S. Carr

Development of a Superconducting Helical Undulator for a Polarised Positron Source

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.

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

An undulator based positron source is the baseline for the International Linear Collider (ILC). The HeLiCal collaboration in the UK is working on the development of a full scale 4-m long undulator module. Several prototypes have been built and tested in the R&D phase of the programme that culminated in the development of manufacturing techniques suitable for construction of the first full scale undulator sections. This paper details the design and the construction status of 4-m long undulator module.

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

An undulator based positron source is a baseline for the international linear collider (ILC). The HeLiCal collaboration in the UK is carrying out an R&D programme on a short period superconducting helical undulator with the goal to develop modelling, measuring and manufacturing techniques. Several undulator prototypes have been built and successfully tested. This paper summarizes the results of the R&D phase of the project.

Vacuum systems for the ILC helical undulator

The International Linear Collider (ILC) positron source uses a helical undulator to generate polarized photons of ∼10MeV at the first harmonic. Unlike many undulators used in synchrotron radiation sources, the ILC helical undulator vacuum chamber will be bombarded by photons, generated by the undulator, with energies mostly below that of the first harmonic. Achieving the vacuum specification of ∼100nTorr in a narrow chamber of 4–6mm inner diameter, with a long length of 100–200m, makes the design of the vacuum system challenging. This article describes the vacuum specifications and calculations of the flux and energy of photons irradiating the undulator vacuum chamber and considers possible vacuum system design solutions for two cases: cryogenic and room temperature.

Status of the HeLiCal contribution to the polarised positron source for the International Linear Collider

The positron source for the International Linear Collider (ILC) is a helical undulator-based design, which can generate unprecedented quantities of polarised positrons. The HeLiCal collaboration [1] takes responsibility for the design and prototyping of the superconducting helical undulator, which is a highly demanding short period device with very small aperture, and also leads the start to end simulations of the polarised electrons and positrons to ensure that the high polarisation levels generated survive from the source up to the collision point. This paper will provide an update on the work of the collaboration, focusing on these two topic areas, and will also discuss future plans.

Spin tracking at the international linear collider

Polarized e- and e+ beams are foreseen for the future International Linear Collider (ILC). High precision physics requires the polarization of both beams to be known with a relative uncertainty of about 0.1% or better. Therefore all possible depolarizing effects that could operate between the polarized sources and the interaction regions have to be under full control. This report gives a brief summary of ongoing work on the ILC spin-dynamics concentrating on recent results for depolarizing effects in the ILC damping rings, main linac, beam delivery system and beam-beam interactions. The polarization dependence of incoherent and second order coherent background processes have been taken into account as well as the treatment of spin precession in strong fields.

Progress on a Superconducting Planar Undulator in the UK

Superconducting (SC) undulators can potentially reach a higher field, for short period devices, than permanent magnet devices. The latest design work on a proposed superconducting planar undulator being designed in the UK by the STFC is presented. The initial layout of the undulator, including superconducting fill factor and the cryogenic system is presented. Calculations of the wakefield heating effects due to different vacuum vessels and electron beam configurations are also presented. Another important issue for superconducting planar undulators is the effect of engineering tolerances of the pole pieces: the computer simulated effects, for different size pole errors, on the electron beam trajectory and phase error through the device are also shown.

Challenge of polarized beams at future colliders

A short overview is given about the potential of polarized beams at future colliders is given. In particular the baseline design for polarized beams at the ILC is presented and the physics case for polarized e− and e+ is discussed. In order to fulfil the precision requirements spin tracking from the source to the interaction point is needed. Updates concerning the theoretical calculations as well as their implementation in simulation codes are reported.

Status Of The HeLiCal Contribution To The Polarised Positron Source For The International Linear Collider

The positron source for the International Linear Collider (ILC) is a helical undulator-based design, which can generate unprecedented quantities of polarised positrons. The HeLiCal collaboration [1] takes responsibility for the design and prototyping of the superconducting helical undulator, which is a highly demanding short period device with very small aperture, and also leads the start to end simulations of the polarised electrons and positrons to ensure that the high polarisation levels generated survive from the source up to the collision point. This paper will provide an update on the work of the collaboration, focusing on these two topic areas, and will also discuss future plans.

Depolarization Effects At The ILC

Spin polarization will play an important role in the International Linear Collider (ILC) physics program. The ‘heLiCal’ collaboration aims to provide a foil analysis of all depolarization effects at the ILC. As expected intuitively, the depolarization in damping rings with carefully corrected orbits is shown to be negligible. No noticeable depolarization is observed in the beam delivery system. The major depolarization effects are expected from the beam‐beam interaction. These effects have been evaluated by the ‘heLiCal’ collaboration for a range of ILC parameter sets.