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%

POLARIZINGHIGH-FLUXNEUTRONBEAMS

withPOLARIZED3HeSPINFILTERS

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)

POLARIZATIONvs TIMEforBooBoo,2005runonLANSCE Pebbles,2006NPDGamma run

“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]

BEAMEFFECTSSTUDIESonPF1BattheILL,2007 EarlBabcocketal

Alkalipolarizationvs neutronfluxAlkalirelaxationvs time

Alkalirelaxationvs neutronflux

BEAMEXPOSURETESTS

Orvieto (Rb/Khybrid) Lottie(pureRb)

Highfluxneutronbeamsinducealkali-metalspinrelaxation

Neutronabsorptionby3Heproducesenergetictritonandproton

Relaxationrateproportionaltosquarerootofneutronflux:

Minorat108 n/s(LANSCE)Substantialat109 n/s(NISTNG6,SNSFNPB)Dominatesat1010 n/s(ILL,newNISTNG-C)

Longtermeffects:reducedtransparencyofcell,perhapsduetoRbH ?

NEUTRONBEAMEFFECTSONIN-SITUSEOPCELLS

DOUBLECELLTESTRoadrunner

JLABpolarized3Hetargethttp://hallaweb.jlab.org/physics/experiments/he3/

REINCARNATIONofSAREK

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