Alcator C-Mod Weekly Highlights March 1, 2002 Work continued on reassembly of Alcator this week. The installation of the inner divertor, milestone 78, was completed. Work also continued on ICRF, DNB, and Lower Hybrid MIE Project systems. Physics ------- Dmitri Mossessian made a presentation at the ITPA pedestal group meeting at GA, February 26 - 28, on "Recent results of pedestal studies at Alcator C-Mod". He showed scaling studies of pedestal parameters with plasma parameters, talked about the operational region of EDA H-mode, and the conditions for obtaining small ELMs on C-Mod. He also presented the results of ideal MHD stability analysis for both EDA and ELMing discharges and showed that the small ELMs can be associated with medium n coupled peeling/ballooning modes that are unstable in the pedestal region. David Mikkelsen, PPPL, visited GA this week to gain experience with the GYRO turbulence simulation code and the vuGYRO analysis tool. These codes will be applied to simulations of transport in C-Mod plasmas. The Alcator C-Mod FY2004 work proposal has been submitted to DoE OFES. It can be found online at www.psfc.mit.edu/people/censabella/C_Mod_Work_Proposal.pdf Inner Divertor -------------- Milestone 78 was completed on Friday, March 8th. This milestone states that: All components of the inner wall modifications will be installed and made ready for operation. These modifications will strengthen the inner divertor and wall, allowing for operation at higher plasma currents, while simultaneously increasing plasma shaping flexibility for our standard lower single-null divertor configurations. All twenty interlocking inner wall girdle plates have been installed along with the over 1000 moly tiles, tile support plates, and tile keeper hardware. The number of inner wall studs was tripled to better hold these new components. New eddy and halo Rogowski coils, thermocouples, and retro-reflectors have also been installed behind the divertor. Simulations indicate that not only will the new divertor easily survive high current, high field disruptions, but it will also add strength to the inner wall and provide a substantial increase in the heat load capacity of the inner divertor during long pulse AT discharges. A picture of the completed inner divertor installation can be seen at http://www.psfc.mit.edu/cmod/operations/EngImages/Inspection_2001-2002/Disassembly_Assembly/Machine_assembly_A/DCP_0254.JPG Operations ---------- The last port on the cylinder needing modification will be completed by Tuesday of next week. Final cleanup and testing will then be done, followed by installation of the cylinder on the machine. The upper wedge plate was installed and carefully aligned this week, and the installation of the top TF arms was begun. Each arm goes through a process of cleaning, hi-potting, and coating of the feltmetal with graphite before installation. Lower Hybrid MIE Project ------------------------ Fiber-optic cables from the transmitter to the pump controller and HV junction box are installed and ready for termination. Wiring on the TPS systems continues. The electrical panel for the transmitter racks is installed. More components were machined for the LH low power microwave rack, including the master oscillator chassis. PPPL continued to focus on launcher prototype testing and the preparation of drawing packages and specifications for early procurement of long-lead components. ICRF Systems ------------ We have checked crowbars and protection circuits, tuned, and brought up both transmitter #1 and #2 to approximately 1.8 MW into a dummy load. We have also run the #1 and 2 transmitters at 200 kW into a dummy load with a 4 second pulse length. With this test we have begun to qualify the rf system for long pulse operation. Control, fault, and data system hardware performed properly on this initial test. The final version of the new phase demodulator board has been tested and has now been put into production. This board uses a programmable local oscillator and PIC controller to mix signals from 40 to 85 MHz into a 10 MHz IF band. Standard operating frequencies can be loaded into and easily selected from a lookup table. Besides providing very accurate measurements of signal phase and amplitude, over a broad power input range, the board also generates fault signals to protect the transmitters. The response time of the fault circuitry is approximately 1 us. A picture of the board can be found at http://www.psfc.mit.edu/cmod/operations/EngImages/Inspection_2001-2002/Disassembly_Assembly/Machine_assembly_A/DCP_0257.JPG DNB and Related Diagnostics --------------------------- The RFX beam is now installed in the cell along with the new power supplies and the pulse transformer. Utilities and control systems are being hooked up. Some redesign of the DNB duct was necessitated by last minute changes in the beam location. We expect to pump down the beamline early next week. Ron Bravenec, UT-FRC, visited MIT to work on noise reduction in the BES data acquisition electronics and to work on the final design of the MSE/BES fiber-holder. Diagnostics: ------------ Perry Phillips, UT-FRC, is currently visiting MIT and will be here through next week. He met with Josh Stillerman to get the PC data acquisition system for FRC ECE system up and running. He also met with Robert Childs to work out any possible conflicts on the modified ECE mirror system on F-port. He plans to test fit the ECE mirror to the F-port flange. Matt Sampsell, UT-FRC, is visiting MIT this week to repair any damaged BES optical fibers. Travel and Visits ----------------- John Rice and Catherine Fiore were in San Diego last week to participate in the ITPA ITB/T session, which reviewed ITB results in an attempt to develop a definition of what an ITB is, and discussed implementation of an ITB database.