n-3He Experiment: overview and updates

Christopher CrawfordUniversity of Kentucky

n-3He Collaboration Meeting

ORNL, TN 2010-10-16

Outline

Introduction• n+3He reaction

Theoretical advances• Viviani – full 4-body calc.• Gudkov – reaction theory

Experimental update• Experimental setup• MC simulations• Statistical sensitivity• Systematic errors• Transverse RF spin rotator• 3He target / ion chamber

Management• FnPB approval status• Schedule• Work packages

Madison Spencer

n-3He PV Asymmetry

~ kn very small for low-energy neutrons

- essentially the same asym.- must discriminate between back-to-back proton-triton

S(I):

4He J =0+ resonance

sensitive to EFT couplingor DDH couplings

~10% I=1 contribution(Gerry Hale, qualitative)

A ~ -1–3x10-7 (M. Viviani, PISA)

A ~ -1–4x10-7 (Gudkov)mixing between 0+, 0- resonance

Naïve scaling of p-p scattering at 22.5 MeV: A ~ 5x10-8

PV observables:

19.81520.578

Tilley, Weller, Hale, Nucl. Phys. A541, 1 (1992)

nn + nn pp ppnn ppnn +pp nn pp

nnpp

Theoretical calculations – progress

Vladimir Gudkov (USC) PV A = -(1 – 4)£10-7

• PV reaction theory (to be submitted)

Gerry Hale (LANL) PC Ay(90±) = -1.7±0.3£10-6

• R matrix calculation of PC asymmetry,nuclear structure , and resonance properties

Anna Hayes (LANL)• No-core shell model calculation with AV18 potential, etc.

Michele Viviani et al. (INFN Pisa) PV A = -(.944 – 2.48)£10-

7

• full 4-body calculation of scattering wave function• calculation of asymmetry within DDH framework• progress on calculation of EFT low energy coefficients• Viviani, Schiavilla, Girlanda, Kievsky, Marcucci, arXiv:1007.2052 (nucl-th)

status: submitted to PRC

Extraction of DDH couplings

np A nD A n3He Ap np n pp Az p Az

f-0.11 0.92 -0.18 -3.12 -0.97 -0.34

h0 -0.50 -0.14 -0. 23 -0.32 0.08 0.14

h1 -0.001 0.10 0.027 0.11 0.08 0.05

h2 0.05 0.0012 -0.25 0.03

h0 -0.16 -0.13 -0. 23 -0.22 -0.07 0.06

h1 -0.003 -0.002 0.05 0.22 0.07 0.06

n-3He: M. Viviani (PISA)

(preliminary)

dA=1x10-8

dA=1x10-8

http://arXiv.org/abs/1007.2052

Sensitivity to DDH couplings

NN-potentials:• AV18• AV18/UIX• N3LO• N3LO/N2LO

Pion-full EFT calculation?

10 Gausssolenoid

RF spinrotator

3He target /ion chamber

supermirrorbender polarizer

(transverse)

FnPB coldneutron guide

3He BeamMonitor transition field

(not shown)

FNPB n-3He

Experimental setup

longitudinal holding field – suppressed PC asymmetry

RF spin flipper – negligible spin-dependent neutron velocity

3He ion chamber – both target and detector

MC Simulations

Two independent simulations:1. a code based on GEANT42. a stand-alone code

including wire correlations

• Ionization at each wire plane averaged over:1. neutron beam phase space2. capture distribution3. ionization distribution (z)4. uniform distribution of proton angles

cos n¢kp/kp

• Used to calculate detector efficiency (effective statistics / neutron flux)

MC Simulations – Results

Majority of neutron captures occur at the very front of chamber• Self-normalization of beam fluctuations• Reduction in sensitivity to A

Statistical Sensitivity

N = 2.2£1010 n/s flux (chopped) x 107 s (4 full months @ 1.4 MW)

P = 96.2% neutron polarization

d = 6 detector efficiency

A/A ~ 5% assuming A=3x10-7

A/A ~ 26% worse case A=5x10-8

Systematics

Beam fluctuations, polarization, RFSF efficiency:

knr ~ 10-5 small for cold neutrons

PC asymmetries minimized with longitudinal polarization

Alignment of field, beam, and chamber: 10 mrad achievable

Unlike NPDG, NDTG: insensitive to gammas (only Compton electrons)

Systematic Error constraints

Mott-Schwinger and parity conserving nuclear asymmetry

Measure longitudinal instead of transverse asymmetry

1) measure the average kn at two different places along the beam using the wire chamber

2) align the B field parallel to kn

3) align the wire planes to be perpendicular to the holding field (same as kn) to 2 degrees by dead reckoning

4) rotate the chamber by 180 degrees about the holding field and measure again to cancel small residuals

Use a magnetic compass which can measure the field direction to 0.1 deg

Transverse RF spin rotator – n3He

extension of NPDGamma design• P-N Seo et al., Phys. Rev. S.T.

Accel. Beam, vol 11, 084701 (2008)• TEM RF waveguide

new resonator for n-3He experiment• transverse horizontal RF B-field• longitudinal / transverse flipping• no fringe field - 100% efficiency• compact geometry - efficient

- smaller diameter for solenoid• matched to driver electronics

for NPDGamma spin flipper

prototype design• parasitic with similar design for

nEDM guide field near cryostat• fabrication and testing at UKy – 2009

NPDGammawindings

n-3Hewindings

RFSF winding: designed from the inside out

Standard iterative method:Create coils and simulate field.

New technique: start with boundary conditions of the desired B-field, and simulate the winding configuration

1. Use scalar magnetic potential (currents only on boundaries)

2. Simulate intermediate region using FEA with Neumann boundary conditions (Hn)

3. Windings are traced along evenly spaced equipotential lines along the boundary

red - transverse field linesblue - end-cap windings

Magnetostatic calculation with COMSOL

Prototype RFSF

Developed for static nEDM guide field

1% uniformity DC field

3He Target / Ion Chamber – Considerations

Must measure proton asymmetry in current mode directly in target

Can distinguish back-to-backproton and triton by their range• Ep:Et = mt:mp = 3:1• Must let protons range out: rp~5 cm• Neutron mean free path should be < rp/2

Current-mode• HV: 1 – 3 kV• 200 Al wires

3He Target / Ion Chamber – Design

M. Gericke, U. Manitoba

Data Acquisition

Requirements similar to NPDGamma• 16 bit resolution, slow 100 kHz• Simultaneous external triggering (precise timing)

High channel density: 20 x 19 channels or less• Driven by the size of the chamber and proton range• Simultaneous measurement of AL, AT

• Data rate ~10x higher than NPDGamma

VME-based system• Groups of 4 IP modules mounted on CPU processors

for data reduction with direct access to RAID disk

Projected schedule – old

Jan 2011 – Jul 2012• NPDGamma data-taking

Aug 2011 – Dec 2011• Construction of solenoid• Test of field uniformity,

alignment procedures

Aug 2012 – Dec 2012• Installation at FnPB• Commissioning

Jan 2013 – Dec 2013• 3He data-taking

Jan 2011 – May 2011• Construction of new RFSF

resonator at UKy• Construction of 3He ion

chamber at Univ. Manitoba• DAQ electronics and software

production at Univ. Kentucky

May 2011, May 2012• test RFSF, 3He chamber, and

DAQ at LANSCE FP12

window of opportunity forthe n-3He experiment between NPDGamma and Nab

ORNL Offsite

Work Packages

Theory - Michele Viviani

MC Simulations - Michael Gericke / ?

Polarimetry - Stefan Baessler / Matthew Musgrave

Beam Monitor - Rob Mahurin

Alignment - David Bowman / Geoff Greene

Field Calculation - Septimiu Balascuta

Solenoid / fieldmap - Libertad Baron Palos

Transition, trim coil - Pil-Neyo Seo

RFSF - Chris Crawford

Target / detector - Michael Gericke

Preamps - Michael Gericke / ?

DAQ - Nadia Fomin / Chris Crawford

Analysis - Nadia Fomin / Chris Crawford

System integration/CAD - Seppo?

Rad. Shielding / Tritium - John Calarco

Organization

Collaboration meetings after NPDG meetings

Regular phone conferences: ~monthly

Collaboration email list: n3he@pa.uky.edu

PRAC in December: submit request for beam time

Installation target date: July 2012