searching for a nedm at psi
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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
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 3/28
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
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 4/28
Outline
• The apparatus
• Ongoing measurements and results• UCN - performance• Magnetometers and field control• High voltage and leakage currents
• Ideas for the next generation experiment
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 5/28
Apparatus overview
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 6/28
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)
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 7/28
Outline
• The apparatus
• Ongoing measurements and results• UCN - performance• Magnetometers and field control• High voltage and leakage currents
• Ideas for the next generation experiment
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 8/28
UCN operation
Filling
Monitor
Em
pty
A. Serebrov et al., NIMA 545(2005)490
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 9/28
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
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 10/28
UCN Detector• Monitor mode ~70000 UCN• Emptying ~30000 UCN
• High UCN losses• High depolarization rate
G. Ban et al., NIMA 611 (2009) 280
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 11/28
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
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 12/28
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 13/28
UCN storage time
21
210)( tt
eNeNytN
s 55180
s 2152
2
1
NTE
2
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 14/28
UCN Spin performance
• Rough adjustment of trim coils
• UCN detection spin sequence not yet optimized
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 15/28
UCN Ramsey cycles
Ramsey curve taken with 250 s precession time
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 16/28
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
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 17/28
Outline
• The apparatus
• Ongoing measurements and results• UCN - performance• Magnetometers and field control• High voltage and leakage currents
• Ideas for the next generation experiment
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 18/28
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
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 19/28
Magnetic shield• Four layer Mu-Metal
• Shielding factors:x: 12000, y: 3000, z:8000
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 20/28
• 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
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 21/28
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
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 22/28
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)
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 23/28
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
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 24/28
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=
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 26/28
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
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012
Homogenizer and fiber bundle
Fiber bundle
Beam splitter mounted on the enclosure support
31 vacuum feedthroughsfor optical fibers
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 28/28
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)
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 29/28
Gradients
• STD from six gradiometer pairs
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 33/28
Outline
• The apparatus• Ongoing measurements and results
• UCN - performance• Magnetometers and field control• High voltage and leakage currents
• Ideas for the next generation experiment
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 34/28
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
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 35/28
Testing high voltage
Configuration w bundle -110 kV vacuum 145 kV He/Ne
Configuration wo bundle 198 kV He/Ne 200 kV He/Ne
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 36/28
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
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 37/28
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
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 38/28
Outline
• The apparatus
• Ongoing measurements and results• UCN - performance• Magnetometers• High voltage and leakage currents
• Ideas for the next generation experiment
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 39/28
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
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 40/28
Thermohouse2
• 10×6×8 m3
• EMC shield made of copper• Thermally stabilized
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012 41/28
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
Philipp Schmidt-Wellenburg ORNL, neutron EDM workshop, 11.-13.10.2012
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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