Alcator C-Mod Weekly Highlights March 2, 2001 We continued to maintain transmitters, develop Lower Hybrid systems, fabricate new J-port antenna components, and work on the DNB this week. Physics ------- The first Active MHD Antenna that will be installed on the upper, outer vessel wall has been completed and initial tests indicate that it can stand off at least 2.5 kV in air, which greatly exceeds expected voltages induced by disruptions and by driven currents. Photos of the antenna are available at http://www.psfc.mit.edu/cmod/operations/EngImages/CmodImages.asp?ref=/DIAGNOSTIC S/Active_MHD/ Power tests of the Active MHD Antenna with a 400 W high frequency amplifier will be performed next week. Ken Gentle, University of Texas, presented via video conference at our physics meeting his analysis of density peaking in core barrier experiments from last December. His conclusion was that there was a change in the V/D ratio relative to the non-peaking cases, but that it was not possible to determine whether the improvement is in the pinch term, or the diffusivity, or both. ICRF Systems ------------ Fabrication has begun on the inconel stripline components for the J-Port antenna modifications. The EDM process had to be stopped briefly because of voids/cracks in the inconel billet. New inconel has been supplied and machining is proceeding. Straight sections of the stripline are being machined using conventional techniques in our shop. The stainless steel ground return plates have been completed and are ready to be plated. Modifications to and reassembly of the Faraday screen continue. Maintenance of FMIT #4 has been completed and the transmitter has been tested into a dummy load at 2 MW. Maintenance work continues on FMIT #3. All PC boards for the J-Port antenna control upgrade have been fabricated. One board (fault indicator) has been tested and is operational. Two more boards (phase balance) remain to be tested and debugged. All meters for FMIT #3 and #4 have been installed and calibrated. Meters connected to Driver #3 will be re-calibrated when the driver is reinstalled. The board layout files for the new demodulator board have been sent to the manufacturer for prototype fabrication. We continue development of an acoustic arc detection system. Shielded boxes were installed around the piezoelectric detectors that greatly reduced electrical pickup and allowed acoustic delays to be measured. DNB --- During this week, the mechanical design for the H-alpha detectors to monitor wall/beam interactions in the DNB duct was completed and parts ordered. The CXRS shutter design moved forward, and is nearly complete. This includes both the cable runs from outside the machine as well as the modification to the in-vessel optical holder. A design review of this shutter is planned for next week. Lower Hybrid Project -------------------- A test panel with splitter, vector modulator, I/Q detector, amplifier, isolator and directional couplers was assembled. Characterization of vector modulator and I/Q detector operation is now underway. New arc detection schemes and test plans were discussed in some detail this week. We are addressing concerns by the review committee that the planned detection system will miss arcs at the launcher. The four klystron carts will be installed on a new mezzanine in the cell following the next run campaign. A meeting was held this week to discuss safety issues during testing of the klystrons and HVPS. Procedures will be developed and safety indicators in the cell will be specified. We have received updated HVPS container foundation drawing from Thomcast. The drawing was reviewed and some suggested changes or modifications were prepared to submit back to Thomcast. The suggestion are mainly to simplify the construction process and add stability and strength to the container anchoring. Requisitions for LH transmitter instrumentation and control electronics were prepared and released. The mechanical configuration of LH transmitter instrumentation and control cabinets has been designed. This design was required before connectors could be selected and detailed pin outs could be specified. Modification and wiring of the klystron carts continues. Responses to comments from the Lower Hybrid Review committee have been prepared. Inner Divertor -------------- The inner divertor C and backing plate fabrication continues on schedule. Tiles continue to be produced and checked through QA. Travel and Visits ----------------- Sergei Mirnov (TRINITI) and Igor Semenov (Kurchatov) visited the PSFC on Monday. They accompanied Leonid Zakharov who gave the Monday Nuclear Engineering seminar, and spent time in discussions with several C-Mod staff members, on topics ranging from disruption dynamics to the possibility of using MDSplus for data acquisition on T-10. Following the regular weekly C-Mod Physics Meeting, Dr. Mirnov gave an informal seminar on recent Lithium limiter experiments on T11-M tokamak at Troitsk. David Mikkelsen and Stewart Zweben from PPPL spent the week at MIT. David worked on transport modeling, and Stewart worked on his edge turbulence imaging diagnostic. Mike Zarnstorff also visited from PPPL on Friday and gave the PSFC seminar. Rejean Boivin gave a colloquium to the Physics department at the University of Montreal on C-Mod and fusion in general. He also met with representatives who were present at the APS-DPP teacher's day (Quebec city -- October) to discuss feedback from the meeting, and plans for the future. He also made contact with officials from the Montreal Science Museum who wanted to learn more about plasmas and fusion and had heard about the teacher's day. Miklos Porkolab attended the VLT-PAC meeting in San Diego, on Feb 22,23. He also gave a talk at the US-Japan Workshop on Plasma Control and Sustainment Using RF Waves. The title of the talk was "Progress in ICRF Experiments on Alcator C-Mod and Future Plans". This workshop was held at General Atomics on Feb. 22,23 also. Subsequently, Miklos attended the FESAC meeting in Gaithersburg, MD, on Feb 27,28, and participated in the March 1st Fusion Congressional Outreach Day activities. Earl Marmar went to a JET collaboration discussion at OFES in Germantown on Feb 26.