Alcator C-Mod Weekly Highlights June 29, 2009 FY2009 weeks of research operations Target: TBD Completed: 0 weeks Operations ----------- Plasma operations resumed on Alcator C-Mod last week with startup and commissioning shots. The MIT Alternator operated nominally in support of C-Mod operations Monday through Friday. Power system testing was completed on Monday with successful operation of the toroidal field magnet up to our routine operating field of 5.4 tesla. After testing and troubleshooting of the DPCS control system, we succeeded in obtaining a satisfactory field null and breakdown plasma on Tuesday, and successful current rise to over 500kA on Wednesday. On Thursday and Friday we continued to produce clean-up plasmas, increasing the plasma current up to 1MA and extending the pulse duration to over 1.5 seconds. Discharge conditions are still dirty and most of the fueling is from the walls, as is typical for the first days of operation following an up-to-air. A total of 15 plasma discharges were produced during the week. By Friday the startup reliability had increased to 38%. Additional conditioning plasma operation is planned for this week. Program Planning ----------------- The first C-Mod Experimental Program Committee meeting of the 2009 campaign was held on Monday, June 22, under the leadership of the new EPC Chairman, Martin Greenwald. One new miniproposal was reviewed and approved. Discussions focused on longer range planning meant to guide the weekly scheduling. In order to maximize research operation during the current fiscal year, configuration changes which require extra maintenance days or that will cost us in recovery time need to be minimized; these considerations will constrain the experiments that can be undertaken. Additional restrictions on near-term operation were agreed in order to permit initial evaluation of new or modified hardware including boron coated tiles, new diagnostics for the SOL footprint, and modifications to MSE. The next EPC meeting is scheduled for Monday, June 29. ICRF Systems ------------ Restart of FMIT#1 and FMIT#2 transmitters have progressed to the point that power tests into dummy load could be attempted. Both #1 and #2 had high voltage applied successfully and FMIT#2 was tested to 1.75 MW into dummy load. Before the E-port (FMIT#2) is operated into plasma, we need to bring the fast ferrite tuners (FFT's) online and purge the transmission lines. The cell data aquisition system also needs to be brought online. FMIT#1 recently had a new final power amplifier tube installed, and has been tested up to 1.2 MW before saturating. Additional tuning will be required to bring the system to full power. The low power RF system also needs to be restored before the system is available for plasma operation. Lower Hybrid System ------------------- High power testing of the prototype "magic tee" waveguide splitter was carried out with scenarios including matched loads, shorts, and spacers. The magic tee was able to handle full reflection conditions without arcing. Initial electrical testing of the new directional couplers was also begun. Three couplers were tested successfully so far, and two have also passed helium leak detection tests. A meeting was held with the vendor working on our new Transmitter Protection System (TPS) upgrade under an SBIR contract. We accepted the first delivery of analog multiplexer modules for testing. Work continued on code development and testing for the Coupler Protection System (CPS). Diagnostic Systems ------------------- Diagnostic systems are being brought on-line and checked out during plasma operation. Magnetics diagnostics for equilibrium reconstruction and plasma control are operational. Visible light signals including D-alpha and CIII brightness, the tangential visible Bremstrahlung (Z-meter), and H-alpha/D-alpha ratio are operational. The TCI interferometer (line-averaged density) is also online and in use for density feedback control. Electron cyclotron emission diagnostics including the GPC and GPC-2 grating polychromators and the Michelson are operational but not yet calibrated. The 2pi diode bolometer is on-line but not yet calibrated. Neutron diagnostics are operational. Soft x-ray tomography diagnostics are on-line. The hard x-ray monitor is operational in a temporary location. The high resolution x-ray spectroscopy (HIREX-JR) diagnostic is online and operational. Travel and Visitors -------------------- Aaron Bader, Paul Bonoli, Bob Harvey (COMPX), Yijun Lin, Orso Meneghini, Ron Parker, Miklos Porkolab, Andrea Schmidt, Syunichi Shiraiwa, Greg Wallace, Randy Wilson (PPPL) and John Wright attended the 18th Topical Conference on Radio Frequency Power in Plasmas in Gent, Belgium on June 24-26, 2009. Invited papers were presented by Lin, "Observation of Flow Drive during ICRF mode conversion experiments in Alcator C-Mod", Parker, "Modification of current profile, toroidal rotation and pedestal with LHCD in Alcator C-Mod", and Wright, "Full-wave simulations of lower hybrid wave propagation in tokamaks". The C-Mod presentations can be found at http://www.psfc.mit.edu/research/alcator/pubs/RF/rf2009index.html Stewart Zweben (PPPL) was at MIT last week to help set up the GPI diagnostic for this campaign. First light signals were seen during plasma start-up experiments in the two Phantom 7.3 cameras from the two GPI imaging systems. Stewart also discussed plans for experiments for this run, and brought to C-Mod the (repaired) PSI-5 camera for ultra high speed imaging. Dennis Whyte participated remotely in the DIII-D particle balance experiments that were oriented towards the 2009 Joint-facility Joule milestone. _______________________________________________ Cmod_weekly mailing list Cmod_weekly@lists.psfc.mit.edu http://lists.psfc.mit.edu/mailman/listinfo/cmod_weekly