Discharge tube

A quartz tube having a needle cathode as electron emitter for a narrow field electron emission (tip diameter 1 um) resulting in a coherent stream of electrons with a high beam current density.  The cathode fed by low voltage pulses. An anode having the same geometry as the cathode (for symmetry reason) has a large electron collection area. The anode wall is grounded. The object with this anode design is to lower the voltage gradient.

 The quarts tube may be filled with hydrogen. The tube runs at hot conditions. In the space between cathode and anode, photons are created at high dV/dt by vacuum particle reactions during tunneling and by photoelectric effect. Light from a hydrogen filled discharge tube has a most intense transition with the emission of red light at 656 nm.

A photovoltaic cell adapted to the wavelength of the photon emissions (mainly infra red light) encloses the quartz tube. Of special interest is thermophotovoltaics (TPV) converting both thermal radiation and photons into electricity. ​These cells can be made very efficient. More information about TPV can be found in patent WO2017223305A1.

The following Step 1- 4 show some colorized computer illustrations providing some thinking on how this may work.