Neutron EDM Experiment at the Paul Scherrer Institute Jacek Zejma - - PowerPoint PPT Presentation

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Neutron EDM Experiment at the Paul Scherrer Institute Jacek Zejma - - PowerPoint PPT Presentation

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Neutron EDM Experiment at the Paul Scherrer Institute Jacek Zejma on behalf of the nEDM collaboration SSP2012, Groningen Jacek Zejma Jagiellonian University Krakw Motivation P

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SSP2012, Groningen Jacek Zejma

Jagiellonian University Kraków

Neutron EDM Experiment at the Paul Scherrer Institute Jacek Zejma

  • n behalf of

the nEDM collaboration

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Jacek Zejma SSP2012, Groningen

Motivation

2

+ _ + _

P

+ _

T

+ _

R

  • ∙ ̂
  • ∙ ̂

Non-zero nEDM value violates both P and T symmetries.

  • Motivation of neutron EDM measurements

has been already presented in several interesting talks.

~ 10

  • ~ 10
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Jacek Zejma SSP2012, Groningen

Motivation

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First nEDM experimental estimation:

  • E. M. Purcell and N. F. Ramsey (1950) dn < 3·10−18 e·cm

First dedicated nEDM measurement:

Smith, Purcell, Ramsey (1957) dn < 5·10–20 e·cm

Current experimental limitation:

RAL-Sussex-ILL collaboration (2006) dn < 2.9·10–26 e·cm.

Problem of last experiments: Limited statistics dn=(+0.2 ± 1.5 ± 0.7)·10-26 e·cm.

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Jacek Zejma SSP2012, Groningen

Experiment at PSI

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General idea:

  • continuation of the successful

Sussex/RAL/ILL experiment.

  • much more intense UCN source
  • better control of the systematics

Paul Scherrer Institute:

  • new UCN source with intensity of

above 1000 cm-3 (typical density at ILL is 10 cm-3).

Bernard Lauss’s talk on Wednesday (17:20).

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Jacek Zejma SSP2012, Groningen

Experiment at PSI

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Last result: dn < 2.9·10–26 e·cm. Aim sensitivity of the experiment at Paul Scherrer Institute:

  • Intermediate:

dn < 5 · 10-27 e·cm (95% C.L.)

  • Finale:

dn < 5 · 10-28 e·cm (95% C.L.)

d ≈ 0.7 µm

if neutron is enlarged to the size of the Earth.

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Jacek Zejma SSP2012, Groningen

nEDM experiment at PSI

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Collaboration of 13 laboratories 51 scientists (including PhD students)

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Jacek Zejma SSP2012, Groningen

Measurement principle

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Larmor precession of the neutron spin

  • ↑↑ ↑↑ , if ↑↑ .
  • ↑↓ ↑↓ , if ↑↓ .

∆ 2 ↑↑ ↑↓ 2 ↑↑ ↑↓

∆

  • , if ↑↑ ↑↓ and ↑↑ ↑↓.

~ ⟹ ∆ ~ ∙ .

  • ωL
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Jacek Zejma SSP2012, Groningen

Measurement principle

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Sample of polarized neutrons with constant (1 μT) i (12 kV/cm) field. RF pulse with 30Hz. Spin rotation by ⁄ to horizontal plane.

Free precession of neutron spin by about 120150 s. ↑↑ or ↑↓ . Second 2s long RF pulse. Rotation of spin ⁄ to vertical if dn=0. Neutron polarization analysis.

The Ramsey method of separated oscillating fields 4. 3. 2. 1. 5.

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Jacek Zejma SSP2012, Groningen

Measurement principle

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The Ramsey method of separated oscillating fields

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

Amount of registered neutrons with polarization equal +1 for E=0. x – working points C1 C2 Measurement accuracy:

  • 2
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Jacek Zejma SSP2012, Groningen

Measurement principle

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The Ramsey method of separated oscillating fields

C1 C2 Measurement accuracy:

  • 2
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Jacek Zejma SSP2012, Groningen

nEDM experiment at PSI

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System components:

  • Ultra-cold neutrons:
  • guides, precession chamber, valves.
  • spin polarization and analysis.
  • detection system.
  • Magnetic field:
  • μ-metal shield.
  • main and compensation (trim) coils.
  • magnetometers to measure field and its gradients.
  • Electric field:
  • power supply and electrodes.
  • leakage current measurement.
  • high-voltage resistant materials
  • Data acquisition system:
  • sequence of steps in a measurement cycle.
  • control of all subsystems.
  • collection of data.
  • 2
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Jacek Zejma SSP2012, Groningen

nEDM experiment at PSI

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Thermo-house with stabilized temperature. Apparatus with precession chamber 0.1°C Control room 1°C

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Jacek Zejma SSP2012, Groningen

nEDM experiment at PSI

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Jacek Zejma SSP2012, Groningen

nEDM experiment at PSI

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Jacek Zejma SSP2012, Groningen

nEDM experiment at PSI

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Switch connects UCN storage volume with

  • UCN source
  • Detection system
  • Pumping system
  • Pressure gauge
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Jacek Zejma SSP2012, Groningen

nEDM experiment at PSI

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UCN detection system

  • 6Li enriched scintillators

n + 6Li → 3H + α

UCN

3H

6Li

6Li depleted 6Li enriched

110 µm 60 µm

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Jacek Zejma SSP2012, Groningen

nEDM experiment at PSI

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Using nonmagnetic materials

  • Tests at PTB Berlin

∆Bpp ≈ 200 pT After demagnetization ∆Bpp ≈ 20 pT

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Jacek Zejma SSP2012, Groningen

nEDM experiment at PSI

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¼ wave plate linear polarizer Hg lamps polarization cell HgO source B0 ≈ 1μT PM

~ 8 Hz

τ = 140s

199Hg co-magnetometer

50 fT/100s

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Jacek Zejma SSP2012, Groningen

nEDM experiment at PSI

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199Hg co-magnetometer

50 pT

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Jacek Zejma SSP2012, Groningen

nEDM experiment at PSI

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4 HV-resistant Cs-mag 8 Cs-mag.

133Cs magnetometers

Measurement of

  • field gradients,
  • rapid field changes.

100 fT/1s

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Jacek Zejma SSP2012, Groningen

nEDM experiment at PSI

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Magnetic field shielding

  • Passive:
  • 4 layers of μ-metal
  • Active:
  • Surrounding field compensation (6 coils)
  • 30 trim coils

Field mapping. Longitudinal neutron spin relaxation T1 = 3600 s, Transverse relaxation T2 = 560 s.

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Jacek Zejma SSP2012, Groningen

nEDM experiment at PSI

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Mean values of Hg atoms and UCNs in the precession chamber differ by ∆ ≈ 2.3 mm – this is a source of uncompensated field drifts:

  • 1

∙ 1 ∙ ∆ Measurement of gradient: < 2.8 fT/cm What corresponds to systematic effect 2.5 ∙ 10e·cm With CS magnetometers we can

  • btain accuracy

0.9 ∙ 10e·cm

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Jacek Zejma SSP2012, Groningen

nEDM experiment at PSI

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Towards n2EDM

  • 1. Better magnetometry system.
  • 2. Active magnetic shielding
  • 3. Simultaneous measurement with E parallel and anti-parallel to B in the

symmetric double-chamber system.

  • 4. Simultaneous neutron “up” and “down” spin measurement.
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Jacek Zejma SSP2012, Groningen

nEDM experiment at PSI

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Summary

  • 1. UCN source is ready for delivering neutrons.
  • 2. All sub-systems tested and ready to work.
  • some improvements and tests are still being prepared.
  • 3. Expected accuracy obtained in the measurement 2012-2013

… 2 2 ∙ 10e·cm.

  • 4. Investigations regarding next step are in progress.
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Jacek Zejma SSP2012, Groningen

nEDM experiment at PSI

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Thank you

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Jacek Zejma SSP2012, Groningen

nEDM experiment at PSI

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Dedicated measurement for estimation of ∆

  • 1

∙ 1 ∙ ∆ ∆ = 2.3 ± 0.1 mm

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Jacek Zejma SSP2012, Groningen

nEDM experiment at PSI

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Effect Status (⋅10‐27 ecm)

(Feb. 2012)

Leakage Current 0.00 ± 0.05 Uncompensated B drift 2.9 ± 8.6 vxE UCN ± 0.1 Electric Forces 0. ± 0.4 Hg EDM 0.02 ± 0.06 Hg Light Shift 0.00 ± 0.05 Quadrupole Difference 1.3 ± 2.4 Dipoles ± 3 Total 4.2 ± 9.4

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Jacek Zejma SSP2012, Groningen

nEDM experiment at PSI

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  • 5

5 15 25 35 45 100 200 300 400 500

Time (ns) Signal (mV) Neutron pulse

  • 5

5 15 25 35 45 100 200 300 400 500

Time (ns) Signal (mV) Čerenkov pulse

Signals from a UCN detector

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Jacek Zejma SSP2012, Groningen

nEDM experiment at PSI

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Long term magnetic field drifts measured with both Hg and Cs magnetometers