Development of a Superconducting Helical Undulator for a Polarised Positron Source

Abstract

A method of producing a polarised positron beam from e + e -pair production in a target by circularly polarised γ-radiation is being investigated. Polarised photons are to be generated by the passage of a high energy electron beam (250 GeV as anticipated in the International Linear Collider -ILC) through a helical undulator. For production of 20 MeV photons, an undulator with a period of 14 mm, a bore of approximately 4 mm and magnetic field on axis of 0.8 T is required. First prototypes have been constructed using both superconducting and permanent magnet technologies which are capable of producing the necessary magnetic field configuration in the undulator. This paper details the design, construction techniques and field measurement results of the first superconducting prototype and compares the results with simulation.

Positron Sources for Future High Energy Physics Colliders

“…This has been addressed and successfully solved by the UK HeLICal Collaboration. After an intensive R&D phase [43] , the collaboration has eventually fabricated and tested a 𝑁 𝑏𝑇𝑖 superconducting helical undulator prototype which has achieved the required parameters [44], Table 3. Advantage of employing a superconducting magnet technology for building a short-period helical undulator has been demonstrated, and a helical superconducting undulator (HSCU) has become a baseline for the ILC positron source undulator.…”

Status of R&D on a superconducting HeLiCal undulator for the ILC positron source

“…1) are wound onto the formers such that the windings form a double helical winding with currents in opposite directions. Some details of winding technique are described in [3]. Prototypes 1-4 were wound with a superconducting wire having a copper-tosuperconductor ratio of 1.35:1 while the final prototypes 5 and 5' use wire with the ratio of 0.9:1, this allowed for an increase in the operation current.…”

Development of a full scale superconducting undulator module for the ILC positron source

“…The wires of the ribbon are interconnected on a printed circuit board at one end of the undulator section. More information on the undulator manufacture can be found in [4]. The sections are wound on a specially built winding machine which is shown in Fig.…”