D. P. Barber

The role of polarized positrons and electrons in revealing fundamental interactions at the Linear Collider

The proposed International Linear Collider (ILC) is well-suited for discovering physics beyond the Standard Model and for precisely unraveling the structure of the underlying physics. The physics return can be maximized by the use of polarized beams. This report shows the paramount role of polarized beams and summarizes the benefits obtained from polarizing the positron beam, as well as the electron beam. The physics case for this option is illustrated explicitly by analyzing reference reactions in different physics scenarios. The results show that positron polarization, combined with the clean experimental environment provided by the linear collider, allows to improve strongly the potential of searches for new particles and the identification of their dynamics, which opens the road to resolve shortcomings of the Standard Model. The report also presents an overview of possible designs for polarizing both beams at the ILC, as well as for measuring their polarization.

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.

Spin transport, spin diffusion and Bloch equations in electron storage rings

Abstract We show how, beginning with the Fokker–Planck equation for electrons emitting synchrotron radiation in a storage ring, the corresponding equation for spin motion can be constructed. This is an equation of the Bloch type for the polarisation density.

ACCURATE AND EFFICIENT SPIN INTEGRATION FOR PARTICLE ACCELERATORS

Accurate spin tracking is a valuable tool for understanding spin dynamics in particle accelerators and can help improve the performance of an accelerator. In this paper, we present a detailed discussion of the integrators in the spin tracking code gpuSpinTrack. We have implemented orbital integrators based on drift-kick, bend-kick, and matrix-kick splits. On top of the orbital integrators, we have implemented various integrators for the spin motion. These integrators use quaternions and Romberg quadratures to accelerate both the computation and the convergence of spin rotations. We evaluate their performance and accuracy in quantitative detail for individual elements as well as for the entire RHIC lattice. We exploit the inherently data-parallel nature of spin tracking to accelerate our algorithms on graphics processing units.

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.

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.