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

“Heavy” interest in Gas Stopper

2

113

113 (284)

115

115 (288)

117

117 (293)

118

118 (294)

Ce Cerium

58 140.12

Lanthanides

Th Thorium

90 232.04

Actinides

Pr Praseodymium

59 140.91

Pa Protactinium

91 231.04

Nd Neodymium

60 144.24

U Uranium

92 238.03

Pm Promethium

61 (145)

Np Neptunium

93 237.05

Sm Samarium

62 150.40

Pu Plutonium

94 (244)

Eu Europium

63 151.96

Am Americium

95 (243)

Gd Gadolinium

64 157.25

Cm Curium

96 (247)

Tb Terbium

65 158.93

Bk Berkelium

97 (247)

Dy Dysprosium

66 162.50

Cf Californium

98 (251)

Ho Holmium

67 164.93

Es Einsteinium

99 (252)

Er Erbium

68 167.93

Fm Fermium

100 (257)

Tm Thulium

69 168.93

Md Mendelevium

101 (260)

Yb Ytterbium

70 173.04

No Nobelium

102 (259)

Lu Lutetium

71 174.97

Lr Lawrencium

103 (262)

Rf Rutherfordium

104 (261)

Ac Actinium

89 227.03

Db Dubnium

105 (262)

Sg Seaborgium

106 (266)

Bh Bohrium

107 (262)

Hs Hassium

108 (265)

Mt Meitnerium

109 (266)

Ds Darmstadtium

110 (271)

Rg Roentgenium

111 (272) Cn Copernicium

112 (277)

Fl Flerovium

114 (288)

Lv Livermorium

116 (292)

H Hydrogen

1 1.01

Li Lithium

3 6.94

Na Sodium

11 22.99

K Potassium

19 39.10

Rb Rubidium

37 85.47

Cs Cesium

55 132.91

Fr Francium

87 (223)

Be Beryllium

4 9.01

Mg Magnesium

12 24.31

Ca Calcium

20 40.08

Sr Strontium

38 87.62

Ba Barium

56 137.33

Ra Radium

88 226.03

Sc Scandium

21 44.96

Y Yttrium

39 88.91

Ti Titanium

22 47.90

Zr Zirconium

40 91.22

Hf Hafnium

72 178.49

La Lanthanum

57 138.91

V Vanadium

23 50.94

Nb Niobium

41 92.91

Ta Tantalum

73 180.85

Cr Chromium

24 51.996

Mo Molybdenum

42 95.94

W Tungsten

74 183.85

Mn Manganese

25 54.94

Tc Technetium

43 (98)

Re Rhenium

75 186.21

Fe Manganese

26 55.85

Ru Ruthenium

44 101.7

Os Osmium

76 190.20

Co Cobalt

27 58.93

Rh Rhodium

45 102.91

Ir Iridium

77 192.22

Ni Nickel

28 58.70

Pd Palladium

46 106.40

Pt Platinum

78 195.09

Cu Copper

29 63.55

Ag Silver

47 107.87

Au Gold

79 196.97

Zn Zinc

30 65.37

Cd Cadmium

48 112.41

Hg Mercury

80 200.59

Ga Gallium

31 69.72

In Indium

49 114.82

Tl Thallium

81 204.37

B Boron

5 10.81

Al Aluminium

13 26.98

Ge Germanium

32 72.59

Sn Tin

50 118.69

Pb Lead

82 207.19

C Carbon

6 12.01

Si Silicon

14 28.09

As Arsenic

33 74.92

Sb Antimony

51 121.75

Bi Bismuth

83 208.98

N Nitrogen

7 14.01

P Phosphorus

15 30.97

He Helium

2 4.003

O Oxygen

8 15.999

S Sulfur

16 32.06

Se Selenium

34 78.96

Te Tellurium

52 127.60

Po Polonium

84 (209)

F Fluorine

9 18.998

Cl Chlorine

17 35.45

Br Bromine

35 79.90

At Astatine

85 (210)

I Iodine

53 126.90

Ne Neon

10 20.18

Ar Argon

18 39.95

Kr Krypton

36 83.80

Rn Radon

86 (222)

Xe Xenon

54 131.30

Relativistic Effects

Nucleus

Innermost electron orbitals

Outermost electron orbitals

Nucleus

Innermost electron orbitals

Outermost electron orbitals

3 Courtesy of Dr. Megan Bennett

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 30 -50 MeV of kinetic energy

4

γ

Projectile Atom

Target Atom

Evaporation Residue (EVR)

Turning Theory into Reality

Beam From Cyclotron Target

MARS Physical Pre-Separator

Variable Angle Degrader

RTC Window

Recoil Transfer Chamber (RTC)

Chemistry Experiment

5 Courtesy of Marisa C. Alfonso

Inside RTC

6 Courtesy of Marisa C. Alfonso

Experimentation

Monitor Po-216 recoils from a Th-228 source with varying potential difference on electrodes

0

50

100

150

200

250

300

350

400

450

500

5000 6000 7000 8000 9000 10000

Co

un

ts

Energy (keV)

RTC Alpha Spectra

7

Po-216

Po-212 Bi-212

http://www.ortec-online.com/Solutions/RadiationDetectors/silicon-charged-particle-detectors.aspx

Optimization set-up

• Mount Th-228 source to source holder

• Ions travel perpendicular to the equipotential lines (red lines)

420 V

420V - 319 V

60 V 122 V 227V 305 V

420 V

0 V

8

Undesirable Potential Energy Surfaces

Try not to create these environments 9

X y

U(P.E.)

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

Scales

0.5 Scale Original Scale 1.55 Scale

420 V

420- 319 V

60 V 122 V 227V 305 V

420 V

0 V

210 V

210 – 170 V

30 V 61 V 114V 153 V

210 V

0 V

651 V

651- 496 V

93 V 189 V 352 V 473 V

651 V

0 V

11

Experimental Data

12

-0.5

4.5

9.5

14.5

19.5

24.5

29.5

0 200 400 600 800 1000

Ne

t C

ou

nts

(cp

s)

Applied Bias (V)

RTC Window/ Inner Chamber/First Ring Optimization

Courtesy of M.C. Alfonso Disclaimer: Trend line shown above is to guide the eye.

Experimental Data

13

0

5

10

15

20

25

30

0 100 200 300 400 500 600

Ne

t C

ou

nts

(cp

s)

Applied Bias (V)

Last Ring Optimization

Courtesy of M.C. Alfonso

Experimental Data

14

0

5

10

15

20

25

30

0 100 200 300 400 500 600

Ne

t co

un

ts (

cps)

Applied Bias (V)

First Spherical Optimization

Irregularity and Sensitivity of First Petal: • Proximity to last ring (arc discharging at high voltages) • Sharp points and uniform electric fields are not compatible

Courtesy of M.C. Alfonso

Experimental Data

15

-0.5

4.5

9.5

14.5

19.5

24.5

-100 100 300 500 700

Ne

t C

ou

nts

(cp

s)

Applied Bias (V)

Third Spherical Optimization

Courtesy of M.C. Alfonso

Experimental Data

16

0

5

10

15

20

25

30

-400 -300 -200 -100 0 100 200 300 400

Ne

t C

ou

nts

(cp

s)

Applied Bias (V)

Fourth Spherical Optimization

Courtesy of M.C. Alfonso

Radon Emanation

• 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%

17

Courtesy of M. C. Alfonso and Stephen Molitor

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

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-1004780 grant for funding this REU.

19