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Scattering of an alkali-metal atomic beam on anti-spin-relaxation coatings
摘要： We performed scattering experiments using a rubidium (Rb) atomic beam on paraf?n ?lms and measured the angular and velocity distributions of scattered atoms. The paraf?n ?lms were prepared in various ways and characterized by atomic force microscopy and x-ray diffraction. The ?lms exhibited various roughnesses and crystal structures. The paraf?n ?lms preserved the spin polarization of the scattered atoms. The measured angular distributions of all prepared ?lms were consistent with Knudsen’s cosine law. The velocity distributions were well ?tted by Maxwell’s distribution, characterized by a temperature much closer to the ?lm temperature than to the atomic-beam temperature. We therefore concluded that the translational motion of the scattered atoms was thermalized with the paraf?n ?lms via single-scattering events.
关键词： Knudsen’s cosine law,velocity distributions,scattering experiments,paraf?n ?lms,Maxwell’s distribution,rubidium atomic beam,spin polarization,angular distributions
更新于2025-09-23 15:21:01
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - W-Band True-Time Delay Phase Shifters Using Paraffin Microactuators
摘要： We report a distributed loaded line phase shifter based on a new class of electro-thermally actuated RF MEMS devices using paraf?n phase-change material (PCM). Paraf?n is a low loss (tan δ = 6.6×10?4) mechanical phase-change material that exhibits a 15% volumetric change through its solid-liquid transition. Due to its unique electrical and mechanical properties, paraf?n PCM variable capacitors exhibit a very low loss which is critical in designing recon?gurable structures. Here, a low-loss paraf?n PCM based true-time delay, continuously-tunable phase shifter is designed and optimized. A ?gure-of merit of 71.8?/dB is achieved while maintaining a return loss more than 12 dB. Designed phase shifter has a maximum insertion loss of 5 dB for a 360? phase shift. Electro-thermo-mechanical performance of the paraf?n PCM device is studied by carrying out a fully coupled multiphysics simulation. Maximum displacement of 0.8 μm is achieved with a 2.6 μm-thick paraf?n ?lm. A new fabrication method for the deposition of the thin paraf?n ?lm is developed and a fabrication process for the device is presented.
关键词： MEMS,phase shifter,phase-change material,DMTL,paraf?n,millimeter wave
更新于2025-09-04 15:30:14