1. T Bradshaw On behalf of the SCU group 1 Status of the Superconducting Undulator Development in the UK Superconducting Undulator Workshop, Rutherford Appleton Laboratory 28 th April 2014

2. 2 Introduction 2 Outline of the current UK developments in Superconducting Undulator Technology Start with a brief retrospective of the Helical Undulator Planar undulator specification Major concerns and how we are handling those concerns Status Many people have contributed to the developments RAL Technology Department on Harwell Campus ASTec at Daresbury Laboratory Diamond Light Source on Harwell Campus

3. 3 Helical Undulator 3 Design principles have grown from the work on Helical Undulator for the International Linear Collider: Undulator Period11.5 mm Field on Axis0.86 T Peak field homogeneity <1% Winding bore >6mm Undulator Length147 m Nominal current 215A Critical current ~270A Manufacturing tolerances winding concentricity20µm winding tolerances 100µm straightness100µm NbTi wire Cu:Sc ratio 0.9 Winding block9 layers Ribbon7 wire +-

4. 4 Helical Undulator 4

5. 5 5 Fourier transform: Very pure sine wave Peak corresponds to 11.5mm period

6. 6 Integration into Cryostat 6 Magnet was integrated into cryostat and tested with current Field measurements in full cryostat were not attempted

7. 7 Planar Undulator 7 Development of a Superconducting Undulator for the Diamond Light Source Magnetic length ~2Metres TBD by the physical length of gap and modelling Total length 2486Millimetres Confirmed by Diamond 22/9/11 Period at Room Temp. 15.5Millimetres Confirmed by Diamond 12/12/12 Period at 4.2K >15.45Millimetres Field on axis >1.25TeslaAt Operating Temp K (undulator parameter) >1.804 Minimum Physical Aperture 5.4Millimetres (Vertical) Including bore tube 64Millimetres (Horizontal) RMS phase error <3DegreesRequired <2DegreesDesirable Trajectory straightness +/- 1Microns Both planes, after average angle removal, 3.0147 GeV +/-5Microradians First Field Integral (H+V) <+/-0.5Gauss*MetresWithin +/-10mm H, V on axis <+/-1Gauss*MetresWithin +/-20mm H, V on axis Second Field Integral (H+V) +/-1Gauss*Metre 2 Within +/-10mm H, V on axis +/-2Gauss*Metre 2 Within +/-20mm H, V on axis Normal and skew multipoles (integrated over +/-10mm in H) <50GaussQuadrupole <50Gauss/CentimetreSextupole <50Gauss/Centimetre 2 Octupole

8. 8 Major Concerns 8 TolerancesVery tight ~10µm (Ben Shepherd and Tim Hayler talks) Quench protectionThermal issues – one coil should not be a problem but 2m module is. (Vicky Bayliss talk) Cooling and thermal issuesNeed temperature margin on the conductor – run at 2K (T Bradshaw later talk) Wakefield/beam/cavity heating beam tube design Field MeasurementAccuracy.. Mechanical(Tim Hayler talk) Insulation and potting Forces Joints and interconnectsLarge number of these Mounting of unitsBolt together or leave a gap? Everything really, this is a tough project ………….

9. 9 Implementation 9 The specification means that the tolerances on the manufacture are very tight (Ben Shepherd talk). Typically we are looking at ~10µm tolerances or of that order Magnetic length:2 m Period :15.5 mm Field on axis:1.266 T -> K =1.8 Beam stay clear: 5.4 mm (Vert.) x 60 mm (Horiz.) rms phase error: < 3 degrees (target 2 degrees) Trajectory straightness: +/- 0.5 micron

10. Implementation The end poles are stepped to ensure that the beam trajectory is straight. (Note that the trajectory can effect the phase error). End windings have odd numbers of layers to make winding easier 579············Coil layers = 2.354.83.83············ Pole heights = 11 4.8

11. 11 Early Prototype tests 11 Accurate translational stage Top Plate Carbon fibre rod supporting Hall probe Test Undulator

12. 12 Prototype tests 12 Highest field magnetic measurement at 260A Maximum magnet quench at 287A –need 407A Issues with cracking on potting material Peak fields on back of winding – need to improve spacing Periodicity from sin fit at all currents is 14.995mm +/-0.001mm at RT (10-100mA) 14.963mm +/-0.001mm at 4K (10-260A) Re-evaluation on how it is made

13. 13 Test Pieces 13 Winding trials and test pieces showing good winding technique: Section from straight, showing wires level with poles. Coil height measures 4.03 to 4.05mm.

14. 14 Test Pieces 14 Profile of former has undergone many revisions to ease the winding process Metrology is key to understanding the machining processes

15. 15 Wire Quality 15 Wire found to have voids:

16. 16 Voltage Breakdown tests 16 Wire quality has been found to be an issue and details of winding has caused problems with electrical breakdown. Looked at winding issues to reduce abrasion Looked at insulation layer position and thickness Looked at potting issues Now achieved good results: Location Max calculated voltage (VB) AchievedNotesSafety factor Coil to ground (end winding to ground) 3000V4500V On steel testpiece, 0.5mm isopon (no vacuum impregnation) 1.5 Turn-to-turn120V1000V (pass) Three short samples, Vacuum Impregnated at 60C with RAL230 (note 1) 8 (minimum) Coil-to- crossover wire 430V1200VOn 4cf #2 with wire on Araldite 2014. Expected to improve with addition of isopon. 2.8

17. 17 Forces 17 Forces are enough to cause problems with alignment and positioning (Tim Hayler talk)

18. 18 Interconnects 18 Using crimps for the joints and interconnects – we have a large number of these so they need to be reliable and fully superconducting. Looking at finding a more compact crimp tool

19. 19 Testing 19 Guillotine approach to Hall probe carriage Arrangement made to minimise crabbing Carriage and rails GRP construction Concentric guide wheel and axel Eccentric guide wheel and axel

20. 20 Testing 20 Formers sit on beam inside test cryostat We will be testing at 4K only

21. Summary 21 Large number of difficult technologies in this build – ticking off all of the technological challenges Status: Just about ready to build end magnet pieces Prototype straight formers – have a drawing and a design Building up test cryostat for magnetic measurements/training prior to build Possible to build the magnet but difficult! Other talks will be dealing with the details of the technical challenges

22. 22 END