Swirl Tube Research Articles

Burnout experiments on the externally-finned swirl tube for steady-state and high-heat flux beam stops

An experimental study to develop beam stops for the next generation of neutral beam injectors was started, using an ion source developed for the JT-60 neutral beam injector. A swirl tube is one of the most promising candidates for a beam stop element which can handle steady-state and high-heat flux beams. In the present experiments, a modified swirl tube, namely an externally-finned swirl tube, was tested together with a simple smooth tube, an externally finned tube, and an internally finned tube. The major dimensions of the tubes are 10 mm in outer-diameter, 1.5 mm in wall thickness, 15 mm in external fin width, and 700 mm in length. The burnout heat flux (CHF) normal to the externally finned swirl tube was 4.1 ± 0.1 kW/cm 2 , where the Gaussian e-folding half-width of the beam intensity distribution was about 90 mm, the flow rate of the cooling water was 30 l/min, inlet and outlet gauge pressures were about 1 MPa and 0.2 MPa, respectively, and the temperature of the inlet water was kept to 20 °C during a pulse. A burnout heat flux ratio, which is defined by the ratio of the CHF value of the externally-finned swirl tube to that of the externally-finned tube, turned out to be about 1.5. Burnout heat fluxes of the tubes with a swirl tape or internal fins increase linearly with an increase of the flow rate. It was found that the tube with external fins has effects that not only reduce the thermal stress but also improve the characteristics of boiling heat transfer.

Compact, inexpensive target design for steady-state heat removal in high-heat-flux fusion applications

A high-heat-flux target has been developed for intercepting multimegawatt, multisecond neutral beams at Oak Ridge National Laboratory (ORNL). Water-cooled copper swirl tubes are used for the heat transfer medium; these tubes exhibit an enhancement in burnout heat flux over conventional axial flow tubes. The target consists of 126 swirl tubes [each 0.95 cm in outside diameter (o.d.) with 0.16-cm-thick walls and ≊1 m long] arranged in a V shape and inclined with respect to the beam axis. In tests with the ORNL long-pulse ion source (13×43-cm grid), the target has handled up to 3-MW, 30-s beam pulses with no deleterious effects. The peak power density was estimated at ≊15 kW/cm2 normal to the beam axis (>5 kW/cm2 maximum on tube surfaces). The water flow rate through the tubes was 0.33 l/s (5.2 gal/min) per tube (axial flow velocity=11.6 m/s) with a corresponding pressure drop of 1.14 MPa (165 psi). To date, the target has absorbed an estimated 25 000 full-power (≊3 MW) pulses for a cumulative time of ≊100 000 beam seconds without failure. Other potential applications for swirl tube technology in the fusion area include plasma limiters, divertor collector plates, rf launchers, and Faraday shields.

Erosion Tests of Materials by Energetic Particle Beams

The internal components of magnetic fusion devices must withstand erosion from and high heat flux of energetic plasma particles. The selection of materials for the construction of these components is important to minimize contamination of the plasma. In order to study various materials' comparative resistance to erosion by energetic particles and their ability to withstand high heat flux, water-cooled copper swirl tubes coated or armored with various materials were subjected to bombardment by hydrogen and helium particle beams. Materials tested were graphite, titanium carbide (TiC), chromium, nickel, copper, silver, gold, and aluminum. Details of the experimental arrangement and methods of application or attachment of the materials to the copper swirl tubes are presented. Results including survivability and mass losses are discussed.

The split tube and lock, and swirl tube attachments

T HE treatment of malocclusion consists of changing the abnormal relationships of the teeth and the jaws to a normal relationship. A change in relationship implies a change in position, and a change in position represents motion. Motion can be imparted to a body at rest by the application of a force; accordingly, the teeth which are at rest in relation to the supporting structures can be made to move by exerting controlled pressures upon them. These controlled pressures, or applied forces, may be of several different characters. The various mechanical devices in use at the present time apply forces to the teeth in different manners, and thus bring about different kinds of tooth movements. The recognition of the various kinds of tooth movements induced by these mechanical devices is very important, for the intelligent selection of a working appliance depends upon a full understanding of appliance action. Thus, it is made clear that the selection of an appliance is governed entirely by the required tooth movements. It has never been pointed out that there is an inherent tendency on the part of the teeth to move into normal positions. While this does not always take place, this tendency is clearly recognizable in all instances. Malocclusions are the result of the failure of the teeth to move into normal positions. The development of 6he specialty of orthodontics may be traced directly to this characteristic tendency of the teeth to align themselves properly. The early orthodontic appliances depended almost entirely upon this tendency. The plain labial appliance is a final expression of these earlier attempts, and its successful operation depends upon the ability of the teeth to move into normal positions. It is possible to bring about all the required tooth movements by the plain labial appliance, such as buccal or labial, lingual and mesiodistal tipping movements, bodily movements, root movements and rotations; but many of these changes cannot be explained on a mechanical basis and cannot be directly attrihut,ed to the appliance. As a result of this characteristic property of the teeth, a very large number of cases can be successfully treated by the plain labial arches, and with little effort almost all movements may be effectively produced. There are a number of instances, however, where the plain labial appliance proves to be inadequate. The inefficiency of the appliance and the lack of force control become apparent, and other devices must be resorted to in order to attain a desirable result.