GYROTRON-BASED MILLIMETER-WAVE: BEAMS FOR MATERIAL PROCESSING. Thomas Hardek Wayne Cooke. William P e r r y D a n i e l Rees

Transcription

1 GYROTRON-BASED MILLIMETER-WAVE: BEAMS FOR MATERIAL PROCESSING Title: Thomas Hardek Wayne Cooke William P e r r y D a n i e l Rees AUthOr(s): 32nd Microwave Power Symposiurr~, Ottawa, Canada, July 14-16, submitted to: DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Gnvernment nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or mponsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark. manufacturer, or otherwise docs not necessarily constitute or imply its endorsement, mommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors exprtsstd herein do not necessarily state or reflect thosc of the United States Government or any agency thereof. LosAlamos II NATIONAL LABORATORY Los Alamos Nationai Laboratory, an affirmative actjon/equal Opportunity employer, is operated by!he University of California for the US. Department of Energy under contract W-7405ENG-36. By ecceptance of this article, the publisher recognizes that the U.S. Government retains a nonexclusive. royalty-free license to publish or reprodugethe published f w n of this eontrikrtlon. or to allow others to do SO. for U S. Government purposes. Los Alamos National LaboraQaiy reqoests that the publisher identify this cutlde - urvlr d m n w d invbr thn s i a n i ~ c nf tha I I C nanahnnt nf Enarmi Thn I M A l a m n e kletimd I ahnrahni r+rruvllii a t d e

2

3 i05/19i97 YON 1 0 : 0 9 FAX t. GYROTRON-BASED MILLIMETER-WAVE BEAMS FOR MATERIAL PROCESSING THOMAS W. HARDEK, WAYNE D. COOKE, WILLIAM L. PERRY, DANIEL E,.REES, Los Alamos National Laboratory, Los Alamos,New Mexico, ABSTRACT Los Alamos scientists, working with the National Center for Manufacturing Sciences have assembled a materials processing facility utilizing gyrotron based RF sources. The facility is intended to demonsh-ate unique features available at 30 to 84 GHz. This paper presents an overview of our quasi-optical facility and describes the microwave hardware. INTRODUCTION Microwave processing of materials has traditionally utilized frequencies in the 915 MHz and 2.45 GHz bands. Microwave power sources are readily available at these fkquencies but the relatively long wavelengths can present challenges in uniformiy heating materials. An additional difficulty is the typically poor coupling of ceramic based materials to the microwave energy. Los Alamos National Laboratory scientists, working in conjunction with the National Center for Manufacturing Sciences (NCMS), have assembled a high-frequency demonstrationprocessing facility[l] with capabilities over a broad range of microwave fiequencies. The facility is primarily intended to demonstratethe unique features available at millimeter wavelengths but we have access to hardware capable of providing large amounts of cw or pulsed power throughout the entire radio frequency spectrum. We can readily provide quasi-optical, 37 GHz beams at continuous wave (cw)power levels in the 8 kw range. We have also provided beams at 84 GHz at 10 k W cw power levels. We are presently preparing a facility to demonstrate the sintering of ceramics and the processing of other materials under controlled environmental conditions at 30 GHz. The ability to process materials at millimeter wavelengths has been the primary focus of ow program. Through the close cooperation of the Paton Welding Institute (PWI) f23,and the Salyut Company, former Soviet Union organizations, Los Alamos has acquired a materials processing chamber and gyrotron equipment capable of providing many kilowatts of continuous, quasi-optical, output power in the 37 0.r 84 G& microwave bands. QUASI-OPTICAL SYSTEM Our 37 GHd84 GHz system features a quasi-optical beam which may be tailored to the processing application by combinations of dielectric lenses and metal mirrors. In addition to adjusting the beam distribution the mirrors may be scanned to sweep the beam across a large area sample. Processing is done primarily in an air environment although we sometimes insert the sample within a quartz tube and back fill the tube with an inert gas. The process may be viewed through water-filled, microwave screened, windows. We have a thermal-imaging camera, and other thermal detecting equipment available to document the process. The system provides a continuous (cw) output. Power may be adjusted from several hundred watts to 10 kw. and may be gated on and off with pulse lengths as short as 0.5 second. For materials that must be heated slowly the pulse repetition rate and the pulse width may be gradually increased. Figure 1 gives a typical pulsed output power curve. 003

4 4000 M : E 30 * a 500 lo v 20 g o q V H w N -10 H d Seconds Figure 1. Typical output power pulse (upper trace) and anode current. 30 GHz MULTI-MODE-CAVITY SYSTEM In addition to the quasi-optical equipment we have recently installed a 30 GHz processing system produced by the Institute of Applied Physics, N i h y Novgorod, Rwsia[3]. This facility mcorporaks a multi-mode chamber configured to achieve a uniform microwave field throughout the processing chamber volume. The chamber may be evacuated or operated at up to 2 atmospheres providing the capability of precisely controlling the environment in which materials are processed. The system has been designed to operate under complete computer control allowing repeated experimental cycles under identical microwave and environmental conditions. Figure 2 is a sample temperature curve resulting from an actual processing cycle. The rate of temperature rise may be selected as a predetermined sequence or altered on-thefly as the processing proceeds. As shown in Figure 2 the temperature of the processed material accurately followed the program function throughout the cycle and only deviated significantly at the conclusion of the cycle where the material was allowed to cool at its own rate. Figure 2. Temperature Profile Taken During Ceramic Sintering Cycle.

5 ,05/19L97 3 MON 10:12 FAX 505 ti M 005 CONCLUSION We are presently operating the gyrotron hardware under an agreement with the National Center of manufacturing Sciences. We can identi& several areas where the use of high-power millimeter-waves technology will provide industry with unique materials processing opportunities. We continue to demonstnate the unique features of this emerging technology and hope to be able to present some of our results in the near future. REFERENCES 1. J. D. Katz and D. E. Rees, Quasi-Optical Gyrotron Materials Processing at Los Alamos, Ceramic Transactions Voi. 59, p , (1995). 2. Vladislav Skliarevich, Consultant for NCMS and, Michail Shevelev, Peter Syrovets, Paton. Welding Institute, Kiev, Ukraine, Private Communication (1995) Y. Bykov, A. Eremeev, V. Holoptsev, Comparative Study of ShN4 Based Ceramics Sintering at Frequencies 30 and 8 3 G W MRS Symposium Proceedings, Microwave Processing of Materials V, p , (1996).