Electrical signals are fundamental to key biological events such as brain activity, heartbeat, or vital hormone secretion. Their capture and analysis provide insight into cell or organ physiology and a number of bioelectronic medical devices aim to improve signal acquisition. Organic electrochemical transistors (OECT) have proven their capacity to capture neuronal and cardiac signals with high fidelity and amplification. Vertical PEDOT:PSS-based OECTs (vOECTs) further enhance signal amplification and device density but have not been characterized in biological applications. An electronic board with individually tuneable transistor biases overcomes fabrication induced heterogeneity in device metrics and allows quantitative biological experiments. Careful exploration of vOECT electric parameters defines voltage biases compatible with reliable transistor function in biological experiments and provides useful maximal transconductance values without influencing cellular signal generation or propagation. This permits successful application in monitoring micro-organs of prime importance in diabetes, the endocrine pancreatic islets, which are known for their far smaller signal amplitudes as compared to neurons or heart cells. Moreover, vOECTs capture their single-cell action potentials and multicellular slow potentials reflecting micro-organ organizations as well as their modulation by the physiological stimulator glucose. This opens the possibility to use OECTs in new biomedical fields well beyond their classical applications.

a b s t r a c tThe self-modulation instability of long particle beams was proposed as a new mechanism to produce driver beams for proton driven plasma wakefield acceleration (PWFA). The PWFA experiment at the Photo Injector Test facility at DESY, Zeuthen site (PITZ) was launched to experimentally demonstrate and study the selfmodulation of long electron beams in plasma. Key aspects for the experiment are the very flexible photocathode laser system, a plasma cell and well-developed beam diagnostics. In this contribution we report about the plasma cell design, preparatory experiments and the results of the first PWFA experiment at PITZ.

Self-modulation of particle beams in a plasma was proposed as a new concept to enable plasma wakefield acceleration with long driver beams. An experiment is in preparation at the Photo Injector Test facility at DESY, Zeuthen site (PITZ), to demonstrate and characterize self-modulation of an electron beam. Key elements for this are the highly flexible photocathode laser system and the well-developed beam diagnostics. Preparations for the experiment have started at PITZ. In a first step a suitable insertion point for the plasma cell was determined with beam dynamics simulations. It was decided to use laser ionization to generate the plasma since this technique is capable of providing a homogeneous plasma channel with sufficient size (1 mm diameter, 60 mm length) and density (10 15 cm −3 ). Two different ways were found to generate the plasma, utilizing either field ionization with a 1 T W Ti:Sapphire laser or single photon ionization with a 400 mJ ArF excimer laser. As opposed to previously realized designs the ionization laser is coupled from the side, orthogonally to the electron beam direction.

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