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Register a new userMeasurement of Radio-Frequency Radiation Pressure
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Added by
Christopher Holloway
Publication date
2018
fields
Physics
and research's language is
English
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We perform measurements of the radiation pressure of a radio-frequency (RF) electromagnetic field which may lead to a new SI-traceable power calibration. There are several groups around the world investigating methods to perform more direct SI traceable measurement of RF power (where RF is defined to range from 100s of MHz to THz). A measurement of radiation pressure offers the possibility for a power measure traceable to the kilogram and to Plancks constant through the redefined SI. Towards this goal, we demonstrate the ability to measure the radiation pressure/force carried in a field at 15~GHz.
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High pressure Nuclear Magnetic Resonance (NMR) is known to uncover behavior of matter at extreme conditions. However, significant maintenance demands, space requirements and high costs of superconducting magnets render its application unfeasible for regular modern high pressure laboratories. Here, we present a table-top NMR system based on permanent Halbach magnet arrays with dimensions of 25 cm diameter and 4 cm height. At the highest field of 1013 mT, 1H-NMR spectra of Ice VII have been recorded at 25 GPa and ambient temperature. The table-top NMR system can be used together with double sided laser heating set-ups. Feasibility of high-pressure high-temperature NMR was demonstrated by collecting 1H-NMR spectra of H2O at 25 GPa and 1063(50) K. We found that the change in signal intensity in laser-heated NMR diamond anvil cell yields a convenient way for temperature measurements.
While Atomic Force Microscopy is mostly used to investigate surface properties, people have almost since its invention sought to apply its high resolution capability to image also structures buried within samples. One of the earliest techniques for this was based on using ultrasound excitations to visualize local differences in effective tip-sample stiffness caused by the presence of buried structures with different visco-elasticity from their surroundings. While the use of ultrasound has often triggered discussions on the contribution of diffraction or scattering of acoustic waves in visualizing buried structures, no conclusive papers on this topic have been published. Here we demonstrate and discuss how such acoustical effects can be unambiguously recognized and can be used with Atomic Force Microscopy to visualize deeply buried structures.
Ions confined using a Paul trap require a stable, high voltage and low noise radio frequency (RF) potential. We present a guide for the design and construction of a helical coil resonator for a desired frequency that maximises the quality factor for a set of experimental constraints. We provide an in-depth analysis of the system formed from a shielded helical coil and an ion trap by treating the system as a lumped element model. This allows us to predict the resonant frequency and quality factor in terms of the physical parameters of the resonator and the properties of the ion trap. We also compare theoretical predictions with experimental data for different resonators, and predict the voltage applied to the ion trap as a function of the Q-factor, input power and the properties of the resonant circuit.
Within the framework of the European, project MYRTE (MYRRHA Research and Transmutation Endeavour) of the H2020 program, a 4-Rods RFQ (Radio Frequency Quadrupole) has been designed at 176.1 MHz RFQ for accelerating up to 4 mA protons in CW (Continuous Wave) operation from 30 keV up to 1.5 MeV. A LLRF prototype has been developed to regulate the amplitude and the phase of the accelerator field into the RFQ and the frequency of the RFQ controlling the motor of the frequency tuner. The facility at Louvain-La-Neuve will be presented with a focus on the LLRF system used and some preliminary results.
This paper gives a brief overview of the general principles of radiation protection legislation; explains radiological quantities and units, including some basic facts about radioactivity and the biological effects of radiation; and gives an overview of the classification of radiological areas at CERN, radiation fields at high-energy accelerators, and the radiation monitoring system used at CERN. A short section addresses the ALARA approach used at CERN.
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