A system providing an optical frequency with an instability comparable to that of a hydrogen maser is presented. It consists of a $5$ $\mathrm{cm}$ long, vertically oriented silicon optical resonator operated at temperatures between $1.5$ $\mathrm{K}$ and $3.6$ $\mathrm{K}$ in a closed-cycle cryostat with low-temperature Joule-Thomson stage. We show that with a standard cryostat, a simple cryogenic optomechanical setup, no active or passive vibration isolation, a minimum frequency instability of $2.5\times10^{-15}$ at $τ=1500$ $\mathrm{s}$ integration time can be reached. The influence of pulse-tube vibrations was minimized by using a resonator designed for low acceleration sensitivity. With reduced optical laser power and interrogation duty cycle an ultra-low fractional frequency drift of $-2.6\times10^{-19}$/$\mathrm{s}$ is reached. At $3.5$ $\mathrm{K}$ the resonator frequency exhibits a vanishing thermal sensitivity and an ultra-small temperature derivative $8.5\times10^{-12}/\mathrm{K}^{2}$. These are favorable properties that should lead to high performance also in simpler cryostats not equipped with a Joule-Thomson stage.
Here, we study the paramagnetic ions behavior in presence of a strong microwave electromagnetic field sustained inside a cryogenic sapphire whispering gallery mode resonator. The high frequency measurement resolution that can be now achieved by comparing two CSOs permit for the first time to observe clearly the non-linearity of the resonator power sensitivity. These observations that in turn allow us to optimize the CSO operation, are well explained by the Electron Spin Resonance (ESR) saturation of the paramagnetic impurities contained in the sapphire crystal.
We report a homebuilt ultra-high-vacuum (UHV) rotating sample manipulator with cryogenic cooling. The sample holder is thermally anchored to a built-in cryogenic cold head through flexible copper beryllium strips, permitting continuous sample rotation. A similar contact mechanism is implemented for the electrical wiring to the sample holder for thermometry. The apparatus thus enables continuous sample rotation at regulated cryogenic temperatures in a UHV environment. We discuss the potential applications of this apparatus for cryogenic sputtering.
The Cryogenic Apparatus for Precision Tests of Argon Interactions with Neutrinos (CAPTAIN) is being built at Los Alamos National Laboratory. A hexagonal time projection chamber (TPC) with a 1 m drift length will be constructed inside a cryostat containing 7,700L of liquid argon. CAPTAIN will be used to test interactions using beams of neutrons and neutrinos. It will serve as a test bed for various options for the Long Baseline Neutrino Experiment (LBNE) including in the photon detection system. The current photon detection system will be described and future options discussed. The system is co…
Trapping ions in Paul traps requires high radio-frequency voltages, which are generated using resonators. When operating traps in a cryogenic environment, an in-vacuum resonator showing low loss is crucial to limit the thermal load to the cryostat. In this study, we present a guide for the design and production of compact, shielded cryogenic resonators. We produced and characterized three different types of resonators and furthermore demonstrate efficient impedance matching of these resonators at cryogenic temperatures.
We present the design and first measurement results for an ultra-stable cryogenically cooled optical sapphire resonator system with a potential relative frequency stability better than 3x10^-17. This level of oscillator stability allows for more precise tests of Einstein's theories of relativity and thus could help to find first hints of "new physics". We will give some details on a projected experiment to test Lorentz invariance that will utilize these cavities.
We describe the design, commissioning and operation of an ultra-low-vibration closed-cycle cryogenic ion trap apparatus. One hundred lines for low-frequency signals and eight microwave / radio frequency coaxial feed lines offer the possibility of implementing a small-scale ion-trap quantum processor or simulator. With all supply cables attached, more than 1.3 W of cooling power at 5 K is still available for absorbing energy from electrical pulses introduced to control ions. The trap itself is isolated from vibrations induced by the cold head using a helium exchange gas interface. The performan…
We report on the measurement and characterization of power to frequency conversion in the resonant mode of a cryogenic sapphire loaded cavity resonator, which is used as the frequency discriminating element of a loop oscillator circuit. Fluctuations of power incident on the resonator leads to changes in radiation pressure and temperature in the sapphire dielectric, both of which contribute to a shift in the resonance frequency. We measure a modulation and temperature independent radiation pressure induced power to frequency sensitivity of -0.15 Hz/mW and find that this is the primary factor li…
The frequency stability of lasers is limited by thermal noise in state-of-the-art frequency references. Further improvement requires operation at cryogenic temperature. In this context, we investigate a fiber-based ring resonator. Our system exhibits a first-order temperature-insensitive point around $3.55$ K, much lower than that of crystalline silicon. The observed low sensitivity with respect to vibrations ($<5\cdot{10^{-11}}\,\text{m}^{-1} \text{s}^{2}$), temperature ($-22(1)\cdot{10^{-9}}\,\text{K}^{-2}$) and pressure changes ($4.2(2)\cdot{10^{-11}}\,\text{mbar}^{-2}$) makes our approach …
We introduce an improved microwave calibration method for use in a cryogenic environment, based on a traditional three-standard calibration, the Thru-Reflect-Line (TRL) calibration. The modified calibration method takes advantage of additional information from multiple measurements of an ensemble of realizations of a superconducting resonator, as a new pseudo-Open standard, to correct errors in the TRL calibration. We also demonstrate an experimental realization of this in-situ broadband cryogenic calibration system utilizing cryogenic switches. All calibration measurements are done in the sam…
A cryogenic apparatus with a rotatable substrate for matrix isolation spectroscopy of BaF in neon crystals down to 3.2 K
Istituto Nazionale di Fisica Nucleare（意大利国家核物理研究所）；University of Ferrara（费拉拉大学）；University of Padua（帕多瓦大学）；National Quantum Science and Technology Institute（国家量子科学与技术研究所）
We propose a new type of cryogenic current amplifiers, in which low-frequency power spectrum of current can be measured through a measurement of microwave response of a superconducting resonant circuit shunted by a series array of Josephson junctions. From numerical analysis on the equivalent circuit, the numerical value of the input-referred current noise of the proposed amplifier is found to be two orders of magnitude lower than the noise floor measured with the conventional cryogenic current amplifiers based on high-electron-mobility transistors or superconducting quantum interference devic…
A magnetic coil operated at cryogenic temperatures is used to produce spatial, relative field gradients below 6 ppm/cm, stable for several hours. The apparatus is a prototype of the magnetic components for a neutron electric dipole moment (nEDM) search, which will take place at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory using ultra-cold neutrons (UCN). That search requires a uniform magnetic field to mitigate systematic effects and obtain long polarization lifetimes for neutron spin precession measurements. This paper details upgrades to a previously described apparat…
Suspended aluminium nanoelectromechanical resonators have been fabricated, and the manufacturing process is described in this work. Device motion is driven and detected with a magnetomotive method. The resonance response has been measured at 4.2 K temperature in vacuum and low pressure $^4$He gas. At low oscillation amplitudes the resonance response is linear, producing Lorentzian line shapes, and Q-values up to 4400 have been achieved. At higher oscillation amplitudes the devices show nonlinear Duffing-like behavior. The devices are found to be extremely sensitive to pressure in $^4$He gas. S…
We developed an apparatus to couple a 50-micrometer diameter whispering-gallery silica microtoroidal resonator in a helium-4 cryostat using a straight optical tapered-fiber at 1550nm wavelength. On a top-loading probe specifically adapted for increased mechanical stability, we use a specifically-developed "cryotaper" to optically probe the cavity, allowing thus to record the calibrated mechanical spectrum of the optomechanical system at low temperatures. We then demonstrate excellent thermalization of a 63-MHz mechanical mode of a toroidal resonator down to the cryostat's base temperature of 1…
We present a cryogenic setup where an optical Fabry-Perot resonator is coupled to a single-mode optical fiber with coupling efficiency above 90% at mK temperatures without realignment during cooling down. The setup is prealigned at room temperature to compensate for the thermal contraction and change of the refractive index of the optical components during cooling down. The high coupling efficiency is achieved by keeping the setup rotation-symmetric around the optical axis. The majority of the setup components are made of Invar (FeNi36) which minimizes the thermal contraction. High coupling ef…
State-of-the-art optical oscillators employing cryogenic reference cavities are limited in performance by the Brownian thermal noise associated with the mechanical dissipation of the mirror coatings. Recently, crystalline Al$_{1-x}$Ga$_{x}$As/GaAs coatings have emerged as a promising candidate for improved coating thermal noise. We present measurements of the frequency noise of two fully crystalline cryogenic reference cavities with Al$_{0.92}$Ga$_{0.08}$As/GaAs optical coatings. We report on previously unmeasured birefringent noise associated with anti-correlated frequency fluctuations betwee…
A cryogenic apparatus is described that enables a new experiment, nEDM@SNS, with a major improvement in sensitivity compared to the existing limit in the search for a neutron Electric Dipole Moment (EDM). It uses superfluid $^4$He to produce a high density of Ultra-Cold Neutrons (UCN) which are contained in a suitably coated pair of measurement cells. The experiment, to be operated at the Spallation Neutron Source at Oak Ridge National Laboratory, uses polarized $^3$He from an Atomic Beam Source injected into the superfluid $^4$He and transported to the measurement cells as a co-magnetometer. …
We studied noise properties of microwave signals transmitted through the cryogenic resonator. The experiments were performed with the 11.342 GHz sapphire loaded cavity resonator cooled to 6.2 K. Based on the measured transmission coefficient of the cryogenic resonator we computed its noise suppression function. This was done via Monte-Carlo simulations some details of which are discussed in this Letter. Next, we measured technical fluctuations of a signal incident on the cryogenic resonator. Having processed these data with the previously computed noise filtering "template" we inferred noise s…
The Cryogenic Sapphire Oscillator is today recognized for its unprecedented frequency stability, mainly coming from the exceptional physical properties of its resonator made in a high quality sapphire crystal. With these instruments, the fractional frequency measurement resolution, currently of the order of 1e-16, is such that it is possible to detect very small phenomena like residual resonator environmental sensitivities. Thus, we highlighted an unexpected magnetic sensitivity of the Cryogenic Sapphire Oscillator (CSO) at low magnetic field. The fractional frequency sensitivity has been prel…
We describe the construction of an apparatus designed to realize a hybrid quantum system comprised of a cryogenically cooled mechanical oscillator and ultra-cold $^{87}$Rb atoms coupled via light. The outstanding feature of our instrument is an in-situ adjustable asymmetric all-fiber membrane-in-the-middle cavity located inside an ultra-high vacuum dilution refrigerator based cryostat. We show that Bose-Einstein condensates of $N=2\times10^6$ atoms can be produced in less than 20 s and demonstrate a single photon optomechanical coupling strength of $g_0=2π\times9$ kHz employing a high-stress S…
We implemented a low noise current preamplifier for the readout of resistive bolometers. We tested the apparatus on thermometer resistances ranging from 10 Ohm to 500 Mohm. The use of current preamplifier overcomes constraints introduced by the readout time constant due to the thermometer resistance and the input capacitance. Using cold JFETs, this preamplifier board is shown to have very low noise: the Johnson noise of the source resistor (1 fA/Hz1/2) dominated in our noise measurements. We also implemented a lock-in chain using this preamplifier. Because of fast risetime, compensation of the…
We describe a liquid-cryogen free cryostat with ultra-low vibration levels which allows for continuous operation of a torsion balance at cryogenic temperatures. The apparatus uses a commercially available two-stage pulse-tube cooler and passive vibration isolation. The torsion balance exhibits torque noise levels lower than room temperature thermal noise by a factor of about four in the frequency range of 3-10mHz, limited by residual seismic motion and by radiative heating of the pendulum body. In addition to lowering thermal noise below room-temperature limits, the low-temperature environment…
We present two different techniques for achieving low resistance ($<$20 n$\rm Ω$) contacts between copper and aluminium at cryogenic temperatures. The best method is based on gold plating of the surfaces in an e-beam evaporator immediately after Ar plasma etching in the same apparatus, yielding resistances as low as 3 n$\rm Ω$ that are stable over time. The second approach involves inserting indium in the Al/Cu joint. For both methods, we believe key elements are surface polishing, total removal of the aluminum oxide surface layer, and temporary application of large (typ. 11 kN) compression fo…
This article reports on the long-term frequency stabilty characterisation of a new type of cryogenic sapphire oscillator using an autonomous pulse-tube cryocooler as its cold source. This new design enables a relative frequency stability of better than 4.5e-15 over one day of integration. This represents to our knowledge the best long-term frequency stability ever obtained with a signal source based on a macroscopic resonator.
We present a hybrid microwave SQUID multiplexer that combines two frequency-division multiplexing techniques to allow multiplexing a given number of cryogenic detectors with only a fraction of frequency encoding resonators. Similar to conventional microwave SQUID multiplexing, our multiplexer relies on inductively coupling non-hysteretic, unshunted rf-SQUIDs to superconducting microwave resonators as well as applying flux ramp modulation for output signal linearization. However, instead of utilizing one resonator per SQUID, we couple multiple SQUIDs to a common readout resonator and encode the…
We report on the development of a sapphire cryogenic microwave resonator oscillator long-term fractional frequency stability of 2x10^-17Sqrt[τ] for integration times τ>10^3 s and negative drift of about 2.2x10^-15/day. The short-term frequency instability of the oscillator is highly reproducible and also state-of-the-art: 5.6x10^-16 for an integration time of τ~ 20 s.
We have developed a contact-less technique for the real time measurement of a-thermal (Cooper-pair breaking) phonons in an absorber held at sub-Kelvin temperatures. In particular, a thin-film aluminum superconducting resonator was realized on a 30-grams high-resistivity silicon crystal. The lumped-element resonator is inductively excited/read-out by a radio-frequency microstrip feed-line deposited on another wafer; the sensor, a Kinetic Inductance Detector (KID), is read-out without any physical contact or wiring to the absorber. The resonator demonstrates excellent electrical properties, part…
We describe the newest generation of the SLAC Microresonator RF (SMuRF) electronics, a warm digital control and readout system for microwave-frequency resonator-based cryogenic detector and multiplexer systems such as microwave SQUID multiplexers ($μ$mux) or microwave kinetic inductance detectors (MKIDs). Ultra-sensitive measurements in particle physics and astronomy increasingly rely on large arrays of cryogenic sensors, which in turn necessitate highly multiplexed readout and accompanying room-temperature electronics. Microwave-frequency resonators are a popular tool for cryogenic multiplexi…
We demonstrate a hermetically sealed packaging system for integrated photonic devices at cryogenic temperatures with plug-and-play functionality. This approach provides the ability to encapsulate a controlled amount of gas into the optical package allowing helium to be used as a heat-exchange gas to thermalize photonic devices, or condensed into a superfluid covering the device. This packaging system was tested using a silicon-on-insulator slot waveguide resonator which fills with superfluid $^4$He below the transition temperature. To optimize the fiber-to-chip optical integration 690 tests we…
Yttrium Vanadate (YVO4) is a birefringent crystal material used in optical isolators and circulators with potentials for application in cryogenic microwave devices. As microwave properties of the YVO4 are not known, we measured the complex permittivity at the frequency of 25 GHz, using the Hakki-Coleman dielectric resonator technique in the temperature range from 13 K to 80 K. The real part of relative permittivity of YVO4 turned out to be similar to that of Sapphire - one of popular dielectric materials, used at microwave frequencies. The measured loss tangent tang δ of the YVO4 was of the or…
Two nominally identical ultra-stable cryogenic microwave oscillators are compared. Each incorporates a dielectric-sapphire resonator cooled to near 6 K in an ultra-low vibration cryostat using a low-vibration pulse-tube cryocooler. The phase noise for a single oscillator is measured at -105 dBc/Hz at 1 Hz offset on the 11.2 GHz carrier. The oscillator fractional frequency stability is characterized in terms of Allan deviation by 5.3 x 10^-16 tau^-1/2 + 9 x 10^-17 for integration times 0.1 s < tau < 1000 s and is limited by a flicker frequency noise floor below 1 x 10^-16. This result is better…
Experimental values for the viscosity of the radioactive hydrogen isotopologue tritium are still unknown in literature. Existing values from ab initio calculations disregard quantum mechanic effects and are therefore only good approximations for room temperature and above. To fill in these missing experimental values, a measurement setup has been designed, to measure the viscosity of gaseous hydrogen and its isotopologues (H$_2$, HD, HT, D$_2$, DT, T$_2$) at cryogenic temperatures. In this paper, the first results with this Cryogenic Viscosity Measurement Apparatus (Cryo-ViMA) of the viscosity…
Dielectric resonators are employed to build state-of-the-art low-noise and high- stability oscillators operating at room and cryogenic temperatures. A resonator temperature coefficient of frequency is one criterion of performance. This paper reports on predictions and measurements of this temperature coefficient of frequency for three types of cylindrically-symmetric Bragg resonators operated at microwave frequencies. At room temperature, microwave Bragg resonators have the best potential to reach extremely high Q-factors. Research has been conducted over the last decade on modeling, optimizin…
Thermal Nyquist noise fluctuations of high-$Q$ Bulk Acoustic Wave (BAW) cavities have been observed at cryogenic temperatures with a DC Superconducting Quantum Interference Device (SQUID) amplifier. High $Q$ modes with bandwidths of few tens of milliHz produce thermal fluctuations with a Signal-To-Noise ratio of up to 23dB. The estimated effective temperature from the Nyquist noise is in good agreement with the physical temperature of the device, confirming the validity of the equivalent circuit model and the non-existence of any excess resonator self-noise. The measurements also confirm that …
We present a cryogenic wafer mapper based on light emitting diodes (LEDs) for spatial mapping of a large microwave kinetic inductance detector (MKID) array. In this scheme, an array of LEDs, addressed by DC wires and collimated through horns onto the detectors, is mounted in front of the detector wafer. By illuminating each LED individually and sweeping the frequency response of all the resonators, we can unambiguously correspond a detector pixel to its measured resonance frequency. We have demonstrated mapping a 76.2 mm 90-pixel MKID array using a mapper containing 126 LEDs with 16 DC bias wi…
