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Register a new userElectron neutral collision frequency measurement with the hairpin resonator probe
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Electron neutral collision frequency is measured using both grounded and floating hairpin resonator probes in a 27 MHz parallel plate capacitively coupled plasma (CCP). Operating conditions are 0.1-2 Torr (13.3-267 Pa) in Ar, He, and Ar-He gas mixtures. The method treats the hairpin probe as a two wire transmission line immersed in a dielectric medium. A minimization method is applied during the pressure and sheath correction process by sweeping over assumed collision frequencies in order to obtain the measured collision frequency. Results are compared to hybrid plasma equipment module (HPEM) simulations and show good agreement.
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The collision frequencies of electron-neutral-particle in the weakly ionized complex plasmas with the non-Maxwellian velocity distributions are studied. The average collision frequencies of electron-neutral-particle in the plasmas are derived accurately. We find that these collision frequencies are significantly dependent on the power-law spectral indices of non-Maxwellian distribution functions and so they are generally different from the collision frequencies in the plasmas with a Maxwellian velocity distribution, which will affect the transport properties of the charged particles in the plasmas. Numerically analyses are made to show the roles of the spectral indices in the average collision frequencies respectively.
We study the collision frequency of electron-neutral-particle in the weakly ionized plasma with the power-law velocity q-distribution and derive the formulation of the average collision frequency. We find that the average collision frequency in the q-distributed plasma also depends strongly on the q-parameter and thus is generally different from that in the Maxwell-distributed plasma, which therefore modifies the transport coefficients in the previous studies of the weakly ionized plasmas with the power-law velocity distributions.
We present a wafer trimming technique for producing superconducting micro-resonator arrays with highly uniform frequency spacing. With the light-emitting diode (LED) mapper technique demonstrated previously, we first map the measured resonance frequencies to the physical resonators. Then, we fine-tune each resonators frequency by lithographically trimming a small length, calculated from the deviation of the measured frequency from its design value, from the interdigitated capacitor. We demonstrate this technique on a 127-resonator array made of titanium-nitride (TiN) and show that the uniformity of frequency spacing is greatly improved. The array yield in terms of frequency collisions improves from 84% to 97%, while the quality factors and noise properties are unaffected. The wafer trimming technique provides an easy-to-implement tool to improve the yield and multiplexing density of large resonator arrays, which is important for various applications in photon detection and quantum computing.
In the recent years, the hydrofluoroolefine HFO1234ze(E) (C3H2F4) has been subject to a growing interest for refrigerant applications. This novel gas is also considered a promising alternative in gaseous particle detectors and gaseous voltage insulation devices, thanks to its low global warming potential. In this contribution, measurements of electron transport coefficients and reaction rates in C3H2F4 are analyzed by an iterative procedure. A complete set of scattering cross sections for electrons in C3H2F4 has been obtained and validated by a systematic comparison of electron swarm parameters with experimental measurements in pure C3H2F4 as well as in gas mixtures of C3H2F4/CO2. Since the electron attachment of C3H2F4 is strongly influenced by the gas density, accurate calculations of the critical electric field strength in such mixtures are also reported in this paper.
A new type of laser photodetachment (LPD) technique has been developed for the measurement of electron sheath thickness around an electrostatic probe and for the measurement of the length of collection region of photodetached electrons (PDE). When a thickness of the sheath formed around an electrostatic probe is thicker than about 0.1 mm, modification of the temporal evolution of the LPD signal is observed. By making use of the modification, we evaluated sheath thickness around a cylindrical probe in the existence of the magnetic field of 15 mT. It was found that the thickness of electron sheath along the magnetic field was comparable to the calculated plane-parallel Child-Langmuir sheath thickness when the probe-bias voltage was high. Furthermore, by inserting a small screening object in the laser beam channel, we can measure the sheath thickness from the modification of LPD signal. From the variation of the signal intensity as scanning the screening object perpendicular to the laser beam channel, we can observe the collection region of photodetached electrons, because this procedure changes the relative displacement between shadow and the probe electrode.
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