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C ,

4-5 2008



Tao , () , () Jun Luo, Huazhong University of Science and Technology (China) , () Shanqing Yan, Huazhong University of Science and Technology (China)



Progress on experimental determination of G
1798, H. Cavendish: G=(6.67 ± 0.07)в10-11 m3kg-1s-2 First G value! Uncertainty ~ 10000 ppm

2007, CODATA value: G=(6.67428 ± 0.00067)в10-11 m3kg-1s-2 Uncertainty ~ 100 ppm 10 !

!


Principle of Cavendish type experiment


No 1

The torsion balances and time of swing method
2 =
D + G ( / J

)

J ( 2 )1 - ( 2 )2 G= ( / )1 - ( /

[

]

)

2

No 2


G CODATA .
Authors, year of publication Value of Gв10-11 1972 1979 1982 1986 1995 1996 1997 1998 1999 1999 2000 2001 2002 2003 2003 2006 2007 3kg-1s-2 6.6714 6.6745 6.6726 6.67259 6.7154 6.6729 6.6740 6.673 6.6699 6.6742 6.674215 6.67559 6.67407 6.6742 6.67387 6.67425 6.67428 STD в10-11 m3kg-1s ppm
-

[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17]

Facy and Ponticis Sagitov, Milyukov, et al. Luther and Towler, CODATA Michaelis, et al. Karagioz, Izmailov, Bagley and Luther, CODATA Jun Luo, et al., Fitzgerald and Armstrong Gundlach and Merkowich, Quinn, Speake et all. Schlamminger et all. CODATA Armstrong and Fitzgerald Schlamminger et all CODATA

0.0006 0.0008 0.0005 0.00085 0.0006 0.0005 0.0007 0.010 0.0007 0.0007 0.000092 0.00027 0.00022 0.0010 0.00027 0.00010 0.00067

90 120 75 128 90 75 105 1500 105 105 14 41 33 150 40 16 100


Determination of G in SAI MSU (1975-1978)
General view on experimental device

Adjustment of torsion pendulum support

Vacuum chamber Vacuum pumps

Attractive mass

Attractive mass

Torsion balance Device for linear measurements


Results on measurement of Gravitational constant in SAI MSU in 1975-1978
Set No Exp. No I 6.6739 6.6741 6.6746 II 6.6708 6.6746 6.6730 6.7612 6.6747 Gв 10-11m3kg-1s
-2

III 6.6686 6.6795 6.6800 6.6732 6.6755 6.6721 6.6749 6.6826 6.6719 6.6688 6.6779 6.6757 6.6715 6.6799 6.6774

IV

1 2 3 4 5 6 7 8 9 10 Average value

6.6742 ± 0.002

6.6729 ±0.0009

6.6753 ±0.0020

6.6752 ±0.0013

According to STUDENT criterion (t-criterion) all these four sets on the 0.95 confidence level are belong to one statistical ensemble with the average value of

G=(6.6745 ± 0.0008)в10

-11

m3kg-1s

-2


The new experiment on determination of the gravitation constant in collaboration between HUST (China) and SAI MSU (Russia)



The vacuum vessel and the optical lever system were located in a -metal shielding room in the cave laboratory. The daily temperature change in the room is less than 0.005oC.




The torsion balance is the system with five degrees of freedom

Co-ordinats 1 and 4 is swing oscillations in the plate ZX, Co-ordinats 2 and 5 is swing oscillations in the plate ZY. 3 is the torsion oscillations



.

No.

,

1 2 3 4 5 6 7 8

0.0002 1.0372 2.8562 3.8936 7.3401 10.20 11.2335 14.0899


Suppression of coupling modes
Magnetic damper
Cu plate Dia.50m, length 70mm tungsten fiber

Dia.25m, length 890mm tungsten fiber

By eddy current loss of Al plate, the swing mode is suppressed effectively



. 1.67610-3 . 2.186·10-4 ­ .
10 10 10 10 10
-4

f0=1.676 в10 Hz

-3

-5

Amplitude(rad)

-6

-7

-8

10

-4

10 F requenc y(Hz)

-3

10

-2

fa=2.186в10 Hz
-4

-4

f0=1 .676в10 Hz

-3

Amplitude(rad)

10

10

-6

. 2.186·10-4 .

10

-8

10

-4

10 10 F requency(Hz)

-3

-2

10

-1



4, .
No.
1 2 3 4 , 1.0372 4.9790 6.0162 10.9952



· 11-15 ppm.