Induced Power Deposition Research Articles

Operational experience of a low beam coupling impedance injection kicker magnet for the CERN SPS ring

The CERN SPS injection kicker magnets (MKP) were developed in the 1970’s, before beam power deposition was considered an issue. There are two types of these magnets in the SPS: MKP-S (small aperture) and MKP-L (large aperture) versions. The MKP-L magnets are very lossy from a beam impedance perspective: this would be an issue during SPS operation with the higher intensity beams needed in the future for HL-LHC. Hence, a beam screen has been developed, which is inserted in the aperture of each MKP-L module. The screen consists of silver fingers applied to alumina U-shaped chambers: the fingers have been optimized to achieve both adequately low beam induced power deposition and good high voltage (HV) behaviour. A surface coating, with a low secondary electron yield, is applied to the inner surface of the alumina chambers to reduce dynamic vacuum. The low-impedance MKP-L has been extensively HV tested in the lab before installation in the SPS. This paper briefly presents the design and focuses on the operational experience in the SPS, including heating and vacuum.

Beam Induced Power Deposition in CERN SPS Injection Kickers

Beam Induced Power Deposition in CERN SPS Injection Kickers

Landau and collisional damping induced power deposition for the m = 0 mode of helicon and Trivelpiece–Gould waves in high density helicon plasmas

By considering the thermal and collisional effects in the analysis of power deposition properties of the helicon and Trivelpiece–Gould (TG) waves in radially uniform and high density (1 × 1013 cm−3) helicon plasmas, theoretical calculations indicate that both the electron temperature and the applied magnetic field have great effects on the wave power deposition. Detailed investigations show that for a typical helicon plasma electron temperature range, 3 eV–5 eV, power deposition due to the TG wave has a dominant role compared to that of the helicon wave for moderate to large (B0 ≥ 100 G) applied magnetic fields. Specifically, collisional damping induced TG wave power deposition dominates for the most of the electron temperature range.

Data‐Driven Experimental Evaluation Method for the Safety Assessment of Implants With Respect to RF‐Induced Heating During MRI

AbstractSmall (mm size) distal electrodes of active medical implants can cause localized radio frequency (RF)‐induced power deposition with extreme spatial gradient (5–6 dB/mm). We propose a method that aims to improve the accuracy of the traditional experimental evaluation, which relies solely on hardware instrumentation. A numerically derived local deposition distribution is used to assist the estimation of power deposition. The method was successfully validated against numerical simulations, considering three different generic implants with a single electrode. The power deposition in the surrounding region of the implant electrodes estimated with the proposed method was validated with less than 1 dB (30%) of uncertainty.

Radio frequency induced heating of an insulated wire during magnetic resonance imaging.

Radio frequency (RF) induced power deposition near straight insulated leads excited by different incident electrical field profiles was investigated. 3-D electromagnetic (EM) simulations were used to obtain implant models as well as RF-induced power depositions calculated as the integral of power loss density. For the investigated setups up to 400% discrepancy between the implant model predictions and EM simulation values was observed.

Analysis of power deposition and temperature rise due to presence of an implant inside a 1.5 t MRI RF coil.

We numerically investigated power deposition and temperature rise generated due to the presence of a titanium rod placed in a phantom, located inside a 1.5 T coil. The induced power deposition and temperature rise normalized to incident tangential electric field was found to be dependent on distance to the phantom wall. The different dependence of the integral of power deposition over a box surrounded the rod and the temperature rise on American Society for Testing and Materials (ASTM) phantom medium electrical conductivity was observed. The consequences of numerical domain simplification have been analyzed.

Verification of a hyperthermia model method using MR thermometry.

Simulation of hyperthermia induced power and temperature distributions is becoming generally accepted and finding its way into clinical hyperthermia treatments. Such simulations provide a means for understanding the complete three-dimensional temperature distribution. However, the results of the simulation studies should be regarded with caution since modelling errors will result in differences between the actual and simulated temperature distribution. This study uses a diffusion weighted magnetic resonance (MR) based technique to measure hyperthermia induced temperature distributions in a three-dimensional space in a non-perfused phantom. The measured data are used to verify the accuracy of numerical simulations of the same three-dimensional temperature distributions. The simulation algorithm is a finite element based method that first computes the electromagnetic induced power deposition then the temperature distribution. Two non-perfused phantom studies were performed and qualitatively the MR and simulated distributions agreed for steady-state. However, due to the long MR sampling time (approximately 4 min), poor agreement between the simulations and MR measurements were obtained for thermal transients. Good agreement between the simulations and fibreoptic thermometry measurements were obtained. The fiberoptic measurements differed from the simulations by 0.11 +/- 0.59 degrees C and -0.17 +/- 0.29 degrees C (mean +/- standard deviation for the two studies).