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Full Mission Simulation Test Report Cajun Probe

Full Mission Simulation Test Report Cajun Probe. University of Louisiana at Lafayette Mark Roberts 5.12.2010. Mission Overview. Objectives. Design and implement a robust, compact payload to latter be integrated into a probe. Develop improved Geiger Counter circuit.

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Full Mission Simulation Test Report Cajun Probe

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  1. Full Mission Simulation Test Report Cajun Probe University of Louisiana at Lafayette Mark Roberts 5.12.2010

  2. Mission Overview Objectives • Design and implement a robust, compact payload to latter be integrated into a probe. • Develop improved Geiger Counter circuit. • Testing of payload’s durability and performance under space conditions. • Obtain and analyze data for a baseline of future experiments.

  3. Changes Since Subsystem Integration No changes have been made to the overall system so far Finished airtight chamber for pressure sensor and mount; The mount is made from a leftover polycarbonate makrolon sheet

  4. Tests Performed (Thus far…) • Geiger Plateau • Pulse Height • Dead Time Testing • Overall Systems Function Test • The Juicy source Life Test! • The Stay Puft Test! • Snowman Test • Deep South Test Appendix

  5. Tests Results Defining the voltage range in which the Geiger-Mueller tube operates most effectively; that is, the region such that the potential difference in the tube is strong enough to ionize all the gas inside the tube upon triggering by the incoming ionizing radiation.

  6. Voltages below the plateau are not high enough to cause complete discharge where as higher voltages causes quenching in which the positively charged ions are drawn to the cathode thus creating a continuous electric pulse in the counter.

  7. Output Pulse An oscilloscope was used to measure the output electrical pulse of the avalanche at different operating voltages; the total charge of the pulse can be found by integrating the area under the contained in a pulse .

  8. Pulse Height Pulse height generally increased fairly linearly as the increasing high voltage bias increased the electric field inside the Geiger Mueller detector thus allowing the discharge to grow larger.

  9. Plotting the pulse height vs. operating voltage on a log-log scale further reveals a linear relationship suggesting a power law.

  10. Dead Time (Gas Ionization Detectors) Dead Time: The minimum time between detectable pulses will be less than the recovery time. This is the pulse resolving time. Non-paralyzable dead-time: is defined as an event that occurs during this period is not counted nor does it influence the ability of the tube to respond to later events. Paralyzable dead time: is the time duration between the end of the non-paralyzable dead time and a resolving pint at which a pulse larger than the discriminator level can be developed.

  11. Split Source Method to determine Dead Time A split radiation source is nothing more than a radioactive source that is split into two pieces. The source as a hole is considered to be the combined sources of N1 and N2 therefore I will call it NC . N1 is the left side of the split source for me; making N2 the right side of NC. Counts are taken from N1,N2, andNC sourced with the same time duration. Then the dead time of the system can be calculated by [seconds] I made my own split source with some Uranyl Acetate that was laying around which happens to contain Uranium 238! =o)

  12. Dead Time of the Geiger Mueller tube with the Nuclear Scaler Model 500 The next series of tables are results from making specific adjustments to a particular section to the Geiger counter circuit in attempts to reduce dead time in the system…not all results are posted.

  13. Will further investigate at a later time…

  14. Overall Analysis • Task to Complete For Launch • Receive Geiger Counter PCB and construct counter • Mounting of Geiger Tube(s) • Complete Assembly of payload • Testing of complete Assembly • Modification to standoffs

  15. Lessons Learned • Have at least one individual in charge of paperwork and producing the necessary documents. • Don’t play with high voltage with lack of sleep i.e. When applying high voltage to a breadboard the metal outer base of the breadboard is held at that potential consequently when your arm glances that part of the board…prepare for a wake up call…

  16. Appendix • Test that were performed and included in last presentation • Overall Systems Function Test • The Juicy source life Test • The Stay Puft Test • The Snowman Test • The Deep South Test

  17. Overall Systems Function Test This test just involved hooking everything together and triggering each sensor to verify everything was behaving nominally. The Juicy source Life Test This just involved obtaining a hot radiation source (not the typical Cobalt 60 source), I settled on Cesium 137 and ran the counter for 16 hours. I don’t have any photos of this test bet lets just say the counter was going berserk the whole time. Video of counter with a Cobalt 60 source.

  18. The Stay Puft Test The average off the shelf Marshmallow is a foam object with closed wall air cells within the foam. By placing a Marshmallow in a Vacuum the walls will expand with reduction of pressure; when air is allowed back into the chamber the walls collapse hence the marshmallow rapidly deflates to a shriveled state from it’s original form. The Stay Puft Test is to demonstrate the effectiveness of the air tight containers' constructed. One marshmallow is placed inside the air tight container and then placed into the vacuum chamber along with another marshmallow.

  19. Snowman Test The Snowman test is just a basic cold test where the payload is placed into a well insulated container and surrounded with dry ice to test the performance of the system(s) in a cold environment.

  20. Deep South Test The Deep South test is designed to test the systems performance when heat is applied. Unfortunately all I had to my disposal was an industrial hot air gun. Thus to help distribute the hot air more evenly I threw together a black foam box (black body) and placed the payload inside this body with various temperature sensors placed through out it.

  21. Deep South Test

  22. Deep South Test

  23. Test Results: Stay Puft! The marshmallow did indeed stay puft! Test Results: Snowman Once tube reaches a particular temperature voltage drop off is dramatic

  24. Test Results: Deep South Resulting effects….

  25. Test Results: Deep South Temperature and Voltage are directly proportional here with a consequence of quenching occurring

  26. Conclusions The results of the testing were as predicted however I did notice that the pressure sensor yields bogus data once it reaches a particular temperature in a cold environment. However, these temperatures will not be reached on the rocket but some type of insulation or a choice of another pressure sensor would solve this issue. Also from the snowman and deep south graphs if you notice the voltages ran. I was not able to use the LND 73118 tube due to a defection. It was replaced with an LND 712 tube. The only similarity between the two tubes are there temperature operational limits. I have already sent the defective LND 73118 tubes back to the manufacture for repair and will repeat these experiments again with the manufactured Geiger counter PCB and the LND 73118 tube.

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