emblation microwave INDUSTRIAL, SCIENTIFIC AND MEDICAL

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1 emblation microwave INDUSTRIAL, SCIENTIFIC AND MEDICAL THE NEXT GENERATION OF MICROWAVE SYSTEMS Cold Plasma

2 Recent developments in microwave technology offer a highly versatile and reliable option for power generation in cold plasma applications. As a fast growing area of research, plasma physics has the potential to revolutionize a number of global industries. With continued success in sterilization and coating applications, there are a number of opportunities being developed using low temperature cold plasma and key to their success is the ability to find stable, reliable power sources. Traditionally 2.45GHz magnetron sources have been used, but consistent and repeatable delivery of stable power for cold plasma applications is challenging using this technology. New Developments For low-power requirements (such as Surfatron devices, or anything 100W and below), solid state microwave systems can provide a number of benefits over standard magnetron and travelling wave tube (TWT) power sources. While magnetron power sources are still the industry standard for high power requirements, recent advances in gallium nitride (GaN) have allowed for significant innovation in solid state generators at 2.45GHz.

3 Stable and Flexible Power Sources WHAT S DIFFERENT: A reliable power source is crucial for achieving stable plasma generation. Solid state generators, such as Emblation Microwave s range of combined microwave generators and amplifiers, can offer an advantage to researchers as they produce a highly stable signal. These systems also offer better power conditioning because they operate at very low voltages compared with magnetron power generators. RECENT DEVELOPMENTS IN SOLID STATE MICROWAVE GENERATOR SYSTEMS CAN PROVIDE SIGNIFICANT ADVANTAGES IN POWER STABILITY AND SYSTEM RELIABILITY AND AT RELATIVELY LOW COST. WHY SHOULD I CARE: Traditional magnetron systems have a number of issues relating to high voltage supply. High voltages can create a ripple a consequence that often affects frequency behaviour, phase and power output within the system. This figure of ripple can be as high as 5% at full output with a 1-2% drift in operating frequency typically solid state systems will be lower than 0.5% with phase noise less than -107dBc. Generally, magnetron systems are a cruder means of generating microwaves and can become noisy an unreliable output affects the quality, consistency and controllability of plasma generated. 1 Pulsed and CW microwave plasma excitation for surface functionalization in nitrogen-containing gases. Meyer-Plath, A.A., Finke, B., Schröder, K., Ohl A. Institut für Niedertemperatur-Plasmaphysik, Friedrich-Ludwig-Jahn-Strasse 19, Greifswald, Germany. Surface and Coatings Technology, Vol , Sept Oct r 2003, Pages Proceedings of the Eight International Conference on Plasma Surface Engineering ONE MORE THING: Emblation s microwave systems can generate continuous (CW) or pulsed output power (PWM) allowing researchers the flexibility to explore various options in plasma generation 1. Emblation s generators can also run as an amplifier and can be driven by very high precision phase-locked sources, for the ultimate in frequency control.

4 Stability and Mismatch WHAT S DIFFERENT: Emblation s generators present a comprehensive solution to issues relating to impedance mismatch. These next generation solid state systems are mismatch tolerant and do not change output frequency with match. WHY SHOULD I CARE: Impedance mismatch is a common problem when generating plasma. Any significant mismatch can cause issues with performance, damage to equipment and unreliable power measurement. A mismatch can also affect the stability of the magnetron source which in turn can distort the operating frequency. Measured Reflected Power (W) Distance (cm) FIGURE 1. Swept vs unswept power measurment (510cm cable +/- 0.7% 2.45GHz 25% mismatch 100W) Sweep On Sweep Off THE KEY TO SUCCESS IN MANY COLD PLASMA PROJECTS IS THE ABILITY TO FIND A STABLE, RELIABLE POWER SOURCE ONE MORE THING: Emblation s microwave systems also uniquely feature SafeSweep - a function which provides an accurate measurement of the real reflected power in mismatched loads, minimising the effects of false readings caused by voltage standing wave (VSWR) cancellations. These cancellations occur periodically along the cable and in CW applications can provide a false indicator of low returned energy, suggesting an optimal match which may not be the case. This is highlighted in Figure 1, where small differences in cable phase-length can suggest anywhere between 30% and 8% reflected power, when in reality the load returns 25% of the energy.

5 Safety Risks WHAT S DIFFERENT: Today s solid state systems typically run at 38V dc (amplifier internal voltages) compared with voltages in excess of 1500V ac for magnetron based systems, and are put through rigorous safety tests to ensure the highest possible levels of user safety. WHY SHOULD I CARE: In addition to performance, there is also user safety to consider. While utilising old microwave equipment can be cost-effective, high voltage systems can create significant risks for the user. Researchers have been known to use old, defunct medical equipment as 2.45GHz power supplies, which not only puts the success of their project at risk, but also the user s safety. Reliability WHAT S DIFFERENT: A substantial benefit that the latest advances in microwave systems offer is reliability. Solid state systems benefit from modular architecture, providing dramatic system reliability advantages. WHY SHOULD I CARE: Vacuum tube based Magnetrons and TWT based systems suffer from operational shelf-life issues due to eventual loss of cathode emission standard life time values are typically around 2000 hours for low-power magnetrons. Typically vacuum tube devices have to be routinely cycled to maintain their operation which is also time consuming. As solid state systems rely on transistors rather than tubes, shelf life reliability is not an issue.

6 About Emblation Microwave Emblation Limited is a global leader in the development of compact, next-generation microwave generators. The company provides some of the smallest microwave generators available as turnkey, OEM solutions for organizations developing microwave power systems. Working with the latest technologies, Emblation can customize all products to client specifications, including full system design (applicator & generator), software and operating frequency. For more information about solid state microwave generators and how researchers can benefit from a highly stable signal output, or for information and advice on how to combat issues relating to impedance mismatch, contact Emblation Microwave today. emblation microwave INDUSTRIAL, SCIENTIFIC AND MEDICAL An Emblation Limited Company Emblation Microwave Forrester Lodge Inglewood Alloa Scotland UK FK10 2HU Tel: +44 (0) Fax: +44 (0) info@emblationmicrowave.com