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.
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
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
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
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
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
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
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
Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
Proton Asymmetry in Chamber
~n +3He → p + T + 765keV
neutron proton TritonCharge Collection
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.
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
Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
Target Frames
1/4” thick macor ceramic
Signal Frame
• 9 wires
HV Frame
• 8 wires
Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
Assembled Frame Stack
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
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
Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
Mounting Housing on Frame Stack
Introduction Motivation Experiment Setup Ion Chamber Assembly Current Status
Housing In Place
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
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)
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