Studying the neutron quantum states in the gravitational field “using ...

flab.phys.nagoya.u.ac.jp

Studying the neutron quantum states in the gravitational field “using ...

Studying the neutron quantum states

in the gravitational field

“using nuclear emulsion technique”

• Motivations

• Results obtained with CR39

• Perspectives with emulsion

Nagoya, 2006

I.Laktineh, IPNL 1


"Let us consider another possibility, an atom held together by gravity

alone. For exemple, we might have two neutrons in a bound state.

When we calculate the Bohr radius of such an atom, we find that it

would be 10 8 light years, and that the atomic binding energy would be

10 -70 Rydbergs. There is then little hope of ever observing

gravitational effects on systems which are simple enough to

be calculable in quantum mechanics."

Brian Hatfield, in "Feynman Lectures on Gravitation" ;

R.P. Feynman, F.B. Morinigo, W.G. Wagner, Ed. Brian Hatfield

Addison-Wesley Publishing Company, 1995, p. 11

Nagoya, 2006

I.Laktineh, IPNL 2


Neutrons in gravitational field

Academic exercise

E , n

peV

3,32

V( z)

=

mgz

2,46

1,41

0

14 24 32 z,

µ m

z

h

2gm

2

3

0

= = 5,87 µ m

2

E

qc

n

≈ 3 ⋅ g n−

Nagoya, 2006

⎛9m

⎞ ⎛ ⎛ 1⎞⎞

⎜ ⎟ ⎜ ⎟

8

⎜π

h

4


⎝ ⎠ ⎝ ⎝ ⎠⎠

2

I.Laktineh, IPNL 3


Some history

• Solution of Schrödinger equation with linear potential 1928 :

G. Breit, Phys Rev 32 (1928) 273

• First attempts of ultra cold neutron storage at JINR (Dubna(

Dubna)

in 1968 :

V.I. Luschikov et al., JETP Lett 9 (1969) 40

• 1976, , proposal to look for quantum energy levels using ultra

old neutrons :

V.I. Luschikov, Physics Today 42 (1977) 51;

V.I. Luschikov and A.I. Frank, JETP Lett 28 (1978) 559

• First observations of the quantum states in a gravitational

field at ILL/France in 1999 :

V.V.Nesvizhevsky

et al., Nature 415 (2002) 297;

Phys Rev D87 (2003) 102002

Nagoya, 2006

I.Laktineh, IPNL 4


Institut Laue Langevin, Grenoble/France

ILL

LPSC/IN2P3

ESRF

100 km from Lyon

Nagoya, 2006

I.Laktineh, IPNL 5


equirements

To observe quantum states in gravitational field

- neutral particle

- long lifetime ultracold neutron

- small mass (E


Experiment setup

Vh

=

few

m/s

1

10 9

3

5

x

6

7

8

11

Shutter

control

Amplifier

ADC

COMPUTER

Vv

=

few

mm/s

2

10 cm

4

Amplifier

DAC

1. Neutron guide

2. Anti-vibration table

3. Polished granite stone

4. Piezo translators

5. Vacuum chamber

6. Mirrors and absorber

7. Detector

8. Anti-magnetic shielding

9. Input collimator

10. Neutron shutter

11. Inclinometers

Nagoya, 2006

I.Laktineh, IPNL 7


Detector

∆X

15 mm

120 mm

Picture of developed detector with tracks

Fission

fragment

UCN

neutrons

Plastic

Supermirror coating

Uranium-235

Nagoya, 2006

~0.2 µm ~0.5 µm

I.Laktineh, IPNL 8


Neutrons in gravitational field

Academic exercise

E , n

peV

3,32

V( z)

=

mgz

2,46

1,41

0

14 24 32 z,

µ m

z

h

2gm

2

3

0

= = 5,87 µ m

2

E

qc

n

≈ 3 ⋅ g n−

Nagoya, 2006

⎛9m

⎞ ⎛ ⎛ 1⎞⎞

⎜ ⎟ ⎜ ⎟

8

⎜π

h

4


⎝ ⎠ ⎝ ⎝ ⎠⎠

2

I.Laktineh, IPNL 9


Wave function

1st quantum

state

2nd quantum

state

0 10 20 30 40 50

Z, micron

0 10 20 30 40 50

Z, micron

2 ( ) ψ n

z

3rd quantum

state

4th quantum

state

0 10 20 30 40 50

Z, micron

0 10 20 30 40 50

Z, micron

Nagoya, 2006

I.Laktineh, IPNL 10


Procedure

After the exposure to the UCN beam one has to

- take out the Uranium (U235) layer

- itch the CR39 to produce the tracks

-scan the CR39

The observation of the quantum states of neutrons in gravitational field

can then be obtained by “visualizing” the square wave function module

using the neutron impact density.

Many problems were to be addressed:

-The Z zero position should be determined for the whole CR39 plate

-The mechanics precision should be less than 1 µ

But Itching leads to the CR39 curvature as well as scratches…

Nagoya, 2006

I.Laktineh, IPNL 11


Etching of uranium coating

The etching may curve the detector in following manner:

For this reason reference lines were used to estimate the curvature

Nagoya, 2006

I.Laktineh, IPNL 12


First results

Nesvizhevsky et al.,

J. Phys. C40 (2005)

479

Results obtained

by semi automatic

scannig

Nagoya, 2006

I.Laktineh, IPNL 13


What the automatic scanning can

provide?

The semi-automatic scanning suffers from some

drawbacks

1) It lasts about two months for each plate leading to

uncertainties on the absolute position due to temperature

and mechanics

2) Human intervention introduces subjective decisions which

thus differ from one operator to another.

3) CR39 degradation with time if not properly protected

3)

Nagoya, 2006

I.Laktineh, IPNL 14


What the automatic scanning can

provide?

At the French Scanning station we adapted the ESS to

scan some of the exposed CR39.

• The tracks are limited to the surface with a maximum

penetration of 10 microns.

12-15

15 tomographic layers were used ⇒ 1h/plate.

• All the tracks were found except those of large angle

(tg

θ > 5)

• Scratches dues to itching process simulated fake tracks

“however automatic scanning can be controlled easily and

quickly by a manual scanning”

Nagoya, 2006

I.Laktineh, IPNL 15


What the automatic scanning can

provide?

In 2007-2008 2008 a new run with more statistics is expected

• CR39 is a good detector but its relatively bad surface

planarity and the scratches left by the Uranium itching

convince us to try to use emulsion. However emulsion

density is about twice the CR39 one ( 3 vs 1.3) which

means that ions will produce very short tracks

(< 5 microns) which are hard to work out.

• Diluted emulsion of 20-30 microns thickness can be of

great help. Indeed the tracks can be seen from the side

opposite to the U235 covered side limiting the scratches

effects

• In both cases tracking algorithms capable of finding

horizontal tracks are on preparation.

Nagoya, 2006

I.Laktineh, IPNL 16


Conclusion

• The automatic scanning development we engaged for

OPERA can be a wonderful tool for amazing and very

interesting application.

• Ultra cold neutrons is one of those topics that our scanning

system can perform with negligible systematics.

(quantum states, 5th force search, axions…)

• The emulsion can be a competitive and even better one

but we need help from our Japanese colleagues.

Nagoya, 2006

I.Laktineh, IPNL 17

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