Transcript Hadronic PV and latest results – Neutron capture reactions

n-3He Experiment:
overview and updates
Christopher Crawford
University of Kentucky
n-3He Collaboration Meeting
ORNL, TN 2010-10-16
Outline
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Introduction
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Theoretical advances
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Viviani – full 4-body calc.
Gudkov – reaction theory
Experimental update
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n+3He reaction
Experimental setup
MC simulations
Statistical sensitivity
Systematic errors
Transverse RF spin rotator
3He target / ion chamber
Management
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FnPB approval status
Schedule
Work packages
Madison
Spencer
n-3He PV Asymmetry
n
p
n p
+
n
n pp
p
+
n
n p
PV observables:
~ kn very small for
low-energy neutrons
S(I):
20.578
- essentially the same asym.
- must discriminate between
back-to-back proton-triton
19.815
Tilley, Weller, Hale, Nucl. Phys. A541, 1 (1992)
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4He J =0+ resonance
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sensitive to EFT coupling
or DDH couplings
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~10% I=1 contribution
(Gerry Hale, qualitative)
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A ~ -1–3x10-7 (M. Viviani, PISA)
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A ~ -1–4x10-7 (Gudkov)
mixing between 0+, 0- resonance
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Naïve scaling of p-p scattering
at 22.5 MeV: A ~ 5x10-8
Theoretical calculations – progress

Vladimir Gudkov (USC)
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PC
Ay(90±) = -1.7±0.3£10-6
R matrix calculation of PC asymmetry,
nuclear structure, and resonance properties
Anna Hayes (LANL)
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PV reaction theory (to be submitted)
Gerry Hale (LANL)
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A = -(1 – 4)£10-7
PV
No-core shell model calculation with AV18 potential, etc.
Michele Viviani et al. (INFN Pisa)
PV
A = -(.944 – 2.48)£10-7
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full 4-body calculation of scattering wave function
calculation of asymmetry within DDH framework
progress on calculation of EFT low energy coefficients
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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 
-0.11
0.92
-0.18
-3.12
-0.97
-0.50
-0.14
-0. 23
-0.32
0.08
0.14
0.10
0.027
0.11
0.08
0.05
hr 2
0.05
0.0012
-0.25
h 0
-0.16
-0.13
-0. 23
f
hr 0
hr 1
h 1
-0.001
-0.003 -0.002
0.05
pp Az
p Az
-0.34
0.03
-0.22
-0.07
0.06
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:
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AV18
AV18/UIX
N3LO
N3LO/N2LO
 Pion-full EFT calculation?
Experimental setup
FnPB cold
neutron guide
supermirror
bender polarizer
(transverse)
10 Gauss
solenoid
3He
Beam
Monitor
transition field
(not shown)
3He
RF spin
rotator
FNPB
target /
ion chamber
n-3He
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longitudinal holding field – suppressed PC asymmetry
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RF spin flipper – negligible spin-dependent neutron velocity
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3He
ion chamber – both target and detector
MC Simulations
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Two independent simulations:
1.
2.
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Ionization at each wire plane
averaged over:
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a code based on GEANT4
a stand-alone code
including wire correlations
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
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Majority of neutron captures occur
at the very front of chamber
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Self-normalization of beam fluctuations
Reduction in sensitivity to A
Statistical Sensitivity
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N = 2.2£1010 n/s flux (chopped)
x 107 s (4 full months @ 1.4 MW)
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P = 96.2%
neutron polarization
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d = 6
detector efficiency
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A/A ~ 5% assuming A=3x10-7
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A/A ~ 26% worse case A=5x10-8
Systematics
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Beam fluctuations, polarization, RFSF efficiency:
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knr ~ 10-5 small for cold neutrons
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PC asymmetries minimized with longitudinal polarization
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Alignment of field, beam, and chamber: 10 mrad achievable
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Unlike NPDG, NDTG: insensitive to gammas (only Compton electrons)
Systematic Error constraints
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Mott-Schwinger and parity
conserving nuclear asymmetry
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Measure longitudinal instead of
transverse asymmetry
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1) measure the average kn at
two different places along the
beam using the wire chamber
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2) align the B field parallel to kn
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3) align the wire planes to be
perpendicular to the holding
field (same as kn) to 2 degrees
by dead reckoning
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4) rotate the chamber by 180
degrees about the holding field
and measure again to cancel
small residuals
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Use a magnetic compass
which can measure the field
direction to 0.1 deg
Transverse RF spin rotator – n3He
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extension of NPDGamma design
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P-N Seo et al., Phys. Rev. S.T.
Accel. Beam, vol 11, 084701 (2008)
TEM RF waveguide
new resonator for n-3He experiment
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transverse horizontal RF B-field
longitudinal / transverse flipping
no fringe field - 100% efficiency
compact geometry - efficient
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NPDGamma
windings
smaller diameter for solenoid
matched to driver electronics
for NPDGamma spin flipper
prototype design
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parasitic with similar design for
nEDM guide field near cryostat
fabrication and testing at UKy – 2009
n-3He
windings
RFSF winding: designed from the inside out
Magnetostatic calculation with COMSOL
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Standard iterative method:
Create coils and simulate field.
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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 lines
blue - end-cap windings
Prototype RFSF
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Developed for static nEDM guide field
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1% uniformity DC field
3He Target / Ion Chamber – Considerations
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Must measure proton asymmetry in current
mode directly in target
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Can distinguish back-to-back
proton and triton by their range
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Ep:Et = mt:mp = 3:1
Must let protons range out: rp~5 cm
Neutron mean free path should be < rp/2
Current-mode
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HV: 1 – 3 kV
200 Al wires
3He
Target / Ion Chamber – Design
M. Gericke,
U. Manitoba
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Custom aluminum CF flanges
with SS knife-edges
Macor ceramic frame supporting
pure copper wires, 200um diameter
Being designed and constructed at the
University of Manitoba
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Similar to the design that was used for
the NPDGamma beam monitors
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Chamber and parts have been ordered
Data Acquisition
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Requirements similar to NPDGamma
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High channel density: 20 x 19 channels or less
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16 bit resolution, slow 100 kHz
Simultaneous external triggering (precise timing)
Driven by the size of the chamber and proton range
Simultaneous measurement of AL, AT
Data rate ~10x higher than NPDGamma
VME-based system
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Groups of 4 IP modules mounted on CPU processors
for data reduction with direct access to RAID disk
Projected schedule – old
Offsite
ORNL
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Jan 2011 – Jul 2012
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Jan 2011 – May 2011
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NPDGamma data-taking
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Aug 2011 – Dec 2011
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Aug 2012 – Dec 2012
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Construction of solenoid
Test of field uniformity,
alignment procedures
Installation at FnPB
Commissioning
Jan 2013 – Dec 2013
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3He
data-taking
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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
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test RFSF, 3He chamber, and
DAQ at LANSCE FP12
window of opportunity for
the n-3He experiment between
NPDGamma and Nab
Work Packages

Theory
- Michele Viviani
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MC Simulations
- Michael Gericke / ?
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Polarimetry
- Stefan Baessler / Matthew Musgrave
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Beam Monitor
- Rob Mahurin
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Alignment
- David Bowman / Geoff Greene
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Field Calculation
- Septimiu Balascuta
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Solenoid / fieldmap
- Libertad Baron Palos
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Transition, trim coil
- Pil-Neyo Seo
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RFSF
- Chris Crawford
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Target / detector
- Michael Gericke
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Preamps
- Michael Gericke / ?
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DAQ
- Nadia Fomin / Chris Crawford
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Analysis
- Nadia Fomin / Chris Crawford
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System integration/CAD - Seppo?
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Rad. Shielding / Tritium - John Calarco
Organization
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Collaboration meetings after NPDG meetings
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Regular phone conferences: ~monthly
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Collaboration email list: [email protected]
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PRAC in December: submit request for beam time
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Installation target date: July 2012