Progress on Helical Undulator for Polarised Positron Production

Progress on Helical Undulator for Polarised Positron Production Duncan Scott ASTe. C Daresbury Laboratory Presented by Gudrid Moortgat-Pick 05/02/03

Contents l l l 05/02/03 Introduction Helical Undulator Designs l Super-Conducting l Pure Permanent Magnet Further Work Duncan Scott: LCUK 2

Introduction l l 05/02/03 Looked at different helical undulator designs. l Super-Conductin Wires l Permanent Magnet Helical l Planar Permanent Magnet Helical Carrying out Engineering Feasibilty on two designs Duncan Scott: LCUK 3

Super - Conducting Design l l Magnet Design for 12 & 14 mm periods: l Vacuum Vessel Diameter 4 mm Calculated the magnetic field at the SC wires For 12 mm period this 83% of Critical Field For 14 mm period this 50% of Critical Field l (cf at Critical Field wires become normal conducting) Undulator Period, u Current, i Helix Diameter Current, -i 05/02/03 Duncan Scott: LCUK 4

Permanent Magnet Undulator Design l “Halbach” undulator (Klaus Halbach NIM Vol. 187, No 1) l 05/02/03 PPM blocks create Dipole Field l Rotate many rings to create Helical Field Duncan Scott: LCUK 5

Permanent Magnet Undulator Design l l l Looking at 14 mm period solution Vacuum system difficult Maximum vacuum for stainless steel pipe ~ 10 -7 mbar Therefore NEG coating will be needed However NEG coating a 4 mm diameter tube has never been done 05/02/03 Duncan Scott: LCUK 6

Next - Steps l l l Super-Conducting l Look at other periods & diameters l Solutions for making the former l Iron yoke and non iron vacuum vessel Halbach l Creating the required vacuum l Engineering of magnet holders and alignment of rings Build a prototype of preferred option (or one of each…? ) 05/02/03 Duncan Scott: LCUK 7