1. 1 Scope of PosiPol2008 WS LC related positron source issues (ILC and CLIC) General Capture Section Targets Polarized Particle Physics Laser Applications Experimental efforts Project Plan

2. 2 The PosiPol is a series of workshops dealing with the physics aspects, the suggestions and the open questions concerning a polarized positron source in the framework of the ILC and CLIC projects. The PosiPol 2008 is the third workshop following Posipol 2006 at CERN and 2007 at LAL, Orsay. A primal topic of the workshop is the polarized positron source by laser Compton back-scattering schemes and attention will be paid to a comparison between the Compton and the undulator baseline solution. However, conventional positron sources with various target material, such as metal, liquid metal, and crystal, for the linear colliders, will also be topics of the workshop. The meeting will also focus on the development and coordination of the R&D programs under way and the need for a costing of the different solutions. This workshop is addressed not only to experts and participants in the ILC and CLIC projects, but also to a wider audience and may prove of particular interest to the community studying the application of the Compton radiation source to the industrial and medical field.

3. 3 Why Laser Compton ? i) Independence Undulator-base line e + : use e - main linac, so it can generate necessary gamma-rays. However, target design is not confirmed. Problem on design, construction, commissioning, maintenance Laser-base e + : independent Easier construction, operation, commissioning, maintenance ii) Low energy operation Undulator-base e + : need deceleration Laser-base e + : no problem also liquid target and conventional target. Need independent positron system for LC and CLIC.

4. 4 World-Wide-Web of Laser Compton Laser Compton ILC e+ CLIC e+ Optical Cavity High power laser e- source ILC, ERL Medical applications Industrial applications ERL 4 th Generation light source LW monitor  collider Polari- metry X-ray source Nuclear Assay Diagnostic

5. 5 Summary of my talk. Compton e + source is an advanced alternative of ILC e + source. It is not mature for LC at present. We have world-wide collaboration for laser Compton. Not only for ILC e+ source. Also for many other applications.

6. 6 Hope fruitful discussion. Enjoy good talks. Thank you for your attention.