ORNL, 11.10.2012 Philipp Schmidt- Wellenburg Searching for a nEDM at PSI P. Schmidt-Wellenburg on...

ORNL, 11.10.2012

Philipp Schmidt-Wellenburg

Searching for a nEDM at PSI

P. Schmidt-Wellenburgon behalf of the

PSI-nEDM collaboration

Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 2/28

The collaboration

• 6 countries• 14 institutions• 45 members


UCN source at PSI

UCN Source

Proton Accelerator590 MeV Cyclotron2.2 mA beam current nEDM

2 experimental areas / 3 beamlines

See talk by B. Lauss


Outline

• The apparatus

• Ongoing measurements and results• UCN - performance• Magnetometers and field control• High voltage and leakage currents

• Ideas for the next generation experiment


Apparatus overview


The apparatus

• 2009 Transfer from ILL (France) toPSI (Switzerland)

• Setup in thermally stabilized wooden house

• Two independent air-conditionings

• Six coils for surrounding field compensation (SFC)


Outline

• The apparatus




UCN operation

Filling

Monitor

Em

pty

A. Serebrov et al., NIMA 545(2005)490


UCN

3H

6Li

6Li depleted

6Li enriched

110

µm

6

0 µm

UCN detector

Time (ns)

Sign

al (

mV)

G. Ban et al., NIMA 611 (2009) 280

• 6Li doped glass scintillator stack• 9 independent channels

(PMTs +DAQ)• High count rate capable > 10 M


UCN Detector• Monitor mode ~70000 UCN• Emptying ~30000 UCN

• High UCN losses• High depolarization rate

G. Ban et al., NIMA 611 (2009) 280


UCN emptying curve• During emptying: high loss rate of

stored spin component → wrong polarisation

τflip = 236 s

τloss =16.5 s

τ↓ = 163 s

τ↑ = 16.9 s

N = 29185α0 = 0.999

Best fit to

data


UCN storage time

21

210)( tt

eNeNytN

s 55180

s 2152

2

1

NTE

2


UCN Spin performance

• Rough adjustment of trim coils

• UCN detection spin sequence not yet optimized


UCN Ramsey cycles

Ramsey curve taken with 250 s precession time


100 200 300 400 500Ts

2 10 24

5 10 24

1 10 23

2 10 23

5 10 23

1 10 22

ecm

Sensitivity

Minimum:σ(219s)=5.94×10-24 e·cm → σ(1d)=4×10-25 e·cm

E=110/12 kV/cmN10=9838N20=8042T1=56.6 sT2=182.5 sα0=0.79Tα=556.6 s

Assuming 30 x more UCN


Outline

• The apparatus




The measurement technique

Measure the difference of precession frequencies in parallel/anti-parallel fields:

BBμEEdΔ nn 22

for dn<10-26 ω < 60 nHz

RAL-Sussex-ILL:

dn < 2.9 x 10–26 e cm

C.A.Baker et al., PRL 97 (2006) 131801


Magnetic shield• Four layer Mu-Metal

• Shielding factors:x: 12000, y: 3000, z:8000


• Surrounding field (~ 80μT)• Compensation and stabilization• Three coil pairs:

• 6m x 8m, d= 4m

• 9/18 windings

• Six current supplies(10/20 A)

• Ten 3-axis Fluxgates (FG)

Surrounding field compensation


FG 3FG 9

Y

Z

XTherm

o house

(first

floor)

door

nEDMCoordinate

system

Al fr

ame

Magnetic shield

FG 8

FG 7

FG 0 FG 2

FG 6

Sensor positionsMonitoring positionsclose to shield (~ 0.3…0.8 m)

FG 1

FG 5


ResultsFeedback with inverted & regularized Matrix•Twelve sensors close to shield taken into account

(for x-direction shown below:sensors 0x, 3x, 6x, and 8x are used)


Systematic effects

• Most important source of systematic effects

→Field mapping

→Online Cs-OPM measurement

→Dedicated B-drift runs (ramping E-field)

→Magnetic scanning at PTB, Berlin

× 10-27


Hg co-magnetometer

See talk by D. Rebreyend

Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012

Principle of Cs magnetometer

0

2

4

6

8

10

6970 6980 6990 7000 7010 7020 7030

-90

-45

0

45

90

Pha

se(°

)

Frequency (Hz)

-4

-2

0

2

4

Qua

drat

ure

(Y)

(arb

.uni

ts)

Inph

ase

(X)

(arb

.uni

ts)

Phase signalcloseto resonance

n nrf L=


Cesium magnetometers

Monitoring of vertical magnetic gradients

• Two cesium magnetometer arrays

• Stabilized laser• PID phase locked DAQ

1 2 3 4

5 … 11 12

±140kV


Homogenizer and fiber bundle

Fiber bundle

Beam splitter mounted on the enclosure support

31 vacuum feedthroughsfor optical fibers


Adjusting field gradients

• Measure the response of all n=17 magnetometers to changes of each m=33 individual coil current

10pT

10nT

• Known response allows to calculate ideal currents for given field setting(iterative process)


Gradients

• STD from six gradiometer pairs


Outline

• The apparatus• Ongoing measurements and results

• UCN - performance• Magnetometers and field control• High voltage and leakage currents



High voltage

• Cesium work with HV• HV did not work with Cs

Tests• HV works up to 200kV• Flashovers along fiber

bundles• Reliable HV runs at ±150kV

Leakage current @ 195 kV

nA

3

2

1

15:06 15:14


Testing high voltage

Configuration w bundle -110 kV vacuum 145 kV He/Ne

Configuration wo bundle 198 kV He/Ne 200 kV He/Ne


Leakage current

1. Changing the polarity of the high voltage will change the direction of the leakage current, and hence the magnetic field produced by these currents

2. Most contribution of the leakage currents cancel out, not so jφ.

jr

jr

jφ jφ

jφ

jz

Leakage currents are caused by the high voltageand appear along the surface of the insulator ring.

A leakage current of 1 nA produces a false edm of 2 × 10 -28 e cm


Leakage current measurement

0 2 4 6 8 103.5555

3.5560

3.5565

3.5570

3.5575

3.5580

3.5585

3.5590

3.5595

3.5600

Cur

rent

(nA

)Time (h)

0.75pA4 pA

FEMTO

1. Monitoring of leakage currents on ground electrode

2. Combination of protection circuit and highly sensitive current/voltage amplifier -80 -60 -40 -20 0 20 40 60 80

-0.9

-0.6

-0.3

0.0

0.3

0.6

0.9

I Lea

k (n

A)

UHV (kV)

ILeak ≤ 0.5 nAσ ≤ 0.1 × 10-27e cm


Outline

• The apparatus

• Ongoing measurements and results• UCN - performance• Magnetometers• High voltage and leakage currents



E

E

n2EDM: General concept

• Simultaneous measurement in 2 precession chambers

• Laser based Hg co-magnetometer

• 3He magnetometers• Multiple Cs

magnetometers for 3He readout and gradients

• UCN chamber position at PSI UCN beam height

3He see talk by A. Kraft


Thermohouse2

• 10×6×8 m3

• EMC shield made of copper• Thermally stabilized


Conclusion & Outlook• Apparatus is ready for data taking

• Presently remeasuring UCN parameters

• High quality adjustment of B-field gradients

• Excellent performance of high voltage

• nEDM data taking from Nov 2012

• 400 nights of data in 2013/2014→ σ < 5×10-27 e·cm

• In parallel design of next generation experiment → σ < 5×10-28 e·cm


also at: 1Paul Scherrer Institut, 2PNPI Gatchina, 3Eidgenössische Technische Hochschule, 4GUM Mainz

The Neutron EDM Collaboration

M. Burghoff, A. Schnabel, J. Vogt

G. Ban, V. Helaine1, Th. Lefort, Y. Lemiere,O. Naviliat-Cuncic, G. Quéméner

K. Bodek, G. Wyszynski3, J. Zejma

A. Kozela

N. Khomutov

Z. Grujic, M. Kasprzak, P. Knowles, H.C. Koch4, A. Weis

G. Pignol, D. Rebreyend S. Afach, G. Lembke

N. Severijns, P. Pataguppi

S. Roccia

C. Plonka-Spehr, J. Zenner1

W. Heil, A. Kraft

G. Bison, Z. Chowdhuri, M. Daum, M. Fertl3 , B. Franke3, B. Lauss, A. Mtchedlishvili, D. Ries3, PSW, G. Zsigmond

K. Kirch1, J. Krempel, F. Piegsa

Physikalisch Technische Bundesanstalt, Berlin

Laboratoire de Physique Corpusculaire, Caen

Institute of Physics, Jagiellonian University, Cracow

Henryk Niedwodniczanski Inst. Of Nucl. Physics, Cracow

Joint Institute of Nuclear Reasearch, Dubna

Département de physique, Université de Fribourg, Fribourg

Laboratoire de Physique Subatomique et de Cosmologie, Grenoble

Biomagnetisches Zentrum, Jena

Katholieke Universiteit, Leuven

Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, Orsay

Inst. für Kernchemie, Johannes-Gutenberg-Universität, Mainz

Inst. für Physik, Johannes-Gutenberg-Universität, Mainz

Paul Scherrer Institut, Villigen

Eidgenössische Technische Hochschule, Zürich

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