progress toward a measurement of hadronic parity violation ...crawford/n3he/mainspace/files/cap 2014...
TRANSCRIPT
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Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
Progress toward a Measurement of HadronicParity Violation in the Capture of Cold Neutrons
on Helium-3
for the n3He CollaborationMark McCrea
University of Manitoba
June 17, 2014
CAP Congress 2014 Sudbury, ON.
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Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
The n3He Experiment: Target Ion Chamber
1 Introduction
2 Motivation
3 Experiment Setup
4 Ion Chamber Assembly
5 Current Status
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Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
n3He Introduction
n3He probes the weak nucleon-nucleon interaction by measuring
the parity violating directional asymmetry between the polarization
direction of the incoming cold neutrons and the direction of the
outgoing protons in the reaction
~n +3He →4He∗ → p + T + 765keV
Beam n 3He pθs,~k
T
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Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
Theoretical Motivation
q
q
q
q
g
Strong Interaction
q
q
q
q
Z 0,W±
Weak Interaction
u d d
u d d
udd
udd
?
Uncertain HWI
N
N
N
N
PC
Strong
PV
Weak
π, ρ, ω
DDH Parameterization
DDH Meson Exchange Parameters:
Opv = a1πh
1π + a0
ρh0ρ + a1
ρh1ρ + a2
ρh2ρ + a0
ωh0ω + a1
ωh1ω
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Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
A Brief Look at ParityUnder a parity transformation P polar vectors such as themomentum transform as
P(~kn)→ −~kn and P(~kp) = −~kpbut axial vectors, such as the neutron spin, remain unchanged
P(~sn)→ ~sn
Orignal State:
Beam n 3He p
θs,~k
T
Parity Transformed:
Beamn3Hep
θs,~k
T
Spin Flipped:
Beam n 3He p
θs,~k
T
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Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
Spallation Neutron Source
• Located at the Oak Ridge National Laboratory (ORNL) inTennessee
• 60 Hertz pulsed spallation source
• n3He will located at the FnPB
• 20K liquid hydrogen moderator for cold neutron beam lines
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Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
n3He Schematic Diagram in FnPB
Biological Shielding
NeutronGuide
C1 C2
M1 SMP RFSF
Collimator
3He Target/Detector
HF Solendoid
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Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
n3He Target/Detector Chamber
Beam
HVSignal
17 HV Frames with 8 wires each16 signal Frames with 9 wires each1 atm. He-3
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Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
Proton Asymmetry in Chamber
~n +3He → p + T + 765keV
neutron proton TritonCharge Collection
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Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
Target CAD Drawing
Frame Stack with signal and HVPCB on mount plate
Chamber exterior with allflanges in place.
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Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
Aluminum Chamber Vessel
• 10” conflat end flanges
• windows are 1mm thick Al
• 4 signal feed thrus
• 2 gas feed thrus
• 2 HV feed thrus
• Al body, SS knife edges
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Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
Target Frames
1/4” thick macor ceramic
Signal Frame
• 9 wires
HV Frame
• 8 wires
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Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
Assembled Frame Stack
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Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
Frame Stack Shielding
• Teflon Shielding on signalboard to stop stray chargecollection
• Teflon on HV to stopunwanted discharge
• Kapton around ends to stopstop unwanted discharge
• Ceramic beads on barewires when possible
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Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
Survey and Alignment
• The position and angle ofthe frame stack inside thehousing needs to be knownto align it to the neutronbeam.
• Faro Arms are 3Dmeasurement devices.
• Position and angle of framestack measured to baseflange
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Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
Mounting Housing on Frame Stack
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Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
Housing In Place
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Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
Chamber Testing
• Helium Leak Checked at10e-10 mBar l/s
• HV leakage testing in Air• 1.5× 10−8 amps at
1400V from HV toground
• HV Testing with He FillGas
• MHV Flange Sparked at580V
• 940V reached afteradditional Kaptonshielding used in MHVfeed thru to preventsparking to its ownground
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Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
Current Status
• n3He Chamber Assembled.
• Initial HV Leakage to ground testing passed
• Initial He leak check passed
Upcoming Tasks:
• Finish HV shielding upgrades (July)
• Fill with He-3 and test with neutrons (August)
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Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
n3He Collaboration
Duke University, TriangleUniversities NuclearLaboratory
• Pil-Neo Seo
Istituto Nazionale diFisica Nucleare, Sezionedi Pisa
• Michele Viviani
Oak Ridge NationalLaboratory
• Seppo Penttil
• David Bowman
• Vince Cianciolo
• Jack Thomison
University of Kentucky
• Chris Crawford
• Latiful Kabir
• Aaron Sprow
Western KentuckyUniversity
• Ivan Novikov
University of Manitoba
• Michael Gericke
• Mark McCrea
• Carlous Olguin
Universidad NacionalAutnoma de Mxico
• Libertad Baron
• Jose Favela
University of NewHampshire
• John Calarco
University of SouthCarolina
• Vladimir Gudkov
• Young-Ho Song
University of Tennessee
• Nadia Fomin
• Geoff Greene
• S. Kucuker
• C. Hayes
• Irakli Garishvili
University of Tennesseeat Chattanooga
• Josh Hamblen
• Caleb Wickersham
University of Virginia
• S. Baessler