Shannon Fogwell Hoogerheide Lepton Moments 2014 July 21 2014 Acknowledgements 2 Prof Gerald Gabrielse Elise Novitski PhD in progress Joshua Dorr 2013 Shannon Fogwell ID: 370059
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Slide1
Positrons for a New Measurement of the Positron Magnetic Moment
Shannon Fogwell HoogerheideLepton Moments 2014July 21, 2014Slide2
Acknowledgements
2
Prof. Gerald
Gabrielse
Elise
Novitski
(PhD in progress…)Joshua Dorr (2013)Shannon Fogwell Hoogerheide (2013)
New ApparatusRetractable Positron SourcePositron LoadingSlide3
2008 Electron Magnetic Moment Measurement
3
Best measurement of electron
g
-value:
→ Most precise determination of fine
structure constant:
→Most precise test of Standard Model and QED (with independent α)However, best measurement of positron g-value is only 4.3 ppt.This limits test of CPT violation in lepton systems:
Could be improved by 15x with 0.28
ppt
positron measurement
T. Aoyama, M. Hayakawa, T. Kinoshita, and M.
Nio
, Phys. Rev.
Lett
. 109, 111808 (2012)
D
.
Hanneke
, S.
Fogwell
, and G.
Gabrielse
,
Phys. Rev.
Lett
.
100
, 120801 (2008)
R.
Bouchendira
et.al.
Phys. Rev.
Lett
.
106,
080801 (2011)
R. Van
Dyck
et.al.
Phys. Rev.
Lett
.
59
. 26 (1987)Slide4
2008 Measurement
4
Best measurement of electron
g
-value:
→ Most precise determination of fine
structure constant:
→Most precise test of QED with independent αHowever, best measurement of positron g-value is only 4.3 ppt.This limits test of CPT violation in lepton systems:
Could be improved by 15x with 0.28
ppt
positron measurement
T. Aoyama, M. Hayakawa, T. Kinoshita, and M.
Nio
, Phys. Rev.
Lett
. 109, 111808 (2012)
D
.
Hanneke
, S.
Fogwell
, and G.
Gabrielse
,
Phys. Rev.
Lett
.
100, 120801 (2008)R. Bouchendira et.al. Phys. Rev. Lett. 106, 080801 (2011)R. Van Dyck et.al. Phys. Rev. Lett. 59. 26 (1987)
Solution: New and Improved Apparatus with Positron Loading Capability!Slide5
5
Magnetic Field:
6 T Superconducting Solenoid
Electric Field:
Silver trap electrodes
Axial
Magnetron
CyclotronSlide6
6
Magnetic Field:
6 T Superconducting Solenoid
Electric Field:
Silver trap electrodes
Dilution Refrigerator:
Quantum measurement
h
n
c
/
k
B
≈
7.2 K
Run at 100
mK
<n> <<1Slide7
New Apparatus
7
2.5 cmSlide8
Advantages of the New Apparatus
Mechanical Stability
8Slide9
Advantages of the New Apparatus
Mechanical Stability
9
Challenge:
Lowering warm apparatus straight into a liquid helium
dewar
without quenching the magnetSlide10
Cooldown Procedure
10
4-5 hour cooling time
Sliding seal plus glove bagSlide11
Cooldown Procedure
11
4-5 hour cooling time
Sliding seal plus glove bagSlide12
Advantages of the New Apparatus
Mechanical StabilityRadial Centering
12Slide13
Advantages of the New Apparatus
Mechanical StabilityRadial CenteringImproved Magnetic Shielding6x More Cooling
Power at 100 mK (300 μW vs 50 μW)
More Room for Electronics
13Slide14
Advantages of the New Apparatus
Mechanical StabilityRadial CenteringImproved Magnetic Shielding6x More Cooling Power at 100 mK (300 μW vs 50 μW)
More Room for ElectronicsSmaller Magnetic BottleNarrower resonance lines
14Slide15
Advantages of the New Apparatus
Mechanical StabilityRadial CenteringImproved Magnetic Shielding6x More Cooling Power at 100 mK (300 μW vs 50 μW)
More Room for ElectronicsSmaller Magnetic BottleTrap Cavity Mode DesignAllows for new techniques (discussed in next talk)
15Slide16
Advantages of the New Apparatus
Mechanical StabilityRadial CenteringImproved Magnetic Shielding6x More Cooling Power at 100 mK (300 μW vs 50 μW)
More Room for ElectronicsSmaller Magnetic BottleTrap Cavity Mode DesignPositron Source Access
16Slide17
Positron Source
Source: Radioactive 22Na capsuleRequirements:Smallest source activity
possibleSafety considerationsMinimal disruption to high-precision environmentReasonable loading rate
17Slide18
Positron Source Requirements
Smallest source activity possibleReasonable loading rate
18
Solution:
Positron Loading TrapSlide19
Positron Source Requirements
Smallest source activity possibleReasonable loading rateRetractable source
19Slide20
Positron Source Requirements
Smallest source activity possibleReasonable loading rateRetractable sourceAdvantages: Preserve high-precision environment for measurement
Able to easily remove source from apparatus if desired
20Slide21
Positron Source Requirements
Smallest source activity possibleReasonable loading rateRetractable sourceAdvantages: Preserve high-precision environment for measurement
Able to easily remove source from apparatus if desiredChallenges: Move source at 100 mKMinimize heat load on Dil fridge: Dil
fridge can only handle ~300
uW
at 100 mK – a 1/32” (0.8 mm) hole at 300 K radiates ~200 uW at 100 mK!
21Slide22
Retractable Positron Source
22
Take great care to prevent room temperature thermal radiation from reaching cryogenic environmentSlide23
Retractable Positron Source
23Slide24
Positron Loading Mechanism
24
J. Estrada
et al.
, Phys. Rev. Lett.
84
, 859 (2000)
e
+
Ps*
e
+
e
-Slide25
Comparison of Source Size and Loading Rate
25
Source Size
Loading Rate
Loading Rate/mCi
UW ’81-’87
(resistive damping)
0.5 mCi
0.4 e
+
/min
0.8 e
+
/min/mCi
HU ’94-’95
(resistive damping + RMOD)
10 mCi
12 e
+
/min
1.2 e
+
/min/mCi
HU ’00 (ATRAP)
(TMOD only)
2.5 mCi
420 e
+
/min
170 e
+
/min/mCi
HU ’00 (ATRAP)
(TMOD + RMOD)
2.5 mCi
1700 e
+
/min
670 e
+
/min/mCi
HU ’03 (ATRAP)
(TMOD + RMOD)
75 mCi
3.2x10
4
e
+
/min
420 e
+
/min/mCi
This work
(TMOD only)
.0065 mCi
1-2 e
+
/min
150-300 e
+
/min/mCiSlide26
Comparison of Source Size and Loading Rate
26
Source Size
Loading Rate
Loading Rate/mCi
UW ’81-’87
(resistive damping)
0.5 mCi
0.4 e
+
/min
0.8 e
+
/min/mCi
HU ’94-’95
(resistive damping + RMOD)
10 mCi
12 e
+
/min
1.2 e
+
/min/mCi
HU ’00
(TMOD only)
2.5 mCi
420 e
+
/min
170 e
+
/min/mCi
HU ’00
(TMOD + RMOD)
2.5 mCi
1700 e
+
/min
670 e
+
/min/mCi
HU ’03
(TMOD + RMOD)
75 mCi
3.2x10
4
e
+
/min
420 e
+
/min/mCi
This work
(TMOD only)
.0065 mCi
1-2 e
+
/min
150-300 e
+
/min/mCiSlide27
Loading Potentials
27Slide28
Loading Potentials
28Slide29
Positron Loading Rate
Maximum positron loading rate: 1-2 e+/min for 6.5 μCi source, or 3-5 e+/s/mCiSimilar normalized loading rate
to the 2.5 mCi and 100 mCi sources used to demonstrate positronium loading method3-5 times higher loading rate and 75 times smaller source than used in previous e
+
g-value measurement
29Slide30
Prospects for a New Positron Magnetic Moment Measurement
New high-precision apparatus complete and running wellRobust positron loading demonstratedWork is underway on transferring positrons to the precision trapReady for new (and improved!) measurements (NEXT TALK)
30Slide31
31