POLARIZED3HeinFUNDAMENTALPHYSICSwithCOLDNEUTRONS
TomGentileNationalInstituteofStandardsandTechnology
(NIST)
NEUTRONSPINFILTERSforFUNDAMENTALPHYSICS
EXPERIMENTS
DecaycorrelationcoefficientsA (spin-electron)andB (spin-neutrino)asymmetrycoefficients
(measureneutronpolarizationproducedby”crossed”supermirrors)D(time-reversal)coefficient
Parityviolatinggammaasymmetry(NPDGamma)(discoveryofeffectsonneutronbeamsonin-situSEOP)
Neutronspinrotation
Fewbodyphysics:spin-dependenceofn-3Hescatteringlength
PRECISIONNEUTRONPOLARIMETRYfora
MEASUREMENTofthen-3HeINCOHERENTSCATTERINGLENGTHof3He
T.R.Gentile1,M.Arif1,W.C.Chen1,2,D.S.Hussey1,D.A.Pushin1,L.Yang1,M.G.Huber3,F.E.Wietfeldt3 andT.C.Black4
1. National Institute of Standards and Technology2. Indiana University3. Tulane University4. University of North Carolina at Wilmington
AcknowledgementstoNSFandDoE
ExperimentalOverview
Spin
Wemeasurethen-3Hespin-dependentscatteringlengthusingpolarized3Hegastrappedinaglasscell.Thephaseshiftf betweenthetwoflipperstates(offoron)isrelatedtothespin-dependentscatteringlength(bi)by
0.80.60.40.20.0
-0.2-0.4-0.6-0.8
∆φ0,
[rad]
0.80.40.0-0.4-0.8ξ
25
20
15
10
5
0-0.1 0.0 0.1
R
(b)
PHASESHIFTMEASUREMENT
M.G.Huberetal,Phys.Rev.C90,064004(2014).
(proportionalto3Hepolarization)
€
Pn = tanh[t PHe ]
PRECISION NEUTRON POLARIMETRY with POLARIZED 3He
€
Tn = T0 cosh[t PHe ]
€
Pn = 1− T0Tn
#
$ %
&
' (
2 Pn=neutronpolarizationTn =transmissionofpolarizedcellT0=TEexp(-t)=transmissionofunpolarized cell
TE=transmissionofemptycell
NEUTRONPOLARIZATIONdeterminedfromtransmission
crosssectionproportionaltol - timeofflightanalysisideal
t=opacity =crosssection*3Hedensity*celllength
PHYSICSASYMMETRYproportionaltoPn
€
PA = tanh[t PHe ] = 1− T0
Tn
#
$ %
&
' (
2
PRECISION NEUTRON POLARIMETRY with POLARIZED 3He
€
Tn = T0 cosh[t PHe ]Unpolarizedneutrons:Tn=transmissionofpolarizedcellT0=transmissionofunpolarizedcell
ANALYZINGPOWERdeterminedfromrelativetransmission
t=opacity =crosssection*3Hedensity*celllength
€
PA =T+ −T-T+ +T-
Perfectlypolarizedneutrons:T+=neutronsand3HepolarizationparallelT- =neutronsand3HepolarizationantiparallelPA=analyzingpower
Skylight(polarimetrycell)
Pistachio
(interferometercell)
Threepolarimetrycellsused:Haystack,Skylight,Whitefacepressures=2.9- 3.5bar,yieldingt=3.0- 3.6andPA =0.88- 0.99forPHe =0.45- 0.7
Relaxationtimes~150hintrinsic,35hatinterferometerdueto2x10-3 cm-1 fieldgradient
92.8
92.85
92.9
92.95
93
99.4
99.45
99.5
99.55
99.6
Neutron polarization Pn and spin flip efficiency s from asymmetry and NT antiparallel methods
Pn s
P n s
asymmetry
NT antiparallel
combined
asymmetry
NT antiparallel
combined
O.Zimmeretal,EPJDirect1-28(2002).“Aprecisemeasurementofthespin-dependentneutronscatteringlengthof3He”
ILLMEOPcompressionapparatususedtopolarizeasilicon-windowed10cmlongcylindricalcelltheninstalledinaneutronspin-echoapparatus
G.L.Greene,A.K.Thompson,M.S.Dewey,Nucl.Instrum.Meth.A356,177(1995).“Amethodfortheaccuratedeterminationofthepolarizationofaneutronbeamusingapolarized3Hespinfilter”
O.Zimmer,Phys.Lett.B461,307- 314(1999).“Amethodforpreciseneutronbeampolarisation analysisusinganopaquespinfilter”
O.Zimmeretal,Phys.Lett.B455,62- 68(1999).“High-precisionneutronpolarizationanalysisusingopaquespinfilters”
O.Zimmer etal.,Nucl.Instrum.Meth.A440,764- 771(2000).“Spinfiltersandsupermirrors:acomparisonstudyoftwomethodsofhigh-precisionneutronpolarisation analysis”
D.R.Richetal,Nucl.Instrum.Meth.A481,431- 453(2002).“Ameasurementoftheabsoluteneutronbeampolarizationproducedbyanopticallypumped3Heneutronspinfilter” 0.3%intheneutronenergyrangefrom40meV to10eV
M.Kreuz etal,Nucl.Instrum.Meth.A547,583- 591(2005).“Thecrossedgeometryoftwosupermirrorpolarisers - anewmethodforneutronbeampolarisation andpolarisation analysis”
F.E.Wietfeldt andT.R.Gentile,J.Res.Natl.Inst.Stand.Technol.110,305- 308(2005).”Anew method forprecision cold neutron polarimetry using a3Hespin filter”
S.I.Penttila andJ.D.Bowman,J.Res.Natl.Inst.Stand.Technol.110,1- 5(2005).”Precisionneutron polarimetry forneutron betadecay”
T.E.Chupp etal,Nucl.Instrum.Meth.A574,500- 509(2007)."Alarge areapolarized 3Heneutron spin filter”0.1%with TOFanalysis forthe LANSCEFP12cold neutron beam
S.Masalovich,Nucl.Instrum.Meth.A581,791- 798(2007).”Methodtomeasure neutron beampolarization with 2×1neutron spin filter”
T.Ino etal,Physica B406,2424- 2428(2011).”MeasurementoftheneutronbeampolarizationofBL05/NOPbeamlineatJ-PARC”0.03%intheneutronwavelengthrangefrom0.1nm(81meV)to0.7nm(1.7meV)
NEUTRON POLARIMETRY WITH SPIN FILTERS
0.996
0.997
0.998
0.999
1
10-9
10-8
10-7
10-6
10-5
0.0001
0.001
0.01
0.1
1
0.2 0.4 0.6 0.8 1 1.2
OPAQUE SPIN FILTERS
(50% 3He polarization assumed)
A (15 bar-cm)
A (25 bar-cm)
A (40 bar-cm)T (15 bar-cm)T (25 bar-cm)T (40 bar-cm)
anal
yzin
g po
wer
transmission of desired spin state
neutron wavelength [nm]
M.Schumannetal,Phys.Rev.Lett.99,191803(2007)“MeasurementoftheneutrinoasymmetryparameterB inneutrondecay”
M.Schumannetal,Phys.Rev.Lett.100,151801(2008).“Measurementoftheprotonasymmetryparameterinneutronbetadecay”
D.Mund etal,Phys.Rev.Lett.110,172502(2013)."Determinationoftheweakaxialvectorcouplingl =gA/gV fromameasurementoftheb-asymmetryparameterA inneutronbetadecay"
A, B, and C at the Institut Laue-Langevin
Neutronpolarizationmeasuredtobe99.7+/- 0.1%
n + p
g
g
PNCasymmetry:
€
Aγ ( ˆ σ n • k γ )
€
Aγ = 0.11 fπ1 ~ 5 x 10−8
PARITYVIOLATIONinNUCLEON-NUCLEONINTERACTIONS
(mesonexchangemodel)
np
Parityoperator:
€
r →− r
3HepolarizerforNPDgexperimentatLANSCE
Continuousoperationinahighfluxbeamrevealeddecreasein3Hepolarizationshorttermeffect(alkalipolarization)andlongtermeffect(opacitytolaserlight)EffectsstudiedonPF1bandtomographybeamlineattheILL(Babcocketal)
oneyearofnearlycontinuoususein2005forstudyofsolidtargets
M.T. Gericke etal,Phys.Rev.C74,065503(2006)
NPDg resultM.Gericke etal,Phys.Rev.C83,015505(2011)
Ag =-1.2+/- 2.1(stat)+/- 0.2(sys)x10-7
Polarizer:T.E.Chupp etal,Nucl.Instrum.Meth.A574,500-509(2007)Beameffects: M.Sharmaetal,Phys.Rev.Lett.101,083002(2008)
E.Babcocketal,Phys.Rev.A80,033414(2009)
“BooBoo”after1yearinLANSCEbeam ~108 n/(cm2-s)
0
0.2
0.4
0.6
0.8
1
120 130 140 150 160 170 180
BooBoo pumped with two 50 W QPC lasers
narrowed or unnarrowed
narrowed laser
broad laserP R
b
temperature [deg C]
Highfluxneutronbeamsinducealkali-metalspinrelaxation
Neutronabsorptionby3Heproducesenergetictritonandproton
Relaxationrateproportionaltosquarerootofneutronflux:
Minorat108 n/s(LANSCE)Substantialat109 n/s(NISTNG6,SNSFNPB)Dominatesat1010 n/s(ILL,newNISTNG-C)
Longtermeffects:reducedtransparencyofcell,perhapsduetoRbH ?
NEUTRONBEAMEFFECTSONIN-SITUSEOPCELLS
0
5
10
15
20
25
30
0
5
10
15
20
25
180 190 200 210 220
TESTS with SAREK - Oct 2016
D = [K]/[Rb] = 7 MAX POL (neutron-based) - 58%
expect 66% for T1=70 h and X=1.25
pumping timc constant [h]
NMR signal [mV]pu
mpi
ng ti
mc
cons
tant
[h]
NM
R signal [m
V]
temp [C}
SUMMARY
3HeSPINFILTERSPROVIDEAMEANSFORHIGHLYACCURATEDETERMINATIONofNEUTRONPOLARIZATION(andaccurate3Hepolarizationmeasurements)
FUTUREEXPERIMENTSTHATWOULDUSEIN-SITUSEOP 3HeSPINFILTERSinHIGHFLUXNEUTRONBEAMS WOULDNEEDTOADDRESSBEAM-INDUCEDRELAXATION,PROBABLYWITHLARGEDOUBLECELLS
POLARIZED3HeHASBEENEMPLOYEDTODETERMINETHESPIN-DEPENDENCEOFTHEn-3HeSCATTERINGLENGTHBYBOTHNEUTRONSPIN-ECHOANDINTERFEROMETRYMETHODS
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