In traveling wave tube (TWT) amplifiers, an axial focusing magnetic field is required to keep electrons traveling in a narrow, pencil-like beam over the considerable length of the circuit. Conventionally, this focusing has been accomplished by using a periodic permanent magnet system housing axially polarized ring magnets. Making the structure to this point has been a complicated process consisting of brazing multiple metals together and honing the piece to the desired specifications. We present a new method of fabricating this housing structure monolithically using iron, developing magnetically oversaturated housing regions, and saving processing time and effort.
"New Method of Integrating Periodic Permanent Magnet (Ppm) Assembly in Traveling Wave Tubes (TWTs
)," Progress In Electromagnetics Research C,
Vol. 10, 187-199, 2009. doi:10.2528/PIERC09082907
1. Leupold, H. A., "Approaches to permanent magnet circuit design," IEEE Trans. Magn., Vol. 29, No. 6, 2341-2346, Nov. 1993. doi:10.1109/20.280860
2. Gilmour Jr., A. S., Principles of Traveling Wave Tubes, Artech House, Inc., Norwood, 1994.
3. Leupold, H. A., E. Potenziani II, and A. S. Tilak, "Iron-free permanent magnet structures for traveling wave tubes," Proc. International Electron. Devices Meeting (IEDM), 411-414, 1991.
4. MAXWELL2D User's Manual, Ansoft, 2005.
5. Matsumoto, H., T. Shintake, Y. Ohkubo, H. Taoka, K. Ohhashi, and K. Kakuno, "The new fabrication method for a periodic permanent magnet (PPM) C-band (5712 MHz) Klystron," Proc. 25th Linear Accelerator Meeting, 14A-01, 2000.
6. Sprehn, D., G. Caryotakis, E. Jongewaard, and R. M. Phillips, "Periodic permanent magnet development for linear collider X-band klystrons,", Stanford Linear Accelerator Center, Stanford University, Stanford, CA 94309.
7. Baird, J. M. and A. C. Attard, "Design of single-anode, mig-type gyrotron gun for a 35 GHz Gyro-TWT," Microwave Symposium Digest, MTT-S International, Vol. 81, No. 1, 261-263, Jun. 1981. doi:10.1109/MWSYM.1981.1129891
8. Zhang, H., W. Liu, S. Bai, and K. Chen, "Periodic permanent magnet focusing system with high peak field," J. Magn. Magn. Mater., Vol. 320, 1675-1679, 2008. doi:10.1016/j.jmmm.2008.01.017
9. Leupold, H. A., E. Potenziani II, and A. S. Tilak, "Flux tailoring of permanent magnet solenoids," IEEE Trans. Magn., Vol. 29, No. 6, 2905-2907, Nov. 1993. doi:10.1109/20.281093
10. Strnat, K. J., "Modern permanent magnets for applications in electro-technology," Proc. IEEE, Vol. 78, No. 6, 923-946, Jun. 1990. doi:10.1109/5.56908
11. Baird, M., et al. MPPM Program Manual User's Guide, Apr. 2002.