Effect Of Pulsed Heating Research Articles

Features of thermal processes and the influence of pulsed heating of surface layers of titanium on the diffusion transfer of dopants during high-intensity ion implantation

Methods for modification of surface and near-surface layers of materials and coatings by ion beamshave prospects for application in many fields of science and technology. The method of high-intensityimplantation by high-power density ion beams with submillisecond duration involves significantpulsed heating of the irradiated target’s surface layer, followed by its rapid cooling due to heatremoval into the material due to thermal conductivity and the implementation of repetitively-pulsedradiation-enhanced diffusion of atoms to depths significantly exceeding the projective ion range. Thispaper considers features of thermal processes and the effect of pulsed heating of near-surface titaniumlayers on diffusion transfer under conditions of synergy of high-intensity titanium ion implantationand energy impact of a high-power density repetitively-pulsed beam on the surface to increase iondoping depth due to radiation-enhanced diffusion under conditions of limited heating of the entiresample. The paper presents the data of numerical simulation of dynamic changes in temperature fieldsin titanium and titanium self-diffusion under the action of ion beams with a submillisecond durationand a pulse power of tens of kW/cm2 and fluence of ions in a pulse 1.25×1015 ion/cm2.

Effects of Pulsed Radiofrequency Source on Cardiac Ablation.

Heart arrhythmia is caused by abnormal electrical conduction through the myocardium, which in some cases, can be treated with heat. One of the challenges is to reduce temperature peaks-by still guaranteeing an efficient treatment where desired-to avoid any healthy tissue damage or any electrical issues within the device employed. A solution might be employing pulsed heat, in which thermal dose is given to the tissue with a variation in time. In this work, pulsed heat is used to modulate induced temperature fields during radiofrequency cardiac ablation. A three-dimensional model of the myocardium, catheter and blood flow is developed. Porous media, heat conduction and Navier-Stokes equations are, respectively, employed for each of the investigated domains. For the electric field, solved via Laplace equation, it is assumed that the electrode is at a fixed voltage. Pulsed heating effects are considered with a cosine time-variable pulsed function for the fixed voltage by constraining the product between this variable and time. Different dimensionless frequencies are considered and applied for different blood flow velocity and sustained voltages. Results are presented for different pulsed conditions to establish if a reasonable ablation zone, known from the obtained temperature profiles, can be obtained without any undesired temperature peaks.

Pulsed Magnetization of a Short-Circuited HTSC Coil

We have studied trapped magnetic fields and their relaxation during pulsed magnetization of a 20-turn short-circuited coil made of a stabilized HTSC-2G tape at liquid nitrogen temperature. The highest trapped field is close to the value obtained during field cooling (FC process) and varies insignificantly upon a five-fold increase of the magnetizing pulse amplitude. Copper coating of the tape considerably suppresses pulsed heating effects. Current relaxation at the initial segment is determined by the current passing between superconducting and normal layers and by the form of the current–voltage characteristic. Over long time intervals (t > 100 s), relaxation is determined by the contact resistance of the soldered junction.

Color centers in NaCl single crystals induced by pulsed intense relativistic electron beams to simulate radiation bursts in Europa

To simulate the burst irradiation environment of Europa, single crystals of NaCl were irradiated by pulsed intense relativistic electron beams (PIREBs) with a peak energy of 6 MeV, a current of −800 A, and a pulse width of 70 ns. After irradiation, the optical absorption of the samples was measured, and results indicated that the irradiation induced F- and F2-centers. The density of F-centers was estimated to be 8.9 × 1016 cm−3 from 1 shot of PIREB irradiation with 6 MeV. The absorbed energy to form F-centers by PIREB was comparable but slightly higher than those induced by conventional direct current accelerators. The effect of pulsed heating, which should be taken into account for the detection of NaCl on Europa, is discussed.

Импульсное намагничивание короткозамкнутой катушки из ВТСП

In this paper is described the pulsed magnetization of a 20-turn short-circuited coil from a stabilized HTSC-2G tape. The trapped field in the coil is close to the value obtained at the field cooling (FC) process and varies only slightly with a 5-fold increase in the amplitude of the magnetizing pulse. The copper coating of the tape significantly reduces the effects of pulsed heating. The relaxation of the current in the initial stage is determined by the flow of current between the superconducting and normal layer and the type of the current-voltage characteristic. At large times (t> 100 s), attenuation is determined by the contact resistance of the junction.

Performance limiting effects inX-band accelerators

Acceleration gradient is a critical parameter for the design of future TeV-scale linear colliders. The major obstacle to higher gradient in room-temperature accelerators is rf breakdown, which is still a very mysterious phenomenon that depends on the geometry and material of the accelerator as well as the input power and operating frequency. Pulsed heating has been associated with breakdown for many years; however, there have been no experiments that clearly separate field and heating effects on the breakdown rate. Recently, such experiments have been performed at SLAC with both standing-wave and traveling-wave structures. These experiments have demonstrated that pulsed heating is limiting the gradient. Nevertheless the $X$-band structures breakdown studies show damage to the iris surfaces in locations of high electric field rather than of high magnetic field after thousands of breakdowns. It is not yet clear how the relative roles of electric field, magnetic field, and heating factor into the damage caused by rf breakdown. Thus, a dual-moded cavity has been designed to better study the electric field, magnetic field, and pulsed heating effects on breakdown damage.

Laser mass spectrometric detection of extraterrestrial aromatic molecules: Mini-review and examination of pulsed heating effects

Laser mass spectrometry is a powerful tool for the sensitive, selective, and spatially resolved analysis of organic compounds in extraterrestrial materials. Using microprobe two-step laser mass spectrometry (muL(2)MS), we have explored the organic composition of many different exogenous materials, including meteorites, interplanetary dust particles, and interstellar ice analogs, gaining significant insight into the nature of extraterrestrial materials. Recently, we applied muL(2)MS to analyze the effect of heating caused by hypervelocity particle capture in aerogel, which was used on the NASA Stardust Mission to capture comet particles. We show that this material exhibits complex organic molecules upon sudden heating. Similar pulsed heating of carbonaceous materials is shown to produce an artifactual fullerene signal. We review the use of muL(2)MS to investigate extraterrestrial materials, and we discuss its recent application to characterize the effect of pulsed heating on samples of interest.

Effect of Pulsed Heating of the Active Region of an Injection Laser on the Dynamics of Storage of a Pulse Information Sequence in an Electrooptical Recirculation Circuit

With account for the effect of a residual charge, a theoretical analysis is carried out of the effect of pulsed heating of the active region of an injection laser on the dynamics of storage of a pulse information sequence in a closed electrooptical circuit consisting of an injection laser, a fiber‐optic light guide, and a regenerator based on a threshold shaper. Results on the time of storage of information in the circuit for different kinds of storage devices are obtained.

Characterization of pressure pulse and carrier gas flow changes resulting from pulsed heating in ETV-ICP-MS

A simplistic model was formulated to show the effects of pulsed heating upon a flow of gas through an ETV. Using this model, a significant change in flow was predicted with a profile that increased sharply during the initial stages of heating, but then tapered off. Experimentally, pressure and flow increases were shown to be coincident to the pulsed heating of an ETV, by using both a direct and an indirect method of determination. Direct measurement of both pressure and flow increases were acquired through the use of a probe that contained pressure, flow and temperature sensors. An indirect measurement of the pressure/flow pulse was obtained by monitoring the Ar2+, which is sensitive to the carrier gas flow rate. The pressure increase was determined to be minimal ( 100 ml min−1). The magnitudes of both pressure and flow increases were determined to be dependent upon the initial carrier gas flow rates. Due to the envisioned deleterious effects of the pressure/flow pulse, an attempt was made to separate the arrival of the pulse at the plasma from the analyte signal by lengthening the transport tubing. In this manner, it was determined that the analyte signal traveled at a velocity which was much less than that of the pressure pulse which propagates at the speed of sound in Ar. However, increased transport tubing lengths resulted in lower sensitivities and no significant gain in precision.