Geant4 Simulations for the Radon Electric Dipole Moment Search at

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Figure 2.2: Schematic of the prototype on-line noble gas collection apparatus tested at TRIUMF with isotopes of 120 Xe [26]. was then closed to trap the xenon gas in the measurement cell. The trapped radioactive 120 Xe atoms were observed in the measurement cell using high-purity germanium (HPGe) γ-ray detectors. This process of transferring the xenon from the foil to the measurement cell was demonstrated to be greater than 40% efficient [26]. Improvements and adjustments have since been made to the initial prototype design in order to enhance the overall transfer efficiency. In the summer of 2008, improvements in the coldfinger design and nitrogen system resulted in a transfer efficiency greater than 90% using radioactive isotopes of 121,123 Xe [27]. 2.3 Measuring Atomic EDMs High-precision measurements will be necessary in order to search for a non-zero EDM in radon. Magnetic moments in nuclei aremeasured with great sensitivity using 16
NMR techniques, and supplementing standard NMR techniques with a strong electric field provides an excellent method to search for an EDM. The process of measuring an EDM using these techniques begins with polarizing the nuclei. Nuclear spin polarization of noble gases is possible through spin-exchange collisions with optically pumped alkali-metals [28, 29, 30]. This method has been shown to be successful in the polarization of radon isotopes ( 209,223 Rn) at the ISOLDE isotope separator at CERN [31]. Similar polarization studies have been tested and are continuing to be developed for the RnEDM experiment at TRUMF. 2.3.1 Optical Pumping of Rubidium Vapour Alkai-metals are commonly used for optical pumping since they have only one valence electron. This electron can be easily excited with photon wavelengths conveniently in the range where diode lasers are available. The measurement cell in the RnEDM apparatus will contain an optical pumping region, containing natural rubidium ( 85,87 Rb) vapour, radon atoms and roughly 1 atm of N 2 gas. The natural rubidium vapour is the alkali-metal used to polarize the radon nuclei through spinexchange collisions and the N 2 gas acts as a buffer. The natural rubidium ( 85,87 Rb) atoms have odd-A nuclei and therefore have a non-zero nuclear spin (I) which complicates its level structure. To illustrate the process of optical pumping we will first consider a much simpler atom with no nuclear spin. Consider the 4 He + ion, which is similar to the hydrogen atom without the nuclear spin. The electron can be in its ground state (1S 1/2 ), or given enough energy, it can occupy the first excited state (2P 1/2 ). Placing this atom in an external magnetic field will cause the energy levels to spilt, known as the Zeeman effect. This is illustrated in Figure 2.3. Both energy levels have J = 1/2; in the presence of a magnetic field the 17
Page 1 and 2: GEANT4 SIMULATIONS FOR THE RADON EL
Page 3 and 4: Dictated but not read. i
Page 5 and 6: Contents Acknowledgements ii 1 Intr
Page 7 and 8: 4 Results 60 4.1 γ-Ray Spectroscop
Page 9 and 10: List of Figures 1.1 An illustration
Page 11 and 12: Chapter 1 Introduction Thesearchfor
Page 13 and 14: ˆP ր ˆT ց Figure 1.1: An illust
Page 15 and 16: 1.1.1 CP Violation Following the ob
Page 17 and 18: Figure 1.2: Experimental upper limi
Page 19 and 20: Figure 1.3: Illustration of the dou
Page 21 and 22: Chapter 2 RnEDM Experiment at TRIUM
Page 23 and 24: Figure 2.1: A schematic of the ISAC
Page 25: a measurement cell. The RnEDM exper
Page 29 and 30: Occupied Orbitals Fine Structure Hy
Page 31 and 32: energy levels are separated accordi
Page 33 and 34: (σ + ) along the axis of the B fie
Page 35 and 36: atom and absorbed by another. Radia
Page 37 and 38: anaverageof120kHzphotopeakcountrate
Page 39 and 40: Figure 2.7: One GRIFFIN/TIGRESS HPG
Page 41 and 42: (a) One GRIFFIN detector in the HPG
Page 43 and 44: 3.1 Introduction 3.1.1 Previous Wor
Page 45 and 46: energies, branching ratios, emissio
Page 47 and 48: used around the measurement cell in
Page 49 and 50: 3.2.5 Simulated Data Thecodewaswrit
Page 51 and 52: lower its total energy. Internal co
Page 53 and 54: 10000 1000 2 χ red = 1.21 t 1/2 =
Page 55 and 56: as [47] I(E) = G 2π 3 7 c 6 | M i
Page 57 and 58: was to use an average X-ray energy
Page 59 and 60: 1.5 1.4 1.3 1.2 P = 100% P = 75% P
Page 61 and 62: where (a b c d | e f) are Clebsch-G
Page 63 and 64: 2 2 1.5 J i = 5/2, J f = 5/2 J i =
Page 65 and 66: of radius 10 cm, allowing the GRIFF
Page 67 and 68: (a) Screenshot showing the detector
Page 69 and 70: 3.6.2 Output Data and Sort Codes Th
Page 71 and 72: (user-defined option), secondly toa
Page 73 and 74: 30 Absolute Efficiency (%) 25 20 15
Page 75 and 76: 11 10 9 8 7 6 5 4 3 2 1 0 1e+06 Cou
Page 77 and 78:
4.2.1 Multipolarity Effects The sha
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Figure 4.7: The time projections an
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distribution, this average intensit
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Table 4.1: The fit results for the
Page 85 and 86:
12 10 linear regression: y = 0.2243
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15 Linear Counts (e+04) 10 5 0 1e+0
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Chapter 5 Conclusions and Future Di
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simulated given sufficient parent a
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Appendix A Figure A.1: Simulated de
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Figure A.3: Simulated decay scheme
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Figure A.5: Simulated decay scheme
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6 out = (1/(1+∆ˆ2))*(f(k,jf,L1,L
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44 return; 45 end 46 if abs(m) > j
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1 % LegendreP.m 2 function P = Lege
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39 xx(i+1,j+1) = r(i+1,1)*sin((i*re
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11 %warning('m1 + m2 + m3 must equa
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23 end 24 % ////////// 25 j1 = J1;
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33 if L1 == L2 && ∆ == 0 34 title
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Bibliography [1] J. M. Pendlebury a
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[25] P. G. Bricault, M. Dombsky, Je
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[47] RichardA.Dunlap. An introducti
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