The KATRIN experiment is a next-generation direct neutrino mass experiment with a sensitivity of 0.2 eV (90% C.L.) to the effective mass of the electron neutrino. It measures the tritium β-decay spectrum close to its endpoint with a spectrometer based on the MAC-E filter technique. The β-decay electrons are guided by a magnetic field that operates in the mT range in the central spectrometer volume; it is fine-tuned by a large-volume air coil system surrounding the spectrometer vessel. The purpose of the system is to provide optimal transmission properties for signal electrons and to achieve efficient magnetic shielding against background. In this paper
JINST 13 P02003we describe the technical design of the air coil system, including its mechanical and electrical properties. We outline the importance of its versatile operation modes in background investigation and suppression techniques. We compare magnetic field measurements in the inner spectrometer volume during system commissioning with corresponding simulations, which allows to verify the system's functionality in fine-tuning the magnetic field configuration. This is of major importance for a successful neutrino mass measurement at KATRIN.
Robot-assisted minimally invasive surgery generally prevents the use of an important diagnostic tool in medicine: palpation. There are various approaches to reestablish the haptic feedback for the surgeon, including tactile displays and haptic input devices. We present a novel haptic display that features seven pins mounted on compression springs that can be pre-loaded with servo motors. Each pin has a stroke of 10 mm and a maximum counterforce of 1.1 N. An additional force of 0.7 N per pin can be applied with the motors. This technique allows for simultaneous stimulation of kinesthetic as well as tactile perception. The control of the haptic display has been implemented in the open-source haptics library CHAI 3D. We extended the framework with a multi interaction point tool to represent the hardware. This eventually lead to a palpation training program where bodies with multiple adjustable parameters encapsulated in a virtual soft tissue can be simulated. We evaluated this software in a user study with 15 participants in order to demonstrate the usability of the haptic display. With 90 % of successful hits, we are confident that sensible haptic feedback can be generated with the presented device. Furthermore, we are currently extending the scope of the haptic display to make use of a novel capacitive tactile proximity sensor in exploration scenarios.
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