1. FLNP of JINR, Dubna, Russia
Neutron gravity experiments and tests of the Weak Equivalence Principle
A. Frank
FLNP of JINR, Dubna, Russia
ESS Science Symposium on Neutron Physics at Long Pulse Spallation Sources
25-27 March 2013
PSI October, 11-14, 2010

2. Outline Free Fall Universality tests (short review)
Neutrons and gravity
Status of new Neutron Gravity experiment
Proposal of the future free fall experiment with UCN.
A.Frank. nppatlps-2013, 27 March 2013 July

3. Free Fall Universality tests (short review) Neutrons and gravity
Status of new Neutron Gravity experiment
Proposal of the future free fall experiment with UCN.
A.Frank. nppatlps-2013, 27 March 2013 July

4. A.Frank. nppatlps-2013, 27 March 2013
P.G. Roll, R. Krotkov, and R.H. Dicke, Ann. Phys. (N.Y.) 26, 442 (1964)
S.Carusotto, V.Cavassinni, A.Mordacci et. al. Phys.Rev Lett. 69, 1722 (1992)
S. Schlamminger, K.-Y. Choi, T. A. Wagner, et al. Phys.Rev Lett 100, (2008)
S. Fray, C. A. Diez, T. W. Hänsch, and M. Weitz. arXiv:physics/ v.2 (2005)
J. G. Williams, S.G. Turyshev, and D. H. Boggs, Phys.Rev Lett 93, (2004)
G. L. Smith, C. D. Hoyle, J. H. Gundlach, E. G. Adelberger, B. R. Heckel, and H. E. Swanson. Phys. Rev. Rev. D 61, (1999)
A.Frank. nppatlps-2013, March 2013

5. Free Fall Universality tests (short review) Neutrons and gravity
Status of new Neutron Gravity experiment
Proposal of the future free fall experiment with UCN.
A.Frank. nppatlps-2013, March 2013

6. A.Frank. nppatlps-2013, 27 March 20131.
g =935  70cm/sec2 2.
J.W.Dabbs,J.A.Harvey, D.Pava and H.Horstmann, 1965
g(002)=973.1  7.4cm/sec2
g(100)=975.1  3.1cm/sec2
gloc = cm/sec2
A.Frank. nppatlps-2013, March 2013

7. A.Frank. nppatlps-2013, 27 March 2013
L.Koester, 1976
Knowing the neutron mass m and local free fall acceleration gloc one can obtain the effective scattering length beff
Coherence length b was measured also in the neutron scattering experiment with Pb and Bi. Thus the equivalence factor  was found
1- = 310-4
V.F.Sears,1982
J. Schmiedmayer, NIM A 284, (1989)  = 
A.Frank. nppatlps-2013, March 2013

8. Koester’s experiment and the problem of n-e scattering
When the value of bcoh extracts from the total cross section data it is necessary to take into account the n-e scattering. For the case of Pb and Bi correspondent corrections are of the order 1%. Consequently, if one aim to reach 10-4 in precision of bcoh the amplitude of n-e scattering must be known with precision of 1%.
It is not evident that bne is known with such precision even now
Schmiedmayer used statistically inconsistent data for n-e scattering
A.Frank. nppatlps-2013, March 2013

9. Koester’s experiment and effective potential
What is a precision of the above equation for the effective potential U?
V.F.Sears (1982); M. Warner, J.E Gubernatis. (1985)
Lax, 1951
Theory: (estimation for lead at Vn  400 m/sec) – corrections of the order of 510-5
There are no any experiments for the test of theory with precision better
than some percents
A.Frank. nppatlps-2013, March 2013

10. Neutron Interferometric Experiments (COW – type experiment)
R.Colella, A,W.Overhauser and S.A. Werner (COW), 1975
The experimentally obtained values for the gravitationally induced phase factor were lower
than the theoretically expected value by 1.5% for the skew-symmetric interferometer data
and 0.8% for the symmetric interferometer data in measurements with relative uncertainties
of 0.12% and 0.11%, respectively.
K.S.Litrell, B.E.Allman and S.A.Werner, 1997
A.Frank. nppatlps-2013, March 2013

11. 1- = (1±9)10-3
A.Frank. nppatlps-2013, March 2013

12. Dubna-ILL-Kurchatov experiment of 2006
E0  E E
E0 + mgH
E0 –ħ1 +mgH H
E0 –ħ2 +mgH g
The idea was to compare the energy mgH with energy ħΩ
A.I. Frank, P. Geltenbort, M. Jentschel,et al. JETP Letters, 86, 225 (2007)
A.Frank. nppatlps-2013, March 2013 12

13. Moving diffraction grating as a nonstationary devicez y
L – period of grating E 1 -1 2 -2
A.Frank. nppatlps-2013, March 2013 13

14. Moving (rotating) diffraction grating as a nonstationary device
UCN
Monochromator
Phase π -grating n L d E 1 -1
where N is number of groves
N = 75398
A.Frank. nppatlps-2013, March 2013 14

15. Fabry-Perot interferometers (Neutron Interference filters) as a spectrometric device
Energy of the state 1 2
Substrate
A.Frank. nppatlps-2013, March 2013

16. Experimental results Bth = 0.304203 Bexp = 0.3037 ± 0.00065
A.I. Frank, P. Geltenbort, M. Jentschel,et al. JETP Letters, 86, 225 (2007)
A.Frank. nppatlps-2013, March 2013

17. Free Fall Universality tests (short review) Neutrons and gravity
Status of new Neutron Gravity experiment
Proposal of the future free fall experiment with UCN.
A.Frank. nppatlps-2013, March 2013

18. Comparing the energy mggnH with energy ħΩ as before
Combination of Neutron Interference Filters with peculiar TOF spectrometry
Flux modulation
TOF base E1
Count-rate oscillations on a detector E2 E3
E1>E2>E3
A.Frank. nppatlps-2013, March 2013 18

19. Comparing the energy mggnH with energy ħΩ as before
Combination of Neutron Interference Filters with peculiar TOF spectrometry
Flux modulation
TOF base E1
Count-rate oscillations on a detector E2 E3
E1>E2>E3
Not sensitive to fluctuations of:
Background
Intensity
Efficiency registration of neutrons
A.Frank. nppatlps-2013, March 2013 19

20. 20 Experiment. Part I Calibration
Modulation frequency 75Hz
Monochromator
Detector
Calibration
Variation of the monochromator vertical position leads to changing of the UCN energy, time of flight and total phase of the count rate oscillation
A.Frank. nppatlps-2013, March 2013 20

21. Experiment. Part II (idea)
Detector
Monochromator
Detector
Monochromator
grating
grating
The count rate oscillation phase of the UCN which energy
shifted by rotating grating must be compared with the calibration curv
A.Frank. nppatlps-2013, March 2013 21

22. Experiment. Part II (idea)
Detector
Monochromator
Detector
Monochromator
grating
grating
The count rate oscillation phase of the UCN which energy
shifted by rotating grating must be compared with the calibration curv
Unfortunately -1 order of diffravtion is accopanied by the +1 and diffraction.
orders of higher orders
A.Frank. nppatlps-2013, March 2013 22

23. Detector
Monochromator
grating
Wide analyzer
Using special 9-layers filter with wide transmission band it is possible to select the UCN of -1 diffraction order wide
A.Frank. nppatlps-2013, March 2013 23

24. Experiment. Part II (idea)
Detector
Monochromator
grating
Wide analyzer ΔH
The count rate oscillation phase of the UCN which energy shifted by the grating rotating with different frequency must be compared with the calibration curv
A.Frank. nppatlps-2013, March 2013 24

25. New gravitational spectrometer of UCN.
A.Frank. nppatlps-2013, March 2013

26. Chopper-modulator
Stability of the modulation frequency is better than 10-4
A.Frank. nppatlps-2013, March 2013 26 26 26

27. Grating manufactured by the Qudos technology LTD (2012)
A.Frank. nppatlps-2013, March 2013

28. Experiment of 2011. A.Frank. nppatlps-2013, 27 March 2013
Oscillation of the count rate. Modulation frequency 75Hz, neutron time of flight 150 ms
Dependence of the count rate oscillation
phase on the modulation frequency
A.Frank. nppatlps-2013, March 2013

29. 29 Experiment of 2011. A.Frank. nppatlps-2013, 27 March 2013
Detector
Monochromator
grating
Wide analyzer
A.Frank. nppatlps-2013, March 2013 29

30. Experiment of 2011.
Detector
Monochromator
grating
Wide analyzer
Rate of the collection of accuracy 1.5×10-2 per day
A.Frank. nppatlps-2013, March 2013 30

31. Experiment of 2012. A.Frank. nppatlps-2013, 27 March 2013
Amplitude of the count rate oscillation
in dependence of position of analyzer.
Geometry of calibration.
Count rate in the geometry of calibration
with rotating chopper- modulator
Scanning curve of -1 diffraction order with
the grating spinning at 6300 rpm..
A.Frank. nppatlps-2013, March 2013

32. Experiment of 2012. A.Frank. nppatlps-2013, 27 March 2013
Geometry of calibration
Oscillation of the count rate. Modulation frequency 84Hz, statistic collection time 3200 s,
error for the phase measurement 0.01rad, total phase about 80 radian
A.Frank. nppatlps-2013, March 2013

33. Experiment of 2012.
A.Frank. nppatlps-2013, March 2013

34. Experiment of 2012.
A.Frank. nppatlps-2013, March 2013

35. The main results of 2012
The full scale test measurements with new spectrometer was performed.
2. The rate of the collection of statistical accuracy, was obtained as 5×10-3 per day. That is enough to collect statistical accuracy of the order of 5×10-4 during two cycle of statistic collection at PF2 source.
3. The systematic effect due to admixture of zero order to the spectrum of minus first order was found. This problem may be probably solved by manufacturing of the grating with
a) smaller inner diameter, what as we hope will decrease the intensity of UCN bypasses the grating
b) with larger space frequency what will increase separation between the zero (if it will be) and minus first orders.
A.Frank. nppatlps-2013, March 2013

36. The possible improvement
The grating with larger number of groves ( instead of 75398) will be used. That will increase the energy transform
The monochromator with position of transmission line at 95nev will be used instead of monochromator with 105 nev line.
The TOF base will be increased from to 70 to 90 cm
All that will double the collection rate of the
statistical accuracy.
A.Frank. nppatlps-2013, March 2013

37. Free Fall Universality tests (short review) Neutrons and gravity
Status of new Neutron Gravity experiment
Proposal of the future free fall experiment with UCN.
A.Frank. nppatlps-2013, March 2013

38. What was measured in the previous experiments
Koester
m is known tabular data of neutron mass
ILL-Dubna-Kurchatov inst.
It is seems very attractive to perform experiment where mi/mg will be measured without any additional information
The best is the direct measurement of gn
A.Frank. nppatlps-2013, March 2013

39. Neutron fountain for the measuring of gn
For the measure of time it was proposed to use
Yu.N.Pokotilovsky, 1994
We propose to modify the idea of Yu. P
1. Interference filter with number of lines
1. Interference filter with single line
2. Simple chopper- modulator Instead of
pseudo-random chopper
2. Correlation time of flight spectroscopy
with pseudo-random chopper
Detector
3. Only the phase of the intensity oscillation will be measured.
3. Because the energy of the lines is unknown, it was proposed to vary height of detector for calculation of g.
A.Frank. nppatlps-2013, March 2013

40. Neutron fountain for the measuring of gn
Simple chopper- modulator Instead of
pseudo-random chopper
Only the phase of the intensity oscillation will be measured.
Dependence of phase on the height of monochromator
gives the value of g
Detector
Alternative possibility: instead of variation of the height of monochromator it is possible to shift energy by rotating grating
Vertical mirror may be added
A.Frank. nppatlps-2013, March 2013

41. Neutron fountain for the measuring of gn
Simple chopper- modulator Instead of
pseudo-random chopper
Solid angle  
Only the phase of the intensity oscillation will be measured.
Dependence of phase on the height of monochromator
gives the value of g
Detector
Vertical mirror may be added
That will give a gain in the intensity of the order of magnitude
A.Frank. nppatlps-2013, March 2013

42. Main advantages of this approach is that absolute measurements are needed only for
Frequency of the beam modulation
The value H of the variation in the position of monochromator
Or (alternatively) the frequency  of quantum modulation due to diffraction by a moving grating
Estimation shows that precision of the order 10-5 may be achieved at PF2
A.Frank. nppatlps-2013, March 2013

43. A. I. Frank, S. Goryunov, G. V. Kulin, D. Kustov
A.I.Frank, S.Goryunov, G.V.Kulin, D.Kustov*) Frank Laboratory of Neutron Physics, JINR, Dubna, Russia *) Institute of Nuclear Research, Kiev, Ukraine P. Geltenbort, M.Jentschel ILL, Grenoble, France A.N.Strepetov NRC “Kurchatov Institute”, Moscow, Russia.

44. Thank you for your attention!

45. 45

46. Two aspects of the Universality of Free Fall (UFF) experimental tests
Tests of the equivalence principle
Probes for the new interactions that violate the UFF
A.Frank. nppatlps-2013, March 2013