NSTX Team Meeting August 9, 2011 NSTX TF Update Team Meeting August 9, 2011 Culham Sci Ctr U St. Andrews York U Chubu U Fukui U Hiroshima U Hyogo U Kyoto U Kyushu U Kyushu Tokai U NIFS Niigata U U Tokyo JAEA Hebrew U Ioffe Inst RRC Kurchatov Inst TRINITI NFRI KAIST POSTECH ASIPP ENEA, Frascati CEA, Cadarache IPP, Jülich IPP, Garching ASCR, Czech Rep Columbia U CompX General Atomics FIU INL Johns Hopkins U LANL LLNL Lodestar MIT Nova Photonics New York U ORNL PPPL Princeton U Purdue U SNL Think Tank, Inc. UC Davis UC Irvine UCLA UCSD U Colorado U Illinois U Maryland U Rochester U Washington U Wisconsin NSTX Supported by

NSTX Team Meeting August 9, Time: 1:00 ~ 2:30, August 9, 2011 Place: LSB 318, PPPL TF Update (40 minutes) Engineering Operations Update (10 minutes) Research Operations Update (10 minutes) Project / Program Items (30 minutes) NSTX Team Meeting Agenda

NSTX Team Meeting August 9, TF Bundle Lifted Without Breaking High Vacuum July 25 - Disassembled lower TF hub for further examination July 26 – Decided to remove TF bundle out for better examination and formulation of repair strategy July 28 – TF bundle lifted out of NSTX in to the stand in the South High bay area without disturbing high vacuum. August 1 – Present focus is to pinpoint the shorted location by electrical and borescopic measurements No additional visible damages observed on the inner TF bundle

NSTX Team Meeting August 9, 2011 TF Bundle Placed in Its Stand on July 28 The NSTX TF center bundle was removed and placed in its stand in the south high bay area. Cleaning and inspections are in progress so we can develop a repair plan. E. Perry

NSTX Team Meeting August 9, 2011 Damaged TF Area (7/29/2011) The damaged TF area after the TF bundle is placed in the stand. The blackened lead is the TF #13. The short appears to be internal. TF Bundle Before Installed on NSTX

NSTX Team Meeting August 9, 2011 Inner TF Bundle Turn Designation NORTH ~ 1 Ω short among TF #30, TF # 13 and TF # 14 Maximum voltage can be minimized for the affected turns by clocking TF Maximum voltage drop ~ difference in the # times 30V TF is connected to a 1 kV supply. ~ 500 V can be applied between #30 and #13 but only ~ 30 V between # 13 and #14.

NSTX Team Meeting August 9, 2011 Inner TF Bundle Electrical Test Indicates a Short at ~ 2 Feet From the Bottom

NSTX Team Meeting August 9, 2011 TF Bundle Short Located by Electrical Measurement: –Electrical short involving TF # 13, 14 and 30 located ~ 2 feet from the bottom. –Borescope measurement being performed to internally examine the location of the short – melted solder must be removed. –The location is where the general stress level is relatively low. PF 1A and PF 1B effect being investigated TF Bundle Electrical Short Location

NSTX Team Meeting August 9, 2011 The location of the short (2 feet up from the joint) preclude a possibility of quick repair: –The shorted TF bars will need to be repaired. –The bar will need to be removed from the bundle. –Spare conductor bars were located which would give us some additional options such as preparing the replacement bars in parallel with the TF short investigation and the damaged conductor removal. An external team of experts will be invited to advise on the TF fault and the TF Upgrade Design once sufficient information is gathered. If the TF repair is determined to take too long, we may revise our upgrade strategy. –The upgraded TF design to reflect what we learned best we can. –By starting the outage early, we maybe able to start up the upgraded machine that much sooner in FY The TF Repair Will Not Be Quick

NSTX Team Meeting August 9, 2011 –TF conductor length increases ~ 0.6 cm during the pulse due to the temperature rise from ~ 12 °C to ~ 80°C. –If we take out turns, those turns would not grow causing the sheering force between them and the conducting turns resulting in possible turn-to-turn insulation failure. –It is also not clear what can be gained from the de-rated operation (lower and shorter TF pulses). –If we put back the TF bundle as is and operate it, this has its own risks and it also prevents further examination of the bundle. Should we run with de-rated TF? It is not easy.

NSTX Team Meeting August 9, 2011 We will look for options to repair the TF coil while investigating the cause of fault. –We need to find the cause and if possible repair the coil as soon as possible. –We also need to take advantage of this down time to make as much progress as possible on the Upgrade Project. NSTX Research Team: –Complete whatever you need to do on the machine such as commissioning etc. –Please take your long over due vacations! –Continue analyzing data for publications and meetings assuming no new data (e.g., APS) NSTX Engineering Team: –TF failure diagnose and repair will be pursued at highest priority. –Machine will be kept under high vacuum for the time being. –Tasks which benefit the Upgrade Project get high priority. Let us make the best of the situation

NSTX Team Meeting August 9, 2011 OH/TF Manufacturing Area The Inner TF/ OH fabrication will occur at PPPL in the CS High Bay area (Former NCSX Test Cell) Crane capacity (45 T), environmental control and adequate work space 12 Setup for Inner TF Bundle

NSTX Team Meeting August 9, 2011 Present TF bundle (Diameter is ~ ½ of the Upgrade TF) Upgraded TF bundle Upgraded TF Have Much Improved Design Complicated two layer design Complicated cooling water path 3/16” refrigeration cooling tube B-stage insulation Identical simple conductors Simple straight cooling water path 3/8” K-type straight copper tube More robust VPI insulation

NSTX Team Meeting August 9, ES&H Issues (J. Levine) Even though we are now in a stand-by mode, your safety is still highly important wherever you maybe. Have fun vacationing but please keep the safety in mind for you and your family. We just had a tragic bicycle accident of our dear colleague who had decades of riding experience. Safely, Safely, Safely