The n-3He Experiment

Christopher CrawfordUniversity of Kentucky

for the n-3He Collaboration

FnPB PRAC

ORNL, TN 2013-01-23

Outline

Physics• Reaction & observable• EFT calculation• Statistical sensitivity• Systematic effects

Experimental design• Experimental setup• Installation at FnPB• Commission & run plan• ES&H issues

Collaboration• Organization / Manpower

WBS subpackages• Neutron beamline• Stand / Alignment• Magnetic field• RF Spin Rotator• Target Chamber• Preamps• Data Acquisition

Project• Timeline• Resources

n-3He PV asymmetry

Sensitive to isoscalar couplings (I=0) of the Hadronic Weak Interaction

Complementary to NPDGamma (I=1)and p-p scattering (I=0 & 2)

Large asymmetry A = 1.15 x 10-7

Viviani, et al., PRC 82, 044001 (2010),

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- 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

Sensitivity matrix for few-body reactions

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

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

10 Gausssolenoid

RF spinrotator

3He target /ion chamber

supermirrorbender polarizer

(transverse)

FnPB coldneutron guide

3He BeamMonitor

FNPB n-3He

Experimental setup

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

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:• neutron beam phase space• capture distribution• ionization distribution (z)• 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

Runtime estimate for n-3He at FnPB

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

P = 96.2% neutron polarization

d = 6 detector efficiency

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

= 1.6 x 10-8

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)

Assembly in the FnPB cave

Commissioning / run plan

ES&H Issues

Radiation much lower than from NPDGamma• IRR will cover 3 activities:

- Front and back beam scans 3He detector + 6Li aperture- Polarimetry 3He polarizer + 3He monitor- Physics data run 3He target/detector

• Beam friendly materials- Aluminum windows transparent to neutrons- 3He, 6Li have large cross section with no γ radiation

• Graduate student will create MCNP model based on NPDG- Will be validated by radiation group

No other safety concerns• No HV, pressure, vacuum, cryogenics, ladders, …

n-3He collaboration

Spokespersons D. Bowman, M. Gericke, C. Crawford

Local Project Manager S. Penttila

Project Engineer Rick Allen

Work Subpackage Leaders M. Gericke Beam monitors

G. Greene Polarimetry

L. Barrón Magnetic fields

C. Crawford Spin rotator

M. Gericke Target chamber

J. Hamblen Preamplifiers

I. Novikov Data acquisition

D. Bowman Alignment

J. Calarco Shielding

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

Transverse RF spin rotator

Resonant RF spin rotator• P-N Seo et al., Phys. Rev. S.T.

Accel. Beam 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 outside

minimizes RF leaked outside SR• 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

field linesend cap windings

NPDGammawindings

n-3Hewindings

Inner / outer coil design

Windings calculated using scalar potential• Uniform transverse RF field inside• Zero leakage field enforced by B.C.’s• Copper wires run along equipotentials

1. Inner region:

2. Intermediate:

3. Outer region:

4:1 inside / outside winding ratio• By choosing

appropriate radii• Perfect cos theta

windings inside & out• 48 inner loops of

18 AWG wire

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

Progress & Schedule

Design completed in 2011

Resonator machined except wire grooves

March 2013:Finish machining

May 2013:Finish winding

September 2013:RF field map

November 2013:Test with preamps and DAQ system

Target Chamber

Chamber design finished in 2010• delivered to U. of Manitoba, Fall 2010

All aluminum except for the knife edges.• 4 feedthrough ports (200 readout channels)• 2 HV ports + 2 gas inlets/outlets • 12 inch Conflat aluminum windows (0.9 mm thick).

Frame Design and Construction

Chamber frame design finished in 2012

Received 50 Macor wire frames (up to 25 signal and 25 HV) $30K

Final feature machining planned for early this year at UT shop.

Platinum-Gold thick film wire solder pads on Macor to be completed early this year by Hybrid Sources Inc..

Frame Assembly and Signal Readout

The frame mounting structure is designed• pieces will be ordered in the spring

Two options for frame mounting: • Mount into exit flange with threaded rods • Insert into existing exit window flange

Signal readout via circuit board traces• Single HV connections• Guide wires to feedthroughs with PMT-

inspired stand-offs and ceramic beads

Target Chamber Assembly Schedule

February 2013: Have test frame finished by Hybrid Sources and verify measurements.

March 2013: Complete feature machining at UT shop.

April 2013: Order remaining parts for frame assembly and feedthroughs.

June-July 2013: Completed solder pad deposition by Hybrid Sources.

October 2013: Complete chamber assembly

December 2013: Testwith RFSF and DAQ

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

Equipment summary

FnPB / NPDG hardware• 3He beam monitor• SM polarizer• Beam position monitor• Radiation shielding• Pb shield walls• Beam Stop

New equipment• Longitudinal field solenoid mounted on stand• Longitudinal RFSF resonator mounted in solenoid• 3He target/ion chamber mounted in solenoid• Preamps mounted on target• Data acquisition system + RAID storage

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

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

Resources

All equipment funded except Preamp, DAQ, RAID ($117k)• UNAM: (CONACYT $31k) Solenoid and support stand• U. Kentucky: (NSF $23k) RF spin rotator• U. Manitoba: (NSERC $111k) Target chamber

Minimal utilization of SNS crafts• Most equipment mounted on single support structure,

staged in the EDM building, craned onto NPDG det. support• 3D solid model will be drafted by graduate (Mark McCrea),

reviewed by SNS engineer, and incorporated into SNS model• MCNP radiation simulation will created by UKy graduate,

validated by radiation group• Machining will be done at university shops• Alignment is relative to beam scan

Total P-Division operations budget request ($200k)• $117k for DAQ + $83k for Engineering/Radiation/Craft support• See budget spreadsheet for details

Standing in between elephants