Cornell University Unit Name

"Polarised Positron Source"

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Efficient production of polarised positrons can be achieved using a helical undulator based system, where circularly polarised photons (~10MeV) generated from a high-energy electron beam in the undulator produce longitudinally polarised electron-positron pairs in a thin target. While a conceptual design of a non-polarised (planar undulator) based source exists, critical R&D for both polarised and non-polarised sources still remains. Specifically: complete design of the undulator; design of the spin rotation and spin flipper systems; design of the photon collimator and conversion target; optimisation of system parameters to achieve maximum polarisation and positron yields; understanding of the systematic polarisation errors; engineering design and full simulation of the system; location and performance specifications of the required diagnostics (low-energy polarimeter).

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• What are the goals of this R&D project. How does this R&D project address the needs of one or more of the detector concepts?

• If there are multiple institutions participating in this project, please describe the distribution of responsibilities.

• Are there significant recent results?

• What are the plans for the near future(about 1 year)? What are the plans on a time scale of 2 to 3 years?

• Are there critical items that must be addressed before significant results can be obtained from this project?

• Is the support for this project sufficient? Are there significant improvements that could be made with additional support?