Systematics of the SNS n-3He Experiment

Christopher CrawfordUniversity of Kentucky

for the n-3He Collaboration

APS April Meeting

Denver, CO, 2013-04-16

Overview – Hadronic Weak Interaction (HWI)

Hadronic

Nuclear

EW

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Nuclear PV

Few-body PV

Viviani et al, PRC 82 (2010), 044001

Wasem, PRC 85 (2012), 022501

2/10

10 Gausssolenoid

RF spinrotator

3He target /ion chamber

supermirrorbender polarizer

(transverse)

FnPB coldneutron guide

3He BeamMonitor

FNPB n-3He

Experimental setup at the FnPB

longitudinal holding field – suppressed PC nuclear asymmetry A=1.7x10-6 (Hales) sn kn x kp suppressed by two small angles

RF spin flipper – negligible spin-dependence of neutron velocity

3He ion chamber – both target and detector

3/10

Asymmetry Measurement – Statistics

Extract physics asymmetry from single-wire spin asymmetries– operating in current-mode: t, pdownstream background

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

including wire correlations

N = 1.5x1010 n/s flux (chopped) x 107 s (116 days)

P = 96.2% neutron polarization

d = 6 detector efficiency

1. 15% measurement in 1 beam cycle (without contingency), assuming Az= 1.15 x 10-7

= 1.6 x 10-8

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Systematic Uncertainties

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 n p -> d ° or n d -> t °, n 3He is very insensitive to gammas (only Compton electrons)

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Transverse RF spin rotator

Resonant RF spin rotator• P-N Seo et al., PRSTAB 11, 084701 (2008)

Properties suitable for n-3He expt.• Transverse horizontal RF B-field• Longitudinal or transverse flipping• No fringe field - 100% efficiency• Real, not eddy currents along

outsideminimizes RF leaked outside

• Doesn’t affect neutron velocity• Compact geometry• Matched to the driver electronics

of the NPDGamma spin flipper

Construction• Development in parallel with similar

design for nEDM neutron guide field• Few-winding prototype built at UKy;

Production RFSF being built now

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Target Ion Chamber

Chamber all aluminum except for the knife edges.• 4 feedthrough ports (153 readout channels)• 2 HV ports + 2 gas inlets/outlets • 12 inch aluminum windows (0.9 mm thick).

Macor wire frames• Platinum-gold thick film wire solder pads

Filled with 1 atm of 3He

7/10

Assembly in the FnPB cave

8/10

Commissioning / run plan

9/10

Summary n-3He collaboration

Last measurement for the a characterization of the Hadronic Weak Interaction

15% projected uncertainty

will be the most accurateHWI experiment in afew-body system

Scheduled FnPB beam time June 2014 – Dec 2015

10/10

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- 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

Viviani, Schiavilla, Girlanda, Kievsky, Marcucci, PRC 82, 044001 (2010) Girlanda, Kievsky, Marcucci, Pastore, Schiavilla, Viviani, PRL 105 232502 (2010)

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

• PV reaction theory Gudkov, PRC 82, 065502 (2010)

Michele Viviani et al. (INFN Pisa) PV VNNEFT, a0 – a5

Viviani, PAVI (2011), preliminary

EFT NN potential revisited to NNLO

Viviani et al., preliminary (PAVI 11)• (a) Q0 h1

π gπ(r)

• (CT) Q1 C1,2,3,4,5 Z(r)

• (b,c) Q2 zero• (e,h) Q2 renorm./absorb in h1

π

• (d), Q2 h1π+C3 (triangle) L(r)

• (f,g,g’) Q2 h1π (box) H(r)+L(r)

Azn3He (prelim) using N3LO (Emtem & Macheleidt) + 3N N2LO (Navratil)

Λ = 500: a0=-0.15 a1=.026 a2=.021 a3=0.11 a4=-.043 a5=-.0022

Sensitivity matrix for few-body reactions

Contribution: 1.15 0.087 1.55 – -.002 -0.47 –

Neutron beamline

Scope: • FnPB guide, polarizer, beam monitors (existing, NPDG)• Beam profile scanners, polarimetry

Status: • All equipment exists except aluminum aperture / crosshair• Must design shielding to accommodate xy-scanner• Must design mount for 3He analyzer

Alignment

Scope: • Aperture / crosshairs for beam scan• Support stand and xy-adjustment for theodolite• Alignment V-block for trimming B-field• Optical system and adjustable mount for target

Progress: • Conceptual design

Magnetic field

Scope: • Magnetic field simulations to verity adiabatic spin rotation and uniformity• Design and construct longitudinal solenoid and frame• Map fields at UNAM before delivery to SNS

Status: • Conceptual design, preliminary calculations indicate adiabaticity

15 coils, 15 cm apart, 35 cm radius, 150 A turns

Electrical specifications – compatible with NPDG

Holding field:

Resonant frequency:

Inductance: 4.5 mH

Capacitance: 7.5 nF

Resistance: 5.1 Ω

Maximum voltage:

Stored energy:

Dissipated power:

Quality factor: Q=151

R&D: test 3 winding patterns with same field in high-frequency limitINNER INNER/OUTER OUTER

easiest to wind no eddy currents no copper in beam

Preamps

Scope• 4 boxes with 32 channels each $41k• Design and fabricate circuit, and mechanical enclosure• Connector to Target Chamber port and cabling to DAQ module

Status – on critical path – need resources soon!• Have preliminary design (from NPDG preamps)• Must modify circuit for n-3He (high channel density, 10x larger signal)

Data Acquisition

Scope: • 128 channels of 16/24 bit ADC, > 60 KS/s $51k

data acquisition software; RAID storage array $25k

Status – need resources soon to begin development and testing! • selected candidate system D-tAcq CQ196CPCI-96-500• Each card 96 sim. channels + antialiasing filters + FPGA signal proc.

runs Linux on 400MHz XScale processor with Gigabit Ethernet• Inexpensive cPCI chassis used only for power and cooling• DAQ software included with hardware – turn-key system• awaiting funds to purchase and test system

Timeline

Construction of subsystems in parallel• Will be ready for beam at beginning of cycle Aug 2014• Critical path: preamp design and construction (possibly DAQ)• Will stage experiment in EDM building and perform

dry run of field map, beam map, and alignment procedures• See Gantt chart for details

Milestones• 2014-04-21 Begin assembly and testing in EDM building• 2014-07-18 Begin installation in FnPB cave• 2014-10-27 IRR – begin commissioning phase• 2015-02-?? Physics data taking at beginning of beam cycle

Time budget• 76 days commissioning (all equipment pre-assembled)• 15 days PC transverse asymmetry 1.7 x 10-6 ± 0.5 x 10-7

• 116 days PV longitudinal asymmetry 1.15 x 10-7 ± 1.6 x 10-8