DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2013 EXPERIMENTAL CAMPAIGN Review | Direct submission with log-in | Request submission without log-in
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Title	127: Characterization of Intense Bursts of Millimeter Wave Emission in QH-mode Plasma
Name:	Liubing Yu lbyu@ucdavis.edu	Affiliation:	University of California, Davis
Research Area:	Inductive Scenarios	Presentation time:	Requested
Co-Author(s):	B.J. Tobias, M.E. Austin, C.W. Domier, N.C. Luhmann, Jr.	ITPA Joint Experiment :	No
Description:	The purpose of this experiment is to characterize the intense bursts of the millimeter wave emission in QH-mode using the ECE radiometer system, ECE imaging system and the newly installed RF spectrometer, in order to lead to a plausible explanation for these bursts. This work will be the most important part of my dissertation. In this experiment, only several simple QH-mode will be made to restore the bursts. This experiment will use QH-mode, low collionality discharges with BT optimized for ECE and ECEI view. Several key parameters will be varied including magnetic field, neutron beam power. Highly spatially and temperally measurements of the bursts location, frequency, bandwidth and intensity will be obtained by ECE, ECEI, RF spectrometer. In addition, obtain the best data from CER, BES, FIDA, SXR are very important to interpret the data and explain the phenomenon.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	For the diagnostic, the new RF spetrometer which has been installed on DIII-D since Aug will help characterize the bursts. It can take the signal from both the low frequency antena or one vertial channel of ECEI system, then divided into two part, one goes to regular ECEI module, the other goes to the modified module. In last campaign, it was connected to the low frequency lenses and antenna, which had successfully demonstrated that the bursts from both systems are millimeter wave radiation instead of the low RF frequency interference. For this campaign, it will be connected to the center ECEI channel, which will provide 7 contiguous mimic ECE channels on different toroidal angles. This will help determine the toroidal mode number and structure of the bursts. For the plasma conditions, two key parameters should be varied after bursts appear. One is toroidal magnetic field which might affect the upshifted frequency; the other is neutron beam power, which will affect the collion frequency νei (which is trusted to be important in some static experiences in Ref 1) without big affect on the electron. Reproduce shot 149135, then increase the Bt from 2.0 to 2.1 T during 2500-3500 ms; then turn on the neutron beam at time 2500 ms; then try to reproduce the shot 149135 with Bt=1.9 T and 2.1 T
Background:	The ECE radiometer system and ECE imaging system are both hetedyne systems view at the 2nd harmonic X-mode ECE radiation. Super intense bursts, which go up to 10000 times the blackbody radiation temperature, with duration of 5-10 μs have been observed by both system mainly on three plasma events: disruptions, ELMs in H-mode and in QH-mode. The bursts in EHO in QH-mode have specific phase realtionship with edge magentic fluctuation data (Ref 1) and propagate the same poloidal veloctiy with n=1 EHO (Ref 2); also they are proved to be narrowbanded (1 GHz compared to 3-5 GHz in ELMy cases); all these feastures make them easier to be charactized. There is two kind of bursts in QH-mode which varied in many parameters. One has strong narrowbanded EHO with BT=2 T. It has a MHD threshold for the bursts to initiate and it is highly related to the odd-mode amplitude of δB[Ref. 1]. The bursts are very strong that the actually ECE signal will get saturated most of the time during the bursts as shot 149135. And these bursts has a very narrowband which is smaller than 1 GHz and their upshifted frequency from the EHO locations is 3-5 GHz. The other has broadband EHO with BT=1.9 T. These bursts initiate and disappear without clear connection with δB. The bursts on ECE channel 1 in shot 146473 look like some intense spikes. And their upshifted frequency from the EHO locations is 1-2 GHz.
Resource Requirements:
Diagnostic Requirements:	ECE, ECEI, RF Spectrometer, MSE, CER, SXR, FIDA
Analysis Requirements:
Other Requirements: