chapter three

3.5i Efficiency of the System:

The efficiency of the system can be defined as the ratio of the output power to the input power at 100%.The output power of our system has been measured by using IR power meter [heat sink detector( coherent ) ]of type LTD, model 542]maximum scale power measurement of 1000 W.i
The efficiency of the laser varies with the current flowing through the tube..i

Maximum efficiency and output power might not be obtained at the same time, the current which gives greatest efficiency might being lower than that which gives the best output. .i


The maximum efficiency comes out to be in our work equal 16.2% at input power equal of 90W, discharge current of about 20 mA, discharge voltage 11kV and output power equal 14.6 W at a plasma tube pressure of 15mbar.These measurement were carried out for only one fold design ..i

But the maximum output power has been recorded at an efficiency equal 10% and input power equal 235W which is equal 23.5Wat pressure of 12mbar input discharge current 28mA Figure 3.7 shows the variation of the efficiency with input power at different pressure..i

It is clear from the figure that the efficiency depends on the input current being used..i
In two fold (V- configuration) the maximum laser output power was 37 W at input power of 400 W, discharge voltage was 13kV at pressure 16mbar and discharge current 30mA. The efficiency of such design is about 9% the total discharge length of the system equal 1.5m and cavity length of 2m .This value considered to be very low with the expected value which is about 75 W because the available input current compare with the current that we need is very low .The min required value of the current should be not less than 100mA..i



Fig.3.7: The Effect of Efficiency by Input Power at Different Pressure..i

So, the resultant of our work slow axial flow CO2 laser multi folds work in TEM01 mode (as we have see in the lap when the laser drop at the different material basis) .i

Conclusion :.i

Usually, from every experiment, there are results. These results lead to conclusions that consider as rules of thumb.Our experiments guided us to our own rules of thumb as follow:-.i

1.Seeking for reliability of CO2 system starts from its power supply. The ballast resistance that should be used to control the amount of the current that enter to the discharge tube and to protect power supply from the high current delivered due to discharge processes..i

2.Three main parameters affecting on the output power of CO2 laser are pressure, current and discharge voltage, where the current affects by the cross-section area of the discharge tube and the voltage affects by the active discharge length. Controlling the discharge needs to control gas pressure..i

3.Its possible to get uniform excitation in a multi folds CO2, V-configuration so this design proved to be quite reliable as the have no vacuum troubles and an other excepted problems during the construction and operation as well as minimize size and cost of the system..i

4.It is possible to get uniform excitation of the V-shape multi fold..i


Proposal for Future Work:-.i

1.A compact power supply should take the priority of the future work,due to fact that ,controlling the power supply and its current will control the whole system easily .There fore anew power supply of higher current(1A-2A) should be design and implemented before any farther improvements in the CO2 laser system ..i

2.Completing the system by groups the different configuration that have been design into one system and increase the number of folds to five tube at each fold to increase the power to 500 W..i

3.Using this laser in the industrial application like wielding, drilling, melting and cutting for ****l and non****l..i

4.Use Teflon material instead of Bakelite for higher thermal resistive..i