Thrust 04 ChitID 04.001 Richard Hawryluk 6/08/2009 14:24 Thrust 04 I would highlight in the issue of H-mode confinement the importance of understanding not only the L to H power threshold but the H to L power threshold. This may be more important or at least as important for ITER. ChitID 04.002 Richard Hawryluk 6/08/2009 14:36 Thrust 04 There has been considerable work on using ICRF to condition SC tokamaks. That should be mentioned since it may mean that we do not need to develop variable frequency ECH. ChitID 04.003 David Hill 6/08/2009 16:45 Thrust 04 Seems like wall conditioning would belong under thrusts 10 or 11 ChitID 04.004 Rob Goldston 6/08/2009 16:51 Thrust 04 Have you estimated the heating power density from ECDC? One needs rather high heating power to raise the surface temperature enough to desorb T. I would be a bit surprised if 1 MW did the job, but maybe the spot size is small enough. ChitID 04.005 Richard Callis 6/08/2009 16:53 Thrust 04 With respect to ICRF antennas,a topic not mentioned is the effect on antenna performance from deposited erosion products. Does this lead to impurity transport, voltage stand-off degradation etc.? What about ICRF coupling and plasma antenna gap relationships. The proposed localized gas puffing may not be practical because of the large throughput required. ChitID 04.006 David Hill 6/08/2009 16:57 Thrust 04 Even though we understand the ECH propagation and absorption, is the energy confinement for ECH-heated plasmas understood well enough that we can predict performance in ITER? Should this be part of this thrust? ChitID 04.007 Rob Goldston 6/08/2009 17:06 Thrust 04 In what ways would the new facility you are discussing be significantly different from the three Asian tokamaks? It seems that having a fourth such machine, much later than those three, would be overly redundant. ChitID 04.008 David Rasmussen 6/08/2009 17:11 Thrust 04 Regarding attributes for a "new" facility. One approach that could separate a US facility from EAST, KSTAR and JT-60 could be to push the auxiliary power density. This would imply a modest size device and a lot of investment in heating power. If it was to be ITER relevant or (alpha relevant) it would need a means to get a significant fast ion population. Power ramp up and power ramp down (to avoid disruptions) could be part of the program. ChitID 04.009 Mike Zarnstorff 6/08/2009 17:14 Thrust 04 Why does the US need to build a new facility of this sort, instead of partnering with KSTAR, EAST, or JT-60SA? If you start designing such a facility now, won't KSTAR, EAST, and JT-60SA have an insurmountable head-start by the time such a US facility was operating? ChitID 04.010 Richard Temkin 6/08/2009 21:34 Thrust 04 The talk by Ron Parker and Craig Petty presented specific advocacy for these ideas: “Ensuring that ITER will efficiently achieve its objectives requires a high level of support by the US tokamak program. This requires: In the near term, investing in the domestic tokamaks, e.g., with additional HCD and diagnostics, enabling a focused program of research addressing key ITER issues; In the longer term, constructing and operating a new US tokamak -- an ITER Satellite Facility.” This advocacy is missing from both the one pager and the six-pager. It should be in both documents. This statement also should be prominent in the write-ups: “Much of the research required for extending the pulse length on ITER, and indeed for carrying out the research outlined in this thrust, can be initiated on the existing domestic tokamaks with enhanced capabilities. As a first step, this can be accomplished by approximately doubling the ECH power on DIII-D, the NBCD power on NSTX, and the LHCD on ChitID 04.011 Richard Temkin 6/08/2009 21:39 Thrust 04 Ron Parker said in the Thrust 4 talk, under facility requirements: “As a first step, this can be accomplished by approximately doubling the ECH power on DIII-D, the NBCD power on NSTX, and the LHCD on Alcator C-Mod. This is an excellent idea. I wonder why Ron did not also advocate ECH for NSTX and for Alcator C-Mod? A major Bernstein Wave Heating program was proposed for NSTX in recent years, but not funded. I would include that. ECH for Alcator would also be interesting. ChitID 04.012 John Wesley 6/09/2009 13:01 Thrust 04 The are many connections between the normal aspects of plasma initiation, ramp-up, equilibrium burn and ramp-down and the 'alternate' evolutions associated with response to hardware and plasma abnormalities and disruption avoidance. The plasma anomalies can in turn arise from lack or limitation of control capabilities (out of actuator range, insufficient power, bad algorithm) or unforeseen plasma perturbations. In the end, an integrated cross-thrust (Super-Thrust) effort that combines scenario, actuators, control (system and algorithms) and intelligent reaction plus active-in-scenario guidance to minimize 'variance' will be needed. Not advocating combining thrusts; just mutual support. ChitID 04.013 Martin Peng 6/09/2009 14:44 Thrust 04 Various disruption loads for CTF (including its first stage scientific R&D implementation called FNSF), estimated according to the ITER physics basis for disruptions, are much smaller than those estimated for ITER. These are well documented in the IAEA FEC2008 paper FT/P3-14. The reasons for these results are obvious, that the FNSF stored plasma and magnetic energies are an order of magnitude smaller than those of ITER, over a plasma linear scale size that is 1/5 that of ITER. As a result, FNSF will unfortunately not be a good facility for testing DEMO-relevant disruption mitigation science and technology compared to ITER. It is recommended that such information be included the Thrust 13 documentation. ChitID 04.014 Richard Buttery 6/09/2009 15:47 Thrust 04 The biggest risk to ITER achieving its scenarios si the absence of NNBI and possibly viability of ICRH. Therefore add a fall back with a bullet for developing and assessing ECRH dominant scenarios, augmented by edge rotation from tangential positive ion beams. ChitID 04.015 Richard Callis 6/09/2009 17:57 Thrust 04 There is no mention in the fueling discussion if the fueling can reach the core to replace the DT burnup. Are high speed pellets or some other means of fueling needed? ChitID 04.016 Lee Berry 6/10/2009 08:48 Thrust 04 To balance issues, reliability of ECH (invessel, tubes, xmission system) and of NBI performance should be mentioned--no actions required. It should be noted that: 1. ITER, because of size, beta field is qualitatively different from present machines and is largely single pass. 2. Ill understood possibilities for flow drive are possible with ICRH. ChitID 04.017 Richard Temkin 6/22/2009 17:59 Thrust 04 Previously, the thrust said: Develop wall cleaning techniques that are compatible with high stationary toroidal magnetic fields. Investigate feasibility of tunable gyrotrons for EC cleaning. In this version, it has been changed to: Develop wall cleaning techniques that are compatible with large, stationary magnetic fields; The earlier language made sense and matched the disucssion. I would suggest as a possible option that still fits in the available space: Develop wall cleaning techniques that are compatible with large, stationary magnetic fields. Investigate feasibility of tunable gyrotrons for EC cleaning.