Transcript Hadronic PV and latest results – Neutron capture reactions

Systematics of the SNS n3He Experiment
Christopher Crawford
University of Kentucky
for the n-3He Collaboration
APS April Meeting
Denver, CO, 2013-04-16
Overview – Hadronic Weak Interaction (HWI)
Viviani et al, PRC 82 (2010), 044001
Nuclear
<structure>
Nuclear PV
Hadronic
<structure>
Few-body PV
EW
Wasem, PRC 85 (2012), 022501
2/10
Experimental setup at the FnPB
FnPB cold
neutron guide
supermirror
bender polarizer
(transverse)
10 Gauss
solenoid
3He
Beam
Monitor
RF spin
rotator
FNPB
3He
target /
ion chamber
n-3He

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.
2.
a code based on GEANT4
a stand-alone code
including wire correlations
= 1.6 x 10-8
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
4/10
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)
5/10
Transverse RF spin rotator

Resonant RF spin rotator
•

Properties suitable for n-3He expt.
•
•
•
•
•
•
•

P-N Seo et al., PRSTAB 11, 084701 (2008)
Transverse horizontal RF B-field
Longitudinal or transverse flipping
No fringe field - 100% efficiency
Real, not eddy currents along outside
minimizes 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
6/10
Target Ion Chamber

Chamber all aluminum except for the knife edges.
•
•
•

Macor wire frames
•

4 feedthrough ports (153 readout channels)
2 HV ports + 2 gas inlets/outlets
12 inch aluminum windows (0.9 mm thick).
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
1. Scan beam profile upstream
and transfer centroid to crosshairs
2. Scan beam profile downstream
5. Field map in RFSR/Target region
6. Align the position / angle of target with
theodolite / autocollimator
3. Align theodolite to crosshairs
7. Tune RSFR / measure polarization
4. Align B-field to theodolite
8. Measure physics asymmetry
9/10
Summary
n-3He collaboration

Last measurement for the a
characterization of the
Hadronic Weak Interaction

15% projected uncertainty
will be the most accurate
HWI experiment in a
few-body system

Scheduled FnPB beam time
June 2014 – Dec 2015
10/10
Theoretical calculations – progress

Gerry Hale (LANL)
•

PV
A = -(.248 – .944)£10-7
full 4-body calculation of scattering wave function
-
•
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)
•
PC
Kohn variational method with hyperspherical functions
No parity mixing in this step: Jπ = 0+, 0-, 1+, 1Tested 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)
Viviani, PAVI (2011), preliminary
PV VNNEFT,
a0 – a5
EFT NN potential revisited to NNLO

Viviani et al., preliminary (PAVI 11)
•
•
•
•
•
•
(a)
Q0
(CT) Q1
(b,c) Q2
(e,h) Q2
(d),
Q2
(f,g,g’) Q2
h1π
gπ(r)
C1,2,3,4,5
Z(r)
zero
renorm./absorb in h1π
h1π+C3 (triangle)
L(r)
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
Saturday, January 05, 2013
10:37 PM
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:

Maximum voltage:

Resonant frequency:

Stored energy:

Dissipated power:

Quality factor: Q=151



Inductance: 4.5 mH

R&D: test 3 winding patterns with same field in high-frequency limit
INNER
INNER/OUTER
OUTER
Capacitance: 7.5 nF
Resistance: 5.1 Ω
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
data acquisition software; RAID storage array
$51k
$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
2014-07-18
2014-10-27
2015-02-??
Begin assembly and testing in EDM building
Begin installation in FnPB cave
IRR – begin commissioning phase
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