Data Results for peak field of 0.5 T and target immersion depth of 30.25 mm 06/04/2011IOP NPPD Glasgow10

11. Target Material Conductivity To resolve the difference between simulations and the data the properties of the titanium are being investigated. Currently the electrical and thermal conductivity of the titanium is being measured Expected Resistance8.8 x 10 -5 Ω Expected Electrical Conductivity 5.62 x 10 5 S m -1 Expected Thermal Conductivity 6.70 W K -1 m -1

12. Target Material Conductivity Samples Probe 2 Probe 1 SampleLength (mm)Width (mm)Height (mm) A49.9616.464.94 B49.9716.459.96 C49.8216.3714.92 06/04/2011IOP NPPD Glasgow12

13. Target Material Conductivity Oxygen Free Copper Contacts Springs Sample 06/04/2011IOP NPPD Glasgow13

14. Target Material Conductivity Experimental setup consists of a AC current source and nanovoltmeter connected to LabView Only preliminary DC measurements taken so far Trying to understand systematic effects causing shifts in the signal between consecutive data taking periods

15. Summary Undulator simulations are promising, it appears that the new wire could allow the undulator period to reduce from 11.5 mm to 10.0 mm keeping K constant Awaiting confirmation about the performance of the Nb 3 Sn wire, current uncertainty about the performance of the wire at low field strength Conductivity measurements of the target material are preliminary and there are a few issues still to resolve 06/04/2011IOP NPPD Glasgow15

16. Thank you for listening, are there any questions