Transcript Hadronic PV and latest results – Neutron capture reactions

Proposal Update: the n-3He
Parity Violation Experiment
Christopher Crawford
University of Kentucky
for the n-3He Collaboration
FnPB PRAC Meeting
ORNL, TN 2010-12-16
Outline

Theoretical advances
•
•

Experimental update
•
•
•
•
•

Viviani – full 4-body calc.
Gudkov – reaction theory
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
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)

4He J =0+ resonance

sensitive to EFT coupling
or 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
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 reaction theory
•
Gudkov, PRC (in press)
PV
A = -(1 – 4)£10-7
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+, 1Tested against n-3He scattering lengths
2. Evaluation of weak <J-|VPV|J+> matrix elements
•
•
In terms of DDH potential
EFT calculation in progress
Sensitivity matrix for few-body reactions
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

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
-
•

NPDGamma
windings
n-3He
windings
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
field lines
end 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

Chamber and flanges have
been delivered to U. Manitoba

Macor ceramic frame,
Cu wires, 200um diameter

Construction of frame / wires
will be completed in 2011.
Data Acquisition

Requirements similar to NPDGamma
•
•

High channel density: ~144 channels
•
•

Driven by the size of the chamber and proton range
Data rate ~3x higher than NPDGamma
VME-based system
•

16 bit resolution, 100 kHz sample rate
Simultaneous external triggering (precise timing)
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
gas
< 1 cm
HV grid wires
Si, anodes on each side
3He
baffles
-HV
-HV
-HV
-HV
-HV
-HV
MC Simulations

Two independent simulations:
1.
2.
•
Ionization at each wire plane
averaged over:
•
•
•
•
•
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

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
3. 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
6Li
Shutter
CsI crystal
B4C target
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
 NPDG electronics:
•
•
•
•
•
•
B-field power supply
RFSF electronics
Trigger electronics
SNS / chopper readout
Fluxgate magnetometers
Computer network
 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
Projected schedule
Offsite
ORNL

Jan 2011 – Jul 2012
•

•
NPDGamma data-taking
•
Stage of stand, solenoid,
RFSF, Ion Chamber
in nEDM building
•
•
(request: 1000 hrs)
Beam axis scans
3He Polarimetry
Jan 2013
•
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
Installation at FnPB
Field map at FnPB
Sept 2012
•
•

Jan 2011 – July 2011
Aug 2012
•
•


July 2012
•

(beam)
3He
(request: 5000 hrs)
data-taking

Aug 2011, May 2012
•
test RFSF, 3He chamber, and
DAQ at LANSCE FP12
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