Overview of the n3He Experiment and Target Chamber Mark McCrea - - PowerPoint PPT Presentation

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Overview of the n3He Experiment and Target Chamber Mark McCrea - - PowerPoint PPT Presentation

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Overview of the n3He Experiment and Target Chamber Mark McCrea University of Manitoba for the n3He Collaboration January 30, 2017 1 / 21 n3He Introduction The n3He experimental goal is to make a high precision measurement of the parity

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SLIDE 1

Overview of the n3He Experiment and Target Chamber

Mark McCrea University of Manitoba for the n3He Collaboration January 30, 2017

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SLIDE 2

n3He Introduction

The n3He experimental goal is to make a high precision measurement of the parity violating directional asymmetry in the proton emission direction from the reaction

  • n +3He → p + T + 765keV

The asymmetry is expected to be small, of order 10−7, and our goal is to measure it to 2 × 10−8.

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SLIDE 3

Theoretical Motivation

u d d u d d u d d u d d ? Uncertain HWI N N N N PC Strong PV Weak π, ρ, ω DDH Parameterization DDH Meson Exchange Parameters: Opv = a1

πh1 π + a0 ρh0 ρ + a1 ρh1 ρ + a2 ρh2 ρ + a0 ωh0 ω + a1 ωh1 ω + a1′ ω h1′ ω

q q q q g Strong Interaction q q q q Z 0,W ± Weak Interaction

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SLIDE 4

FnPB Schematic

  • Located at the Oak Ridge

National Laboratory in Tennessee

  • 60 Hertz pulsed spallation

source

  • n3He was located at the

FnPB

  • 20K liquid hydrogen

moderator for cold neutron beam lines

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SLIDE 5

n3He Schematic Diagram

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SLIDE 6

Neutron Pulse

time(ms) 16.6 33.3 50 66.6 83.3 100 116 133 m1(V) 0.05 0.1 0.15 0.2 0.25 0.3 0.35

Unchopped Chopped

time(ms) 16.6 33.3 50.0 66.6 83.3 100 116 133 m1(V) 0.05 0.1 0.15 0.2 0.25 0.3 0.35

1 Hz Pulse 60 Hz Pulses

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SLIDE 7

Target/Detector Chamber

  • 0.47 atm He-3 fill gas
  • 144 signal wires
  • −350 V bias voltage
  • Aluminum housing

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SLIDE 8

n3He Target Chamber Schematic

33.8 25.4 30.4 16 1.9

HV Signal Beam ˆ z ˆ y/ˆ x

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SLIDE 9

Signal Formation in Chamber

  • n +3He → p + T + 765keV

neutron proton Triton Electron Collection Ion Collection Objects are to scale.

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SLIDE 10

Measured Charge Distribution in the Chamber

i h g f e d c b a Wire Letter 2 4 6 8 10 12 14 16 Layer Number 1 10-1 10-2

Beam

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SLIDE 11

Asymmetry Calculation

For an ideal target and detector: Y ↑/↓

k

= I0ǫk(1 ± P cos θAPV ± P sin θAPC) (1) For a real target and detector: Y ↑/↓

k

= I0ǫk(1 ± PGPV APV ± PGPCAPC) (2) S13.00008 : Simulation of ion chamber signals in the n+3Hep+t experiment (next talk) To calculate the asymmetry: APV = 1 PGPV Y ↑ − Y ↓ Y ↑ + Y ↓ (3) J12.00006 : A measurement of the parity violating asymmetry in the neutron capture

  • n 3He at the SNS

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SLIDE 12

Preliminary Asymmetry Results

10 20 30 40 50 60 70 80 90

  • 1.5
  • 1
  • 0.5

0.5 1 1.5 2

  • 6

10 ×

11 x Layer number + wire number Raw asymmetry LR Raw Asymmetry A+ B

J12.00006 : A measurement of the parity violating asymmetry in the neutron capture

  • n 3He at the SNS (January 29)

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SLIDE 13

Summary

  • n3He Data taking completed end of 2015
  • Asymmetry calculations underway
  • We expect to reach the goal statistical accuracy

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SLIDE 14

n3He Collaboration

Arizona State University

  • R. Alarcon
  • D. Blyth

Duke University, Triangle Universities Nuclear Laboratory

  • Pil-Neo Seo

Istituto Nazionale di Fisica Nucleare, Sezione di Pisa

  • Michele Viviani

Oak Ridge National Laboratory

  • David Bowman
  • Vince Cianciolo
  • Paul E. Mueller
  • Seppo Penttil¨

a

  • Jack Thomison
  • T. Tong

University of Indiana

  • Chad Gillis

University of Kentucky

  • Chris Crawford
  • Latiful Kabir
  • Aaron Sprow

Western Kentucky University

  • Ivan Novikov

University of Manitoba

  • Michael Gericke
  • Mark McCrea
  • Carlos Olguin

Universidad Nacional Aut´

  • noma

de M´ exico

  • Libertad Baron
  • Andr´

es Ramirez-Morales University of New Hampshire

  • John Calarco

University of Nevada at Los Vegas

  • A. Barzilov

University of South Carolina

  • Vladimir Gudkov
  • Matthias Schindler
  • Young-Ho Song

University of Tennessee

  • Nadia Fomin
  • Geoff Greene
  • Serpil Kucuker
  • Chris Coppola
  • Chris Hayes
  • Irakli Garishvili
  • Eric Plemmons
  • Noah Birge
  • Connor Gautham
  • Mae Scott

University of Tennessee at Chattanooga

  • Josh Hamblen
  • Jeremy Watts
  • Caleb Wickersham

Middle Tennessee State University

  • Robert Mahurin

University of Virginia

  • Stefan Baessler
  • Septimiu Balascuta

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SLIDE 15

Spare Slides

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SLIDE 16

Parity Transformation

A parity transformation, P inverts the spatial coordinates, inverting polar vectors, such as momentum , P( k) = − k, but not axial vectors, such a spin, P( σ) = σ. Original state:

Beam

  • σn

n

3He

  • kp
  • σn

p

θs,

k

T

Parity transformed:

Beam

  • σn

n

3He

  • kp
  • σn

p

θs,

k

T

Spin flipped:

Beam

  • σn

n

3He

  • kp
  • σn

p

θs,

k

T

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SLIDE 17

FnPB CAD Model

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SLIDE 18

n3He In FnPB

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SLIDE 19

Collimator

  • 4 independent haws
  • Cd and Li-6 neutron absorbing layers used to stop beam

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SLIDE 20

Assembled Frame Stack

  • 17 HV frames
  • 16 signal frames
  • 144 signals to read out
  • 0.02” diameter wires

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SLIDE 21

Chamber Assembly

  • 1mm aluminum windows
  • 4 signal feed thrus
  • 2 gas feed thrus
  • 2 HV feed thrus
  • 0.47 atm He-3 fill gas
  • operated at -350V
  • 4 point kinematic mount allows the

target to be aligned to the magnetic field and neutron beam

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