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