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Sample records for frequency reference cavities

  1. Mounting system for optical frequency reference cavities

    NASA Technical Reports Server (NTRS)

    Notcutt, Mark (Inventor); Hall, John L. (Inventor); Ma, Long-Sheng (Inventor)

    2008-01-01

    A technique for reducing the vibration sensitivity of laser-stabilizing optical reference cavities is based upon an improved design and mounting method for the cavity, wherein the cavity is mounted vertically. It is suspended at one plane, around the spacer cylinder, equidistant from the mirror ends of the cavity. The suspension element is a collar of an extremely low thermal expansion coefficient material, which surrounds the spacer cylinder and contacts it uniformly. Once the collar has been properly located, it is cemented in place so that the spacer cylinder is uniformly supported and does not have to be squeezed at all. The collar also includes a number of cavities partially bored into its lower flat surface, around the axial bore. These cavities are support points, into which mounting base pins will be inserted. Hence the collar is supported at a minimum of three points.

  2. Flight-Like Optical Reference Cavity for GRACE Follow-On Laser Frequency Stabilization

    NASA Technical Reports Server (NTRS)

    Folkner, W. M.; deVine, G.; Klipstein, W. M.; McKenzie, K.; Spero, R.; Thompson, R.; Yu, N.; Stephens, M.; Leitch, J.; Pierce, R.; Shaddock, D.; Lam, T.

    2011-01-01

    We describe a prototype optical cavity and associated optics that has been developed to provide a stable frequency reference for a future space-based laser ranging system. This instrument is being considered for inclusion as a technology demonstration on the recently announced GRACE follow-on mission, which will monitor variations in the Earth's gravity field.

  3. Dual frequency optical cavity

    DOEpatents

    George, E.V.; Schipper, J.F.

    Method and apparatus for generating two distinct laser frequencies in an optical cavity, using a T configuration laser cavity and means for intermittently increasing or decreasing the index of refraction n of an associated transmission medium in one arm of the optical cavity to enhance laser action in one arm or the second arm of the cavity.

  4. Dual frequency optical cavity

    DOEpatents

    George, E. Victor; Schipper, John F.

    1985-01-01

    Method and apparatus for generating two distinct laser frequencies in an optical cavity, using a "T" configuration laser cavity and means for intermittently increasing or decreasing the index of refraction n of an associated transmission medium in one arm of the optical cavity to enhance laser action in one arm or the second arm of the cavity.

  5. Monochromatic radio frequency accelerating cavity

    DOEpatents

    Giordano, Salvatore

    1985-01-01

    A radio frequency resonant cavity having a fundamental resonant frequency and characterized by being free of spurious modes. A plurality of spaced electrically conductive bars are arranged in a generally cylindrical array within the cavity to define a chamber between the bars and an outer solid cylindrically shaped wall of the cavity. A first and second plurality of mode perturbing rods are mounted in two groups at determined random locations to extend radially and axially into the cavity thereby to perturb spurious modes and cause their fields to extend through passageways between the bars and into the chamber. At least one body of lossy material is disposed within the chamber to damp all spurious modes that do extend into the chamber thereby enabling the cavity to operate free of undesired spurious modes.

  6. Monochromatic radio frequency accelerating cavity

    DOEpatents

    Giordano, S.

    1984-02-09

    A radio frequency resonant cavity having a fundamental resonant frequency and characterized by being free of spurious modes. A plurality of spaced electrically conductive bars are arranged in a generally cylindrical array within the cavity to define a chamber between the bars and an outer solid cylindrically shaped wall of the cavity. A first and second plurality of mode perturbing rods are mounted in two groups at determined random locations to extend radially and axially into the cavity thereby to perturb spurious modes and cause their fields to extend through passageways between the bars and into the chamber. At least one body of lossy material is disposed within the chamber to damp all spurious modes that do extend into the chamber thereby enabling the cavity to operate free of undesired spurious modes.

  7. High frequency reference electrode

    DOEpatents

    Kronberg, J.W.

    1994-05-31

    A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or halo' at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes. 4 figs.

  8. High frequency reference electrode

    DOEpatents

    Kronberg, James W.

    1994-01-01

    A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or "halo" at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes.

  9. Frequency-feedback cavity enhanced spectrometer

    DOEpatents

    Hovde, David Christian; Gomez, Anthony

    2015-08-18

    A spectrometer comprising an optical cavity, a light source capable of producing light at one or more wavelengths transmitted by the cavity and with the light directed at the cavity, a detector and optics positioned to collect light transmitted by the cavity, feedback electronics causing oscillation of amplitude of the optical signal on the detector at a frequency that depends on cavity losses, and a sensor measuring the oscillation frequency to determine the cavity losses.

  10. Molecular frequency reference at 1.56  μm using a 12C16O overtone transition with the noise-immune cavity-enhanced optical heterodyne molecular spectroscopy method.

    PubMed

    Saraf, Shailendhar; Berceau, Paul; Stochino, Alberto; Byer, Robert; Lipa, John

    2016-05-15

    We report on a molecular clock based on the interrogation of the 3ν rotational-vibrational combination band at 1563 nm of carbon monoxide C1612O. The laser stabilization scheme is based on the noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) technique in frequency modulation (FM) saturation spectroscopy. We use a high-finesse ultra-low expansion (ULE) glass optical cavity with CO as the molecular reference for long-term stabilization of the cavity resonance. We report an Allan deviation of 1.8×10-12 at 1 s that improves to ∼3.5×10-14 with 1000 s of averaging. PMID:27176959

  11. Cavity-Enhanced Optical Frequency Comb Spectroscopy

    NASA Astrophysics Data System (ADS)

    Ye, Jun; Thorpe, Michael J.; Adler, Florian; Cossel, Kevin C.

    2009-06-01

    Cavity-enhanced optical frequency comb spectroscopy is a new technique that realizes simultaneously broad spectral coverage and high spectral resolution provided by an optical frequency comb as well as ultrahigh detection sensitivities enabled with a high-finesse optical cavity [1]. These powerful capabilities have been demonstrated in a series of experiments where real-time detection and identification of many different molecular states or species are achieved in a massively parallel fashion [2,3]. We will discuss the principle, technical requirements, and various implementations for this spectroscopic approach, as well as applications that include trace gas detections, human breath analysis, and characterization of cold and ultracold molecules [4,5,6]. References: [1] M. J. Thorpe, K. D. Moll, B. Safdi, and J. Ye, Science 311, 1595 (2006). [2] M. J. Thorpe, D. D. Hudson, K. D. Moll, J. Lasri, and J. Ye, Opt. Lett. 32, 307 (2007). [3] C. Gohle, B. Stein, A. Schliesser, T. Udem, and T. W. Hänsch, Phys. Rev. Lett. 99, 263902 (2007). [4] M. J. Thorpe, D. Balslev-Clausen, M. Kirchner, and J. Ye, Opt. Express. 16, 2387 (2008). [5] M. J. Thorpe and J. Ye, Appl. Phys. B 91, 397 (2008). [6] M. J. Thorpe, F. Adler, K. C. Cossel, M. H. G. de Miranda, and J. Ye, Chem. Phys. Lett. 468, 1 (2009).

  12. Frequency doubled, cavity dumped feedback laser

    NASA Technical Reports Server (NTRS)

    Sipes, Jr., Donald L. (Inventor); Robinson, Deborah L. (Inventor)

    1989-01-01

    Higher efficiency in cavity dumping and frequency doubling in a laser used to produce modulated output beam pulses is achieved by deflecting light out of the resonant cavity to a third mirror through a frequency doubler using an electro-optic modulator and a polarizing beamsplitter in the resonant cavity, or using just an acousto-optic modulator to deflect light out of the laser cavity in response to a control signal (electric or acoustic). The frequency doubler in front of the third mirror rotates the frequency doubled light so that it will pass out of the laser cavity through the polarizing beamsplitter, while undoubled frequency light is reflected by the polarizing beamsplitter back into the gain medium of the laser. In the case of using a type-II frequency doubler, a dichroic beamsplitter deflects out the frequency doubled light and passes the undoubled frequency light to the polarizing beamsplitter for return to the laser gain medium. If an acousto-optic modulator is used, it deflects light out of the primary laser cavity, so a polarizing beamsplitter is not needed, and only a dichroic beamsplitter is needed to separate frequency doubled light out of the path from the third mirror.

  13. Frequency References for Gravitational Wave Missions

    NASA Technical Reports Server (NTRS)

    Preston, Alix; Thrope, J. I.; Donelan, D.; Miner, L.

    2012-01-01

    The mitigation of laser frequency noise is an important aspect of interferometry for LISA-like missions. One portion of the baseline mitigation strategy in LISA is active stabilization utilizing opto-mechanical frequency references. The LISA optical bench is an attractive place to implement such frequency references due to its environmental stability and its access to primary and redundant laser systems. We have made an initial investigation of frequency references constructed using the techniques developed for the LISA and LISA Pathfinder optical benches. Both a Mach-Zehnder interferometer and triangular Fabry-Perot cavity have been successfully bonded to a Zerodur baseplate using the hydroxide bonding method. We will describe the construction of the bench along with preliminary stability results.

  14. Quantum frequency doubling based on tripartite entanglement with cavities

    NASA Astrophysics Data System (ADS)

    Juan, Guo; Zhi-Feng, Wei; Su-Ying, Zhang

    2016-02-01

    We analyze the entanglement characteristics of three harmonic modes, which are the output fields from three cavities with an input tripartite entangled state at fundamental frequency. The entanglement properties of the input beams can be maintained after their frequencies have been up-converted by the process of second harmonic generation. We have calculated the parametric dependences of the correlation spectrum on the initial squeezing factor, the pump power, the transmission coefficient, and the normalized analysis frequency of cavity. The numerical results provide references to choose proper experimental parameters for designing the experiment. The frequency conversion of the multipartite entangled state can also be applied to a quantum communication network. Project supported by the National Natural Science Foundation of China (Grant No. 91430109), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20111401110004), and the Natural Science Foundation of Shanxi Province, China (Grant No. 2014011005-3).

  15. Resonant Cavities for Frequency Tunable Gyrotrons

    NASA Astrophysics Data System (ADS)

    Sabchevski, S.; Idehara, T.

    2008-01-01

    In this paper we present, discuss and compare several concepts based on both well-known and novel ideas for tunable gyrotron cavities. Although theoretical and design considerations are presented and discussed together the main focus is on the underlying principles and feasibility of different approaches rather than on their specific implementations. Illustrative examples are provided for configurations and frequency range appropriate for gyrotrons used as radiation sources for NMR spectroscopy with signal enhancement through DNP.

  16. Thermal design and test results for SUNLITE ultra-stable reference cavity

    NASA Technical Reports Server (NTRS)

    Amundsen, Ruth M.

    1991-01-01

    SUNLITE (Stanford University-NASA Laser In-Space Technology Experiment) is a space-based experiment which uses a reference cavity to provide a stable frequency reference for a terahertz laser oscillator. Thermal stability of the cavity is a key factor in attaining a stable narrow-linewidth laser beam. The mount which is used to support and align the cavity will provide thermal isolation from the environment. The baseline requirement for thermal stability of the cavity is 0.025 C/min, but the design is directed toward achieving stability well beyond this requirement to improve the science data gained. A prototype of the cavity mount was fabricated and tested to characterize the thermal performance. The thermal vacuum test involved stable high-resolution temperature measurements and stable baseplate temperature control over long durations. Based on test data, the cavity mount design satisfies the severe requirement for the cavity thermal stability.

  17. Plasma processing of superconducting radio frequency cavities

    NASA Astrophysics Data System (ADS)

    Upadhyay, Janardan

    The development of plasma processing technology of superconducting radio frequency (SRF) cavities not only provides a chemical free and less expensive processing method, but also opens up the possibility for controlled modification of the inner surfaces of the cavity for better superconducting properties. The research was focused on the transition of plasma etching from two dimensional flat surfaces to inner surfaces of three dimensional (3D) structures. The results could be applicable to a variety of inner surfaces of 3D structures other than SRF cavities. Understanding the Ar/Cl2 plasma etching mechanism is crucial for achieving the desired modification of Nb SRF cavities. In the process of developing plasma etching technology, an apparatus was built and a method was developed to plasma etch a single cell Pill Box cavity. The plasma characterization was done with the help of optical emission spectroscopy. The Nb etch rate at various points of this cavity was measured before processing the SRF cavity. Cylindrical ring-type samples of Nb placed on the inner surface of the outer wall were used to measure the dependence of the process parameters on plasma etching. The measured etch rate dependence on the pressure, rf power, dc bias, temperature, Cl2 concentration and diameter of the inner electrode was determined. The etch rate mechanism was studied by varying the temperature of the outer wall, the dc bias on the inner electrode and gas conditions. In a coaxial plasma reactor, uniform plasma etching along the cylindrical structure is a challenging task due to depletion of the active radicals along the gas flow direction. The dependence of etch rate uniformity along the cylindrical axis was determined as a function of process parameters. The formation of dc self-biases due to surface area asymmetry in this type of plasma and its variation on the pressure, rf power and gas composition was measured. Enhancing the surface area of the inner electrode to reduce the

  18. Fast scanning cavity offset lock for laser frequency drift stabilization

    NASA Astrophysics Data System (ADS)

    Seymour-Smith, Nicolas; Blythe, Peter; Keller, Matthias; Lange, Wolfgang

    2010-07-01

    We have implemented a compact setup for long-term laser frequency stabilization. Light from a stable reference laser and several slave lasers is coupled into a confocal Fabry-Pérot resonator. By stabilizing the position of the transmission peaks of the slave lasers relative to successive peaks of the master laser as the length of the cavity is scanned over one free spectral range, the long-term stability of the master laser is transferred to the slave lasers. By using fast analog peak detection and low-latency microcontroller-based digital feedback, with a scanning frequency of 3 kHz, we obtain a feedback bandwidth of 380 Hz and a relative stability of better than 10 kHz at timescales longer than 1 s, a significant improvement on previous scanning-cavity stabilization systems.

  19. Thermal-noise limit in the frequency stabilization of lasers with rigid cavities.

    PubMed

    Numata, Kenji; Kemery, Amy; Camp, Jordan

    2004-12-17

    We evaluate thermal noise (Brownian motion) in a rigid reference cavity used for frequency stabilization of lasers, based on the mechanical loss of cavity materials and the numerical analysis of the mirror-spacer mechanics with the direct application of the fluctuation dissipation theorem. This noise sets a fundamental limit for the frequency stability achieved with a rigid frequency-reference cavity of order 1 Hz/ square root Hz (0.01 Hz/ square root Hz) at 10 mHz (100 Hz) at room temperature. This level coincides with the world-highest level stabilization results. PMID:15697887

  20. Laser frequency modulator for modulating a laser cavity

    DOEpatents

    Erbert, Gaylen V.

    1992-01-01

    The present invention relates to a laser frequency modulator for modulating a laser cavity. It is known in the prior art to utilize a PZT (piezoelectric transducer) element in combination with a mirror to change the cavity length of a laser cavity (which changes the laser frequency). Using a PZT element to drive the mirror directly is adequate at frequencies below 10 kHz. However, in high frequency applications (100 kHz and higher) PZT elements alone do not provide a sufficient change in the cavity length. The present invention utilizes an ultrasonic concentrator with a PZT element and mirror to provide modulation of the laser cavity. With an ultrasonic concentrator, the mirror element at the end of a laser cavity can move at larger amplitudes and higher frequencies.

  1. Cavities for electron spin resonance: predicting the resonant frequency

    NASA Astrophysics Data System (ADS)

    Colton, John; Miller, Kyle; Meehan, Michael; Spencer, Ross

    Microwave cavities are used in electron spin resonance to enhance magnetic fields. Dielectric resonators (DRs), pieces of high dielectric material, can be used to tailor the resonant frequency of a cavity. However, designing cavities with DRs to obtain desired frequencies is challenging and in general can only be done numerically with expensive software packages. We present a new method for calculating the resonant frequencies and corresponding field modes for cylindrically symmetric cavities and apply it to a cavity with vertically stacked DRs. The modes of an arbitrary cavity are expressed as an expansion of empty cavity modes. The wave equation for D gives rise to an eigenvalue equation whose eigenvalues are the resonant frequencies and whose eigenvectors yield the electric and magnetic fields of the mode. A test against theory for an infinitely long dielectric cylinder inside an infinite cavity yields an accuracy better than 0.4% for nearly all modes. Calculated resonant frequencies are also compared against experiment for quasi-TE011 modes in resonant cavities with ten different configurations of DRs; experimental results agree with predicted values with an accuracy better than 1.0%. MATLAB code is provided at http://www.physics.byu.edu/research/coltonlab/cavityresonance.

  2. Automated frequency tuning of SRF cavities at CEBAF

    SciTech Connect

    Chowdhary, M.; Doolittle, L.; Lahti, G.; Simrock, S.N.; Terrell, R.

    1995-12-31

    An automated cavity tuning procedure has been implemented in the CEBAF control system to tune the superconducting RF (SRF) cavities to their operating frequency of 1497 MHz. The capture range for coarse tuning algorithm (Burst Mode) is more than 20 cavity bandwidths (5 kHz). The fine tuning algorithm (Sweep Mode) calibrates the phase offset in the detuning angle measurement. This paper describes the implementation of these algorithms and experience of their operation in CEBAF control system. 3 refs., 5 figs.

  3. Perturbing Open Cavities: Anomalous Resonance Frequency Shifts in a Hybrid Cavity-Nanoantenna System.

    PubMed

    Ruesink, Freek; Doeleman, Hugo M; Hendrikx, Ruud; Koenderink, A Femius; Verhagen, Ewold

    2015-11-13

    The influence of a small perturbation on a cavity mode plays an important role in fields like optical sensing, cavity quantum electrodynamics, and cavity optomechanics. Typically, the resulting cavity frequency shift directly relates to the polarizability of the perturbation. Here, we demonstrate that particles perturbing a radiating cavity can induce strong frequency shifts that are opposite to, and even exceed, the effects based on the particles' polarizability. A full electrodynamic theory reveals that these anomalous results rely on a nontrivial phase relation between cavity and nanoparticle radiation, allowing backaction via the radiation continuum. In addition, an intuitive model based on coupled mode theory is presented that relates the phenomenon to retardation. Because of the ubiquity of dissipation, we expect these findings to benefit the understanding and engineering of a wide class of systems. PMID:26613442

  4. Three-dimensional self-consistent simulations of multipacting in superconducting radio frequency cavities

    SciTech Connect

    Chet Nieter

    2010-12-01

    Superconducting radio frequency (SRF) cavities are a popular choice among researchers designing new accelerators because of the reduced power losses due to surface resistance. However, SRF cavities still have unresolved problems, including the loss of power to stray electrons. Sources of these electrons are field emission from the walls and ionization of background gas, but the predominant source is secondary emission yield (SEY) from electron impact. When the electron motion is in resonance with the cavity fields the electrons strike the cavity surface repeatedly creating a resonant build up of electrons referred to as multipacting. Cavity shaping has successfully reduced multipacting for cavities used in very high energy accelerators. However, multipacting is still a concern for the cavity power couplers, where shaping is not possible, and for cavities used to accelerate particles at moderate velocities. This Phase II project built upon existing models in the VORPAL simulation framework to allow for simulations of multipacting behavior in SRF cavities and their associated structures. The technical work involved allowed existing models of secondary electron generation to work with the complex boundary conditions needed to model the cavity structures. The types of data produced by VORPAL were also expanded to include data common used by cavity designers to evaluate cavity performance. Post-processing tools were also modified to provide information directly related to the conditions that produce multipacting. These new methods were demonstrated by running simulations of a cavity design being developed by researchers at Jefferson National Laboratory to attempt to identify the multipacting that would be an issue for the cavity design being considered. These simulations demonstrate that VORPAL now has the capabilities to assist researchers working with SRF cavities to understand and identify possible multipacting issues with their cavity designs.

  5. Measurement of air refractive index fluctuation based on interferometry with two different reference cavity lengths.

    PubMed

    Chen, Qianghua; Luo, Huifu; Wang, Sumei; Wang, Feng; Chen, Xinhua

    2012-09-01

    A measurement method based on interferometry with two different reference cavity lengths is presented and applied in air refractive index measurement in which the two cavity lengths and a laser wavelength are combined to generate two wavelength equivalents of cavity. Corresponding calculation equations are derived, and the optical path configuration is designed, which is inspired by the traditional synthetic wavelength method. Theoretical analyses indicate that the measurement uncertainty of the determined index of refraction is about 2.3×10(-8), which is mainly affected by the length precision of the long vacuum cavity and the ellipticity of polarization components of the dual-frequency laser, and the range of nonambiguity is 3.0×10(-5), which is decided by the length difference of the two cavities. Experiment results show that the accuracy of air refractive index measurement is better than 5.0×10(-8) when the laboratory conditions changes slowly. The merit of the presented method is that the classical refractometry can be also used without evacuation of the gas cavity during the experiment. Furthermore, the application of the traditional synthetic wavelength method may be extended by using the wavelength equivalents of cavity, any value of which can be easily acquired by changing cavity length rather than using actual wavelengths whose number is limited. PMID:22945157

  6. Precise Frequency Measurements Using a Superconducting Cavity Stabilized Oscillator

    NASA Technical Reports Server (NTRS)

    Strayer, D. M.; Yeh, N.-C.; Jiang, W.; Anderson, V. L.; Asplund, N.

    1999-01-01

    Many physics experiments call on improved resolution to better define the experimental results, thus improving tests of theories. Modern microwave technology combined with high-Q resonators can achieve frequency readout and control with resolutions up to a part in 10(exp 18). When the physical quantity in question in the experiment can be converted to a frequency or a change in frequency, a high-stability microwave oscillator can be applied to obtain state-of-the-art precision. In this work we describe the overall physical concepts and the required experimental procedures for optimizing a high-resolution frequency measurement system that employs a high-Q superconducting microwave cavity and a low-noise frequency synthesizer. The basic approach is to resolve the resonant frequencies of a high-Q (Q > 10(exp 10)) cavity to extremely high precision (one part in 10(exp 17)- 10(exp 18)). Techniques for locking the synthesizer frequency to a resonant frequency of the superconducting cavity to form an ultra-stable oscillator are described. We have recently set up an ultra-high-vacuum high-temperature annealing system to process superconducting niobium cavities, and have been able to consistently achieve Q > 10(exp 9). We have integrated high-Q superconducting cavities with a low-noise microwave synthesizer in a phase-locked-loop to verify the frequency stability of the system. Effects that disturb the cavity resonant frequency (such as the temperature fluctuations and mechanical vibrations) and methods to mitigate those effects are also considered. Applicability of these techniques to experiments will be discussed, and our latest experimental progress in achieving high-resolution frequency measurements using the superconducting-cavity-stabilized-oscillator will be presented.

  7. Reference frequency transmission over optical fiber

    NASA Technical Reports Server (NTRS)

    Lutes, G.; Kirk, A.

    1986-01-01

    A 100-MHz reference frequency from a hydrogen maser frequency standard has been transmitted via optical fiber over a 14-km distance with a measured stability of 1.5 X 10 to the-15 power for 1000 seconds averaging time. This capability was demonstrated in a frequency distribution experiment performed in April, 1986. The reference frequency was transmitted over a single-mode fiber-optic link from Deep Space Station (DSS) 13 to DSS 12 and back. The background leading up to the experiment and the significance of stable reference frequency distribution in the Deep Space Network (DSN) is discussed. Also described are the experiment, including the fiber-optic link, the measurement method and equipment, and finally the results of the experiment.

  8. Design of digital Pound-Drever-Hall frequency stabilizing system for two-cavity dual-frequency Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Xing, Junhong; Jiao, Mingxing; Zheng, Yi; Zheng, Lingling

    2013-01-01

    Two-cavity dual-frequency Nd:YAG laser with large frequency difference can be used as an ideal light source for synthetic-wave absolute-distance interferometric system. The operation principle of the two-cavity dual-frequency Nd:YAG laser with large frequency difference has been introduced, and the frequency locking principle of the Pound-Drever-Hall (PDH) method has been analyzed. A FPGA-based digital PDH frequency stabilizing system for the two-cavity dual-frequency Nd:YAG laser has been designed, in which the same frequency reference of a high finesse Fabry-Perot cavity is used and two separate heterodyne interference sub-systems are employed so that two electrical error signals can be obtained. Having been processed through FPGA, the output signals are applied to drive the PZT frequency actuators attached on the two-cavity dual-frequency Nd:YAG laser, as a result both operating frequencies of the two-cavity dual-frequency Nd:YAG laser can be simultaneously frequency-locked to two resonant frequencies of the Fabry-Perot cavity. A frequency stability of better than 10-10 will be obtained by use of the digital PDH frequency locking system, which can meet the needs of synthetic-wave absolute-distance interferometry.

  9. Calculation of mechanical vibration frequencies of stiffened superconducting cavities

    SciTech Connect

    Black, S.J.; Spalek, G.

    1992-09-01

    We calculated the frequencies of transverse and longitudinal mechanical-vibration modes of the HEPL- modified, CERN/DESY four-cell superconducting cavity, using finite-element techniques. We compared the results of these calculations, including the stiffening of the cavity with rods, with mode frequencies measured at HEPL. The correlation between data was significant. The same techniques were also used to design and optimize the stiffening scheme for the seven-cell 805-MHz superconducting cavity being developed at Los Alamos. In this report, we describe the final stiffening scheme and the results of our calculations.

  10. Calculation of mechanical vibration frequencies of stiffened superconducting cavities

    SciTech Connect

    Black, S.J.; Spalek, G.

    1992-01-01

    We calculated the frequencies of transverse and longitudinal mechanical-vibration modes of the HEPL- modified, CERN/DESY four-cell superconducting cavity, using finite-element techniques. We compared the results of these calculations, including the stiffening of the cavity with rods, with mode frequencies measured at HEPL. The correlation between data was significant. The same techniques were also used to design and optimize the stiffening scheme for the seven-cell 805-MHz superconducting cavity being developed at Los Alamos. In this report, we describe the final stiffening scheme and the results of our calculations.

  11. Dielectric supported radio-frequency cavities

    DOEpatents

    Yu, David U. L.; Lee, Terry G.

    2000-01-01

    A device which improves the electrical and thermomechanical performance of an RF cavity, for example, in a disk-loaded accelerating structure. A washer made of polycrystalline diamond is brazed in the middle to a copper disk washer and at the outer edge to the plane wave transformer tank wall, thus dissipating heat from the copper disk to the outer tank wall while at the same time providing strong mechanical support to the metal disk. The washer structure eliminates the longitudinal connecting rods and cooling channels used in the currently available cavities, and as a result minimizes problems such as shunt impedance degradation and field distortion in the plane wave transformer, and mechanical deflection and uneven cooling of the disk assembly.

  12. High-Performance Optical Frequency References for Space

    NASA Astrophysics Data System (ADS)

    Schuldt, Thilo; Döringshoff, Klaus; Milke, Alexander; Sanjuan, Josep; Gohlke, Martin; Kovalchuk, Evgeny V.; Gürlebeck, Norman; Peters, Achim; Braxmaier, Claus

    2016-06-01

    A variety of future space missions rely on the availability of high-performance optical clocks with applications in fundamental physics, geoscience, Earth observation and navigation and ranging. Examples are the gravitational wave detector eLISA (evolved Laser Interferometer Space Antenna), the Earth gravity mission NGGM (Next Generation Gravity Mission) and missions, dedicated to tests of Special Relativity, e.g. by performing a Kennedy- Thorndike experiment testing the boost dependence of the speed of light. In this context we developed optical frequency references based on Doppler-free spectroscopy of molecular iodine; compactness and mechanical and thermal stability are main design criteria. With a setup on engineering model (EM) level we demonstrated a frequency stability of about 2·10-14 at an integration time of 1 s and below 6·10-15 at integration times between 100s and 1000s, determined from a beat-note measurement with a cavity stabilized laser where a linear drift was removed from the data. A cavity-based frequency reference with focus on improved long-term frequency stability is currently under development. A specific sixfold thermal shield design based on analytical methods and numerical calculations is presented.

  13. Mechanical properties of niobium radio-frequency cavities

    DOE PAGESBeta

    Ciovati, Gianluigi; Dhakal, Pashupati; Matalevich, Joseph R.; Myneni, Ganapati Rao; Schmidt, A.; Iversen, J.; Matheisen, A.; Singer, W.

    2015-07-02

    Radio-frequency cavities made of bulk niobium are one of the components used in modern particle accelerators. The mechanical stability is an important aspect of cavity design, which typically relies on finite-element analysis simulations using material properties from tensile tests on sample. This contribution presents the results of strain and resonant frequency measurements as a function of a uniform pressure up to 722 kPa, applied to single-cell niobium cavities with different crystallographic structure, purity and treatments. In addition, burst tests of high-purity multi-cell cavities with different crystallographic structure have been conducted up to the tensile strength of the material. Finite-element analysismore » of the single-cell cavity geometry is in good agreement with the observed behavior in the elastic regime assuming a Young's modulus value of 88.5 GPa and a Poisson's ratio of 0.4, regardless of crystallographic structure, purity or treatment. However, the measured yield strength and tensile strength depend on crystallographic structure, material purity and treatment. In particular, the results from this study show that the mechanical properties of niobium cavities with large crystals are comparable to those of cavities made of fine-grain niobium.« less

  14. Mechanical properties of niobium radio-frequency cavities

    SciTech Connect

    Ciovati, Gianluigi; Dhakal, Pashupati; Matalevich, Joseph R.; Myneni, Ganapati Rao; Schmidt, A.; Iversen, J.; Matheisen, A.; Singer, W.

    2015-07-02

    Radio-frequency cavities made of bulk niobium are one of the components used in modern particle accelerators. The mechanical stability is an important aspect of cavity design, which typically relies on finite-element analysis simulations using material properties from tensile tests on sample. This contribution presents the results of strain and resonant frequency measurements as a function of a uniform pressure up to 722 kPa, applied to single-cell niobium cavities with different crystallographic structure, purity and treatments. In addition, burst tests of high-purity multi-cell cavities with different crystallographic structure have been conducted up to the tensile strength of the material. Finite-element analysis of the single-cell cavity geometry is in good agreement with the observed behavior in the elastic regime assuming a Young's modulus value of 88.5 GPa and a Poisson's ratio of 0.4, regardless of crystallographic structure, purity or treatment. However, the measured yield strength and tensile strength depend on crystallographic structure, material purity and treatment. In particular, the results from this study show that the mechanical properties of niobium cavities with large crystals are comparable to those of cavities made of fine-grain niobium.

  15. Laser frequency stabilization using folded cavity and mirror reflectivity tuning

    NASA Astrophysics Data System (ADS)

    Liu, X.; Cassou, K.; Chiche, R.; Dupraz, K.; Favier, P.; Flaminio, R.; Honda, Y.; Huang, W. H.; Martens, A.; Michel, C.; Pinard, L.; Sassolas, B.; Soskov, V.; Tang, C. X.; Zomer, F.

    2016-06-01

    A new method of laser frequency stabilization using polarization property of an optical cavity is proposed. In a standard Fabry-Perot cavity, the coating layers thickness of cavity mirrors is calculated to obtain the same phase shift for s- and p-wave but a slight detuning from the nominal thickness can produce s- and p-wave phase detuning. As a result, each wave accumulates a different round-trip phase shift and resonates at a different frequency. Using this polarization property, an error signal is generated by a simple setup consisting of a quarter wave-plate rotated at 45°, a polarizing beam splitter and two photodiodes. This method exhibits similar error signal as the Pound-Drever-Hall technique but without need for any frequency modulation. Lock theory and experimental results are presented in this paper.

  16. Noise-Immune Cavity-Enhanced Optical Frequency Comb Spectroscopy

    NASA Astrophysics Data System (ADS)

    Rutkowski, Lucile; Khodabakhsh, Amir; Johanssson, Alexandra C.; Foltynowicz, Aleksandra

    2015-06-01

    We present noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS), a recently developed technique for sensitive, broadband, and high resolution spectroscopy. In NICE-OFCS an optical frequency comb (OFC) is locked to a high finesse cavity and phase-modulated at a frequency precisely equal to (a multiple of) the cavity free spectral range. Since each comb line and sideband is transmitted through a separate cavity mode in exactly the same way, any residual frequency noise on the OFC relative to the cavity affects each component in an identical manner. The transmitted intensity contains a beat signal at the modulation frequency that is immune to frequency-to-amplitude noise conversion by the cavity, in a way similar to continuous wave noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS). The light transmitted through the cavity is detected with a fast-scanning Fourier-transform spectrometer (FTS) and the NICE-OFCS signal is obtained by fast Fourier transform of the synchronously demodulated interferogram. Our NICE-OFCS system is based on an Er:fiber femtosecond laser locked to a cavity with a finesse of ˜9000 and a fast-scanning FTS equipped with a high-bandwidth commercial detector. We measured NICE-OFCS signals from the 3νb{1}+νb{3} overtone band of CO_2 around 1.57 μm and achieved absorption sensitivity 6.4×10-11cm-1 Hz-1/2 per spectral element, corresponding to a minimum detectable CO_2 concentration of 25 ppb after 330 s integration time. We will describe the principles of the technique and its technical implementation, and discuss the spectral lineshapes of the NICE-OFCS signals. A. Khodabakhsh, C. Abd Alrahman, and A. Foltynowicz, Opt. Lett. 39, 5034-5037 (2014). J. Ye, L. S. Ma, and J. L. Hall, J. Opt. Soc. Am. B 15, 6-15 (1998). A. Khodabakhsh, A. C. Johansson, and A. Foltynowicz, Appl. Phys. B (2015) doi:10.1007/s00340-015-6010-7.

  17. Cavity mode frequencies and strong optomechanical coupling in two-membrane cavity optomechanics

    NASA Astrophysics Data System (ADS)

    Li, Jie; Xuereb, André; Malossi, Nicola; Vitali, David

    2016-08-01

    We study the cavity mode frequencies of a Fabry–Pérot cavity containing two vibrating dielectric membranes. We derive the equations for the mode resonances and provide approximate analytical solutions for them as a function of the membrane positions, which act as an excellent approximation when the relative and center-of-mass position of the two membranes are much smaller than the cavity length. With these analytical solutions, one finds that extremely large optomechanical coupling of the membrane relative motion can be achieved in the limit of highly reflective membranes when the two membranes are placed very close to a resonance of the inner cavity formed by them. We also study the cavity finesse of the system and verify that, under the conditions of large coupling, it is not appreciably affected by the presence of the two membranes. The achievable large values of the ratio between the optomechanical coupling and the cavity decay rate, g/κ , make this two-membrane system the simplest promising platform for implementing cavity optomechanics in the strong coupling regime.

  18. Resonant-frequency discharge in a multi-cell radio frequency cavity

    SciTech Connect

    Popović, S.; Upadhyay, J.; Nikolić, M.; Vušković, L.; Mammosser, J.

    2014-11-07

    We are reporting experimental results on a microwave discharge operating at resonant frequency in a multi-cell radio frequency (RF) accelerator cavity. Although the discharge operated at room temperature, the setup was constructed so that it could be used for plasma generation and processing in fully assembled active superconducting radio-frequency cryo-module. This discharge offers a mechanism for removal of a variety of contaminants, organic or oxide layers, and residual particulates from the interior surface of RF cavities through the interaction of plasma-generated radicals with the cavity walls. We describe resonant RF breakdown conditions and address the issues related to resonant detuning due to sustained multi-cell cavity plasma. We have determined breakdown conditions in the cavity, which was acting as a plasma vessel with distorted cylindrical geometry. We discuss the spectroscopic data taken during plasma removal of contaminants and use them to evaluate plasma parameters, characterize the process, and estimate the volatile contaminant product removal.

  19. External cavity diode laser with very-low frequency drift

    NASA Astrophysics Data System (ADS)

    Takamizawa, Akifumi; Yanagimachi, Shinya; Ikegami, Takeshi

    2016-03-01

    An external cavity diode laser with significant mechanical robustness was installed in a housing that was sealed from outside for eliminating variations in the refractive index of air. Using the feedback signal for a frequency lock, it was found that the variation in the laser frequency under free running was suppressed to 275 MHz over one month and depended on the room temperature. Moreover, the upper limit of the linear frequency drift rate was evaluated as intrinsically 40 Hz/s. The frequency lock is expected to be sustainable for more than 110 days with temperature-controlled housing.

  20. Fabrication of the APS Storage Ring radio frequency accelerating cavities

    SciTech Connect

    Primdahl, K.; Bridges, J.; DePaola, F.; Kustom, R.; Snee, D.

    1993-07-01

    Specification, heat treatment, strength, and fatigue life of the Advanced Photon Source (APS) Storage Ring 352-MHz radio frequency (RF) accelerating cavity copper is discussed. Heat transfer studies, including finite element analysis, and configuration of water cooling is described. Requirements for and techniques of machining are considered. Braze and electron beam joint designs are compared. Vacuum considerations during fabrication are discussed.

  1. Using Frequency Noise Feedback to Improve Stability in Extended Cavity Diode Lasers

    NASA Astrophysics Data System (ADS)

    Pugh, Mckinley; Durfee, Dallin

    2016-03-01

    We are developing a feedback system to stabilize extended cavity diode lasers using frequency noise. In other literature, amplitude noise has been used to predict and prevent mode hops. We've found, however, that amplitude noise only correlates to an impending mode hop when the laser is locked to a frequency reference. We have found evidence that the amplitude noise is generated from more fundamental frequency noise by the lock feedback. We therefore propose a way to use frequency noise directly to generate a signal to predict and prevent mode hops.

  2. Dual-etalon, cavity-ring-down, frequency comb spectroscopy.

    SciTech Connect

    Strecker, Kevin E.; Chandler, David W.

    2010-10-01

    The 'dual etalon frequency comb spectrometer' is a novel low cost spectometer with limited moving parts. A broad band light source (pulsed laser, LED, lamp ...) is split into two beam paths. One travels through an etalon and a sample gas, while the second arm is just an etalon cavity, and the two beams are recombined onto a single detector. If the free spectral ranges (FSR) of the two cavities are not identical, the intensity pattern at the detector with consist of a series of heterodyne frequencies. Each mode out of the sample arm etalon with have a unique frequency in RF (radio-frequency) range, where modern electronics can easily record the signals. By monitoring these RF beat frequencies we can then determine when an optical frequencies is absorbed. The resolution is set by the FSR of the cavity, typically 10 MHz, with a bandwidth up to 100s of cm{sup -1}. In this report, the new spectrometer is described in detail and demonstration experiments on Iodine absorption are carried out. Further we discuss powerful potential next generation steps to developing this into a point sensor for monitoring combustion by-products, environmental pollutants, and warfare agents.

  3. Use of a variable frequency source with a single-mode cavity to process ceramic filaments

    SciTech Connect

    Vogt, G.J.; Regan, A.H.; Rohlev, A.S.; Curtin, M.T.

    1995-05-01

    =Rapid feedback control is needed for practical microwave processing of continuous ceramic oxide filaments to regulate the process temperature where the dielectric properties of the filaments change rapidly with temperature. A broadband traveling wave tube (TWT) amplifier provides a highly versatile process control platform for filament processing. By comparing a rf signal from the cavity to a reference signal from the TWT, phase information can be used in a negative feedback loop to allow the oscillator to track the cavity frequency as it shifts due to the changing dielectric constant in the filaments being heated. By sampling the field level in the cavity with a detector, amplitude control can be done to maintain a consistent electric field level in the cavity, which is important for controlling the filament heating and temperature. The system design will be discussed along with application data for commercial ceramic samples.

  4. Fractional frequency instability in the 10{sup -14} range with a thermal beam optical frequency reference

    SciTech Connect

    McFerran, John J.; Luiten, Andre N.

    2010-02-15

    We demonstrate a means of increasing the signal-to-noise ratio in a Ramsey-Borde interferometer with spatially separated oscillatory fields on a thermal atomic beam. The {sup 1}S{sub 0}{r_reversible}{sup 3}P{sub 1} intercombination line in neutral {sup 40}Ca is used as a frequency discriminator, with an extended cavity diode laser at 423 nm probing the ground state population after a Ramsey-Borde sequence of 657 nm light-field interactions with the atoms. Evaluation of the instability of the Ca frequency reference is carried out by comparison with (i) a hydrogen-maser and (ii) a cryogenic sapphire oscillator. In the latter case the Ca reference exhibits a square-root {Lambda} variance of 9.2x10{sup -14} at 1 s and 2.0x10{sup -14} at 64 s. This is an order-of-magnitude improvement for optical beam frequency references, to our knowledge. The shot noise of the readout fluorescence produces a limiting square-root {Lambda} variance of 7x10{sup -14}/{radical}({tau}), highlighting the potential for improvement. This work demonstrates the feasibility of a portable frequency reference in the optical domain with 10{sup -14} range frequency instability.

  5. Transportable cavity-stabilized laser system for optical carrier frequency transmission experiments.

    PubMed

    Parker, B; Marra, G; Johnson, L A M; Margolis, H S; Webster, S A; Wright, L; Lea, S N; Gill, P; Bayvel, P

    2014-12-10

    We report the design and performance of a transportable laser system at 1543 nm, together with its application as the source for a demonstration of optical carrier frequency transmission over 118 km of an installed dark fiber network. The laser system is based around an optical reference cavity featuring an elastic mounting that bonds the cavity to its support, enabling the cavity to be transported without additional clamping. The cavity exhibits passive fractional frequency insensitivity to vibration along the optical axis of 2.0×10(-11)  m(-1) s(2). With active fiber noise cancellation, the optical carrier frequency transmission achieves a fractional frequency instability, measured at the user end, of 2.6×10(-16) at 1 s, averaging down to below 3×10(-18) after 20,000 s. The fractional frequency accuracy of the transfer is better than 3×10(-18). This level of performance is sufficient for comparison of state-of-the-art optical frequency standards and is achieved in an urban fiber environment. PMID:25608055

  6. Frequency-Agile Differential Cavity Ring-Down Spectroscopy

    NASA Astrophysics Data System (ADS)

    Reed, Zachary; Hodges, Joseph

    2015-06-01

    The ultimate precision of highly sensitive cavity-enhanced spectroscopic measurements is often limited by interferences (etalons) caused by weak coupled-cavity effects. Differential measurements of ring-down decay constants have previously been demonstrated to largely cancel these effects, but the measurement acquisition rates were relatively low [1,2]. We have previously demonstrated the use of frequency agile rapid scanning cavity ring-down spectroscopy (FARS-CRDS) for acquisition of absorption spectra [3]. Here, the method of rapidly scanned, frequency-agile differential cavity ring-down spectroscopy (FADS-CRDS) is presented for reducing the effect of these interferences and other shot-to-shot statistical variations in measured decay times. To this end, an electro-optic phase modulator (EOM) with a bandwidth of 20 GHz is driven by a microwave source, generating pairs of sidebands on the probe laser. The optical resonator acts as a highly selective optical filter to all laser frequencies except for one tunable sideband. This sideband may be stepped arbitrarily from mode-to-mode of the ring-down cavity, at a rate limited only by the cavity buildup/decay time. The ability to probe any cavity mode across the EOM bandwidth enables a variety of methods for generating differential spectra. The differential mode spacing may be changed, and the effect of this method on suppressing the various coupled-cavity interactions present in the system is discussed. Alternatively, each mode may also be differentially referenced to a single point, providing immunity to temporal variations in the base losses of the cavity while allowing for conventional spectral fitting approaches. Differential measurements of absorption are acquired at 3.3 kHz and a minimum detectable absorption coefficient of 5 x10-12 cm-1 in 1 s averaging time is achieved. 1. J. Courtois, K. Bielska, and J.T Hodges J. Opt. Soc. Am. B, 30, 1486-1495, 2013 2. H.F. Huang and K.K. Lehmann App. Optics 49, 1378

  7. Absolute molecular transition frequencies measured by three cavity-enhanced spectroscopy techniques.

    PubMed

    Cygan, A; Wójtewicz, S; Kowzan, G; Zaborowski, M; Wcisło, P; Nawrocki, J; Krehlik, P; Śliwczyński, Ł; Lipiński, M; Masłowski, P; Ciuryło, R; Lisak, D

    2016-06-01

    Absolute frequencies of unperturbed (12)C(16)O transitions from the near-infrared (3-0) band were measured with uncertainties five-fold lower than previously available data. The frequency axis of spectra was linked to the primary frequency standard. Three different cavity enhanced absorption and dispersion spectroscopic methods and various approaches to data analysis were used to estimate potential systematic instrumental errors. Except for a well established frequency-stabilized cavity ring-down spectroscopy, we applied the cavity mode-width spectroscopy and the one-dimensional cavity mode-dispersion spectroscopy for measurement of absorption and dispersion spectra, respectively. We demonstrated the highest quality of the dispersion line shape measured in optical spectroscopy so far. We obtained line positions of the Doppler-broadened R24 and R28 transitions with relative uncertainties at the level of 10(-10). The pressure shifting coefficients were measured and the influence of the line asymmetry on unperturbed line positions was analyzed. Our dispersion spectra are the first demonstration of molecular spectroscopy with both axes of the spectra directly linked to the primary frequency standard, which is particularly desirable for the future reference-grade measurements of molecular spectra. PMID:27276950

  8. Absolute molecular transition frequencies measured by three cavity-enhanced spectroscopy techniques

    NASA Astrophysics Data System (ADS)

    Cygan, A.; Wójtewicz, S.; Kowzan, G.; Zaborowski, M.; Wcisło, P.; Nawrocki, J.; Krehlik, P.; Śliwczyński, Ł.; Lipiński, M.; Masłowski, P.; Ciuryło, R.; Lisak, D.

    2016-06-01

    Absolute frequencies of unperturbed 12C16O transitions from the near-infrared (3-0) band were measured with uncertainties five-fold lower than previously available data. The frequency axis of spectra was linked to the primary frequency standard. Three different cavity enhanced absorption and dispersion spectroscopic methods and various approaches to data analysis were used to estimate potential systematic instrumental errors. Except for a well established frequency-stabilized cavity ring-down spectroscopy, we applied the cavity mode-width spectroscopy and the one-dimensional cavity mode-dispersion spectroscopy for measurement of absorption and dispersion spectra, respectively. We demonstrated the highest quality of the dispersion line shape measured in optical spectroscopy so far. We obtained line positions of the Doppler-broadened R24 and R28 transitions with relative uncertainties at the level of 10-10. The pressure shifting coefficients were measured and the influence of the line asymmetry on unperturbed line positions was analyzed. Our dispersion spectra are the first demonstration of molecular spectroscopy with both axes of the spectra directly linked to the primary frequency standard, which is particularly desirable for the future reference-grade measurements of molecular spectra.

  9. T-shaped cavity dual-frequency Nd:YAG laser with electro-optical modulation

    NASA Astrophysics Data System (ADS)

    Xing, Junhong; Jiao, Mingxing; Liu, Yun

    2016-05-01

    A T-shaped cavity dual-frequency Nd:YAG laser with electro-optical modulation is proposed, which consists of both p- and s-cavities sharing the same gain medium of Nd:YAG. Each cavity was not only able to select longitudinal mode but also tune frequency using an electro-optic birefringent filter polarization beam splitter + lithium niobate. The frequency difference of dual frequency was tuned through the whole gain bandwidth of Nd:YAG, which is far above the usually accepted free spectral range value in the case of a single-axis laser. As a result, the simultaneous operation of orthogonally and linearly polarized dual-frequency laser was obtained, which coincides with the theoretical analysis based on Jones matrices. The obtained frequency difference ranges from 0 to 132 GHz. This offers a simple and widely tunable source with potential for portable frequency reference applications in terahertz-wave generation and absolute-distance interferometry measurement areas.

  10. Gravitational wave detection with high frequency phonon trapping acoustic cavities

    NASA Astrophysics Data System (ADS)

    Goryachev, Maxim; Tobar, Michael E.

    2014-11-01

    There are a number of theoretical predictions for astrophysical and cosmological objects, which emit high frequency (1 06-1 09 Hz ) gravitation waves (GW) or contribute somehow to the stochastic high frequency GW background. Here we propose a new sensitive detector in this frequency band, which is based on existing cryogenic ultrahigh quality factor quartz bulk acoustic wave cavity technology, coupled to near-quantum-limited SQUID amplifiers at 20 mK. We show that spectral strain sensitivities reaching 1 0-22 per √{Hz } per mode is possible, which in principle can cover the frequency range with multiple (>100 ) modes with quality factors varying between 1 06 and 1 010 allowing wide bandwidth detection. Due to its compactness and well-established manufacturing process, the system is easily scalable into arrays and distributed networks that can also impact the overall sensitivity and introduce coincidence analysis to ensure no false detections.

  11. A millimeter-scale atomic frequency reference

    NASA Astrophysics Data System (ADS)

    Schwindt, Peter; Kitching, John; Knappe, Svenja; Liew, Li-Anne; Shah, Vishal; Moreland, John; Hollberg, Leo

    2004-05-01

    We are developing a MEMS-fabricated chip-scale atomic clock that uses all-optical excitation to interrogate the hyperfine splitting of cesium. To date, we have constructed several clock physics packages that include a laser, micro-optics package, cesium vapor cell, and photo diode. A recent physics package had a fractional frequency instability of 3*10-10 at one second, had a volume of 9.5 mm^3, and used 75 mW of power. We are working to decrease power consumption of physics package to 15 mW and to integrate control electronics and a local oscillator, such that the entire clock will be 1 cm^3 in size and use 30 mW of power, allowing battery operation. Because of the MEMS fabrication techniques employed, frequency references of this type could be assembled at the wafer level, enabling low-cost mass-production of thousands of identical units with the same process sequence, and easy integration with other electronics.

  12. Compact microwave cavity for high performance rubidium frequency standards.

    PubMed

    Stefanucci, Camillo; Bandi, Thejesh; Merli, Francesco; Pellaton, Matthieu; Affolderbach, Christoph; Mileti, Gaetano; Skrivervik, Anja K

    2012-10-01

    The design, realization, and characterization of a compact magnetron-type microwave cavity operating with a TE(011)-like mode are presented. The resonator works at the rubidium hyperfine ground-state frequency (i.e., 6.835 GHz) by accommodating a glass cell of 25 mm diameter containing rubidium vapor. Its design analysis demonstrates the limitation of the loop-gap resonator lumped model when targeting such a large cell, thus numerical optimization was done to obtain the required performances. Microwave characterization of the realized prototype confirmed the expected working behavior. Double-resonance and Zeeman spectroscopy performed with this cavity indicated an excellent microwave magnetic field homogeneity: the performance validation of the cavity was done by achieving an excellent short-term clock stability as low as 2.4 × 10(-13) τ(-1/2). The achieved experimental results and the compact design make this resonator suitable for applications in portable atomic high-performance frequency standards for both terrestrial and space applications. PMID:23126789

  13. Use of a variable frequency source with a single-mode-cavity to process ceramic filaments

    SciTech Connect

    Vogt, G.T.; Regan, A.H.; Rohlev, A.S.; Curtin, M.T.

    1995-12-31

    Rapid feedback control is needed for practical microwave processing of continuous ceramic oxide filaments to regulate the process temperature where the dielectric properties of the filaments change rapidly with temperature. A broadband traveling wave tube (TWT) amplifier provides a highly versatile process control platform for filament processing. By comparing a RF signal from the cavity to a reference signal from the TWT, phase information can be used in a negative feedback loop to allow the oscillator to track the cavity frequency as it shifts due to the changing dielectric constant in the filaments being heated. By sampling the electric field level in the cavity with a detector, amplitude control can be done to maintain a constant absorbed power in a fiber tow, which is important for controlling the tow heating and temperature. The system design will be discussed along with application data for commercial ceramic samples.

  14. Design verification of large time constant thermal shields for optical reference cavities.

    PubMed

    Zhang, J; Wu, W; Shi, X H; Zeng, X Y; Deng, K; Lu, Z H

    2016-02-01

    In order to achieve high frequency stability in ultra-stable lasers, the Fabry-Pérot reference cavities shall be put inside vacuum chambers with large thermal time constants to reduce the sensitivity to external temperature fluctuations. Currently, the determination of thermal time constants of vacuum chambers is based either on theoretical calculation or time-consuming experiments. The first method can only apply to simple system, while the second method will take a lot of time to try out different designs. To overcome these limitations, we present thermal time constant simulation using finite element analysis (FEA) based on complete vacuum chamber models and verify the results with measured time constants. We measure the thermal time constants using ultrastable laser systems and a frequency comb. The thermal expansion coefficients of optical reference cavities are precisely measured to reduce the measurement error of time constants. The simulation results and the experimental results agree very well. With this knowledge, we simulate several simplified design models using FEA to obtain larger vacuum thermal time constants at room temperature, taking into account vacuum pressure, shielding layers, and support structure. We adopt the Taguchi method for shielding layer optimization and demonstrate that layer material and layer number dominate the contributions to the thermal time constant, compared with layer thickness and layer spacing. PMID:26931831

  15. Applications of Cavity-Enhanced Direct Frequency Comb Spectroscopy

    NASA Astrophysics Data System (ADS)

    Cossel, Kevin C.; Adler, Florian; Maslowski, Piotr; Ye, Jun

    2010-06-01

    Cavity-enhanced direct frequency comb spectroscopy (CE-DFCS) is a unique technique that provides broad bandwidth, high resolution, and ultra-high detection sensitivities. This is accomplished by combining a femtosecond laser based optical frequency comb with an enhancement cavity and a broadband, multichannel imaging system. These systems are capable of simultaneously recording many terahertz of spectral bandwidth with sub-gigahertz resolution and absorption sensitivities of 1×10-7 cm-1 Hz-1/2. In addition, the ultrashort pulses enable efficient nonlinear processes, which makes it possible to reach spectral regions that are difficult to access with conventional laser sources. We will present an application of CE-DFCS for trace impurity detection in the semiconductor processing gas arsine near 1.8 μm and the development of a high-power, mid-infrared frequency comb for breath analysis in the 2.8-4.8 μm region. M. J. Thorpe, K. D. Moll, R. J. Jones, B. Safdi, and J. Ye. Science 311, 1595-1599 (2006) F. Adler, M. J. Thorpe, K. C. Cossel, and J. Ye. Annu. Rev. Anal. Chem. 3, 175-205 (2010) F. Adler, K. C. Cossel, M. J. Thorpe, I. Hartl, M. E. Fermann, and J. Ye. Opt. Lett. 34, 1330-1332 (2009)

  16. Resonant-frequency discharge in a multi-cell radio frequency cavity

    SciTech Connect

    Popovic, S; Upadhyay, J; Mammosser, J; Nikolic, M; Vuskovic, L

    2014-11-07

    We are reporting experimental results on microwave discharge operating at resonant frequency in a multi-cell radio frequency (RF) accelerator cavity. Although the discharge operated at room temperature, the setup was constructed so that it could be used for plasma generation and processing in fully assembled active superconducting radio-frequency (SRF) cryomodule (in situ operation). This discharge offers an efficient mechanism for removal of a variety of contaminants, organic or oxide layers, and residual particulates from the interior surface of RF cavities through the interaction of plasma-generated radicals with the cavity walls. We describe resonant RF breakdown conditions and address the problems related to generation and sustaining the multi-cell cavity plasma, which are breakdown and resonant detuning. We have determined breakdown conditions in the cavity, which was acting as a plasma vessel with distorted cylindrical geometry. We discuss the spectroscopic data taken during plasma removal of contaminants and use them to evaluate plasma parameters, characterize the process, and estimate the volatile contaminant product removal.

  17. Thermal analysis of optical reference cavities for low sensitivity to environmental temperature fluctuations.

    PubMed

    Dai, Xiaojiao; Jiang, Yanyi; Hang, Chao; Bi, Zhiyi; Ma, Longsheng

    2015-02-23

    The temperature stability of optical reference cavities is significant in state-of-the-art ultra-stable narrow-linewidth laser systems. In this paper, the thermal time constant and thermal sensitivity of reference cavities are analyzed when reference cavities respond to environmental perturbations via heat transfer of thermal conduction and thermal radiation separately. The analysis as well as simulation results indicate that a reference cavity enclosed in multiple layers of thermal shields with larger mass, higher thermal capacity and lower emissivity is found to have a larger thermal time constant and thus a smaller sensitivity to environmental temperature perturbations. The design of thermal shields for reference cavities may vary according to experimentally achievable temperature stability and the coefficient of thermal expansion of reference cavities. A temperature fluctuation-induced length instability of reference cavities as low as 6 × 10(-16) on a day timescale can be achieved if a two-layer thermal shield is inserted between a cavity with the coefficient of thermal expansion of 1 × 10(-10) /K and an outer vacuum chamber with temperature fluctuation amplitude of 1 mK and period of 24 hours. PMID:25836547

  18. Absorption line metrology by optical feedback frequency-stabilized cavity ring-down spectroscopy

    NASA Astrophysics Data System (ADS)

    Burkart, Johannes; Kassi, Samir

    2015-04-01

    Optical feedback frequency-stabilized cavity ring-down spectroscopy (OFFS-CRDS) is a near-shot-noise-limited technique combining a sensitivity of with a highly linear frequency axis and sub-kHz resolution. Here, we give an in-depth review of the key elements of the experimental setup encompassing a highly stable V-shaped reference cavity, an integrated Mach-Zehnder modulator and a tightly locked ring-down cavity with a finesse of 450,000. Carrying out a detailed analysis of the spectrometer performance and its limitations, we revisit the photo-electron shot-noise limit in CRDS and discuss the impact of optical fringes. We demonstrate different active schemes for fringe cancelation by varying the phase of parasitic reflections. The proof-of-principle experiments reported here include a broadband high-resolution spectrum of carbon dioxide at 1.6 µm and an isolated line-shape measurement with a signal-to-noise ratio of 80,000. Beyond laboratory-based absorption line metrology for fundamental research, OFFS-CRDS holds a considerable potential for field laser measurements of trace gas concentrations and isotopic ratios by virtue of its small sample volume and footprint, the robust cavity-locking scheme and supreme precision.

  19. Use of a variable frequency source with a single-mode cavity to process ceramic filaments

    SciTech Connect

    Vogt, G.J.; Regan, A.H.; Rohlev, A.S.; Curtin, M.T.

    1995-09-01

    Rapid feedback control is needed for practical microwave processing of continuous ceramic oxide filaments to regulate the process temperature where the -dielectric properties of the filaments change rapidly with temperature. These dielectric changes can produce large rapid changes in the resonant frequency, the reflectivity, and the power density of the cavity. A broadband traveling wave tube (TWT) amplifier provides a highly versatile process control platform for filament processing. By comparing a RF signal from the cavity to a reference signal from the TWT, phase information can be used in a negative feedback loop to allow the oscillator to track the cavity frequency as it shifts due to the changing dielectric constant in the filaments being heated. By sampling the electric field level in the cavity with a detector, amplitude control can be done to maintain a constant absorbed power in a fiber tow, which is important for controlling the tow heating and temperature. This paper describes the design and testing of feedback controller with mullite rods in a single-mode TE{sub 10n} resonator driven by a commercial TWT.

  20. Birefringence-induced frequency beating in high-finesse cavities by continuous-wave cavity ring-down spectroscopy

    NASA Astrophysics Data System (ADS)

    Dupré, Patrick

    2015-11-01

    By analyzing the decaying intensity, leaking out a high-finesse cavity previously "filled" by a cw laser source (using the cavity ring-down spectroscopy technique), we observed frequency beating between what we think are two orthogonal eigenpolarization states of the intracavity electromagnetic field. The time decay (ring down) is analyzed by varying the angle of the polarization analyzer located in front of the detector. A full modeling of the observed signal is proposed. It is based on the Jones matrix formalism required for modeling the cavity behavior following a rotated phase shifter. The full transfer function is first established in the frequency domain, and then Fourier transformed to recover the temporal response. The same optical cavity, i.e., constituted of the same set of mirrors, is used at two different wavelengths (˜800 and ˜880 nm). It demonstrates the differences in behavior between a high-finesse cavity (˜400 000 ) and a lower finesse cavity (˜50 000 ). Beating frequency, characteristics time, and beat amplitude are mainly discussed versus the analyzer angle. A cavity birefringence of ˜1.6 ×10-5 rad, resulting from the mirror birefringence is suggested. If the current analysis is in agreement with pulsed CRDS experiments (polarimetry) obtained in an isotropic moderate-finesse cavity, it differs from a recent work report on a high-finesse cavity associated with a source mode locking [Phys. Rev. A 85, 013837 (2012), 10.1103/PhysRevA.85.013837].

  1. Three-Dimensional Electromagnetic High Frequency Axisymmetric Cavity Scars.

    SciTech Connect

    Warne, Larry K.; Jorgenson, Roy E.

    2014-10-01

    This report examines the localization of high frequency electromagnetic fi elds in three-dimensional axisymmetric cavities along periodic paths between opposing sides of the cavity. The cases where these orbits lead to unstable localized modes are known as scars. This report treats both the case where the opposing sides, or mirrors, are convex, where there are no interior foci, and the case where they are concave, leading to interior foci. The scalar problem is treated fi rst but the approximations required to treat the vector fi eld components are also examined. Particular att ention is focused on the normalization through the electromagnetic energy theorem. Both projections of the fi eld along the scarred orbit as well as point statistics are examined. Statistical comparisons are m ade with a numerical calculation of the scars run with an axisymmetric simulation. This axisymmetric cas eformstheoppositeextreme(wherethetwomirror radii at each end of the ray orbit are equal) from the two -dimensional solution examined previously (where one mirror radius is vastly di ff erent from the other). The enhancement of the fi eldontheorbitaxiscanbe larger here than in the two-dimensional case. Intentionally Left Blank

  2. Coherent Frequency Reference System for the NASA Deep Space Network

    NASA Technical Reports Server (NTRS)

    Tucker, Blake C.; Lauf, John E.; Hamell, Robert L.; Gonzaler, Jorge, Jr.; Diener, William A.; Tjoelker, Robert L.

    2010-01-01

    The NASA Deep Space Network (DSN) requires state-of-the-art frequency references that are derived and distributed from very stable atomic frequency standards. A new Frequency Reference System (FRS) and Frequency Reference Distribution System (FRD) have been developed, which together replace the previous Coherent Reference Generator System (CRG). The FRS and FRD each provide new capabilities that significantly improve operability and reliability. The FRS allows for selection and switching between frequency standards, a flywheel capability (to avoid interruptions when switching frequency standards), and a frequency synthesis system (to generate standardized 5-, 10-, and 100-MHz reference signals). The FRS is powered by redundant, specially filtered, and sustainable power systems and includes a monitor and control capability for station operations to interact and control the frequency-standard selection process. The FRD receives the standardized 5-, 10-, and 100-MHz reference signals and distributes signals to distribution amplifiers in a fan out fashion to dozens of DSN users that require the highly stable reference signals. The FRD is also powered by redundant, specially filtered, and sustainable power systems. The new DSN Frequency Distribution System, which consists of the FRS and FRD systems described here, is central to all operational activities of the NASA DSN. The frequency generation and distribution system provides ultra-stable, coherent, and very low phase-noise references at 5, l0, and 100 MHz to between 60 and 100 separate users at each Deep Space Communications Complex.

  3. High-Q toroidal cavities for high frequency klystrons.

    NASA Technical Reports Server (NTRS)

    Branch, G. M.

    1972-01-01

    A toroidal cavity developed for a 4-KW 12 GHz satellite-borne television transmitter klystron is described. The cavity has an internal Q 40% higher than that of a conventional cylindrical doubly reentrant cavity, thus yielding higher circuit efficiency and conserving energy which cannot be recovered in multistage depressed potential beam collectors. As a result of optimization studies with a digital computer program for obtaining cavity field distributions by a relaxation method and for computing the intrinsic cavity parameters, a particular cavity configuration with conical reentrant tunnel tips and toroidal walls is shown to provide good thermal characteristics and mechanical rigidity as well as low internal losses.

  4. Electron density and collision frequency of microwave resonant cavity produced discharges. [Progress report

    SciTech Connect

    McColl, W.; Brooks, C.; Brake, M.L.

    1992-12-31

    This progress report consists of an article, the abstract of which follows, and apparently the references and vita from a proposal. A review of perturbation diagnostics applied to microwave resonant cavity discharges is presented. The classical microwave perturbation technique examines the shift in the resonant frequency and cavity quality factor of the resonant cavity caused by low electron density discharges. However, modifications presented here allow the analysis to be applied to discharges with electron densities beyond the limit predicted by perturbation theory. An {open_quote}exact{close_quote} perturbation analysis is presented which models the discharge as a separate dielectric, thereby removing the restrictions on electron density imposed by the classical technique. The {open_quote}exact{close_quote} method also uses measurements of the shifts in the resonant conditions of the cavity. Thirdly, an electromagnetic analysis is presented which uses a characteristic equation, based upon Maxwell`s laws, and predicts the discharge conductivity based upon measurements of a complex axial wave number. By allowing the axial wave number of the electromagnetic fields to be complex, the fields are experimentally and theoretically shown to be spatially attenuated. The diagnostics are applied to continuous-wave microwave (2.45 GHz) discharges produced in an Asmussen resonant cavity. Double Langmuir probes, placed directly in the discharge at the point where the radial electric field is zero, act as a comparison with the analytic diagnostics. Microwave powers ranging from 30 to 100 watts produce helium and nitrogen discharges with pressures ranging from 0.5 to 6 torr. Analysis of the data predicts electron temperatures from 5 to 20 eV, electron densities from 10{sup 11} to 3 {times} 10{sup 12} cm{sup {minus}3}, and collision frequencies from 10{sup 9} to 10{sup 11} sec{sup {minus}1}.

  5. Laser nitriding for niobium superconducting radio-frequency accelerator cavities

    SciTech Connect

    Senthilraja Singaravelu, John Klopf, Gwyn Williams, Michael Kelley

    2010-10-01

    Particle accelerators are a key tool for scientific research ranging from fundamental studies of matter to analytical studies at light sources. Cost-forperformance is critical, both in terms of initial capital outlay and ongoing operating expense, especially for electricity. It depends on the niobium superconducting radiofrequency (SRF) accelerator cavities at the heart of most of these machines. Presently Nb SRF cavities operate near 1.9 K, well (and expensively) below the 4.2 K atmospheric boiling point of liquid He. Transforming the 40 nm thick active interior surface layer from Nb to delta NbN (Tc = 17 K instead of 9.2 K) appears to be a promising approach. Traditional furnace nitriding appears to have not been successful for this. Further, exposing a complete SRF cavity to the time-temperature history required for nitriding risks mechanical distortion. Gas laser nitriding instead has been applied successfully to other metals [P.Schaaf, Prog. Mat. Sci. 47 (2002) 1]. The beam dimensions and thermal diffusion length permit modeling in one dimension to predict the time course of the surface temperature for a range of per-pulse energy densities. As with the earlier work, we chose conditions just sufficient for boiling as a reference point. We used a Spectra Physics HIPPO nanosecond laser (l = 1064 nm, Emax= 0.392 mJ, beam spot@ 34 microns, PRF =15 – 30 kHz) to obtain an incident fluence of 1.73 - 2.15 J/cm2 for each laser pulse at the target. The target was a 50 mm diameter SRF-grade Nb disk maintained in a nitrogen atmosphere at a pressure of 550 – 625 torr and rotated at a constant speed of 9 rpm. The materials were examined by scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and x-ray diffraction (XRD). The SEM images show a sharp transition with fluence from a smooth, undulating topography to significant roughening, interpreted here as the onset of ablation. EPMA measurements of N/Nb atom ratio as a function of depth found a constant

  6. An iodine-based frequency reference for space applications

    NASA Astrophysics Data System (ADS)

    Schuldt, Thilo; Johann, Ulrich; Doeringshoff, Klaus; Kovalchuk, Evgeny; Peters, Achim; Braxmaier, Claus; Pahl, Julia; Stuehler, Johannes; Franz, Matthias

    We present the development of an iodine-based frequency reference for future potential applications in space, including the gravitational wave detector LISA/eLISA (Laser Interferometer Space Antenna), the mini SpaceTime Asymmetry Research (mSTAR) program, the aperture-synthesis telescope Darwin and the GRACE (Gravity Recovery and Climate Experiment) follow on mission/NGGM (Next Generation Gravity Mission) exploring Earth's gravity. Based on a state-of-the-art laboratory iodine frequency reference, setups on elegant breadboard (EBB) and engineering model (EM) level were realized, taking into account specific design criteria for space compatibility such as compactness and robustness. Both setups employ modulation transfer spectroscopy (MTS) in combination with balanced detection. They use a baseplate made of glass material in combination with a dedicated easy-to-handle assembly-integration technology (adhesive bonding) ensuring high pointing stability of the two counter-propagating laser beams in the iodine cell and therefore high long-term stability. The EBB setup utilizes a commercial off-the-shelf 30 cm long iodine cell in triple-pass configuration, the EM setup a specifically designed and manufactured compact iodine cell made of fused silica in a nine-pass configuration with a specific robust cold finger design. Both setups were characterized in beat measurements with a ULE cavity setup. Similar frequency stabilities of about 1*10 (-14) at an integration time of 1 s and below 5*10 (-15) at integration times between 10 s and 100 s were demonstrated. These values are comparable to the currently best laboratory setups. The EM setup was further subjected to environmental testing including thermal cycling and vibrational testing. Financial support by the German Space Agency DLR with funds provided by the Federal Ministry of Economics and Technology (BMWi) under grant numbers 50 QT 1102 and 50 QT 1201 is highly appreciated. The authors thank Jan Hrabina and Josef Lazar

  7. Reducing the linewidth of a diode laser below 30 Hz by stabilization to a reference cavity with a finesse above 10(5).

    PubMed

    Schoof, A; Grünert, J; Ritter, S; Hemmerich, A

    2001-10-15

    An extended-cavity diode laser operating in the Littrow configuration emitting near 657 nm is stabilized through its injection current to a reference cavity with a finesse of more than 10(5) and a corresponding resonance linewidth of 14 kHz. The laser linewidth is reduced from a few megahertz to a value below 30 Hz. The compact and robust setup appears ideal as a portable optical frequency standard that uses the calcium intercombination line. PMID:18049663

  8. Frequency stability of maser oscillators operated with cavity Q. [hydrogen and rubidium masers

    NASA Technical Reports Server (NTRS)

    Tetu, M.; Tremblay, P.; Lesage, P.; Petit, P.; Audoin, C.

    1982-01-01

    The short term frequency stability of masers equipped with an external feedback loop to increase the cavity quality factor was studied. The frequency stability of a hydrogen and a rubidium maser were measured and compared with theoretical evaluation. It is shown that the frequency stability passes through an optimum when the cavity Q is varied. Long term fluctuations are discussed and the optimum mid term frequency stability achievably by small size active and passive H-masers is considered.

  9. A water-filled radio frequency accelerating cavity

    SciTech Connect

    Faehl, R.J.; Keinigs, R.K.; Pogue, E.W.

    1998-12-31

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The objective of this project was to study water-filled resonant cavities as a high-energy density source to drive high-current accelerator configurations. Basic considerations lead to the expectation that a dielectric-filled cavity should be able to store up to e/e{sub o} as much energy as a vacuum one with the same dimensions and thus be capable of accelerating a proportionately larger amount of charge before cavity depletion occurs. During this project, we confirmed that water-filled cavities with e/e{sub o} = 60-80 did indeed behave with the expected characteristics, in terms of resonant TM modes and cavity Q. We accomplished this result with numerical cavity eigenvalue codes; fully electromagnetic, two-dimensional, particle-in-cell codes; and, most significantly, with scaled experiments performed in water-filled aluminum cavities. The low-power experiments showed excellent agreement with the numerical results. Simulations of the high-field, high-current mode of operation indicated that charged-particle loss on the dielectric windows, which separate the cavity from the beamline, must be carefully controlled to avoid significant distortion of the axial fields.

  10. Storage ring free electron laser dynamics in presence of an auxiliary harmonic radio frequency cavity

    NASA Astrophysics Data System (ADS)

    Thomas, C. A.; Botman, J. I. M.; Bruni, C.; Orlandi, G.; de Ninno, G.; Garzella, D.; Couprie, M. E.

    2005-01-01

    In a Storage Ring Free Electron Laser (SRFEL) there is a strong interdependence between the laser beam and the electron beam from which the laser is generated. The Super ACO storage ring has a second Radio Frequency (RF) cavity at the 5th harmonic of the main RF cavity. It is used to shorten the bunch length, thereby enhancing the laser gain. Employing this RF harmonic cavity instabilities are observed with a strong effect on both the laser radiation properties and the electron beam behaviour. In this paper, we first present beam characteristics of Super-ACO as influenced by the harmonic cavity, and the instabilities of the beam due to this RF cavity. Then we discuss the FEL properties in presence of the harmonic RF cavity. In general the harmonic cavity functions as intended, and it is observed that the laser suppresses the instabilities caused by the harmonic cavity in the absence of the FEL.

  11. Compact, low power radio frequency cavity for femtosecond electron microscopy

    SciTech Connect

    Lassise, A.; Mutsaers, P. H. A.; Luiten, O. J.

    2012-04-15

    Reported here is the design, construction, and characterization of a small, power efficient, tunable dielectric filled cavity for the creation of femtosecond electron bunches in an existing electron microscope without the mandatory use of femtosecond lasers. A 3 GHz pillbox cavity operating in the TM{sub 110} mode was specially designed for chopping the beam of a 30 keV scanning electron microscope. The dielectric material used is ZrTiO{sub 4}, chosen for the high relative permittivity ({epsilon}{sub r}= 37 at 10 GHz) and low loss tangent (tan {delta}= 2 x 10{sup -4}). This allows the cavity radius to be reduced by a factor of six, while the power consumption is reduced by an order of magnitude compared to a vacuum pillbox cavity. These features make this cavity ideal as a module for existing electron microscopes, and an alternative to femtosecond laser systems integrated with electron microscopes.

  12. Cavity-enhanced frequency up-conversion in rubidium vapor.

    PubMed

    Offer, Rachel F; Conway, Johnathan W C; Riis, Erling; Franke-Arnold, Sonja; Arnold, Aidan S

    2016-05-15

    We report the first use of a ring cavity to both enhance the output power and dramatically narrow the linewidth (<1  MHz) of blue light generated by four-wave mixing in a rubidium vapor cell. We find that the high output power available in our cavity-free system leads to power broadening of the generated blue light linewidth. Our ring cavity removes this limitation, allowing high output power and narrow linewidth to be achieved concurrently. As the cavity blue light is widely tunable over the Rb855S1/2F=3→6P3/2 transition, this narrow linewidth light would be suitable for near-resonant rubidium studies including, for example, second-stage laser cooling. PMID:27176956

  13. Cavity-enhanced frequency up-conversion in rubidium vapor

    NASA Astrophysics Data System (ADS)

    Offer, Rachel F.; Conway, Johnathan W. C.; Riis, Erling; Franke-Arnold, Sonja; Arnold, Aidan S.

    2016-05-01

    We report the first use of a ring cavity to both enhance the output power and dramatically narrow the linewidth ($<1\\,$MHz) of blue light generated by four wave mixing in a rubidium vapour cell. We find that the high output power available in our cavity-free system leads to power broadening of the generated blue light linewidth. Our ring cavity removes this limitation, allowing high output power and narrow linewidth to be achieved concurrently. As the cavity blue light is widely tunable over the $^{85}$Rb 5S$_{1/2} \\,\\,F=3$ $\\rightarrow$ 6P$_{3/2}$ transition, this narrow linewidth light would be suitable for second-stage laser cooling, which could be valuable for efficient $^{85}$Rb BEC production.

  14. Effect of laser frequency noise on fiber-optic frequency reference distribution

    NASA Technical Reports Server (NTRS)

    Logan, R. T., Jr.; Lutes, G. F.; Maleki, L.

    1989-01-01

    The effect of the linewidth of a single longitude-mode laser on the frequency stability of a frequency reference transmitted over a single-mode optical fiber is analyzed. The interaction of the random laser frequency deviations with the dispersion of the optical fiber is considered to determine theoretically the effect on the Allan deviation (square root of the Allan variance) of the transmitted frequency reference. It is shown that the magnitude of this effect may determine the limit of the ultimate stability possible for frequency reference transmission on optical fiber, but is not a serious limitation to present system performance.

  15. Qualification of niobium materials for superconducting radio frequency cavity applications: View of a condensed matter physicist

    SciTech Connect

    Roy, S. B.; Myneni, G. R.

    2015-12-04

    We address the issue of qualifications of the niobium materials to be used for superconducting radio frequency (SCRF) cavity fabrications, from the point of view of a condensed matter physicist/materials scientist. We focus on the particular materials properties of niobium required for the functioning a SCRF cavity, and how to optimize the same properties for the best SCRF cavity performance in a reproducible manner. In this way the niobium materials will not necessarily be characterized by their purity alone, but in terms of those materials properties, which will define the limit of the SCRF cavity performance and also other related material properties, which will help to sustain this best SCRF cavity performance. Furthermore we point out the need of standardization of the post fabrication processing of the niobium-SCRF cavities, which does not impair the optimized superconducting and thermal properties of the starting niobium-materials required for the reproducible performance of the SCRF cavities according to the design values.

  16. Sub-kilohertz linewidth narrowing of a mid-infrared optical parametric oscillator idler frequency by direct cavity stabilization.

    PubMed

    Ricciardi, I; Mosca, S; Parisi, M; Maddaloni, P; Santamaria, L; De Natale, P; De Rosa, M

    2015-10-15

    We stabilize the idler frequency of a singly resonant optical parametric oscillator directly to the resonance of a mid-infrared Fabry-Perot reference cavity. This is accomplished by the Pound-Drever-Hall locking scheme, controlling either the pump laser or the resonant signal frequency. A residual relative frequency noise power spectral density below 10(3)  Hz(2)/Hz is reached on average, with a Gaussian linewidth of 920 Hz over 100 ms, which reveals the potential for reaching spectral purity down to the hertz level by locking the optical parametric oscillator against a mid-infrared cavity with state-of-the-art superior performance. PMID:26469609

  17. Selective engineering of cavity resonance for frequency matching in optical parametric processes

    SciTech Connect

    Lu, Xiyuan; Rogers, Steven; Jiang, Wei C.; Lin, Qiang

    2014-10-13

    We propose to selectively engineer a single cavity resonance to achieve frequency matching for optical parametric processes in high-Q microresonators. For this purpose, we demonstrate an approach, selective mode splitting (SMS), to precisely shift a targeted cavity resonance, while leaving other cavity modes intact. We apply SMS to achieve efficient parametric generation via four-wave mixing in high-Q silicon microresonators. The proposed approach is of great potential for broad applications in integrated nonlinear photonics.

  18. Frequency up- and down-conversions in two-mode cavity quantum electrodynamics

    SciTech Connect

    Serra, R.M.; Villas-Boas, C.J.; Moussa, M.H.Y.; Almeida, N.G. de

    2005-04-01

    In this Brief Report we present a scheme for the implementation of frequency up- and down-conversion operations in two-mode cavity quantum electrodynamics (QED). This protocol for engineering bilinear two-mode interactions could enlarge perspectives for quantum-information manipulation and also be employed for fundamental tests of quantum theory in cavity QED. As an application we show how to generate a two-mode squeezed state in cavity QED (the original entangled state of Einstein, Podolsky, and Rosen)

  19. Mechanical design of SXLS (Superconducting X-ray Lithography Source) radio-frequency cavity

    SciTech Connect

    Mortazavi, P.; Sharma, S.; Keane, J.; Thomas, M.

    1989-01-01

    This paper presents the mechanical design of a Radio-Frequency (RF) cavity to be used on a compact storage ring for Superconducting X-ray Lithography Source (SXLS). Various design features of this cavity are discussed, including basic geometrical configuration, structural design, initial and operational tuning, vacuum multipactoring, power window, and damping of higher order modes. A second application of this cavity design for beam life extension in an existing storage ring is also described. 2 refs., 6 figs.

  20. Selective engineering of cavity resonance for frequency matching in optical parametric processes

    NASA Astrophysics Data System (ADS)

    Lu, Xiyuan; Rogers, Steven; Jiang, Wei C.; Lin, Qiang

    2014-10-01

    We propose to selectively engineer a single cavity resonance to achieve frequency matching for optical parametric processes in high-Q microresonators. For this purpose, we demonstrate an approach, selective mode splitting (SMS), to precisely shift a targeted cavity resonance, while leaving other cavity modes intact. We apply SMS to achieve efficient parametric generation via four-wave mixing in high-Q silicon microresonators. The proposed approach is of great potential for broad applications in integrated nonlinear photonics.

  1. Influence of frequency detunings and form of the initial field distribution on parametric generation of radiation in a dynamic cavity

    NASA Astrophysics Data System (ADS)

    Rosanov, N. N.; Fedorov, E. G.

    2016-05-01

    Characteristics of parametric generation of an electromagnetic field in a cavity with oscillating mirrors have been calculated as functions of the oscillation frequency detuning from the resonant frequency for different types of frequency dependence of the cavity mirror reflectance. The influence of the initial field distribution in the cavity on the parametric generation efficiency is demonstrated.

  2. Dual frequency optical carrier technique for transmission of reference frequencies in dispersive media

    NASA Technical Reports Server (NTRS)

    Maleki, Lutfollah (Inventor)

    1993-01-01

    Two different carrier frequencies modulated by a reference frequency are transmitted to each receiver to be synchronized therewith. Each receiver responds to local phase differences between the two received signals to correct the phase of one of them so as to maintain the corrected signal as a reliable synchronization reference.

  3. Resonance frequencies of a cavity containing a compressible viscous fluid

    NASA Astrophysics Data System (ADS)

    Conca, C.; Planchard, J.; Vanninathan, M.

    1993-03-01

    The aim of this paper is to study the resonance spectrum of a cavity containing a compressible viscous fluid. This system admits a discrete infinite sequence of eigenvalues whose real parts are negative, which is interpreted as the damping effect introduced by viscosity. Only a finite number of them have non-zero imaginary parts and this number depends on viscosity; a simple criterion is given for their position in the complex plane. The case of a cavity containing an elastic mechanical system immersed in the fluid is also examined; from a qualitative point of view, the nature of the resonance spectrum remains unchanged.

  4. Response of a store with tunable natural frequencies in compressible cavity flow

    SciTech Connect

    Wagner, Justin L.; Casper, Katya Marie; Beresh, Steven J.; Hunter, Patrick S.; Spillers, Russell Wayne; Henfling, John F.

    2015-01-07

    Fluid-structure interactions that occur during aircraft internal store carriage were experimentally explored at Mach 0.94 and 1.47 using a generic, aerodynamic store installed in a rectangular cavity having a length-to-depth ratio of 7. Similar to previous studies using a cylindrical store, the aerodynamic store responded to the cavity flow at its natural structural frequencies, and it exhibited a directionally dependent response to cavity resonance. Moreover, cavity tones excited the store in the streamwise and wall-normal directions consistently, whereas the spanwise response was much more limited.

  5. Stabilization of a laser on a large-detuned atomic-reference frequency by resonant interferometry

    NASA Astrophysics Data System (ADS)

    Barboza, Priscila M. T.; Nascimento, Guilherme G.; Araújo, Michelle O.; da Silva, Cícero M.; Cavalcante, Hugo L. D. de S.; Oriá, Marcos; Chevrollier, Martine; Passerat de Silans, Thierry

    2016-04-01

    We report a simple technique for stabilization of a laser frequency at the wings of an atomic resonance. The reference signal used for stabilization issues from interference effects obtained in a low-quality cavity filled with a resonant atomic vapour. For a frequency detuned 2.6 GHz from the 133Cs D2 6S{}1/2 F = 4 to 6P{}3/2 F’ = 5 transition, the fractional frequency Allan deviation is 10-8 for averaging times of 300 s, corresponding to a frequency deviation of 4 MHz. Adequate choice of the atomic density and of the cell thickness allows locking the laser at detunings larger than 10 GHz. Such a simple technique does not require magnetic fields or signal modulation.

  6. Cavity-Enhanced Frequency-Agile Rapid Scanning (fars) Spectroscopy: Experimental Realizations and Measurement Results

    NASA Astrophysics Data System (ADS)

    Long, David A.; Truong, Gar-Wing; Zee, Roger Van; Plusquellic, David F.; Hodges, Joseph T.

    2013-06-01

    We present a series of experimental realizations of cavity-enhanced, frequency-agile rapid scanning (FARS) spectroscopy using distributed feedback diode lasers, external cavity diode lasers, and ultra-narrow linewidth fiber lasers. FARS offers a scanning rate which is limited only by the cavity response time itself as well as a microwave-level frequency axis. Finally, it allows for an absorption sensitivity which is one of the highest ever reported. These realizations offer a range of applications from low-cost field measurements of trace gases to laboratory-based metrology.

  7. Enhanced terahertz source based on external cavity difference-frequency generation using monolithic single-frequency pulsed fiber lasers.

    PubMed

    Petersen, Eliot B; Shi, Wei; Nguyen, Dan T; Yao, Zhidong; Zong, Jie; Chavez-Pirson, Arturo; Peyghambarian, N

    2010-07-01

    We demonstrate a resonant external cavity approach to enhance narrowband terahertz radiation through difference-frequency generation for the first time (to our knowledge). Two nanosecond laser pulses resonant in an optical cavity interact with a nonlinear crystal to produce a factor of 7 enhancement of terahertz power compared to a single-pass orientation. This external enhancement approach shows promise to significantly increase both terahertz power and conversion efficiency through optical pump pulse enhancement and effective recycling. PMID:20596183

  8. Frequency-feedback tuning for single-cell cavity under rf heating

    SciTech Connect

    Stepp, J.D.; Bridges, J.F.

    1993-08-01

    A tuning system is described that is being used to match the source frequency of a high-power klystron on the resonant frequency of the prototype single-cell cavity for the 7-GeV Advance Photon Source (APS) storage ring. Typically a water-cooled piston tuner is required to adjust the reactive component of the cavity`s impedance to minimize reflected power back to the RF drive source. As the cavity watts expand due to RF heating, the resonant frequency decreases. Adjusting the source frequency to follow the cavity resonant frequency is a convenient method used to condition the cavity (for vacuum) at high power levels, in this case, 1 MV gap voltage at 100 kW power level. The tuning system consists of two coupling ports, a phase detector, a digitizing I/O system, and a DC coupled FM-modulated RF source. Proportional Integral Derivative (PID) loop parameters for the Experimental Physics and Industrial Control System (EPICS) software are calculated, and data is presented showing the damped response to peturbations on the loop. The timing system presented here does not need water-cooling, has no moving parts to wear out, and has an inherently faster response time. Its one limitation is the digitizing sampling rate. The only limitation in tuning range is the bandwidth of the RF source.

  9. Ultrastable reference frequency distribution utilizing a fiber optic link

    NASA Technical Reports Server (NTRS)

    Calhoun, Malcolm; Kuhnle, Paul

    1993-01-01

    The Frequency Standards Laboratory at the Jet Propulsion Laboratory (JPL) is responsible for the generation and distribution of ultra-stable reference frequency in NASA's Deep Space Network (DSN). Certain assemblies and components of the Radio Science and VLBI systems are located in the cones of tracking antennas hundreds of meters from the Frequency and Timing Subsystem's frequency standards. The very stringent requirements of these users challenge the performance of state-of-the-art frequency sources as well as the associated signal distribution system. The reference frequency distribution system described is designed around a low temperature coefficient of delay (TCD) optical fiber. On-site measurements of the fiber optic link alone indicate 100 MHz phase noise performance on the order of -120 dBc at 1 Hz from the carrier and Allan deviation on the order of parts in 10(exp 16) at 1000 seconds averaging time. The measured phase noise and stability of the link indicate that the performance characteristics of the hydrogen maser frequency standards are not degraded by the distribution system. Thus, optical fibers and electro-optic devices as distribution media appear to be a viable alternative to the classical coaxial cable distribution systems.

  10. Coupled modes, frequencies and fields of a dielectric resonator and a cavity using coupled mode theory

    NASA Astrophysics Data System (ADS)

    Elnaggar, Sameh Y.; Tervo, Richard; Mattar, Saba M.

    2014-01-01

    Probes consisting of a dielectric resonator (DR) inserted in a cavity are important integral components of electron paramagnetic resonance (EPR) spectrometers because of their high signal-to-noise ratio. This article studies the behavior of this system, based on the coupling between its dielectric and cavity modes. Coupled-mode theory (CMT) is used to determine the frequencies and electromagnetic fields of this coupled system. General expressions for the frequencies and field distributions are derived for both the resulting symmetric and anti-symmetric modes. These expressions are applicable to a wide range of frequencies (from MHz to THz). The coupling of cavities and DRs of various sizes and their resonant frequencies are studied in detail. Since the DR is situated within the cavity then the coupling between them is strong. In some cases the coupling coefficient, κ, is found to be as high as 0.4 even though the frequency difference between the uncoupled modes is large. This is directly attributed to the strong overlap between the fields of the uncoupled DR and cavity modes. In most cases, this improves the signal to noise ratio of the spectrometer. When the DR and the cavity have the same frequency, the coupled electromagnetic fields are found to contain equal contributions from the fields of the two uncoupled modes. This situation is ideal for the excitation of the probe through an iris on the cavity wall. To verify and validate the results, finite element simulations are carried out. This is achieved by simulating the coupling between a cylindrical cavity's TE011 and the dielectric insert's TE01δ modes. Coupling between the modes of higher order is also investigated and discussed. Based on CMT, closed form expressions for the fields of the coupled system are proposed. These expressions are crucial in the analysis of the probe's performance.

  11. Coupled modes, frequencies and fields of a dielectric resonator and a cavity using coupled mode theory.

    PubMed

    Elnaggar, Sameh Y; Tervo, Richard; Mattar, Saba M

    2014-01-01

    Probes consisting of a dielectric resonator (DR) inserted in a cavity are important integral components of electron paramagnetic resonance (EPR) spectrometers because of their high signal-to-noise ratio. This article studies the behavior of this system, based on the coupling between its dielectric and cavity modes. Coupled-mode theory (CMT) is used to determine the frequencies and electromagnetic fields of this coupled system. General expressions for the frequencies and field distributions are derived for both the resulting symmetric and anti-symmetric modes. These expressions are applicable to a wide range of frequencies (from MHz to THz). The coupling of cavities and DRs of various sizes and their resonant frequencies are studied in detail. Since the DR is situated within the cavity then the coupling between them is strong. In some cases the coupling coefficient, κ, is found to be as high as 0.4 even though the frequency difference between the uncoupled modes is large. This is directly attributed to the strong overlap between the fields of the uncoupled DR and cavity modes. In most cases, this improves the signal to noise ratio of the spectrometer. When the DR and the cavity have the same frequency, the coupled electromagnetic fields are found to contain equal contributions from the fields of the two uncoupled modes. This situation is ideal for the excitation of the probe through an iris on the cavity wall. To verify and validate the results, finite element simulations are carried out. This is achieved by simulating the coupling between a cylindrical cavity's TE011 and the dielectric insert's TE01δ modes. Coupling between the modes of higher order is also investigated and discussed. Based on CMT, closed form expressions for the fields of the coupled system are proposed. These expressions are crucial in the analysis of the probe's performance. PMID:24246950

  12. Characterization of Nb Superconducting Radio Frequency Cavities Based On In-Situ STEM And EELS

    NASA Astrophysics Data System (ADS)

    Tao, Runzhe

    Niobium, a 4d transition metal, has the highest superconducting transition temperature (Tc=9.2K) of any elemental superconductor as type II superconductor with coherent length, sigma approximately that of the penetration length, lambda. Pure niobium is grey in color and very soft, which makes this metal easily fabricable into different shapes for superconducting radio- frequency (SRF) cavities. Such cavities are used in some modern accelerators (SNS, CEBAF, XFEL), and are intended for usage in the next generation of particle accelerators, such as ILC. Since the crucial part of the cavities is top 100 nm of Nb near the inner cavity surface, considering the penetration depth is around 40 nm, it has attracted more and more attention in improving the surface process for optimizing the performance of the cavities. Nowadays, the main treatment of the Nb surface includes electro polishing (EP), buffered chemical polishing (BCP), high temperature baking (800 °C, 1000 °C and 1200 °C) and mild baking (120 °C). Firstly, the two half cells are welded together and the weld line is quite rough; there exists a lot of visible pits and defects on the inner shell of cavities. In this Ph.D. thesis, novel techniques in a scanning transmission electron microscope (STEM) that can be used to analyze the atomic scale structure-property relationship, both at room tem- perature and high/LN 2 temperature, are explored. Specifically, by using correlated Z-contrast imaging and electron energy loss spectrum (EELS), the structure, composition and bonding can be characterized directly on the atomic scale, also, light atoms, like H, O and C, are visible in ABF images. For the examining the defect behavior on the cavity surface, heating and cold stages are involved to simulate the baking treatment and low-temperature environments. These studies will serve as an important reference for qualifying different surface treatments to further improve SRF cavities' performance. The experimental results

  13. Fiber optic reference frequency distribution to remote beam waveguide antennas

    NASA Technical Reports Server (NTRS)

    Calhoun, Malcolm; Kuhnle, Paul; Law, Julius

    1995-01-01

    In the NASA/JPL Deep Space Network (DSN), radio science experiments (probing outer planet atmospheres, rings, gravitational waves, etc.) and very long-base interferometry (VLBI) require ultra-stable, low phase noise reference frequency signals at the user locations. Typical locations for radio science/VLBI exciters and down-converters are the cone areas of the 34 m high efficiency antennas or the 70 m antennas, located several hundred meters from the reference frequency standards. Over the past three years, fiber optic distribution links have replaced coaxial cable distribution for reference frequencies to these antenna sites. Optical fibers are the preferred medium for distribution because of their low attenuation, immunity to EMI/IWI, and temperature stability. A new network of Beam Waveguide (BWG) antennas presently under construction in the DSN requires hydrogen maser stability at tens of kilometers distance from the frequency standards central location. The topic of this paper is the design and implementation of an optical fiber distribution link which provides ultra-stable reference frequencies to users at a remote BWG antenna. The temperature profile from the earth's surface to a depth of six feet over a time period of six months was used to optimize the placement of the fiber optic cables. In-situ evaluation of the fiber optic link performance indicates Allan deviation on the order of parts in 10(exp -15) at 1000 and 10,000 seconds averaging time; thus, the link stability degradation due to environmental conditions still preserves hydrogen maser stability at the user locations. This paper reports on the implementation of optical fibers and electro-optic devices for distributing very stable, low phase noise reference signals to remote BWG antenna locations. Allan deviation and phase noise test results for a 16 km fiber optic distribution link are presented in the paper.

  14. Microwave frequency electromagnetic coupling to a thin membrane as one end of a cylindrical cavity

    NASA Astrophysics Data System (ADS)

    Castelli, Alessandro; Martinez, Luis; Speer, Jerry; Sharping, Jay; Chiao, Raymond

    2015-03-01

    We demonstrate coupling of an 11.1 GHz radio frequency (RF) TE011 cylindrical cavity mode to the mechanical motion of a silicon nitride (Si3N4) membrane. The membrane is driven into motion through radiation pressure forces arising from the transverse magnetic field present at the membrane boundary. We use a cylindrical aluminum cavity where one end consists of a 500-nm thick Si3N4 membrane that has been sputtered with 300 nm of niobium (Nb). Cavity frequency tuning is controlled via an aluminum plunger attached to a micrometer at the other end of the cavity. The membrane is driven into motion by modulating the amplitude of the RF signal at the membrane's resonant frequency in the KHz range. The membrane's displacement is measured by means of a Michelson interferometer. We compare results from experimental runs utilizing both square and circular membrane geometries. This experiment shows that the TE011 mode gives rise to radiation pressure on the ends of a cylindrical cavity and demonstrates the feasibility of future work using high Q superconducting RF cavities to realize a dynamical Casimir effect (DCE) due to the membrane's motion at GHz frequencies.

  15. Planar surface-micromachined pressure sensor with a sub-surface, embedded reference pressure cavity

    SciTech Connect

    Eaton, W.P.; Smith, J.H.

    1996-09-01

    Planar, surface micromachined pressure sensors have been fabricated by an extension of the chemical-mechanical polishing (CMP) process. CMP eliminates many of the fabrication problems associated with the photolithography, dry etch, and metallization of non-planar devices. Furthermore, CMP adds additional design flexibility. The sensors are based upon deformable, silicon nitride diaphragms with polysilicon piezoresistors. Absolute pressure is detected by virtue of reference pressure cavities underneath the diaphragms. Process details are discussed and characteristics from many devices are presented.

  16. Frequency dependence of the acoustic field generated from a spherical cavity transducer with open ends

    NASA Astrophysics Data System (ADS)

    Li, Faqi; Song, Dan; Zeng, Deping; Lin, Zhou; He, Min; Lei, Guangrong; Wu, Junru; Zhang, Dong; Wang, Zhibiao

    2015-12-01

    Resolution of high intensity focused ultrasound (HIFU) focusing is limited by the wave diffraction. We have developed a spherical cavity transducer with two open ends to improve the focusing precision without sacrificing the acoustic intensity (App Phys Lett 2013; 102: 204102). This work aims to theoretically and experimentally investigate the frequency dependence of the acoustic field generated from the spherical cavity transducer with two open ends. The device emits high intensity ultrasound at the frequency ranging from 420 to 470 kHz, and the acoustic field is measured by a fiber optic probe hydrophone. The measured results shows that the spherical cavity transducer provides high acoustic intensity for HIFU treatment only in its resonant modes, and a series of resonant frequencies can be choosen. Furthermore, a finite element model is developed to discuss the frequency dependence of the acoustic field. The numerical simulations coincide well with the measured results.

  17. Frequency dependence of the acoustic field generated from a spherical cavity transducer with open ends

    SciTech Connect

    Li, Faqi; Zeng, Deping; He, Min; Wang, Zhibiao E-mail: wangzhibiao@haifu.com.cn; Song, Dan; Lei, Guangrong; Lin, Zhou; Zhang, Dong E-mail: wangzhibiao@haifu.com.cn; Wu, Junru

    2015-12-15

    Resolution of high intensity focused ultrasound (HIFU) focusing is limited by the wave diffraction. We have developed a spherical cavity transducer with two open ends to improve the focusing precision without sacrificing the acoustic intensity (App Phys Lett 2013; 102: 204102). This work aims to theoretically and experimentally investigate the frequency dependence of the acoustic field generated from the spherical cavity transducer with two open ends. The device emits high intensity ultrasound at the frequency ranging from 420 to 470 kHz, and the acoustic field is measured by a fiber optic probe hydrophone. The measured results shows that the spherical cavity transducer provides high acoustic intensity for HIFU treatment only in its resonant modes, and a series of resonant frequencies can be choosen. Furthermore, a finite element model is developed to discuss the frequency dependence of the acoustic field. The numerical simulations coincide well with the measured results.

  18. Frequency response enhancement in integrated coupled-cavity DBR lasers.

    SciTech Connect

    Wendt, Joel Robert; Vawter, Gregory Allen; Tauke-Pedretti, Anna; Alford, Charles Fred; Skogen, Erik J.; Chow, Weng Wah; Cajas, Florante G.; Overberg, Mark E.; Torres, David L.; Yang, Zhenshan; Peake, Gregory Merwin

    2010-11-01

    We present a photonic integrated circuit (PIC) composed of two strongly coupled lasers. This PIC utilizes the dynamics of mutual injection locking to increase the relaxation resonance frequency from 3 GHz to beyond 30 GHz.

  19. Adaptive frequency comb illumination for interferometry in the case of nested two-beam cavities

    SciTech Connect

    Harder, Irina; Leuchs, Gerd; Mantel, Klaus; Schwider, Johannes

    2011-09-01

    The homogeneity test of glass plates in a Fizeau interferometer is hampered by the superposition of multiple interference signals coming from the surfaces of the glass plate as well as the empty Fizeau cavity. To evaluate interferograms resulting from such nested cavities, various approaches such as the use of broadband light sources have been applied. In this paper, we propose an adaptive frequency comb interferometer to accomplish the cavity selection. An adjustable Fabry-Perot resonator is used to generate a variable frequency comb that can be matched to the length of the desired cavity. Owing to its flexibility, the number of measurements needed for the homogeneity test can be reduced to four. Furthermore, compared to approaches using a two-beam interferometer as a filter for the broadband light source, the visibility of the fringe system is considerably higher if a Fabry-Perot filter is applied.

  20. Schemes for realizing frequency up- and down-conversions in two-mode cavity QED

    SciTech Connect

    Zou Xubo; Dong Yuli; Guo Guangcang

    2006-02-15

    We propose experimental schemes for realizing frequency up- and down-conversion in two-mode cavity QED by considering the atom-cavity interaction in the presence of a strong driving classical field. In contrast to the recent paper based on dispersive atom-cavity interaction [Serra et al., Phys. Rev. A 71, 045802 (2005)], our scheme is based on resonant interaction of the cavity modes with a single driven three-level atom, so that the quantum dynamics operates at a high speed, which is important in view of decoherence. It is shown that, with the help of a strong driving classical field, frequency up- and down-conversion operations can be realized by initially preparing the atom in a certain state.

  1. Frequency characterization of a swept- and fixed-wavelength external-cavity quantum cascade laser by use of a frequency comb.

    PubMed

    Knabe, Kevin; Williams, Paul A; Giorgetta, Fabrizio R; Armacost, Chris M; Crivello, Sam; Radunsky, Michael B; Newbury, Nathan R

    2012-05-21

    The instantaneous optical frequency of an external-cavity quantum cascade laser (QCL) is characterized by comparison to a near-infrared frequency comb. Fluctuations in the instantaneous optical frequency are analyzed to determine the frequency-noise power spectral density for the external-cavity QCL both during fixed-wavelength and swept-wavelength operation. The noise performance of a near-infrared external-cavity diode laser is measured for comparison. In addition to providing basic frequency metrology of external-cavity QCLs, this comb-calibrated swept QCL system can be applied to rapid, precise broadband spectroscopy in the mid-infrared spectral region. PMID:22714230

  2. Frequency measurement of the prototype storage ring stainless steel single cell cavity

    SciTech Connect

    Reisinger, E.A.

    1992-07-29

    Frequency measurements were made on the stainless steel single cell cavity after prototype storage ring at the Advanced Photon Source with various port terminations, using two small loops. The cavity contains six larger ports. The top and bottom ports have a diameter of 144 mm, the front and back ports (beam ports) have a diameter of 140 mm, and the two side ports have a diameter of 120 mm. The cavity also have four smaller ports of diameter 34.8 mm, which contain an E-probe, a H-loop, and two field probes.

  3. Semi-monolithic cavity for external resonant frequency doubling and method of performing the same

    NASA Technical Reports Server (NTRS)

    Hemmati, Hamid (Inventor)

    1999-01-01

    The fabrication of an optical cavity for use in a laser, in a frequency doubling external cavity, or any other type of nonlinear optical device, can be simplified by providing the nonlinear crystal in combination with a surrounding glass having an index of refraction substantially equal to that of the nonlinear crystal. The closed optical path in this cavity is formed in the surrounding glass and through the nonlinear crystal which lies in one of the optical segments of the light path. The light is transmitted through interfaces between the surrounding glass in the nonlinear crystal through interfaces which are formed at the Brewster-angle to minimize or eliminate reflection.

  4. Frequency-selection mechanism in incompressible open-cavity flows via reflected instability waves.

    PubMed

    Tuerke, F; Sciamarella, D; Pastur, L R; Lusseyran, F; Artana, G

    2015-01-01

    We present an alternative perspective on nonharmonic mode coexistence, commonly found in the shear layer spectrum of open-cavity flows. Modes obtained by a local linear stability analysis of perturbations to a two-dimensional, incompressible, and inviscid sheared flow over a cavity of finite length and depth were conditioned by a so-called coincidence condition first proposed by Kulikowskii [J. Appl. Math. Mech. 30, 180 (1966)] which takes into account instability wave reflection within the cavity. The analysis yields a set of discrete, nonharmonic frequencies, which compare well with experimental results [Phys. Fluids 20, 114101 (2008); Exp. Fluids 50, 905 (2010)]. PMID:25679706

  5. Cavity-Enhanced Frequency-Agile Rapid Scanning (fars) Spectroscopy: Measurement Principles

    NASA Astrophysics Data System (ADS)

    Hodges, Joseph T.; Long, David A.; Truong, Gar-Wing; Douglass, Kevin O.; Maxwell, Stephen E.; Zee, Roger Van; Plusquellic, David F.

    2013-06-01

    We present the principles of frequency-agile, rapid scanning (FARS) spectroscopy, a new technique for high-bandwidth, cavity-enhanced, laser absorption measurements. This method enables a visible or near-infrared probe laser beam to be frequency tuned over several tens of GHz using a microwave source, a waveguide phase modulator and a filter cavity. For the types of cavity-enhanced methods discussed here, the optical resonator itself is used to select a single sideband of the modulated laser spectrum, obviating the need for a separate filter cavity. FARS offers several important advantages over conventional cw laser tuning methods based on thermal or mechanical methods. These include, high speed tuning with sub-ms switching times, the ability to select arbitrary frequency steps or chirp rates, and the realization of a spectrum detuning axis with sub-kHz level precision. We discuss how FARS can be applied to cavity ring-down spectroscopy and other cavity-enhanced methods to enable rapid and accurate measurements of line parameters and to give noise-equivalent absorption coefficients at the 10^{-12} cm^{-1} Hz^{-1/2} level.

  6. Development of Ultra High Gradient and High Q{sub 0} Superconducting Radio Frequency Cavities

    SciTech Connect

    Geng, Rongli; Clemens, William A.; Follkie, James E.; Harris, Teena M.; Kushnick, Peter W.; Machie, Danny; Martin, Robert E.; Palczewski, Ari D.; Perry, Era A.; Slack, Gary L.; Williams, R. S.; Adolphsen, C.; Li, Z.; Hao, J. K.; Li, Y. M.; Liu, K. X.

    2013-06-01

    We report on the recent progress at Jefferson Lab in developing ultra high gradient and high Q{sub 0} superconducting radio frequency (SRF) cavities for future SRF based machines. A new 1300 MHz 9-cell prototype cavity is being fabricated. This cavity has an optimized shape in terms of the ratio of the peak surface field (both magnetic and electric) to the acceleration gradient, hence the name low surface field (LSF) shape. The goal of the effort is to demonstrate an acceleration gradient of 50 MV/m with Q{sub 0} of 10{sup 10} at 2 K in a 9-cell SRF cavity. Fine-grain niobium material is used. Conventional forming, machining and electron beam welding method are used for cavity fabrication. New techniques are adopted to ensure repeatable, accurate and inexpensive fabrication of components and the full assembly. The completed cavity is to be first mechanically polished to a mirror-finish, a newly acquired in-house capability at JLab, followed by the proven ILC-style processing recipe established already at JLab. In parallel, new single-cell cavities made from large-grain niobium material are made to further advance the cavity treatment and processing procedures, aiming for the demonstration of an acceleration gradient of 50 MV/m with Q{sub 0} of 2�10{sup 10} at 2K.

  7. Radio frequency accelerating cavity having slotted irises for damping certain electromagnetic modes

    DOEpatents

    Palmer, R.B.

    1991-05-21

    An accelerating cavity is disclosed having one or more iris structures mounted therein for strongly damping unwanted frequencies that are generated in the cavity by bunches of particles in a particle beam that is accelerated through the cavity during its operation. Each of the iris structures is characterized by containing a plurality of radial slots therein that extend from the central aperture through the iris member to the perimeter thereof. The outer end of each of the radial slots includes an enlarged portion that is effective to prevent undesired frequencies from being reflected back into the center aperture of the iris member. Waveguide means connect the outer ends of the radial slots to frequency damping means or to a dump or dumps. 17 figures.

  8. a New Broadband Cavity Enhanced Frequency Comb Spectroscopy Technique Using GHz Vernier Filtering.

    NASA Astrophysics Data System (ADS)

    Morville, Jérôme; Rutkowski, Lucile; Dobrev, Georgi; Crozet, Patrick

    2015-06-01

    We present a new approach to Cavity Enhanced - Direct Frequency Comb Spectroscopy where the full emission bandwidth of a Titanium:Sapphire laser is exploited at GHz resolution. The technique is based on a low-resolution Vernier filtering obtained with an appreciable -actively stabilized- mismatch between the cavity Free Spectral Range and the laser repetition rate, using a diffraction grating and a split-photodiode. This particular approach provides an immunity to frequency-amplitude noise conversion, reaching an absorption baseline noise in the 10-9 cm-1 range with a cavity finesse of only 3000. Spectra covering 1800 cm-1 (˜ 55 THz) are acquired in recording times of about 1 second, providing an absorption figure of merit of a few 10-11 cm-1/√{Hz}. Initially tested with ambient air, we report progress in using the Vernier frequency comb method with a discharge source of small radicals. Rutkowski et al, Opt. Lett., 39(23)2014

  9. Radio frequency accelerating cavity having slotted irises for damping certain electromagnetic modes

    DOEpatents

    Palmer, Robert B.

    1991-01-01

    An accelerating cavity having one or more iris structures mounted therein for strongly damping unwanted frequencies that are generated in the cavity by bunches of particles in a particle beam that is accelerated through the cavity during its operation. Each of the iris structures is characterized by containing a plurality of radial slots therein that extend from the central aperture through the iris member to the perimeter thereof. The outer end of each of the radial slots includes an enlarged portion that is effective to prevent undesired frequencies from being reflected back into the center aperture of the iris member. Waveguide means connect the outer ends of the radial slots to frequency damping means or to a dump or dumps.

  10. Frequency control in the process of a multicell superconducting cavity production

    NASA Astrophysics Data System (ADS)

    Shemelin, Valery; Carriere, Paul

    2012-04-01

    Modifications in the geometry of a superconducting RF cavity due to various processing procedures are presented in a convenient matrix formulation. Specifically, the effect of chemical etching, cooling down, and preloading are characterized, while the corresponding frequency shifts are calculated with a reliable software. This matrix method was used in the fabrication of the first cornell energy recovery linac (ERL) 7-cell cavity. Cavity fabrication can be broken down into three main stages: deep-drawing cups, welding the cups in pairs to obtain "dumbbells" and end groups, and, finally, welding the obtained components into a completed cavity. Frequency measurements and precise machining were implemented after the second stage. A custom RF fixture and data acquisition system were designed and validated for this purpose. The system comprised of a mechanical press with RF contacts, a network analyzer, a load cell and custom LABVIEW and MATLAB scripts. To extract the individual frequencies of the cups from these measurements, the established algorithm of calculations was analysed and corrected. Corrections for the ambient environment were also incorporated into the measurement protocol. Using the procedure presented, the frequency deviation of the completed 1.3 GHz 7-cell cavity was 360 kHz, corresponding to an average error about 75 μm in length for every cell.

  11. Plasma Parameters of SRF Cavities for Radio-Frequency Discharge Processing

    NASA Astrophysics Data System (ADS)

    Upadhyay, Janardan; Popovic, Svetozar; Vuskovic, Lepsha; Valente-Feliciano, Anne-Marie; Phillips, Larry

    2012-10-01

    Superconducting radio frequency (SRF) cavities of bulk Niobium are accelerating field-generating components of particle accelerators. Cavities are designed to support TM modes at a resonant frequency, which usually serve as their identifier. RF plasma surface modification dry-etching technology as an alternative to the currently existing wet etching technology requires a different RF coupling regime. The choice of power generator frequency greatly affects the field and plasma parameters distribution over the cavity. These are adjusted by a coaxial centerline antenna to provide for optimum level of plasma sheath uniformity. In the search for best etching conditions, we are opting for radio frequency (13.56 MHz, 100 MHz) and microwave frequency plasma (2.45 GHz) in Ar/Cl2 gas mixture. We have developed five optical probes for simultaneous spectroscopic measurements of the plasma properties at five points inside the cavity. The electron temperature and density measurement at the same set of points will be also measured with a Langmuir probe. The measurement of plasma parameters at different pressure and power for the chosen frequency set with varying chlorine content will be presented.

  12. Stabilized Fiber-Optic Distribution of Reference Frequency

    NASA Technical Reports Server (NTRS)

    Calhoun, Malcolm; Tjoelker, Robert; Diener, William; Dick, G. John; Wang, Rabi; Kirk, Albert

    2003-01-01

    An optoelectronic system distributes a reference signal of low noise and highly stabilized phase and frequency (100 MHz) from an atomic frequency standard to a remote facility at a distance up to tens of kilometers. The reference signal is transmitted to the remote station as amplitude modulation of an optical carrier signal propagating in an optical fiber. The stabilization scheme implemented in this system is intended particularly to suppress phase and frequency fluctuations caused by vibrations and by expansion and contraction of the optical fiber and other components in diurnal and seasonal heating and cooling cycles. The system (see figure) comprises several subsystems, the main one being (1) a hydrogen-maser or linear-ion-trap frequency standard in an environmentally controlled room in a signal-processing center (SPC), (2) a stabilized fiber-optic distribution assembly (SFODA), (3) a compensated sapphire oscillator (CSO) in an environmentally controlled room in the remote facility, (4) thermally stabilized distribution amplifiers and cabling from the environmentally controlled room to end users, and (5) performance- measuring equipment.

  13. Homodyne digital interferometry for a sensitive fiber frequency reference.

    PubMed

    Ngo, Silvie; McRae, Terry G; Gray, Malcolm B; Shaddock, Daniel A

    2014-07-28

    Digitally enhanced homodyne interferometry enables robust interferometric sensitivity to be achieved in an optically simple configuration by shifting optical complexity into the digital signal processing regime. We use digitally enhanced homodyne interferometry in a simple, all-fiber Michelson interferometer to achieve a frequency reference stability of better than 20 Hz/√Hz from 10 mHz to 1 Hz, satisfying, for the first time in an all fiber system, the stability requirements for the Gravity Recovery and Climate Experiment Follow On mission. In addition, we have demonstrated stability that satisfies the future mission objectives at frequencies down to 1 mHz. This frequency domain stability translates into a fractional Allan deviation of 3.3 × 10(-17) for an integration time of 55 seconds. PMID:25089435

  14. Computational imaging using a mode-mixing cavity at microwave frequencies

    SciTech Connect

    Fromenteze, Thomas; Decroze, Cyril; Carsenat, David; Yurduseven, Okan; Imani, Mohammadreza F.; Gollub, Jonah; Smith, David R.

    2015-05-11

    We present a 3D computational imaging system based on a mode-mixing cavity at microwave frequencies. The core component of this system is an electrically large rectangular cavity with one corner re-shaped to catalyze mode mixing, often called a Sinai Billiard. The front side of the cavity is perforated with a grid of periodic apertures that sample the cavity modes and project them into the imaging scene. The radiated fields are scattered by the scene and are measured by low gain probe antennas. The complex radiation patterns generated by the cavity thus encode the scene information onto a set of frequency modes. Assuming the first Born approximation for scattering dynamics, the received signal is processed using computational methods to reconstruct a 3D image of the scene with resolution determined by the diffraction limit. The proposed mode-mixing cavity is simple to fabricate, exhibits low losses, and can generate highly diverse measurement modes. The imaging system demonstrated in this letter can find application in security screening and medical diagnostic imaging.

  15. Hybrid Physical Chemical Vapor Deposition of Superconducting Magnesium Diboride Coatings for Large Scale Radio Frequency Cavities

    NASA Astrophysics Data System (ADS)

    Lee, Namhoon; Withanage, Wenura; Tan, Teng; Wolak, Matthaeus; Xi, Xiaoxing

    2016-03-01

    Magnesium diboride (MgB2) is considered to be a great candidate for next generation superconducting radio frequency (SRF) cavities due to its higher critical temperature Tc (40 K) and increased thermodynamic critical field Hc compared to other conventional superconductors. These properties significantly reduce the BCS surface resistance (RsBCS)and residual resistance (Rres) according to theoretical studies and suggest the possibility of an enhanced accelerating field (Eacc) . We have investigated the possibility of coating the inner surface of a 3 GHz SRF cavity with MgB2 by using a hybrid physical-vapor deposition (HPCVD) system which was modified for this purpose. To simulate a real 3 GHz SRF cavity, a stainless steel mock cavity has been employed for the study. The film quality was characterized on small substrates that were placed at selected locations within the cavity. MgB2 films on stainless steel foils, niobium pieces and SiC substrates showed transition temperatures of above 36 K. Dielectric resonance measurements resulted in promising Q values as obtained for the MgB2 films grown on the various substrates. By employing the HPCVD technique, a uniform film was achieved across the cavity interior, demonstrating the feasibility of HPCVD for MgB2 coatings for SRF cavities.

  16. A scalable multipass laser cavity based on injection by frequency conversion for noncollective Thomson scattering

    SciTech Connect

    Schaeffer, D. B.; Constantin, C. G.; Everson, E. T.; Van Compernolle, B.; Kugland, N. L.; Niemann, C.; Ebbers, C. A.; Glenzer, S. H.

    2010-10-15

    A scalable setup using injection by frequency conversion to establish a multipassing cavity for noncollective Thomson scattering on low density plasmas is presented. The cavity is shown to support >10 passes through the target volume with a 400% increase in energy on target versus a single-pass setup. Rayleigh scattering experiments were performed and demonstrate the viability of the cell to study low density plasmas of the order of 10{sup 12}-10{sup 13} cm{sup -3}. A high-repetition, low-energy, single-pass Thomson scattering setup was also performed on the University of California, Los Angeles Large Plasma Device and shows that the multipass cavity could have a significant advantage over the high-repetition approach due to the cavity setup's inherently higher signal per shot.

  17. A scalable multipass laser cavity based on injection by frequency conversion for noncollective Thomson scattering.

    PubMed

    Schaeffer, D B; Kugland, N L; Constantin, C G; Everson, E T; Van Compernolle, B; Ebbers, C A; Glenzer, S H; Niemann, C

    2010-10-01

    A scalable setup using injection by frequency conversion to establish a multipassing cavity for noncollective Thomson scattering on low density plasmas is presented. The cavity is shown to support >10 passes through the target volume with a 400% increase in energy on target versus a single-pass setup. Rayleigh scattering experiments were performed and demonstrate the viability of the cell to study low density plasmas of the order of 10(12)-10(13) cm(-3). A high-repetition, low-energy, single-pass Thomson scattering setup was also performed on the University of California, Los Angeles Large Plasma Device and shows that the multipass cavity could have a significant advantage over the high-repetition approach due to the cavity setup's inherently higher signal per shot. PMID:21033873

  18. High-frequency RCS of open cavities with rectangular and circular cross sections

    NASA Technical Reports Server (NTRS)

    Ling, Hao; Lee, Shung-Wu; Chou, Ri-Chee

    1989-01-01

    The radar cross-section (RCS) analysis of open-ended cavities with rectangular and circular cross sections is carried out using the waveguide modal approach and the shooting-and-bouncing ray (SBR) approach. For a cavity opening on the order of ten wavelengths or larger, the comparison between the two approaches is excellent. It is also observed that at lower frequencies the SBR results deviate from the more accurate modal results. On the other hand, the SBR approach allows for greater flexibility in geometrical modeling, and can be applied to problems where waveguide modes cannot be easily found. SBR results for an offset rectangular cavity and a circular cavity with rounded endplate are presented.

  19. Flux pinning characteristics in cylindrical ingot niobium used in superconducting radio frequency cavity fabrication

    SciTech Connect

    Dhavale Ashavai, Pashupati Dhakal, Anatolii A Polyanskii, Gianluigi Ciovati

    2012-04-01

    We present the results of from DC magnetization and penetration depth measurements of cylindrical bulk large-grain (LG) and fine-grain (FG) niobium samples used for the fabrication of superconducting radio frequency (SRF) cavities. The surface treatment consisted of electropolishing and low temperature baking as they are typically applied to SRF cavities. The magnetization data were fitted using a modified critical state model. The critical current density Jc and pinning force Fp are calculated from the magnetization data and their temperature dependence and field dependence are presented. The LG samples have lower critical current density and pinning force density compared to FG samples which implies a lower flux trapping efficiency. This effect may explain the lower values of residual resistance often observed in LG cavities than FG cavities.

  20. Superconducting magnesium diboride coatings for radio frequency cavities fabricated by hybrid physical-chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Wolak, M. A.; Tan, T.; Krick, A.; Johnson, E.; Hambe, M.; Chen, Ke; Xi, X. X.

    2014-01-01

    We have investigated the coating of an inner surface of superconducting radio frequency cavities with a magnesium diboride thin film by hybrid physical-chemical vapor deposition (HPCVD). To simulate a 6 GHz rf cavity, a straight stainless steel tube of 1.5-inch inner diameter and a dummy stainless steel cavity were employed, on which small sapphire and metal substrates were mounted at different locations. The MgB2 films on these substrates showed uniformly good superconducting properties including Tc of 37-40 K, residual resistivity ratio of up to 14, and root-mean-square roughness Rq of 20-30 nm. This work demonstrates the feasibility of coating the interior of cylindrical and curved objects with MgB2 by the HPCVD technique, an important step towards superconducting rf cavities with MgB2 coating.

  1. Fabry-Pérot filter cavities for wide-spaced frequency combs with large spectral bandwidth

    NASA Astrophysics Data System (ADS)

    Steinmetz, T.; Wilken, T.; Araujo-Hauck, C.; Holzwarth, R.; Hänsch, T. W.; Udem, T.

    2009-08-01

    We use low-finesse Fabry-Pérot cavities in series to generate frequency combs with a large mode spacing in a way that allows its application to a large optical bandwidth. The attenuation of laser modes closest to the pass bands of the cavity exceeds 70 dB for a filter ratio of m=20 relative to the resonant modes centered within the pass bands. We also identify the best cavity geometry to suppress spurious transmission of higher order transversal modes. Such a thinned out frequency comb can be used to calibrate traditional spectrographs for precision astronomy. In the time domain mode filtering generates a pulse train with a multiplied repetition rate. High-fidelity filtering, as described here, implies small variations of the pulse energies.

  2. Summary of performance of superconducting radio-frequency cavities built from CBMM niobium ingots

    SciTech Connect

    Ciovati, Gianluigi Dhakal, Pashupati Kneisel, Peter Myneni, Ganapati R.

    2015-12-04

    Several Nb ingots have been provided by CBMM to Jefferson Lab since 2004 as part of an R&D collaboration aimed at evaluating the performance of superconducting radio-frequency cavities built from ingots with different purity, as a results of different ingot production processes. Approximately 32 multi- and single-cell cavities with resonant frequency between ∼1.3-2.3 GHz were built, treated and tested at 2 K at Jefferson Lab between 2004 and 2014. The average peak surface field achieved in cavities made of RRR∼260 and RRR∼100-150 ingots was (119 ± 4) mT and (100 ± 8) mT, respectively. Higher quality factor values at 2.0 K have been measured in medium-purity, compared to higher purity material.

  3. Direct generation of optical frequency combs in χ(2) nonlinear cavities

    NASA Astrophysics Data System (ADS)

    Mosca, Simona; Ricciardi, Iolanda; Parisi, Maria; Maddaloni, Pasquale; Santamaria, Luigi; De Natale, Paolo; De Rosa, Maurizio

    2016-06-01

    Quadratic nonlinear processes are currently exploited for frequency comb transfer and extension from the visible and near infrared regions to other spectral ranges where direct comb generation cannot be accomplished. However, frequency comb generation has been directly observed in continuously pumped quadratic nonlinear crystals placed inside an optical cavity. At the same time, an introductory theoretical description of the phenomenon has been provided, showing a remarkable analogy with the dynamics of third-order Kerr microresonators. Here, we give an overview of our recent work on χ(2) frequency comb generation. Furthermore, we generalize the preliminary three-wave spectral model to a many-mode comb and present a stability analysis of different cavity field regimes. Although our work is a very early stage, it lays the groundwork for a novel class of highly efficient and versatile frequency comb synthesizers based on second-order nonlinear materials.

  4. Frequency-tunable transmon in a three-dimensional copper cavity

    NASA Astrophysics Data System (ADS)

    Pan, Jia-Zheng; Cao, Zhi-Min; Fan, Yun-Yi; Zhou, Yu; Lan, Dong; Liu, Yu-Hao; Chen, Zhi-Ping; Li, Yong-Chao; Cao, Chun-Hai; Xu, Wei-Wei; Kang, Lin; Chen, Jian; Yu, Hai-Feng; Yu, Yang; Sun, Guo-Zhu; Wu, Pei-Heng

    2015-11-01

    We have realized a frequency-tunable transmon in a three-dimensional cooper cavity using a direct current superconducting quantum interference device. Both the transition frequency of the transmon and the frequency of the dressed cavity can be varied with the applied external flux bias, which are well consistent with the theoretical model. The range of the variable transition frequency is from 5.188 GHz to 7.756 GHz. The energy relaxation time of the transmon is hundreds of nanoseconds. Project supported by the National Basic Research Program of China (Grant Nos. 2011CB922104 and 2011CBA00200), the National Natural Science Foundation of China (Grant No. 11474154), the Natural Science Foundation of Jiangsu Province, China (Grant No. BK2012013), the Priority Academic Program Development of Jiangsu Higher Education Institutions, China, the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120091110030), and the Dengfeng Project B of Nanjing University, China.

  5. Nonlinear frequency conversion using high-quality modes in GaAs nanobeam cavities.

    PubMed

    Buckley, Sonia; Radulaski, Marina; Zhang, Jingyuan Linda; Petykiewicz, Jan; Biermann, Klaus; Vučković, Jelena

    2014-10-01

    We demonstrate the design, fabrication, and characterization of nanobeam photonic crystal cavities in (111)-GaAs with multiple high-Q modes, with large frequency separations (up to 740 nm in experiment, i.e., a factor of 1.5 and up to an octave in theory). Such structures are crucial for efficient implementation of nonlinear frequency conversion. Here, we employ them to demonstrate sum-frequency generation from 1300 and 1950 nm to 780 nm. These wavelengths are particularly interesting for quantum frequency conversion between Si vacancy centers in diamond and the fiber-optic network. PMID:25360956

  6. Dual-etalon cavity ring-down frequency-comb spectroscopy with broad band light source

    DOEpatents

    Chandler, David W; Strecker, Kevin E

    2014-04-01

    In an embodiment, a dual-etalon cavity-ring-down frequency-comb spectrometer system is described. A broad band light source is split into two beams. One beam travels through a first etalon and a sample under test, while the other beam travels through a second etalon, and the two beams are recombined onto a single detector. If the free spectral ranges ("FSR") of the two etalons are not identical, the interference pattern at the detector will consist of a series of beat frequencies. By monitoring these beat frequencies, optical frequencies where light is absorbed may be determined.

  7. Diode laser frequency stabilization using a low cost, low finesse Fabry-Perot cavity

    NASA Astrophysics Data System (ADS)

    Hastings, Hannah; Jaber, Noura B.; Piatt, Georgia; Gregoric, Vincent C.; Carroll, Thomas J.; Noel, Michael W.

    2016-05-01

    Our lab employs low cost, low finesse Fabry-Perot cavities to stabilize the frequency of diode lasers used in ultra-cold Rydberg atom experiments. To characterize the stability of this technique, we perform a self-heterodyne linewidth measurement. For comparison, we also measure the linewidth when using a saturated absorption spectrometer to provide frequency stability. This work is supported by the National Science Foundation under Grants No. 1205895 and No. 1205897.

  8. Microwave induced plasma discharge in multi-cell superconducting radio-frequency cavity

    SciTech Connect

    Ahmed, Shahid; Mammosser, John D.

    2015-07-15

    A R&D effort for in situ cleaning of 1.5 GHz Superconducting Radio Frequency (SRF) cavities at room temperature using the plasma processing technique has been initiated at Jefferson Lab. This is a step toward the cleaning of cryomodules installed in the Continuous Electron Beam Accelerator Facility (CEBAF). For this purpose, we have developed an understanding of plasma discharge in a 5-cell CEBAF-type SRF cavity having configurations similar to those in the main accelerator. The focus of this study involves the detailed investigations of developing a plasma discharge inside the cavity volume and avoids the breakdown condition in the vicinity of the ceramic RF window. A plasma discharge of the gas mixture Ar–O{sub 2} (90%:10%) can be established inside the cavity volume by the excitation of a resonant 4π/5 TM{sub 010}-mode driven by a klystron. The absence of any external magnetic field for generating the plasma is suitable for cleaning cavities installed in a complex cryomodule assembly. The procedures developed in these experimental investigations can be applied to any complex cavity structure. Details of these experimental measurements and the observations are discussed in the paper.

  9. Superconducting radio-frequency cavities made from medium and low-purity niobium ingots

    NASA Astrophysics Data System (ADS)

    Ciovati, Gianluigi; Dhakal, Pashupati; Myneni, Ganapati R.

    2016-06-01

    Superconducting radio-frequency cavities made of ingot niobium with residual resistivity ratio (RRR) greater than 250 have proven to have similar or better performance than fine-grain Nb cavities of the same purity, after standard processing. The high purity requirement contributes to the high cost of the material. As superconducting accelerators operating in continuous-wave typically require cavities to operate at moderate accelerating gradients, using lower purity material could be advantageous not only to reduce cost but also to achieve higher Q 0-values. In this contribution we present the results from cryogenic RF tests of 1.3–1.5 GHz single-cell cavities made of ingot Nb of medium (RRR = 100–150) and low (RRR = 60) purity from different suppliers. Cavities made of medium-purity ingots routinely achieved peak surface magnetic field values greater than 70 mT with an average Q 0-value of 2 × 1010 at 2 K after standard processing treatments. The performances of cavities made of low-purity ingots were affected by significant pitting of the surface after chemical etching.

  10. Microwave induced plasma discharge in multi-cell superconducting radio-frequency cavity

    NASA Astrophysics Data System (ADS)

    Ahmed, Shahid; Mammosser, John D.

    2015-07-01

    A R&D effort for in situ cleaning of 1.5 GHz Superconducting Radio Frequency (SRF) cavities at room temperature using the plasma processing technique has been initiated at Jefferson Lab. This is a step toward the cleaning of cryomodules installed in the Continuous Electron Beam Accelerator Facility (CEBAF). For this purpose, we have developed an understanding of plasma discharge in a 5-cell CEBAF-type SRF cavity having configurations similar to those in the main accelerator. The focus of this study involves the detailed investigations of developing a plasma discharge inside the cavity volume and avoids the breakdown condition in the vicinity of the ceramic RF window. A plasma discharge of the gas mixture Ar-O2 (90%:10%) can be established inside the cavity volume by the excitation of a resonant 4π/5 TM010-mode driven by a klystron. The absence of any external magnetic field for generating the plasma is suitable for cleaning cavities installed in a complex cryomodule assembly. The procedures developed in these experimental investigations can be applied to any complex cavity structure. Details of these experimental measurements and the observations are discussed in the paper.

  11. Microwave induced plasma discharge in multi-cell superconducting radio-frequency cavity.

    PubMed

    Ahmed, Shahid; Mammosser, John D

    2015-07-01

    A R&D effort for in situ cleaning of 1.5 GHz Superconducting Radio Frequency (SRF) cavities at room temperature using the plasma processing technique has been initiated at Jefferson Lab. This is a step toward the cleaning of cryomodules installed in the Continuous Electron Beam Accelerator Facility (CEBAF). For this purpose, we have developed an understanding of plasma discharge in a 5-cell CEBAF-type SRF cavity having configurations similar to those in the main accelerator. The focus of this study involves the detailed investigations of developing a plasma discharge inside the cavity volume and avoids the breakdown condition in the vicinity of the ceramic RF window. A plasma discharge of the gas mixture Ar-O2 (90%:10%) can be established inside the cavity volume by the excitation of a resonant 4π/5 TM010-mode driven by a klystron. The absence of any external magnetic field for generating the plasma is suitable for cleaning cavities installed in a complex cryomodule assembly. The procedures developed in these experimental investigations can be applied to any complex cavity structure. Details of these experimental measurements and the observations are discussed in the paper. PMID:26233368

  12. Superconducting radio-frequency cavities made from medium and low-purity niobium ingots

    DOE PAGESBeta

    Ciovati, Gianluigi; Dhakal, Pashupati; Myneni, Ganapati R.

    2016-04-07

    Superconducting radio-frequency cavities made of ingot niobium with residual resistivity ratio (RRR) greater than 250 have proven to have similar or better performance than fine-grain Nb cavities of the same purity, after standard processing. The high purity requirement contributes to the high cost of the material. As superconducting accelerators operating in continuous-wave typically require cavities to operate at moderate accelerating gradients, using lower purity material could be advantageous not only to reduce cost but also to achieve higher Q0-values. In this contribution we present the results from cryogenic RF tests of 1.3–1.5 GHz single-cell cavities made of ingot Nb ofmore » medium (RRR = 100–150) and low (RRR = 60) purity from different suppliers. Cavities made of medium-purity ingots routinely achieved peak surface magnetic field values greater than 70 mT with an average Q0-value of 2 × 1010 at 2 K after standard processing treatments. As a result, the performances of cavities made of low-purity ingots were affected by significant pitting of the surface after chemical etching.« less

  13. Surface analyses of electropolished niobium samples for superconducting radio frequency cavity

    SciTech Connect

    Tyagi, P. V.; Nishiwaki, M.; Saeki, T.; Sawabe, M.; Hayano, H.; Noguchi, T.; Kato, S.

    2010-07-15

    The performance of superconducting radio frequency niobium cavities is sometimes limited by contaminations present on the cavity surface. In the recent years extensive research has been done to enhance the cavity performance by applying improved surface treatments such as mechanical grinding, electropolishing (EP), chemical polishing, tumbling, etc., followed by various rinsing methods such as ultrasonic pure water rinse, alcoholic rinse, high pressure water rinse, hydrogen per oxide rinse, etc. Although good cavity performance has been obtained lately by various post-EP cleaning methods, the detailed nature about the surface contaminants is still not fully characterized. Further efforts in this area are desired. Prior x-ray photoelectron spectroscopy (XPS) analyses of EPed niobium samples treated with fresh EP acid, demonstrated that the surfaces were covered mainly with the niobium oxide (Nb{sub 2}O{sub 5}) along with carbon, in addition a small quantity of sulfur and fluorine were also found in secondary ion mass spectroscopy (SIMS) analysis. In this article, the authors present the analyses of surface contaminations for a series of EPed niobium samples located at various positions of a single cell niobium cavity followed by ultrapure water rinsing as well as our endeavor to understand the aging effect of EP acid solution in terms of contaminations presence at the inner surface of the cavity with the help of surface analytical tools such as XPS, SIMS, and scanning electron microscope at KEK.

  14. High-frequency electromagnetic scarring in three-dimensional axisymmetric convex cavities

    DOE PAGESBeta

    Warne, Larry K.; Jorgenson, Roy E.

    2016-04-13

    Here, this article examines the localization of high-frequency electromagnetic fields in three-dimensional axisymmetric cavities along periodic paths between opposing sides of the cavity. When these orbits lead to unstable localized modes, they are known as scars. This article treats the case where the opposing sides, or mirrors, are convex. Particular attention is focused on the normalization through the electromagnetic energy theorem. Both projections of the field along the scarred orbit as well as field point statistics are examined. Statistical comparisons are made with a numerical calculation of the scars run with an axisymmetric simulation.

  15. Dual-pump Kerr Micro-cavity Optical Frequency Comb with varying FSR spacing

    PubMed Central

    Wang, Weiqiang; Chu, Sai T.; Little, Brent E.; Pasquazi, Alessia; Wang, Yishan; Wang, Leiran; Zhang, Wenfu; Wang, Lei; Hu, Xiaohong; Wang, Guoxi; Hu, Hui; Su, Yulong; Li, Feitao; Liu, Yuanshan; Zhao, Wei

    2016-01-01

    In this paper, we demonstrate a novel dual-pump approach to generate robust optical frequency comb with varying free spectral range (FSR) spacing in a CMOS-compatible high-Q micro-ring resonator (MRR). The frequency spacing of the comb can be tuned by an integer number FSR of the MRR freely in our dual-pump scheme. The dual pumps are self-oscillated in the laser cavity loop and their wavelengths can be tuned flexibly by programming the tunable filter embedded in the cavity. By tuning the pump wavelength, broadband OFC with the bandwidth of >180 nm and the frequency-spacing varying from 6 to 46-fold FSRs is realized at a low pump power. This approach could find potential and practical applications in many areas, such as optical metrology, optical communication, and signal processing systems, for its excellent flexibility and robustness. PMID:27338250

  16. Frequency-agile terahertz-wave parametric oscillator in a ring-cavity configuration

    NASA Astrophysics Data System (ADS)

    Minamide, Hiroaki; Ikari, Tomofumi; Ito, Hiromasa

    2009-12-01

    We demonstrate a frequency-agile terahertz wave parametric oscillator (TPO) in a ring-cavity configuration (ring-TPO). The TPO consists of three mirrors and a MgO:LiNbO3 crystal under noncollinear phase-matching conditions. A novel, fast frequency-tuning method was realized by controlling a mirror of the three-mirror ring cavity. The wide tuning range between 0.93 and 2.7 THz was accomplished. For first demonstration using the ring-TPO, terahertz spectroscopy was performed as the verification of the frequency-agile performance, measuring the transmission spectrum of the monosaccharide glucose. The spectrum was obtained within about 8 s in good comparison to those of Fourier transform infrared spectrometer.

  17. Dual-pump Kerr Micro-cavity Optical Frequency Comb with varying FSR spacing.

    PubMed

    Wang, Weiqiang; Chu, Sai T; Little, Brent E; Pasquazi, Alessia; Wang, Yishan; Wang, Leiran; Zhang, Wenfu; Wang, Lei; Hu, Xiaohong; Wang, Guoxi; Hu, Hui; Su, Yulong; Li, Feitao; Liu, Yuanshan; Zhao, Wei

    2016-01-01

    In this paper, we demonstrate a novel dual-pump approach to generate robust optical frequency comb with varying free spectral range (FSR) spacing in a CMOS-compatible high-Q micro-ring resonator (MRR). The frequency spacing of the comb can be tuned by an integer number FSR of the MRR freely in our dual-pump scheme. The dual pumps are self-oscillated in the laser cavity loop and their wavelengths can be tuned flexibly by programming the tunable filter embedded in the cavity. By tuning the pump wavelength, broadband OFC with the bandwidth of >180 nm and the frequency-spacing varying from 6 to 46-fold FSRs is realized at a low pump power. This approach could find potential and practical applications in many areas, such as optical metrology, optical communication, and signal processing systems, for its excellent flexibility and robustness. PMID:27338250

  18. Self-consistent modeling of terahertz waveguide and cavity with frequency-dependent conductivity

    SciTech Connect

    Huang, Y. J.; Chu, K. R.; Thumm, M.

    2015-01-15

    The surface resistance of metals, and hence the Ohmic dissipation per unit area, scales with the square root of the frequency of an incident electromagnetic wave. As is well recognized, this can lead to excessive wall losses at terahertz (THz) frequencies. On the other hand, high-frequency oscillatory motion of conduction electrons tends to mitigate the collisional damping. As a result, the classical theory predicts that metals behave more like a transparent medium at frequencies above the ultraviolet. Such a behavior difference is inherent in the AC conductivity, a frequency-dependent complex quantity commonly used to treat electromagnetics of metals at optical frequencies. The THz region falls in the gap between microwave and optical frequencies. However, metals are still commonly modeled by the DC conductivity in currently active vacuum electronics research aimed at the development of high-power THz sources (notably the gyrotron), although a small reduction of the DC conductivity due to surface roughness is sometimes included. In this study, we present a self-consistent modeling of the gyrotron interaction structures (a metallic waveguide or cavity) with the AC conductivity. The resulting waveguide attenuation constants and cavity quality factors are compared with those of the DC-conductivity model. The reduction in Ohmic losses under the AC-conductivity model is shown to be increasingly significant as the frequency reaches deeper into the THz region. Such effects are of considerable importance to THz gyrotrons for which the minimization of Ohmic losses constitutes a major design consideration.

  19. A digital frequency stabilization system of external cavity diode laser based on LabVIEW FPGA

    NASA Astrophysics Data System (ADS)

    Liu, Zhuohuan; Hu, Zhaohui; Qi, Lu; Wang, Tao

    2015-10-01

    Frequency stabilization for external cavity diode laser has played an important role in physics research. Many laser frequency locking solutions have been proposed by researchers. Traditionally, the locking process was accomplished by analog system, which has fast feedback control response speed. However, analog system is susceptible to the effects of environment. In order to improve the automation level and reliability of the frequency stabilization system, we take a grating-feedback external cavity diode laser as the laser source and set up a digital frequency stabilization system based on National Instrument's FPGA (NI FPGA). The system consists of a saturated absorption frequency stabilization of beam path, a differential photoelectric detector, a NI FPGA board and a host computer. Many functions, such as piezoelectric transducer (PZT) sweeping, atomic saturation absorption signal acquisition, signal peak identification, error signal obtaining and laser PZT voltage feedback controlling, are totally completed by LabVIEW FPGA program. Compared with the analog system, the system built by the logic gate circuits, performs stable and reliable. User interface programmed by LabVIEW is friendly. Besides, benefited from the characteristics of reconfiguration, the LabVIEW program is good at transplanting in other NI FPGA boards. Most of all, the system periodically checks the error signal. Once the abnormal error signal is detected, FPGA will restart frequency stabilization process without manual control. Through detecting the fluctuation of error signal of the atomic saturation absorption spectrum line in the frequency locking state, we can infer that the laser frequency stability can reach 1MHz.

  20. Absolute distance measurement by multi-heterodyne interferometry using a frequency comb and a cavity-stabilized tunable laser.

    PubMed

    Wu, Hanzhong; Zhang, Fumin; Liu, Tingyang; Balling, Petr; Qu, Xinghua

    2016-05-20

    In this paper, we develop a multi-heterodyne system capable of absolute distance measurement using a frequency comb and a tunable diode laser locked to a Fabry-Perot cavity. In a series of subsequent measurements, numerous beat components can be obtained by downconverting the optical frequency into the RF region with multi-heterodyne interferometry. The distances can be measured via the mode phases with a series of synthetic wavelengths. The comparison with the reference interferometer shows an agreement within 1.5 μm for the averages of five measurements and 2.5 μm for the single measurement, which is at the 10-8 relative precision level. PMID:27411152

  1. Frequency and intensity modulation characteristics of GaAs lasers in an external cavity

    SciTech Connect

    Carter, G.M.; Huang, Kao Yang . Dept. of Electrical Engineering); Brotman, J.; Grober, R.; Mandelberg, H. )

    1993-12-01

    Frequency and intensity modulation characteristics were measured for external cavity GaAs diode lasers as a function of modulation frequency. The data, displayed as a Chirp-to-Power (CPR) ratio, showed at low modulation frequencies a flat response and a zero or 180 degree relative phase depending on laser structure. A model incorporating a carrier density dependent imaginary part of the differential gain (Henry alpha factor) was developed to explain the data. The model yields simple scaling of the CPR with injection current and photon lifetime. The agreement between the model and data including scaling is excellent. These results provide strong evidence for transverse spatial hole burning'' in these lasers.

  2. Cavities

    MedlinePlus

    ... The tooth may hurt even without stimulation (spontaneous toothache). If irreversible damage to the pulp occurs and ... To detect cavities early, a dentist inquires about pain, examines the teeth, probes the teeth with dental instruments, and may take x-rays. People should ...

  3. An optical beam frequency reference with 10{sup -14} range frequency instability

    SciTech Connect

    McFerran, J. J.; Hartnett, J. G.; Luiten, A. N.

    2009-07-20

    The authors report on a thermal beam optical frequency reference with a fractional frequency instability of 9.2x10{sup -14} at 1 s reducing to 2.0x10{sup -14} at 64 s before slowly rising. The {sup 1}S{sub 0}{r_reversible}{sup 3}P{sub 1} intercombination line in neutral {sup 40}Ca is used as a frequency discriminator. A diode laser at 423 nm probes the ground state population after a Ramsey-Borde sequence of 657 nm light-field interactions on the atoms. The measured fractional frequency instability is an order of magnitude improvement on previously reported thermal beam optical clocks. The photon shot-noise of the read-out produces a limiting square root {lambda}-variance of 7x10{sup -14}/{radical}({tau})

  4. Strong Meissner screening change in superconducting radio frequency cavities due to mild baking

    SciTech Connect

    Romanenko, A. Grassellino, A.; Barkov, F.; Suter, A.; Salman, Z.; Prokscha, T.

    2014-02-17

    We investigate “hot” regions with anomalous high field dissipation in bulk niobium superconducting radio frequency cavities for particle accelerators by using low energy muon spin rotation (LE-μSR) on corresponding cavity cutouts. We demonstrate that superconducting properties at the hot region are well described by the non-local Pippard/BCS model for niobium in the clean limit with a London penetration depth λ{sub L}=23±2 nm. In contrast, a cutout sample from the 120 ∘C baked cavity shows a much larger λ>100 nm and a depth dependent mean free path, likely due to gradient in vacancy concentration. We suggest that these vacancies can efficiently trap hydrogen and hence prevent the formation of hydrides responsible for rf losses in hot regions.

  5. Strong Meissner screening change in superconducting radio frequency cavities due to mild baking

    NASA Astrophysics Data System (ADS)

    Romanenko, A.; Grassellino, A.; Barkov, F.; Suter, A.; Salman, Z.; Prokscha, T.

    2014-02-01

    We investigate "hot" regions with anomalous high field dissipation in bulk niobium superconducting radio frequency cavities for particle accelerators by using low energy muon spin rotation (LE-μSR) on corresponding cavity cutouts. We demonstrate that superconducting properties at the hot region are well described by the non-local Pippard/BCS model for niobium in the clean limit with a London penetration depth λL=23±2 nm. In contrast, a cutout sample from the 120 ∘C baked cavity shows a much larger λ >100 nm and a depth dependent mean free path, likely due to gradient in vacancy concentration. We suggest that these vacancies can efficiently trap hydrogen and hence prevent the formation of hydrides responsible for rf losses in hot regions.

  6. Characterization of etch pits found on a large-grain bulk niobium superconducting radio-frequency resonant cavity

    DOE PAGESBeta

    Zhao, Xin; Ciovati, G.; Bieler, T. R.

    2010-12-15

    The performance of superconducting radio-frequency (SRF) resonant cavities made of bulk niobium is limited by nonlinear localized effects. Surface analysis of regions of higher power dissipation is thus of intense interest. Such areas (referred to as “hotspots”) were identified in a large-grain single-cell cavity that had been buffered-chemical polished and dissected for examination by high resolution electron microscopy, electron backscattered diffraction microscopy (EBSD), and optical microscopy. Pits with clearly discernible crystal facets were observed in both “hotspot” and “coldspot” specimens. The pits were found in-grain, at bicrystal boundaries, and on tricrystal junctions. They are interpreted as etch pits induced bymore » crystal defects (e.g. dislocations). All coldspots examined had a qualitatively lower density of etch pits or relatively smooth tricrystal boundary junctions. EBSD mapping revealed the crystal orientation surrounding the pits. Locations with high pit density are correlated with higher mean values of the local average misorientation angle distributions, indicating a higher geometrically necessary dislocation content. In addition, a survey of the samples by energy dispersive x-ray analysis did not show any significant contamination of the samples’ surface. In conclusion, the local magnetic field enhancement produced by the sharp-edge features observed on the samples is not sufficient to explain the observed degradation of the cavity quality factor, which starts at peak surface magnetic field as low as 20 mT.« less

  7. Characterization of etch pits found on a large-grain bulk niobium superconducting radio-frequency resonant cavity

    SciTech Connect

    Zhao, Xin; Ciovati, G.; Bieler, T. R.

    2010-12-15

    The performance of superconducting radio-frequency (SRF) resonant cavities made of bulk niobium is limited by nonlinear localized effects. Surface analysis of regions of higher power dissipation is thus of intense interest. Such areas (referred to as “hotspots”) were identified in a large-grain single-cell cavity that had been buffered-chemical polished and dissected for examination by high resolution electron microscopy, electron backscattered diffraction microscopy (EBSD), and optical microscopy. Pits with clearly discernible crystal facets were observed in both “hotspot” and “coldspot” specimens. The pits were found in-grain, at bicrystal boundaries, and on tricrystal junctions. They are interpreted as etch pits induced by crystal defects (e.g. dislocations). All coldspots examined had a qualitatively lower density of etch pits or relatively smooth tricrystal boundary junctions. EBSD mapping revealed the crystal orientation surrounding the pits. Locations with high pit density are correlated with higher mean values of the local average misorientation angle distributions, indicating a higher geometrically necessary dislocation content. In addition, a survey of the samples by energy dispersive x-ray analysis did not show any significant contamination of the samples’ surface. In conclusion, the local magnetic field enhancement produced by the sharp-edge features observed on the samples is not sufficient to explain the observed degradation of the cavity quality factor, which starts at peak surface magnetic field as low as 20 mT.

  8. High-frequency asymptotic methods for analyzing the EM scattering by open-ended waveguide cavities

    NASA Technical Reports Server (NTRS)

    Burkholder, R. J.; Pathak, P. H.

    1989-01-01

    Four high-frequency methods are described for analyzing the electromagnetic (EM) scattering by electrically large open-ended cavities. They are: (1) a hybrid combination of waveguide modal analysis and high-frequency asymptotics, (2) geometrical optics (GO) ray shooting, (3) Gaussian beam (GB) shooting, and (4) the generalized ray expansion (GRE) method. The hybrid modal method gives very accurate results but is limited to cavities which are made up of sections of uniform waveguides for which the modal fields are known. The GO ray shooting method can be applied to much more arbitrary cavity geometries and can handle absorber treated interior walls, but it generally only predicts the major trends of the RCS pattern and not the details. Also, a very large number of rays need to be tracked for each new incidence angle. Like the GO ray shooting method, the GB shooting method can handle more arbitrary cavities, but it is much more efficient and generally more accurate than the GO method because it includes the fields diffracted by the rim at the open end which enter the cavity. However, due to beam divergence effects the GB method is limited to cavities which are not very long compared to their width. The GRE method overcomes the length-to-width limitation of the GB method by replacing the GB's with GO ray tubes which are launched in the same manner as the GB's to include the interior rim diffracted field. This method gives good accuracy and is generally more efficient than the GO method, but a large number of ray tubes needs to be tracked.

  9. High-frequency asymptotic methods for analyzing the EM scattering by open-ended waveguide cavities

    NASA Astrophysics Data System (ADS)

    Burkholder, R. J.; Pathak, P. H.

    1989-09-01

    Four high-frequency methods are described for analyzing the electromagnetic (EM) scattering by electrically large open-ended cavities. They are: (1) a hybrid combination of waveguide modal analysis and high-frequency asymptotics, (2) geometrical optics (GO) ray shooting, (3) Gaussian beam (GB) shooting, and (4) the generalized ray expansion (GRE) method. The hybrid modal method gives very accurate results but is limited to cavities which are made up of sections of uniform waveguides for which the modal fields are known. The GO ray shooting method can be applied to much more arbitrary cavity geometries and can handle absorber treated interior walls, but it generally only predicts the major trends of the RCS pattern and not the details. Also, a very large number of rays need to be tracked for each new incidence angle. Like the GO ray shooting method, the GB shooting method can handle more arbitrary cavities, but it is much more efficient and generally more accurate than the GO method because it includes the fields diffracted by the rim at the open end which enter the cavity. However, due to beam divergence effects the GB method is limited to cavities which are not very long compared to their width. The GRE method overcomes the length-to-width limitation of the GB method by replacing the GB's with GO ray tubes which are launched in the same manner as the GB's to include the interior rim diffracted field. This method gives good accuracy and is generally more efficient than the GO method, but a large number of ray tubes needs to be tracked.

  10. Green pulsed lidar-radar emitter based on a multipass frequency-shifting external cavity.

    PubMed

    Zhang, Haiyang; Brunel, Marc; Romanelli, Marco; Vallet, Marc

    2016-04-01

    This paper investigates the radio frequency (RF) up-conversion properties of a frequency-shifting external cavity on a laser beam. We consider an infrared passively Q-switched pulsed laser whose intensity modulation results from the multiple round-trips in the external cavity, which contains a frequency shifter. The output beam undergoes optical second-harmonic generation necessary to reach the green wavelength. We model the pulse train using a rate-equation model to simulate the laser pulses, together with a time-delayed interference calculation taking both the diffraction efficiency and the Gaussian beam propagation into account. The predictions are verified experimentally using a diode-pumped Nd:YAG laser passively Q-switched by Cr4+:YAG whose pulse train makes multiple round-trips in a mode-matched external cavity containing an acousto-optic frequency shifter driven at 85 MHz. Second-harmonic generation is realized in a KTP crystal, yielding RF-modulated pulses at 532 nm with a modulation contrast of almost 100%. RF harmonics up to the 6th order (1.020 GHz) are observed in the green output pulses. Such a RF-modulated green laser may find applications in underwater detection and ranging. PMID:27139644

  11. External-cavity frequency doubling of a 5-W 756-nm injection-locked Ti:sapphire laser.

    PubMed

    Cha, Yong-Ho; Ko, Kwang-Hoon; Lim, Gwon; Han, Jae-Min; Park, Hyun-Min; Kim, Taek-Soo; Jeong, Do-Young

    2008-03-31

    We have developed a 5-W 756-nm injection-locked Ti:sapphire laser and frequency-doubled it in an external enhancement cavity for the generation of watt-level 378-nm single-frequency radiation, which is essential for isotope-selective optical pumping of thallium atoms. With a lithium triborate (LBO) crystal in the enhancement cavity, 1.1 W at 378 nm was coupled out from the cavity. Such results are to our knowledge the highest powers of continuous-wave single-frequency radiation generated from a Ti:sapphire laser and its frequency doubling. PMID:18542585

  12. An improved coupling design for high-frequency TE011 electron paramagnetic resonance cavities

    NASA Astrophysics Data System (ADS)

    Savitsky, A.; Grishin, Yu.; Rakhmatullin, R.; Reijerse, E.; Lubitz, W.

    2013-01-01

    In high-frequency electron paramagnetic resonance (EPR) spectroscopy the sample is usually accommodated in a single-mode cylindrical TE011 microwave cavity. This cavity stands out in terms of flexibility for various types of EPR experiments due to convenient control of its resonance frequency and easy waveguide-to-cavity microwave coupling. In continuous wave and in pulsed EPR it is, however, essential to be able to vary the coupling efficiency over a large range. We present a new mechanical design to vary the microwave coupling to the cavity using a movable metal sphere. This coupling sphere is shifted in the plane of the iris wall inside the coupling waveguide. The design allows for a compact and robust construction of the EPR probehead that can be easily accommodated inside a limited space of helium flow cryostat. The construction details and characterization of the coupling element for 95 GHz (W-band) EPR as well as for 34 GHz (Q-band) are presented.

  13. Computer program for calculating the resonant frequency, shunt impedance and quality factor of a pill-box cavity in a storage ring. [CAVITY

    SciTech Connect

    Aguero, V.M.; Ng, K.Y.

    1983-10-01

    Keil and Zotter have analyzed the electromagnetic fields excited by the longitudinal density fluctuations of an unbunched relativistic particle beam drifting in a corrugated vacuum chamber of circular cross section. At higher frequencies, these corrugations become resonant cavities. Zotter has written a computer program known as KN7C to compute the resonant frequencies. However, in the actual use of KN7C, some difficulties are encountered. To surmount these difficulties, the program known as CAVITY was written to analyze this pill-box shaped resonant cavity. Although there are many input variables to this program, only two are essential and need to be specified. They are BD = b/d = the ratio of the circular beampipe radius to that of the pill-box cavity and GD = g/d where g is the length of the cavity. When they are specified, CAVITY will print out the dimensionless normalized fundamental resonant frequency FD, shunt impedance Z and figure of merit Q. From these, the actual resonant frequency, shunt impedance and figure of merit can be deduced. The program is described and a listing is provided.

  14. Frequency conversion in field stabilization system for application in SC cavity of linear accelerator

    NASA Astrophysics Data System (ADS)

    Filipek, Tomasz A.

    2005-09-01

    The paper concerns frequency conversion circuits of electromagnetic field stabilization system in superconductive cavity of linear accelerator. The stabilization system consists of digital part (based on FPGA) and analog part (frequency conversions, ADC/DAC, filters). Frequency conversion circuit is analyzed. The main problem in the frequency conversion for the stabilization system are: linearity of conversion and stability. Also, second order problems are subject of analysis: control of local oscillator parameters and fluctuation of actuated signal (exposing conversion). The following work was done: analysis of individual stage parameters on field stability and external influence, simulation. The work was closed with conclusions of the major frequency conversion parameters for field stabilization. The results have been applied for field stabilization system (RF Feedback System) in TESLA Test Facility 2 and preliminary research on X-Ray Free Electron Laser.

  15. Single-frequency blue light generation by single-pass sum-frequency generation in a coupled ring cavity tapered laser

    NASA Astrophysics Data System (ADS)

    Bjarlin Jensen, Ole; Michael Petersen, Paul

    2013-09-01

    A generic approach for generation of tunable single frequency light is presented. 340 mW of near diffraction limited, single-frequency, and tunable blue light around 459 nm is generated by sum-frequency generation (SFG) between two tunable tapered diode lasers. One diode laser is operated in a ring cavity and another tapered diode laser is single-passed through a nonlinear crystal which is contained in the coupled ring cavity. Using this method, the single-pass conversion efficiency is more than 25%. In contrast to SFG in an external cavity, the system is entirely self-stabilized with no electronic locking.

  16. Low temperature laser scanning microscopy of a superconducting radio-frequency cavity

    DOE PAGESBeta

    Ciovati, G.; Anlage, Steven M.; Baldwin, C.; Cheng, G.; Flood, R.; Jordan, K.; Kneisel, P.; Morrone, M.; Nemes, G.; Turlington, L.; et al

    2012-03-16

    An apparatus was created to obtain, for the first time, 2D maps of the surface resistance of the inner surface of an operating superconducting radio-frequency niobium cavity by a low-temperature laser scanning microscopy technique. This allows identifying non-uniformities of the surface resistance with a spatial resolution of about one order of magnitude better than with earlier methods. A signal-to-noise ratio of about 10 dB was obtained with 240 mW laser power and 1 Hz modulation frequency. The various components of the apparatus, the experimental procedure and results are discussed in details in this contribution.

  17. First-principles calculations of niobium hydride formation in superconducting radio-frequency cavities

    SciTech Connect

    Ford, Denise C.; Cooley, Lance D.; Seidman, David N.

    2013-09-01

    Niobium hydride is suspected to be a major contributor to degradation of the quality factor of niobium superconducting radio-frequency (SRF) cavities. In this study, we connect the fundamental properties of hydrogen in niobium to SRF cavity performance and processing. We modeled several of the niobium hydride phases relevant to SRF cavities and present their thermodynamic, electronic, and geometric properties determined from calculations based on density-functional theory. We find that the absorption of hydrogen from the gas phase into niobium is exothermic and hydrogen becomes somewhat anionic. The absorption of hydrogen by niobium lattice vacancies is strongly preferred over absorption into interstitial sites. A single vacancy can accommodate six hydrogen atoms in the symmetrically equivalent lowest-energy sites and additional hydrogen in the nearby interstitial sites affected by the strain field: this indicates that a vacancy can serve as a nucleation center for hydride phase formation. Small hydride precipitates may then occur near lattice vacancies upon cooling. Vacancy clusters and extended defects should also be enriched in hydrogen, potentially resulting in extended hydride phase regions upon cooling. We also assess the phase changes in the niobium-hydrogen system based on charge transfer between niobium and hydrogen, the strain field associated with interstitial hydrogen, and the geometry of the hydride phases. The results of this study stress the importance of not only the hydrogen content in niobium, but also the recovery state of niobium for the performance of SRF cavities.

  18. Advances in development of Nb3Sn superconducting radio-frequency cavities

    NASA Astrophysics Data System (ADS)

    Posen, Sam; Liepe, Matthias

    2014-11-01

    A 1.3 GHz Nb3Sn superconducting radio-frequency cavity prepared with a modified annealing step reached Bp k>50 mT , well above Bc 1=25 ±7 mT , without the strong Q -slope observed in previous Nb3Sn cavities. At 4.2 K, it has a Q0 of approximately 1 ×1 010 at >10 MV /m , far outperforming Nb at useable gradients. At 2 K, quench occurred at ˜55 mT , apparently due to a defect, so additional treatment may increase the maximum gradient. Material parameters of the coating were extracted from Q vs T data, including a Tc of 18.0 ±0.1 K , close to the maximum literature value. High power pulses were used to reach fields far higher than in CW measurements, and near Tc, quench fields close to the superheating field were observed. Based on a review of previous experience with Nb3Sn cavities, a speculative mechanism involving weak link grain boundaries is presented to explain how the modified annealing step could be the cause of the absence of strong Q -slope. Finally, an analysis of the progress to date provides hints that the path forward for Nb3Sn cavities should focus on minimizing defects.

  19. Study of Temperature Wave Propagation in Superfluid Helium Focusing on Radio-Frequency Cavity Cooling

    NASA Astrophysics Data System (ADS)

    Koettig, T.; Peters, B. J.; Avellino, S.; Junginger, T.; Bremer, J.

    2015-12-01

    Oscillating Superleak Transducers (OSTs) can be used to localize quenches of superconducting radio-frequency cavities. Local hot spots at the cavity surface initiate temperature waves in the surrounding superfluid helium that acts as cooling fluid at typical temperatures in the range of 1.6 K to 2 K. The temperature wave is characterised by the properties of superfluid helium such as the second sound velocity. For high heat load densities second sound velocities greater than the standard literature values are observed. This fast propagation has been verified in dedicated small scale experiments. Resistors were used to simulate the quench spots under controlled conditions. The three dimensional propagation of second sound is linked to OST signals. The aim of this study is to improve the understanding of the OST signal especially the incident angle dependency. The characterised OSTs are used as a tool for quench localisation on a real size cavity. Their sensitivity as well as the time resolution was proven to be superior to temperature sensors glued to the surface of the cavity.

  20. Frequency-doubling Gyro-amplifier using a TE Cluster Cavity

    NASA Astrophysics Data System (ADS)

    Granatstein, V.; Guo, H.; Miao, Y.; Nusinovich, G.; Rodgers, J.

    2001-10-01

    Frequency-doubling gyro-amplifier advantages include reduced driver frequency and simplified input coupler. The first gyro-amplifier with frequency doubling was a gyroklystron relevant to accelerator applications which had output of 32 MW at 19.8 GHz and 29% efficiency, but with bandwidth 0.1%.(W.Lawson et al, Phys. Rev. Lett.71, 456 (1993)) With an eye on radar applications requiring larger bandwidth albeit at lower power, a frequency-doubling gyro-TWT was recently studied; it had good phase stability, and 3% bandwidth but only 12% efficiency.(G. Nusinovich et al, IEEE Trans.ED-48, 1460 (2001); also, J.Rodgers et al, ibid.(to be published)) To improve efficiency while maintaining bandwidth at 3-5%, the circuit has been rebuilt to include a TE cluster cavity between input and output traveling wave sections.(H.Guo et al, Record of Pulsed Power Plasma Sci. 2001 Conf., p.520; also, Y.Miao et al, ibid. p. 514) We estimate improved bunching due to the cluster cavity will give efficiency 25% for 5% spread in axial electron velocity. Initial experimental results will be reported.

  1. Application of superconducting magnesium diboride (MGB2) in superconducting radio frequency cavities

    NASA Astrophysics Data System (ADS)

    Tan, Teng

    The superconductivity in magnesium diboride (MgB2) was discovered in 2001. As a BCS superconductor, MgB2 has a record-high Tc of 39 K, high Jc of > 107 A/cm2 and no weak link behavior across the grain boundary. All these superior properties endorsed that MgB2 would have great potential in both power applications and electronic devices. In the past 15 years, MgB2 based power cables, microwave devices, and commercial MRI machines emerged and the next frontier are superconducting radio frequency (SRF) cavities. SRF cavities are one of the leading accelerator technologies. In SRF cavities, applied microwave power generates electrical fields that accelerate particle beams. Compared with other accelerator techniques, SRF cavity accelerators feature low loss, high acceleration gradients and the ability to accelerate continuous particle beams. However, current SRF cavities are made from high-purity bulk niobium and work at 2 K in superfluid helium. The construction and operational cost of SRF cavity accelerators are very expensive. The demand for SRF cavity accelerators has been growing rapidly in the past decade. Therefore, a lot of effort has been devoted to the enhancement of the performance and the reduction of cost of SRF cavities. In 2010, an acceleration gradient of over 50 MV/m has been reported for a Nb-based SRF cavity. The magnetic field at the inner surface of such a cavity is ~ 1700 Oe, which is close to the thermodynamic critical field of Nb. Therefore, new materials and technologies are required to raise the acceleration gradient of future SRF cavity accelerators. Among all the proposed approaches, using MgB2 thin films to coat the inner surface of SRF cavities is one of the promising tactics with the potential to raise both the acceleration gradient and the operation temperature of SRF cavity accelerators. In this work, I present my study on MgB2 thin films for their application in SRF cavities. C-epitaxial MgB2 thin films grown on SiC(0001) substrates

  2. Effective index model predicts modal frequencies of vertical-cavity lasers

    SciTech Connect

    SERKLAND,DARWIN K.; HADLEY,G. RONALD; CHOQUETTE,KENT D.; GEIB,KENT M.; ALLERMAN,ANDREW A.

    2000-04-18

    Previously, an effective index optical model was introduced for the analysis of lateral waveguiding effects in vertical-cavity surface-emitting lasers. The authors show that the resultant transverse equation is almost identical to the one typically obtained in the analysis of dielectric waveguide problems, such as a step-index optical fiber. The solution to the transverse equation yields the lateral dependence of the optical field and, as is recognized in this paper, the discrete frequencies of the microcavity modes. As an example, they apply this technique to the analysis of vertical-cavity lasers that contain thin-oxide apertures. The model intuitively explains the experimental data and makes quantitative predictions in good agreement with a highly accurate numerical model.

  3. Frequency doubled femtosecond Ti:sapphire laser with an assisted enhancement cavity

    NASA Astrophysics Data System (ADS)

    Jin-Wei, Zhang; Hai-Nian, Han; Lei, Hou; Long, Zhang; Zi-Jiao, Yu; De-Hua, Li; Zhi-Yi, Wei

    2016-01-01

    We report an enhancement cavity for femtosecond Ti:sapphire laser at the repetition rate of 170 MHz. An enhancement factor of 24 is obtained when the injecting pulses have an average power of 1 W and a pulse duration of 80 fs. By placing a BBO crystal at the focus of the cavity, we obtain a 392-mW intracavity doubled-frequency laser, corresponding to a conversion efficiency of 43%. The output power has a long-term stability with a root mean square (RMS) of 0.036%. Project supported by the National Basic Research Program of China (Grant Nos. 2013CB922401 and 2012CB821304) and the National Natural Science Foundation of China (Grant No. 61378040).

  4. Intra-cavity frequency-doubled mode-locked semiconductor disk laser at 325 nm.

    PubMed

    Bek, Roman; Baumgärtner, Stefan; Sauter, Fabian; Kahle, Hermann; Schwarzbäck, Thomas; Jetter, Michael; Michler, Peter

    2015-07-27

    We present a passively mode-locked semiconductor disk laser (SDL) emitting at 650nm with intra-cavity second harmonic generation to the ultraviolet (UV) spectral range. Both the gain and the absorber structure contain InP quantum dots (QDs) as active material. In a v-shaped cavity using the semiconductor samples as end mirrors, a beta barium borate (BBO) crystal is placed in front of the semiconductor saturable absorber mirror (SESAM) for pulsed UV laser emission in one of the two outcoupled beams. Autocorrelation (AC) measurements at the fundamental wavelength reveal a FWHM pulse duration of 1.22ps. With a repetition frequency of 836MHz, the average output power is 10mW per beam for the red emission and 0.5mW at 325nm. PMID:26367654

  5. Surface Science Laboratory for Studying the Surfaces of Superconducting Radio Frequency Cavities

    SciTech Connect

    Andy Wu

    2003-09-01

    A Surface Science Laboratory (SSL) has been established at JLab to study surfaces relevant to superconducting radio frequency (SRF) cavities. Current operational facilities include a scanning electron microscope equipped with energy dispersive x-ray analysis, a secondary ion mass spectrometry, a metallographic optical microscope, a transmission electron microscope, a high precision and large scan area 3-D profilometer, a scanning field emission microscope, and a fully equipped sample preparation room. A scanning Auger microscope is being commissioned, and will be available for routine usage soon. Results from typical examples of the R&D projects on SRF cavities that were supported in the past through the use of the facilities in the SSL will be briefly reported.

  6. Experimental Demonstration of Frequency Autolocking an Optical Cavity Using a Time-Varying Kalman Filter

    NASA Astrophysics Data System (ADS)

    Schütte, Dirk; Hassen, S. Z. Sayed; Karvinen, Kai S.; Boyson, Toby K.; Kallapur, Abhijit G.; Song, Hongbin; Petersen, Ian R.; Huntington, Elanor H.; Heurs, Michèle

    2016-01-01

    We propose and demonstrate a new autolocking scheme using a three-mirror ring cavity consisting of a linear quadratic regulator and a time-varying Kalman filter. Our technique does not require a frequency scan to acquire resonance. We utilize the singular perturbation method to simplify our system dynamics and to permit the application of linear control techniques. The error signal combined with the transmitted power is used to estimate the cavity detuning. This estimate is used by a linear time-varying Kalman filter which enables the implementation of an optimal controller. The experimental results validate the controller design, and we demonstrate improved robustness to disturbances and a faster locking time than a traditional proportional-integral controller. More important, the time-varying Kalman filtering approach automatically reacquires lock for large detunings, where the error signal leaves its linear capture range, a feat which linear time-invariant controllers cannot achieve.

  7. Frequency locking of an optical cavity using linear-quadratic Gaussian integral control

    NASA Astrophysics Data System (ADS)

    Sayed Hassen, S. Z.; Heurs, M.; Huntington, E. H.; Petersen, I. R.; James, M. R.

    2009-09-01

    We show that a systematic modern control technique such as linear-quadratic Gaussian (LQG) control can be applied to a problem in experimental quantum optics which has previously been addressed using traditional approaches to controller design. An LQG controller which includes integral action is synthesized to stabilize the frequency of the cavity to the laser frequency and to reject low frequency noise. The controller is successfully implemented in the laboratory using a dSpace digital signal processing board. One important advantage of the LQG technique is that it can be extended in a straightforward way to control systems with multiple measurements and multiple feedback loops. This work is expected to pave the way for extremely stable lasers with fluctuations approaching the quantum noise limit and which could be potentially used in a wide range of applications.

  8. Fibers and combs: weaving a portable frequency reference in the near-IR

    NASA Astrophysics Data System (ADS)

    Corwin, Kristan

    2009-05-01

    Ten years after the advent of femtosecond optical frequency combs, they are now used for many applications. Here, we use near infrared combs to characterize and develop portable frequency references based on gas-filled hollow optical fibers. We explore the accuracy and stability of saturated absorption features in acetylene gas confined inside both 10 micron core diameter photonic bandgap fibers and ˜60 micron core diameter kagome-structured photonic crystal fibers. A cw fiber laser referenced to these features has resulted in stabilities of ˜10-11 in 1 s, competitive with iodine-stabilized HeNe lasers. Most of these studies have been performed using a femtosecond fiber laser that relies on a carbon nanotube saturable absorber. However, we have also explored Cr:forsterite femtosecond lasers with intracavity prisms, which reveal dramatic narrowing of the carrier-envelope offset beat when a knife edge is inserted in the cavity. Such observations and subsequent noise dynamics studies will lead to a better understanding of noise in these solid state combs, making Cr:forsterite laser combs more competitive for spectroscopy and other applications.

  9. Experimental Investigation on Electromagnetic Attenuation by Low Pressure Radio-Frequency Plasma for Cavity Structure

    NASA Astrophysics Data System (ADS)

    He, Xiang; Zhang, Yachun; Chen, Jianping; Chen, Yudong; Zeng, Xiaojun; Yao, Hong; Tang, Chunmei

    2016-01-01

    This paper reports on an experiment designed to test electromagnetic (EM) attenuation by radio-frequency (RF) plasma for cavity structures. A plasma reactor, in the shape of a hollow cylinder, filled with argon gas at low pressure, driven by a RF power source, was produced by wave-transmitting material. The detailed attenuations of EM waves were investigated under different conditions: the incident frequency is 1-4 GHz, the RF power supply is 13.56 MHz and 1.6-3 kW, and the argon pressure is 75-200 Pa. The experimental results indicate that 5-15 dB return loss can be obtained. From a first estimation, the electron density in the experiment is approximately (1.5-2.2) × 1016 m-3 and the collision frequency is about 11-30 GHz. The return loss of EM waves was calculated using a finite-difference time-domain (FDTD) method and it was found that it has a similar development with measurement. It can be confirmed that RF plasma is useful in the stealth of cavity structures such as jet-engine inlet. supported by National Natural Science Foundation of China (No. 51107033) and the Fundamental Research Funds for the Central Universities of China (No. 2013B33614)

  10. Production of Seamless Superconducting Radio Frequency Cavities from Ultra-fine Grained Niobium, Phase II Final Report

    SciTech Connect

    Roy Crooks, Ph.D., P.E.

    2009-10-31

    The positron and electron linacs of the International Linear Collider (ILC) will require over 14,000, nine-cell, one meter length, superconducting radio frequency (SRF) cavities [ILC Reference Design Report, 2007]. Manufacturing on this scale will benefit from more efficient fabrication methods. The current methods of fabricating SRF cavities involve deep drawing of the halves of each of the elliptical cells and joining them by high-vacuum, electron beam welding, with at least 19 circumferential welds per cavity. The welding is costly and has undesirable effects on the cavity surfaces, including grain-scale surface roughening at the weld seams. Hydroforming of seamless tubes avoids welding, but hydroforming of coarse-grained seamless tubes results in strain-induced surface roughening. Surface roughness limits accelerating fields, because asperities prematurely exceed the critical magnetic field and become normal conducting. This project explored the technical and economic feasibility of an improved processing method for seamless tubes for hydroforming. Severe deformation of bulk material was first used to produce a fine structure, followed by extrusion and flow-forming methods of tube making. Extrusion of the randomly oriented, fine-grained bulk material proceeded under largely steady-state conditions, and resulted in a uniform structure, which was found to be finer and more crystallographically random than standard (high purity) RRR niobium sheet metal. A 165 mm diameter billet of RRR grade niobium was processed into five, 150 mm I.D. tubes, each over 1.8 m in length, to meet the dimensions used by the DESY ILC hydroforming machine. Mechanical properties met specifications. Costs of prototype tube production were approximately twice the price of RRR niobium sheet, and are expected to be comparable with economies of scale. Hydroforming and superconducting testing will be pursued in subsequent collaborations with DESY and Fermilab. SRF Cavities are used to construct

  11. Laser Processing on the Surface of Niobium Superconducting Radio-Frequency Accelerator Cavities

    NASA Astrophysics Data System (ADS)

    Singaravelu, Senthilraja; Klopf, Michael; Krafft, Geoffrey; Kelley, Michael

    2011-03-01

    Superconducting Radio frequency (SRF) niobium cavities are at the heart of an increasing number of particle accelerators.~ Their performance is dominated by a several nm thick layer at the interior surface. ~Maximizing its smoothness is found to be critical and aggressive chemical treatments are employed to this end.~ We describe laser-induced surface melting as an alternative ``greener'' approach.~ Modeling guided selection of parameters for irradiation with a Q-switched Nd:YAG laser.~ The resulting topography was examined by SEM, AFM and Stylus Profilometry.

  12. Widely tunable terahertz source based on intra-cavity frequency mixing in quantum cascade laser arrays

    SciTech Connect

    Jiang, Aiting; Jung, Seungyong; Jiang, Yifan; Kim, Jae Hyun; Belkin, Mikhail A.; Vijayraghavan, Karun

    2015-06-29

    We demonstrate a compact monolithic terahertz source continuously tunable from 1.9 THz to 3.9 THz with the maximum peak power output of 106 μW at 3.46 THz at room temperature. The source consists of an array of 10 electrically tunable quantum cascade lasers with intra-cavity terahertz difference-frequency generation. To increase fabrication yield and achieve high THz peak power output in our devices, a dual-section current pumping scheme is implemented using two electrically isolated grating sections to independently control gain for the two mid-IR pumps.

  13. Frequency tuning of polarization oscillations in spin-polarized vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Lindemann, Markus; Pusch, Tobias; Michalzik, Rainer; Gerhardt, Nils C.; Hofmann, Martin R.

    2016-04-01

    Controlling the coupled spin-photon dynamics in vertical-cavity surface-emitting lasers (VCSELs) is an attractive opportunity to overcome the limitations of conventional, purely charge based semiconductor lasers. Such spin-controlled VCSELs (spin-VCSELs) offer several advantages, like reduced threshold, spin amplification and polarization control. Furthermore the coupling between carrier spin and light polarization bears the potential for ultrafast polarization dynamics. By injecting spin-polarized carriers, the complex polarization dynamics can be controlled and utilized for high-speed applications. Polarization oscillations as resonance oscillations of the coupled spin- photon system can be generated using pulsed spin injection, which can be much faster than the intensity dynamics in conventional devices. We already demonstrated that the oscillations can be switched in a controlled manner. These controllable polarization dynamics can be used for ultrafast polarization-based optical data communication. The polarization oscillation frequency and therefore the possible data transmission rate is assumed to be mainly determined by the birefringence-induced mode-splitting. This provides a direct tool to increase the polarization dynamics toward higher frequencies by adding a high amount of birefringence to the VCSEL structure. Using this technique, we could recently demonstrate experimentally a birefringence splitting of more than 250 GHz using mechanical strain. Here, we employ the well-known spin-flip model to investigate the tuning of the polarization oscillation frequency. The changing mechanical strain is represented by a linear birefringence sweep to values up to 80πGHz. The wide tuning range presented enables us to generate polarization oscillation frequencies exceeding the conventional intensity modulation frequency in the simulated device by far, mainly dependent on the birefringence in the cavity only.

  14. A novel approach to characterizing the surface topography of niobium superconducting radio frequency (SRF) accelerator cavities

    SciTech Connect

    Hui Tian, Guilhem Ribeill, Chen Xu, Charles E. Reece, Michael J. Kelley

    2011-03-01

    As superconducting niobium radio-frequency (SRF) cavities approach fundamental material limits, there is increased interest in understanding the details of topographical influences on realized performance limitations. Micro- and nano-roughness are implicated in both direct geometrical field enhancements as well as complications of the composition of the 50 nm surface layer in which the super-currents typically flow. Interior surface chemical treatments such as buffered chemical polishing (BCP) and electropolishing (EP) used to remove mechanical damage leave surface topography, including pits and protrusions of varying sharpness. These may promote RF magnetic field entry, locally quenching superconductivity, so as to degrade cavity performance. A more incisive analysis of surface topography than the widely used average roughness is needed. In this study, a power spectral density (PSD) approach based on Fourier analysis of surface topography data acquired by both stylus profilometry and atomic force microscopy (AFM) is introduced to distinguish the scale-dependent smoothing effects, resulting in a novel qualitative and quantitative description of Nb surface topography. The topographical evolution of the Nb surface as a function of different steps of well-controlled EP is discussed. This study will greatly help to identify optimum EP parameter sets for controlled and reproducible surface levelling of Nb for cavity production.

  15. Beam uniformization and low frequency RF cavities in compact electron storage rings

    NASA Astrophysics Data System (ADS)

    Pham, Alfonse N.

    An electron storage ring is currently under construction at Indiana University for extreme environment radiation effects experiments, x-ray production, and particle beam dynamics experiments. For an electron bunch to be successfully stored for long durations, a radio-frequency (RF) resonant structure will be used to provide an adequate RF bucket for longitudinal focusing and replenishment of energy electrons loses via synchrotron radiation. Due to beam line space limitation that are inherent to compact circular particle accelerators, a unique ferrite-loaded quarter-wave RF resonant cavity has been designed and constructed for use in the electron storage ring. The physics of particle accelerators and beams, ferrite-loaded RF resonant cavity theory, and results of the Poisson-SUPERFISH electromagnetic field simulations that were used to guide the specification and design of the RF cavity will be presented. Low-power resonant cavity characterization measurements were used to benchmark the performance of the RF cavity. High-power characterization and measurements with electron beams will be used to validate the performance of the cavity in the electron storage ring. To fulfill the requirements for radiation effect experiments, the storage ring manipulation of beams that utilizes a phase space beam dilution method have been developed for the broadening of the radiation damped electron bunch with longitudinal particle distribution uniformity. The method relies on phase modulation applied to a double RF system to generate large regions of bounded chaotic particle motion in phase space. These region are formed by a multitude of overlapping parametric resonances. Parameters of the double RF system and applied phase modulation can be adjusted to vary the degree of beam dilution. The optimal RF parameters have been found for maximal bunch broadening, uniform longitudinal particle distribution, and bounded particle diffusion. Implementation of the phase space dilution method

  16. Frequency-doubled vertical-external-cavity surface-emitting laser

    DOEpatents

    Raymond, Thomas D.; Alford, William J.; Crawford, Mary H.; Allerman, Andrew A.

    2002-01-01

    A frequency-doubled semiconductor vertical-external-cavity surface-emitting laser (VECSEL) is disclosed for generating light at a wavelength in the range of 300-550 nanometers. The VECSEL includes a semiconductor multi-quantum-well active region that is electrically or optically pumped to generate lasing at a fundamental wavelength in the range of 600-1100 nanometers. An intracavity nonlinear frequency-doubling crystal then converts the fundamental lasing into a second-harmonic output beam. With optical pumping with 330 milliWatts from a semiconductor diode pump laser, about 5 milliWatts or more of blue light can be generated at 490 nm. The device has applications for high-density optical data storage and retrieval, laser printing, optical image projection, chemical-sensing, materials processing and optical metrology.

  17. Low temperature laser scanning microscopy of a superconducting radio-frequency cavity

    NASA Astrophysics Data System (ADS)

    Ciovati, G.; Anlage, Steven M.; Baldwin, C.; Cheng, G.; Flood, R.; Jordan, K.; Kneisel, P.; Morrone, M.; Nemes, G.; Turlington, L.; Wang, H.; Wilson, K.; Zhang, S.

    2012-03-01

    An apparatus was developed to obtain, for the first time, 2D maps of the surface resistance of the inner surface of an operating superconducting radio-frequency niobium cavity by a low-temperature laser scanning microscopy technique. This allows identifying non-uniformities of the surface resistance with a spatial resolution of about 2.4 mm and surface resistance resolution of ˜1 μΩ at 3.3 GHz. A signal-to-noise ratio of about 10 dB was obtained with 240 mW laser power and 1 Hz modulation frequency. The various components of the apparatus, the experimental procedure and results are discussed in detail in this contribution.

  18. Long-term frequency stabilization system for external cavity diode laser based on mode boundary detection

    NASA Astrophysics Data System (ADS)

    Xu, Zhouxiang; Huang, Kaikai; Jiang, Yunfeng; Lu, Xuanhui

    2011-12-01

    We have realized a long-term frequency stabilization system for external cavity diode laser (ECDL) based on mode boundary detection method. In this system, the saturated absorption spectroscopy was used. The current and the grating of the ECDL were controlled by a computer-based feedback control system. By checking if there are mode boundaries in the spectrum, the control system determined how to adjust current to avoid mode hopping. This procedure was executed periodically to ensure the long-term stabilization of ECDL in the absence of mode hops. This diode laser system with non-antireflection coating had operated in the condition of long-term mode-hop-free stabilization for almost 400 h, which is a significant improvement of ECDL frequency stabilization system.

  19. Frequency-diverse microwave imaging using planar Mills-Cross cavity apertures.

    PubMed

    Yurduseven, Okan; Gollub, Jonah N; Marks, Daniel L; Smith, David R

    2016-04-18

    We demonstrate a frequency diverse, multistatic microwave imaging system based on a set of transmit and receive, radiating, planar cavity apertures. The cavities consist of double-sided, copper-clad circuit boards, with a series of circular radiating irises patterned into the upper conducting plate. The iris arrangement is such that for any given transmitting and receiving aperture pair, a Mills-Cross pattern is formed from the overlapped patterns. The Mills-Cross distribution provides optimum coverage of the imaging scene in the spatial Fourier domain (k-space). The Mills-Cross configuration of the apertures produces measurement modes that are diverse and consistent with the computational imaging approach used for frequency-diverse apertures, yet significantly minimizes the redundancy of information received from the scene. We present a detailed analysis of the Mills-Cross aperture design, with numerical simulations that predict the performance of the apertures as part of an imaging system. Images reconstructed using fabricated apertures are presented, confirming the anticipated performance. PMID:27137323

  20. Modelling of horn antennas and detector cavities for the SAFARI instrument at THz frequencies

    NASA Astrophysics Data System (ADS)

    Doherty, S.; Trappe, N.; O'Sullivan, C.; Murphy, J. A.; Curran, G.; Mauskopf, P.; Zhang, J.; Withington, S.; Goldie, D.; Glowaka, D.; Khosropanah, P.; Ridder, M.; Brujin, M.; Gao, J. R.; Griffin, D.; Swinyard, B.; Ferlot, M.

    2011-02-01

    Future Far-IR space telescopes, such as the SAFARI instrument of the proposed JAXA/ESA SPICA mission, will use horn antennas to couple to cavity bolometers to achieve high levels of sensitivity for Mid-IR astronomy. In the case of the SAFARI instrument the bolometric detectors susceptibility to currents coupling into the detector system and dissipating power within the bolometers is a particular concern of the class of detector technology considered.1 The simulation of such structures can prove challenging. At THz frequencies ray tracing no longer proves completely accurate for these partially coherent large electrical structures, which also present significant computational difficulties for the more generic EM approaches applied at longer microwave wavelengths. The Finite Difference Time Domain method and other similar commercially viable approaches result in excessive computational requirements, especially when a large number of modes propagate. Work being carried out at NUI-Maynooth is utilising a mode matching approach to the simulation of such devices. This approach is based on the already proven waveguide mode scattering code "Scatter"2 developed at NUI-Maynooth, which is a piece of mode matching code that operates by cascading a Smatrice while conserving power at each waveguide junction. This paper outlines various approaches to simulating such Antenna Horns and Cavities at THz frequencies, focusing primarily on the waveguide modal Scatter approach. Recently the code has been adapted to incorporate a rectangular waveguide basis mode set instead of the already established circular basis set.

  1. Highly Accurate Frequency Calculations of Crab Cavities Using the VORPAL Computational Framework

    SciTech Connect

    Austin, T.M.; Cary, J.R.; Bellantoni, L.; /Argonne

    2009-05-01

    We have applied the Werner-Cary method [J. Comp. Phys. 227, 5200-5214 (2008)] for extracting modes and mode frequencies from time-domain simulations of crab cavities, as are needed for the ILC and the beam delivery system of the LHC. This method for frequency extraction relies on a small number of simulations, and post-processing using the SVD algorithm with Tikhonov regularization. The time-domain simulations were carried out using the VORPAL computational framework, which is based on the eminently scalable finite-difference time-domain algorithm. A validation study was performed on an aluminum model of the 3.9 GHz RF separators built originally at Fermi National Accelerator Laboratory in the US. Comparisons with measurements of the A15 cavity show that this method can provide accuracy to within 0.01% of experimental results after accounting for manufacturing imperfections. To capture the near degeneracies two simulations, requiring in total a few hours on 600 processors were employed. This method has applications across many areas including obtaining MHD spectra from time-domain simulations.

  2. High frequency radar software reference manual for product one

    NASA Astrophysics Data System (ADS)

    Walden, D. C.; Winkelman, J. R.; Matheson, L. D.; Schultz, L. D.; Merrill, R. G.

    1984-02-01

    This manual for use with the HF Radar Product 1 software was first distributed to users in draft form in 1978. It has been updated several times since then as the software has evolved. It is being formally published now to record the achievement and to form a more convenient reference manual for the use of this product.

  3. Temporal characterization of FEL micropulses as function of cavity length detuning using frequency-resolved optical gating

    SciTech Connect

    Richman, B.A.; DeLong, K.W.; Trebino, R.

    1995-12-31

    Results of frequency resolved optical gating (FROG) measurements on the Stanford mid-IR FEL system show the effect of FEL cavity length detuning on the micropulse temporal structure. The FROG technique enables the acquisition of complete and uniquely invertible amplitude and phase temporal dependence of optical pulses. Unambiguous phase and amplitude profiles are recovered from the data. The optical pulses are nearly transform limited, and the pulse length increases with cavity length detuning.

  4. Temperature dependence of spontaneous switch-on and switch-off of laser cavity solitons in vertical-cavity surface-emitting lasers with frequency-selective feedback

    NASA Astrophysics Data System (ADS)

    Jimenez, J.; Oppo, G.-L.; Ackemann, T.

    2016-03-01

    A systematic experimental and numerical investigation of the conditions for the spontaneous formation of laser cavity solitons in broad-area vertical-cavity surface-emitting lasers with frequency-selective feedback by a volume Bragg grating is reported. It is shown that the switching thresholds are controlled by a combination of frequency shifts induced by ambient temperature and Joule heating. The gain level has only a minor influence on the threshold but controls mainly the power of the solitons. At large initial detuning and high threshold gain, the first observed structure can be a high order soliton. In real devices spatial disorder in the cavity length causes a pinning of solitons and a dispersion of thresholds. The experimental observations are in good agreement with numerical simulations taking into account disorder and the coupling of gain and cavity resonance due to Joule heating. In particular, we demonstrate that the existence of the traps explain the spontaneous switch on of the solitons, but do not modify the soliton shape significantly, i.e. the observed solitons are a good approximation of the ones expected in a homogeneous system.

  5. Superconducting NbTiN thin films for superconducting radio frequency accelerator cavity applications

    DOE PAGESBeta

    Burton, Matthew C.; Beebe, Melissa R.; Yang, Kaida; Lukaszew, Rosa A.; Valente-Feliciano, Anne -Marie; Reece, Charles

    2016-02-12

    Current superconducting radio frequency technology, used in various particle accelerator facilities across the world, is reliant upon bulk niobium superconducting cavities. Due to technological advancements in the processing of bulk Nb cavities, the facilities have reached accelerating fields very close to a material-dependent limit, which is close to 50 MV/m for bulk Nb. One possible solution to improve upon this fundamental limitation was proposed a few years ago by Gurevich [Appl. Phys. Lett. 88, 012511 (2006)], consisting of the deposition of alternating thin layers of superconducting and insulating materials on the interior surface of the cavities. The use of type-IImore » superconductors with Tc > TcNb and Hc > HcNb, (e.g., Nb3Sn, NbN, or NbTiN) could potentially greatly reduce the surface resistance (Rs) and enhance the accelerating field, if the onset of vortex penetration is increased above HcNb, thus enabling higher field gradients. Although Nb3Sn may prove superior, it is not clear that it can be grown as a suitable thin film for the proposed multilayer approach, since very high temperature is typically required for its growth, hindering achieving smooth interfaces and/or surfaces. On the other hand, since NbTiN has a smaller lower critical field (Hc1) and higher critical temperature (Tc) than Nb and increased conductivity compared to NbN, it is a promising candidate material for this new scheme. Here, the authors present experimental results correlating filmmicrostructure with superconducting properties on NbTiN thin film coupon samples while also comparing filmsgrown with targets of different stoichiometry. In conclusion, it is worth mentioning that the authors have achieved thin films with bulk-like lattice parameter and transition temperature while also achieving Hc1 values larger than bulk for films thinner than their London penetration depths.« less

  6. Broadband frequency conversion and shaping of single photons emitted from a nonlinear cavity.

    PubMed

    McCutcheon, Murray W; Chang, Darrick E; Zhang, Yinan; Lukin, Mikhail D; Loncar, Marko

    2009-12-01

    Much recent effort has focused on coupling individual quantum emitters to optical microcavities in order to produce single photons on demand, enable single-photon optical switching, and implement functional nodes of a quantum network. Techniques to control the bandwidth and frequency of the outgoing single photons are of practical importance, allowing direct emission into telecommunications wavelengths and "hybrid" quantum networks incorporating different emitters. Here, we describe an integrated approach involving a quantum emitter coupled to a nonlinear optical resonator, in which the emission wavelength and pulse shape are controlled using the intra-cavity nonlinearity. Our scheme is general in nature, and demonstrates how the photonic environment of a quantum emitter can be tailored to determine the emission properties. As specific examples, we discuss a high Q-factor, TE-TM double-mode photonic crystal cavity design that allows for direct generation of single photons at telecom wavelengths (1425 nm) starting from an InAs/GaAs quantum dot with a 950 nm transition wavelength, and a scheme for direct optical coupling between such a quantum dot and a diamond nitrogen-vacancy center at 637 nm. PMID:20052195

  7. Plasma Studies in a High Pressure Gas Filled Radio Frequency Cavity

    NASA Astrophysics Data System (ADS)

    Freemire, Ben; Chung, Moses; Tollestrup, Alvin; Yonehara, Katsuya

    2014-10-01

    A Muon Collider offers a great deal of physics potential to the high energy physics community. In order to build such a machine with the desired luminosity, significant cooling of the muon beam is required. One proposed method for doing so is the Helical Cooling Channel, which consists of high pressure gas filled radio frequency (HPRF) cavities arranged in a helix within a strong external magnetic field. To validate this technology, an HPRF cavity was subjected to a 400 MeV proton beam at Fermilab's MuCool Test Area. Parent gases of hydrogen, deuterium, helium and nitrogen, at room temperature and densities up to 2.5E21 cm-3 were used, and doped with sulfur hexafluoride or dry air. The plasma density created by the beam approached 1E16 cm-3. Measurements of the RF energy dissipated per charged particle pair, the electron-ion recombination rate, the ion-ion recombination rate, and electron attachment time were made.

  8. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Cavity design and linear analysis of 225 GHz frequency-quadrupling gyroklystron

    NASA Astrophysics Data System (ADS)

    Liu, Di-Wei; Yuan, Xue-Song; Yan, Yang; Liu, Sheng-Gang

    2009-07-01

    This paper considers the frequency-quadrupling three-cavity gyroklystrons with successive frequency-doubling in each cavity. The cavities of 225 GHz frequency-quadrupling gyroklystron are designed with the scattering matrices method and the possible operating mode are discussed. With the point-gap theory, the starting currents of the possible operating modes and the potential parasitic modes in the output cavity are calculated. The optimal operating mode is proposed under consideration of the mode competition and the power capacity of the cavity.

  9. A calculable, transportable audio-frequency AC reference standard

    SciTech Connect

    Oldham, N.M.; Hetrick, P.S. ); Zeng, X. )

    1989-04-01

    A transportable ac voltage source is described, in which sinusoidal signals are synthesized digitally in the audio-frequency range. The rms value of the output waveform may be calculated by measuring the dc level of the individual steps used to generate the waveform. The uncertainty of this calculation at the 7-V level is typically less than +-5 ppm from 60 Hz to 2 kHz and less than +-10 ppm from 30 Hz to 15 kHz.

  10. System and method for tuning adjusting the central frequency of a laser while maintaining frequency stabilization to an external reference

    NASA Technical Reports Server (NTRS)

    Livas, Jeffrey (Inventor); Thorpe, James I. (Inventor); Numata, Kenji (Inventor)

    2011-01-01

    A method and system for stabilizing a laser to a frequency reference with an adjustable offset. The method locks a sideband signal generated by passing an incoming laser beam through the phase modulator to a frequency reference, and adjusts a carrier frequency relative to the locked sideband signal by changing a phase modulation frequency input to the phase modulator. The sideband signal can be a single sideband (SSB), dual sideband (DSB), or an electronic sideband (ESB) signal. Two separate electro-optic modulators can produce the DSB signal. The two electro-optic modulators can be a broadband modulator and a resonant modulator. With a DSB signal, the method can introduce two sinusoidal phase modulations at the phase modulator. With ESB signals, the method can further drive the optical phase modulator with an electrical signal with nominal frequency OMEGA(sub 1) that is phase modulated at a frequency OMEGA(sub 2)

  11. Reliable and integrated technique for determining resonant frequency in radio frequency resonators. Application to a high-precision resonant cavity-based displacement sensor

    NASA Astrophysics Data System (ADS)

    Jauregui, Rigoberto; Asua, Estibaliz; Portilla, Joaquin; Etxebarria, Victor

    2015-03-01

    This paper presents a reliable and integrated technique for determining the resonant frequency of radio frequency resonators, which can be of interest for different purposes. The approach uses a heterodyne scheme as phase detector coupled to a voltage-controlled oscillator. The system seeks the oscillator frequency that produces a phase null in the resonator, which corresponds to the resonant frequency. A complete explanation of the technique to determine the resonant frequency is presented and experimentally tested. The method has been applied to a high-precision displacement sensor based on resonant cavity, obtaining a theoretical nanometric precision.

  12. Frequency-Based Investigation of Charge Neutralization Processes and Thermal Cavity Expansion in Gyrotrons

    NASA Astrophysics Data System (ADS)

    Schlaich, Andreas; Wu, Chuanren; Pagonakis, Ioannis; Avramidis, Konstantinos; Illy, Stefan; Gantenbein, Gerd; Jelonnek, John; Thumm, Manfred

    2015-09-01

    During the first hundred milliseconds, the frequency and RF output power of long pulse operating gyrotrons undergo deterministic variation. This well-known behavior is caused by the thermal expansion of the cavity and internal electrostatic processes related to the ionization of residual gas. A macroscopic analytical investigation of the gas conditions in modern gyrotrons indicates that ionization processes are unlikely to influence the overall internal gas pressure. In combination with electrostatic potential considerations, it was found that the beam depression voltage is not fully neutralized; in the case of W7-X gyrotrons, a maximum value of about 60 % neutralization is expected, in conflict with the common assumption of full neutralization in steady state. Using experimentally measured frequency shifts and the Evridiki gyrotron interaction simulation code, a fitting process was employed to further investigate these effects. The results are in very good agreement with the theoretical predictions and allow a separation of the time constants of the two processes causing the frequency tuning.

  13. Laser polishing of niobium for application to superconducting radio frequency cavities

    SciTech Connect

    Singaravelu, Senthil; Klopf, John Michael; Xu, Chen; Krafft, Geoffrey; Kelley, Michael J.

    2012-09-01

    Superconducting radio frequency niobium cavities are at the heart of an increasing number of particle accelerators. Their performance is dominated by a several nanometer thick layer at the interior surface. Maximizing the smoothness of this surface is critical, and aggressive chemical treatments are now employed to this end. The authors describe laser-induced surface melting as an alternative 'greener' approach. Selection of laser parameters guided by modeling achieved melting that reduced the surface roughness from the fabrication process. The resulting topography was examined by scanning electron microscope and atomic force microscope (AFM). Plots of power spectral density computed from the AFM data give further insight into the effect of laser melting on the topography of the mechanically polished (only) niobium.

  14. Low-frequency fluctuations in vertical cavity lasers: Experiments versus Lang-Kobayashi dynamics

    SciTech Connect

    Torcini, Alessandro; Barland, Stephane; Giacomelli, Giovanni; Marin, Francesco

    2006-12-15

    The limits of applicability of the Lang-Kobayashi (LK) model for a semiconductor laser with optical feedback are analyzed. The model equations, equipped with realistic values of the parameters, are investigated below the solitary laser threshold where low-frequency fluctuations (LFF's) are usually observed. The numerical findings are compared with experimental data obtained for the selected polarization mode from a vertical cavity surface emitting laser (VCSEL) subject to polarization selective external feedback. The comparison reveals the bounds within which the dynamics of the LK model can be considered as realistic. In particular, it clearly demonstrates that the deterministic LK model, for realistic values of the linewidth enhancement factor {alpha}, reproduces the LFF's only as a transient dynamics towards one of the stationary modes with maximal gain. A reasonable reproduction of real data from VCSEL's can be obtained only by considering the noisy LK or alternatively deterministic LK model for extremely high {alpha} values.

  15. Coherent Optical Frequency Domain Reflectometry (OFDR) using a fiber grating external cavity laser

    NASA Astrophysics Data System (ADS)

    Huang, Kao-Yang; Carter, Gary M.

    1994-12-01

    An optical frequency domain reflectometry (OFDR) system containing a narrow linewidth fiber grating external cavity laser is demonstrated to have 62-dB of sensitivity when detecting Fresnel backreflection and 2 m of resolution at a 115 m range in optical fiber. With this system we were able to detect Rayleigh backscattering in optical fiber with 20-dB signal-to-noise ratio. The phase noise limitation on the distance range for the OFDR was investigated, and the measured signal-to-noise ratio (SNR) data followed the theoretical simulation over the ranges measured. This technique has potential to be applied to the OFDR at 1550 nm with very high dynamic range by using an erbium doped fiber laser.

  16. Reclamation of niobium compounds from ionic liquid electrochemical polishing of superconducting radio frequency cavities

    SciTech Connect

    Wixtrom, Alex I.; Buhler, Jessica E.; Reece, Charles E.; Abdel-Fattah, Tarek M.

    2013-06-01

    Recent research has shown that choline chloride (vitamin B4)-based solutions can be used as a greener alternative to acid-based electrochemical polishing solutions. This study demonstrated a successful method for electrochemical deposition of niobium compounds onto the surface of copper substrates using a novel choline chloride-based ionic liquid. Niobium ions present in the ionic liquid solution were dissolved into the solution prior to deposition via electrochemical polishing of solid niobium. A black coating was clearly visible on the surface of the Cu following deposition. This coating was analyzed using scanning electron microscopy (SEM), electron dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), and X-ray fluorescence spectroscopy (XRF). This ionic liquid-based electrochemical deposition method effectively recycles previously dissolved niobium from electrochemical polishing of superconducting radio frequency (SRF) cavities.

  17. Surface polishing of niobium for superconducting radio frequency (SRF) cavity applications

    SciTech Connect

    Zhao, Liang

    2014-08-01

    Niobium cavities are important components in modern particle accelerators based on superconducting radio frequency (SRF) technology. The interior of SRF cavities are cleaned and polished in order to produce high accelerating field and low power dissipation on the cavity wall. Current polishing methods, buffered chemical polishing (BCP) and electro-polishing (EP), have their advantages and limitations. We seek to improve current methods and explore laser polishing (LP) as a greener alternative of chemical methods. The topography and removal rate of BCP at different conditions (duration, temperature, sample orientation, flow rate) was studied with optical microscopy, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). Differential etching on different crystal orientations is the main contributor to fine grain niobium BCP topography, with gas evolution playing a secondary role. The surface of single crystal and bi-crystal niobium is smooth even after heavy BCP. The topography of fine grain niobium depends on total removal. The removal rate increases with temperature and surface acid flow rate within the rage of 0~20 °C, with chemical reaction being the possible dominate rate control mechanism. Surface flow helps to regulate temperature and avoid gas accumulation on the surface. The effect of surface flow rate on niobium EP was studied with optical microscopy, atomic force microscopy (AFM), and power spectral density (PSD) analysis. Within the range of 0~3.7 cm/s, no significant difference was found on the removal rate and the macro roughness. Possible improvement on the micro roughness with increased surface flow rate was observed. The effect of fluence and pulse accumulation on niobium topography during LP was studied with optical microscopy, SEM, AFM, and PSD analysis. Polishing on micro scale was achieved within fluence range of 0.57~0.90 J/cm2, with pulse accumulation adjusted accordingly. Larger area treatment was proved possible by

  18. Insights to Superconducting Radio-Frequency Cavity Processing from First Principles Calculations and Spectroscopic Techniques

    SciTech Connect

    Ford, Denise Christine

    2013-03-01

    Insights to the fundamental processes that occur during the manufacturing of niobium superconducting radio-frequency (SRF) cavities are provided via analyses of density functional theory calculations and Raman, infrared, and nuclear magnetic resonance (NMR) spectra. I show that during electropolishing fluorine is bound and released by the reaction of the acid components in the solution: HF + H2SO4 <-> HFSO3 + H2O. This result implies that new recipes can possibly be developed on the principle of controlled release of fluorine by a chemical reaction. I also show that NMR or Raman spectroscopy can be used to monitor the free fluorine when polishing with the standard electropolishing recipe. Density functional theory was applied to calculate the properties of common processing impurities – hydrogen, oxygen, nitrogen, and carbon – in the niobium. These impurities lower the superconducting transition temperature of niobium, and hydride precipitates are at best weakly superconducting. I modeled several of the niobium hydride phases relevant to SRF cavities, and explain the phase changes in the niobium hydrogen system based on the charge transfer between niobium and hydrogen and the strain field inside of the niobium. I also present evidence for a niobium lattice vacancy serving as a nucleation center for hydride phase formation. In considering the other chemical impurities in niobium, I show that the absorption of oxygen into a niobium lattice vacancy is preferred over the absorption of hydrogen, which indicates that oxygen can block these phase nucleation centers. I also show that dissolved oxygen atoms can trap dissolved hydrogen atoms to prevent niobium hydride phase formation. Nitrogen and carbon were studied in less depth, but behaved similarly to oxygen. Based on these results and a literature survey, I propose a mechanism for the success of the low-temperature anneal applied to niobium SRF cavities. Finally, I

  19. Insights to Superconducting Radio-Frequency Cavity Processing from First Principles Calculations and Spectroscopic Techniques

    NASA Astrophysics Data System (ADS)

    Ford, Denise Christine

    Insights to the fundamental processes that occur during the manufacturing of niobium superconducting radio-frequency (SRF) cavities are provided via analyses of density functional theory calculations and Raman, infrared, and nuclear magnetic resonance (NMR) spectra. I show that during electropolishing fluorine is bound and released by the reaction of the acid components in the solution: HF + H2SO4 <-> HFSO3 + H2O. This result implies that new recipes can possibly be developed on the principle of controlled release of fluorine by a chemical reaction. I also show that NMR or Raman spectroscopy can be used to monitor the free fluorine when polishing with the standard electropolishing recipe. Density functional theory was applied to calculate the properties of common processing impurities---hydrogen, oxygen, nitrogen, and carbon---in the niobium. These impurities lower the superconducting transition temperature of niobium, and hydride precipitates are at best weakly superconducting. I modeled several of the niobium hydride phases relevant to SRF cavities, and explain the phase changes in the niobium hydrogen system based on the charge transfer between niobium and hydrogen and the strain field inside of the niobium. I also present evidence for a niobium lattice vacancy serving as a nucleation center for hydride phase formation. In considering the other chemical impurities in niobium, I show that the absorption of oxygen into a niobium lattice vacancy is preferred over the absorption of hydrogen, which indicates that oxygen can block these phase nucleation centers. I also show that dissolved oxygen atoms can trap dissolved hydrogen atoms to prevent niobium hydride phase formation. Nitrogen and carbon were studied in less depth, but behaved similarly to oxygen. Based on these results and a literature survey, I propose a mechanism for the success of the low-temperature anneal applied to niobium SRF cavities. Finally, I present the beginning of a model to describe magnetic

  20. The frequency of dietary references in homeopathic consultations.

    PubMed

    Filho, Rubens Dolce

    2011-07-01

    A retrospective quantitative study on dietary references found in medical records of 2753 patients attending consultations from 10/1/1994 to 5/31/2007 was conducted. The symptoms found in the rubrics relating to food and drink aggravation and amelioration, aversion and craving of homeopathic repertories reflect diets at different places and times and do not correspond fully, to contemporary gastronomy. Desires for sweet and spicy foods were statistically more frequent, revealing the prevailing taste for such food among the studied population. Food cravings should be carefully analyzed before considering them as indications for choosing homeopathic therapy, they are less significant than aversions, aggravations and ameliorations. PMID:21784331

  1. High frequency radar software reference manual for Product Two

    NASA Astrophysics Data System (ADS)

    Walden, D. C.; Winkelman, J. R.; Matheson, L. D.; Grubb, R. N.

    1984-03-01

    The Space Environment Laboratory (SEL) of NOAA developed a general purpose High Frequency (HF) Radar system capable of making most of the measurements of the ionosphere that can be made by coherent monostatic or bistatic radio wave sounding. This capability is provided by combining a very flexible, frequency-agile transmitter and receiver system with a digital control and signal processing system containing a general purpose 16-bit minicomputer for operator interaction and control. A manual is given which describes the software operating system written by the SEL staff to permit the Radar to be used for quite a wide range of standard measurements under simple operator control. The control language enables the user to exploit most of the capabilities of the instrument without having to program the system in detail. The manual is primarily directed at the user who needs to understand and use this capability. Secondarily, if used in conjunction with the computer manufacturer's system and language manuals, the SEL HF Radar Hardware manuals and the SEL source code listings, it should enable an experienced user to customize the software for special purposes or to produce new operating software.

  2. A novel approach to a PPM-modulated frequency-doubled electro-optic cavity-dumped Nd:YAG laser

    NASA Technical Reports Server (NTRS)

    Robinson, D. L.

    1989-01-01

    A technique which can provide frequency doubling, with high efficiency, while cavity dumping a laser for pulse position M-ary modulation while being used for an optical communication link is discussed. This approach uses a secondary cavity that provides feedback of the undoubled fundamental light, which is normally lost, into the primary cavity to be recirculated and frequency doubled. Specific operations of the electrooptic modulator and frequency-doubling crystal are described along with the overall modulation scheme and experimental setup.

  3. Dual-frequency comb generation with differing GHz repetition rates by parallel Fabry–Perot cavity filtering of a single broadband frequency comb source

    NASA Astrophysics Data System (ADS)

    Mildner, Jutta; Meiners-Hagen, Karl; Pollinger, Florian

    2016-07-01

    We present a dual-comb-generator based on a coupled Fabry–Perot filtering cavity doublet and a single seed laser source. By filtering a commercial erbium-doped fiber-based optical frequency comb with CEO-stabilisation and 250 MHz repetition rate, two broadband coherent combs of different repetition rates in the GHz range are generated. The filtering doublet consists of two Fabry–Perot cavities with a tunable spacing and Pound–Drever–Hall stabilisation scheme. As a prerequisite for the development of such a filtering unit, we present a method to determine the actual free spectral range and transmission bandwidth of a Fabry–Perot cavity in situ. The transmitted beat signal of two diode lasers is measured as a function of their tunable frequency difference. Finally, the filtering performance and resulting beat signals of the heterodyned combs are discussed as well as the optimisation measures of the whole system.

  4. Analysis of trace impurities in semiconductor gas via cavity-enhanced direct frequency comb spectroscopy

    NASA Astrophysics Data System (ADS)

    Cossel, K. C.; Adler, F.; Bertness, K. A.; Thorpe, M. J.; Feng, J.; Raynor, M. W.; Ye, J.

    2010-09-01

    Cavity-enhanced direct frequency comb spectroscopy (CE-DFCS) has demonstrated powerful potential for trace-gas detection based on its unique combination of high bandwidth, rapid data acquisition, high sensitivity, and high resolution, which is unavailable with conventional systems. However, previous demonstrations have been limited to proof-of-principle experiments or studies of fundamental laboratory science. Here, we present the development of CE-DFCS towards an industrial application—measuring impurities in arsine, an important process gas used in III-V semiconductor compound manufacturing. A strongly absorbing background gas with an extremely complex, congested, and broadband spectrum renders trace detection exceptionally difficult, but the capabilities of CE-DFCS overcome this challenge and make it possible to identify and quantify multiple spectral lines associated with water impurities. Further, frequency combs allow easy access to new spectral regions via efficient nonlinear optical processes. Here, we demonstrate detection of multiple potential impurities across 1.75-1.95 μm (5710-5130 cm-1), with a single-channel detection sensitivity (simultaneously over 2000 channels) of ˜4×10-8 cm-1 Hz-1/2 in nitrogen and, specifically, an absorption sensitivity of ˜4×10-7 cm-1 Hz-1/2 for trace water doped in arsine.

  5. Etching of Niobium Sample Placed on Superconducting Radio Frequency Cavity Surface in Ar/CL2 Plasma

    SciTech Connect

    Janardan Upadhyay, Larry Phillips, Anne-Marie Valente

    2011-09-01

    Plasma based surface modification is a promising alternative to wet etching of superconducting radio frequency (SRF) cavities. It has been proven with flat samples that the bulk Niobium (Nb) removal rate and the surface roughness after the plasma etchings are equal to or better than wet etching processes. To optimize the plasma parameters, we are using a single cell cavity with 20 sample holders symmetrically distributed over the cell. These holders serve the purpose of diagnostic ports for the measurement of the plasma parameters and for the holding of the Nb sample to be etched. The plasma properties at RF (100 MHz) and MW (2.45 GHz) frequencies are being measured with the help of electrical and optical probes at different pressures and RF power levels inside of this cavity. The niobium coupons placed on several holders around the cell are being etched simultaneously. The etching results will be presented at this conference.

  6. Pump-Induced, Dual-Frequency Switching in a Short-Cavity, Ytterbium-Doped Fiber Laser

    SciTech Connect

    Guan, W.; Marciante, J.R.

    2008-07-23

    Using a short linear cavity composed of a section of highly ytterbium-doped fiber surrounded by two fiber Bragg gratings, dual frequency switching is achieved by tuning the pump power of the laser. The dual-frequency switching is generated by the thermal effects of the absorbed pump in the ytterbium-doped fiber. At each frequency, the laser shows single-longitudinal-mode behavior. In each single-mode regime, the optical signal-to-noise ratio of the laser is greater than 50 dB. The dual-frequency, switchable, fiber laser can be designed for various applications by the careful selection of the two gratings.

  7. Characterization of the frequency stability of an optical frequency standard at 1.39 µm based upon noise-immune cavity-enhanced optical heterodyne molecular spectroscopy.

    PubMed

    Dinesan, H; Fasci, E; D'Addio, A; Castrillo, A; Gianfrani, L

    2015-01-26

    Frequency fluctuations of an optical frequency standard at 1.39 µm have been measured by means of a highly-sensitive optical frequency discriminator based on the fringe-side transmission of a high finesse optical resonator. Built on a Zerodur spacer, the optical resonator exhibits a finesse of 5500 and a cavity-mode width of about 120 kHz. The optical frequency standard consists of an extended-cavity diode laser that is tightly stabilized against the center of a sub-Doppler H(2) (18)O line, this latter being detected by means of noise-immune cavity-enhanced optical heterodyne molecular spectroscopy. The emission linewidth has been carefully determined from the frequency-noise power spectral density by using a rather simple approximation, known as β-line approach, as well as the exact method based on the autocorrelation function of the laser light field. It turns out that the linewidth of the optical frequency standard amounts to about 7 kHz (full width at half maximum) for an observation time of 1 ms. Compared to the free-running laser, the measured width corresponds to a line narrowing by a factor of ~220. PMID:25835931

  8. Femtosecond-laser-based synthesis of ultrastable microwave signals from optical frequency references.

    PubMed

    Bartels, A; Diddams, S A; Oates, C W; Wilpers, G; Bergquist, J C; Oskay, W H; Hollberg, L

    2005-03-15

    We use femtosecond laser frequency combs to convert optical frequency references to the microwave domain, where we demonstrate the synthesis of 10-GHz signals having a fractional frequency instability of < or =3.5 x 10(-15) at a 1-s averaging time, limited by the optical reference. The residual instability and phase noise of the femtosecond-laser-based frequency synthesizers are 6.5 x 10(-16) at 1 s and -98 dBc/Hz at a 1-Hz offset from the 10-GHz carrier, respectively. The timing jitter of the microwave signals is 3.3 fs. PMID:15792011

  9. High-power 390-nm laser source based on efficient frequency doubling of a tapered diode laser in an external resonant cavity.

    PubMed

    Bhawalkar, J D; Mao, Y; Po, H; Goyal, A K; Gavrilovic, P; Conturie, Y; Singh, S

    1999-06-15

    We frequency doubled the single-frequency beam from an external-cavity tapered laser diode operating at 780 nm in a resonant cavity containing a beta -barium borate crystal to generate an output at 390 nm with high efficiency. Output powers as great as 233 mW were obtained, corresponding to an efficiency of 65%/W . The resonant-cavity design was a low-loss three-mirror configuration that provided compensation for astigmatism and coma. The laser diode frequency was locked to the doubling-cavity resonance by use of the Hänsch-Couillaud discrimination technique. PMID:18073866

  10. Low-temperature mechanical properties of superconducting radio frequency cavity materials

    SciTech Connect

    Byun, Thak Sang; Kim, Sang-Ho; Mammosser, John

    2009-01-01

    Low temperature mechanical behaviors have been investigated for the constituent materials of superconducting radio frequency cavities. Test materials consist of small grain Nb, single crystal Nb, large grain Nb (bicrystal), Ti45Nb-Nb weld joint (e-beam welded), and Ti-316L bimetal joint (explosion welded). The strength of all test metals displayed strong temperature dependence and the Ti-316L bimetal showed the highest strength and lowest ductility among the test materials. The fracture toughness of the small grain Nb metals decreased with decreasing test temperature and reached the lower shelf values (30 40 MPa m) at or above 173 K. The Ti45Nb base and Ti45Nb-Nb weld metals showed much higher fracture toughness than the small grain Nb. An extrapolation and comparison with existing data showed that the fracture toughness of the small grain Nb metals at 4 K was expected to be similar to those at 173 K and 77 K. The results from optical photography at a low magnification and fractography by a scanning electron microscope were consistent with corresponding mechanical properties.

  11. Sum-frequency generation of continuous-wave tunable ultraviolet coherent light in BBO-installed external cavity

    NASA Astrophysics Data System (ADS)

    Mukoyama, Kenta; Tokuyama, Kazuhiro; Kumagai, Hiroshi; Inoue, Norihiro; Fukuda, Naoaki; Takiya, Toshio

    2012-02-01

    Recently, we have tried to develop a continuous wave (CW), tunable, and ultraviolet (UV) coherent light source through sum-frequency generation (SFG) using a BBO nonlinear crystal with a two-stage frequency-conversion system using two different external cavities for the enhancement of CW lights. In the first stage, we obtained the 532-nm light with the second harmonic generation (SHG) of the 1064-nm light. A bow-tie external cavity incorporating four mirrors, whose cavity length was controlled by the frequency stabilization method proposed by Hänsch and Couillaud, was employed there. In the second stage, to generate the 312-nm light, we demonstrated doubly resonant sum frequency generation of the 532-nm light from the first-stage and the 754-nm light from a single-frequency CW Ti:Sapphire laser. Considering a nonlinear coefficient, it should be preferable to use a BiBO crystal for high-efficient SFG, but the 312-nm light might be absorbed by the BiBO crystal. Therefore, we chose a BBO as a nonlinear crystal to avoid the absorption of the 312-nm light.

  12. Improving the frequency stability of microwave oscillators by utilizing the dual-mode sapphire-loaded cavity resonator

    NASA Astrophysics Data System (ADS)

    Tobar, Michael E.; Ivanov, Eugene N.; Locke, Clayton R.; Hartnett, John G.; Cros, Dominique

    2002-08-01

    The design and experimental testing of a novel control circuit to stabilize the temperature of a sapphire-loaded cavity whispering gallery resonator-oscillator and improve its medium-term frequency stability is presented. Finite-element software was used to predict frequencies and quality factors of WGE7,0,0 and the WGH9,0,0 modes near 9 GHz, and separated in frequency by approximately 80 MHz. Calculations show that the novel temperature control circuits from the difference frequency can result in a frequency stability of better than one part in 1013 at 270 K. Also, we present details on the best way to couple orthogonally to two modes of similar frequency but different polarization.

  13. Superconducting Storage Cavity for RHIC

    SciTech Connect

    Ben-Zvi,I.

    2009-01-02

    This document provides a top-level description of a superconducting cavity designed to store hadron beams in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. It refers to more detailed documents covering the various issues in designing, constructing and operating this cavity. The superconducting storage cavity is designed to operate at a harmonic of the bunch frequency of RHIC at a relatively low frequency of 56 MHz. The current storage cavities of RHIC operate at 197 MHz and are normal-conducting. The use of a superconducting cavity allows for a high gap voltage, over 2 MV. The combination of a high voltage and low frequency provides various advantages stemming from the resulting large longitudinal acceptance bucket.

  14. Three-wavelength digital holography using spatial frequency-division multiplexing and dual reference arms

    NASA Astrophysics Data System (ADS)

    Tahara, Tatsuki; Takeshita, Shingo; Morimoto, Kenta; Kaku, Toru; Arai, Yasuhiko

    2016-03-01

    We propose single-shot multiwavelength digital holography using a monochromatic image sensor and dual reference arms. Multiple wavelength information is multiplexed on the monochromatic image sensor plane in the space domain and is separated in the spatial frequency domain by utilizing the difference between the spatial frequencies of interference fringes at respective wavelengths. The recordable spatial bandwidth that is utilized for object waves is extended by using dual reference arms in comparison with that using a single reference arm. Both the three-dimensional and three-wavelength information of an object were recorded and reconstructed without the crosstalk between object waves with multiple wavelengths.

  15. Highly stable piezoelectrically tunable optical cavities

    NASA Astrophysics Data System (ADS)

    Möhle, Katharina; Kovalchuk, Evgeny V.; Döringshoff, Klaus; Nagel, Moritz; Peters, Achim

    2013-05-01

    We have implemented highly stable and tunable frequency references using optical high finesse cavities which incorporate a piezo actuator. As piezo material we used ceramic PZT, crystalline quartz, or PZN-PT single crystals. Lasers locked to these cavities show a relative frequency stability better than 1× 10^{-14}, which is most likely not limited by the piezo actuators. The piezo cavities can be electrically tuned over more than one free spectral range (>1.5 GHz) with only a minor decrease in frequency stability. Furthermore, we present a novel cavity design, where the piezo actuator is prestressed between the cavity spacer components. This design features a hermetically sealable intra cavity volume suitable for, e.g., cavity enhanced spectroscopy.

  16. In-situ plasma processing to increase the accelerating gradients of superconducting radio-frequency cavities

    NASA Astrophysics Data System (ADS)

    Doleans, M.; Tyagi, P. V.; Afanador, R.; McMahan, C. J.; Ball, J. A.; Barnhart, D. L.; Blokland, W.; Crofford, M. T.; Degraff, B. D.; Gold, S. W.; Hannah, B. S.; Howell, M. P.; Kim, S.-H.; Lee, S.-W.; Mammosser, J.; Neustadt, T. S.; Saunders, J. W.; Stewart, S.; Strong, W. H.; Vandygriff, D. J.; Vandygriff, D. M.

    2016-03-01

    A new in-situ plasma processing technique is being developed at the Spallation Neutron Source (SNS) to improve the performance of the cavities in operation. The technique utilizes a low-density reactive oxygen plasma at room temperature to remove top surface hydrocarbons. The plasma processing technique increases the work function of the cavity surface and reduces the overall amount of vacuum and electron activity during cavity operation; in particular it increases the field emission onset, which enables cavity operation at higher accelerating gradients. Experimental evidence also suggests that the SEY of the Nb surface decreases after plasma processing which helps mitigating multipacting issues. In this article, the main developments and results from the plasma processing R&D are presented and experimental results for in-situ plasma processing of dressed cavities in the SNS horizontal test apparatus are discussed.

  17. Frequency stabilization based on high finesse glass-ceramic Fabry-Perot cavity for a 632.8-nm He-Ne laser

    NASA Astrophysics Data System (ADS)

    Fu, Tingting; Yang, Kaiyong; Tan, Zhongqi; Luo, Zhifu; Wu, Suyong

    2014-12-01

    A frequency stabilization technique for a 632.8nm He-Ne laser with a high finesse Fabry-Perot cavity is introduced in this paper. The resonant frequency of the cavity is taken as the frequency standard .In this system the Fabry-Perot cavity is composed of a glass-ceramic spacer, with thermal expansion coefficient smaller than 2×10-8/°C , which means an excellent thermal stabilization which greatly decreases the thermal impacts on the cavity length in the desired constant-temperature environment.The intra-cavity spherical mirror is specially designed, which makes the Fabry-cavity a sensor element in our subsequent experiments for a new practical optical accelerometer .Both cavity mirrors were custom made in our laboratory which have reflectivities greater than 99.995% at 632.8nm, so the Fabry-Perot cavity has a finesse of about 62830. The half-maximum transmission line width is about 55.48 KHz and the free spectral range is 3.5GHz .In the experimental setup, we adopt the frequency stabilization circuit with small dithering .With proper dithering voltage, the laser can be precisely locked to the Fabry-Perot cavity minimum reflection point. Theoretically the frequency stability can reach 10-10 order.

  18. Spectral line-shapes investigation with Pound-Drever-Hall-locked frequency-stabilized cavity ring-down spectroscopy

    NASA Astrophysics Data System (ADS)

    Cygan, A.; Wójtewicz, S.; Domysławska, J.; Masłowski, P.; Bielska, K.; Piwiński, M.; Stec, K.; Trawiński, R. S.; Ozimek, F.; Radzewicz, C.; Abe, H.; Ido, T.; Hodges, J. T.; Lisak, D.; Ciuryło, R.

    2013-10-01

    A review of recent experiments involving a newly developed Pound-Drever-Hall-locked frequency-stabilized cavity ring-down spectroscopy (PDH-locked FS-CRDS) system is presented. By comparison to standard FS-CRDS, the PDH lock of the probe laser to the ring-down cavity optimized coupling into the cavity, thus increasing the ring-down signal acquisition rate nearly 300-fold to 14 kHz and reducing the noise-equivalent absorption coefficient by more than an order of magnitude to 7 × 10-11 cm-1. We discuss how averaging approximately 1000 spectra yielded a signal-to-noise ratio of 220000. We also discuss how the spectrum frequency axis was linked to an optical frequency comb, thus enabling absolute frequency measurements of molecular optical transitions at sub-MHz levels. Applications of the spectrometer to molecular line-shape studies are also presented. For these investigations, we use semi-classical line-shape models that consider the influence of Dicke narrowing as well as the speed dependence of the pressure broadening and shifting to fit spectra. We show that the improved precision and spectrum fidelity of the spectrometer enable precise determinations of line-shape parameters. We also discuss the importance of line-shape analysis with regard to the development of new spectroscopic databases as well as in the optical determination of the Boltzmann constant.

  19. Effects of electron beam parameters and velocity spread on radio frequency output of a photonic band gap cavity gyrotron oscillator

    NASA Astrophysics Data System (ADS)

    Singh, Ashutosh; Jain, P. K.

    2015-09-01

    In this paper, the effects of electron beam parameters and velocity spread on the RF behavior of a metallic photonic band gap (PBG) cavity gyrotron operating at 35 GHz with TE041-like mode have been theoretically demonstrated. PBG cavity is used here to achieve a single mode operation of the overmoded cavity. The nonlinear time-dependent multimode analysis has been used to observe the beam-wave interaction behavior of the PBG cavity gyrotron, and a commercially available PIC code "CST Particle Studio" has been reconfigured to obtain 3D simulation results in order to validate the analytical values. The output power for this typical PBG gyrotron has been obtained ˜108 kW with ˜15.5% efficiency in a well confined TE041-like mode, while all other competing modes have significantly low values of power output. The output power and efficiency of a gyrotron depend highly on the electron beam parameters and velocity spread. The influence of several electron beam parameters, e.g., beam voltage, beam current, beam velocity pitch factor, and DC magnetic field, on the PBG gyrotron operations has been investigated. This study would be helpful in optimising the electron beam parameters and estimating accurate RF output power of the high frequency PBG cavity based gyrotron oscillators.

  20. Effects of electron beam parameters and velocity spread on radio frequency output of a photonic band gap cavity gyrotron oscillator

    SciTech Connect

    Singh, Ashutosh; Jain, P. K.

    2015-09-15

    In this paper, the effects of electron beam parameters and velocity spread on the RF behavior of a metallic photonic band gap (PBG) cavity gyrotron operating at 35 GHz with TE{sub 041}–like mode have been theoretically demonstrated. PBG cavity is used here to achieve a single mode operation of the overmoded cavity. The nonlinear time-dependent multimode analysis has been used to observe the beam-wave interaction behavior of the PBG cavity gyrotron, and a commercially available PIC code “CST Particle Studio” has been reconfigured to obtain 3D simulation results in order to validate the analytical values. The output power for this typical PBG gyrotron has been obtained ∼108 kW with ∼15.5% efficiency in a well confined TE{sub 041}–like mode, while all other competing modes have significantly low values of power output. The output power and efficiency of a gyrotron depend highly on the electron beam parameters and velocity spread. The influence of several electron beam parameters, e.g., beam voltage, beam current, beam velocity pitch factor, and DC magnetic field, on the PBG gyrotron operations has been investigated. This study would be helpful in optimising the electron beam parameters and estimating accurate RF output power of the high frequency PBG cavity based gyrotron oscillators.

  1. Dissemination of optical-comb-based ultra-broadband frequency reference through a fiber network.

    PubMed

    Nagano, Shigeo; Kumagai, Motohiro; Li, Ying; Ido, Tetsuya; Ishii, Shoken; Mizutani, Kohei; Aoki, Makoto; Otsuka, Ryohei; Hanado, Yuko

    2016-08-22

    We disseminated an ultra-broadband optical frequency reference based on a femtosecond (fs)-laser optical comb through a kilometer-scale fiber link. Its spectrum ranged from 1160 nm to 2180 nm without additional fs-laser combs at the end of the link. By employing a fiber-induced phase noise cancellation technique, the linewidth and fractional frequency instability attained for all disseminated comb modes were of order 1 Hz and 10-18 in a 5000 s averaging time. The ultra-broad optical frequency reference, for which absolute frequency is traceable to Japan Standard Time, was applied in the frequency stabilization of an injection-seeded Q-switched 2051 nm pulse laser for a coherent light detection and ranging LIDAR system. PMID:27557196

  2. High-power dual-wavelength external-cavity diode laser based on tapered amplifier with tunable terahertz frequency difference.

    PubMed

    Chi, Mingjun; Jensen, Ole Bjarlin; Petersen, Paul Michael

    2011-07-15

    Tunable dual-wavelength operation of a diode laser system based on a tapered diode amplifier with double-Littrow external-cavity feedback is demonstrated around 800 nm. The two wavelengths can be tuned individually, and the frequency difference of the two wavelengths is tunable from 0.5 to 5.0 THz. An output power of 1.54 W is achieved with a frequency difference of 0.86 THz, the output power is higher than 1.3 W in the 5.0 THz range of frequency difference, and the amplified spontaneous emission intensity is more than 20 dB suppressed in the range of frequency difference. To our knowledge, this is the highest output power from a dual-wavelength diode laser system operating with tunable terahertz frequency difference. PMID:21765489

  3. Traceable dual-frequency measurement of Zeeman split He-Ne lasers using an optical frequency comb locked external cavity diode laser

    NASA Astrophysics Data System (ADS)

    Wei, Haoyun; Wu, Xuejian; Zhou, Lei; Zhang, Jitao; Li, Yan

    2012-11-01

    A frequency measurement system for dual frequency He-Ne lasers is set up based on an external cavity diode laser locked to fiber femtosecond optical frequency comb using an Rb clock as a frequency standard. The frequencies of the Zeeman split orthogonal polarized lasers are measured by beating with the locked diode laser at the same time. Locking the diode laser to the 1 894 449th comb tooth, the absolute frequency of the diode laser is 473 612 190 000.0 (2.4) kHz, with a relative frequency uncertainty of 5.1×10-12. A commercial dual frequency He-Ne laser is measured to test the system, and the results show that the mean absolute frequencies of the horizontal polarized laser and the vertical polarized laser are 473 612 229 934 kHz and 473 612 232 111 kHz, respectively, with a relative Allan deviation of 5.2× 10-11 at 1 024 s, and the mean split frequency is 2.177 MHz with a standard deviation of 2 kHz.

  4. Laser-frequency locking to a whispering-gallery-mode cavity by spatial interference of scattered light.

    PubMed

    Zullo, R; Giorgini, A; Avino, S; Malara, P; De Natale, P; Gagliardi, G

    2016-02-01

    We present a simple and effective method for frequency locking a laser source to a free-space-coupled whispering-gallery-mode cavity. The scheme relies on the interference of spatial modes contained in the light scattered by the cavity, where low- and high-order modes are simultaneously excited. A dispersion-shaped signal proportional to the imaginary component of the resonant optical field is simply generated by spatial filtering of the scattered light. Locking of a diode laser to the equatorial modes of a liquid droplet resonator is demonstrated using this scheme, and its performance is compared to the Pound-Drever-Hall technique. This new approach makes laser-frequency locking straightforward and shows a number of advantages, including robustness, low cost, and no need for sophisticated optical and electronic components. PMID:26907446

  5. Tunable ultraviolet output from an intracavity frequency-doubled red vertical-external-cavity surface-emitting laser

    NASA Astrophysics Data System (ADS)

    Hastie, Jennifer E.; Morton, Lynne G.; Kemp, Alan J.; Dawson, Martin D.; Krysa, Andrey B.; Roberts, John S.

    2006-08-01

    An optically pumped red vertical-external-cavity surface-emitting laser with an AlInGaP gain region produced more than 1W of continuous-wave output power at a wavelength of 675nm. Frequency doubling in a beta-barium borate crystal placed at an intracavity beam waist generated 120mW of total output power at 338nm. Using an intracavity birefringent filter a second harmonic tuning range of ˜5nm was achieved.

  6. High Conversion Efficiency and Power Stability of 532 nm Generation from an External Frequency Doubling Cavity

    NASA Astrophysics Data System (ADS)

    Zhao, Yang; Lin, Bai-Ke; Li, Ye; Zhang, Hong-Xi; Cao, Jian-Ping; Fang, Zhan-Jun; Li, Tian-Chu; Zang, Er-Jun

    2012-09-01

    We present a high-efficiency 532 nm green light conversion from an external cavity-enhanced second harmonic generation (SHG) with a periodically poled KTP crystal (PPKTP). The cavity is a bow-tie ring configuration with a unitized structure. When the impedance matching is optimized, the coupling efficiency of the fundamental is as high as 95%. Taking into account both the high power output of the second harmonic and the stability of the system, we obtain over 500 mW green passing through the output cavity mirror, corresponding to a net conversion efficiency higher than 75.2%. Under these operating conditions, the power stability is better than ±0.25% during 5 h. It is the highest conversion efficiency and power stability ever produced in the bow-tie ring cavity with PPKTP for 532 nm generation.

  7. Accuracy In Numerical Prediction Of Cavity Length and Vapor Cloud Shedding Frequency Of Cavitating Flows Over Various Geometries.

    NASA Astrophysics Data System (ADS)

    Jayaprakash, Arvind; Mahalatkar, Kathikeya

    2006-11-01

    Standard two-equation turbulence models have been found to be incapable of predicting cavitating flow due to high compressibility in the vapor region. In order to predict the dynamics of vapor cloud shedding, Courtier-Delgosha (J. of Fluid Eng, 125, 2003) suggested a modification for the eddy viscosity for k-epsilon turbulence model. Though the modification works in capturing the dynamic behavior of cavitation sheet, the accuracy of cavity length and frequency is not achieved for a wide range of cavitation numbers. This is due to the complex flow features present during a cavitating flow and the incapability of Couitier-Delgosh's turbulence modification to account for these factors. A tuning factor is introduced in the turbulence modification of Coutier-Delgosha, which can be adjusted for different types of geometries. This modified form is then tuned and tested on prediction of cavitating flow over several geometries including NACA 0015 hydrofoil, Convergent-Divergent Nozzle, and Wedge. Good comparisons for both cavity length and frequency of vapor cloud shedding were obtained for wide range of cavitation numbers in all the geometries. The commercial CFD software Fluent has been used for this analysis. Comparisons of cavity length and vapor cloud shedding frequency as predicted by the present turbulence modification and those observed in experimental studies will be presented.

  8. Frequency scanning interferometry with nanometer precision using a vertical-cavity surface-emitting laser diode under scanning speed control

    NASA Astrophysics Data System (ADS)

    Kakuma, Seiichi

    2015-12-01

    Frequency scanning interferometry technique with a nanometer precision using a vertical-cavity surface-emitting laser diode (VCSEL) is presented. Since the frequency scanning of the VCSEL is linearized by the phase-locked-loop technique, the gradient of the interference fringe order can be precisely determined using linear least squares fitting. This enables a length measurement with a precision better than a quarter wavelength, and the absolute fringe number including the integer part at the atomic transition spectrum (rubidium-D2 line) is accurately determined. The validity of the method is demonstrated by excellent results of block gauge measurement with a root mean square error better than 5 nm.

  9. Low-pressure line-shape study in molecular oxygen with absolute frequency reference

    NASA Astrophysics Data System (ADS)

    Domysławska, J.; Wójtewicz, S.; Cygan, A.; Bielska, K.; Lisak, D.; Masłowski, P.; Trawiński, R. S.; Ciuryło, R.

    2013-11-01

    We present a line-shape analysis of the rovibronic R1 Q2 transition of the oxygen B band resolved by the Pound-Drever-Hall-locked frequency-stabilized cavity ring-down spectroscopy technique in the low pressure range. The frequency axis of the spectra is linked by the ultra-narrow diode laser to the optical frequency comb in order to measure the absolute frequency at each point of the recorded spectra. Experimental spectra are fitted with various line-shape models: the Voigt profile, the Galatry profile, the Nelkin-Ghatak profile, the speed-dependent Voigt profile, and the speed-dependent Nelkin-Ghatak profile with quadratic and hypergeometric approximations for the speed dependence of collisional broadening and shifting. The influences of Dicke narrowing, speed-dependent effects, and correlation between phase- and velocity-changing collisions on the line shape are investigated. Values of line-shape parameters, including the absolute frequency of the transition 435685.24828(46) GHz, are reported.

  10. Coherent-state storage and retrieval between superconducting cavities using parametric frequency conversion

    SciTech Connect

    Sirois, A. J.; Castellanos-Beltran, M. A.; DeFeo, M. P.; Ranzani, L.; Lecocq, F.; Simmonds, R. W.; Teufel, J. D.; Aumentado, J.

    2015-04-27

    In superconducting quantum information, machined aluminum superconducting cavities have proven to be a well-controlled, low-dissipation electromagnetic environment for quantum circuits such as qubits. They can possess large internal quality factors, Q{sub int} > 10{sup 8}, and present the possibility of storing quantum information for times far exceeding those of microfabricated circuits. However, in order to be useful as a storage element, these cavities require a fast “read/write” mechanism—in other words, they require tunable coupling between other systems of interest such as other cavity modes and qubits, as well as any associated readout hardware. In this work, we demonstrate these qualities in a simple dual cavity architecture in which a low-Q “readout” mode is parametrically coupled to a high-Q “storage” mode, allowing us to store and retrieve classical information. Specifically, we employ a flux-driven Josephson junction-based coupling scheme to controllably swap coherent states between two cavities, demonstrating full, sequenced control over the coupling rates between modes.

  11. Coherent-state storage and retrieval between superconducting cavities using parametric frequency conversion

    NASA Astrophysics Data System (ADS)

    Sirois, A. J.; Castellanos-Beltran, M. A.; DeFeo, M. P.; Ranzani, L.; Lecocq, F.; Simmonds, R. W.; Teufel, J. D.; Aumentado, J.

    2015-04-01

    In superconducting quantum information, machined aluminum superconducting cavities have proven to be a well-controlled, low-dissipation electromagnetic environment for quantum circuits such as qubits. They can possess large internal quality factors, Qint > 108, and present the possibility of storing quantum information for times far exceeding those of microfabricated circuits. However, in order to be useful as a storage element, these cavities require a fast "read/write" mechanism—in other words, they require tunable coupling between other systems of interest such as other cavity modes and qubits, as well as any associated readout hardware. In this work, we demonstrate these qualities in a simple dual cavity architecture in which a low-Q "readout" mode is parametrically coupled to a high-Q "storage" mode, allowing us to store and retrieve classical information. Specifically, we employ a flux-driven Josephson junction-based coupling scheme to controllably swap coherent states between two cavities, demonstrating full, sequenced control over the coupling rates between modes.

  12. Towards a reference cavitating vessel Part III—design and acoustic pressure characterization of a multi-frequency sonoreactor

    NASA Astrophysics Data System (ADS)

    Wang, Lian; Memoli, Gianluca; Hodnett, Mark; Butterworth, Ian; Sarno, Dan; Zeqiri, Bajram

    2015-08-01

    A multi-frequency cavitation vessel (RV-multi) has been commissioned at the National Physical Laboratory (NPL, UK), with the aim of establishing a standard source of acoustic cavitation in water, with reference to which details of the cavitation process can be studied and cavitation measurement techniques evaluated. The vessel is a cylindrical cavity with a maximum capacity up to 17 L, and is designed to work at six frequency ranges, from 21 kHz to 136 kHz, under controlled temperature conditions. This paper discusses the design of RV-multi and reports experiments carried out to establish the reproducibility of the acoustic pressure field established within the vessel and its operating envelope, including sensitivity to aspects such as water depth and temperature. The acoustic field distribution was determined along the radial and depth directions within the vessel using a miniature hydrophone, for two input voltage levels under low power transducer excitation conditions (e.g. below the cavitation threshold). Particular care was taken in determining peak acoustic pressure locations, as these are critical for accompanying cavitation studies. Perturbations of the vessel by the measuring hydrophone were also monitored with a bottom-mounted pressure sensor.

  13. Towards high-frequency operation of polarization oscillations in spin vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Lindemann, Markus; Höpfner, Henning; Gerhardt, Nils C.; Hofmann, Martin R.; Pusch, Tobias; Michalzik, Rainer

    2015-09-01

    Compared to purely charge based devices, spintronic lasers offer promising perspectives for new superior device concepts. Especially vertical-cavity surface-emitting lasers with spin-polarization (spin-VCSELs) feature ultrafast spin and polarization dynamics. Oscillations in the circular polarization degree can be generated using pulsed spin-injection. The oscillations evolve due to the carrier-spin-photon system that is coupled for the linear modes in the VCSEL's cavity via the birefringence. The polarization oscillations are independent of the conventional relaxation oscillations and have the potential to exceed frequencies of 100 GHz. The oscillations are switchable and can be the basis for ultrafast directly modulated spin-VCSELs for, e.g., communication purposes. The polarization oscillation frequency is mainly determined by the birefringence. We show a method to tune the birefringence and thus the polarization oscillation frequency by adding mechanical strain to the substrate in the vicinity of the laser. We achieved first experimental results for high-frequency operation using 850 nm oxide-confined single-mode VCSELs. The results are compared with simulations using the spin-flip-model for high birefringence values.

  14. Square Kilometre Array Telescope--Precision Reference Frequency Synchronisation via 1f-2f Dissemination.

    PubMed

    Wang, B; Zhu, X; Gao, C; Bai, Y; Dong, J W; Wang, L J

    2015-01-01

    The Square Kilometre Array (SKA) project is an international effort to build the world's largest radio telescope, with a one-square-kilometre collecting area. In addition to its ambitious scientific objectives, such as probing cosmic dawn and the cradle of life, the SKA demands several revolutionary technological breakthroughs, such as ultra-high precision synchronisation of the frequency references for thousands of antennas. In this report, with the purpose of application to the SKA, we demonstrate a frequency reference dissemination and synchronisation scheme in which the phase-noise compensation function is applied at the client site. Hence, one central hub can be linked to a large number of client sites, thus forming a star-shaped topology. As a performance test, a 100-MHz reference frequency signal from a hydrogen maser (H-maser) clock is disseminated and recovered at two remote sites. The phase-noise characteristics of the recovered reference frequency signal coincide with those of the H-maser source and satisfy the SKA requirements. PMID:26349544

  15. Square Kilometre Array Telescope—Precision Reference Frequency Synchronisation via 1f-2f Dissemination

    PubMed Central

    Wang, B.; Zhu, X.; Gao, C.; Bai, Y.; Dong, J. W.; Wang, L. J.

    2015-01-01

    The Square Kilometre Array (SKA) project is an international effort to build the world’s largest radio telescope, with a one-square-kilometre collecting area. In addition to its ambitious scientific objectives, such as probing cosmic dawn and the cradle of life, the SKA demands several revolutionary technological breakthroughs, such as ultra-high precision synchronisation of the frequency references for thousands of antennas. In this report, with the purpose of application to the SKA, we demonstrate a frequency reference dissemination and synchronisation scheme in which the phase-noise compensation function is applied at the client site. Hence, one central hub can be linked to a large number of client sites, thus forming a star-shaped topology. As a performance test, a 100-MHz reference frequency signal from a hydrogen maser (H-maser) clock is disseminated and recovered at two remote sites. The phase-noise characteristics of the recovered reference frequency signal coincide with those of the H-maser source and satisfy the SKA requirements. PMID:26349544

  16. Square Kilometre Array Telescope—Precision Reference Frequency Synchronisation via 1f-2f Dissemination

    NASA Astrophysics Data System (ADS)

    Wang, B.; Zhu, X.; Gao, C.; Bai, Y.; Dong, J. W.; Wang, L. J.

    2015-09-01

    The Square Kilometre Array (SKA) project is an international effort to build the world’s largest radio telescope, with a one-square-kilometre collecting area. In addition to its ambitious scientific objectives, such as probing cosmic dawn and the cradle of life, the SKA demands several revolutionary technological breakthroughs, such as ultra-high precision synchronisation of the frequency references for thousands of antennas. In this report, with the purpose of application to the SKA, we demonstrate a frequency reference dissemination and synchronisation scheme in which the phase-noise compensation function is applied at the client site. Hence, one central hub can be linked to a large number of client sites, thus forming a star-shaped topology. As a performance test, a 100-MHz reference frequency signal from a hydrogen maser (H-maser) clock is disseminated and recovered at two remote sites. The phase-noise characteristics of the recovered reference frequency signal coincide with those of the H-maser source and satisfy the SKA requirements.

  17. Cavity piezomechanical strong coupling and frequency conversion on an aluminum nitride chip

    NASA Astrophysics Data System (ADS)

    Zou, Chang-Ling; Han, Xu; Jiang, Liang; Tang, Hong X.

    2016-07-01

    Schemes to achieve strong coupling between mechanical modes of aluminum nitride microstructures and microwave cavity modes due to the piezoelectric effect are proposed. We show that the strong-coupling regime is feasible for an on-chip aluminum nitride device that is either enclosed by a three-dimensional microwave cavity or integrated with a superconducting coplanar resonator. Combining with optomechanics, the piezomechanical strong coupling permits coherent conversion between microwave and optical modes with high efficiency. Hence, the piezomechanical system will be an efficient transducer for applications in hybrid quantum systems.

  18. Surface Characterization of Nb Samples Electro-polished Together With Real Superconducting Radio-frequency Accelerator Cavities

    DOE PAGESBeta

    Xin Zhao; Geng, Rongli; Tyagi, P. V.; Hayano, Hitoshi; Kato, Shigeki; Nishiwaki, Michiru; Saeki, Takayuki; Sawabe, Motoaki

    2010-12-01

    We report the results of surface characterizations of niobium (Nb) samples electropolished together with a single cell superconducting radio-frequency accelerator cavity. These witness samples were located in three regions of the cavity, namely at the equator, the iris and the beam-pipe. Auger electron spectroscopy (AES) was utilized to probe the chemical composition of the topmost four atomic layers. Scanning electron microscopy with energy dispersive X-ray for elemental analysis (SEM/EDX) was used to observe the surface topography and chemical composition at the micrometer scale. A few atomic layers of sulfur (S) were found covering the samples non-uniformly. Niobium oxide granules withmore » a sharp geometry were observed on every sample. Some Nb-O granules appeared to also contain sulfur.« less

  19. A digitally compensated 1.5 GHz CMOS/FBAR frequency reference.

    PubMed

    Rai, Shailesh; Su, Ying; Pang, Wei; Ruby, Richard; Otis, Brian

    2010-03-01

    A temperature-compensated 1.5 GHz film bulk acoustic wave resonator (FBAR)-based frequency reference implemented in a 0.35 microm CMOS process is presented. The ultra-small form factor (0.79 mm x 1.72 mm) and low power dissipation (515 microA with 2 V supply) of a compensated FBAR oscillator present a promising alternative for the replacement of quartz crystal frequency references. The measured post-compensation frequency drift over a 0-100 degrees C temperature range is < +/- 10 ppm. The measured oscillator phase noise is -133 dBc/Hz at 100 kHz offset from the 1.5 GHz carrier. PMID:20211770

  20. Singly resonant sum-frequency generation of 520-nm laser via a variable input-coupling transmission cavity

    NASA Astrophysics Data System (ADS)

    Guo, Shanlong; Ge, Yulong; He, Jun; Wang, Junmin

    2015-11-01

    We experimentally present a three-mirror folded singly resonant sum-frequency generation (SFG) cavity with an adjustable input coupling, which has been applied to 520-nm single-frequency laser generation via 780-nm laser and 1560-nm laser frequency mixing in a periodically poled KTiOPO4 crystal (PPKTP). A continuous variation in the input coupling reflectivity from 81.4 to 96.1% for 780-nm resonant laser is achieved by tilting the input coupler, and the impedance matching of the resonator can be optimized. Up to 268 mW of SFG output power at 520-nm is obtained with 6.8 W of the 1560-nm laser input and 1.5 W of 780-nm laser input.

  1. Coherent continuous-wave dual-frequency high-Q external-cavity semiconductor laser for GHz-THz applications.

    PubMed

    Paquet, Romain; Blin, Stéphane; Myara, Mikhaël; Gratiet, Luc Le; Sellahi, Mohamed; Chomet, Baptiste; Beaudoin, Grégoire; Sagnes, Isabelle; Garnache, Arnaud

    2016-08-15

    We report a continuous-wave highly-coherent and tunable dual-frequency laser emitting at two frequencies separated by 30 GHz to 3 THz, based on compact III-V diode-pumped quantum-well surface-emitting semiconductor laser technology. The concept is based on the stable simultaneous operation of two Laguerre-Gauss transverse modes in a single-axis short cavity, using an integrated sub-wavelength-thick metallic mask. Simultaneous operation is demonstrated theoretically and experimentally by recording intensity noises and beat frequency, and time-resolved optical spectra. We demonstrated a >80  mW output power, diffraction-limited beam, narrow linewidth of <300  kHz, linear polarization state (>45  dB), and low intensity noise class-A dynamics of <0.3% rms, thus opening the path to a compact low-cost coherent GHz to THz source development. PMID:27519080

  2. The Impact on the Positioning Accuracy of the Frequency Reference of a GPS Receiver

    NASA Astrophysics Data System (ADS)

    Yeh, Ta-Kang; Chen, Chieh-Hung; Xu, Guochang; Wang, Chuan-Sheng; Chen, Kwo-Hwa

    2013-01-01

    Despite the pervasive use of the global positioning system (GPS) as a positioning technology for its high efficiency and accuracy, several factors reduce its performance. This study examines to which extent the frequency offset and the frequency stability of the internal quartz oscillator or of an externally supplied rubidium oscillator have an influence. Observations were made at the Taiwan Ching Yun University (TCYU) tracking station, where a quartz oscillator and a rubidium oscillator were applied alternatively on a monthly basis throughout a 16-month period. Moreover, the accuracy of the local oscillator used in this study was calibrated by the National Standard Time and Frequency Laboratory, Taiwan. The frequency offset and frequency stability calculated via the remote method at the TCYU station were compared with values (uncertainty is 3.0E-13) measured directly at the National Standard Time and Frequency Laboratory, Taiwan. Analytical results show that the two methods vary by 1.4E-10 in terms of frequency offset and by 6.5E-12 in terms of frequency stability, demonstrating that the remote method can yield computational results almost as accurate as direct measurement. Positioning precision results also show that rubidium oscillator accuracy improved by 5, 11, and 15 % for short-, medium-, and long-baseline positioning, respectively, indicating that clock quality is more influential for long-baseline GPS relative positioning and that the frequency stability of a receiver clock is far more critical than the frequency offset. On the other hand, the positioning performance noted is essentially independent (max. 15 % change) of the reference frequency stability, which indeed differed by 4 orders of magnitude.

  3. Frequency-Stabilized Cavity Ring-Down Spectroscopy of Oxygen and Carbon Dioxide to Support Atmospheric Remote Sensing

    NASA Astrophysics Data System (ADS)

    Long, David Alexander

    Recent remote-sensing satellite missions have aimed to measure global greenhouse gas concentrations with precisions as demanding as 0.25%. These high-resolution measurements should allow for the quantification of carbon sources and sinks, thus, allowing for a considerable reduction in present carbon cycle uncertainties. To achieve these unprecedented measurement goals will require the most precise body of spectroscopic reference data (i.e., laboratory measurements) ever assembled. In order to aid these missions, we have measured ultraprecise spectroscopic parameters for the (30012)←(00001) CO2 band at 1.57 microm and the O2 A-band at 0.76 microm. These near-infrared transitions are utilized in recent greenhouse gas monitoring missions, with the A-band being employed to derive pressure and temperature profiles. In these investigations we have employed frequency-stabilized cavity ring-down spectroscopy (FS-CRDS), a novel ultrasensitive spectroscopic technique. In the O2 A-band we have measured magnetic dipole line parameters for 16O 2 as well as each of the rare isotopologues and have produced calculated, HITRAN-style line lists. Due to the clear presence of collisional narrowing in the spectra, we have utilized the Galatry line profile in these studies and have reported narrowing parameters under self- and air-broadened conditions. We anticipate that the use of these spectral parameters will greatly reduce the uncertainties of atmospheric remote-sensing retrievals. In addition, the spectral fidelity of FS-CRDS allowed us to observe and quantify unresolved hyperfine structure for the 17O-containing isotopologues. Furthermore, the high sensitivity of FS-CRDS enabled measurements of ultraweak (S˜10 -30 cm molec.-1) electric quadrupole transitions in the A-band, many of which had not previously been observed. Recently we have begun a series of studies of the near-infrared CO2 transitions. Measurements at low pressures (<40 kPa) have revealed the simultaneous presence

  4. Conceptual design of a sapphire loaded coupler for superconducting radio-frequency 1.3 GHz cavities

    NASA Astrophysics Data System (ADS)

    Xu, Chen; Tantawi, Sami

    2016-02-01

    This paper explores a hybrid mode rf structure that served as a superconducting radio-frequency coupler. This application achieves a reflection S(1 ,1 ) varying from 0 to -30 db and delivers cw power at 7 KW. The coupler has good thermal isolation between the 2 and 300 K sections due to vacuum separation. Only one single hybrid mode can propagate through each section, and no higher order mode is coupled. The analytical and numerical analysis for this coupler is given and the design is optimized. The coupling mechanism to the cavity is also discussed.

  5. Analysis of Nb3Sn surface layers for superconducting radio frequency cavity applications

    NASA Astrophysics Data System (ADS)

    Becker, Chaoyue; Posen, Sam; Groll, Nickolas; Cook, Russell; Schlepütz, Christian M.; Hall, Daniel Leslie; Liepe, Matthias; Pellin, Michael; Zasadzinski, John; Proslier, Thomas

    2015-02-01

    We present an analysis of Nb3Sn surface layers grown on a bulk Niobium (Nb) coupon prepared at the same time and by the same vapor diffusion process used to make Nb3Sn coatings on 1.3 GHz Nb cavities. Tunneling spectroscopy reveals a well-developed, homogeneous superconducting density of states at the surface with a gap value distribution centered around 2.7 ± 0.4 meV and superconducting critical temperatures (Tc) up to 16.3 K. Scanning transmission electron microscopy performed on cross sections of the sample's surface region shows an ˜2 μm thick Nb3Sn surface layer. The elemental composition map exhibits a Nb:Sn ratio of 3:1 and reveals the presence of buried sub-stoichiometric regions that have a ratio of 5:1. Synchrotron x-ray diffraction experiments indicate a polycrystalline Nb3Sn film and confirm the presence of Nb rich regions that occupy about a third of the coating volume. These low Tc regions could play an important role in the dissipation mechanisms occurring during RF tests of Nb3Sn-coated Nb cavities and open the way for further improving a very promising alternative to pure Nb cavities for particle accelerators.

  6. Time domain and frequency domain design techniques for model reference adaptive control systems

    NASA Technical Reports Server (NTRS)

    Boland, J. S., III

    1971-01-01

    Some problems associated with the design of model-reference adaptive control systems are considered and solutions to these problems are advanced. The stability of the adapted system is a primary consideration in the development of both the time-domain and the frequency-domain design techniques. Consequentially, the use of Liapunov's direct method forms an integral part of the derivation of the design procedures. The application of sensitivity coefficients to the design of model-reference adaptive control systems is considered. An application of the design techniques is also presented.

  7. Model for initiation of quality factor degradation at high accelerating fields in superconducting radio-frequency cavities

    NASA Astrophysics Data System (ADS)

    Dzyuba, A.; Romanenko, A.; Cooley, L. D.

    2010-12-01

    A model for the onset of the reduction in superconducting radio-frequency (SRF) cavity quality factor, the so-called Q-drop, at high accelerating electric fields is presented. Since magnetic fields at the cavity equator are tied to accelerating electric fields by a simple geometric factor, the onset of magnetic flux penetration determines the onset of Q-drop. We consider breakdown of the surface barrier at triangular grooves to predict the magnetic field of first flux penetration Hpen. Such defects were argued to be the worst case by Buzdin and Daumens (1998 Physica C 294 257), whose approach, moreover, incorporates both the geometry of the groove and local contamination via the Ginzburg-Landau parameter κ. Since previous Q-drop models focused on either topography or contamination alone, the proposed model allows new comparisons of one effect in relation to the other. The model predicts equivalent reduction of Hpen when either roughness or contamination were varied alone, so smooth but dirty surfaces limit cavity performance about as much as rough but clean surfaces do. Still lower Hpen was predicted when both effects were combined, i.e. contamination should exacerbate the negative effects of roughness and vice versa. To test the model with actual data, coupons were prepared by buffered chemical polishing and electropolishing, and stylus profilometry was used to obtain distributions of angles. From these data, curves for surface resistance generated by simple flux flow as a function of magnetic field were generated by integrating over the distribution of angles for reasonable values of κ. This showed that combined effects of roughness and contamination indeed reduce the Q-drop onset field by ~ 20%, and that contamination contributes to Q-drop as much as roughness. The latter point may be overlooked by SRF cavity research, since access to the cavity interior by spectroscopy tools is very difficult, whereas optical images have become commonplace. The model was

  8. Frequency Response Calculations of Input Characteristics of Cavity-Backed Aperture Antennas Using AWE with Hybrid FEM/MoM Technique

    NASA Technical Reports Server (NTRS)

    Reddy, C. J.; Deshpande, M. D.

    1997-01-01

    Application of Asymptotic Waveform Evaluation (AWE) is presented in conjunction with a hybrid Finite Element Method (FEM)/Method of Moments (MoM) technique to calculate the input characteristics of cavity-backed aperture antennas over a frequency range. The hybrid FEM/MoM technique is used to form an integro-partial-differential equation to compute the electric field distribution of the cavity-backed aperture antenna. The electric field, thus obtained, is expanded in a Taylor series around the frequency of interest. The coefficients of 'Taylor series (called 'moments') are obtained using the frequency derivatives of the integro-partial-differential Equation formed by the hybrid FEM/MoM technique. Using the moments, the electric field in the cavity is obtained over a frequency range. Using the electric field at different frequencies, the input characteristics of the antenna are obtained over a wide frequency band. Numerical results for an open coaxial line, probe fed cavity, and cavity-backed microstrip patch antennas are presented. Good agreement between AWE and the exact solution over the frequency range is observed.

  9. Synthesis of Optical Frequencies and Ultrastable Femtosecond Pulse Trains from an Optical Reference Oscillator

    NASA Astrophysics Data System (ADS)

    Bartels, A.; Ramond, T. M.; Diddams, S. A.; Hollberg, L.

    Recently, atomic clocks based on optical frequency standards have been demonstrated [1,2]. A key element in these clocks is a femtosecond laser that downconverts the petahertz oscillation rate into countable ticks at 1 GHz. When compared to current microwave standards, these new optical clocks are expected to yield an improvement in stability and accuracy by roughly a factor of 1000. Furthermore, it is possible that the lowest noise microwave sources will soon be based on atomically-stabilized optical oscillators that have their frequency converted to the microwave domain via a femtosecond laser. Here, we present tests of the ability of femtosecond lasers to transfer stability from an optical oscillator to their repetition rates as well as to the associated broadband frequency comb. In a first experiment, we phase-lock two lasers to a stabilized laser diode and find that the relative timing jitter in their pulse trains can be on the order of 1 femtosecond in a 100 kHz bandwidth. It is important to distinguish this technique from previous work where a femtosecond laser has been stabilized to a microwave standard [3,4] or another femtosecond laser [5]. Furthermore, we extract highly stable microwave signals with a fractional frequency instability of 2×10-14 in 1 s by photodetection of the laser pulse trains. In a second experiment, we similarly phase-lock the femtosecond laser to an optical oscillator with linewidth less than 1 Hz [6]. The precision with which we can make the femtosecond frequency comb track this reference oscillator is then tested by a heterodyne measurement between a second stable optical oscillator and a mode of the frequency comb that is displaced 76 THz from the 1 Hz-wide reference. From this heterodyne signal we place an upper limit of 150 Hz on the linewidth of the elements of the frequency comb, limited by the noise in the measurement itself.

  10. Use of 130Te 2 for frequency referencing and active stabilisation of a violet extended cavity diode laser

    NASA Astrophysics Data System (ADS)

    Burns, I. S.; Hult, J.; Kaminski, C. F.

    2006-04-01

    This paper reports on the use of 130Te 2 absorption lines in active laser-locking, and in frequency referencing, of the emission of a violet extended cavity diode laser with a wavelength of around 410 nm. We note the existence of closely spaced tellurium absorption lines, suitable for referencing purposes in gas sensing applications, at wavelengths below the lower limit (417 nm) of the spectral region covered by the tellurium atlas [J. Cariou, P. Luc, Atlas du spectre d'Absorption de la Molecule de Tellure, CNRS, Paris, 1980]. The absolute positions of the lines in the acquired spectra were estimated by comparison to a simultaneously acquired fluorescence spectrum of atomic indium, and were identified using calculations based on fundamental spectroscopic data. The laser frequency was stabilised within a range of 40 MHz, which is negligible compared to typical transition widths at atmospheric pressure.