Abstract
The RF-driven negative ion source testbed BATMAN upgrade is being developed at IPP Garching in the framework of the ion source development for ITER and DEMO neutral beam injection systems. The testbed has recently been enhanced to allow for steady state operation with a focus on beam optics studies. The previous titanium sublimation pumps and inertial calorimeter limited the beam pulse length to about 6s every 3min. The upgrade comprises a long-pulse compatible, actively cooled diagnostic calorimeter. This has been designed and is currently being manufactured to substitute the inertially cooled calorimeter that has limited diagnostic capabilities. The new diagnostic calorimeter consists of a copper plate with dimensions of 910 × 660 × 25mm3 placed about 2m from the ion source extraction grids, and through a novel solution, it will provide a 2D profile of beam power density with a 20mm spatial resolution. Water flowing through cooling channels embedded in the copper plate will actively cool the calorimeter, which is loaded with about 160 kW beam power at ITER-relevant current density, but 45 kV acceleration. A fraction of the beam will pass through many small apertures (ø2mm) positioned in the calorimeter plate and will be collected by thin (0.2mm) copper foils attached to the calorimeter back side. Evaluation of power density will be performed by measuring the temperature of the heat flux foils with a high-resolution infrared camera observing the calorimeter from the back side and calibrated by thermocouples.
Highlights
The international fusion experiment ITER will be equipped with two Neutral Beam Injectors (NBIs) with a total power of 33 MW for plasma heating and current drive.1 The ITER NBIs incorporate radio frequency (RF)-driven ion sources that are required to deliver 46 A of H− current for up to 1000 s and 40 A of D− for up to 3600 s
A fraction of the beam will pass through many small apertures (ø2 mm) positioned in the calorimeter plate and will be collected by thin (0.2 mm) copper foils attached to the calorimeter back side
Beam pulse duration up to 1 hour is going to be possible at BATMAN Upgrade thanks to a new cryo-pump, which has recently been installed in the testbed, and a new long-pulse diagnostic calorimeter, which is currently being manufactured
Summary
The international fusion experiment ITER will be equipped with two Neutral Beam Injectors (NBIs) with a total power of 33 MW for plasma heating and current drive. The ITER NBIs incorporate radio frequency (RF)-driven ion sources that are required to deliver 46 A of H− current for up to 1000 s and 40 A of D− for up to 3600 s. An extraction voltage Uex of up to 15 kV can be applied, while the total maximum voltage UHV is 45 kV These operational parameters grant considerably improved beam optics with respect to the previous BATMAN testbed: the typical beam divergence has been reduced from 3○ to 4○ in BATMAN to 1○–2○ in BUG, but still not below 7 mrad (≈0.4○) as required for ITER. Beam pulse duration up to 1 hour is going to be possible at BATMAN Upgrade thanks to a new cryo-pump, which has recently been installed in the testbed, and a new long-pulse diagnostic calorimeter, which is currently being manufactured. This paper describes the novel design solutions, simulations, and manufacturing of the new long pulse diagnostic calorimeter for BATMAN Upgrade
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