Improved ramped bunch train to increase the transformer ratio of a two-channel multimode dielectric wakefield accelerator

• Published in: Physical review special topics. PRST-AB. Accelerators and beams Vol. 14; no. 3; p. 031302
• Main Authors: Sotnikov, G. V., Marshall, T. C.
• Format: Journal Article
• Language: English
• Published: College Park American Physical Society 11.03.2011
• Subjects: Aluminum oxide; Cylindrical shells; Particle in cell technique; Shells; Transformers
• ISSN: 1098-4402; 1098-4402; 2469-9888
• DOI: 10.1103/PhysRevSTAB.14.031302

Here we show a possibility of applying the ramped drive bunch train (RBT) technique to a two-channel coaxial dielectric wakefield accelerator (CDWA). For numerical research we study a 28 GHz structure with two nested alumina cylindrical shells having these diameters: outer shell, OD=28.1mm , ID=27mm ; inner shell, OD=6.35mm , ID=4.0mm . The structure is to be excited by a train of four annular bunches having energy 14 MeV and axial rms length 1 mm; the total charge of bunches is 200 nC. In the case of equally charged drive bunches, spaced apart by the principal wakefield wavelength 10.67 mm, we obtained transformer ratio T=3.4 . If the bunch charge is increasing as the ratio 1∶3∶5∶7 and the bunches are spaced by one and one-half wavelengths, we obtained T=3.8 . We found that if the charge ratios are 1.0∶2.4∶3.5∶5.0 and the spaces between the bunches are 2.5, 2.5, and 4.5 wakefield periods, then T increases strongly, T∼20 . The RBT also can be used successfully in a high gradient THz CDWA structure. A particle-in-cell simulation shows that the four drive bunches can move without appreciable distortion.