Proposal Update: the n- 3 He Parity Violation Experiment Christopher Crawford University of Kentucky for the n- 3 He Collaboration FnPB PRAC Meeting ORNL,

Proposal Update: the n-3He  Parity Violation Experiment

Christopher CrawfordUniversity of Kentucky

for the n-3He Collaboration

FnPB PRAC Meeting

ORNL, TN 2010-12-16

Outline

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

Experimental update• Transverse RF spin rotator• 3He target / ion chamber• Statistical sensitivity - simulations• Systematic errors• Alignment scheme

Management plan• Installation: changes from NPDG• Operation: run time and sensitivity

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 ~ -.3–1x10-7 (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

Gerry Hale (LANL) PC Ay(90) = -1.7 +/- 0.3 x

10-6

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

Michele Viviani et al. (INFN Pisa) PV A = -(.248 – .944)£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, PRC 82, 044001 (2010),

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

• PV reaction theory • Gudkov, PRC (in press)

http://arXiv.org/abs/1007.2052

Sensitivity to DDH couplings

1. Calculation of strong 4-body wave functions • Kohn variational method with hyperspherical functions• No parity mixing in this step: Jπ = 0+, 0-, 1+, 1-

• Tested against n-3He scattering lengths

§ Evaluation of weak <J-|VPV|J+> matrix elements• In terms of DDH potential• EFT calculation in progress

Sensitivity matrix for few-body reactions

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

Transverse RF spin rotator

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 expt.• 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, testing at UKy – 2010

NPDGammawindings

n-3Hewindings

field linesend cap windings

Prototype holding field coil

Developed for static nEDM guide field

1% uniformity DC field

Field map of DSCTC

Prototype RFSF coil

3He Target / Ion Chamber – Design

M. Gericke, U. Manitoba

Custom aluminum CF flanges with SS knife-edges

Macor ceramic frame,Cu wires, 200um diameter

Chamber and flanges have been delivered to U. Manitoba

Construction of frame / wires will be completed in 2011.

Data Acquisition

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

High channel density: ~144 channels• Driven by the size of the chamber and proton range• Data rate ~3x higher than NPDGamma

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

for data reduction with direct access to RAID disk

Alphi Technologies: $36k for 192 channels DAQ + storage

New Detection Scheme under consideration

Strategy: detect higher ion density of triton, not longer range of proton

Both proton and triton range out at Si wafer cell walls

Form asymmetry from ions near each side of cell

Less ions per event, but not differential measurement

σd = 2 (left/right planes) vs. σd = 6 (proton range / absorption length)

Can measure 6Li asymmetry to same level with this technique

-HV -HV -HV -HV -HV -HV

HV

grid

wire

s

Si,

an

od

es

on

ea

ch s

ide

3He gas < 1 cm

baffles

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

Measurement of LANSCE FP12 absolute flux

Measurement of LANSCE FP12 absolute flux

Comparison of statistics at LANSCE FP12

based on: • D. Bowman, technical note, 2010-09-24,• A. Salas-Bacci, technical note, 2010-10-14• Gericke, NIMA 611 239 (2009)

2.68 x 107 n/s cm2 neutron flux at 100 μA, measured with FC

3.5” collimator, 87.6 μA proton current

4966 runs (after cut) x 104/20 Hz

0.88 (air) x 0.90 (Al) x 0.88 (glass) x 0.346 (3He) transmission

0.60 capture in LH2 x 0.3017 geom. factor

0.53 pol. 3He x 0.989 SF eff. / (1+0.25) bkg. Dilution

δA = 1.9 x 10-7 from calc. vs. 2.1 x 10-7 RMS width in Aγ

Runtime estimate for n-3He at FnPB

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

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)

Alignment procedure

Suppression of 1.7 x 10-6 nuclear PC asymmetry• longitudinal polarization: sn . kn x kp doubly suppressed

1. Symmetric detector• Rotate 180 deg about kn during data taking

2. Align B field with detector axis to 1 mrad• Vant-Hull and Henrickson windblown generator• Minimize Bx, By by observing eddy currents in generator

§ Align detector/field with neutron beam to 1 mrad• Perform xy-scans of beam at 2 z-positions before/after target• NPDG: B4C target in beam with CsI detector, 6Li chopper

Scanning beam monitor

B4C target

CsI crystal

6Li Shutter

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 / field map - 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

Installation at FnPB

NPDG equipment:• 3He beam monitor• SM polarizer• Beam position monitor• Radiation shielding• Pb shield walls• Beam Stop

New equipment:• Transition guide field• 4He flight path from SMpol to RFSF (reuse 6Li shielding)• Longitudinal field solenoid mounted on stand• Longitudinal RFSF resonator mounted in solenoid• 3He target/ion chamber mounted in solenoid• Preamps mounted on target• DAQ: single-board computers + ADC modules + RAID array

NPDG electronics:• B-field power supply• RFSF electronics• Trigger electronics• SNS / chopper readout• Fluxgate magnetometers• Computer network

Projected schedule

Jan 2011 – Jul 2012 (beam)• NPDGamma data-taking

July 2012• Stage of stand, solenoid,

RFSF, Ion Chamberin nEDM building

Aug 2012• Installation at FnPB• Field map at FnPB

Sept 2012 (request: 1000 hrs)• Beam axis scans • 3He Polarimetry

Jan 2013 (request: 5000 hrs)• 3He data-taking

Jan 2011 – July 2011• Construction and field mapping

of solenoid at UNAM• Construction and testing of

RFSF resonator at UKy• Assembly of 3He ion chamber

at Univ. Manitoba• DAQ electronics and software

at UKy / UTK / ORNL

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

DAQ at LANSCE FP12

ORNL Offsite

Conclusion

Published 4-body calculation• EFT calculation under way

Experimental progress• Prototype RFSF resonator• Target chamber delivered• Systematics under control

Scheduled to immediately follow NPDG