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1 st Workshop on Photo-cathodes: 300-500nm

Join us at the 1st Workshop on Photo-cathodes to discuss and explore new directions, materials, techniques, and geometries for building a cost-efficient single-photon detector with high efficiency and bandwidth optimization. Identify the most promising conventional materials for high-QE, low-noise cathodes and contribute to narrowing the possibilities for this year's work on photo-cathodes.

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1 st Workshop on Photo-cathodes: 300-500nm

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  1. 1st Workshop on Photo-cathodes: 300-500nm July 20-21, 2009: University of Chicago Klaus Attenkofer, Karen Byrum, Henry Frisch, Oswald Siegmund

  2. Motivation for the workshop:How to build a Single-Photon-Detector better than a PMT? • Existing project for large area detector with single photon capability, time resolution of up to 1ps and 300µm spatial resolution. • The new detector should be cost efficient and “easy” to build (in comparison to PMT based systems) • What can we learn from the various communities to make a “perfect” photo-cathode.

  3. The Three Criteria: Long lifetime of the device & easy to assembly High efficiency& bandwidth optimization “Good” noise behavior What is the best structure for a good and cost-efficientPhotocathode?

  4. What is Our Goals? • Discuss and agree on the basic underlying physics processes(Finding a common Language) • Bring up and explore new directions, materials, techniques, and geometries • Elucidate the trade –offs between conventional choices:transparent/reflective, bialkali/III-V, etc. • Clarify the requirements for large-area photo-cathodes(Vacuum, fabrication, lifetime, mechanical & chemical) • Identify the most promising conventional materials for high-QE, low-noise cathodes in the 300-500nm range • Identify additional resources, facilities, and (possibly) collaborative efforts • Contribute to narrowing the possibilities for this year’s work on photo-cathodes to a few most promising paths

  5. Thank you for coming and enjoy the workshop

  6. High Efficiency and Bandwidth Optimization: • What are the best ways to reduce reflection losses, what are the problems • Pattering of substrate / nano-structures • Reflection versus transmission geometries • Refractive index matching • ?????? • Thickness optimization of the active layer • State-of-the-art simulation of electron and photon • Optimization of doping profile and how to make it • External versus internal electric fields • The negative electron affinity (NEA) layer • The chemistry and crystal structure of the layer • Long term stability • Ion etching and how to protect the cathode • Are there new (nano-)technologies which can help

  7. Lifetime of the Device and How to Assembly • Chemical and mechanical damage of the cathode • The process and is there a way of quantitative understanding • Effects of various gasses • Protective layers • Membranes: influence on time structure, efficiency, and noise. • Cathodes with alternative geometries (like reflection geometry) • Assembly issues • What are the vacuum requirements in the final detector (partial pressures?) • Which fabrication steps can be done in foundries and what has to be done in a precise vacuum/gas atmosphere • Final assembly in vacuum or ultra-pure gas atmosphere • How does the production line look like

  8. What Determines the Noise Behavior • Dopants and defects • Is there a basic understanding on the effects of different dopants (electron scattering, thermal excitation, E-field-strength effects) • Correlation between free carriers and macroscopic quantities like refractive index, DC/RC dielectric constant. • Field emission • Limitations of the external field for nano structured surfaces • Effects of dopants on local field distributions • Spectral response • How precise can the bandwidth be matched to the source • Thermal effects in detectors • Influence of high count rate • …………

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