The Space Optical Clocks Project:Development of optical lattice clocks for future applications in space
S. Schiller1, A. Görlitz1, A. Nevsky1, S. Alighanbari1, S. Vasilyev1, C. Abou-Jaoudeh1, G. Mura1, T. Franzen1, U. Sterr2, S. Falke2, Ch.
Lisdat2, E. Rasel3, A. Kulosa3, S. Bize4, J. Lodewyck4, G. M. Tino5, N. Poli5, M. Schioppo5, K. Bongs6, Y. Singh6, P. Gill7, G. Barwood7, Y. Ovchinnikov7, J. Stuhler8, W. Kaenders8, C. Braxmaier9, R. Holzwarth10, A. Donati11, S. Lecomte12, D. Calonico13, F. Levi13,
K. Kemmerle14, M. Plattner14, C. Jentsch9, S. Schilt16, T. Kippenberg17 and members of the SOC2 teams
EFTF 2012
Mission on the ISSModular breadboard development
• Operate a Sr lattice optical clock with 10-17 inaccuracy on the
ISS (incl. frequency comb)
• Goal I: test Einstein‘s prediction of the time dilation in the
graviational field of the Earth and of the Sun with 10 times
higher accuracy than in the ACES mission
• Goal II: perform relativistic geodesy, i.e. local determination of
Key points
Clock laserOpticalClock
Frequency comb
Est. total mass 310 kgEst. total power 300 W
(ACES: 270 kg, 450 W)
Payload overview Principle of optical latticeclock
Laser developments
• Goal II: perform relativistic geodesy, i.e. local determination of
the gravity potential, at equivalent level of 1 cm height within
ca. 1 day measurement time
• Space clock is compared with a network of optical and
microwave ground clocks using high-performance microwave
and laser links
• ESA candidate mission within the ELIPS programme, since
2005
• Pre-phase A study completed (2011), clock development
currently funded by EC-FP7
• Natural follow-on of the ACES mission
• Launch after 2018
comb
MicrowaveFrequency
Comparison
Unit
Microwavelink
Opticaltelescopes
OpticalFrequency
comparison unit
Data acquisition unit
Data link
Large atom number→ potential highstability
Several lasers, all frequency stabilized:
Strontium: 461 nm, 689 nm, 813 nm, 707 nm, 679 nm, 698 nm (clock transition)
Ytterbium: 399 nm, 759 nm, 1388 nm, 578 nm (clock transition)
Transportable Sr 698 nm clock laser Interference-filter stabilized clock laser
Laser developments
Frequency stabilizationsystem for 3 lasers
Complete Sr laser system
1E-14
698 nm Laser
NIST spherical cavity [Leibrand 2011]
NIST 26 cm Yb cavity [Jiang 2011]
• Configuration rigidly fixes the position of the cavity up to acceleration of 50 g (FEM simulation)
• Measured ∆ν/ν = 3×10-11/g for vertical and 4.3 ×10-10/g and 11.6 ×10-10/g for horizontal accelerations
• setup 40 cm × 30 cm × 20 cm
• weight 6 kg
• ULE cavity (length 120 mm,
Laser specifications
Sr
The Sr breadboard clockBreadboard apparatus
main planning choices:1. compact breadboard
for frequency production2. all lights fiber delivered
Transportable Strontium Sourcemain requirements:1. compact design2. reliability
Sr breadboard aspects
repumper(497nm)
resonant
photomultiplier(possible)Chamber configuration
rods are screwed
Beam configuration• Atomic flux ~ 3 × 1011 atoms/s
• 1st stage MOT: ~ 6 × 107 trapped atoms at 1 mK
• 2nd stage MOT: ~ 7 × 106 trapped atoms at 1.8 µK
• Lattice: 2 x 105 trapped atoms
Lattice trapping and spectroscopy
462 nm, 813 nm, 707, 679 nm laser are so far integrated with Sr clock breadboard0.01 0.1 1 10 100
1E-16
1E-15
NIST 26 cm Yb cavity [Jiang 2011]
mod
σy(τ
)
τ (s)
• ULE cavity (length 120 mm, diameter 60 mm)
• fused silica mirrors with thermal compensations rings
• finesse of 460 000
• fractional frequency instability < 1 × 10-15 for 0.1 s < t < 300 s
Yb
100 mm triple ULE cavity(low and medium finesse)
2. all lights fiber delivered3. custom flange holding MOT coils
and oven with 2D cooling
2. reliability3. low power consumption
blue (461nm) andred (689) MOT
fromZeeman
slower
(497nm)
optical lattice (813nm)
clock-probe (698nm)
resonantprobe
custom flangeDN150CF
radiator tofix MOT coils
compensation coils
rods are screwed on the custom flange
MOT coil
50 Gauss/cmwith 1.6 A
power dissipation of
20 W for each coil
no water cooling
• Volume of physics package: 210 liter(excluding electronics and readboard plate)
• Mass: 120 kg
• Power: 110 W (Sr oven: 15 W, magnets: ~40 W; electronics: 20 W)
• Total volume 1200 liter
• Lattice: 2 x 105 trapped atoms
Dichroic telescope for MOT Spectroscopy of 88Sr, (preliminary)
Transportable Yb clock
optical breadboard 120 cm x 90 cmno water cooling
is neededDimensions: 22 cm x 36 cm
• Complete Yb system on transportable optical table (1 m x 2 m); clock laser separate
• compact vacuum system; optimized for optical access and implementation of optical lattice• all laser systems diode or fiber based:
- blue laser diodes for precooling MOT (@ 399 nm) - frequency doubling of a diode-amplified fiber laser
in a PPLN waveguide for 2nd stage cooling MOT (556 nm)
- amplified diode laser laser for optical lattice (759 nm)
• 759 nm interference-filter ECDL is underdevelopment
• Interference-filter ECDL at 399 nm is operational
• 20 mW 556 nm for 2nd stage cooling
Yb laser system (partially integrated)Yb trapping in optical lattice• Setup for 1D lattice (achieved)or 2D lattice (planned)
„Green“ laser
(556 nm)
Spectroscopy beam
• Frequency-stable 1389 nm repumper laser
• 1 Hz clock laser linewidth
Measurement of the black-body shift Demonstration of Sr 3D MOT loaded from a dispenser + 2D MOT sourceGoal: operate the tubes at 300 K and 400 K;
New design for a vibration-insensitiveYb cavity, 30 cm long
Lifetime in lattice
Transfer efficiency from2nd stage MOT to lattice
Lattice laser
(759 nm)
(556 nm)
Main
chamber
Atomics package developments
Permanent-magnet Zeeman
slower
2nd generation Sr clock
breadboard design
Optics schematic of transport and magic lattices. - Optical delay paths aremechanically translated to position the waist of the magic lattice and clocklaser beams in either of the BBR measurement tubes. Atoms loaded into thetransport lattice are shuttled into and out of BBR tubes by controlling (withAOMs 1 and 2) a travelling wave component of the standing wave.
Schematic of vacuum chamber with twoblackbody tubes. Right: blackbody tube with
external heater
Goal: operate the tubes at 300 K and 400 K;determine shift to equiv. Inaccuracy of 2 x 10-17
Loading of Yb MOTwithout Zeeman slower
With/without 2D MOT