TY - GEN
T1 - Evolution of plasma density generated by high power microwaves
AU - Beeson, Sterling
AU - Neuber, Andreas
PY - 2012
Y1 - 2012
N2 - The relaxation time of pulsed rf-generated plasma is investigated. A 3 MW, 3 μs width, 50 ns risetime HPM pulse is transmitted through a dielectric window that terminates a WR-284 waveguide filled with insulating gas. The investigated plasma is formed across the dielectric window on the atmospheric side. This produces electron densities on the order of 1013 to 1012 cm3 for 60 to 145 torr in air, respectively. In the same pressure range, initial attenuation ( 0.5 dB) of the microwaves is observed after tens to hundreds of nanoseconds with final attenuation values approaching 40 to 10 dB, respectively. To determine plasma relaxation times after the HPM pulse terminates a multi-standard waveguide coupler (X/S-band) was designed to inject a low power 10 GHz signal used for probing the surface plasma. The coupler was designed to have high coupling coefficients (> 5 dB) for the specific narrowband around 10 GHz (BW 10 MHz) along with negligible insertion loss of the HPM propagation. From the measured attenuation and reflection of the 10 GHz probe signal, the evolution of the electron density is inferred. Furthermore, in an air environment, the density falls exponentially implying attachment as the dominate electron loss mechanism.
AB - The relaxation time of pulsed rf-generated plasma is investigated. A 3 MW, 3 μs width, 50 ns risetime HPM pulse is transmitted through a dielectric window that terminates a WR-284 waveguide filled with insulating gas. The investigated plasma is formed across the dielectric window on the atmospheric side. This produces electron densities on the order of 1013 to 1012 cm3 for 60 to 145 torr in air, respectively. In the same pressure range, initial attenuation ( 0.5 dB) of the microwaves is observed after tens to hundreds of nanoseconds with final attenuation values approaching 40 to 10 dB, respectively. To determine plasma relaxation times after the HPM pulse terminates a multi-standard waveguide coupler (X/S-band) was designed to inject a low power 10 GHz signal used for probing the surface plasma. The coupler was designed to have high coupling coefficients (> 5 dB) for the specific narrowband around 10 GHz (BW 10 MHz) along with negligible insertion loss of the HPM propagation. From the measured attenuation and reflection of the 10 GHz probe signal, the evolution of the electron density is inferred. Furthermore, in an air environment, the density falls exponentially implying attachment as the dominate electron loss mechanism.
KW - High power microwaves
KW - Plasma
KW - Relaxation
KW - Surface flashover
UR - http://www.scopus.com/inward/record.url?scp=84879911697&partnerID=8YFLogxK
U2 - 10.1109/IPMHVC.2012.6518710
DO - 10.1109/IPMHVC.2012.6518710
M3 - Conference contribution
AN - SCOPUS:84879911697
SN - 9781467312233
T3 - Proceedings of the 2012 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2012
SP - 187
EP - 190
BT - Proceedings of the 2012 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2012
T2 - 2012 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2012
Y2 - 3 June 2012 through 7 June 2012
ER -