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Computer models in the design of FXR

Description: Lawrence Livermore National Laboratory is developing a 15 to 20 MeV electron accelerator with a beam current goal of 4 kA. This accelerator will be used for flash radiography and has a requirement of high reliability. Components being developed include spark gaps, Marx generators, water Blumleins and oil insulation systems. A SCEPTRE model was developed that takes into consideration the non-linearity of the ferrite and the time dependency of the emission from a field emitter cathode. This model was used to predict an optimum charge time to obtain maximum magnetic flux change from the ferrite. This model and its application will be discussed. JASON was used extensively to determine optimum locations and shapes of supports and insulators. It was also used to determine stress within bubbles adjacent to walls in oil. Computer results will be shown and bubble breakdown will be related to bubble size.
Date: January 1, 1980
Creator: Vogtlin, G. & Kuenning, R.
Partner: UNT Libraries Government Documents Department

Two-Beam Accelerator: structure studies and 35 GHz experiments

Description: The Two-Beam Accelerator (TBA) shows great promise for achieving high accelerating gradients, perhaps >250 MV/m, for such machines as electron linear colliders. This paper presents the results of studies of candidate structures for a TBA. Also, the hardware and program for 35 GHz high-gradient testing are described. 18 refs., 13 figs.
Date: May 1, 1985
Creator: Hopkins, D.B. & Kuenning, R.W.
Partner: UNT Libraries Government Documents Department

Phase and amplitude considerations for the Two-Beam Accelerator

Description: Phase and amplitude considerations are made for a Two-Beam Accelerator and analytic formulas are obtained expressing the phase and amplitude errors in terms of magnetic wiggler errors, beam energy errors, beam current errors, and microwave field amplitude errors. The necessity of phase and amplitude control is shown and schemes are proposed which can accomplish this control.
Date: February 1, 1985
Creator: Kuenning, R.W.; Sessler, A.M. & Wurtele, J.S.
Partner: UNT Libraries Government Documents Department

Beam optics in the FXR 1. 5 MeV, 4 kA injector

Description: The 20 MeV, 4 kA linear induction accelerator (FXR), currently under construction at LLNL, will use a cold cathode injector. The foil cathode consists of a 0.03 mm tantalum ribbon wound in a spiral with successive turns spaced 0.8 mm apart. The emitted current will be 15 to 20 kA but will be reduced to 4 kA by collimating immediately beyond the anode. This will minimize the beam emittance and maintain a good impedance match with the low impedance driving source. Computer simulation was used extensively to optimize the configuration of the beam forming electrodes, the emitter geometry, and the overall focusing and beam transport system in the injector region. This paper will discuss the approach used and the problems encountered in the design of the diode geometry and of the overall beam optics. Preliminary experimental results will be presented and will be compared with the computer model predictions.
Date: January 1, 1981
Creator: Scarpetti, R.D.; Kuenning, R.W. & Wong, K.C.
Partner: UNT Libraries Government Documents Department

Radio frequency phase in the FEL section of a TBA

Description: The basic idea of the two-beam accelerator is to have a low-energy beam travel through an undulator magnet and generate microwave radiation by the free electron laser mechanism. The energy of the low-energy beam is repeatedly resupplied by induction units, and the microwave radiation is employed to accelerate the desired particles to very high energies. The two-beam accelerator must incorporate in its free electron laser portion tight control of the rf wave amplitude and phase. With regards to this, the present paper extends many particle simulation to include non-equilibrium conditions and discusses several feedback systems to correct phase errors. A many-particle simulation is used to study the evolution of the radiation phase and amplitude, and results are compared with one-dimensional resonant particle analysis. The electric field evolution is also discussed. (LEW)
Date: August 1, 1986
Creator: Kuenning, R. W.; Sessler, A. M. & Sternbach, E. J.
Partner: UNT Libraries Government Documents Department

Saturable reactor-controlled power supply system for TCT/TFTR neutral beam sources

Description: Each neutral beam source requires one major power supply, the acceleration supply, and four auxiliary power supplies. The power supplies are designed to permit independent interruption of current to any source and crowbarring within 20 $mu$sec, in the event of a source spark, while not disturbing the normal pulsing of all other adjacent sources. The sources are described. (MOW)
Date: November 1, 1975
Creator: Baker, W.R.; Hopkins, D.B.; Dexter, W.L.; Kuenning, R.W. & Smith, B.J.
Partner: UNT Libraries Government Documents Department


Description: The sensitivity of the radio frequency (rf) wave generated by the free electron laser portion of a Two-Beam Accelerator (TBA) is analyzed, both analytically and numerically in a 'resonant particle' approximation. It is shown that the phase of the rf wave is strongly dependent upon errors in the wiggler strength and wavelength and upon the electron beam characteristics of energy and current. The resulting phase error is shown to be unacceptable for a TBA, given reasonable errors in various components. A feedback system is proposed which will keep the rf wave phase within acceptable bounds. However, the feedback system is, at best, cumbersome and a simpler system would be desirable.
Date: July 1, 1985
Creator: Kuenning, R.W. & Sessler, A.M.
Partner: UNT Libraries Government Documents Department

High gain free electron laser at ETA

Description: A single pass, tapered electron wiggler and associated beam transport has been constructed at the Experimental Test Accelerator (ETA) at Lawrence Livermore National Laboratory (LLNL). The system is designed to transport 1 kA of 4.5 MeV electrons with an emittance of 30 millirad-cm. The planar wiggler is provided by a pulsed electromagnet. The interaction region is an oversized rectangular waveguide. Quadrupole fields stabilize the beam in the plane parallel to the wiggler field. The 3 meter long wiggler has a 9.8 cm period. The Free Electron Laser (FEL) will serve as an amplifier for input frequencies of 35 GHz and 140 GHz. The facility is designed to produce better than 500 Megawatts peak power.
Date: February 9, 1983
Creator: Orzechowski, T.J.; Prosnitz, D.; Halbach, K.; Kuenning, R.; Paul, A.; Hopkins, D. et al.
Partner: UNT Libraries Government Documents Department

Status of the Lawrence Berkeley Laboratory and Lawrence Livermore National Laboratory free electron laser (FEL)

Description: A description of the FEL experiment underway at the 10 kA, 5 MeV Experimental Test Accelerator (ETA) is described. The facility has been designed to investigate the high-gain operation of an FEL.
Date: September 19, 1983
Creator: Orzechowski, T.J.; Moebus, M.C.; Penko, F.A.; Prosnitz, D.; Rogers, D.; Chavis, C.S. et al.
Partner: UNT Libraries Government Documents Department