Search for an EDM of the neutron at PSI

• Collaboration• Context• Our approach• The UCN source at PSI• Present research at ILL• Future EDM at PSI

K. Kirch, PSIfor the nEDM collaboration

G. Ban, Th. Lefort, O. Naviliat-Cuncic, G. Rogel1Laboratoire de Physique Corpusculaire, Caen, France

K. Bodek, St. Kistryn, M. Kuzniak2, J. ZejmaInstitute of Physics, Jagiellonian University, Cracow, Poland

N. Khomytov, B.M. SabirovJoint Institute of Nuclear Reasearch, Dubna, Russia

P. Knowles, M. Rebetez, A. WeisDepartement de Physique, Université de Fribourg, Fribourg, Switzerland

C. PlonkaInstitut Laue-Langevin, Grenoble, France

G. Quéméner, D. Rebreyend, M. TurLaboratoire de Physique Subatomique et de Cosmologie, Grenoble, France

M. Daum, R. Henneck, S. Heule3, M. Kasprzak4, K. Kirch, A. Knecht3, A. PichlmaierPaul Scherrer Institut, Villigen, Switzerland

The Neutron EDM Collaboration

also at: 1Institute Laue-Langevin, 2Paul Scherrer Institut, 3University of Zürich, 4SMI Vienna

ContextWhat is needed

for progress?– larger sensitivity,

much more UCN– better control

of systematics

hν+ = 2 (μnB + dnE)hν– = 2 (μnB – dnE)

hΔν = 4 dn E

Context

C. A. Baker et al., hep-ex/0602020P. G. Harris et al., PRL 82 (1999) 904

Sussex-RAL-ILL experiment

dn < 3 x 10-26 e cm

Context

hν+ = 2 (μnB + dnE)hν– = 2 (μnB – dnE)

hΔν = 4 dn E

50 pT

Context

·· · · · · ·

· ·· · ··· ··· ·· · ·· ·· ·

BoEUCN

199Hg

199Hg co-magnetometer

K.Green et al., NIM A 404 (1998) 381 P. G. Harris et al., PRL 82 (1999) 904

J.M.Pendlebury et al., PR A 70 (2004) 032102S.K.Lamoreaux and R.Golub, PR A 71 (2005) 032104P.G.Harris and J.M.Pendlebury, PR A 73 (2006) 014101C.A.Baker hep-ex/0602020

50 pT

Context

Other projects: cryogenic experimentswith UCN in superfluid 4He below 1K

Our approachImprove room-temperature, in-vacuum technique

At ILL:• Work with the RT experiment of Sussex-RAL-ILL

(measure, test, try, learn, repair, recuperate, ….)• Improve magnetic field measurement• Improve magnetic field stability and homogeneity• Improve overall stability and control (+ many other issues)At PSI:• Increase statistics• New systematic control tools• At some point: new system

Present planning

2006 2007 2008 2009 2010

UCN source at PSI

RAL-Sussex-ILL Spectrometer

New EDM spectrometer

Tests at ILL

Commission Normal operation

Upgrades ?Measurement at

PSI ?

ConstructionNew EDM

runs at PSIDecision to moveapparatus to PSI

Concept and design

nEDMSource

UCN source at PSIDeliver 600 MeV, 2mA at 1% duty cycle toUCN target station

2 mA,600 MeVproton beam1% duty cycle

3 m3 D2O

ρUCN~6000cm-3

2-3 m3 volumestorage trap

ρ ~ 2000 cm-3ρexp> 1000 cm-3

The PSI UCN source

UCN guide

30 liters solid D2

vacuum

• high power• low duty cycle• starts 2008 with 1 area• multi-user capabilitywith 2nd area, year xx?Papers by the PSI UCN groupconcerning related sourceand UCN physics athttp://ucn.web.psi.ch

Research at ILL

C. A. Baker et al., hep-ex/0602020P. G. Harris et al., PRL 82 (1999) 904

Sussex-RAL-ILL experiment

dn < 3 x 10-26 e cm

Understanding details…

Basic operation

UCN spectrum

0

100

200

300

400

500

600

700

800

1 25 49 73 97 121 145 169 193 217 241 265 289 313 337 361 385 409 433 457 481 505

channel

coun

ts

RAB95, amp x t = 16.5, t_prec = 50 s, visibility = 0.43, correct Ramsey with two pi/2 spinflips

2000

2500

3000

3500

4000

4500

5000

5500

6000

29,66 29,67 29,68 29,69 29,7 29,71 29,72

n-frequency [Hz]

cts/

cycl

e

spinupspindown

P.G. Harris et al., PRL 82 (1999) 904

Existing equipment mostlyunderstood and under control

: OK

UCN transport and counting: Understand Statistics

Simulations using Geant4 (S. Agostinelli et al., NIM A 506 (2003) 250)modified and extended for UCN:P. Fierlinger, PhD thesis, UniZh, 2005; F. Atchison et al., NIM A 552 (2005) 513.Further developed by M. Kuzniak and others in our collaboration.

Comparison of MC and experiment

MC of the experiment at PSI

MC of the experiment at PSI

Sussex-RAL-ILL apparatus @ PSI• gain factor 3-4 in sensitivity with the present

setup• gain factor 5-6 in sensitivity with new wall

material• need improved magnetic field stability,

homogeneity and control– improved co-magnetometry– external magnetometry, outside but close to UCN

Co-magnetometry I• Improve sensitivity of HgM

200 fT → 40 fT or better– initial polarization– prepolarizer volume– lamp vs. laser ?

• Activities just starting

Self-oscillating laser-pumped Cs magnetometers

1 magnetometer (OPM) needs 25 μW

1 laser delivers >10 mW1 laser = many sensors

• non-magnetic sensor head• Larmor frequency: 3.5 kHz @ 1 μT

S.Groeger, PhD thesis, UniFr, 2005S.Groeger et al.,J. Res. NIST 110, 179 (2005),Appl.Phys. B80, 645 (2005),EPJ D 38, 239 (2006),EPJ AP 33, 221 (2006,)http://www.unifr.ch/physics/frap/

External magnetometry with

http://www.unifr.ch/physics/frap/

Active field stabilization

correction coil

gradient fluctuations

Cramér-Rao limit: ~ τ -3/2OPM 1

OPM 2

Simple field stabilization coils give 103 improvement at 100 s.Gradient correction of the same order can be expected.

field stability for ~10-27 e cm

intrinsic sensitivity

Cs magnetometers in EDM

Operate Cs and Hgsimultaneously

50 pT

50 pT

PRL82(1999)904

B~1μT

~3.5 kHz

~8 Hz1 h~1 pT

Operate Cs and Hgsimultaneously

50 pT

50 pT

Active B-field stabilizationwith Cs-magnetometer works.HV-tests: P.Knowles et al., June 06Next: stabilize also gradients.

PRL82(1999)904

1 h~1 pT

A new dimension in diagnostics ...

Cs199Hg

280 GB of data under analysis at FRAPDAQ related: S.Groeger et al., arXiv physics/0506068

A new dimension in diagnostics ...

Movement of the UCN shutterseen at different locations:Effect of a magnetic impurity(see also hep-ex/0602020)

External Cs magnetometry• Many (vector) CsM desirable for monitoring of

the magnetic field• Stabilize magnetic field and gradients• It appears feasible to stabilize the field to a level

at least as good as was achieved by offline correction with the HgM before

• But: probably not sensitive enough to leakagecurrents and magnetic wall impurities

Improvements for a new EDM• Double chamber setup, larger volumes• Velocity sensitive UCN detection

(false neutron EDM: daf,n ~ Bz-2 dBz/dz )

• Second co-magnetometer(go for no atomic false EDM: daf,atom ~ γ2 R2 dBz/dz )

• Stability, control and logging of theenvironmental data

Co-magnetometry II• Potential co-magnetometer candidates:

199Hg (7.7 Hz/μT), 129Xe (-11.8 Hz/μT), 3He (-32.4 Hz/μT)• Geometrical phase induced false effect:

(Pendlebury et al., PRA70(2004)032102)daf,atom ~ γ2 R2 dBz/dz daf,n ~ Bz-2 dBz/dz

• Example: Bz=1μT, dBz/dz=1nT/m

daf,n ~ 10-27e cm

daf,Hg ~ 13 x daf,ndaf,Xe ~ 2 x daf,Hgdaf,He ~ 18 x daf,Hg

Two null results for atomicco-magnetometers couldprove the stability of theB-field magnitude and theabsence of gradients

D. Wark

We appreciatethe great technicalsupport of manyindividuals and workshopsthroughout thewhole collaboration

and thank themembers of theRAL-Sussex-ILLcollaboration forallowing us to usetheir apparatus.

D. Wark

Velocity sensitive UCN detection

Problem: UCN velocitydependent EDM systematics G4-UCN** simulation

of UCN with energies[0, 250] neV at 100 cmfalling into a 6-foldsegmented detector

e.g. B = 1 μT, E = 10 kV/cm, dB/dz =1 nT/m

dn(false)* = 3 x 10-27 e cm*J.M.Pendlebury et al., Phys. Rev. A 70 (2004) 032102S.K.Lamoreaux and R.Golub, Phys.Rev. A 71 (2005) 032104P.G.Harris and J.M.Pendlebury, Phys. Rev. A 73 (2006) 014101

** F.Atchison et al., NIM A552(2005)513Idea: Measure EDM as function of UCN velocity with efficient simultaneous detectione.g. δdn √2 δdn in 2 energy bins withaccording ability to test an EDM signal

• PhD project at PSI• study of detector options• realization of prototype• comprehensive study of UCN velocity related systematics

Comparison of MC and experiment

Example calculation: #(Cs)Use a spherical harmonics expansion formalism in order to calculate the number of sensors, their optimum locations, optimum (correction) coil configurations, etc.Caveat: Assume no magnetization and no currents inside the volume surroundedby the magnetometers.

Clearly prefervector typemagnetometers !

Calculations: E-fieldsOpera 3D models are used to predict theelectric fields in the experiment and calculatethe influence of external magnetometers.

E-fields from 2D and 3D models serve as input for UCN simulationsin the investigation of systematic effects, due to, e.g. motional magnetic fields

Adapted Geant4* for UCNUCN specific features:

– Boundary and bulk material interaction– Particle tracking with gravity– Particle tracking through arbitrary (in general:

inhomogenous, dynamic) magnetic fields– Spin tracking through arbitrary magnetic fields

P. Fierlinger, PhD thesis, UniZh, 2005T. Brys et al., NIM A 550 (2005) 637F. Atchison et al., PL B 625 (2005) 19F. Atchison et al., NIM A 551 (2005) 429

* S. Agostinelli et al., NIM A 506 (2003) 250

Search for an EDM of the neutron at PSIThe Neutron EDM CollaborationContext ContextContextContextContextOur approachPresent planningThe PSI �UCN sourceResearch at ILLUnderstanding details…Basic operationUCN transport and counting: Understand Statistics Comparison of MC and experimentMC of the experiment at PSIMC of the experiment at PSISussex-RAL-ILL apparatus @ PSICo-magnetometry ICs magnetometers in EDMOperate Cs and Hg�simultaneouslyOperate Cs and Hg�simultaneouslyA new dimension in diagnostics ...A new dimension in diagnostics ...External Cs magnetometryImprovements for a new EDMCo-magnetometry IIComparison of MC and experimentExample calculation: #(Cs)Calculations: E-fields

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