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The development of periodic structures for use as oscillators and amplifiers in the millimetre and sub-millimetre region has been an important topic in science in recent years [1–4]. The 2D periodic structure used in this instance to form the interaction region has a potential for application in sources of high power microwave and THz radiation [5]. Such a structure can be observed using a hollow,...
The axis of symmetry of the magnetic field is not always ideally aligned to the mechanical axis of the gyrotron, mainly for two reasons: (i) misalignment of the coils in the magnet and (ii) mechanical inaccuracies on the gun and cavity position. In this work, the effects of the magnetic field misalignment are numerically studied for the coaxial cavity EU gyrotron1 for ITER. First, the degradation...
At present, gyrotron oscillators, as sources of high power millimeter waves, play a central role in fusion energy research. Recently, spurious oscillations in high power gyrotrons gained attention as an influencing factor on the overall efficiency: in the up-taper/launcher section, a region exists where the decreasing magnetic field is alleged to excite spurious oscillations1. Numerical investigations...
Coaxial gyrotrons offer the potential to generate microwave power in the multi-megawatt levels at frequencies well above 100 GHz1, since very high-order volume modes can be used. The presence of the coaxial insert reduces the voltage depression and eliminates the restrictions of mode selectivity, making it possible to maintain the cavity ohmic losses at a reasonable low level (<2kW/cm2) allowing...
As is known, the operating magnetic fields in gyrotrons can be significantly decreased by using high-cyclotron-harmonic radiation of an axis-encircling electron beam. This configuration of so-called Large Orbit Gyrotron (LOG) improves both the electron-wave coupling and mode selectivity. Recently, a unique third-harmonic 1 THz/80 kV LOG has been realized at the IAP [1]. It should be noticed that because...
Gyrotrons find use in several diverse fields, ranging from plasma heating and plasma diagnostic to spectroscopy and materials processing. However, with demand for high power coherent radiation at THz frequencies, the confining magnetic fields required for gyrotrons operating at the fundamental harmonic become increasingly restrictive. However, considerable promise lies with the concept of the gyro-multiplier...
A commonly used laser-based method of acceleration of dense plasma, particularly applied for compression and ignition of a fusion target in ICF research, is ablative acceleration (AA) employing the “rocket effect ”. However, the energetic efficiency of acceleration in the AA scheme is relatively small (≤10%), so significant efforts have been made to find more efficient schemes. Very recently, a novel...
A nuclear explosion in the upper atmosphere generate a cavity filled with radioactive plasma of high conductivity, from this superseded the geomagnetic field. Hundredths of a second cavity is filled with relativistic beta-electrons. The flux density of beta-electrons in the cavity jβ (1/sm2.s) is determined by its activity, the size of the cavity and the cavity flow coming out of beta-electrons. The...
The International Linear Collider (ILC) requires a 1.3 GHz RF source with a minimum efficiency of 65% at 10 MW output power, and a cathode current density of less than 5 A/cm2. In addition, the source must be compatible with a pulse width of 1.5 milliseconds at a repetition rate of 15 Hz. Present source development is centered on multiple beam (MBK) and sheet beam (SBK) klystrons. These devices are...
One of the on-going research programs, at the University of Strathclyde, involves the development of high-power, pulsed, Free-Electron Masers (FEMs) with the lasing cavity defined using periodic corrugations on the drift-tube walls1–4. These corrugations form 1D and 2D Bragg resonators, whose reflection bands determine the dominant resonance of the maser5. Proper selection of the FEM undulator magnetic...
VisRad (Prism Computational Sciences), a 3-D view factor code, is used to simulate the multi-dimensional radiation environment within a compact hohlraum. A new hohlraum design proposed in B. Jones, et al. [PRL, v.104, 125001, (2010)] incorporates multiple compact (mm-scale) planar wire array (PWA) x-ray sources that surround a target in the center of the hohlraum cavity, allowing a reduction of hohlraum...
The A6 magnetron was introduced by Palevsky and Bekefi at MIT in 1979 [1]. It is the most studied relativistic magnetron in the literature. Since 2005 UNM has been studying novel advances to the A6 and to the A6 with diffraction output (MDO) that achieve higher power, greater efficiency (η), fast start of oscillations, and eliminate mode competition. This presentation summarizes recent advances pertaining...
Spurious oscillations near edges of pass-bands due to periodicity (π and 2π) as well as edges due to manufacturing tolerance (3π/2) might develop in coupled cavity TWTs (CC-TWTs) and limit their performance. Modeling of spurious oscillations is challenging computational task since the beam-wave interaction occurs at several frequencies simultaneously. In general, stability analysis is a non-linear...
Ion beams driven by ultra-intense lasers have many applications, such as the proton radiography, hadrontherapy and the fast ignition of inertial confinement fusion targets. An important issue in many of the applications is the problem of laser-to-ion beam energy conversion efficiency, which is generally below 10%. In this contribution we discuss one possible method for improving this parameter by...
Oral squamous cell carcinoma (OSCC) is the most widespread malignant oral cavity neoplasm, with even higher proportion of deaths than breast cancer and cervical cancer. Although advances were made in conventional treatment for OSCC such as surgery and radiation therapy, there has not been significant increase in the 5-year survival rate in the past four decades, and chemotherapeutic drug resistance...
Megawatt gyrotrons have a variety of applications including electron cyclotron heating (ECH) of plasmas in fusion devices. High efficiency operation is necessary to minimize the prime power required and to ensure good reliability of the device over its lifetime. To achieve high power and efficiency at the required frequencies, the gyrotrons must utilize large, overmoded cavities that face severe mode...
High-efficiency narrow-band 30-GHz Bragg FEM-oscillator was elaborated during the last few years in JINR-IAP collaboration based on 0.8 MeV / 200 A / 250 ns LINAC LIU-3000 (JINR). An attractive solution to prospect FEM into short wave-lengths keeping beam energy and geometry of electron-optical system is operation at harmonics of bounce-frequency. Two FEM schemes exploiting this idea are under development...
The gyrotron is the most wide-spread variety of electron cyclotron masers based on excitation of a near-cutoff mode of an open microwave cavity. Along with advantages (good selectivity, weak sensitivity to the velocity spread), the use of near-cutoff wave results in several disadvantages (significant Ohmic losses, difficulty to provide frequency tuning). In this work, a new regime of the cyclotron...
A W-band extended interaction klystron (EIK) driven by a 19.5-kV, 3.5-A sheet beam is being developed. Simulations using the 3-D particle-in-cell codes MAGIC1 and ICEPIC2 predict saturated output power levels of 8–10 kW with a saturated gain <30 dB and small signal gain <40 dB. A beamstick has been successfully fabricated and tested, transporting 98% of the emitted current through...
A proposed future TeV collider operating at X-band will require high peak rf powers of hundreds of MW in pulses lasting hundreds of nanoseconds. One method to provide such pulses is through the use of rf pulse compressors to multiply the power produced by high-power klystrons producing multi-microsecond pulse widths. Such compressors can be passive, employing phase switching to discharge rf energy...
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