Optimization of the Extraction Efficiency of a Gas stopper using a Th-228 Source

Transcription

1 Optimization of the Extraction Efficiency of a Gas stopper using a Th-228 Source August 3, 2012 Mike DeVanzo, Towson University Graduate Mentor: Marisa C. Alfonso Faculty Advisor: Dr. Charles M. Folden III 1

2 Heavy interest in Gas Stopper H Hydrogen Li Lithium Be Beryllium Na Mg Sodium Magnesium B Boron Al Aluminium C Carbon Si Silicon N Nitrogen P Phosphorus O Oxygen S Sulfur F Fluorine Cl Chlorine He Helium Ne Neon Ar Argon K Potassium Rb Rubidium Cs Cesium 87 (223) Fr Francium Ca Calcium Sr Strontium Ba Barium Ra Radium Sc Scandium Y Yttrium La Lanthanum Ac Actinium Ti Titanium Zr Zirconium Hf Hafnium 104 (261) Rf Rutherfordium V Vanadium Nb Niobium Ta Tantalum 105 (262) Db Dubnium Cr Chromium Mo Molybdenum W Tungsten 106 (266) Sg Seaborgium Mn Manganese 43 (98) Tc Technetium Re Rhenium 107 (262) Bh Bohrium Fe Manganese Ru Ruthenium Os Osmium 108 (265) Hs Hassium Co Cobalt Rh Rhodium Ir Iridium 109 (266) Mt Meitnerium Ni Nickel Pd Palladium Pt Platinum 110 (271) Ds Darmstadtium Cu Copper Ag Silver Au Gold Zn Zinc Cd Cadmium Hg Mercury 112 (277) 111 (272) Cn Copernicium Rg Roentgenium Ga Gallium In Indium Tl Thallium 113 (284) Ge Germanium Sn Tin Pb Lead 114 (288) Fl Flerovium As Arsenic Sb Antimony Bi Bismuth 115 (288) Se Selenium Te Tellurium 84 (209) Po Polonium 116 (292) Lv Livermorium Br Bromine I Iodine 85 (210) At Astatine 117 (293) Kr Krypton Xe Xenon 86 (222) Rn Radon 118 (294) 118 Lanthanides Actinides Ce Cerium Th Thorium Pr Praseodymium Pa Protactinium Nd Neodymium U Uranium 61 (145) Pm Promethium Np Neptunium Sm Samarium 94 (244) Pu Plutonium Eu Europium 95 (243) Am Americium Gd Gadolinium 96 (247) Cm Curium Tb Terbium 97 (247) Bk Berkelium Dy Dysprosium 98 (251) Cf Californium Ho Holmium 99 (252) Es Einsteinium Er Erbium 100 (257) Fm Fermium Tm Thulium 101 (260) Md Mendelevium Yb Ytterbium 102 (259) No Nobelium Lu Lutetium 103 (262) Lr Lawrencium 2

3 Relativistic Effects Outermost electron electron orbitals orbitals Nucleus Nucleus Innermost electron Innermost orbitals electron orbitals Courtesy of Dr. Megan Bennett 3

4 Fusion Evaporation Reactions Irradiate a target with accelerated particles Atoms fuse into highly excited compound nucleus Compound nucleus de-excites through the emission of nucleons and gamma rays Evaporation Residues (EVRs) also have MeV of kinetic energy γ Projectile Atom Target Atom Evaporation Residue (EVR) 4

5 Turning Theory into Reality Beam From Cyclotron Target MARS Physical Pre-Separator RTC Window Variable Angle Degrader Recoil Transfer Chamber (RTC) Chemistry Experiment Courtesy of Marisa C. Alfonso 5

6 Inside RTC Courtesy of Marisa C. Alfonso 6

7 Counts Experimentation Monitor Po-216 recoils from a Th-228 source with varying potential difference on electrodes RTC Alpha Spectra Po Bi-212 Po Energy (kev) 7

8 Optimization set-up 0 V Mount Th-228 source to source holder Ions travel perpendicular to the equipotential lines (red lines) 420 V 420 V 420V V 60 V 122 V 227V 305 V 8

9 Undesirable Potential Energy Surfaces U(P.E.) X y Try not to create these environments 9

10 Desirable Potential Energy Surfaces Goal : Have EVRs roll down the potential energy surface Gentle slope to extraction nozzle Focusing of ions/evrs prior to first ring electrode and first spherical electrode Lack of radial electric fields 10

11 Scales 0.5 Scale Original Scale 1.55 Scale 0 V 0 V 0 V 210 V 210 V 420 V 420 V 651 V 651 V 30 V 61 V 114V 153 V 60 V 122 V 227V 305 V 93 V 189 V 352 V 473 V V V V 11

12 Net Counts (cps) Experimental Data 29.5 RTC Window/ Inner Chamber/First Ring Optimization Applied Bias (V) Disclaimer: Trend line shown above is to guide the eye. Courtesy of M.C. Alfonso 12

13 Net Counts (cps) Experimental Data Last Ring Optimization Applied Bias (V) Courtesy of M.C. Alfonso 13

14 Net counts (cps) Experimental Data First Spherical Optimization Applied Bias (V) Courtesy of M.C. Alfonso Irregularity and Sensitivity of First Petal: Proximity to last ring (arc discharging at high voltages) Sharp points and uniform electric fields are not compatible 14

15 Net Counts (cps) Experimental Data Third Spherical Optimization Applied Bias (V) Courtesy of M.C. Alfonso 15

16 Net Counts (cps) Experimental Data 30 Fourth Spherical Optimization Applied Bias (V) Courtesy of M.C. Alfonso 16

17 Removed of ring and spherical electrodes and source holder Assuming 3% radon emanation Maximum count rate attained : 30 cps Highest experimental count rate : 21 cps Extraction efficiency up to 70% Radon Emanation Courtesy of M. C. Alfonso and Stephen Molitor 17

18 Conclusions and Future Endeavors Optimal electrode configuration were observed with the original scale. A range or tolerance on individual electrodes has been determined. Extraction efficiency up to 70% Future Work Modifications to RTC window Replace Spherical electrodes with RF carpet 18

19 Acknowledgements A genuine thank you goes to Marisa C. Alfonso for training on the RTC and assistance in data analysis. Many thanks and appreciation also to the entire Folden Group, all of whom made this research experience enjoyable and, most importantly, possible. And of course, a special thanks to the NSF PHY grant for funding this REU. 19