Development of Polarized Photocathodes for the Linear Collider

In prior years a Wisconsin-SLAC collaboration developed polarized photocathodes which were used for the SLAC SLD and fixed target programs. Currently, the R&D program goal is the development of a polarized electron source (PES) which meets the ILC requirements for polarization, charge, lifetime, and pulse structure. There are two parts to this program. One part is the continued improvement of photocathode structures with higher polarization. The second part is the design and development of the laser system used to drive the photocathode. The long pulse train for the ILC introduces new challenges for the PES. More reliable and stable operation of the PES may be achievable if appropriate R&D is carried out for higher voltage operation and for a simpler photocathode load-lock system. The collaboration with SLAC is through the Polarized Photocathode Research Collaboration (PPRC). Senior SLAC personnel include T. Maruyama, J. Clendenin, R. Kirby, and A. Brachmann

Improved Electron Yield and Spin-Polarizaton from III-V Photocathodes Via Bias Enhanced Carrier Drift

Spin-polarized electrons are commonly used in high energy physics. Future work will benefit from greater polarization. Polarizations approaching 90% have been achieved at the expense of yield. The primary paths to higher polarization are material design and electron transport. Our work addresses the latter. Photoexcited electrons may be preferentially emitted or suppressed by an electric field applied across the active region. We are tuning this forward bias for maximum polarization and yield, together with other parameters, e.g., doping profile. Preliminary measurements have been carried out on bulk and thin film GaAs. As expected, the yield change far from the bandgap is quite large for bulk material. The bias is applied to the bottom (non-activated) side of the cathode so that the accelerating potential as measured with respect to the ground potential chamber walls is unchanged for different front-to-back cathode bias values. The size of the bias to cause an appreciable effect is rather small reflecting the low drift kinetic energy in the zero bias case

The iNanoBIT project: integration of Nano - and Biotechnology for Beta-cell and Islet Transplantation

Preclinical trials with porcine pancreatic islets have started and in recent years major progress has been made, particularly in the development of novel immunosuppressive regimens and genetically multi-modified donor pigs with an excellent potential to become a clinically relevant option for the treatment of type-1 diabetes (T1D). Ethical and regulatory frameworks for this new branch of medicine are currently being developed, including safety requirements. High resolution imaging of the function and faith of transplanted porcine xenoislets and beta-cells in large animals and patients for testing ATMPs is a currently unmet need for preclinical/clinical testing. The iNanoBIT EU H2020 project is aimed to apply nanotechnologies for imaging porcine pancreatic islet cellular transplants and induced pluripotent stem cell-derived beta-cells and subsequent regenerative processes in vivo in a porcine model. The project is developing novel highly sensitive nanotechnology-based imaging approaches allowing for monitoring of survival, engraftment, proliferation, function and whole body distribution of the cellular transplants in a preclinical porcine model with excellent translational potential to humans. We develop and validate the application of SPECT and optoacoustic imaging technologies in preclinical transgenic humanized type-1 diabetic pig model to observe transplanted porcine xenoislets and in vitro differentiated human beta-cells. The consortium of 5 SME and 3 Academic partners is progressing in generating new transgenic reporter pigs and human induced pluripotent cell lines for optoacoustic imaging and testing them in transplantable bioartificial islet devices. Novel nanomolecules have been generated and being tested for nuclear imaging of islets and beta-cells using a new, high-resolution SPECT imaging device for large animals. Overall, the combined multidisciplinary expertise of the project partners allows progress towards creating much needed technological tool-boxes for the xenotransplantation and ATMP field, and thus reinforce the European healthcare supply chain for regenerative medicinal products