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- A. Fomin
antineutron oscillations using a projected UCN source at the WWR-M - - PowerPoint PPT Presentation
antineutron oscillations using a projected UCN source at the WWR-M - - PowerPoint PPT Presentation
Experiment on search for neutron- antineutron oscillations using a projected UCN source at the WWR-M reactor A. Fomin Project leader: A. Serebrov PNPI, Gatchina, Russia International Workshop "Probing Fundamental Symmetries and
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ILL beam experiment
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ESS beam experiment
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NNbar via UCN
Storage trap: height 2.5 m, vboundary = 6.8 m/s, diffusion 90 %, abs. in walls 310-5 Nt2 – discovery potential muon veto calorimeter pressure, magnetic shield tracker
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6 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 10
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[13] [8] [6] [5] [4] [12] [15-16] present [3] [9] [10] first test experiment with SD2
PNPI
SD2 Mainz project [17] projects
ILL ILL
first test experiments with superfluid He test experiment project SD2 in pulse mode SD2 pulse mode SD2 reactor
PSI-PNPI PNPI PNPI LANL-PNPI SRIAR ILL ILL IAE TUM IAE JINR PNPI PNPI PNPI PNPI PNPI PNPI UCN density, cm
- 3
years
Progress of UCN sources
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7 He Т=1.2 К Pb Т=300 К Ф=1014 n/(cm2s) Q=15 MW Al, QAl=13 W C, QC=700 W Pb, QPb=15 кW 19 W
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LD2 Т=20 К C Т=300 К LD2, QLD2+Al=100 W
MCNP neutron flux calculation results and heat generation in thermal column of WWR-M reactor at 15 MW
Ф=4.5∙1012 n/(сm2s) Ф(=9 А)=3∙1010 n/(сm2sA) QHe=6 W
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Project of UCN source at reactor WWR-M (PNPI, Gatchina)
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MC model of the source
(1) source chamber; (2) neutron guide; (3) UCN trap; (4) membrane in front of the inlet to the UCN trap;(5) pipe for filling the chamber; (6) pipeline for evacuation of the chamber (UCN gravitational shutter) 1 2 3 4 5 6
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0,7 0,8 0,9 1,0 1,1 1,2 1,3 1,4 1,5 10
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600 T, K UCN density, cm
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100 23.3 6.7
He II, s
UCN density
source trap 35 l trap 350 l Production of the source 108 UCN/s.
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What is the probability for UCÑ to be reflected?
2
1 1 (1 ) 1 1 (1 ) U i E R U i E
W U U U iW
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We can consider two cases:
1. (pessimistic case) 2. (optimistic case)
R 0
0 2 0 8 R R ( . ) .
U iW for n U iW for n
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Reflection coefficient for UCÑ
1 2 3 4 5 6 7 8 9 10 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0
E/U0=0.1 ~ ~
=0.2
~ ~
~
E/U0=0.15 E/U0=0.25 E/U0=1
R
~ ~ ~ ~ ~ ~
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UCN number in the trap for different storage trap radius
1 2 3 4 5 6 1x10
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2x10
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3x10
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4x10
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5x10
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storage trap radius, m number of UCN in the trap
Storage trap: height 2.5 m, vboundary = 6.8 m/s, diffusion 90 %, abs. in walls 310-5
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UCN density for different storage trap radius
Storage trap: height 2.5 m, vboundary = 6.8 m/s, diffusion 90 %, abs. in walls 310-5 1 2 3 4 5 6 1000 2000 3000 4000 5000 6000 7000 storage trap radius, m maximum UCN density near the bottom
- f the storage trap, n/cm
3
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0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 100000 200000 300000 400000 500000 600000
density of distribution, arb. un. t, s
1 m 2 m 3 m 4 m 5 m 6 m Storage trap: height 2.5 m, vboundary = 6.8 m/s, diffusion 90 %, abs. in walls 310-5
UCN time of flight for different storage trap radius
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Nt2 for different storage trap radius
Storage trap: height 2.5 m, vboundary = 6.8 m/s, diffusion 90 %, abs. in walls 310-5 1 2 3 4 5 6 0,0 2,0x10
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1,2x10
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1,4x10
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1,6x10
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N·t
2, n·s
storage trap radius, m
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2
( )
nn
N t T N
Oscillation period
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(1 2) 10 s (90% CL)
nn
0.9 ~ 3 T years 2.3 ( at 90% CL) N
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UCN facilities at reactor WWR-M (preliminary)
nEDM n , Gravitrap n , magnetic trap nn nñ
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UCN facilities at reactor WWR-M (preliminary)
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Conclusion
- 1. Optimal size of the storage trap for NNbar
- scillation experiment at reactor WWR-M:
height 2.5 m, radius 3 m.
- 2. Increase of the experiment sensitivity is about
20 80 times to ILL level.
- 3. Oscillation period for 3 years: