Refractive Index Figure Of Merit Research Articles

Helicon wave heating and current drive in toroidal plasmas

Investigation of helicon wave heating and current drive (CD) in toroidal plasma has been carried out with the ray-tracing code GENRAY. The wave trajectories, profiles of power deposition and driven-currents are presented. It is shown that increasing the poloidal launch angle does not change the absorption rate of the wave, but moves the peak of the wave deposition toward the plasma core. Wave frequencies in the range of our interest (460 MHz ∼ 480 MHz) do not change the absorption of the wave. Under low parameter plasmas, we find that both the peak position and magnitude of the wave power deposition are dependent on the launched parallel refractive index n||. With increasing the refractive index, the driving efficiency first increases and then decreases. The parallel refractive index figure of merit for mid-plane launching in HL-2M configuration is 3.2. With high plasma parameters, both the position and magnitude of the driving current are weakly dependent on n||. The magnitude of the driven current is determined by both the absorption rate and the value of ξe, which is related to n||. It is also demonstrated that driven current increases with increase of the core plasma temperature and decrease of the core plasma density. The plasma ohmic current seems do not significantly affect the helicon CD efficiency, but moves the driven current toward the plasma core region and narrows the width of the driven current profile. In addition, the preliminary calculations including scrape-off-layer (SOL) suggest that the power absorption rate loss in SOL is about 5%–20%. These results provide a reference and theoretical basis for the design and construction of HL-2M helicon wave system.

Water-Based Terahertz Metamaterial for Skin Cancer Detection Application

We present a highly sensitive detection of skin cancer using a novel water-based terahertz (THz) metamaterial (MM) and a semiconductor film. We apply the application of terahertz pulsed imaging in reflection geometry for the study of skin tissue and related cancers. As a refractive index (RI) sensing application of the proposed device, with placing different sensing materials in the biosensor design, the effective RI will also change that in turn leads to measuring the sensitivity of the biosensor to detect the normal skin and basal cell carcinoma. The RI figure of merit (FOM) value of the proposed device is much higher than that of the sensor using a semiconductor film to detect biomarkers in the literature. Significantly, the sensitivity increases by about 117 $\mu {\mathrm{ m}}$ /RIU and the RI FOM increases by more than 20.53. This results from a combination of size-related factors, leading to field enhancement accompanying strong field localization. We observed the resonance-frequency shift of the THz MM following the RI changing of the detected skin. The dip reflectance resonance has a blue shift for normal skin. Finally, we suggest that this water-based MM can be used to the control of the gene expression. The advantage of our design depends on two factors. First, we used the MM structure that has micro-scale, and the smaller the size of the structure, the more sensitive to the changes in the RI. Second, we used water in our structure, which is very well-suited to the human body, highly bio-absorbable and inexpensive, and abundantly found in nature.