The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
The efficacy of protecting electronics from high power microwaves (HPM) through plasma creation depends on how quickly the plasma forms in the protective gas chamber when illuminated with microwave radiation. A cylindrical chamber with polycarbonate windows was filled with a neon, krypton gas mixture and illuminated with a train of ∼25kW, 800ns long pulses at 43Hz repetition rate as a simulation of...
Development of high power microwave (HPM) distributed discharge limiters relies critically on minimizing the delay time between HPM incidence and diffuse plasma creation. We present a range of pulsed plasma experiments conducted in neon, argon, helium, and mixtures of these gases, from 50–760 torr. Breakdown is achieved by illuminating a gas cell with a ∼25kW, ∼2 kV/cm, 800ns-long pulse as well as...
Development of high power microwave (HPM) distributed discharge limiters relies critically on minimizing the delay time between HPM incidence and diffuse plasma creation. We present a series of pulsed plasma experiments conducted in neon, argon, and a 9∶1 mixture of the two gases from 50–760 torr. Breakdown is achieved by illuminating a gas cell with a train of ∼25kW, ∼2 kV/cm, 800ns-long pulses at...
The MadHex experimental system consists of a 150 cm long, 10 cm inner diameter Pyrex tube connected to a stainless steel expansion chamber 60 cm long and 45 cm in diameter (expansion ratio RE = 4.5) with an axial magnetic field, variable up to 1 kG at the source region that is operated in a nozzle configuration. A half-turn double helix antenna, 18 cm long and 12 cm diameter, is used to excite helicon...
The MadHex experimental thruster consists of a 150 cm long, 10 cm inner diameter Pyrex tube connected to a stainless steel expansion chamber 60 cm long and 45 cm in diameter (expansion ratio RE = 4.5) with an axial magnetic field, variable up to 1 kG at the source region that can be operated in nozzle or flat field configurations. An 18 cm long, 12 cm diameter half-turn double-helix antenna is used...
The MadHex experimental system consists of a 150 cm long, 10 cm inner diameter Pyrex tube connected to a stainless steel expansion chamber 60 cm long and 45 cm in diameter (expansion ratio RE = 4.5) with an axial magnetic field, variable up to 1 kG at the source region that can be operated in nozzle or flat field configurations. An 18 cm long, 12 cm diameter half-turn double-helix antenna is used...
Measurements and analysis of air breakdown processes and plasma production by focusing 193 nm, 300 mJ, 15 MW high power laser radiation inside a 6 cm diameter helical RF coil. We observe quantum resonant multi-photon (REMPI)1 and collisional cascade laser ionization processes that produce high density (ne∼5*1015/cm3) cylindrical seed plasmas at 20 Torr. The focused laser and associated shock wave...
We report experiments and analysis of field emission from metallic knife-edge cathodes coated with thin film Lanthanum Hexaboride (LaB6), a low work function material (~2.5 eV). The emission current density is found to depend sensitively on film properties, particularly the thickness of the LaB6 layer. Films thinner than approximately 10 nm greatly enhance the emitted current. However, cathodes coated...
Summary form only given. The design, fabrication and initial measurements and analysis of an X-band high power microwave (HPM) limiter are presented. The microwave discharge test chamber is an L-band rectangular waveguide with Lexan or Rexolite microwave windows. The chamber is illuminated by the output of an X-band waveguide pressed against the chamber window. The objective is to study conditions...
A flowing argon helicon plasma is formed in a 10 cm diameter, 1.5 m long Pyrex chamber with an axial magnetic field in nozzle or flat configuration, variable up to 1 kG in the source region. A new expansion chamber has been constructed and initial laser induced fluorescence (LIF) results including ion velocities and temperatures are presented. Microwave interferometry (105 GHz), collisional radiative...
We report experiments and analysis of field emission from copper knife-edge (CKE) cathodes, both bare and coated with low work function (2.6 eV) Lanthanum hexaboride (LaB6) thin films. The bare CKE cathode exhibits evidence of space charge limited emission currents at high field strengths. The LaB6 coated cathodes exhibit a nonlinear Fowler-Nordhiem (FN) type emission. An intermediate saturation region...
Summary form only given. A flowing argon helicon plasma is formed in a 10 cm diameter, 1.5 m long Pyrex chamber with an axial magnetic field in nozzle or flat configuration, variable up to 1 kG in the source region. Experimental upgrades including a new expansion chamber have been implemented and initial laser induced fluorescence (LIF) results including ion velocities and temperatures are presented...
The design, fabrication, initial measurements and analysis of an X-band high power microwave (HPM) limiter are presented. The microwave discharge test chamber is an L-band rectangular waveguide with Lexan or Rexolite microwave windows. The chamber is illuminated by the output of an X-band waveguide pressed against the chamber window. The objective is to study conditions and configurations that enable...
We report experiments and analysis of field emission from copper knife-edge (CKE) cathodes, both bare and coated with low work function (~2.5 eV) Lanthanum hexaboride (LaB6) thin films. The bare CKE cathode exhibits evidence of space charge limited emission currents at high field strengths. The LaB6 coated cathodes exhibit a nonlinear Fowler-Nordhiem (FN) type emission. An intermediate saturation...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.