ISSN:
1089-7623
Source:
AIP Digital Archive
Topics:
Physics
,
Electrical Engineering, Measurement and Control Technology
Notes:
We describe the base line design for the wiggler to be used in conjunction with the Experimental Test Accelerator-II (ETA-II) to produce high-power microwave radiation in the Intense Microwave Prototype (IMP) free-electron laser experiment. This design produces negligible noise growth for spontaneous noise sources as large as 20 dB above shot noise, and thus corrects the defects present in earlier iterations of the design, which resulted in diminished gain at the signal frequency because of space-charge effects as well as enhanced spontaneous noise growth at frequencies lower than the signal frequency. In addition, more realistic engineering design constraints on the waveguide size and the wiggler gap spacing have been set by the waveguide wall loading and the electron beam fill factor and have been incorporated in the final base line design. The design assumes that the ETA-II accelerator will supply an electron beam with an energy of 10 MeV, a current of 3 kA, and a brightness of 1.0×108 A/(m rad)2. With this beam and 500 W of input power at a frequency of 250 GHz, the peak output TE01 power predicted by the simulation codes, for a rectangular waveguide of dimensions 3.5×3.0 cm2, is in excess of 12 GW, corresponding to an extraction efficiency of 44%. The wiggler has an overall length of 5.5 m and a period of 10 cm. It consists of a 2-m untapered section at a magnetic field of about 4.3 kG followed by a 3.5-m tapered section with magnetic field ranging from a peak value of 4.5 kG to a minimum of 390 G. The growth of the beam linear fill factor to about 50% sets the lower limit of the magnetic field strength in the tapered wiggler region. A nonsteering, nondisplacing binomial winding pattern has been incorporated into the wiggler profile. The base line design is a 2(1331) pattern spanning six magnet poles, giving an inherent tapering resolution of 30 cm.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1140459
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