INCORPORATING COLD CHAIN
CONTRIBUTORS every facet of electronics before the early 2010s . It was at this point that transistors were capable of generating sufficient power necessary to compete with the existing magnetrons through the use of complex RF combining structures . Due to the imprecise frequency , phase angle , and harmonic characteristics of the magnetron tube , efficient combining of multiple generator units through waveguide had been impossible .
However , by utilising a corporate combining hierarchy , hundreds or thousands of transistors are now able to be operated in unison to produce microwave power levels ranging from as little as one kilowatt up to or exceeding one megawatt ; the upper limit of this technology is yet to be determined .
In addition to the vastly increased power , ongoing research shows solidstate microwave generators are capable of shifting their frequency within the government-allocated ISM bands . These changes in frequency cause changes in the electromagnetic response of the target material , shifting hot- and cold-spots within the material and producing more evenly distributed temperature rise .
Frequency can be shifted at a time scale that is several orders of magnitude above that of thermal phenomenon , allowing the temperature increase to be effectively averaged across almost the total volume of the sample .
The harsh conditions of the mining industry preclude the use of magnetronbased microwave
Generators . Vacuum seals can crack , environmental contaminants can ruin components , and maintenance / replacement costs can ultimately derail projects . The use of transistor-based microwave generators eliminates many of these problems and allows the use of high-power microwaves in locations that were previously impossible , including the direct application of microwaves at underground mining sites . Significant testing and experimentation is being performed to quantify the savings in cost and energy that can be expected from utilising this technology .
One example of this testing includes the design and commissioning of a largescale microwave cavity which is designed to hold immense rock samples and is capable of receiving up to one megawatt of microwave power through multiple waveguide feeds which are strategically located on the cavity walls . Extensive simulation work has been performed to justify the construction of this system by optimising the expected energy absorption by sample materials such as granite , pyroxinite , platreef , and others . The cavity itself is highly instrumented to collect as much thermal and visual data as possible , as well as operational data from the microwave units such as absorbed and reflected power and optimal operating frequency .
Once samples have completed thermal processing in the microwave system , they will undergo extensive physical testing to quantify the performance improvements of the relevant mining operation . This could include reductions in energy expenditure and processing time due to in-situ microfracturing , life-extension for consumable components of mining machines such as milling heads or drill bits , and reductions in total vibration within the mining area that can cause various equipment problems and pose health hazards to mining personnel .
Additionally , the implementation of highpower microwaves may ultimately save lives by allowing the removal of humans from dangerous underground mine sites and making it possible for mining operations to be monitored and controlled remotely from the safety of external control centres .
Phew , for you scientists this has been quite an interesting article , stay safe till next time . CLA
Ongoing research shows solidstate microwave generators are capable of shifting their frequency within the governmentallocated ISM bands .
COLD LINK AFRICA • July / August 2024 www . coldlinkafrica . co . za 27