Author: Tantawi, S.G.
Paper Title Page
MOPP128 Bridging the Gap Between Conventional RF Acceleration and Laser Driven Acceleration 358
MOPOL04   use link to see paper's listing under its alternate paper code  
 
  • M.V. Fazio, V.A. Dolgashev, S.G. Tantawi
    SLAC, Menlo Park, California, USA
  
  For decades conventional RF accelerators have been built and operated with ever increasing capability through a few tens of gigahertz in frequency. More recent research takes advantage of the continuing development of high peak power short pulse lasers to drive accelerator structures at optical frequencies. This jump from RF to optical frequencies skips four orders of magnitude in wavelength. With recent experiments that demonstrate high gradients in metallic structures at millimeter wavelengths one is compelled to consider the viability of new approaches for acceleration in the millimeter-wave to terahertz regime. This paper will explore some of these possibilities.  
 
TUPP123 Design of Novel RF Sources to Reduce the Beam Pace-Charge Effects 712
TUPOL10   use link to see paper's listing under its alternate paper code  
 
  • M. Dal Forno, A. Jensen, R.D. Ruth, S.G. Tantawi
    SLAC, Menlo Park, California, USA
  
  Funding: DOE
Traditional RF sources, such as Klystrons, TWT require a magnet (such as a solenoid) in order to maintain the electron beam focusing, compensating the particle repulsion caused by space charge effects. We designed a novel RF source with an alternative approach that reduces beam space charge problems. This paper shows the design of the device, with a new formulation of the Child’s Law, and the mode-beam stability analysis. The electron beam interaction with the cavity fields has been analyzed by means of particle tracking software in order to evaluate the beam bunching and the beam dynamics. 		 
poster icon Poster TUPP123 [0.172 MB]  
 
TUPP124
 Update on High Power Tests of Single Cell Standing Wave structures at SLAC  
 
  • V.A. Dolgashev, J.R. Lewandowski, S.G. Tantawi, S.P. Weathersby, A.D. Yeremian
    SLAC, Menlo Park, California, USA
  • Y. Higashi
    OIST, Onna-son, Okinawa, Japan
  • B. Spataro
    INFN/LNF, Frascati (Roma), Italy
  
  Funding: This work was supported by the U.S. Department of Energy contract DE-AC02-76SF00515.
We report results of ongoing high power tests of single cell standing wave structures. These tests are part of an experimental and theoretical study of rf breakdown in normal conducting structures at 11.4 GHz. The goal of this study is to determine the accelerating gradient capability of normal-conducting rf powered particle accelerators. The test setup consists of reusable mode-launchers and short test structures powered by SLAC's XL-4 klystron. We have tested structures of different geometries, cell joining techniques, and materials, including copper structures with molybdenum and stainless steel irises. In previous experiments we found that the breakdown rate is correlated more with peak surface pulse heating than with the peak surface electric field. In recent experiments we continue study of hard cooper alloys and manufacturing techniques that avoid heat treatment of the metal. As a result we observed that cooper silver alloys show superior performance in comparison with both hard and heat treated copper. 		 
 
WEIOA03
 New X-band and above high gradient linacs  
 
  • S.G. Tantawi, M.V. Fazio
    SLAC, Menlo Park, California, USA
  
  During the past few years we gained a qualitative understanding of the basic physics of breakdown phenomena in high vacuum RF structures. With this understanding we have been able to demonstrate accelerator structures with gradient extended to 175 MV/m, well above the state of the art. This was accomplished with the understanding of geometrical effects and material properties. To push the gradient further, the scaling lows developed to date requires us to increase the frequency to reduce the filing time and use very short pulses at the same order as the filling time. Indeed, initial experimental investigation shows the possibility of a 1GV/m structure at W-band for a structure that operates for only 3 ns. The next stage of developments can not only address the next generation of high gradient structure technologies but also has to address the efficient production and utilization of RF power for linacs. We will present the development of RF accelerator structures aimed at operating frequency from mm-wave to THz. We also present the experimental results of novel rf sources aimed to be integrated with these structure for an efficient overall system.  
slides icon Slides WEIOA03 [15.516 MB]  
 
THPP125 Super-Compact SLED System Used in the LCLS Diagnostic System 1151
 
  • J.W. Wang, S.G. Tantawi, C. Xu
    SLAC, Menlo Park, California, USA
  
  Funding: * Work supported by Department of Energy contract DE–AC03–76SF00515.
At SLAC, we have designed and installed an X-band radio-frequency transverse deflector system at the LCLS for measurement of the time-resolved lasing effects on the electron beam and extraction of the temporal profile of the pulses in routine operations. We have designed an X-Band SLED system capable design to augment the available klystron power and to double the kick.