Space Fundamental Physics Program Past, Present and · PDF fileMark C. Lee/NASA Headquarters...

Wednesday, October 13, Session 1b, Talk 2.

Space Fundamental Physics Program Past, Present and Future Mark C. Lee/NASA Headquarters NASA’s space fundamental physics program will be reviewed and commented in term of its past performance, present posture and future possibilities.



NRC Decadal Survey of Life and Physical Science Space Research

N. P. Bigelow

Recently there has been a significant effort by a committee formed by the National Research Council to

provide a decadal survey to NASA to guide its research program in the life and physical sciences in space.

I will describe the context of this study and review the interim recommendations.

Wednesday, October 13, Session 1c, Talk 1.

Gravitational Physics with Atom Interferometry

Mark Kasevich/Stanford University


The Space Atom Interferometer (SAI) project: status and perspectives

G. M. Tino for the SAI Team, Universita' di Firenze, LENS, INFN

The Space Atom Interferometer (SAI) project, aiming at operating a cold atom interferometer on the ISS

for tests of fundamental physics, is a pre-phase-A study funded by ESA (2007-10).

Subcomponents of an atom interferometer demonstrator with the added specification of

transportability and using techniques that are suitable for later space use, such as all-solid-state lasers,

low power consumption, and compact dimensions, have been developed and are being validated.

The talk will give an overview over the achieved results and outline future developments.


Quantum Gases in microgravity

Ernst M. Rasel/University of Hannover, Germany

The European project "Quantum Gases in Microgravity" investigates the potential of quantum matter

for fundamental experiments in microgravity. We will present the research targets for drop tower

experiments as well as the road map for exploiting this new technique for a quantum test of the

equivalence principle in space. The main contributions to the project are from the QUANTUS and ICE

consortia pursuing drop tower tests and parabolic flights.


Atom interferometer sensor development and applications in space

Nan Yu/Jet Propulsion Laboratory, California Institute of Technology

Cold atom-based matter-wave interferometers use freefall atomic particles as test masses for precision

inertial force measurements. This inertial measurement technique is particularly advantageous while

implemented in a microgravity platform in space, making it an attractive scheme for precise tests of

gravity and fundamental physics. JPL has been developing a transportable gravity gradiometer based on

the cold atom interferometer scheme with the aim to bring the technology to space applications. In this

talk, we will summarize the progress in the on-going development of transportable gravity gradiometer

sensors at JPL. We will discuss some of the space applications, from tests of fundamental physics to

potential planetary gravity mapping.


Atom interferometers in microgravity: recent progress and perspectives

V. Ménoret, R. Geiger, G. Stern, P. Cheinet, B. Battelier, N. Zahzam, F. Pereira Dos Santos, A. Bresson, A.

Landragin and P. Bouyer , CNRS - Institut d'Optique

Quantum inertial sensing relies on the capability of manipulating the coherent wave nature of matter.

Because of the large and well-known (quantized) mass of atoms, Atom Interferometers are extremely

sensitive and accurate devices to sense for inertial and gravitational effects. They offer a breakthrough

advance in accelerometry, gyroscopy and gravimetry, for applications to inertial guidance, geo-

prospecting , geophysics and metrology.

In addition, Atom Interferometers have established to be excellent candidates for new fundamental

tests of General Relativity : since an Atom Interferometer is essentially monitoring a quantum particle

moving in a gravitational field, it may penetrate the classically unknown region of the gravitational

potential. This might answer the question of whether the time of flight of a quantum particle in a

gravitational field might deviate systematically from that of a classical particle due to violation of the

Universality of Free Fall. AIs also open perspectives for further tests such as the detection of

gravitational waves. These fundamental tests will benefit from the long interrogation times accessible

on microgravity platforms or in space.

We will report on the first demonstration of a quantum inertial sensor in an aircraft and in microgravity.

We have operated a 87Rb matter wave interferometer sensitive to acceleration in the Novespace A300-

0g aircraft taking off from Bordeaux airport, France. The plane carries out ballistic flights during which

22 seconds free-fall (0g) parabolas are alternated between pull-on and pull-down hypergravity (2g)

phases, and followed by one minute of standard (1g) gravity flight. The Atom Interferometer measures

the local acceleration of the aircraft with respect to the inertial frame attached to the interrogated

atoms which are free-falling. In this sense, the AI can be used to monitor the aircraft acceleration. We

have investigated differential Atom Interferometer configurations to illustrate the vibration noise

rejection expected in a two-species Atom Interferometer. These achievements constitute a major step

towards an airborne test of the UFF with quantum objects at the 10-11 level, and a possible space-based

test below 10-15.

Wednesday, October 13, Session 1d, Talk 1.

Optical clock with collisional shift at 10-17

Jun Ye/JILA, National Institute of Standards and Technology and University of Colorado, Department of

Physics, University of Colorado, Boulder, Colorado 80309-0440 ,[email protected]

Optical clocks based on atoms confined in optical lattices provide a unique opportunity for precise study

and measurement of quantum many-body systems. The state-of-the-art optical lattice clock has reached

an overall fractional frequency uncertainty of 1×10-16 [1]. A dominant contribution arises from atomic

collision-induced frequency shifts, which occur when spin-polarized fermionic Sr atoms are subject to

slightly inhomogeneous optical excitations during the clock operation [2]. Several theories have been

proposed to describe the frequency shift mechanism [3–5]. Here we present a seemingly paradoxical

solution to the collision shift problem: we dramatically increase the atomic interactions and observe an

increasingly suppressed collisional shift. The atomic interaction is enhanced by strongly confining the

atoms in one-dimensional tube-shaped optical traps. The large atomic interaction strength creates an

effective energy gap in the system such that inhomogeneous excitations can no longer drive fermions

into a pseudo-spin antisymmetric state, and hence their collisions and the corresponding frequency

shifts are suppressed [6]. This mechanism is akin to the continuous Quantum Zeno effect where an

increasingly large dissipation rate helps freeze a system in its initial state. We demonstrate the

effectiveness of this approach by reducing the density-related frequency shift to 3×10-17 ± 1×10-17,

achieving an order of magnitude reduction from the previous record [2]. Control of atomic interactions

at the level of 1×10-17 is a testimony to our understanding of a quantum many-body system and it

removes an important obstacle for building an optical atomic clock based on such systems with the

highest possible accuracy. When the atom number increases, both the clock precision and accuracy are

improved at the same time.

[1] A. D. Ludlow et al., Science 319, 1805 (2008).

[2] G. K. Campbell et al., Science 324, 360 (2009).

[3] K. Gibble, Phys. Rev. Lett. 103, 113202 (2009).

[4] A. M. Rey, A. V. Gorshkov, C. Rubbo, Phys. Rev. Lett. 103, 260402 (2009).

[5] Z. H. Yu and C. J. Pethick, Phys. Rev. Lett. 104, 010801 (2010).

[6] M. D. Swallows et al., arXiv:1007.0059v2, 2010.


The Space Optical Clocks Project

P. Lemonde, S. Schiller, G. M. Tino, U. Sterr, Ch. Lisdat, A. Görlitz, N. Poli, A. Nevsky, C. Salomon/ SYRTE

The Space Optical Clocks project aims at operating lattice clocks on the ISS for tests of fundamental

physics and for providing high-accuracy comparisons of future terrestrial optical clocks. A pre-phase-A

study (2007-10), funded partially by ESA and DLR, included the implementation of several optical lattice

clock systems using Strontium and Ytterbium as atomic species and their characterization.

Subcomponents of clock demonstrators with the added specification of transportability and using

techniques suitable for later space use, such as all-solid-state lasers, low power consumption, and

compact dimensions, have been developed and have been validated. This included demonstration of

laser-cooling and magneto-optical trapping of Sr atoms in a compact breadboard apparatus and

demonstration of a transportable clock laser with 1 Hz linewidth. With two laboratory Sr lattice clock

systems a number of fundamental results were obtained, such as observing optical atomic resonances

with linewidths as low as 3 Hz, non-destructive detection of atom excitation, determination of

decoherence effects and reaching a frequency instability below 10-16.


Update on the NIST Single-Atom Optical Clocks

James C. Bergquist/ NIST, Boulder, USA

Single-trapped-ion frequency standards based on a 282 nm transition in 199Hg+ and on a 267 nm

transition in 27Al+ have been developed at NIST over the past several years. Their frequencies are

measured relative to each other and to the NIST primary frequency standard, the NIST-F1 cesium

fountain, by means of a self-referenced femtosecond laser frequency comb. Both ion standards have

demonstrated instabilities and inaccuracies of less than 3 ×10-17. I will report the most recent results of

these two standards as well as future plans toward highly stable, robust, and portable spherical cavities.


Comparison of Remote Optical Atomic Clocks

Fritz Riehle/Physikalisch-Technische Bundesanstalt (PTB)

Optical atomic clocks on ground now outperform the best caesium atomic clocks that realize the unit of

time in the International System of Units (SI) and they represent the most accurate measuring devices

for applications in technology and basic science. The currently used methods to compare remote clocks

e.g. by Two-Way Satellite Time and Frequency Transfer are no longer capable to compare optical clocks

with optimal accuracy and stability.

The status and prospects of optical clocks on ground and in space will be reviewed. It will be

demonstrated how, in contrast to microwave transmission, long-haul optical fiber links can be used to

perform phase-coherent carrier frequency comparisons of optical clocks without limitations of the

achieved clock stability and accuracy. Intercontinental clock comparisons, however, will furthermore

need free-space optical carrier links in a phase-coherent way. The prospects for space optical clocks and

means for phase coherent optical ground-to-space links will be outlined and different methods for their

implementation will be discussed.


Improving the Accuracy, Stability, and Portability of Neutral Atom Optical Clocks

A. D. Ludlow, N. D. Lemke, J. A. Sherman, Y. Y. Jiang, R. W. Fox, T. Fortier, S. A. Diddams, C. W.

Oates/NIST

We discuss recent efforts to improve the performance of the NIST optical clocks based on neutral Yb and

Ca. We describe recent measurements made with 171Yb confined in 1-D and 2-D optical lattices,

including characterization of cold collision effects. We show recent improvements to our interrogation

laser and the benefits afforded to the Yb clock stability. We also discuss plans to characterize blackbody

induced limitations to the Yb clock accuracy. Finally, we describe the Ca optical clock. This system is

designed with stability, simplicity, and eventual portability in mind and we discuss recent efforts to

improve its robustness and reduce its size for possible field application.


NPL Optical Atomic Clocks and Space Hugh A. Klein/NPL The Quantum Frequency Standards group* at the U.K. National Physical Laboratory (NPL) is developing optical clocks based on both trapped ions and atoms [1]. Centred on an anticipated redefinition of the second, our optical frequency standards and femtosecond combs work also targets space and other applications, as well as tests of the stability of the fundamental constants [2]. Over the last ten years, together with other European partners, we have been involved in several investigations for ESA on space-based applications of optical clocks. Two important studies were led by NPL on: Optical Synthesisers for Space, and Optical Clocks for Deep Space Ground Stations. More recently NPL prepared a technology development programme for ESA which mapped out a route to achieving the goal of deploying an optical atomic clock in space by 2020. * Patrick Gill, Geoffrey Barwood, Liz Bridge, Witold Chalupczak, Anne Curtis, Christopher Edwards, Rachel Godun, Ian Hill, Guilong Huang, Steven King, Hugh Klein, Stephen Lea, Helen Margolis, Giuseppe Marra, Yuri Ovchinnikov, Ben Parker, Krzysztof Szymaniec, Barney Walton, Stephen Webster and Veronika Tsatourian. 1. http://www.npl.co.uk/science-technology/time-frequency/optical-frequency-standards-and-metrology/ 2. Related research at NPL includes frequency transfer by fibre networks, primary frequency standards (caesium fountains), an ion-trap based entangled quantum absorbers project and measurement of the Rydberg constant. 3. Patrick Gill, Helen Margolis, Anne Curtis, Hugh Klein, Stephen Lea, Stephen Webster and Peter Whibberley, “Optical Atomic Clocks for Space” ESTEC Contract No. 21641/08/NL/PA (November 2008).

Thursday, October 14, Session 2a, Talk 2.

ISS Kennedy-Thorndike Experiment

Joel Nissen /JPL, John Lipa/Stanford University

Recently improvements in ground based Michelson-Morley experiments have rivaled the results

attainable on the ISS. Advancements in ground based Kennedy-Thorndike (KT) experiments, however,

have not been as dramatic because the angle independent KT experiment cannot take advantage of

turntables to optimize the measurement. A very attractive package for operation on the ISS would be to

combine a highly a stable room temperature Ultra Low Expansion (ULE) optical cavity with an Iodine

stabilized laser. For the KT experiment the signal is enhanced by the orbital velocity. The ratio of the

orbital velocity with the ground velocity, results in an 18 times improvement in sensitivity. On orbit, the

measurement is repeated 16 times a day leading to further enhancement of a factor of 4. The 90 minute

orbital period is also a better match for the optimal performance of the cavity than the diurnal cycle

available on earth. In addition to providing advancement over ground based measurements, an ISS

based optical cavity experiment could be teamed with the ACES clock using a frequency comb giving rise

to additional Lorentz invariance tests.


Space as a laboratory to test the foundations of General Relativity: the Satellite Test of the

Equivalence Principle.

John Mester, Suwen Wang, Paul Worden, Francis Everitt / Stanford University

STEP (the Satellite Test of the Equivalence Principle) will advance experimental limits on violations of

Einstein's equivalence principle (EP) from their present sensitivity of 2 parts in 1013 to 1 part in 1018

through multiple comparison of the motions of four pairs of test masses of different compositions in an

earth-orbiting drag-free satellite. Dimensional arguments suggest that violations, if they exist, should be

found in this range, and they are also predicted by many of the leading attempts at unified theories of

fundamental interactions (e.g. string theory), as well as cosmological theories involving dynamical dark

energy. Discovery of a violation would constitute the discovery of a new force of nature and provide us

with a critical signpost toward unification. A null result would be just as profound, because it would

close off any possibility of a natural-strength coupling between standard-model fields and the new light

degrees of freedom that nearly all such theories generically predict (e.g., dilatons, moduli,

quintessence). STEP should thus be seen as the intermediate-scale component of an integrated strategy

for fundamental physics experiments that already includes particle accelerators (at the smallest scales)

and supernova probes (at the largest).


Test of the Equivalence Principle on ISS

Ho Jung Paik, Krishna Y. Venkateswara, and M. Vol Moody/ Department of Physics, University of

Maryland, College Park

The Equivalence Principle (EP) is a cornerstone of General Relativity. Nonetheless, many models of the

quantum theory of gravity prefer a scalar-tensor theory and suggest a violation of this principle. Testing

EP to the highest possible precision is important because the failure to quantize gravity may be partly

due to incompleteness of General Relativity. We propose to test EP to one part in 1017 on ISS by using

superconducting accelerometers of a unique design. This will improve the limit of EP by two orders of

magnitude beyond the Microscope mission.

To reach this sensitivity, superconducting accelerometer technology will be combined with advantages

of the low-g environment of space. The experiment will be cooled to < 2 K, which permits

superconducting magnetic levitation, allowing very soft, low-loss suspension of the test masses. Unlike

STEP, which utilizes test masses of cylindrical geometry, this experiment utilizes outer test masses of

near spherical-shell geometry. The spherical shell reduces higher multipole moments of the test masses

and permits a simpler levitation and alignment scheme along a common circular tube. The signals are

detected by superconducting differential accelerometers formed by the inner and outer test masses.

Unlike the EP tests on the ground, which utilizes a mere 10-3 of the Earth’s gravity as signal, space

experiments can use the full gravity of the Earth as signal by rotating the experiment with respect to the

Earth. Vibration and jitter are main challenges of the ISS experiment. The proposed single-tube

levitation/alignment scheme minimizes the effects of the platform noise by rejecting common-mode

accelerations to better than one part in 108.

The superconducting accelerometer technology has matured through the NASA superconducting

gravity gradiometer project in the 1980’s and 1990’s, and the NSF funded short-range test of the

inverse-square law developed over the last decade. With the GP-B heritage for flight SQUID electronics,

the main remaining task is the demonstration of the ability to manufacture the test masses with

required tolerances. With adequate funding, the flight experiment could be prepared in five years.

Thursday, October 14, Session 2b, Talk 1.

The Potential Use of the Low Temperature Microgravity Physics Facility for Fundamental

Physics Studies on the ISS

Talso Chui / JPL

The Low Temperature Microgravity Physics Facility (LTMPF) is a liquid helium cooled facility equipped

with a number of superconducting quantum interference devices (SQUIDs) and other sensitive

thermometers. It is intended to enhance the scientific capability of ISS by enabling very sensitive

experiments that can only be done in space and at low temperatures. I will review of a wide range of

condensed matter physics and gravitational physics experiments that will be enabled by LTMPF, and

discuss the reason why both space and low temperature environment are required for them. The

current status of LTMPF will also be reviewed.


The DX/CQ Experiments

Dr. Richard A. M. Lee (JPL), Prof. Robert V. Duncan (University of Missouri) and Prof. David L. Goodstein

(Caltech)

The DX Experiment (Critical Dynamics in Microgravity) will use the superfluid transition, in pure He-4, to

study how disequilibrium effects a critical point phase transition. It will explore how a heat flux modifies

the Lambda Transition by creating a nonlinear region where the helium is neither fully superfluid nor

fully normal fluid. The CQ experiment (Enhanced Heat Capacity of Superfluid Helium in a Heat Flux) will

compliment and extend DX by exploring the effect of a heat flux on the superfluid side of the transition,

through measurement of its heat capacity. Both experiments will test predictions of the Dynamic

Renormalization Group theory. They will be done in conjunction, using the same hardware and

electronics, and on the same mission.

For DX, the spatial extent of the nonlinear region is heavily attenuated by Earth’s gravity, to ~ 100

microns, severely limiting its measurement - in microgravity no such limitation exists and the nonlinear

region can be almost as large as the experimental cell, 10 mm. For CQ, the heat capacity is profoundly

rounded due to Earth's gravity. This can be mitigated somewhat by having a shallow cell, but the best

ground-based data is still strongly affected in both its range and precision - again, in space, no such

restrictions apply.

The DX/CQ Experiments were originally scheduled for operation on the International Space Station (ISS)

in the Low Temperature Microgravity Physics Facility (LTMPF) – a reusable, unmanned, microgravity

physics laboratory that was designed to dock onto the ISS and operate autonomously. LTMPF is able to

accommodate two low temperature experiments at the same time, one of which would be DX/CQ. On-

orbit DX/CQ would require a minimum of one month operation time (with an anticipated maximum of

five months) before LTMPF was returned to Earth and a new suite of experiments installed. Both LTMPF

and DX/CQ passed their Critical Design Reviews before the program was cancelled in 2004 due to

NASA’s new Moon and Mars initiative. Before cancellation LTMPF had entered into its fabrication phase

and was approximately 70% complete. DX/CQ had been through several successive flight prototype

developments, and almost all of its flight hardware drawings were completed and released (note, some

changes to the experimental design are anticipated). The flight software and embedded processing

design had been initiated and was about 15% complete. The remaining flight hardware/software must

be completed and assembled, and then undergo complete flight testing. Approximate time to flight for

DX/CQ: 3 to 6 years.

Potential US collaborators include NIST to develop a flight, single channel or multiplexing, SQUID system

for LTMPF - this system is required to read the precision thermometry for DX/CQ. International

collaborators may include JAXA who currently operate the Japanese Exposed Facility on the ISS - the

original proposed docking site for LTMPF.

It is recommended that the DX/CQ and LTMPF flight projects be recommenced in order to fulfill the

substantial intellectual and financial investment that has been made by NASA and JPL.


Superfluid 4He critical phenomena in space, and in the SOC state on Earth

R.V. Duncan / University of Missouri

Measurements of the heat capacity and thermal conductivity of 4He have been made on Earth orbit in

the LPE experiment, and on earth on the self-organized criticality (SOC) state. The SOC state

measurements avoid 'rounding' that is induced by the hydrostatic pressure gradient across the sample,

as in space-based measurements, but departures occur within 50 nK of the critical temperature in the

heat capacity due to limits imposed by gravity on the divergence in the correlation length. The thermal

conductivity divergence permits the system to self organize. Strangely the heat capacity that is

measured on the SOC state is observed to diverge at the static critical point 'T-lambda', but the thermal

conductivity diverges at a lower temperature Tc(Q). The ramifications of these results will be discussed,

since they are counter-intuitive. The speed v of a new temperature-entropy wave that was predicted by

Weichman and Miller (WM) has now been measured over a wide range of heat flux Q, and this observed

variation of V(Q) agrees well with theory. These published measurements have been co-authored with

Andrew Chatto, R.A.M. Lee, and David Goodstein. This work has been sponsored by NASA and

conducted at Caltech and at the University of New Mexico.


Advances in fundamental physics through a partnership between theory and experiment

Peter B. Weichman, BAE Systems – AIT

Rather than focusing on a single narrow topic, I would like to present a broad argument for the benefit

of theoretical studies in support of microgravity experiments. Advances in fundamental physics,

especially in the high-resolution regimes accessible in microgravity, typically require a unique

partnership between experiment and theory.

Solutions to interesting problems will always have surprises along the way, especially in experiments

seeking to explore entirely new phenomena. However, interpretation of uniquely high resolution

microgravity data may also require sophisticated theory even if the phenomenon is well understood---

trust in important numbers (e.g., critical exponents) requires a corresponding improvement in

theoretical resolution. Theoretical considerations may then enter at all stages of the multi-year critical

path of a flight experiment, from research concept, to flight definition requirements, to analysis of the

flight data.

I will discuss a few examples related past programs, such as issues in near-critical superfluids studied in

DYNAMX and CQ, and some examples from possible future experiments, such as dynamics of

microdroplets in free fall and their relation to cloud physics and rain formation. The latter is also

relevant to microgravity manipulation of fluids in spacecraft for practical applications.

Thursday, October 14, Session 2c, Talk 1.

The ACES Mission

L. Cacciapuoti/ESA-The Netherlands, O. Minster/ESA-The Netherlands, C. Salomon/ENS-France

Atomic Clock Ensemble in Space (ACES) is a mission of the European Space Agency (ESA) testing

fundamental laws of physics with high-performance atomic clocks. Operated on-board the International

Space Station, the ACES payload will distribute a clock signal with fractional frequency instability and

inaccuracy of 1×10-16. This frequency reference is obtained from the combination of the medium-term

stability of an active hydrogen maser (SHM) with the long-term stability and accuracy of a primary

standard based on samples of laser cooled Cs atoms (PHARAO). The ACES clocks are entangled by two

servo-loops, the first stabilizing the PHARAO local oscillator on SHM, the second controlling the long-

term instabilities of SHM using the error signal generated by the PHARAO Cs resonator. A link in the

microwave domain (MWL) and an optical link (ELT) will make the ACES clock signal available to atomic

clocks on ground, connecting them in a worldwide network. Space-to-ground and ground-to-ground

comparisons of atomic frequency standards will be used to test Einstein’s theory of general relativity

including a precision measurement of the gravitational red-shift, a search for time variations of

fundamental constants, and tests of the Standard Model Extension. Applications in geodesy, optical time

transfer, and ranging will also be supported.

ACES main instrument and subsystems have now reached an advanced status of development,

demonstrated by the completion and the successful test of their engineering models. In particular, a

dedicated test campaign has recently verified the performance of the ACES system, where PHARAO and

SHM, locked together via the ACES servo loops, are operated as a unique oscillator to generate the ACES

frequency reference. The test campaign conducted at CNES premises in Toulouse between July and

November 2009 has concluded the engineering models phase, releasing the manufacturing of the ACES

flight models. The first prototype of the ACES MWL ground terminal is being assembled, ready for

testing. The ACES ground segment architecture has been defined. Based on an extension of the standard

Columbus USOC (User Support and Operations Center) located in CADMOS–Toulouse, the ACES USOC

will remotely control the network of MWL ground terminals, and provide the necessary interfaces with

the Columbus Control Center and the ACES users’ community.

The current development status of the ACES mission elements will be presented. An overview of future

planning will be given and possible areas of collaboration on the ACES exploitation programme

discussed.


ACES Scientific Objectives and Perspectives

C. Salomon (1) and L. Cacciapuoti (2)/ (1) Ecole Normale Supérieure, 24 rue Lhomond, Paris, France

(2) ESA-ESTEC, Noordwijk ZH, 2200 AG, The Netherlands

We will recall the Scientific Objectives of the Space mission ACES and discuss possible collaborations

with USA institutes. Thanks to a high performance time transfer system (microwave link: MWL),

intercontinental clock comparisons with a new level of precision will be achieved. This will

allow fundamental physics tests such as a search for a time dependence of fundamental physics

constants and a redshift test with 2 parts per million accuracy. With the recent advance on optical

clocks, new applications in geodesy and Earth observation will become possible.


JPL Participation in ESA ACES Worldwide Clock Comparison Campaign

Nan Yu, Eric Burt, John Prestage, and Robert Tjoelker/Jet Propulsion Laboratory

ACES is an ESA mission in Fundamental Physics using advanced atomic clocks in the microgravity

environment of the ISS. Some of the key objectives of ACES will be achieved by global time transfer and

clock comparisons with the most advanced clocks at multiple worldwide sites. There is an opportunity

for investigators from the leading clock and metrology labs to participate in the clock comparison

campaign, enhancing the overall science objective of ACES and at the same time demonstrating and

providing science benefit from advanced clock technologies. JPL has developed the unique trapped ion

mercury clock technology that enables exceptional high stability performances. LITS clocks based on the

trapped ion mercury clock technology are the only advanced clocks currently capable of continuous

long-term operation and have demonstrated extremely high long-term frequency stability with a single

frequency standard comparable to that of the Universal Time Coordinated time scale. Spaceflight

worthy versions of the similar technology are also being developed for use in the next generation of GPS

satellites clocks and Deep Space Science missions. NASA has recently funded JPL for a collaboration

effort with ACES mission by participating in the ACES global clock campaign using the JPL LITS clocks

together with an ensemble of other high performance frequency references at JPL. In this talk we will

present a brief description of the LITS performance capabilities and discuss the collaboration objective

and the planned activities.


High Stability Clocks in Space

Kurt Gibble/ Penn State

Microgravity offers performance advantages for high stability atomic clocks and the opportunity for

tests of fundamental physics. Just as in the case of microwave clocks, the design of optical frequency

clocks must also be different for microgravity from that for earth. I will describe some possible designs

to achieve high short and long term stability and accuracy.


JPL Ultra-Stable Trapped Ion Clock Performance and Space Applications

E.A. Burt, J.D. Prestage, and R.L. Tjoelker/Jet Propulsion Laboratory, California Institute of Technology,

Pasadena, CA 91109-8099

JPL’s ultra-stable continuously running trapped ion atomic clock, known as LITS-9, has demonstrated

long-term fractional frequency deviations of < 3×10-17/day over a 9-month period [1] making it among

the most stable continuously running clocks in the world. With long-term stability approaching UTC, and

its unique geographical location, LITS-9 may be used as part of the campaign to characterize the ACES

clocks and the ACES Microwave Link (MWL). In addition, while an upper bound on long-term LITS-9

stability has been determined, a precise measurement of its systematic floor has been limited by

existing time and frequency transfer methods. With its improved performance, the MWL should make it

possible to unambiguously observe this floor in comparisons to the ACES clocks as well as other ACES

base station clocks.

In this paper we will describe the comparisons between LITS-9 and various international frequency

standards that have been used to derive the upper bound on LITS-9 stability, and future plans for this

standard, as well as newer versions of the clock currently under development for both space and ground

applications.

*1+ E.A. Burt, W. A. Diener, and R.L. Tjoelker, “A Compensated Multi-pole Linear Ion Trap Mercury

Frequency Standard for Ultra-Stable Timekeeping,” IEEE Trans. UFFC 55, 2586 (2008).


Miniaturizing Ion Clocks for Space Applications

John D. Prestage, Sang Chung, Robert Thompson, Nan Yu/Jet Propulsion Lab/California Institute of

Technology, Pasadena, CA/USA, [email protected]

Abstract: Ultra-stable Ion clock technologies can be miniaturized with little loss of short and long-term

stabilities, in part because atomic line Q is not diminished as physics package size is made smaller. We

have demonstrated short-term stability ~1-2x10-13 at 1 second, averaging to 10-15 at 1 day, showing that

H-maser quality stabilities can be produced in a small clock package. We have completed an ion clock

physics package designed to withstand vibration of launch and are currently building a ~ 1 kg model for

test. The ion traps are contained in a sealed vacuum using only getter pump elements to hold ultra-high

vacuum for many years. This operational architecture does not consume Hg vapor and requires no oven

to generate Hg, greatly simplifying the instrument.

A prototype device shows short term stability 9x10-14 at 1 second averaging time after being operated in

a sealed vacuum enclosure for more than 3 years. No mercury oven is required to regenerate vapor to

load ions and hold time for ions inside the rf trap is ~3000 hours, far longer than turbo-pumped systems.

We will review the current state of physics package development, currently at ~1-liter without the

electronic modules used to operate the instrument. The physics package consists of ion traps, electron

source, vacuum tube, optical system, microwave and optical windows and magnetic C-field coils

together with 2-3 layers of magnetic shielding.

Thursday, October 14, Session 2d, Talk 1.

Gravitational Redshift, Equivalence Principle, and Matter Waves

Michael Hohensee and Holger Mueller/ UC Berkeley

The gravitational redshift was the first consequence of General Relativity described by Einstein, and its

measurement continues to be fundamental to our confidence in the theory. Clock comparison tests

have reached an accuracy of 7x10-5, while matter wave tests, in which redshift anomalies modify

material particles' Compton frequencies, have reached 7×10-9. The Standard Model Extension (SME) can

be developed into a comprehensive model for violations of the Einstein Equivalence Principle which

maintains conservation laws of the Standard Model. Here, we use the SME to show that modern redshift

experiments can bound anomalies that are presently poorly constrained and outside the reach of tests

of the universality of free fall. We identify the similarities and differences between matter wave and

clock comparison tests. Moreover, we propose the Geodesic Explorer, an atom interferometer

performing a redshift measurement in a sounding rocket, the Space Station, or a freely flying satellite.

Operation in microgravity converts the redshift measurement into a null measurement while the

velocity along the gravitational potential gradient v provides a signal enhancement by v2/c2, which can

be one million times greater than in the lab. Such a test would provide bounds on post-post Newtonian

mailto:[email protected]

effects of General Relativity that could be 1 billion times better than current laboratory bounds, and

10,000 times better than current astrophysics bounds.


Diode laser based laser systems for precision applications in space

A. Wicht(1,2), A. Peters(1,2), K. Paschke(1), G. Erbert(1), G. Tränkle(1) / (1)Ferdinand-Braun-Institute,

Gustav-Kirchhoffstr. 4 12489 Berlin, Germany, (2) Humboldt University Institut fuer Physik

Hausvogteiplatz 5-7 10117 Berlin, Germany

Optical Metrology provides today’s most precise measurements, specifically in the field of fundamental

physics. Meanwhile it is more and more widely accepted that some of the most precise applications like

optical clocks or matter wave interferometry have to go to space to deliver the performance they can

ultimately provide.

These applications require ultra-frequency stable lasers at various wavelengths ranging from near IR to

the deep blue side of the optical spectrum. As these lasers have to deliver their performance under the

specific conditions of space environment, they have to be compact, energy efficient, robust, and

reliable. I will show that diode laser based laser systems are an ideal solution to this challenge.

I will give an overview about the current activities at the Ferdinand-Braun-Institute to develop diode

laser based narrow linewidth (kHz-level before active frequency stabilization) laser systems for optical

metrology with an optical power ranging from a few 10 mW to well beyond 1 W. The development

includes extended cavity diode lasers, DFB- and DBR-lasers, as well as master-oscillator-power amplifier

configurations or frequency doubled laser systems. The focus lies on the hybrid micro-integration of

mechanics, optics, laser chips and electronics into a single module that eventually can be operated in

space.

The presentation gives an overview of the current status of our work, it outlines potential areas of

application in the field of fundamental physics and optical metrology, and highlights open questions, i.e.

the need for further technology development.


Electron Electric Dipole Moment Experiments using Laser-Cooled Atoms

Harvey Gould /Lawrence Berkeley National Laboratory

Supersymmetry predicts an electron electric dipole moment (EDM) that exceeds the experimental

bound by more than two orders of magnitude for supersymmetric CP-violating phases of order unity and

mass scale of order 100 GeV[1,2]. Thus lowering the experimental bound by several orders of magnitude

without observing an EDM would weaken attractive features of supersymmetry. Observing an electron

EDM would demonstrate a nonstandard-model source of CP violation and point to undiscovered TeV

scale particles.

Laboratory electron EDM experiments search for a difference in energy between an unpaired electron

aligned and anti-aligned with an external electric field. High atomic number paramagnetic atoms provide

test systems of zero net charge and, due to relativistic effects, can enhance the sensitivity to an electron

EDM. The apparatus for these experiments resembles an atomic clock with an added electric field. A

laser-cooled-atom electron EDM experiment could benefit from the extended transit time available in

microgravity in the same way as a laser-cooled microwave atomic clock.

Among the challenges of a microgravity EDM experiment, the force on the polarizable atoms from

inhomogeneities in the electric field is perhaps the most interesting: its understanding and management

requires the tools of accelerator physics.

For experiments that can be ground based, microgravity is appropriate when the experiments approach

their full ground based potential. That is not yet the case for laser-cooled atom electron EDM

experiments for which only a proof-of-principle experiment has been published[3]. There are technical

issues unique to microgravity and ISS environment such as beam transport and magnetic shielding that

are potentially shared by other laser-cooled atom experiments. But for laser-cooled electron EDM

experiments, the critical path is completion of a ground based experiment. In the meanwhile, ground

based technical issues are being addressed. Details may be found at www.eEDM.info.

[1] S. Khalil, Int. J. Mod. Phy. A18, 1697 (2003).

[2] K. A. Olive et. al., Phys. Rev. D72, 075001 (2005).

[3] J. M. Amini, C. T. Munger Jr., and H. Gould, Phys. Rev. A75, 063416 (2007).


Atom Circuits: Persistent current in a toroidal condensate

Gretchen Campbell JQI/NIST

Interferometry with ultracold atoms has shown great promise for making ultraprecise measurements.

However, traditionally they operate in spite of atom-atom interactions, which typically lead to

decoherence. In contrast, the non-linearity of electronic supercounducting, quantum interference

devices (SQUIDs) allows for highly sensitive detection of magnetic fields. By taking advantage of the

superfluidity of an interacting gas, we hope to demonstrate an atom-analogue to a SQUID. Our atom-

SQUID will have similarly enhanced sensitivity to rotation. Here we present our first steps towards this

goal. We have recently created a long-lived persistent current in a toroidal condensate, and have

studied the stability of the flow in the presence of a repulsive barrier.

http://www.eedm.info/


A Quantum Gas Pathfinder Experiment for the ISS

Rob Thompson

Microgravity based studies of superfluid phase transitions such as the shuttle-based LPE and CHEX

missions led to significant new insights into these phenomena. The advent of laser and evaporative

cooling have allowed dilute atomic gases to be cooled to the point in which a rich variety of superfluid

phenomena have been observed. Such experiments offer important differences and advantages over

the previous liquid helium-based studies, including the ability to tune the interactions between atoms

over a wide range, to trap them in a wide variety of potentials and the ability to precisely observe

momentum distributions. Furthermore the lack of cryogen and the use of miniature magnetic traps

make these experiments eminently suitable for space-based studies. Microgravity offers several distinct

advantages for studies of superfluidity, including the ability to significantly reduce density

inhomongeneities and density stratification and to produce even lower temperatures. This advantages

may aid the observation of several predicted but hitherto unobserved phase transitions, as well as allow

more precise measurements of a variety of superfluid phenomena. I will discuss a simple concept for a

relatively inexpensive ISS degenerate quantum gas experiment which could serve as a pathfinder for

other space-based laser-cooling experiments.

Friday, October 15, Session 3a, Talk 2.

Studies of critical water and salt – critical water mixtures under thermal gradients utilizing

the DECLIC facility on-board ISS

Michael C. Hicks and Uday G. Hegde (Nasa Glenn Research Center, Cleveland, OH, USA), Yves Garrabos

and Carole Lecoutre (ICMCB-CNRS, Université de Bordeaux, Pessac, France), Daniel Beysens(CEA,

Grenoble, France and ESPCI-ParisTech, Paris, France)

Recently, the DECLIC (Dispositif pour l'Etude de la Croissance et des Liquides Critiques) facility supported

by CNES/NASA was successfully integrated into the International Space Station (ISS). Multiple science

inserts are developed for the DECLIC facility and are currently on-board ISS. Two inserts are designed to

study sample fluids near their critical point in a very stable thermal environment by using optical

interferometry, light scattering, microscopy, and grid shadowscopy. In particular, the DECLIC-HTI insert

was dedicated to study thermodynamic properties of pure water near its liquid-gas critical point and to

investigate the related phenomena, as piston effect and phase separation in weightless condition. We

present the preliminary results of the experiments using the HTI-insert in the DECLIC facility. This HTI

insert has also proved to be an ideal platform for the observation of the density non-homogeneity

behaviour near the liquid-gas critical point of water. Indeed, we illustrate the recent progress of the

weightlessness investigations of the critical water sample under thermal gradients. We then discuss

newly proposed experiments utilizing a refurbished HTI-R insert where an optical cell filled by a salt –

critical water mixture would be integrated. We expect to measure various thermodynamic quantities,

such as, thermal diffusivity and mass diffusivity, and to study the gas-liquid phase separation and salt

precipitation phenomena under thermal gradients. Such basic studies of pure water and salt-water

mixtures constitute the first part of a complete research program to provide better understanding of the

SCWO (super critical water oxidation) process under weightlessness.


Study of the Super Critical Water Oxidation (SCWO) process utilizing the DECLIC facility on-

board ISS

S. Marre, Y. Garrabos, C. Lecoutre (ICMCB-CNRS, Université de Bordeaux, France), D. Beysens (CEA and

ESPCI-ParisTech, France), K. Jensen (Department of Chemical Engineering, MIT, Cambridge, MA, USA), M.

C. Hicks, U. G. Hegde (Nasa GRC, OH, USA)

Recently, the DECLIC (Dispositif pour l'Etude de la Croissance et des Liquides Critiques) facility supported

by CNES/NASA was successfully integrated into the International Space Station (ISS). Multiple science

inserts are developed for the DECLIC facility and are currently on-board ISS. In particular, the HTI-insert

was designed to study water near its critical point in a very stable thermal environment by using optical

transmission, light scattering, microscopy, and grid shadowscopy. In addition, a refurbished HTI-R insert

is currently in progress to study salt precipitation and transport in near-critical and supercritical water by

using DECLIC facility. These experiments are the first step of a complete research program to provide

better understanding of the fundamentals of the supercritical water oxidation (SCWO) process in

weightless condition. Main scientific objectives are focused on the dynamics of the organic solute

injection, dissolution, and oxidation in supercritical water. To satisfy with the scientific, technical and

safety requirements on board the ISS, a new experimental set-up based on high-pressure-high-

temperature microfluidic devices is currently used on ground to test the methanol and phenol oxidation

with a hydrogen peroxide aqueous solution. This set-up could also be integrated in a new insert called

HTI-SCWO insert, to be used in the DECLIC facility on board the ISS. After a brief presentation of the

ground-based results obtained in the frame of the collaborative program “MIT-France” between the

Supercritical Fluids Group at ICMCB-CNRS and the Jensen’s Lab at MIT, we will discuss newly proposed

experiments utilizing the HTI-SCWO insert to provide measurement and control of the basic operating

parameters involved in the SCWO process in weightlessness.


Optical thermometry for precision temperature control

J.A. Lipa / Physics Dept. Stanford University

Recent advances in optics have allowed the improvement of optical thermometry by orders of

magnitude. We describe a general-purpose fiber coupled optical thermometer that potentially has

resolution in the low nanokelvin range near room temperature. It is based on Fabry-Perot etalon

technology coupled with a low noise laser source. A proof-of-principle device was recently

demonstrated. The device could be integrated into a modified ALI insert for the DECLIC facility on the ISS

giving improved thermal control.

Poster Abstracts:

Superconducting Current Fluctuations as a Possible Source of Excess Noise in Transition Edge

Sensors

Talso Chui (JPL) and Jeff Filippini (Caltech)

Observational Astronomy and Cosmology are emerging areas of research that can be benefited from

both space and low temperature environment. Transition edge sensors (TES)are sensitive photon

detectors for the observations. Large current noise are observed in these sensors. It is not uncommon

to have noise that is more than 10 times the current noise from the resistance of the device. We

present thermodynamic calculation of superconducting current fluctuations and show that the

predicted noise density is of the same order as that observed in TES. Our calculation is based on an

extra degree of thermodynamic freedom available for a quantum fluid.

Space Fundamental Physics Program Past, Present and · PDF fileMark C. Lee/NASA Headquarters...

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