Ucn magnetic storage and neutron lifetime
Download
1 / 39

UCN magnetic storage and neutron lifetime - PowerPoint PPT Presentation


  • 59 Views
  • Uploaded on

UCN magnetic storage and neutron lifetime. V.F.Ezhov Petersburg Nuclear Physics Institute, Gatchina, Russia. ( ITEP - 2007 ).

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' UCN magnetic storage and neutron lifetime' - yetta-oneill


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Ucn magnetic storage and neutron lifetime
UCN magnetic storage and neutron lifetime

V.F.Ezhov

Petersburg Nuclear Physics Institute, Gatchina, Russia.

(ITEP - 2007)


After neutrino decoupling and electron-positron annihilation, neutron decay (lifetime ~ 880 sec) begins to deplete neutrons. Once temperature drops below 1.3·109 K, at t ~ 98 s, the rate of two-body and three-body reactions become negligible compared to the one-body reaction. Only neutron decay then dominates.


Neutron decay and Standard Model annihilation, neutron decay (lifetime ~ 880 sec) begins to deplete neutrons. Once temperature drops below 1.3·10

CKM mixing matrix:

W.Marciano

A.Sirlin

PRL 96, 032002 (2006)

Required experimental accuracy for n and A

has to be about 10-3 and better.


The best results for neutron lifetime

N beam: annihilation, neutron decay (lifetime ~ 880 sec) begins to deplete neutrons. Once temperature drops below 1.3·10

886.8±1.2±3.2 (NIST, 2003)

889.2±4.8 (Sussex-ILL, 1995)

UCN storagein material trap:

878.5±0.7± 0.3 (PNPI-ILL,2004)

885.4±0.9±0.4 (KI-ILL, 1997)

882.6±2.7 (KI-ILL, 1997)

888.4±3.1±1.1 (PNPI, 1992)

887.6±3.0 (ILL, 1989)

The best results for neutron lifetime

Particle data 2003

(without PNPI - ILL,2004):

n = (885.70.8) s


Neutron decay and Standard Model (status in 2003) annihilation, neutron decay (lifetime ~ 880 sec) begins to deplete neutrons. Once temperature drops below 1.3·10


Data analysis with the most precise measurements of neutron decay

nVud

ΔVud=2.4σ

00Vud

Δ=2.4σ

The improvement of the accuracy of A-measurements

(factor of 3 or more) is extremely important.


Reflection of UCN by magnetic barrier decayW. Paul, in Proc. Int. Conf. on Nuclear Physics and Physics of Fundamental Particles, Chicago, 1951. V.V. Vladimirskii, Sov.Phys. - JETP 12, 740, 1961

  • Magnetic potential

  • For magnetic moment of neutron

  • Nuclear potential of Be

  • Magnetic field 1 T reflects neutrons up to 3.4 m/s, as Al.

  • + for and

  • – for


Probability of depolarization
Probability of depolarization decay

  • Precession of magnetic moment

  • Adiabatic condition

  • ( -- is the velocity of neutron)

  • For case of strong field

  • (B = 1T), B = 1T/mm and velocity v = 3.4 m/s one can receive next relation for adiabatic condition:

  • 1.83108 >> 3.4103.


“UCN storage in the vessel with magnetic wall.” decay

JETP Letters 23(3), 1976

Y.Y.Kosvintsev, Y.A.Kushnir, V.I.Morozov

=25±2 sec


44 8 369 1986

Y.G.Abov, V.V.Vasil’ev, V.V.Vladirski, I.B.Rozhnin decay

JETP Letters, 44(8), 369, (1986)

Ю.Г.Абов, В.В.Васильев,В.В.Владимирский, И.Б.РожнинПисьма ЖЭТФ, т.44(8), 369, (1986).

Main problem of the current systems is too large electric power (about 100 kWt)

Main result:

It was shown firstly that it’s possible to obtain τ > 700 sec in the magneto-gravitational trap.


W paul f anton l paul s paul and w mampe z f physik c 45 25 1989
W. Paul, F. Anton, L. Paul, S. Paul, and W. Mampe, decayZ. f. Physik C 45, 25(1989).

Sextupole torus. Rs orbit of circulating neutrons.

τ= 877 ± 10 s

The achieved usable fieldof 3.5 T permits the confinement of neutrons in the velocity range of 5 – 20m/s corresponding to a kinetic energy up to 2 * 10-6 eV.


P.R. Huffman, C.R. Brome, J. S. Butterworth, K. J. Coakle, decayM. S. Dewey, S.N. Dzhosyuk, R. Golub, G. L. Greene, K. Habicht,S.K. Lamoreaux, C.E.H. Mattoni, D.N. McKinsey, F. E. Wietfeldt,& J.M. DoyleNature 403, 62, 2000

The main problems:

1. Filling and empting. If one use superconducting system, then he can’t switch on field too fast.

2. Huge setup and small storage volume

The trapping region is filled with superfluid 4He, which is used to load neutrons

into the trap and as a scintillator to detect their decay. Neutrons have a lifetime

in the trap of

τ = 750+330−200 s.


Magnetic wall
Magnetic wall decay

1 – permanent magnet

2 – magnetic field guide


2004 decay



Experimental advantage s
Experimental decayadvantages

  • To control the depolarization of UCN we cover the inner trap walls with thin lay of fomblin that reflects depolarized UCN. In this case the depolarized UCN penetrate the magnetic barrier inside the solenoid and are measured by the UCN detector installed below the solenoid. Hence this detector may be used as monitor for depolarization losses during neutron storage.

  • Monitor of trap filling

  • Preliminary neutron spectrum preparation

  • Absence of neutrons heating at the moment of magnetic shutter switching on.

  • Possibility to divide fast and spin-flipped neutrons


Problems

Cleaning. Magnetic wall is an ideal mirror, as a result there are stationary trajectories.

Efficiency of depolarized neutrons collection.

Problems


First stage: (2006) there are stationary trajectories.

Neutron guide diameter 20 mm

Without forced spin-flip

Second stage: (2007)

Neutron guide diameter 60 mm

Forced spin-flip is switched on


Lifetime no depended method of efficiency measuring there are stationary trajectories.


2005-2006 there are stationary trajectories.

Volume 15 l

Neutron elevator Storage time

874.6 -1.6 +4 sec.

decay = 878.4  1.8 s.

ε = 0.90±0.02


…………………………………………………….…………………………………………………….


877.4±1.7 s.…………………………………………………….


878.6±1.8 s.…………………………………………………….


The best results for neutron lifetime1

N beam:…………………………………………………….

886.8±1.2±3.2 (NIST, 2003)

889.2±4.8 (Sussex-ILL, 1995)

UCN storagein material trap:

878.5±0.7± 0.3 (PNPI-ILL,2004)

885.4±0.9±0.4 (KI-ILL, 1997)

882.6±2.7 (KI-ILL, 1997)

888.4±3.1±1.1 (PNPI, 1992)

887.6±3.0 (ILL, 1989)

The best results for neutron lifetime

Particle data 2003

(without PNPI - ILL,2004):

n = (885.70.8) s

Magnetic trap (2007)

878.2  1.6 s.

Preliminary


Our plans
Our plans…………………………………………………….

  • 2008 – increasing the volume to one order and increasing of magnetic barrier to 2 times

  • 2009 – run with new trap


V.F.Ezhov,…………………………………………………….1 B.A.Bazarov,1 P.Geltenbort,2 F.J.Hartman,3 N.A.Kovrizhnykh,4 A.Z.Andreev, 1 G.Ban5, A.G.Glushkov, 1 M.G.Groshev, 1 V.A.Knyazkov, 1 G.D.Krygin, 1 A.R.Muller, O.Naviliat-Cuncic5 S.Paul, 3 R.Picker, 3 V.L.Ryabov, 1 A.P.Serebrov, 1 O.Zimmer3,2

1 - Petersburg Nuclear Physics Institute, Gatchina, Russia.

2 - Institut Laue-Langevin, Grenoble, France.

3 - Technical University, Munich, Germany.

4 - Reseach Institute of electrophysical apparatus,

S-Petersburg, Russia.

5 - Caen University, France


2006-2007…………………………………………………….

Small diameter of neutron guide

ε = 0.90±0.02

decay = 878.4  1.8 s.

877.4±1.7 s.

Increased diameter of neutron guide

878.6±1.8 s.

decay = 878.2  1.6 s.

Preliminary


ad