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Introduction Motivation Experiment Setup Experiment Parts Summary
The n3He Experiment: Current Status
for the n3He CollaborationMark McCrea
University of Manitoba
October 11, 2014
DNP 2014 Hawaii
Introduction Motivation Experiment Setup Experiment Parts Summary
The n3He Experiment: Current Status
• Motivation for n3He
• n3He Setup• n3He Parts
• Target Chamber• Preamps• ADC• Spin Flipper• Collimator
• Beam Scan
Introduction Motivation Experiment Setup Experiment Parts Summary
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
The asymmetry is expected to be small around 10−7 and out goalis to measure it to 2× 10−8.
Introduction Motivation Experiment Setup Experiment Parts Summary
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 Experiment Parts Summary
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 pθs,~k
T
Parity Transformed:
Beamn3Hep
θs,~k
T
Spin Flipped:
Beam n 3He p
θs,~k
T
Introduction Motivation Experiment Setup Experiment Parts Summary
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 Experiment Parts Summary
n3He Schematic Diagram in FnPB
Biological Shielding
NeutronGuide
C1 C2
M1 SMP RFSF
Collimator
3He Target/Detector
HF Solendoid
Introduction Motivation Experiment Setup Experiment Parts Summary
n3He Target/Detector Chamber
Beam
HVSignal
17 HV Frames with 8 wires each16 signal Frames with 9 wires eachHelium-3 Fill Gas
Introduction Motivation Experiment Setup Experiment Parts Summary
Proton Asymmetry in Chamber
~n +3He → p + T + 765keV
neutron proton TritonCharge Collection
Introduction Motivation Experiment Setup Experiment Parts Summary
Frame Stack Assembly
• 33 wire planes
• Machined from macorceramic
• 3 point mount betweenplanes
• 144 signal wires readoutindividually
• Teflon and Kapton used forHV shielding
• Kapton Insulated ribboncable used to connect tosignal feed thrus
Introduction Motivation Experiment Setup Experiment Parts Summary
Chamber Assembly
• 1mm aluminum windows
• 4 signal feed thrus
• 2 gas feed thrus
• 2 HV feed thrus
• Helium Leak Checked at10e-10 mBar l/s
• HV Tested to 1100V inHe-4
• 4 point stand allows roll,pitch, yaw, and heightadjustments
Introduction Motivation Experiment Setup Experiment Parts Summary
Signal Preamps
• 4 preamp boards
• 36 channels/board
• plugs directly to chamberfeed thru
• 44 pin plugs out to ADC
• Forced air cooling tocontrol temperature
• testing of preampperformance with chamberunderway.
Introduction Motivation Experiment Setup Experiment Parts Summary
Delta Sigma ADC from d-tAqc Solutions
• current to voltage preamps
• 24 bit resolution
• Two 24 channel inputs
• 5 DAQs to be used
• 4 for chamber signalreadouts
• 1 for other signals
• Has small instrumentalasymmetries ∼ 10−10
Introduction Motivation Experiment Setup Experiment Parts Summary
Magnetic Holding Fielding Coils
Two sets of magnetic holding field are present that can be used tomaintain a transverse or longitudinal neutron polarization.
Introduction Motivation Experiment Setup Experiment Parts Summary
Radio Frequency Spin Flipper
• Used to flip neutron spin ina sequence to controlsystematic effects.
• Constructed with doubleCosine-Theta coils
• homogeneous internal field
• near zero external field willnot interfere with othercomponents
• Electrical testing iscompleted
Introduction Motivation Experiment Setup Experiment Parts Summary
4 Jaw Collimator
• Collimator used to controlbeam area
• Li plastic over Cadmiummetal
• 4 jaws are independentlyadjustable
Introduction Motivation Experiment Setup Experiment Parts Summary
Neutron Beam Scan
• Experiment componentsneeds to be aligned tobeam center and direction.
• Two xy tables will be usedto scan for beam center
• Laser system used toreference centers
• Scanner hardwareassembled
• Control software in progress
Introduction Motivation Experiment Setup Experiment Parts Summary
Summary
• Magnetic Field Coils in Place
• Spin Flipper Assembled• Electrical Testing Completed
• Collimator Assembled
• Chamber Assembled• HV testing complete• Helium leak testing passed
• Chamber Being Tested with preamps and ADC
• Magnetic Field uniformity testing underway
• Neutron beam scan to find centroid planned
• Before end of year expect to see neutrons on target.
Introduction Motivation Experiment Setup Experiment Parts Summary
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
• Carlos Olguin
Universidad NacionalAutonoma de Mexico
• 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
• Eric Plemons
University of Tennesseeat Chattanooga
• Josh Hamblen
• Caleb Wickersham
University of Virginia
• S. Baessler
