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The National Compact Stellarator Experiment (NCSX) was designed to test a compact, quasiaxisymmetric stellarator configuration. Flexibility and accurate realization of its complex 3D geometry were key requirements affecting the design and construction. While the project was terminated before completing construction, there were significant engineering accomplishments in design, fabrication, and assembly. The design of the stellarator core device was completed. All of the modular coils, toroidal field coils, and vacuum vessel sectors were fabricated. Critical assembly steps were demonstrated. Engineering advances were made in the application of CAD modeling, structural analysis, and accurate fabrication of complex-shaped components and subassemblies. The engineering accomplishments of the project are summarized

Photogrammetry, a state-of-the-art technique of metrology employing digital photographs as the vehicle for measurement, has been investigated in the fusion environment. Benefits of this high tolerance methodology include relatively easy deployment for multiple point measurements and deformation/distortion studies. Depending on the equipment used, photogrammetric systems can reach tolerances of 25 microns (0.001 in) to 100 microns (0.004 in) on a 3-meter object. During the fabrication and assembly of the National Compact Stellarator Experiment (NCSX) the primary measurement systems deployed were CAD coordinate-based computer metrology equipment and supporting algorithms such as both interferometer-aided (IFM) and absolute distance measurementbased (ADM) laser trackers, as well as portable Coordinate Measurement Machine (CMM) arms. Photogrammetry was employed at NCSX as a quick and easy tool to monitor coil distortions incurred during welding operations of the machine assembly process and as a way to reduce assembly downtime for metrology processes. This paper will explore the use of photogrammetry on NCSX during field period assembly (FPA) and the results it achieved. It will also explore other applications of this method and discuss future plans for use.

It has been shown that post detonation energetic helium ions can drastically reduce the useful life of the (dry) first wall of an IFE reactor due to the accumulation of implanted helium. For the purpose of attenuating energetic helium ions from interacting with first wall components in the Fusion Test Facility (FTF) target chamber, several concepts have been advanced. These include magnetic intervention (MI), deployment of a dynamically moving first wall, use of a sacrificial shroud, designing the target chamber large enough to mitigate the damage caused by He ions on the target chamber wall, and the use of a low pressure noble gas resident in the target chamber during pulse power operations. It is proposed that employing a low-pressure (∼ 1 torr equivalent) noble gas in the target chamber will thermalize energetic helium ions prior to interaction with the wall. The principle benefit of this concept is the simplicity of the design and the utilization of (modified) existing technologies for pumping and processing the noble ambient gas. Although the gas load in the system would be increased over other proposed methods, the use of a “gas shield” may provide a cost effective method of greatly extending the first wall of the target chamber. An engineering study has been initiated to investigate conceptual engineering methods for implementing a viable gas shield strategy in the FTF.

In support of the National Compact Stellerator Experiment (NCSX), stellerator assembly activities continued this past year at the Princeton Plasma Physics Laboratory (PPPL) in partnership with the Oak Ridge National Laboratory (ORNL). The construction program saw the completion of the first two Half Field-Period Assemblies (HPA), each consisting of three modular coils. The full machine includes six such sub-assemblies. A single HPA consists of three of the NCSX modular coils wound and assembled at PPPL. These geometrically-complex three-dimensional coils were wound using computer-aided metrology and CAD models to tolerances within +/−- 0.5mm. The assembly of these coils required similar accuracy on a larger scale with the added complexity of more individual parts and fewer degrees of freedom for correction. Several new potential positioning issues developed for which measurement and control techniques were developed. To accomplish this, CAD coordinate-based computer metrology equipment and software similar to the solutions employed for winding the modular coils was used. Given the size of the assemblies, the primary tools were both interferometeraided and Absolute Distance Measurement (ADM)-only based laser trackers. In addition, portable Coordinate Measurement Machine (CMM) arms and some novel indirect measurement techniques were employed. This paper will detail both the use of CAD coordinate-based metrology technology and the techniques developed and employed for dimensional control of NSCX sub-assemblies. The results achieved and possible improvements to techniques will be discussed.

A conceptual design has been developed for the recovery of un-expended fuel, ash, and associated post-detonation products from a ~ 2 GW IFE power reactor. The conceptual design incorporates systems for the safe, efficient collection, processing, and purification of IFE plasma exhaust fuel components. The system has been designed and sized such that tritium bred within blankets can also be collected, processed, and introduced into the fuel cycle. The system is nominally sized to process ~2 kg of tritium per day and is designed to link directly to the target chamber mechanical pumping system. The plasma exhaust can be directly processed from the exhaust of the vacuum pumping system or can be processed in batch mode from buffer vessels in the receiving and analysis system (RAS). Systems for the accurate measurement of material in-process (MIP) have been included. Design emphasis is on safety, reliability, redundancy, and efficiency in order to maximize availability. The primary goal of the fuel recovery system (FRS) design is to economically recycle components of IFE fuel back to the target manufacturers in a fashion by which fuel components are rapidly made available for re-use thus lowering the total active inventory. The FRS design is presented as a facility sub-system in the context of supporting the safe and efficient operation of the IFE target chamber.

A conceptual design for a magnetic intervention system is presented in support of a 2 GW IFE direct drive fusion power reactor. The system is designed employing a cusp field to deflect ions generated by an IFE implosion away from the first wall of the reactor core and into specifically designed ion dumps. The magnetic coil system will employ liquid helium cooled 5083 Aluminum alloy casing on a Rutherford NbTi cable. The cables are configured as four double pancakes with a 5083 Aluminum alloy case for structural support. The conceptual design and corresponding preliminary load and field calculations will be presented.

The possibility of utilizing magnetic intervention (MI) in a laser-driven inertial fusion energy (IFE) dry wall chamber is being considered to steer away the ions from the chamber wall to more readily accessible and replaceable dump regions at the equator and poles. This paper summarizes the current status of this study, describing the overall MI chamber core configuration and layout and highlighting the key design and analysis results for the different components.

The NSTX high-k scattering diagnostic measures small-scale density fluctuations by the heterodyne detection of waves scattered from a millimeter wave probe beam at 280 GHz and lambda=1.07 mm. To enable this measurement, major alterations were made to the NSTX vacuum vessel and neutral beam armor. Close collaboration between the PPPL physics and engineering staff resulted in a flexible system with steerable launch and detection optics that can position the scattering volume either near the magnetic axis (rhoap.1) or near the edge (rhoap.8). 150 feet of carefully aligned corrugated waveguide was installed for injection of the probe beam and collection of the scattered signal into the detection electronics

A silicon membrane windows is developed for a KrF laser system. The main function of the windows is to pass electron beam into the laser cell and to hold pressurized gas in the cell. 150 micro-meter thick silicon windows successfully survived from heated electron beam bombardment and shows 80% of electron beam transmission rate. The single silicon windows endured 250,000 cycles of electron beam shots. The arrayed windows did not show sufficient performance due to excessive heat generation. To enhance the longevity, the cooling system has to be improved and a study of the arc generated by the cathode is necessary