The n-3He Project

Christopher CrawfordUniversity of Kentucky

for the n-3He Collaboration

n-3He Technical Review

ORNL, TN 2013-01-08

Outline

Experiment design• Physics reaction and

observable• Experimental setup• Installation in the

FnPB cave• Commissioning

and run plan• ES&H issues

Collaboration• Organization• Manpower

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

Timeline

Resources• P-Division needs

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 = 1.3 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

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

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

Magnetic field

Scope: • Magnetic field simulations to verity adiabatic spin rotation and uniformity• Design and construct longitudinal solenoid and frame• Unistructure frame to support RFSR, Target, alignment jigs,

mounts on NPDG detector stand.

Status: • Conceptual design, preliminary calculations indicate adiabaticity

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

Transverse RF spin rotator

Scope:• Design and construct RF resonator• Driving circuit (use NPDG electronics)

Status:• Prototype built and tested, DC current• Final design completed• Al shell & nylon winding forms machined• Need to wind RF coils and map field

NPDGammawindings

n-3Hewindings

3He Target / Ion Chamber

Scope: • Vacuum chamber, HV + sense wire frames.• Gas handling system

Status: • Chamber and Macor wire frames delivered• Beginning to string wire frames

Preamps

Scope $15k• 4 boxes with 32 channels each• Design and fabricate circuit, and mechanical enclosure• Connector to Target Chamber port and cabling to DAQ module

Status – on critical path• Have preliminary design (from NPDG preamps)• Must modify circuit for n-3He (10x larger signal)

Data Acquisition

Scope: • 128 channels of 16/24 bit ADC, > 60 KS/s $25k

data acquisition software; RAID storage array $15k

Progress: • selected candidate system D-tAcq CQ196CPCI-96-500• Each card 96 sim. channels + antialias filters + FPGA signal proc.

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

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

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• Expect to 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

Milestones• 2014-06-30 Integration of experiment on common stand• 2014-08-10 IRR – begin commissioning phase• 2014-09-15 Begin physics data taking

Runtime• 45 days commissioning (all equipment pre-assembled)• 15 days PC transverse asymmetry 1.7 x 10-6 ± 1 x 10-7

• 208 days PV longitudinal asymmetry 1.3 x 10-7 ± 1 x 10-8

Resources

All equipment funded except Preamp, DAQ, RAID ($60k)• 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

P-Division operations budget request ($75k)• Mainly for Engineering/Radiation support, removal of NPDG• See budget spreadsheet for details