State Scientific Center of the Russian Federation National Research Institute for Physical-Technical and Radio Engineering Measurements Progress in deep laser cooling of Strontium at VNIIFTRI S. Strelkin, A. Galyshev, O. Berdasov, A. Gribov, S. Slyusarev P.N. Lebedev Physical Institute of the Russian Academy of Science K. Khabarova, N. Kolachevsky
GLONASS accuracy has significantly improved over last five years GLONASS Accuracy 8 years ago GLONASS allowed one to choose the appropriate street from the list… 3 years ago one knew exactly what the street it was.
Frequency standard’s evolution
M. Takamoto et al., PRL 102, (2009) 1D optical lattice and magic wave lengths
“An optical lattice clock with accuracy and stability at the level”, B.J.Bloom etc., Nature, vol 506, 6 Feb Sr-87 optical lattice clock instability
Sr-87 optical lattice clock in Russia 2010 – Sr lattice clock project within GLONASS program has been started at VNIIFTRI 2011 – collaboration with P.N. Lebedev Physical Institute
Sr isotopes: 88 (81%), 87 (7%), 86 (10%), 84 (2%) Natural linewidth = 1 mHz (allowed by hyperfine coupling of 3 P 0 to 3 P 1 and 1 P nm Weak sensitivity to the magnetic field (J = 0 →J = 0 transition) Clock transition: 1 S 0 3 P 0 Sr electronic level diagram
3D scatch of the vacuum system
Vertical set method of the system
Optical scheme detection beam Silver mirror Zeeman slower beam MOT beams oven PMT Zeeman slower camera
Without repumpers With repumpers ~10 6 ~4x10 7 First stage cooling
x10 more atoms with repumpers Repumping effect on trapped atoms number
Number of atoms in the “blue” MOT N~4*10 7 Т ~ 3 мК (depends on the intensity) 1 cm Temperature and number of atoms in the 1 st MOT
Narrower transition 1 S 0 3 P 1 is well-suited to Doppler cooling nm, natural linewidth 7,5 kHz, Doppler limit 200 nK) Narrower transition 1 S 0 3 P 1 is well-suited to Doppler cooling nm, natural linewidth 7,5 kHz, Doppler limit 200 nK) Narrow line requires narrow laser spectrum and high frequency stability Second stage cooling
Toptica DL pro laser nm Narrowing of the red MOT cooling laser
The distance covered during transportation - 60 km ULE systems manufacturing and transportation
Laser stabilization
Linear drift ~300 mHz/s Beatnotes
ULE-1 spacer: ATF films Finesse ULE-2 spacer: Lebedev Physics Institute Finesse ULE-1 and ULE-2 Critical Temperatures
Beatnote spectral linewidth
Doppler width of 1 S P 1 mK ~ 2 MHz Second stage cooling features
FM of cooling radiation allows to deal with different velocity groups within Doppler profile Broadband second stage cooling
1 mm Broadband second stage cooling ~10 6
Retrapping efficiency: 8-10% Temperature in the end of broadband cooling: T~35 K Broadband second stage cooling
Retrapping efficiency High intensity in the first stage cooling leads to low retrapping efficiency BUT
Retrapping efficiency The number of atoms in the first MOT depends on the cooling light intensity
Atomic cloud in the end of the second stage cooling T=2 K N=10 5 Atomic cloud in the end of the second stage cooling T=2 K N=10 5 Single mode second stage f=100
g≈eg≈e 1D MOT standard configuration Atomic population in any ground state favors absorption of light from the appropriate direction for trapping. Red MOT Second stage cooling of 87 Sr
g << e Absorption of light from a given direction depends on m F, and some m F states are thus not suited to provide spatial confinement in a MOT The need for stirring and randomizing the population among m F levels Trapping +Stirring Second stage cooling of 87 Sr
Clock laser systems
Target instability 1* Finesse: Achievable laser linewidth: ~1 Hz Clock laser systems
First stage cooling of 88 Sr and 87 Sr Two ULE stabilized lasers for second stage cooling are assembled and characterized Second stage cooling of 88 Sr Two ULE stabilized laser systems for clock transition spectroscopy are assembled Outlook Loading cooled atoms in the optical lattice at 813 nm and at 390 nm OPTICAL LATTICE CLOCK Conclusions
Working group at VNIIFTRI
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