DYNAMIC PROCESSING OF MATERIALS IN THE MICROWAVE POWER FIELD,
USING A NEW PROCEDURE AND DEVICE

V.Surducan, E.Surducan

 National Institute for research and development of Isotopic and Molecular Technologies,  
75-103 Donath Street, POB 700, Cluj Napoca, email: manu@l30.itim-cj.ro

For research and technology purpose there are many microwave power systems for processing of small quantities of material (10 to 500 ml). Typical applications are: sample preparation for analysis, chemical assisted reactions, extractions from natural products and so on.
These non-conventional treatments are based on microwave absorption process in materials, phenomenon that depends on sample dielectric loss and its change with temperature.
The classical microwave power systems operate at a fixed frequency fo and constant power Po (usual 900-1200W at 2.45GHz). What is controlled is the time of irradiation or the energy transferred in material by the microwaves at a fixed generator output power. Some apparatus use microwave variable attenuators for effective control of the microwave power. 
The principal characteristic of these microwaves treatments is the continuous microwave power activation of the treated material at a fixed microwave frequency.
	The use of a dynamic control of the microwave power magnetron and a range of frequency Df as result, is what we consider a new concept in microwaves power processing of materials. This procedure changes the microwave absorption process. Microwave absorption depends not only by the sample dielectric loss but also by the linear and rotational resonant absorption of treated molecular systems.
	Practically, in the microwave power systems that operate on this concept, the microwave input in material is controlled in every second from 0 % to 100% of the time. With other words the magnetron is active from 10 to 100 ms, selectable from working diagram. This time control is active in every second so we can say that is “one second energy control”. In fact it is about of one-second repetitive magnetron control composed by a dynamic start with Df1 frequency, followed by a stabile fo period and closed by dynamic stop with Df2 frequency.
	In this paper we present the technical solution used for the practical application of the concept and the microwaves power device we have realized (fig.1).

FIG.1 Dynamic microwaves treatment unit