Plan to search for nnbar at WWR-M reactor

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1 Plan to search for nnbar at WWR-M reactor A. Fomin A. Serebrov, O. Zherebtsov, M. Chaikovskii, A. Murashkin, E. Leonova, O. Fedorova, V. Ivochkin, V. Lyamkin, D. Prudnikov, A. Chechkin PNPI, Gatchina, Russia INT Workshop INT-17-69W Neutron-Antineutron Oscillations: Appearance, Disappearance, and Baryogenesis October 23-27,

2 NNbar via UCN muon veto calorimeter pressure, magnetic shield tracker N t 2 discovery potential Storage trap: height 2.5 m, v boundary = 6.8 m/s, diffusion 90 %, abs. in walls

3 UCN density, cm first test experiments with superfluid He ILL [12] PNPI ILL SRIAR PNPI PNPI IAE TUM PNPI IAE JINR Progress of UCN sources ILL [4] PNPI PNPI PNPI [5] first test experiment with SD 2 SD 2 pulse mode LANL-PNPI [8] [6] SD 2 reactor test experiment present ILL [13] [3] SD 2 Mainz [9] years PNPI PNPI PSI-PNPI project [17] projects [15-16] [10] project SD 2 in pulse mode 3

4 Principle of a source UCNs are generated in helium from cold neutrons of 9 Å wavelength (12 K energy). It is correspond with phonon energy: cold neutron produces phonon, practically stopsand becomes an ultracold one. UCN can live in superfluid helium for tens or hundreds of seconds until a phonon be captured. Cold neutrons (9 Å) penetrate through the wall of a trap, but ultracold neutrons (500 Å) are reflected, that is why UCN can be accumulated up to the density defined by the time of storage in the trap filled with superfluid helium. CN =9 Å, T=12 K phonon UCN =500 Å, T=10 3 K 4

MCNP neutron flux calculation results and heat generation in thermal column of WWR-M reactor at 15 MW He Т=1.2 К LD 2 Т=20 К C Т=300 К Pb Т=300 К Ф=4.

5 MCNP neutron flux calculation results and heat generation in thermal column of WWR-M reactor at 15 MW He Т=1.2 К LD 2 Т=20 К C Т=300 К Pb Т=300 К Ф= n/(сm 2 s) Ф( =9 А)= n/(сm 2 sa) Q He =6 W Al, Q Al =13 W LD 2, Q LD2+Al =100 W 19 W C, Q C =700 W Pb, Q Pb =15 кw Ф=10 14 n/(cm 2 s) Q=15 MW 5 5

6 Project of UCN source at reactor WWR-M (PNPI, Gatchina) 6

7 UCN source inside the thermal column of the WWR-M reactor 7

8 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) 8

9 UCN density 10 6 UCN density, cm source trap 35 l trap 350 l ,7 0,8 0,9 1,0 1,1 1,2 1,3 1,4 1,5 T, K He II, s Production of the source 10 8 UCN/s. 9

10 What is the probability for UCÑ to be reflected? R U (1 i ) E U (1 i ) E 2 U U iw 0 W U 0 10

11 We can consider two cases: 1. R 0 (pessimistic case) 2. R R ( 02. ) 08. (optimistic case) U0 iw for n U iw for n 0 11

12 Reflection coefficient for UCÑ ~ R 1,0 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0,0 ~ = ~ ~ ~ E /U 0 =0.1 ~ ~ E /U 0 =0.15 ~ ~ E /U 0 =0.25 ~ ~ E /U 0 =1 12

13 UCN number in the trap for different storage trap radius 5x10 10 number of UCN in the trap 4x x x x storage trap radius, m Storage trap: height 2.5 m, v boundary = 6.8 m/s, diffusion 90 %, abs. in walls

14 UCN density for different storage trap radius 7000 maximum UCN density near the bottom of the storage trap, n/cm storage trap radius, m Storage trap: height 2.5 m, v boundary = 6.8 m/s, diffusion 90 %, abs. in walls

15 density of distribution, arb. un. UCN time of flight for different storage trap radius m 2 m 3 m 4 m 5 m 6 m 0 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 Storage trap: height 2.5 m, v boundary = 6.8 m/s, diffusion 90 %, abs. in walls t, s 15

16 N t 2 for different storage trap radius N t 2, n s 1,6x ,4x ,2x ,0x ,0x ,0x ,0x ,0x , storage trap radius, m Storage trap: height 2.5 m, v boundary = 6.8 m/s, diffusion 90 %, abs. in walls

17 Oscillation period nn 2 ( N t ) T N T ~3 years 0.9 N 0 ( 2.3at 90% CL) (1 2) 10 s (90% CL) nn 9 17

18 UCN facilities at reactor WWR-M 18

19 N t 2 for different storage trap height N t 2, n s 9x x x x x x x x x10 10 horizontal cylinder length 4 m rectangular box length 4 m width 2 m h, m 19

20 Time of flight distribution 7x10 5 density of distribution, arb. un. 6x10 5 5x10 5 4x10 5 3x10 5 2x10 5 1x t, s 20

21 Big gravitational trap for neutron lifetime measurement 21

22 GEANT4 simulation 22

23 GEANT4 simulation 23

24 Design of the setup 24

25 Design of the setup 25

26 Magnetic shielding 26

27 Axial magnetic shielding Numerical calculation of the static axial shielding factor shielding factor, S A shell shield 2 shell shield Static shielding factor for μ metal after demagnetization procedure. The soft Radia (ESRF Grenoble) was used for numerical calculation z, [mm] 27

28 Analytical calculation of the static and dynamic axial shielding factor the results are presented in the table 1 shell shield dynamic static Active compensation rate PNPI (project) dynamic static Active compensation rate 28

29 Analytical calculation of the static and dynamic transverse shielding factor the results are presented in the table PNPI (project) 1 shell shield dynamic static Active compensation rate dynamic static Active compensation rate 29

30 The final configuration of our magnetic shield µ metal L=4950 mm D=2730 mm 30

31 Magnetic shielding of multi-chamber EDM spectrometer 31

32 Magnetic shielding 32

33 Magnetic shielding 33

34 Magnetic shielding assembly 34

35 Magnetic shielding assembly 35

36 Vacuum chamber 36

37 UCN trap 37

38 Veto system 38

39 Progress of UCN source at reactor WWR-M Project leader: A. Serebrov 39

40 Cryogenic complex at WWR-M reactor Hall of the cryogenic equipment Helium liquefier and refrigerator Vacuum equipment Cryostat Compressors Receivers, cryogenic building 40

41 The full-scale technological model of UCN source with superfluid helium is mounted 41

42 Recent experiment on full-scale model Temperature 42

43 Vacuum module manufacture

44 UCN source design / manufacture Low temperature (15 K) module with liquid deuterium moderator Under construction Will be ready till December

45 UCN source design / manufacture Low temperature (1 K) module with superfluid helium Under construction Will be ready till December

46 WWR-M reactor thermal column 46

47 Thermal column measurements 3D scan was done from 7 points without contacting radioactive thermal column 47

48 Design of the setup 48

49 Size matters ILL ESS WWR M ESS ILL WWR M 49

50 Conclusion 1. Designed storage trap for NNbar oscillation experiment at reactor WWR-M: horizontal cylinder with diameter 2 m, length 4 m. 2. Increase of the experiment sensitivity is about times to ILL level. 3. Oscillation period for 3 years: ( ) 10 s (90% CL) nn 9 The work is supported by the Russian Foundation for Basic Research, grant no a. 50

Project of ultracold neutron source with superfluid helium at WWR-M reactor (PNPI, Gatchina) and scientific research program А.P.

Project of ultracold neutron source with superfluid helium at WWR-M reactor (PNPI, Gatchina) and scientific research program А.P. Serebrov UCN2010 International Workshop on UCN and Fundamental Neutron