Status and Plans of UK Undulator Prototyping R&D

1. Status and Plans of UK Undulator Prototyping R&D Yury Ivanyushenkov for HeLiCal Collaboration ILC Positron source meeting 27th - 29th September 2006 RAL

2. HeLiCal Collaboration CCLRC Technology Rutherford Appleton Laboratory: D.E. Baynham, T.W. Bradshaw, A.J. Brummitt, F.S. Carr, Y. Ivanyushenkov, A.J. Lintern,J.H. Rochford CCLRC ASTeC Daresbury Laboratory and Cockcroft Institute: A. Birch, J.A. Clarke, O.B. Malyshev, D.J. Scott University of Liverpool and Cockcroft Institute: I.R. Bailey, P. Cooke, J.B. Dainton, L.J. Jenner, L.I. Malysheva University of Durham, CERN and Cockcroft Institute : G.A. Moortgat-Pick DESY: D.P. Barber, P. Schmid

3. Scope • ILC Undulator specification • Working technical specification • Undulator prototyping R&D programme • Full scale undulator module • Plans

4. ILC Undulator specification Electron energy: 150 GeV Undulator period: 10 mm Field on axis: Kx=Ky = 1 or 10 MeV photon in first harmonic ?

5. Working specification • Undulator period: as close as possible to 10 mm • Field on axis: to produce 10 MeV photons (first harmonic) • Field homogeneity: ≤1% • Vacuum bore: to have beam stay clear of 4 mm => about 5 mm for vacuum bore and about 6 mm for magnetic bore • Superconductor (NbTi) working point : about 80% of short sample critical current. • Module length: 4 m

6. Undulator prototyping R&D goal • Develop reliable magnetic modelling technique • Develop undulator manufacturing technique • Manufacture and test first full scale undulator module

7. Magnetic modelling with Opera 2d and 3d • Winding aspect ratio: the highest field on axis is achieved with a rectangular winding with the smallest radial height – to- length ratio (flat conductor). However, taking into consideration the peak field in the conductor, a square shape was found to be optimal. • Winding current: to produce 0.8 T-field on axis a 1000 A/mm2 current density is required (winding - 4mm * 4 mm ; winding internal diameter - 6 mm; period - 14 mm); • (Note: What is the optimal current distribution in the conductor ?) • Field on axis: can be enhanced by the former poles made of magnetic material. The inclusion of magnetic material outside the winding also increases the field on axis. • Peak field: is about twice the field on the axis • for the above configuration, even higher for undulator with iron poles and iron yoke. • (Room for improvement: Nb3Sn ?) • Tolerance effects on central field value: winding radius variation of 0.1 mm leads to 4.2 % change in the on axis field value, the changes induced by changing the winding period by 0.1 mm are at the level of 3%. Region with the highest peak field

8. Magnetic modelling predictions Conclusion so far: Period of 10 mm means very small bore -unpractical! Realistic figures: Beam stay clear – 4 mm Vacuum bore - 5 mm Winding bore - 6 mm Period - 11.5 mm

9. Prototypes matrix

10. Prototypes family Please join us for Undulator R&D Facility Tour on Friday to learn more on manufacture technique

11. Prototype I results Very successful prototype: Never quenched; Reaches the design field; Quite good field profile

12. Prototype II results Field on axis varies by -2% for 100 μm increase in winding bore → +/- 1% variation in the field translates into +/- 50 μm precision in winding borefor pitch 14 mm

13. Prototype III results Period 12 mm Winding bore 6.35 mm 7-Wire Ribbon 8 Layers Wire Cu:Sc = 1.35:1 Measured field = 0.533 T (+/- 0.4% St.Dev., +/- 0.8% max)

14. Prototype IV results Measured field: 0.91 T +/- 1.6% St.Dev Former: Iron Pitch: 12 mm Winding bore: 6.35 mm Bore: 4.5 mm Winding: 7 wires x 8 layers

15. Prototypes III and IV: effect of iron Samples 1-3: 080A16 Bright steel (BS970) Sample 4: unknown mild steel Undulator geometry: Period: 12 mm Winding bore: 6.35 mm Winding: 8 layers of 7-wire ribbon Wire current: 200A

16. Technology status • Former manufacturing - developed techniques for machining formers in aluminium and iron               - accurate gun drilling of bore               - machining of iron spring configuration        - assembly procedure which can be extended to 2m coil module fabrication • Coil winding technology                 - winding based on ribbon technique - winding machine                 - coil terminations                 - coil impregnation with epoxy • Magnet testing and field measurements                 - field measurements - Hall probe movement and positioning at 4K                 - LabVIEW logging software

17. Short prototypes summary

18. Undulator 4m module The main features of the undulator module are: • The module will be made up of a magnet ( two sections), helium bath, thermal shield and a cryostat. • The former which is 11.5mm pitch with a 6.35 DIA winding bore. • The former will give 1747mm of magnet length. • The overall length of the cryostat is 4m. • The turret for the services will be in the centre of the cryostat. • Cold mass is cooled by a cryocooler mounted in the tarret. • Thermal shield is pre-cooled by liquid nitrogen to reduce overall cooling time

19. Undulator 4m module: Layout He bath vessel Thermal shield Two sections of the undulator magnet

20. Undulator 4m module: Cold mass Undulator magnet assembly

21. Undulator 4m module: More details Cryostat wall – Thermal shield - He vessel - Magnet connection Turret region

22. Plans • Complete the Helical Undulator R & D Programme by November 2006 • Design, Manufacture and Test a 4m long Helical Undulator Module by end July 2007: • Complete conceptual design by October 2006 • First 2m-long magnet tested by March 2007 • Second magnet and cryostat manufactured by May 2007 • Module assembly and cold test completed by end July 2007 Note: we are not planning to build a field measurement system for 4-m module -> a proposal by ANL to build such a system looks very attractive and necessary -> a formal collaboration with Argonne should probably start.

23. Plans (2) • Beam test of 4-m undulator module at Daresbury Lab – fall 2007. • Pre-production prototype – 2008-09. Funds are requested, awaiting decision.