TY - GEN
T1 - Diagnostic measurements on explosive emission cathodes operating at high current densities and UHV pressures
AU - Lynnx, C.
AU - Walter, J.
AU - Neuber, A.
AU - Kristiansen, M.
N1 - Copyright:
Copyright 2012 Elsevier B.V., All rights reserved.
PY - 2011
Y1 - 2011
N2 - Vacuum diodes utilizing explosive emission cathodes generally suffer from non-uniform emission, gap closure by anode and cathode plasma expansion, and outgassing. Also, the Child-Langmuir relation does not apply at the edge of the emission area. This results in a high current density sheath at the edge of the emission area. Each of these phenomena presents its own technical challenge in HPM source design and optimization. Diagnostic techniques and particle in cell simulations for a vacuum diode, to be operated as a greater than 100 MW class vircator, have been used in order to compare the characteristics of the electron beam produced by various cathode materials and geometries. Uniform current density plays a key role in vircator performance and efficiency, as well as in the lifetime of the diode. The diode under investigation has an emission area of 20.3 cm 2, and operates at a current density on the order of 300 A/cm 2 at 200 kV. The background vacuum level and the associated adsorbed and absorbed gases at the surface play a major role in the behavior of an explosive emission cathode. This vircator source is operated as a sealed tube, requiring no vacuum pumping until the device is repetitively operated. The small amount of gas generated during operation is pumped down in between shots, if needed, utilizing an integrated small sputter-ion pump. The background pressure in the diode is in the ultra-high vacuum (UHV) range, on the order of 10 -9 Torr to 10 -8 Torr. Particle in cell simulations were performed to investigate current density distributions at the surface of both the anode and cathode due to various field shaping profiles. Additionally, scintillator images were taken to compare the beam profile of a machined aluminum cathode with a CsI coated carbon fiber cathode.
AB - Vacuum diodes utilizing explosive emission cathodes generally suffer from non-uniform emission, gap closure by anode and cathode plasma expansion, and outgassing. Also, the Child-Langmuir relation does not apply at the edge of the emission area. This results in a high current density sheath at the edge of the emission area. Each of these phenomena presents its own technical challenge in HPM source design and optimization. Diagnostic techniques and particle in cell simulations for a vacuum diode, to be operated as a greater than 100 MW class vircator, have been used in order to compare the characteristics of the electron beam produced by various cathode materials and geometries. Uniform current density plays a key role in vircator performance and efficiency, as well as in the lifetime of the diode. The diode under investigation has an emission area of 20.3 cm 2, and operates at a current density on the order of 300 A/cm 2 at 200 kV. The background vacuum level and the associated adsorbed and absorbed gases at the surface play a major role in the behavior of an explosive emission cathode. This vircator source is operated as a sealed tube, requiring no vacuum pumping until the device is repetitively operated. The small amount of gas generated during operation is pumped down in between shots, if needed, utilizing an integrated small sputter-ion pump. The background pressure in the diode is in the ultra-high vacuum (UHV) range, on the order of 10 -9 Torr to 10 -8 Torr. Particle in cell simulations were performed to investigate current density distributions at the surface of both the anode and cathode due to various field shaping profiles. Additionally, scintillator images were taken to compare the beam profile of a machined aluminum cathode with a CsI coated carbon fiber cathode.
UR - http://www.scopus.com/inward/record.url?scp=84861362810&partnerID=8YFLogxK
U2 - 10.1109/PPC.2011.6191570
DO - 10.1109/PPC.2011.6191570
M3 - Conference contribution
AN - SCOPUS:84861362810
SN - 9781457706295
T3 - Digest of Technical Papers-IEEE International Pulsed Power Conference
SP - 1142
EP - 1145
BT - IEEE Conference Record - PPC 2011, Pulsed Power Conference 2011
Y2 - 19 June 2011 through 23 June 2011
ER -