Plasma Science and Fusion Center
Massachusetts Institute of Technology
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WAves & beams
| Smith-Purcell Theory| 17 GHz RF Gun | 17 GHz High Gradient Accelerator | Novel Electromagnetic Structures |
High Gradient Accelerator Research
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| Researchers working on the 17 GHz high gradient electron accelerator. A 17 GHz relativistic klystron amplifier is used to drive the accelerator |
Smith-Purcell Theory
Smith-Purcell radiation is emitted when an electron bunch is passing above a periodic structure (i.e. grating). It is characterized by a broadband radiation spectrum in which the wavelength depends on the observation angle. This radiation could be used as an intense THz radiation source as well as a non-destructive bunch length measurement technique. The goals of this research are to accurately compute the radiated intensity from a finite-length grating and support the experimental results.
Time-domain simulation of Smith-Purcell radiation (*.avi, 4.2 MB)
Smith-Purcell Radiation from a 2D Charge Moving Above a Short Grating: Time & Freqency Domain Models
17 GHz RF Gun
Recent research was conducted on a 17 GHz, microwave driven, photocathode electron injector. This device, sometimes called an RF gun, can generate a 2 ps beam of 1-2 MeV, 50-100 A electrons at high repetition rate. The RF gun experiment is designed to produce a world record brightness of 8*10**14 A/m**2. The current experiment has measured the brightness to within a factor of ten of the design value. The electron beam from the RF gun can be directly applied to microwave generation experiments or it can be used as an injector into a 17 GHz, high gradient accelerator.
17 GHz Gradient Accelerator
Another experiment in progress involves the commissioning of a high gradient 17 GHz electron accelerator built in collaboration with Haimson Research Co. (HRC). The accelerator began operation in 1999 and currently produces a .25A average current, 20 MeV electron beam. At this time the HRC accelerator is the highest power accelerator on the MIT campus and the highest frequency standalone accelerator in the world. Current experiments to measure the emittance, beam size and bunch length are being implemented.
Novel Electromagnetic Structures
The division is also involved in the development of novel materials for applications in microwave vacuum electronics such as photonic band gap (PBG) structures and novel cathodes. We have experimentally demonstrated the benefits of using PBG structures in high gradient accelerators and high frequency microwave sources. Carbon nanotube and silicon tip based field emitter arrays are being investigated for potential applications in plasma displays and high current density cathodes for microwave tubes.
