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Sample records for ghz methanol masers

  1. 37 GHz METHANOL MASERS : HORSEMEN OF THE APOCALYPSE FOR THE CLASS II METHANOL MASER PHASE?

    SciTech Connect

    Ellingsen, S. P.; Breen, S. L.; Sobolev, A. M.; Voronkov, M. A.; Caswell, J. L.; Lo, N.

    2011-12-01

    We report the results of a search for class II methanol masers at 37.7, 38.3, and 38.5 GHz toward a sample of 70 high-mass star formation regions. We primarily searched toward regions known to show emission either from the 107 GHz class II methanol maser transition, or from the 6.035 GHz excited OH transition. We detected maser emission from 13 sources in the 37.7 GHz transition, eight of these being new detections. We detected maser emission from three sources in the 38 GHz transitions, one of which is a new detection. We find that 37.7 GHz methanol masers are only associated with the most luminous 6.7 and 12.2 GHz methanol maser sources, which in turn are hypothesized to be the oldest class II methanol sources. We suggest that the 37.7 GHz methanol masers are associated with a brief evolutionary phase (of 1000-4000 years) prior to the cessation of class II methanol maser activity in the associated high-mass star formation region.

  2. 37 GHz Methanol Masers : Horsemen of the Apocalypse for the Class II Methanol Maser Phase?

    NASA Astrophysics Data System (ADS)

    Ellingsen, S. P.; Breen, S. L.; Sobolev, A. M.; Voronkov, M. A.; Caswell, J. L.; Lo, N.

    2011-12-01

    We report the results of a search for class II methanol masers at 37.7, 38.3, and 38.5 GHz toward a sample of 70 high-mass star formation regions. We primarily searched toward regions known to show emission either from the 107 GHz class II methanol maser transition, or from the 6.035 GHz excited OH transition. We detected maser emission from 13 sources in the 37.7 GHz transition, eight of these being new detections. We detected maser emission from three sources in the 38 GHz transitions, one of which is a new detection. We find that 37.7 GHz methanol masers are only associated with the most luminous 6.7 and 12.2 GHz methanol maser sources, which in turn are hypothesized to be the oldest class II methanol sources. We suggest that the 37.7 GHz methanol masers are associated with a brief evolutionary phase (of 1000-4000 years) prior to the cessation of class II methanol maser activity in the associated high-mass star formation region.

  3. A search for methanol masers at 44 GHz

    NASA Astrophysics Data System (ADS)

    Kalenskij, S. V.; Bachiller, R.; Berulis, I. I.; Val'tts, I. E.; Gomez-Gonzalez, J.; Martin-Pintado, J.; Rodriguez-Franco, A.; Slysh, V. I.

    1992-10-01

    Results of an extensive survey of young stellar objects in the methanol line 7(0) - 6(1)A(+) (44 GHz) are presented. Three new masers were detected towards cold IRAS sources in the dark clouds L 291 (GGD 27), L 379, and IC 1396 N. The new masers were also observed in 4(-1) - 3(0) E (36 GHz) and 1(0) - 0(0)A(+) (48 GHz) methanol transitions. A relationship between methanol masers and high-velocity flows with dense disks around central sources is proposed, and a possible correlation between maser emission and their intensity in the FIR is suggested.

  4. Astronomical Masers: Polarization Properties of 22-GHZ Water and 6.7-GHZ Methanol Masers.

    NASA Astrophysics Data System (ADS)

    Surcis, Gabriele; Vlemmings, Wouter H. T.; van Langevelde, Huib Jan

    2014-06-01

    By observing the astronomical masers in the Milky Way we can determine for instance high-accurate distances of the hosting Galactic sources (e.g., Galactic star-forming regions) and the kinematic of the gas where the masers arise (e.g., the kinematic of Keplerian accretion disks and outflows in massive star-forming regions). In addition, the bright and narrow spectral line emissions of water and methanol masers are ideal for measuring the Zeeman splitting as well as for determining the orientation of the magnetic field in 3-dimensions around massive young stellar objects (YSOs). Therefore, water and methanol maser species can help us to answer several crucial questions about massive star-formation. For instance, one of the most debated question is whether magnetic fields are important in the formation of high-mass stars (M>8 {Msun}). The main difficulty in answering this question is related to the fast evolution of the high-mass stars that makes the massive YSOs rare. Furthermore, they are typically found at fairly large distance. Hence, it is very difficult to measure the magnetic fields at distances <100 Astronomical Units from the central protostar by using dust polarized emissions. But fortunately, the direct measurement of magnetic fields at small scale (10-100 Astronomical Units) around massive YSOs is possible by observing the polarized emission of masers. In my oral contribution, besides showing the polarization properties of 22-GHz water and 6.7-GHz methanol masers, I will show our most interesting results about the determination of the orientation and of the strength of magnetic fields around massive YSOs. We have also started a systematic study for determining if there exists a real alignment between magnetic fields and the large scale outflows that are launched from the central protostar, which is important to constrain future simulations. Furthermore, we are involved in laboratory and modelling efforts to calibrate the magnitude of the Zeeman effect

  5. STATISTICAL PROPERTIES OF 12.2 GHz METHANOL MASERS ASSOCIATED WITH A COMPLETE SAMPLE OF 6.7 GHz METHANOL MASERS

    SciTech Connect

    Breen, S. L.; Caswell, J. L.; Green, J. A.; Voronkov, M. A.; Ellingsen, S. P.; Fuller, G. A.; Quinn, L. J.; Avison, A.

    2011-06-01

    We present definitive detection statistics for 12.2 GHz methanol masers toward a complete sample of 6.7 GHz methanol masers detected in the Methanol Multibeam survey south of declination -20{sup 0}. In total, we detect 250 12.2 GHz methanol masers toward 580 6.7 GHz methanol masers. This equates to a detection rate of 43.1%, which is lower than that of previous significant searches of comparable sensitivity. Both the velocity ranges and the flux densities of the target 6.7 GHz sources surpass that of their 12.2 GHz companion in almost all cases. Eighty percent of the detected 12.2 GHz methanol maser peaks are coincident in velocity with the 6.7 GHz maser peak. Our data support an evolutionary scenario whereby the 12.2 GHz sources are associated with a somewhat later evolutionary stage than the 6.7 GHz sources devoid of this transition. Furthermore, we find that the 6.7 GHz and 12.2 GHz methanol sources increase in luminosity as they evolve. In addition to this, evidence for an increase in velocity range with evolution is presented. This implies that it is not only the luminosity but also the volume of gas conducive to the different maser transitions that increases as the sources evolve. Comparison with GLIMPSE mid-infrared sources has revealed a coincidence rate between the locations of the 6.7 GHz methanol masers and GLIMPSE point sources similar to that achieved in previous studies. Overall, the properties of the GLIMPSE sources with and without 12.2 GHz counterparts are similar. There is a higher 12.2 GHz detection rate toward those 6.7 GHz methanol masers that are coincident with extended green objects.

  6. 6.7 GHz methanol masers: Properties, Associations and Tracers of Galactic Structure

    NASA Astrophysics Data System (ADS)

    Pandian, Jagadheep D.

    2007-01-01

    The 6.7 GHz transition of methanol is the strongest of methanol masers, and is the second strongest maser transition ever observed in the Milky Way. There is st rong theoretical and observational evidence that the masers trace an early phase of massive star formation. The lack of association of these masers with other astronomical objects such as low-mass young stellar objects (YSOs) and late type stars, and their high brightness temperatures makes them excellent tools to detect and study massive star formation across our Galaxy. The preponderance of massive stars along the spiral arms of galaxies also imply the potential utility of these methanol masers to study the spiral structure of our Galaxy. In this dissertation, we present a study of 6.7 GHz methanol masers and their properties based on the Arecibo Methanol Maser Galactic Plane Survey (AMGPS), a sensitive blind survey carried out with the Arecibo radio telescope. To carry out this study, we built a receiver for Arecibo that could process signals between 6 and 8 GHz. The high sensitivity of the cooled receiver and the large collecting area of Arecibo made AMGPS the most sensitive blind survey to date for 6.7 GHz methanol masers, and resulted in the detection of 86 methanol masers, 48 of which are new detections. The distribution of methanol masers as a function of Galactic latitude and the statistics of their multi-wavelength counterparts show our data to be consistent with the hypothesis of 6.7 GHz methanol masers being associated with massive YSOs. Using the detection statistics of AMGPS, we estimate the minimum number of methanol masers in the Galaxy to be 1125. The l-v diagram of the AMGPS sample shows the tangent point of the Carina-Sagittarius spiral arm to be around 49.6°, and suggests occurrence of massive star formation along the extension of the Crux-Scutum arm. A Gaussian component analysis of methanol masers shows the mean line-width to be 0.38 km s^{-1} which is more a factor of two larger than

  7. Resolving distance ambiguities towards 6.7 GHz methanol masers

    NASA Astrophysics Data System (ADS)

    Pandian, J. D.; Momjian, E.; Goldsmith, P. F.

    2008-07-01

    Context: Distances to most star forming regions are determined using kinematics, through the assumption that the observed radial velocity arises from the motion of the source with respect to the Sun resulting from the differential rotation of Galaxy. The primary challenge associated with the application of this technique in the inner Galaxy is the kinematic distance ambiguity. Aims: In this work, we aim to resolve the kinematic distance ambiguity towards a sample of 6.7 GHz methanol masers, which are signposts of the early stages of massive star formation. Methods: We measured 21 cm H I absorption spectra using the Very Large Array in C and CnB configurations. A comparison of the maximum velocity of H I absorption with the source velocity and tangent point velocity was used to resolve the kinematic distance ambiguity. Results: We resolved the distance ambiguity towards 41 sources. Distance determinations that are in conflict with previous measurements are discussed. The NE2001 spiral arm model is broadly consistent with the locations of the star forming complexes. We find that the use of vertical scale height arguments to resolve the distance ambiguity can lead to erroneous classifications for a significant fraction of sources.

  8. Studying Star Formation in the Central Molecular Zone using 22 GHz Water and 6.7 GHz Methanol Masers

    NASA Astrophysics Data System (ADS)

    Rickert, Matthew; Yusef-Zadeh, Farhad; Ott, Juergen; Meier, David S.; SWAG

    2016-01-01

    The inner 400 pc of our Galaxy, or the so-called the central molecular zone (CMZ), has a unique environment with a large mass of dense, warm molecular gas. One of the premier questions is how star formation (SF) differs in this unique environment from elsewhere in the Galaxy. We intend to address this issue by identifying improved numbers and locations of early sites of SF. We have conducted high resolution surveys of the CMZ, looking for early SF indicators such as 22 GHz water and 6.7 GHz methanol masers. We present the initial water maser results from the SWAG survey and methanol results from the first full VLA survey of 6.7 GHz methanol masers in the CMZ. These surveys span beyond the inner 1.2ο x 0.5ο of the Galaxy, including Sgr B through Sgr C. The improved spatial and spectral resolutions (~26" and 2 km s-1) and sensitivity (RMS ~10 mJy beam-1) of our ATCA observations have allowed us to identify over 140 water maser candidates in the SWAG survey. This is a factor of 3 more than detected from prior surveys of the CMZ. The preliminary distribution of these candidates appears to be uniform along Galactic longitude. Should this distribution persist for water masers associated with star formation (as opposed to those produced by evolved stars), then this result would imply a more uniform distribution of recent SF activity in the CMZ. Prior works have shown that 2/3 of the molecular gas mass is located at positive Galactic longitudes, and young stellar objects (YSOs) identified by IR SEDs are located predominantly at negative Galactic longitudes. A combination of these results can provide insight on the evolution of SF within the CMZ. We are currently comparing the water maser positions to other catalogs (ex. OH/IR stars) in order to distinguish between the mechanisms producing these masers. We are also currently working on determining the distribution of 6.7 GHz methanol masers. These masers do not contain the same ambiguity as water masers as to their source

  9. Ammonia and CO Outflow around 6.7 GHz Methanol Masers

    NASA Astrophysics Data System (ADS)

    Li, F. C.; Xu, Y.; Wu, Y. W.; Yang, J.; Lu, D. R.; Menten, K. M.; Henkel, C.

    2016-10-01

    Single point observations are presented in NH3 (1, 1) and (2, 2) inversion transitions using the Effelsberg 100 m telescope for a sample of 100 6.7 GHz methanol masers and mapping observations in the 12CO and 13CO (1 ‑ 0) transitions using the Purple Mountain Observatory Delingha 13.7 m telescope for 82 sample sources with detected ammonia. A further 62 sources were selected for either 12CO or 13CO line outflow identification, producing 45 outflow candidates, 29 using 12CO and 16 using 13CO data. Twenty-two of the outflow candidates were newly identified, and 23 had trigonometric parallax distances. Physical properties were derived from ammonia lines and CO outflow parameters were calculated. Histograms and statistical correlations for ammonia, CO outflow parameters, and 6.7 GHz methanol maser luminosities are also presented. No significant correlation was found between ammonia and maser luminosity. However, weak correlations were found between outflow properties and maser luminosities, which may indicate that outflows are physically associated with 6.7 GHz masers.

  10. DETECTION OF 36 GHz CLASS I METHANOL MASER EMISSION TOWARD NGC 253

    SciTech Connect

    Ellingsen, Simon P.; Chen, Xi; Qiao, Hai-Hua; Baan, Willem; An, Tao; Li, Juan; Breen, Shari L.

    2014-08-01

    We have used the Australia Telescope Compact Array to search for emission from the 4{sub –1} → 3{sub 0} E transition of methanol (36.2 GHz) toward the center of the nearby starburst galaxy NGC 253. Two regions of emission were detected, offset from the nucleus along the same position angle as the inner spiral arms. The emission is largely unresolved on a scale of 5'', has a FWHM line width of <30 km s{sup –1}, and an isotropic luminosity orders of a magnitude larger than that observed in any Galactic star formation region. These characteristics suggest that the 36.2 GHz methanol emission is most likely a maser, although observations with higher angular and spectral resolution are required to confirm this. If it is a maser, this represents the first detection of a class I methanol maser outside the Milky Way. The 36.2 GHz methanol emission in NGC 253 has more than an order of magnitude higher isotropic luminosity than the widespread emission recently detected toward the center of the Milky Way. If emission from this transition scales with the nuclear star formation rate, then it may be detectable in the central regions of many starburst galaxies. Detection of methanol emission in ultra-luminous infrared galaxies would open up a new tool for testing for variations in fundamental constants (particularly the proton-to-electron mass ratio) on cosmological scales.

  11. Tick tock the 12.2 GHz methanol masers in G9.62+0.20

    NASA Astrophysics Data System (ADS)

    Gaylard, Michael J.; Goedhart, Sharmila

    2007-03-01

    The bright interstellar methanol masers at 12.2 GHz and 6.7 GHz were discovered in 1987 and 1991 respectively. It was soon established that many were quite variable. Goedhart Gaylard & van der Walt (2003) reported that one source, G9.62+0.20E, exhibited flares at 12.2 and 6.7 GHz that appeared to be periodic, repeating every 246 days. Since then, monitoring of this and other possibly periodic sources has continued with the 26-m Hartebeesthoek telescope. We discuss here the full 12.2 GHz time series data of G9.62+0.20 through 2006. The data quality has been much improved by telescope upgrades. Flares in the main maser peak continue, the repetition rate remains close to that originally determined.

  12. MAJOR STRUCTURES OF THE INNER GALAXY DELINEATED BY 6.7 GHz METHANOL MASERS

    SciTech Connect

    Green, J. A.; Caswell, J. L.; McClure-Griffiths, N. M.; Breen, S. L.; Voronkov, M. A.; Avison, A.; Fuller, G. A.; Gray, M. D.; Burton, M. G.; Ellingsen, S. P.; Pestalozzi, M.

    2011-05-20

    We explore the longitude-velocity distribution of 6.7 GHz methanol masers in the context of the inner structure of our Galaxy. We analyze the correlation in velocities within this distribution and identify density enhancements indicating large-scale regions of enhanced star formation. These are interpreted as the starting points of the spiral arms and the interaction of the Galactic bar with the 3 kpc arms. The methanol masers support the presence of a long thin bar with a 45{sup 0} orientation. Signatures of the full 3 kpc arm structure are seen, including a prominent tangent at approximately -22{sup 0} Galactic longitude. We compare this distribution with existing models of the gas dynamics of our Galaxy. The 3 kpc arm structure appears likely to correspond to the radius of corotation resonance of the bar, with the bar on its inner surface and the starting points of the spiral arms on its outer surface.

  13. Detection of the Zeeman Effect in the 36 GHz Class I Methanol Maser Line with the EVLA

    NASA Astrophysics Data System (ADS)

    Momjian, Emmanuel; Sarma, A. P.

    2010-01-01

    We report the first detection of the Zeeman effect in the 36 GHz Class I methanol maser line. The observations were carried out with 13 antennas of the Expanded Very Large Array (EVLA) equipped with the new 27-40 GHz (Ka-Band) receivers, and targeted the high-mass star-forming region M8E. The detected line of sight magnetic field values are -31.3 ± 3.5 mG and 20.2 ± 3.5 mG to the northwest and southeast of the maser line peak, respectively. These magnetic field values have been derived using a Zeeman splitting factor based on laboratory measurements of the 25 GHz methanol line, since no measurements exist for the 36 GHz line. The change in sign of the magnetic field, as revealed in our observations, is over a size scale of 1300 AU in the source M8E (assuming a distance of 1.5 kpc). This may indicate that the masers are tracing two regions with different magnetic fields, or that the same field curves across the regions where the masers are being excited. The detected fields are not significantly different from the magnetic fields detected in the 6.7 GHz Class II methanol maser line, indicating that these masers may trace the large scale magnetic field, or that the magnetic field remains unchanged during the early evolution of star forming regions. Given what is known about the densities at which 36 GHz methanol masers are excited, we find that the magnetic field is dynamically significant in this star forming region. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

  14. DISCOVERY OF THE ZEEMAN EFFECT IN THE 44 GHz CLASS I METHANOL (CH{sub 3}OH) MASER LINE

    SciTech Connect

    Sarma, A. P.; Momjian, E.

    2011-03-20

    We report the discovery of the Zeeman effect in the 44 GHz Class I methanol (CH{sub 3}OH) maser line. The observations were carried out with 22 antennas of the Expanded Very Large Array toward a star-forming region in OMC-2. Based on our adopted Zeeman splitting factor of z = 1.0 Hz mG{sup -1}, we detect a line-of-sight magnetic field of 18.4 {+-} 1.1 mG toward this source. Since such 44 GHz CH{sub 3}OH masers arise from shocks in the outflows of star-forming regions, we can relate our measurement of the post-shock magnetic field to field strengths indicated by species tracing pre-shock regions, and thus characterize the large-scale magnetic field. Moreover, since Class I masers trace regions more remote from the star-forming core than Class II masers, and possibly earlier phases, magnetic fields detected in 6.7 GHz Class II and 36 and 44 GHz Class I methanol maser lines together offer the potential of providing a more complete picture of the magnetic field. This motivates further observations at high angular resolution to find the positional relationships between Class I and Class II masers, and masers at various frequencies within each category. In particular, CH{sub 3}OH masers are widespread in high- as well as intermediate-mass star-forming regions, and our discovery provides a new method of studying the magnetic field in such regions, by observing small physical scales that are not accessible by any other lines.

  15. Observations of 6.7 GHz methanol masers with East-Asian VLBI Network. II. Internal proper motion measurement in G006.79-00.25

    NASA Astrophysics Data System (ADS)

    Sugiyama, Koichiro; Fujisawa, Kenta; Hachisuka, Kazuya; Yonekura, Yoshinori; Motogi, Kazuhito; Sawada-Satoh, Satoko; Matsumoto, Naoko; Hirano, Daiki; Hayashi, Kyonosuke; Kobayashi, Hideyuki; Kawaguchi, Noriyuki; Shibata, Katsunori M.; Honma, Mareki; Hirota, Tomoya; Murata, Yasuhiro; Doi, Akihiro; Ogawa, Hideo; Kimura, Kimihiro; Niinuma, Kotaro; Chen, Xi; Xia, Bo; Li, Bin; Sorai, Kazuo; Momose, Munetake; Saito, Yu; Takaba, Hiroshi; Omodaka, Toshihiro; Kim, Kee-Tae; Shen, Zhiqiang

    2016-10-01

    We detected internal proper motions of the methanol maser features at 6.7 GHz in a high-mass star-forming region G006.79-00.25 with the East-Asian VLBI Network. The spatial distribution of the maser features shows an elliptical morphology. The internal proper motions of 17 methanol maser features relative to the barycenter of the features were measured. The amplitude of the internal motions ranged from 1.30 to 10.25 km s-1. Most of the internal proper motions of the maser features seem to point counterclockwise along the elliptical morphology of the maser features. We applied the disk model, which includes both rotating and expanding components, to the observed positions, l.o.s. velocities, and proper motions. The derived rotation, expansion, and systemic velocities are +3^{+2}_{-2}, +6^{+2}_{-2}, and +21^{+2}_{-2}km s-1, respectively, at the radius of 1260 au on the disk with a position angle of the semi-major axis of - 140° and an inclination of 60°. The derived rotating motion suggests that the methanol maser emissions showing the elliptical spatial morphology possibly trace the rotating disk. The derived expanding motion might be caused by the magnetic-centrifugal wind on the disk, which was estimated on the basis of the typical magnetic field strength at emitting zones of a methanol maser.

  16. COMPARISON OF TWO EPOCHS OF THE ZEEMAN EFFECT IN THE 44 GHz CLASS I METHANOL (CH{sub 3}OH) MASER LINE IN OMC-2

    SciTech Connect

    Momjian, E.; Sarma, A. P. E-mail: asarma@depaul.edu

    2012-12-01

    We present a second epoch of observations of the 44 GHz Class I methanol maser line toward the star-forming region Orion Molecular Cloud 2. The observations were carried out with the Very Large Array, and constitute one of the first successful Zeeman effect detections with the new Wide-band Digital Architecture correlator. Comparing to the result of our earlier epoch of data for this region, we find that the intensity of the maser increased by 50%, but the magnetic field value has stayed the same, within the errors. This suggests that the methanol maser may be tracing the large-scale magnetic field that is not affected by the bulk gas motions or turbulence on smaller scales that is causing the change in maser intensity.

  17. THE FIRST VERY LONG BASELINE INTERFEROMETRY IMAGE OF A 44 GHz METHANOL MASER WITH THE KVN AND VERA ARRAY (KaVA)

    SciTech Connect

    Matsumoto, Naoko; Hirota, Tomoya; Honma, Mareki; Kameya, Osamu; Sunada, Kazuyoshi; Sugiyama, Koichiro; Motogi, Kazuhito; Kim, Kee-Tae; Kim, Mikyoung; Byun, Do-Young; Jung, Taehyun; Kim, Jongsoo; Lyo, A-Ran; Oh, Chungsik; Bae, Jaehan; Chung, Hyunsoo; Chung, Moon-Hee; Cho, Se-Hyung; Chibueze, James O.; Shino, Nagisa; and others

    2014-07-01

    We have carried out the first very long baseline interferometry (VLBI) imaging of a 44 GHz class I methanol maser (7{sub 0}-6{sub 1} A {sup +}) associated with a millimeter core MM2 in a massive star-forming region IRAS 18151–1208 with KaVA (KVN and VERA Array), which is a newly combined array of KVN (Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry). We have succeeded in imaging compact maser features with a synthesized beam size of 2.7 milliarcseconds × 1.5 milliarcseconds (mas). These features are detected at a limited number of baselines within the length of shorter than ≈ 650 km corresponding to 100 Mλ in the uv-coverage. The central velocity and the velocity width of the 44 GHz methanol maser are consistent with those of the quiescent gas rather than the outflow traced by the SiO thermal line. The minimum component size among the maser features is ∼5 mas × 2 mas, which corresponds to the linear size of ∼15 AU × 6 AU assuming a distance of 3 kpc. The brightness temperatures of these features range from ∼3.5 × 10{sup 8} to 1.0 × 10{sup 10} K, which are higher than the estimated lower limit from a previous Very Large Array observation with the highest spatial resolution of ∼50 mas. The 44 GHz class I methanol maser in IRAS 18151–1208 is found to be associated with the MM2 core, which is thought to be less evolved than another millimeter core MM1 associated with the 6.7 GHz class II methanol maser.

  18. Physical characteristics of bright Class I methanol masers

    NASA Astrophysics Data System (ADS)

    Leurini, S.; Menten, K. M.; Walmsley, C. M.

    2016-07-01

    Context. Class I methanol masers are thought to be tracers of interstellar shock waves. However, they have received relatively little attention mostly as a consequence of their low luminosities compared to other maser transitions. This situation has changed recently and Class I methanol masers are now routinely used as signposts of outflow activity especially in high extinction regions. The recent detection of polarisation in Class I lines now makes it possible to obtain direct observational information about magnetic fields in interstellar shocks. Aims: We make use of newly calculated collisional rate coefficients for methanol to investigate the excitation of Class I methanol masers and to reconcile the observed Class I methanol maser properties with model results. Methods: We performed large velocity gradient calculations with a plane-parallel slab geometry appropriate for shocks to compute the pump and loss rates which regulate the interactions of the different maser systems with the maser reservoir. We study the dependence of the pump rate coefficient, the maser loss rate, and the inversion efficiency of the pumping scheme of several Class I masers on the physics of the emitting gas. Results: We predict inversion in all transitions where maser emission is observed. Bright Class I methanol masers are mainly high-temperature (>100 K) high-density (n(H2) ~ 107-108 cm-3) structures with methanol maser emission measures, ξ, corresponding to high methanol abundances close to the limits set by collisional quenching. Our model predictions reproduce reasonably well most of the observed properties of Class I methanol masers. Class I masers in the 25 GHz series are the most sensitive to the density of the medium and mase at higher densities than other lines. Moreover, even at high density and high methanol abundances, their luminosity is predicted to be lower than that of the 44 GHz and 36 GHz masers. Our model predictions also reflect the observational result that the

  19. A search for water masers associated with class II methanol masers - II. Longitude range 341° to 6°

    NASA Astrophysics Data System (ADS)

    Titmarsh, A. M.; Ellingsen, S. P.; Breen, S. L.; Caswell, J. L.; Voronkov, M. A.

    2016-06-01

    This is the second paper in a series of catalogues of 22-GHz water maser observations towards the 6.7-GHz methanol masers from the Methanol Multibeam (MMB) survey. In this paper, we present our water maser observations made with the Australia Telescope Compact Array towards the masers from the MMB survey between l = 341° through the Galactic Centre to l = 6°. Of the 204 6.7-GHz methanol masers in this longitude range, we found 101 to have associated water maser emission (˜50 per cent). We found no difference in the 6.7-GHz methanol maser luminosities of those with and without water masers. In sources where both maser species are observed, the luminosities of the methanol and water masers are weakly correlated. Studying the mid-infrared colours from GLIMPSE (Galactic Legacy Infrared Midplane Survey Extraordinaire), we found no differences between the colours of those sources associated with both methanol and water masers and those associated with just methanol. Comparing the column density and dust mass calculated from the 870-μm thermal dust emission observed by ATLASGAL (APEX Telescope Large Area Survey of the GALaxy), we found no differences between those sources associated with both water and methanol masers and those with methanol only. Since water masers are collisionally pumped and often show emission further away from their accompanying young stellar object (YSO) than the radiatively pumped 6.7-GHz methanol masers, it is likely that water masers are not as tightly correlated to the evolution of the parent YSO and so do not trace such a well-defined evolutionary state as 6.7-GHz methanol masers.

  20. Statistical properties of the class I methanol masers

    NASA Astrophysics Data System (ADS)

    Voronkov, Maxim; Caswell, James; Sobolev, Andrey; Ellingsen, Simon; Thompson, Mark

    2007-04-01

    We request 6x10.5 hour sessions to image for the first time all known class I methanol masers located at declinations south of -35 deg. at 44 and 36 GHz. These observations will be the first interferometric observations of 36 GHz masers. Using the JCMT HARP-B data on the molecular environment of these masers we plan to search for association with outflows for a large sample of masers. We also plan to test a predicted correlation between the 44 to 36 GHz flux density ratio and the distance from the 6.7 GHz methanol or OH maser using a statistically significant sample. This survey is not sensitivity critical. It is able to deliver publishable results using a partially working or underperforming system, thus being an excellent test before proposing more complex detection experiments at 7mm.

  1. Detection of class I methanol (CH{sub 3}OH) maser candidates in supernova remnants

    SciTech Connect

    Pihlström, Y. M.; Mesler, R. A.; McEwen, B. C.; Sjouwerman, L. O.; Frail, D. A.; Claussen, M. J.

    2014-04-01

    We have used the Karl G. Jansky Very Large Array to search for 36 GHz and 44 GHz methanol (CH{sub 3}OH) lines in a sample of 21 Galactic supernova remnants (SNRs). Mainly the regions of the SNRs with 1720 MHz OH masers were observed. Despite the limited spatial extent covered in our search, methanol masers were detected in both G1.4–0.1 and W28. Additional masers were found in Sgr A East. More than 40 masers were found in G1.4–0.1, which we deduce are due to interactions between the SNR and at least two separate molecular clouds. The six masers in W28 are associated with the molecular cloud that is also associated with the OH maser excitation. We discuss the possibility that the methanol maser may be more numerous in SNRs than the OH maser, but harder to detect due to observational constraints.

  2. A Search for Class I Methanol Masers

    NASA Astrophysics Data System (ADS)

    Pratap, P.

    2001-12-01

    Class I masers are thought to be associated with outflow activity from young stars and are easily explained with a collisional pumping model. However, masers have been found in regions where there is no apparent star formation or outflow activity. These masers could be probing a very early stage of star formation. Most searches for Class I masers have been done toward regions of known star formation. Such searches are biased as they would not find masers offset by distances greater than the telescope beam. The MIT Haystack Observatory Class I methanol maser survey is a project conducted by undergraduate students using the Haystack 37-m telescope. Each student maps a chosen molecular cloud and searches for maser emission. Once the student project is complete the data becomes part of a database of methanol masers. This collaborative observing strategy results in an unbiased search for new sites of methanol maser activity. Currently five clouds have been mapped and several new sites of methanol maser activity have been discovered. This project is funded by the Divisions of Astronomy and Undergraduate Education of the National Science Foundation.

  3. WATER AND METHANOL MASER ACTIVITIES IN THE NGC 2024 FIR 6 REGION

    SciTech Connect

    Choi, Minho; Kang, Miju; Byun, Do-Young; Lee, Jeong-Eun

    2012-11-10

    The NGC 2024 FIR 6 region was observed in the water maser line at 22 GHz and the methanol class I maser lines at 44, 95, and 133 GHz. The water maser spectra displayed several velocity components and month-scale time variabilities. Most of the velocity components may be associated with FIR 6n, while one component was associated with FIR 4. A typical lifetime of the water maser velocity components is about eight months. The components showed velocity fluctuations with a typical drift rate of about 0.01 km s{sup -1} day{sup -1}. The methanol class I masers were detected toward FIR 6. The methanol emission is confined within a narrow range around the systemic velocity of the FIR 6 cloud core. The methanol masers suggest the existence of shocks driven by either the expanding H II region of FIR 6c or the outflow of FIR 6n.

  4. VizieR Online Data Catalog: 6.7GHz methanol maser polarization in SFR (Surcis+, 2015)

    NASA Astrophysics Data System (ADS)

    Surcis, G.; Vlemmings, W. H. T.; van Langevelde, H. J.; Hutawarakorn Kramer, B.; Bartkiewicz, A.; Blasi, M. G.

    2015-09-01

    The first seven massive SFRs were observed at 6.7GHz in full polarization spectral mode with eight of the EVN antennas (Effelsberg, Jodrell, Onsala, Medicina, Noto, Torun, Westerbork, and Yebes-40m) between November 2012 and June 2013, for a total observation time of 49h. The bandwidth was 2MHz, providing a velocity range of ~100km/s. (8 data files).

  5. VizieR Online Data Catalog: Methanol masers towards IRAS sources (van der Walt+ 1995)

    NASA Astrophysics Data System (ADS)

    van der, Walt D. J.; Gaylard, M. J.; MacLeod, G. C.

    1997-04-01

    We present the results of our second search for 6.7-GHz methanol masers towards colour-selected IRAS sources. Five hundred and twenty IRAS sources that meet the far-infrared colour criteria set by Wood & Churchwell (1989ApJ...340..265W) for ultra-compact HII regions were searched for 6.7-GHz methanol maser emission, to a sensitivity limit of 5Jy. Thirty one new maser sources were detected. We also compare the FIR colours of the newly detected maser sources with those detected by Schutte et al. (1993MNRAS.261..783S) and the IRAS counterparts of sources that have both methanol and hydroxyl maser emission. It was found that the average flux distribution of the newly detected sources differs significantly from that of all other known 6.7-GHz methanol maser sources. It is argued that the differences may be due either to intrinsic differences between the three groups of sources or to interstellar extinction. An analysis of the relation between the 6.7-GHz maser and IRAS flux densities shows that the maser flux density is always less than the 100μm flux density while only three sources have a maser flux density greater than the 60μm flux density. Far-infrared pumping of the 6.7-GHz methanol masers is therefore in principle viable although it was found that the apparent maser efficiency will exceed 10 per cent for a significant number of sources in the case of FIR pumping by photons between 50 and 100μm. The overall detection rates on the IRAS [25-12] vs [60-12] two-colour diagram are also presented. Possible new search strategies for masers in colour-selected IRAS sources are discussed. (2 data files).

  6. THE ENVIRONMENT OF THE STRONGEST GALACTIC METHANOL MASER

    SciTech Connect

    Sanna, A.; Menten, K. M.; Carrasco-González, C.; Brunthaler, A.; Reid, M. J.; Ellingsen, S. P.; Krishnan, V.; Moscadelli, L.; Cesaroni, R.

    2015-05-01

    The high-mass star-forming site G009.62+00.20 E hosts the 6.7 GHz methanol maser source with the greatest flux density in the Galaxy which has been flaring periodically over the last 10 yr. We performed high-resolution astrometric measurements of the CH{sub 3}OH, H{sub 2}O, and OH maser emission and 7 mm continuum in the region. The radio continuum emission was resolved in two sources separated by 1300 AU. The CH{sub 3}OH maser cloudlets are distributed along two north–south ridges of emission to the east and west of the strongest radio continuum component. This component likely pinpoints a massive young stellar object which heats up its dusty envelope, providing a constant IR pumping for the Class II CH{sub 3}OH maser transitions. We suggest that the periodic maser activity may be accounted for by an independent, pulsating, IR radiation field provided by a bloated protostar in the vicinity of the brightest masers. We also report the discovery of an elliptical distribution of CH{sub 3}OH maser emission in the region of periodic variability.

  7. Traveling-Wave Maser for 32 GHz

    NASA Technical Reports Server (NTRS)

    Shell, James; Clauss, Robert

    2009-01-01

    The figure depicts a traveling-wave ruby maser that has been designed (though not yet implemented in hardware) to serve as a low-noise amplifier for reception of weak radio signals in the frequency band of 31.8 to 32.3 GHz. The design offers significant improvements over previous designs of 32-GHz traveling-wave masers. In addition, relative to prior designs of 32-GHz amplifiers based on high-electron-mobility transistors, this design affords higher immunity to radio-frequency interference and lower equivalent input noise temperature. In addition to the basic frequency-band and low-noise requirements, the initial design problem included a requirement for capability of operation in a closed-cycle helium refrigerator at a temperature .4 K and a requirement that the design be mechanically simplified, relative to prior designs, in order to minimize the cost of fabrication and assembly. Previous attempts to build 32- GHz traveling-wave masers involved the use of metallic slow-wave structures comprising coupled transverse electromagnetic (TEM)-mode resonators that were subject to very tight tolerances and, hence, were expensive to fabricate and assemble. Impedance matching for coupling signals into and out of these earlier masers was very difficult. A key feature of the design is a slow-wave structure, the metallic portions of which would be mechanically relatively simple in that, unlike in prior slow-wave structures, there would be no internal metal steps, irises, or posts. The metallic portions of the slow-wave structure would consist only of two rectangular metal waveguide arms. The arms would contain sections filled with the active material (ruby) alternating with evanescent-wave sections. This structure would be transparent in both the signal-frequency band (the aforementioned range of 31.8 to 32.3 GHz) and the pump-frequency band (65.75 to 66.75 GHz), and would impose large slowing factors in both frequency bands. Resonant ferrite isolators would be placed in the

  8. DISCOVERY OF 6.035 GHz HYDROXYL MASER FLARES IN IRAS 18566+0408

    SciTech Connect

    Al-Marzouk, A. A.; Araya, E. D.; Hofner, P.; Kurtz, S.; Linz, H.; Olmi, L.

    2012-05-10

    We report the discovery of 6.035 GHz hydroxyl (OH) maser flares toward the massive star-forming region IRAS 18566+0408 (G37.55+0.20), which is the only region known to show periodic formaldehyde (4.8 GHz H{sub 2}CO) and methanol (6.7 GHz CH{sub 3}OH) maser flares. The observations were conducted between 2008 October and 2010 January with the 305 m Arecibo Telescope in Puerto Rico. We detected two flare events, one in 2009 March and one in 2009 September to November. The OH maser flares are not simultaneous with the H{sub 2}CO flares, but may be correlated with CH{sub 3}OH flares from a component at corresponding velocities. A possible correlated variability of OH and CH{sub 3}OH masers in IRAS 18566+0408 is consistent with a common excitation mechanism (IR pumping) as predicted by theory.

  9. The Arecibo Methanol Maser Galactic Plane Survey. II. Statistical and Multiwavelength Counterpart Analysis

    NASA Astrophysics Data System (ADS)

    Pandian, Jagadheep D.; Goldsmith, Paul F.

    2007-11-01

    We present an analysis of the properties of the 6.7 GHz methanol maser sample detected in the Arecibo Methanol Maser Galactic Plane Survey. The distribution of the masers in the Galaxy, and statistics of their multiwavelength counterparts is consistent with the hypothesis of 6.7 GHz maser emission being associated with massive young stellar objects. Using the detection statistics of our survey, we estimate the minimum number of methanol masers in the Galaxy to be 1275. The l-v diagram of the sample shows the tangent point of the Carina-Sagittarius spiral arm to be around 49.6°, and suggests the occurrence of massive star formation along the extension of the Crux-Scutum arm. A Gaussian component analysis of the maser spectra shows the mean line width to be 0.38 km s-1, which is more than a factor of 2 larger than what has been reported in the literature. We also find no evidence that faint methanol masers have different properties than their bright counterparts.

  10. DISCOVERY OF THE FIRST METHANOL (CH{sub 3}OH) MASER IN THE ANDROMEDA GALAXY (M31)

    SciTech Connect

    Sjouwerman, Lorant O.; Murray, Claire E.; Pihlstroem, Ylva M.; Fish, Vincent L.; Araya, Esteban D.

    2010-12-01

    We present the first detection of a 6.7 GHz Class II methanol (CH{sub 3}OH) maser in the Andromeda galaxy (M31). The CH{sub 3}OH maser was found in a VLA survey during the fall of 2009. We have confirmed the methanol maser with the new EVLA, in operation since 2010 March, but were unsuccessful in detecting a water maser at this location. A direct application for this methanol maser is the determination of the proper motion of M31, such as was previously obtained with water masers in M33 and IC10. Unraveling the three-dimensional velocity of M31 would solve for the biggest unknown in the modeling of the dynamics and evolution of the Local Group of galaxies.

  11. Class I methanol masers in low-mass star-forming regions

    NASA Astrophysics Data System (ADS)

    Kalenskii, S. V.; Kurtz, S.; Bergman, P.

    2013-02-01

    Results of observations of Class I methanol masers in regions of low-mass star formation (MMIL) are summarized and analyzed. Four masers were detected at 44, 84, and 95 GHz towards "chemically active" bipolar outflows in the low-mass star-forming regions NGC1333 I4A, NGC 1333 I2A, HH 25, and L1157. Another maser was found at 36 GHz towards a similar outflow in NGC 2023. Thus, all the detected MMILs are associated with chemically active outflows. The brightness temperatures of the strongest 44-GHz maser spots in NGC 1333 I4A, HH 25, and L1157 exceed 2000 K, whereas the brightness temperature in NGC 1333 I2A is only 176 K, although a rotational-diagram analysis shows that this last source is also amaser. The flux densities of the newly detectedmasers are no higher than 18 Jy, and are much lower than those of strong masers in regions of high-mass star formation (MMIH). The MMIL luminosities match the maser luminosity-protostar luminosity relation established earlier for MMIHs. No MMIL variability was detected in 2004-2011. The radial velocities of the newly detected masers are close to the systemic velocities of the associated regions, except for NGC 2023, where the maser radial velocity is lower than the systemic velocity by approximately 3.5 km/s. Thus, the main MMILproperties are similar to those of MMIHs. MMILs are likely to be an extension of the MMIH population toward lower luminosities of both the masers and the associated young stellar objects. The results of VLA observations of MMILs can be explained using a turbulent-cloud model, which predicts that compact maser spots can arise in extended sources because the coherence lengths along some directions randomly appear to be longer than the mean coherence length in a turbulent velocity field. However, one must assume that the column density of methanol towardM1, the strongest maser in L1157, is appreciably higher than the mean column density of the clump B0a where the maser arises. The shape of the maser lines

  12. Class I methanol (CH{sub 3}OH) maser conditions near supernova remnants

    SciTech Connect

    McEwen, Bridget C.; Pihlström, Ylva M.; Sjouwerman, Loránt O.

    2014-10-01

    We present results from calculations of the physical conditions necessary for the occurrence of 36.169 (4{sub –1}-3{sub 0} E), 44.070 (7{sub 0}-6{sub 1} A {sup +}), 84.521 (5{sub –1}-4{sub 0} E), and 95.169 (8{sub 0}-7{sub 1} A {sup +}) GHz methanol (CH{sub 3}OH) maser emission lines near supernova remnants (SNRs), using the MOLPOP-CEP program. The calculations show that given a sufficient methanol abundance, methanol maser emission arises over a wide range of densities and temperatures, with optimal conditions at n ∼ 10{sup 4}-10{sup 6} cm{sup –3} and T > 60 K. The 36 GHz and 44 GHz transitions display more significant maser optical depths compared to the 84 GHz and 95 GHz transitions over the majority of physical conditions. It is also shown that line ratios are an important and applicable probe of the gas conditions. The line ratio changes are largely a result of the E-type transitions becoming quenched faster at increasing densities. The modeling results are discussed using recent observations of CH{sub 3}OH and hydroxyl (OH) masers near the SNRs G1.4–0.1, W28, and Sgr A East.

  13. Methanol Maser Emission in W75N and Orion Molecular Cloud 2 (OMC 2)

    NASA Astrophysics Data System (ADS)

    Goetz, J. A.; Brubaker, D. W.; Clerc, C. A.

    2001-12-01

    We present data of Class I methanol maser emission at 44 GHz centered on two star forming regions, W75N and Orion Molecular Cloud 2 (OMC 2). The Northeast Radio Observatory Corporation (NEROC) Haystack 37-m radio telescope was used to search for emission in the 70 to 61 A+ transition of CH3OH as part of a larger project lead by Dr. Preethi Pratap (MIT Haystack Observatory). This project focuses on detecting maser activity in positions that are offset from known young stellar objects. In addition to detecting the known methanol maser source in each region, a previously undetected maser source was observed to the southwest of W75N IRAS 1.

  14. Experimental evaluation of a ruby maser at 43 GHz

    NASA Technical Reports Server (NTRS)

    Moore, C. R.; Neff, D.

    1982-01-01

    Inversion ratio measurements were conducted at several frequencies between 27 and 43 GHz for a pink ruby material (0.05% Cr/3+/ in Al2O3) at the push-pull pump angle of 54.7 degrees in order to determine the upper frequency limit where pink ruby could be expected to operate as a practical maser amplifier. Based on these measurements, a single-stage maser was developed which yielded 8 + or - 1 dB net gain and a 3 dB bandwidth of 180 MHz at a center frequency of 42.5 GHz. It is concluded that a multistage reflected wave maser could achieve bandwidths exceeding 1 GHz with 30 dB net gain at center frequencies near 40 GHz.

  15. ALMA OBSERVATIONS OF THE IRDC CLUMP G34.43+00.24 MM3: 278 GHz CLASS I METHANOL MASERS

    SciTech Connect

    Yanagida, Takahiro; Sakai, Takeshi; Hirota, Tomoya; Sanhueza, Patricio; Sakai, Nami; Yamamoto, Satoshi; Foster, Jonathan B.; Jackson, James M.; Furuya, Kenji; Aikawa, Yuri

    2014-10-10

    We have observed a molecular clump (MM3) associated with the infrared dark cloud G34.43+00.24 in the CH{sub 3}OH J{sub K}  = 9{sub –1}-8{sub 0} E, 5{sub 0}-4{sub 0} E, and 5{sub –1}-4{sub –1} E lines at sub-arcsecond resolution by using the Atacama Large Millimeter/submillimeter Array. By comparing the CH{sub 3}OH J{sub K}  = 9{sub –1}-8{sub 0} E emission with the CH{sub 3}OH 5{sub 0}-4{sub 0} E and 5{sub –1}-4{sub –1} E emission, we have found that the CH{sub 3}OH J{sub K}  = 9{sub –1}-8{sub 0} E emission is masing. We have clearly shown that the CH{sub 3}OH J{sub K}  = 9{sub –1}-8{sub 0} masers arise from the post shocked gas in the interacting regions between the outflows and ambient dense gas. Toward the strongest peak of the CH{sub 3}OH maser emission, SiO J = 6-5 emission is very weak. This indicates that the CH{sub 3}OH maser emission traces relatively old shocks or weak shocks.

  16. The Revised Version of Class I Methanol Maser Catalog

    NASA Astrophysics Data System (ADS)

    Larionov, G. M.; Litovchenko, I. D.; Val'tts, I. E.; Alakoz, A. V.

    2011-05-01

    The revised version of the class I methanol maser catalog is presented. It contains 198 sources in total. New class I methanol masers detected in the direction of EGOs (38 sources) were added to the previous list containing ˜ 160 sources (the list have been published in the first version of this catalog - see reference in the text). Electronic version of the catalog has been generated in the form of html file - http://www.asc.rssi.ru/MMI. A statistical analysis was carried out within 2' around a maser position to find an identification of class I methanol masers with any objects typical for star-forming regions - UCHII regions, IRAS sources, dark clouds, bipolar outflows, CS lines as of dense gas tracer, and other masers (class II methanol masers, OH and H_2O). Class I methanol masers identification was made with short-wave infrared objects EGO (extended green objects), which are tracers of bipolar outflows in young stellar objects. It was shown that in the new version of catalog more than 50% of class I methanol masers are identified with bipolar outflow - given EGOs as bipolar outflows (compared with the result of 22% in the first version of the catalog that contains no information about EGO). This result is a strong evidence in favor of the fact that EGOs are indeed active bipolar outflows. At the same time it is important to note, that none of the bipolar outflow, already registered in the direction of class I methanol maser, did not coincide with EGO (with the exception of G45.47+0.07). The results are submitted in a form of a diagram.

  17. Theoretical comparison of maser materials for a 32-GHz maser amplifier

    NASA Technical Reports Server (NTRS)

    Lyons, James R.

    1988-01-01

    The computational results of a comparison of maser materials for a 32 GHz maser amplifier are presented. The search for a better maser material is prompted by the relatively large amount of pump power required to sustain a population inversion in ruby at frequencies on the order of 30 GHz and above. The general requirements of a maser material and the specific problems with ruby are outlined. The spin Hamiltonian is used to calculate energy levels and transition probabilities for ruby and twelve other materials. A table is compiled of several attractive operating points for each of the materials analyzed. All the materials analyzed possess operating points that could be superior to ruby. To complete the evaluation of the materials, measurements of inversion ratio and pump power requirements must be made in the future.

  18. Characterizing Supernova Remnant and Molecular Cloud Interaction Sites Using Methanol (CH3OH) Masers

    NASA Astrophysics Data System (ADS)

    McEwen, Bridget; Pihlstrom, Ylva; Sjouwerman, Lorant

    2016-01-01

    Astronomical masers are useful probes of the physical conditions of the gas in which they are formed. Masers form under specific physical conditions and therefore, can be used to trace distinct environments. In particular, collisionally excited 36 and 44 GHz methanol (CH3OH) and 1720 MHz hydroxl (OH) masers are found associated with shocked gas produced by the interaction between supernova remnants (SNRs) and molecular clouds (MCs). The overall goal of my thesis research is to combine modeling and observations to characterize the properties and formation of CH3OH masers in these SNR/MC interaction regions. More accurate information of the density (and density gradients) could, for example, be used as inputs or constraints for models of SNR cosmic ray acceleration. In this talk, I will present results from calculations of the physical conditions necessary for the occurence of 36.169, 44.070, 84.521, and 95.169 GHz CH3OH maser lines near SNRs, using a coupled radiative transfer and level population code. The modeling shows that given a sufficient CH3OH abundance, CH3OH maser emission arises over a wide range of densities and temperatures, with optimal conditions at n ~ 104 to 106 cm-3 and T > 60 K, overlapping with masing conditions for OH masers. Furthermore, the 36 and 44 GHz transitions display more significant maser optical depths compared to the 84 and 95 GHz transitions over the majority of the physical conditions. The line intensity ratios between multiple transitions significantly change with altering physical conditions and can be used to constrain the physical parameters of the gas where CH3OH masers are detected. I use the modeling results as a diagnostic tool to interpret the observational results of a sample of SNRs with previous and recent CH3OH maser detections (G1.4-0.1, W28, Sgr A East, G5.7-0.0, W44 and W51C). I will also discuss the close spatial and kinematic correlation of CH3OH masers and ammonia (NH3 (3,3)) emission peaks, which is a reliable

  19. Finding Short-Term Variability in Methanol Masers

    NASA Astrophysics Data System (ADS)

    Bonin, Samuel; Barott, W. C.; Catanach, T.

    2012-05-01

    The Allen Telescope Array (ATA) performed 53 observations of 6.7 GHz methanol masers between July 2010 and January 2011 in an effort to identify short-timescale variability. With the notable exception of Weisberg et al. (2005), few analyses have been performed analyzing variability in masers on timescales of minutes or less. This work is aimed both at providing additional data (including refined positions) on the catalog of observed sources as well as identifying the prevalence and cause of short-term phenomena. Observations utilized both the ATA correlator (for mapping) and beamformer (for recording voltage time series). A combination of Fast-Fourier Transforms and Continuous Wavelet Transforms are applied to channelized power series waterfalls) in this investigation. Wavelet analysis can be thought of as a generalization of Fourier analysis that allows us to examine non-stationary characteristics of the spectra. The survey included both short (10 minute), long (60 minute), and follow-up observations on candidate targets. Analysis so far has identified three variable sources out of 43 distinct objects that were observed. These objects exhibit significant variation on the order of several minutes, are consistent in follow-up observations, and we have ruled out instrumental variation. Future and ongoing work includes identifying the source of this variation as intrinsic to the source or a property of the ISM. Shorter time-scales will be investigated using a combination of techniques, including total power variation, pulse searching (in an attempt to find pulsars), and phase-shift demodulation techniques. The case for SETI analysis of these data is given, for example, by Cordes (1993), who suggested that extraterrestrial intelligences could use masers to amplify interstellar signals.This project was funded by the National Science Foundation Grant AST0852095. [1] Weisberg J. M. et al. (2005) Science, 309, 5731. [2] Cordes J. M. (1993) Astron. Soc. Pacific Conf. Series

  20. Targeted VLA Observations of 22 GHz Water Masers Towards the Galactic Center

    NASA Astrophysics Data System (ADS)

    Rickert, Matthew; Ott, Juergen; Yusef-Zadeh, Farhad; Meier, David S.

    2015-01-01

    The Central Molecular Zone (CMZ) has a unique environment with a large amount (5 x107 M⊙) of dense (104 cm-3) warm (75-200 K) molecular gas. To probe sites of ongoing star formation in this region, we carried out follow-up VLA observations targeting 22 GHz water masers detected by a recent Mopra survey of the inner 3° x 1° of the Galactic Center (Chambers et al. 2014, A&A 563, A68). We present preliminary results of these measurements with higher angular resolution (2" x 0.9"), spectral resolution (0.2 km s-1), and sensitivity (40 mJy beam-1) and a velocity coverage of -200 to 250 km s-1. A total of 32 maser positions are detected. Several sources display complex spectra with a number of new velocity components. From the 32 maser positions, over 200 spectral features have been identified, indicating clusters of masers. The complex spectra are indicative of young (< 105 years) star forming regions, with some of the components likely being produced from outflows. The brightest component is over 500 Jy beam-1 towards the HII region G359.14+0.03 with a vLSR of -9 km s-1. The most prominent location of water masers is the star forming region Sgr B2, where over 80 spectral components are identified from 9 different positions with peak flux densities ranging from 0.8 to 142 Jy beam-1. Three of these positions contain enhanced 4.5 μm green extended sources, indicating these masers are likely associated with outflows. Sgr C contains 3 separate maser positions with a total of 4 spectral components ranging from -70 to -66 km s-1 and peak flux densities of 4 to 15 Jy beam-1. One of these positions is also associated with a green source. We will compare the water maser positions with positions of radiatively pumped 6.7 GHz methanol masers and other green (3-8 μm) sources. This comparison will be used to verify that star formation is the underlying source of these masers and to identify masers associated with outlfows.

  1. Discovery of periodic and alternating flares of the methanol and water masers in G107.298+5.639

    NASA Astrophysics Data System (ADS)

    Szymczak, M.; Olech, M.; Wolak, P.; Bartkiewicz, A.; Gawroński, M.

    2016-06-01

    Methanol and water vapour masers are signposts of early stages of high-mass star formation but it is generally thought that due to different excitation processes they probe distinct parts of stellar environments. Here we present observations of the intermediate-mass young stellar object G107.298+5.639, revealing for the first time that 34.4 d flares of the 6.7 GHz methanol maser emission alternate with flares of individual features of the 22 GHz water maser. High angular resolution data reveal that a few components of both maser species showing periodic behaviour coincide in position and velocity and all the periodic water maser components appear in the methanol maser region of size of 360 au. The maser flares could be caused by variations in the infrared radiation field induced by cyclic accretion instabilities in a circumstellar or protobinary disc. The observations do not support either the stellar pulsations or the seed photon flux variations as the underlying mechanisms of the periodicity in the source.

  2. Massive Molecular Outflows Toward Methanol Masers: by Eye and Machine Learning

    NASA Astrophysics Data System (ADS)

    de Villiers, Helena

    2013-07-01

    The best known evolutionary state of massive stars is that of the UC HII region, occurring a few 10^5 years after the initial formation of a massive YSO. Currently objects in the "hot core" phase, occurring prior to the UC HII region, are studied with great interest. Because the YSO is still supposed to be accreting at this stage, one would expect outflows from the central object to develop during this phase, entraining surrounding cold molecular gas in their wake. During this time, 6.7 GHz (Class II) methanol masers will also turn on. They are uniquely associated with massive YSO's, thus serve as a useful signpost. We searched for molecular outflows with the JCMT and HARP focal plane array in a sample of targets toward 6.7 GHz methanol maser coordinates within 20 < Glon < 34. We found 58 CO clumps but only 47 of them were closely associated with the methanol masers. Their spectra were analyzed for broadened line wings, which were found to be present in 46 of the spectra, indicating either bi- or mono-polar outflows. This is a 98% detection frequency. The velocity ranges of these spectrum wings were used to create two dimensional blue and red maps. The out flows' physical parameters were calculated and compared with literature. We created a catalog of kinematic distances and properties of all the 13CO outflows associated with Class II methanol masers, as well as their associated H_2 core and virial masses as derived from the C18O data. In the the light of our results we emphasize the need for an automated detection process, especially with the increasing number of wide-area surveys. We are currently exploring the use of machine learning algorithms (specifically Support Vector Machines) in the detection of high velocity structures in p-p-v cubes.

  3. Instrumental and Observational Studies in Radio Astronomy, Low Noise Amplifier Design and Methanol Maser Research

    NASA Astrophysics Data System (ADS)

    Minier, V.

    1998-10-01

    ``Radio astronomy is the study of the universe by observing electromagnetic radiation after it has been amplified. The use of amplifiers that preserve the oscillatory character of radiation - the phase information - is the mark of Radio astronomy.'' Thus, the development of low noise amplifiers for microwave and millimeter wavelengths is a major part of Radio astronomy as important as the observations themselves. This technical report involves those two aspects of Radio astronomy, the observational and technical aspects. In the first part, observations of methanol masers in massive star forming regions using Very Long Baseline Interferometry (VLBI) are presented. The second part concerns the realization of low noise amplifiers using in a radio camera. Recent observations have confirmed that the methanol masers are powerful tools for probing the regions of massive star formation. The methanol masers fall in two distinct classes related to their location in the star forming regions. Class I methanol masers are observed offset far away from the UC HII region emission peak. They are certainly collisionally pumped and may occur in the interface between high velocity gas outflows and the ambient molecular material. Class II methanol masers coincide with the UC HII region emission. They may be radiatively pumped by FIR radiation from the dust grains and reside either in spherical layers surrounding the UC HII regions or in circumstellar discs. The maser spots are usually compact (~1-10 AU) and lie in region of physical conditions n(H)~104-108 cm-3 and T=100-1000 K. CH3OH may be produced by hydrogenation of CO on the surface of the icy mantles of the dust grains . The methanol is then injected in the molecular gas by evaporation of the ice (n(H)=106 cm-3, T=100-300 K). In this report we present VLBI observations of 6.7 and 12.2 GHz methanol masers in the star forming regions NGC7538, W75N and S252. Our results show the existence of two groups of masers in NGC7538. The

  4. Annular-beam, 17 GHz free-electron maser experiment

    SciTech Connect

    Earley, L.M.; Carlsten, B.E.; Fazio, M.V.

    1997-06-01

    Experiments have been conducted on a 15-17 GHz free electron maser (FEM) for producing a 500 MW output pulse with a phase stability appropriate for linear collider applications. The electron beam source was a 1 {mu}s, 800 kV, 5 kA, 6-cm-dia annular electron beam machine called BANSHEE. The beam interacted with the TM{sub 02} and TM{sub 03} mode Raman FEM amplifier in a corrugated cylindrical waveguide where the beam runs close to the interaction device walls to reduce the power density in the fields. This greatly reduced the kinetic energy loss caused by the beam potential depression associated with the space charge which was a significant advantage in comparison with conventional solid beam microwave tubes at the same beam current. The experiment was operated in a single shot mode with a large number of diagnostics to measure power, frequency and energy.

  5. A 32-GHz reflected-wave maser amplifier with wide instantaneous bandwidth

    NASA Technical Reports Server (NTRS)

    Shell, J.; Neff, D.

    1988-01-01

    An eight stage, 32 GHz reflected wave ruby maser was built. The maser operates in a 3 watt closed cycle refrigerator at 4.5 K and is capable of 21 dB of net gain with an instantaneous bandwidth of 400 MHz. The input noise temperature referred to the room temperature flange is approximately 21 K.

  6. TESTING THE HYPOTHESIS THAT METHANOL MASER RINGS TRACE CIRCUMSTELLAR DISKS: HIGH-RESOLUTION NEAR-INFRARED AND MID-INFRARED IMAGING

    SciTech Connect

    De Buizer, James M.; Bartkiewicz, Anna; Szymczak, Marian

    2012-08-01

    Milliarcsecond very long baseline interferometry maps of regions containing 6.7 GHz methanol maser emission have lead to the recent discovery of ring-like distributions of maser spots and the plausible hypothesis that they may be tracing circumstellar disks around forming high-mass stars. We aimed to test this hypothesis by imaging these regions in the near- and mid-infrared at high spatial resolution and compare the observed emission to the expected infrared morphologies as inferred from the geometries of the maser rings. In the near-infrared we used the Gemini North adaptive optics system of ALTAIR/NIRI, while in the mid-infrared we used the combination of the Gemini South instrument T-ReCS and super-resolution techniques. Resultant images had a resolution of {approx}150 mas in both the near-infrared and mid-infrared. We discuss the expected distribution of circumstellar material around young and massive accreting (proto)stars and what infrared emission geometries would be expected for the different maser ring orientations under the assumption that the masers are coming from within circumstellar disks. Based upon the observed infrared emission geometries for the four targets in our sample and the results of spectral energy distribution modeling of the massive young stellar objects associated with the maser rings, we do not find compelling evidence in support of the hypothesis that methanol masers rings reside in circumstellar disks.

  7. A Search for Submillimeter H2O Masers in Active Galaxies: The Detection of 321 GHZ H2O Maser Emission in NGC 4945

    NASA Astrophysics Data System (ADS)

    Hagiwara, Yoshiaki; Horiuchi, Shinji; Doi, Akihiro; Miyoshi, Makoto; Edwards, Philip G.

    2016-08-01

    We present further results of a search for extragalactic submillimeter H2O masers using the Atacama Large Millimeter/submillimeter Array (ALMA). The detection of a 321 GHz H2O maser in the nearby type 2 Seyfert galaxy, the Circinus galaxy, has previously been reported, and here the spectral analysis of four other galaxies is described. We have discovered H2O maser emission at 321 GHz toward the center of NGC 4945, a nearby type 2 Seyfert. The maser emission shows Doppler-shifted velocity features with velocity ranges similar to those of the previously reported 22 GHz H2O masers however, the non-contemporaneous observations also show differences in velocity offsets. The subparsec-scale distribution of the 22 GHz H2O masers revealed by earlier very long baseline interferometry observations suggests that the submillimeter masers could arise in an edge-on rotating disk. The maser features remain unresolved by the synthesized beam of ˜0.″54 (˜30 pc) and are located toward the 321 GHz continuum peak within errors. A marginally detected (3σ) high-velocity feature is redshifted by 579 km {{{s}}}-1 with respect to the systemic velocity of the galaxy. Assuming that this feature is real and arises from a Keplerian rotating disk in this galaxy, it is located at a radius of ˜0.020 pc (˜1.5 × 105 Schwarzschild radii), which would enable molecular material closer to the central engine to be probed than the 22 GHz H2O masers. This detection confirms that submillimeter H2O masers are a potential tracer of the circumnuclear regions of active galaxies, which will benefit from higher angular resolution studies with ALMA.

  8. A Search for Submillimeter H2O Masers in Active Galaxies: The Detection of 321 GHZ H2O Maser Emission in NGC 4945

    NASA Astrophysics Data System (ADS)

    Hagiwara, Yoshiaki; Horiuchi, Shinji; Doi, Akihiro; Miyoshi, Makoto; Edwards, Philip G.

    2016-08-01

    We present further results of a search for extragalactic submillimeter H2O masers using the Atacama Large Millimeter/submillimeter Array (ALMA). The detection of a 321 GHz H2O maser in the nearby type 2 Seyfert galaxy, the Circinus galaxy, has previously been reported, and here the spectral analysis of four other galaxies is described. We have discovered H2O maser emission at 321 GHz toward the center of NGC 4945, a nearby type 2 Seyfert. The maser emission shows Doppler-shifted velocity features with velocity ranges similar to those of the previously reported 22 GHz H2O masers however, the non-contemporaneous observations also show differences in velocity offsets. The subparsec-scale distribution of the 22 GHz H2O masers revealed by earlier very long baseline interferometry observations suggests that the submillimeter masers could arise in an edge-on rotating disk. The maser features remain unresolved by the synthesized beam of ˜0.″54 (˜30 pc) and are located toward the 321 GHz continuum peak within errors. A marginally detected (3σ) high-velocity feature is redshifted by 579 km {{{s}}}-1 with respect to the systemic velocity of the galaxy. Assuming that this feature is real and arises from a Keplerian rotating disk in this galaxy, it is located at a radius of ˜0.020 pc (˜1.5 × 105 Schwarzschild radii), which would enable molecular material closer to the central engine to be probed than the 22 GHz H2O masers. This detection confirms that submillimeter H2O masers are a potential tracer of the circumnuclear regions of active galaxies, which will benefit from higher angular resolution studies with ALMA.

  9. THE FIRST DETECTION OF THE 232 GHz VIBRATIONALLY EXCITED H{sub 2}O MASER IN ORION KL WITH ALMA

    SciTech Connect

    Hirota, Tomoya; Kim, Mi Kyoung; Honma, Mareki

    2012-09-20

    We investigated the ALMA science verification data of Orion KL and found a spectral signature of the vibrationally excited H{sub 2}O maser line at 232.68670 GHz ({nu}{sub 2} = 1, 5{sub 5,0}-6{sub 4,3}). This line has been detected previously in circumstellar envelopes of late-type stars but not in young stellar objects such as Orion KL. Thus, this is the first detection of the 232 GHz vibrationally excited H{sub 2}O maser in star-forming regions. The distribution of the 232 GHz maser is concentrated at the position of the radio Source I, which is remarkably different from other molecular lines. The spectrum shows a double-peak structure at the peak velocities of -2.1 and 13.3 km s{sup -1}. It appears to be consistent with the 22 GHz H{sub 2}O masers and 43 GHz SiO masers observed around Source I. Thus, the 232 GHz H{sub 2}O maser around Source I would be excited by the internal heating by an embedded protostar, being associated with either the root of the outflows/jets or the circumstellar disk around Source I, as traced by the 22 GHz H{sub 2}O masers or 43 GHz SiO masers, respectively.

  10. Excited-state hydroxyl maser catalogue from the methanol multibeam survey - I. Positions and variability

    NASA Astrophysics Data System (ADS)

    Avison, A.; Quinn, L. J.; Fuller, G. A.; Caswell, J. L.; Green, J. A.; Breen, S. L.; Ellingsen, S. P.; Gray, M. D.; Pestalozzi, M.; Thompson, M. A.; Voronkov, M. A.

    2016-09-01

    We present the results of the first complete unbaised survey of the Galactic plane for 6035-MHz excited-state hydroxyl (ex-OH) masers undertaken as part of the methanol multibeam (MMB) survey. These observations cover the Galactic longitude ranges 186° < l < 60° including the Galactic Centre. We report the detection of 127 ex-OH masers within the survey region, 47 being new sources. The positions of new detections were determined from interferometric observations with the Australia Telescope Compact Array. We discuss the association of 6035-MHz masers in our survey with the 6668-MHz masers from the MMB Survey, finding 37 likely CH3OH-ex-OH maser pairs with physical separations of ≤0.03 pc and 55 pairings separated by ≤0.1 pc. Using these we calculate for the first time an ex-OH maser lifetime of between 3.3 × 103 and 8.3 × 103 yr. We also discuss the variability of the 6035-MHz masers and detection rates of counterpart 6030-MHz ex-OH masers (28 per cent of our sample having detection at both frequencies).

  11. A 2.3-GHz maser at Usuda, Japan, for TDRSS-orbiting VLBI experiment

    NASA Technical Reports Server (NTRS)

    Quinn, R. B.

    1988-01-01

    A 2.3 GHz traveling-wave maser/closed-cycle refrigerator (TWM/CCR) that is used in the DSN was installed and successfully operated on the 64 m antenna at Usuda, Japan. The TWM/CCR supported the first very long baseline interferometry (VLBI) experiment to use an orbiting spacecraft as one of the receiving antennas. The experiment required a 15 K receiving system over a 2271 to 2285 MHz bandwidth. The maser installation was made during June 1986, and successful VLBI measurements were made during July and August 1986 and again in January 1987.

  12. METHANOL MASER EMISSION FROM GALACTIC CENTER SOURCES WITH EXCESS 4.5 {mu}m EMISSION

    SciTech Connect

    Chambers, E. T.; Yusef-Zadeh, F.; Roberts, D. E-mail: zadeh@northwestern.edu

    2011-05-20

    We present a study of signatures of on-going star formation in a sample of protostellar objects with enhanced 4.5 {mu}m emission ('green' sources) near the Galactic center. To understand how star formation in the Galactic center region compares to that of the Galactic disk, we used the Expanded Very Large Array to observe radiatively excited Class II 6.7 GHz CH{sub 3}OH masers and collisionally excited Class I 44 GHz CH{sub 3}OH masers, both tracers of high-mass star formation, toward a sample of 34 Galactic center and foreground 'green' sources. We find that 33% {+-} 15% of Galactic center sources are coincident with 6.7 GHz masers, and that 44% {+-} 17% of foreground sources are coincident with 6.7 GHz masers. For 44 GHz masers, we find correlation rates of 27% {+-} 13% and 25% {+-} 13% for Galactic center green sources and foreground green sources, respectively. Based on these CH{sub 3}OH maser detection rates, as well as correlations of green sources with other tracers of star formation, such as 24 {mu}m emission and infrared dark clouds (IRDCs), we find no significant difference between the green sources in the Galactic center and those foreground to it. This suggests that once the star formation process has begun, the environmental differences between the Galactic center region and the Galactic disk have little effect on its observational signatures. We do find, however, some evidence that may support a recent episode of star formation in the Galactic center region.

  13. Search for the 22 GHz water maser emission in selected comets

    NASA Astrophysics Data System (ADS)

    Cosmovici, C. B.; Pluchino, S.; Montebugnoli, S.; Pogrebenko, S.

    2014-06-01

    Following the first evidence of planetary water maser emission induced by the collision of comet Shoemaker/Levy with Jupiter and the puzzling detection of the 22 GHz water emission line in Comet Hyakutake we started in the period 2002-2008 systematic observations of selected comets at 22 GHz (1.35 cm) with the aim of clarifying the unusual behavior of the maser line in the cometary “scenario”. Using a fast multichannel spectrometer coupled to the 32 m dish of the Medicina (Bologna, Italy) Radio Telescope we investigated 6 bright or sungrazing comets down to a heliocentric distance of 0.11 AU: 96P/Machholz, 153P/ Ikeya-Zhang, C/2002 V1 (NEAT), C/2002 X5 (Kudo-Fujikawa), C/2002 T7 (Linear), and 73P/Schwassmann-Wachmann 3. All of them, similarly to Comet Hyakutake, demonstrate spectral features that, if real and due to the 1.35 cm water vapor transition, are strongly (up to tens of km/s) shifted relative to the radial velocity of the nucleus and, at least sometimes, seem to be present as two separate peaks. If our interpretation of these spectral peaks is correct, there must be some mechanism of acceleration of neutral water molecules up to the velocities of ions. We discuss here the results achieved and the possible explanation of the chemo-physical constraints. First possible detection of the water maser emission line at 22 GHz in sun-grazing comets Observed puzzling acceleration of neutral water molecules at ion velocities and split of the line in two components. Evidence of plasma-grain interaction in sun-grazing comets. Possible new detections in six peculiar comets.

  14. Design of an induction linac driven CARM (Cyclotron Auto Resonance Maser) oscillator at 250 GHz

    SciTech Connect

    Caplan, M.; Kulke, B.

    1990-01-24

    We present the design of a 250 GHz, 400 MW Cyclotron Auto Resonance Maser (CARM) oscillator driven by a 1 KA, 2 MeV electron beam produced by the induction linac at the ARC facility of LLNL. The oscillator circuit is designed as a feedback amplifier operating in the TE{sub 11} mode at ten times cutoff terminated at each end with Bragg reflectors. Theory and cold test results are in good agreement for a manufactured Bragg reflector using 50 {mu}m corrugations to ensure mode purity. The CARM is to be operational by February 1990. 3 figs., 2 tabs.

  15. A 250-GHz CARM (Cyclotron Auto Resonance Maser) oscillator experiment driven by an induction linac

    SciTech Connect

    Caplan, M.; Kulke, B.; Bubp, D.G. ); McDermott, D.; Luhmann, N. )

    1990-09-14

    A 250-GHz Cyclotron Auto Resonance Maser (CARM) oscillator has been designed and constructed and will be tested using a 1-kA, 2-MeV electron beam produced by the induction linac at the Accelerator Research Center (ARC) facility of Lawrence Livermore National Laboratory (LLNL). The oscillator circuit was made to operate in the TE{sub 11} mode at ten times cutoff using waveguide Bragg reflectors to create an external cavity Q of 8000. Theory predicts cavity fill times of less than 30 ns (pulse length) and efficiencies approaching 20% is sufficiently low transverse electron velocity spreads are maintained (2%).

  16. Observacoes do Cometa de Halley no Continuo de 22 GHz E 44 GHz, E NA Raia Maser de Vapor de H20 EM 22.2 GHz

    NASA Astrophysics Data System (ADS)

    Abraham, Z.; Scalise, E., Jr.; Botti, L. C. L.; Cancoro, A. C. O.; Monteiro Do Vale, J. L.; del Ciampo, L. F.; Tateyama, C. E.; Vilas Boas, J. W. S.; Homor, J. L.; Kaufmann, P.

    1987-05-01

    0 cometa de Halley foi observado no contínuo nas frequencias de 22 GHz e 44 GHz no Observatório de Itapetinga, Brasil, no período Fevereiro-Abril de 1986. 0 cometa foi detetado em ambas frequẽncias, apresentando variabilidade corn escalas de tempo de horas. Cálculos teóricos mostram que a radicão não pode ser devida a transicões livre-livre na região ionizada resultante da interacão do cometa corn 0 vento solar. A emissão seria então devida à radiacão térmica dos gráos da coma do cometa, cuja densidade também foi variável em intervalo de horas. Não foi detetada emissão maser de H2O maior que 4 Jy.

  17. DETECTION OF THE ZEEMAN EFFECT IN THE 36 GHz CLASS I CH{sub 3}OH MASER LINE WITH THE EVLA

    SciTech Connect

    Sarma, A. P.; Momjian, E.

    2009-11-10

    We report the first detection of the Zeeman effect in the 36 GHz Class I CH{sub 3}OH maser line. The observations were carried out with 13 antennas of the EVLA toward the high mass star-forming region M8E. Based on our adopted Zeeman splitting factor of z = 1.7 Hz mG{sup -1}, we detect a line-of-sight magnetic field of -31.3 +- 3.5 mG and 20.2 +- 3.5 mG to the northwest and southeast of the maser line peak, respectively. This change in sign over a 1300 AU size scale may indicate that the masers are tracing two regions with different fields, or that the same field curves across the regions where the masers are being excited. The detected fields are not significantly different from the magnetic fields detected in the 6.7 GHz Class II CH{sub 3}OH maser line, indicating that CH{sub 3}OH masers may trace the large-scale magnetic field, or that the magnetic field remains unchanged during the early evolution of star-forming regions. Given what is known about the densities at which 36 GHz CH{sub 3}OH masers are excited, we find that the magnetic field is dynamically significant in the star-forming region.

  18. G 10.472+0.027: AN EXTREME WATER MASER OUTFLOW ASSOCIATED WITH A MASSIVE PROTOSTELLAR CLUSTER

    SciTech Connect

    Titmarsh, A. M.; Ellingsen, S. P.; Breen, S. L.; Caswell, J. L.; Voronkov, M. A.

    2013-09-20

    An Australia Telescope Compact Array search for 22 GHz water masers toward 6.7 GHz class II methanol masers detected in the Methanol Multibeam survey has resulted in the detection of extremely high-velocity emission from one of the sources. The water maser emission associated with this young stellar object covers a velocity span of nearly 300 km s{sup –1}. The highest velocity water maser emission is redshifted from the systemic velocity by 250 km s{sup –1}, which is a new record for high-mass star formation regions. The maser is associated with a very young late O, or early B star, which may still be actively accreting matter (and driving the extreme outflow). If that is the case, future observations of the kinematics of this water maser will provide a unique probe of accretion processes in the highest mass young stellar objects and test models of water maser formation.

  19. The structure of methanol radio sources in star-forming regions from observations at 44 and 95 GHz

    NASA Astrophysics Data System (ADS)

    Kalenskij, S. V.

    1995-08-01

    A simple analytical model for excitation of methanol is developed. It is shown that Class I methanol sources may occur near the boundaries of dense gas-dust clouds. Masres at the transition 8(0)-7(1)A(+) of comparable intensity with masers at the transition 7(0)-6(1)A(+) are possible only when the kinetic temperature is no less than 30 K. Cavities formed by high-velocity streams facilitate the occurrence of masers; it is possible that this is one of the reasons for the link between methanol masers and high-velocity flows of material. It is possible that the radiation field close to young stars 'moves aside' Class I masers to some distance from the stars.

  20. Excitation of the 51 - 60 A+ Methanol Transition

    NASA Astrophysics Data System (ADS)

    Kuiper, T. B. H.; Goldsmith, P.; de Gregorio Monsalvo, I.; Kalensky, S.; Peng, R.; Slysh, V.

    2009-01-01

    We are conducting an investigation of the excitation of the 6.7 GHz methanol maser line to determine the physical conditions that produce the inversion in this strongest of methanol masers. We have observed the ΔJ = -1, ΔK = 0 transitions at 290.1, 287.7 and 239.7 GHz, which connect to the levels of the maser line, towards a sample of strong Class II masers. The observations of the 51-41 A+ line at 239.7 GHz and 60-50 A+ line at 290.1 GHz make it possible to determine the relative populations (excitation temperature) of the 6.7 GHz maser levels. The derived excitation temperatures for the maser line, averaged over the 30" CSO beam, are in most cases positive. The lack of inversion suggests that the beam averages over regions with quasi-thermal and maser emission and that the regions which are inverted are much smaller than the CSO beam. A map of the W51 region in thermal methanol lines shows that the strongest masers occur at or near the peak of thermal methanol emission which indicates a correlation between methanol column density and maser intensity. We plan also to map the Orion OMC-1 region, where the mm emission is intense but the 6.7 GHz emission fairly weak and, interestingly, extended. The DR21 region also has mm emission strong enough to be mapped in reasonable time. Our colleague and friend Slava Slysh passed away in September. We miss his inspiring insights and dedicate this work to his memory. The work by TBHK and PFG was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract to the National Aeronautics and Space Administration.

  1. Astrometrically registered simultaneous observations of the 22 GHz H{sub 2}O and 43 GHz SiO masers toward R Leonis Minoris using KVN and source/frequency phase referencing

    SciTech Connect

    Dodson, Richard; Rioja, María J.; Jung, Tae-Hyun; Sohn, Bong-Won; Byun, Do-Young; Cho, Se-Hyung; Lee, Sang-Sung; Kim, Jongsoo; Kim, Kee-Tae; Oh, Chung-Sik; Han, Seog-Tae; Je, Do-Heung; Chung, Moon-Hee; Wi, Seog-Oh; Kang, Jiman; Lee, Jung-Won; Chung, Hyunsoo; Kim, Hyo-Ryoung; Kim, Hyun-Goo; Lee, Chang-Hoon; and others

    2014-11-01

    Oxygen-rich asymptotic giant branch (AGB) stars can be intense emitters of SiO (v = 1 and 2, J = 1 → 0) and H{sub 2}O maser lines at 43 and 22 GHz, respectively. Very long baseline interferometry (VLBI) observations of the maser emission provide a unique tool to probe the innermost layers of the circumstellar envelopes in AGB stars. Nevertheless, the difficulties in achieving astrometrically aligned H{sub 2}O and v = 1 and v = 2 SiO maser maps have traditionally limited the physical constraints that can be placed on the SiO maser pumping mechanism. We present phase-referenced simultaneous spectral-line VLBI images for the SiO v = 1 and v = 2, J = 1 → 0, and H{sub 2}O maser emission around the AGB star R LMi, obtained from the Korean VLBI Network (KVN). The simultaneous multi-channel receivers of the KVN offer great possibilities for astrometry in the frequency domain. With this facility, we have produced images with bona fide absolute astrometric registration between high-frequency maser transitions of different species to provide the positions of the H{sub 2}O maser emission and the center of the SiO maser emission, hence reducing the uncertainty in the proper motions for R LMi by an order of magnitude over that from Hipparcos. This is the first successful demonstration of source frequency phase referencing for millimeter VLBI spectral-line observations and also where the ratio between the frequencies is not an integer.

  2. The Methanol Multibeam Survey

    NASA Astrophysics Data System (ADS)

    Green, James A.; Cohen, R. J.; Caswell, J. L.; Fuller, G. A.; Brooks, K.; Burton, M. G.; Chrysostomou, A.; Diamond, P. J.; Ellingsen, S. P.; Gray, M. D.; Hoare, M. G.; Masheder, M. R. W.; McClure-Griffiths, N.; Pestalozzi, M.; Phillips, C.; Quinn, L.; Thompson, M. A.; Voronkov, M.; Walsh, A.; Ward-Thompson, D.; Wong-McSweeney, D.; Yates, J. A.; Cox, J.

    2007-03-01

    A new 7-beam methanol multibeam receiver is being used to survey the Galaxy for newly forming massive stars, that are pinpointed by strong methanol maser emission at 6.668 GHz. The receiver, jointly constructed by Jodrell Bank Observatory (JBO) and the Australia Telescope National Facility (ATNF), was successfully commissioned at Parkes in January 2006. The Parkes-Jodrell survey of the Milky Way for methanol masers is two orders of magnitude faster than previous systematic surveys using 30-m class dishes, and is the first systematic survey of the entire Galactic plane. The first 53 days of observations with the Parkes telescope have yielded 518 methanol sources, of which 218 are new discoveries. We present the survey methodology as well as preliminary results and analysis.

  3. Accurate maser positions for MALT-45

    NASA Astrophysics Data System (ADS)

    Jordan, Christopher; Bains, Indra; Voronkov, Maxim; Lo, Nadia; Jones, Paul; Muller, Erik; Cunningham, Maria; Burton, Michael; Brooks, Kate; Green, James; Fuller, Gary; Barnes, Peter; Ellingsen, Simon; Urquhart, James; Morgan, Larry; Rowell, Gavin; Walsh, Andrew; Loenen, Edo; Baan, Willem; Hill, Tracey; Purcell, Cormac; Breen, Shari; Peretto, Nicolas; Jackson, James; Lowe, Vicki; Longmore, Steven

    2013-10-01

    MALT-45 is an untargeted survey, mapping the Galactic plane in CS (1-0), Class I methanol masers, SiO masers and thermal emission, and high frequency continuum emission. After obtaining images from the survey, a number of masers were detected, but without accurate positions. This project seeks to resolve each maser and its environment, with the ultimate goal of placing the Class I methanol maser into a timeline of high mass star formation.

  4. Accurate maser positions for MALT-45

    NASA Astrophysics Data System (ADS)

    Jordan, Christopher; Bains, Indra; Voronkov, Maxim; Lo, Nadia; Jones, Paul; Muller, Erik; Cunningham, Maria; Burton, Michael; Brooks, Kate; Green, James; Fuller, Gary; Barnes, Peter; Ellingsen, Simon; Urquhart, James; Morgan, Larry; Rowell, Gavin; Walsh, Andrew; Loenen, Edo; Baan, Willem; Hill, Tracey; Purcell, Cormac; Breen, Shari; Peretto, Nicolas; Jackson, James; Lowe, Vicki; Longmore, Steven

    2013-04-01

    MALT-45 is an untargeted survey, mapping the Galactic plane in CS (1-0), Class I methanol masers, SiO masers and thermal emission, and high frequency continuum emission. After obtaining images from the survey, a number of masers were detected, but without accurate positions. This project seeks to resolve each maser and its environment, with the ultimate goal of placing the Class I methanol maser into a timeline of high mass star formation.

  5. VizieR Online Data Catalog: Distances towards 6.7GHz methanol masers (Pandian+, 2008)

    NASA Astrophysics Data System (ADS)

    Pandian, J. D.; Momjian, E.; Goldsmith, P. F.

    2008-09-01

    The observations were made in June 2005 using the C-Band receiver of Green Bank Telescope. The GBT spectrometer was used in 16 intermediate frequency (IF) mode to cover 8 frequencies in two polarizations. (1 data file).

  6. VizieR Online Data Catalog: Methanol maser associated outflows (de Villiers+, 2014)

    NASA Astrophysics Data System (ADS)

    de Villiers, H. M.; Chrysostomou, A.; Thompson, M. A.; Ellingsen, S. P.; Urquhart, J. S.; Breen, S. L.; Burton, M. G.; Csengeri, T.; Ward-Thompson, D.

    2015-04-01

    The targets were observed with the JCMT, on the summit of Mauna Kea, Hawaii on seven nights between 2007 May 17 and 2008 July 22. Targets were mapped in the 13CO and C18O (J=3-2) transitions (330.6 and 329.3GHz), using the 16-receptor HARP. (5 data files).

  7. An unbiased pilot survey for Galactic water masers

    NASA Astrophysics Data System (ADS)

    Caswell, J. L.; Breen, S. L.

    2010-10-01

    The Australia Telescope Compact Array has been used in a fast surveying mode to study the 22-GHz transition of water in two small sample regions of the southern Galactic plane. The observations allow an unbiased search for water masers, including any that may have no association with masers from other molecules (or indeed, no association with any other detectable celestial object). Positions with arcsecond accuracy were obtained from the original survey data for detected sources, and these were re-observed at an epoch more than two years later. Variability of the spectra between the epochs was considerable: our total of 32 masers comprises 24 detected at both epochs, two detected at only the first epoch and six detected at only the follow-up epoch. The success of our surveying mode shows it to be a practical strategy for the difficult task of extending unbiased water maser surveys to a large portion of the Galactic plane. Our results show quantitatively the effect of variability on the completeness of surveys conducted at a single epoch. Most of our maser detections are new discoveries. Only four had previously been detected (in searches towards interesting targets in the survey area). The high density of water masers from our unbiased survey supports earlier suggestions that they are the most populous maser species, and one of the most sensitive and reliable tracers of massive young stellar objects - newly forming massive young stars. The spectra of nine masers show high-velocity emission, and they show a striking preponderance of blueshifted high-velocity features. This is compatible with such blueshifts being a characteristic of populations dominated by masers at the earliest evolutionary stage of star formation, in some cases prior to the onset of methanol masers. Amongst the high-velocity emission sources there are two new examples where blueshifted high-velocity outflows dominate the total emission; these substantially increase the previously known meagre

  8. New detections of HC5N towards hot cores associated with 6.7 GHz methanol masers

    NASA Astrophysics Data System (ADS)

    Green, C.-E.; Green, J. A.; Burton, M. G.; Horiuchi, S.; Tothill, N. F. H.; Walsh, A. J.; Purcell, C. R.; Lovell, J. E. J.; Millar, T. J.

    2014-09-01

    We present new detections of cyanodiacetylene (HC5N) towards hot molecular cores, observed with the Tidbinbilla 34 m radio telescope (DSS-34). In a sample of 79 hot molecular cores, HC5N was detected towards 35. These results are counter to the expectation that long chain cyanopolyynes, such as HC5N, are not typically found in hot molecular cores, unlike their shorter chain counterpart HC3N. However, it is consistent with recent models which suggest HC5N may exist for a limited period during the evolution of hot molecular cores.

  9. The Complete, Temperature Resolved Experimental Spectrum of Methanol (CH3OH) between 214.6 and 265.4 GHz

    NASA Astrophysics Data System (ADS)

    McMillan, James P.; Fortman, Sarah M.; Neese, Christopher F.; De Lucia, Frank C.

    2014-11-01

    The spectrum of methanol (CH3OH) has been characterized between 214.6 and 265.4 GHz for astrophysically significant temperatures. Four hundred and eighty-six spectra with absolute intensity calibration recorded between 240 and 389 K provided a means for the calculation of the complete experimental spectrum (CES) of methanol as a function of temperature. The CES includes contributions from vt = 3 and other higher states that are difficult to model quantum mechanically (QM). It also includes the spectrum of the 13C isotopologue in terrestrial abundance. In general the QM models provide frequencies that are within 1 MHz of their experimental values, but there are several outliers that differ by tens of MHz. As in our recent work on methanol in the 560-654 GHz region, significant intensity differences between our experimental intensities and cataloged values were found. In this work these differences are explored in the context of several QM analyses. The experimental results presented here are analyzed to provide a frequency point-by-point catalog that is well suited for the simulation of crowded and overlapped spectra. Additionally, a catalog in the usual line frequency, line strength, and lower state energy format is provided.

  10. Detection of a Methanol Megamaser in a Major-Merger Galaxy

    NASA Astrophysics Data System (ADS)

    Chen, Xi; Ellingsen, Simon P.; Baan, Willem A.; Qiao, Hai-Hua; Li, Juan; An, Tao; Breen, Shari L.

    2015-02-01

    We have detected emission from both the {{4}-1}\\to {{3}0} E (36.2 GHz) class I and {{7}-2}\\to {{8}-1} E (37.7 GHz) class II methanol transitions toward the center of the closest ultra-luminous infrared galaxy Arp 220. The emission in both methanol transitions shows narrow spectral features and has luminosities approximately 8 orders of magnitude stronger than those observed from typical class I methanol masers observed in Galactic star formation regions. The emission is also orders of magnitude stronger than the expected intensity of thermal emission from these transitions and based on these findings we suggest that the emission from the two transitions are masers. These observations provide the first detection of a methanol megamaser in the 36.2 and 37.7 GHz transitions and represent only the second detection of a methanol megamaser, following the recent report of an 84 GHz methanol megamaser in NGC 1068. We find that the methanol megamasers are significantly offset from the nuclear region and arise toward regions where there is Hα emission, suggesting that they are associated with starburst activity. The high degree of correlation between the spatial distribution of the 36.2 GHz methanol and X-ray plume emission suggests that the production of strong extragalactic class I methanol masers is related to galactic-outflow-driven shocks and perhaps cosmic rays. In contrast to OH and H2O megamasers which originate close to the nucleus, methanol megamasers provide a new probe of feedback (e.g., outflows) processes on larger scales and of star formation beyond the circumnuclear starburst regions of active galaxies.

  11. DETECTION OF A METHANOL MEGAMASER IN A MAJOR-MERGER GALAXY

    SciTech Connect

    Chen, Xi; Baan, Willem A.; Qiao, Hai-Hua; Li, Juan; An, Tao; Ellingsen, Simon P.; Breen, Shari L.

    2015-02-10

    We have detected emission from both the 4{sub −1}→3{sub 0} E (36.2 GHz) class I and 7{sub −2}→8{sub −1} E (37.7 GHz) class II methanol transitions toward the center of the closest ultra-luminous infrared galaxy Arp 220. The emission in both methanol transitions shows narrow spectral features and has luminosities approximately 8 orders of magnitude stronger than those observed from typical class I methanol masers observed in Galactic star formation regions. The emission is also orders of magnitude stronger than the expected intensity of thermal emission from these transitions and based on these findings we suggest that the emission from the two transitions are masers. These observations provide the first detection of a methanol megamaser in the 36.2 and 37.7 GHz transitions and represent only the second detection of a methanol megamaser, following the recent report of an 84 GHz methanol megamaser in NGC 1068. We find that the methanol megamasers are significantly offset from the nuclear region and arise toward regions where there is Hα emission, suggesting that they are associated with starburst activity. The high degree of correlation between the spatial distribution of the 36.2 GHz methanol and X-ray plume emission suggests that the production of strong extragalactic class I methanol masers is related to galactic-outflow-driven shocks and perhaps cosmic rays. In contrast to OH and H{sub 2}O megamasers which originate close to the nucleus, methanol megamasers provide a new probe of feedback (e.g., outflows) processes on larger scales and of star formation beyond the circumnuclear starburst regions of active galaxies.

  12. Cosmic Masers

    ERIC Educational Resources Information Center

    Dickinson, Dale F.

    1978-01-01

    Intense radiation at microwave frequencies is emitted by certain nebular regions and stellar atmospheres. It is generated by maser action, which does for microwaves what laser action does for light. Describes in detail the types of masers and their action. (Author/MA)

  13. The complete, temperature resolved experimental spectrum of methanol (CH{sub 3}OH) between 560 and 654 GHz

    SciTech Connect

    Fortman, Sarah M.; Neese, Christopher F.; De Lucia, Frank C.

    2014-02-20

    The complete spectrum of methanol (CH{sub 3}OH) has been characterized over a range of astrophysically significant temperatures in the 560.4-654.0 GHz spectral region. Absolute intensity calibration and analysis of 166 experimental spectra recorded over a slow 248-398 K temperature ramp provide a means for the simulation of the complete spectrum of methanol as a function of temperature. These results include contributions from v{sub t} = 3 and other higher states that are difficult to model via quantum mechanical (QM) techniques. They also contain contributions from the {sup 13}C isotopologue in terrestrial abundance. In contrast to our earlier work on semi-rigid species, such as ethyl cyanide and vinyl cyanide, significant intensity differences between these experimental values and those calculated by QM methods were found for many of the lines. Analysis of these differences shows the difficulty of the calculation of dipole matrix elements in the context of the internal rotation of the methanol molecule. These results are used to both provide catalogs in the usual line frequency, linestrength, and lower state energy format, as well as in a frequency point-by-point catalog that is particularly well suited for the characterization of blended lines.

  14. Maser maps and magnetic field of OH 337.705-0.053

    NASA Astrophysics Data System (ADS)

    Caswell, J. L.; Kramer, B. Hutawarakorn; Reynolds, J. E.

    2011-08-01

    New high resolution studies of the Galactic maser site 337.705-0.053 reveal its magnetic field and velocity morphology. The long baseline array of the Australia Telescope National Facility provided simultaneous observations of both the 1665- and 1667-MHz OH transitions which yielded a sequence of maps at velocity spacing 0.09 km s-1, in both senses of circular polarization, with tenth-arcsec spatial resolution. 38 small diameter maser spots were detected, spread over an ellipse with largest dimension of 1.5 arcsec. Pairs of spots with the same position, but with right and left circular polarization at different frequency, reveal Zeeman splitting. Five pairs at 1665 MHz and four at 1667 MHz are seen; at one position, pairs at both transitions indicate a comparable magnetic field and similar (central) velocity. All estimates of magnetic field are in the same sense, with a median value of -2.5 mG (pointing towards the earth), confirming an interpretation from single-dish observations. The morphology and kinematics have been compared with that of maser emission from the excited state of OH at 6035 MHz, with methanol at 6668 MHz and 12 GHz, and with water at 22 GHz. All species are intermingled, and associated with an ultracompact H II region. The site most likely lies near the tangent point of the Galactic 3-kpc ring, at a distance of 7.9 kpc. The maser spot distribution over 1.5 arcsec then corresponds to a diameter of 60 mpc, amongst the largest known, and likely to be approaching the end of the maser emitting phase. 337.705-0.053 adds to the maser sites studied in sufficient detail to explore ordered patterns in the global Galactic magnetic field.

  15. FIRST INTERSTELLAR HCO{sup +} MASER

    SciTech Connect

    Hakobian, Nicholas S.; Crutcher, Richard M. E-mail: crutcher@illinois.edu

    2012-10-10

    A previously unseen maser in the J = 1-0 transition of HCO{sup +} has been detected by the Combined Array for Millimeter-wave Astronomy (CARMA). A subarcsecond map was produced of the 2 arcmin{sup 2} region around DR21(OH), which has had previous detections of OH and methanol masers. This new object has remained undetected until now due to its extremely compact size. The object has a brightness temperature of >2500 K and an FWHM linewidth of 0.497 km s{sup -1}, both of which suggest non-thermal line emission consistent with an unsaturated maser. This object coincides in position and velocity with the methanol maser named DR21(OH)-1 by Plambeck and Menten. No compact HCO{sup +} emission was present in the CARMA data toward the other methanol masers described in that Letter. These new results support the theory introduced in Plambeck and Menten that these masers likely arise from strong outflows interacting with low mass, high density pockets of molecular gas. This is further supported by recent observations of a CO outflow by Zapata et al. that traces the outflow edges and confirms that the maser position lies along the edge of the outflow where interaction with molecular tracers can occur.

  16. Excitation of millimeter and submillimeter water masers

    NASA Technical Reports Server (NTRS)

    Neufeld, David A.; Melnick, Gary J.

    1991-01-01

    The excitation of maser emission in millimeter and submillimeter transitions of interstellar and circumstellar water is considered. An escape probability method is used to determine the equilibrium populations in 349 rotational states of both ortho- and para-water under varying conditions of gas temperature, density, water abundance, and radiation field. It is shown that, under those conditions believed to prevail around late-type stars and within star-forming regions, strong millimeter and submillimeter water maser emission can be generated by collisional excitations by H2. Several maser transitions can have strengths close to that of the 22 GHz line. The water maser line which can be observed from mountaintop facilities and those which will require air- or space-borne platforms are indicated. The exact portion of parameter space in which each maser transition exhibits peak emission is shown.

  17. Simultaneous Observatinos of H2O and SiO Masers Toward Known Extragalactic Water Maser Sources

    NASA Astrophysics Data System (ADS)

    Cho, Se-Hyung; Yoon, Dong-Hwan; Kim, Jaeheon; Byun, Do-Young; Wagner, Jan

    2015-12-01

    We observe ten known 22 GHz H_{2}O maser galaxies during February 19-22, 2011 using the 21 m Tamna telescope of the Korean VLBI Network and a new wide-band digital spectrometer. Simultaneously we searched for 43 GHz SiO v = 1, 2, J = 1-0 maser emission. We detect H_{2}O maser emission towards five sources (M 33, NGC 1052, NGC 1068, NGC 4258, M 82), with non-detections towards the remaining sources (UGC 3193, UGC 3789, Antennae H_{2}O-West, M 51, NGC 6323) likely due to sensitivity. Our 22 GHz spectra are consistent with earlier findings. Our simultaneous 43 GHz SiO maser search produced non-detections, yielding - for the first time - upper limits on the 43 GHz SiO maser emission in these sources at a 3 σ sensitivity level of 0.018 K-0.033 K (0.24 Jy-0.44 Jy) in a 1.75 km s^{-1} velocity resolution. Our findings suggest that any 43 GHz SiO masers in these sources (some having starburst-associated H_{2}O kilomasers) must be faint compared to the 22 GHz H_{2}O maser emission.

  18. Methanol

    Integrated Risk Information System (IRIS)

    Methanol ; CASRN 67 - 56 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effects )

  19. A search for OH masers in silicate carbon star candidates

    NASA Astrophysics Data System (ADS)

    Engels, Dieter; Green, James; Horiuchi, Shinji; Etoka, Sandra

    2014-04-01

    We wish to observe 22 silicate carbon stars and candidates with the Tidbinbilla radio telescope with the aim to detect possible new OH maser emission. Among the silicate carbon stars, which often show water maser emission, only V778 Cyg and IRAS 18006-3213 are known to show OH maser emission, while the present sample has never been searched for OH masers. New OH masers could be used for future interferometric observations to determine the geometry of the emission region, which is of special interest since silicate carbon stars are believed to be binaries surrounded by an oxygen-rich disk. The complement of the present sample accessible on the Northern Sky was observed with the Nancay radio telescope in the OH maser lines yielding 6 new detections. The observations proposed here will complement observations with the Effelsberg and Tidbinbilla radio telescopes in the 22 GHz water maser line.

  20. The WISE View on Water Maser Galaxies

    NASA Astrophysics Data System (ADS)

    Dick, Emily; Constantin, A.; Braatz, J. A.; Corcoran, J.

    2014-01-01

    Extensive searches for water vapor megamasers in active galactic nuclei (AGN) have resulted in ~120 detections out of ~3500 galaxies surveyed. In about 21% of the detections, the masers originate in the sub-pc circumnuclear disks. An investigation of the relationship between the mid-infrared properties and the water maser emission in galaxy centers is essential for both refinement of future maser surveys and for constraining the dominant ionization mechanism most likely associated with the maser activity. We present here the results of a careful cross reference of all galaxies surveyed to date in 22 GHz, offered by the Megamaser Cosmology Project (MCP), with the Wide field Infrared Survey Explorer (WISE) All-Sky Release data, which reveals an impressive overlap of 93% and 98% for maser detections and non-detections, respectively. We find that, while the WISE classification of AGNs based on their redder W1-W2>0.8 colors produces a potential maser detection rate of ~20%, the cut recovers significantly less than half (27%) of all the disk detections to date. We also find that the W3 band (12 microns) appears to offer significant sensitivity to the maser detection for W3<7, as well as for maser disks, with a 13% overall maser detection rate, that includes 62% of all disks detections. We discuss the possibility that the strong connection between the 22 GHz detection and the W3 emission implies a close physical association of the masing conditions with the strength of the PAH feature (11.3 microns) as well as to the warm continuum in AGNs.

  1. Water masers in the Saturnian system

    NASA Astrophysics Data System (ADS)

    Pogrebenko, S. V.; Gurvits, L. I.; Elitzur, M.; Cosmovici, C. B.; Avruch, I. M.; Montebugnoli, S.; Salerno, E.; Pluchino, S.; Maccaferri, G.; Mujunen, A.; Ritakari, J.; Wagner, J.; Molera, G.; Uunila, M.

    2009-02-01

    Context: The presence of water has long been seen as a key condition for life in planetary environments. The Cassini spacecraft discovered water vapour in the Saturnian system by detecting absorption of UV emission from a background star. Investigating other possible manifestations of water is essential, one of which, provided physical conditions are suitable, is maser emission. Aims: We report detection of water maser emission at 22 GHz associated with several Kronian satellites using Earth-based radio telescopes. Methods: We searched for water maser emission in the Saturnian system in an observing campaign using the Metsähovi and Medicina radio telescopes. Spectral data were Doppler-corrected over orbital phase for the Saturnian satellites, yielding detections of water maser emission associated with the moons Hyperion, Titan, Enceladus, and Atlas. Results: The detection of Saturnian water molecules by remote astronomical observation can be combined with in situ spacecraft measurements to harmonise the physical model of the Saturnian system.

  2. The complete, temperature resolved experimental spectrum of methanol (CH{sub 3}OH) between 214.6 and 265.4 GHz

    SciTech Connect

    McMillan, James P.; Fortman, Sarah M.; Neese, Christopher F.; De Lucia, Frank C.

    2014-11-01

    The spectrum of methanol (CH{sub 3}OH) has been characterized between 214.6 and 265.4 GHz for astrophysically significant temperatures. Four hundred and eighty-six spectra with absolute intensity calibration recorded between 240 and 389 K provided a means for the calculation of the complete experimental spectrum (CES) of methanol as a function of temperature. The CES includes contributions from v{sub t} = 3 and other higher states that are difficult to model quantum mechanically (QM). It also includes the spectrum of the {sup 13}C isotopologue in terrestrial abundance. In general the QM models provide frequencies that are within 1 MHz of their experimental values, but there are several outliers that differ by tens of MHz. As in our recent work on methanol in the 560-654 GHz region, significant intensity differences between our experimental intensities and cataloged values were found. In this work these differences are explored in the context of several QM analyses. The experimental results presented here are analyzed to provide a frequency point-by-point catalog that is well suited for the simulation of crowded and overlapped spectra. Additionally, a catalog in the usual line frequency, line strength, and lower state energy format is provided.

  3. New SIO Masers in Star Forming Regions W:51 IRS:2 and SAGITTARIUS-B2 MD:5

    NASA Astrophysics Data System (ADS)

    Hasegawa, T.; Morita, K.; Okumura, S.; Kaifu, N.; Suzuki, H.; Ohishi, M.; Hayashi, M.; Ukita, N.

    The maser emission of the 43 GHz SiO J = 1-0 transitions in two regions of active star formation, W51 IRS2 and Sgr B2 MD5, have been detected using the 45 m telescope at Nobeyama. The SiO masers coincide in position with strong H2O masers in each region within a positional uncertainty of 5arcsec. If the masers radiate isotropically, the power radiated from W51 IRS2 and Sgr B2 MD5 in the masing 43 GHz SiO lines are comparable to that from the maser in Orion-KL.

  4. Optical Properties of Host Galaxies of Extragalactic Nuclear Water Masers

    NASA Astrophysics Data System (ADS)

    Zhu, Guangtun; Zaw, Ingyin; Blanton, Michael R.; Greenhill, Lincoln J.

    2011-12-01

    We study the optical properties of the host galaxies of nuclear 22 GHz (λ = 1.35 cm) water masers. To do so, we cross-match the galaxy sample surveyed for water maser emission (123 detections and 3806 non-detections) with the Sloan Digital Sky Survey (SDSS) low-redshift galaxy sample (z < 0.05). Out of 1636 galaxies with SDSS photometry, we identify 48 detections; out of the 1063 galaxies that also have SDSS spectroscopy, we identify 33 detections. We find that maser detection rate is higher at higher optical luminosity (MB ), larger velocity dispersion (σ), and higher [O III] λ5007 luminosity, with [O III] λ5007 being the dominant factor. These detection rates are essentially the result of the correlations of isotropic maser luminosity with all three of these variables. These correlations are natural if maser strength increases with central black hole mass and the level of active galactic nucleus (AGN) activity. We also find that the detection rate is higher in galaxies with higher extinction. Based on these results, we propose that maser surveys seeking to efficiently find masers should rank AGN targets by extinction-corrected [O III] λ5007 flux when available. This prioritization would improve maser detection efficiency, from an overall ~3% without pre-selection to ~16% for the strongest intrinsic [O III] λ5007 emitters, by a factor of ~5.

  5. A receiver design for the superconducting cavity-maser oscillator

    NASA Technical Reports Server (NTRS)

    Wang, R. T.; Dick, G. J.

    1991-01-01

    A new frequency standard was demonstrated with the aid of a double phase locked loop (PLL) receiver. A superconducting cavity maser oscillator (SCMO) and a hydrogen maser are combined to show the medium term performance of the hydrogen maser together with improved short term performance made possible by the SCMO. The receiver, which generates a 100 MHz signal with reduced noise, is phase locked to (and may be used in place of) the 100 MHz hydrogen maser output. The maser signal, 2.69xxx-GHz SCMO output, and a 100 MHz quartz crystal oscillator are optimally combined by the receiver. A measured two source fractional frequency stability of 2 x 10(exp -14) was obtained for a measuring time of r = 1 sec, and 1 x 10(exp -15) at r = 1,000 sec. The 1 sec value is approx. 10 times lower than that for hydrogen masers, while the 1,000 sec value is identical to hydrogen maser performance. The design is based on phase noise models for the hydrogen maser, the SCMO, and quartz crystal oscillators for offset frequencies down to 1 x 10(exp -6) Hz.

  6. Cherenkov maser operation at lower-mm wavelengths

    SciTech Connect

    Garate, E.; Cook, R.; Heim, P.; Layman, R.; Walsh, J.

    1985-07-15

    The basic operating principles of Cerenkov maser oscillations are briefly reviewed and the experimental performance of a 3-mm device is discussed. A power level of approximately 100kW was achieved at 88 GHz and voltage tuning from 84 to 128 GHz on the fundamental TM01 mode was observed. Operation on higher-order modes at frequencies up to 300-320 GHz was demonstrated, and a two-stage buncher-amplifier configuration was investigated.

  7. Variable volume maser techniques

    NASA Technical Reports Server (NTRS)

    Reinhardt, V. S.

    1977-01-01

    The frequency stability of hydrogen masers in variable volume storage bulbs is discussed in terms of wall shift. Variable volume devices discussed include: Brenner flexible bulb, Debely device, and the concertina hydrogen maser. A flexible cone variable volume element outside the cavity is described.

  8. Unusual Shock-excited OH Maser Emission in a Young Planetary Nebula

    NASA Astrophysics Data System (ADS)

    Qiao, Hai-Hua; Walsh, Andrew J.; Gómez, José F.; Imai, Hiroshi; Green, James A.; Dawson, Joanne R.; Shen, Zhi-Qiang; Ellingsen, Simon P.; Breen, Shari L.; Jones, Paul A.; Gibson, Steven J.; Cunningham, Maria R.

    2016-01-01

    We report on OH maser emission toward G336.644-0.695 (IRAS 16333-4807), which is a H2O maser-emitting Planetary Nebula (PN). We have detected 1612, 1667, and 1720 MHz OH masers at two epochs using the Australia Telescope Compact Array, hereby confirming it as the seventh known case of an OH-maser-emitting PN. This is only the second known PN showing 1720 MHz OH masers after K 3-35 and the only evolved stellar object with 1720 MHz OH masers as the strongest transition. This PN is one of a group of very young PNe. The 1612 MHz and 1667 MHz masers are at a similar velocity to the 22 GHz H2O masers, whereas the 1720 MHz masers show a variable spectrum, with several components spread over a higher velocity range (up to 36 km s-1). We also detect Zeeman splitting in the 1720 MHz transition at two epochs (with field strengths of ˜2 to ˜10 mG), which suggests the OH emission at 1720 MHz is formed in a magnetized environment. These 1720 MHz OH masers may trace short-lived equatorial ejections during the formation of the PN.

  9. Saturation and beaming in astrophysical masers. III - Asymmetrically pumped masers

    NASA Technical Reports Server (NTRS)

    Alcock, C.; Ross, R. R.

    1986-01-01

    There is reason to believe that the physical conditions in many astrophysical masers are far from homogeneous. In particular, if the maser pump involves the absorption of infrared photons, the pump rate may vary rapidly (perhaps exponentially) across the cloud. The consequences of such variation of the pump rate for the maser radiation are calculated, and it is shown that there are substantial asymmetries in the output of the maser. A general result is that the maser radiation is preferentially emitted back toward the source of pump radiation. The implication of this result for the interpretation of the circumstellar 1612 MHz OH masers is briefly discussed.

  10. Hydrogen-Maser/Ruby-Maser/Quartz-Crystal Oscillator

    NASA Technical Reports Server (NTRS)

    Wang, Rabi T.; Dick, G. John

    1994-01-01

    Highly stable oscillator suitable for use as 100-MHz frequency standard consists of 100-MHz hydrogen maser combined with double-phase-locked-loop receiver. Generates 100-MHz signal with reduced noise. Contains 100-MHz voltage-controlled quartz-crystal oscillator (VCO) locked in phase to superconducting-cavity maser oscillator (SCMO). SCMO, locks in phase to hydrogen maser, phase-locking receiver and its SCMO/ VCO combination to hydrogen maser. Aspects of SCMO described in previous reports, including "Performance of Superconducting-Cavity Maser" (NPO-18175), NASA Tech Briefs, Vol. 15, No. 6. Performances of component oscillators complement each other.

  11. HIGH-RESOLUTION IMAGING OF WATER MASER EMISSION IN THE ACTIVE GALAXIES NGC 6240 AND M51

    SciTech Connect

    Hagiwara, Yoshiaki; Edwards, Philip G. E-mail: Philip.Edwards@csiro.au

    2015-12-20

    We present the results of observations of 22 GHz H{sub 2}O maser emission in NGC 6240 and M51 made with the Karl G. Jansky Very Large Array. Two major H{sub 2}O maser features and several minor features are detected toward the southern nucleus of NGC 6240. These features are redshifted by about 300 km s{sup −1} from the galaxy’s systemic velocity and remain unresolved at the synthesized beam size. A combination of our two-epoch observations and published data reveals an apparent correlation between the strength of the maser and the 22 GHz radio continuum emission, implying that the maser excitation relates to the activity of an active galactic nucleus in the southern nucleus rather than star-forming activity. The star-forming galaxy M51 hosts H{sub 2}O maser emission in the center of the galaxy; however, the origin of the maser has been an open question. We report the first detection of 22 GHz nuclear radio continuum emission in M51. The continuum emission is co-located with the maser position, which indicates that the maser arises from nuclear active galactic nucleus-activity and not from star-forming activity in the galaxy.

  12. Water Maser Emission Around Low/Intermediate Mass Evolved Stars

    NASA Astrophysics Data System (ADS)

    Leal-Ferreira, M. L.; Vlemmings, W. H. T.; Diamond, P. J.; Kemball, A.; Amiri, N.; Desmurs, J.-F.

    2012-07-01

    We present results of Very Long Baseline Array (VLBA) polarimetric 22 GHz H2O maser observations of a number of low/intermediate mass evolved stars. We observed 3 Miras (Ap Lyn, IK Tau and IRC+60370), 1 semi-regular variable (RT Vir) and 1 pPN (OH231.8+4.2). Circular polarization is detected in the H2O maser region of OH231.8+4.2 and we infer a magnetic field of |B||| = ~45 mG. This implies an extrapolated magnetic field of ~2.5 G on the surface of the central star. The preliminary results on RT Vir and IRC+60370 also indicate the first detection of weak H2O maser linear polarization.

  13. SiO and H2O maser emission in OH/IR objects and late-type variable stars

    NASA Technical Reports Server (NTRS)

    Nyman, L.-A.; Johansson, L. E. B.; Booth, R. S.

    1986-01-01

    A four-year search for 86-GHz SiO and H2O maser emission towards about 20 unidentified OH/IR objects and about 35 optically identified variable stars has yielded information on the temporal variations of many of these sources. The SiO maser emission is noted to behave differently in OH/IR objects as compared with Mira variables. An attempt is made to explain the appearance of strong masers in both vibrational states solely at the 43 GHz transition, under the assumption that an intrinsically weak pump mechanism generates weak (v=1, J=2-1) emission.

  14. INTERSTELLAR H{sub 2}O MASERS FROM J SHOCKS

    SciTech Connect

    Hollenbach, David; Elitzur, Moshe; McKee, Christopher F.

    2013-08-10

    We present a model in which the 22 GHz H{sub 2}O masers observed in star-forming regions occur behind shocks propagating in dense regions (preshock density n{sub 0} {approx} 10{sup 6}-10{sup 8} cm{sup -3}). We focus on high-velocity (v{sub s} {approx}> 30 km s{sup -1}) dissociative J shocks in which the heat of H{sub 2} re-formation maintains a large column of {approx}300-400 K gas; at these temperatures the chemistry drives a considerable fraction of the oxygen not in CO to form H{sub 2}O. The H{sub 2}O column densities, the hydrogen densities, and the warm temperatures produced by these shocks are sufficiently high to enable powerful maser action. The observed brightness temperatures (generally {approx} 10{sup 11}-10{sup 14} K) are the result of coherent velocity regions that have dimensions in the shock plane that are 10-100 times the shock thickness of {approx}10{sup 13} cm. The masers are therefore beamed toward the observer, who typically views the shock ''edge-on'', or perpendicular to the shock velocity; the brightest masers are then observed with the lowest line-of-sight velocities with respect to the ambient gas. We present numerical and analytic studies of the dependence of the maser inversion, the resultant brightness temperature, the maser spot size and shape, the isotropic luminosity, and the maser region magnetic field on the shock parameters and the coherence path length; the overall result is that in galactic H{sub 2}O 22 GHz masers, these observed parameters can be produced in J shocks with n{sub 0} {approx} 10{sup 6}-10{sup 8} cm{sup -3} and v{sub s} {approx} 30-200 km s{sup -1}. A number of key observables such as maser shape, brightness temperature, and global isotropic luminosity depend only on the particle flux into the shock, j = n{sub 0} v{sub s} , rather than on n{sub 0} and v{sub s} separately.

  15. Submillimeter Array Imaging of the Maser Emission from the H30α Radio Recombination Line in MWC 349A

    NASA Astrophysics Data System (ADS)

    Weintroub, Jonathan; Moran, James M.; Wilner, David J.; Young, Ken; Rao, Ramprasad; Shinnaga, Hiroko

    2008-04-01

    We used the Submillimeter Array to map the angular distribution of the H30α recombination line (231.9 GHz) in the circumstellar region of the peculiar star MWC 349A. The resolution was 1.2'', but because of high signal-to-noise ratio we measured the positions of all maser components to accuracies better than 0.01'', at a velocity resolution of 1 km s-1. The two strongest maser components (called high-velocity components) at velocities near -14 and 32 km s-1 are separated by 0.048'' +/- 0.001'' (60 AU) along a position angle of 102° +/- 1°. The distribution of maser emission at velocities between and beyond these two strongest components were also provided. The continuum emission lies at the center of the maser distribution to within 10 mas. The masers appear to trace a nearly edge-on rotating disk structure, reminiscent of the water masers in Keplerian rotation in the nuclear accretion disk of the galaxy NGC 4258. However, the maser components in MWC 349A do not follow a simple Keplerian kinematic prescription with v ~ r-1/2, but have a larger power-law index. We explore the possibility that the high-velocity masers trace spiral density or shock waves. We also emphasize caution in the interpretation of relative centroid maser positions where the maser is not clearly resolved in position or velocity, and we present simulations that illustrate the range of applicability of the centroiding method.

  16. Operation of a quasioptical electron cyclotron maser

    SciTech Connect

    Morse, E.C.; Pyle, R.V.

    1984-12-01

    The electron cyclotron maser or gyrotron concept has been developed to produce sources producing 200 kW at 28 GHz continuously, and higher power outputs and frequencies in pulsed mode. These sources have been useful in electron cyclotron resonance heating (ECRH) in magnetically confined fusion devices. However, higher frequencies and higher power levels will be required in reactor-grade fusion plasmas, with likely requirements of 1.0 MW or more per source at 140 GHz. Conventional gyrotrons follow a trend of decreasing power for increasing frequency. In order to circumvent this problem, the quasioptical electron cyclotron maser was proposed. In this device, the closed resonator of the conventional gyrotron is replaced with an open, Fabry-Perot type resonator. The cavity modes are then the TEM-type modes of an optical laser. The advantage of this configuration is that the cavity size is not a function of frequency, since the length can be any half-integer number of wavelengths. Furthermore, the beam traverses across the cavity transverse to the direction of radiation output, and thus the rf window design is less complicated than in conventional tubes. The rf output, if obtained by diffraction coupling around one of the mirrors, could be in a TEM mode, which would allow for quasioptical transmission of the microwaves into the plasma in fusion devices. 4 references, 1 figure.

  17. Free electron maser experiments in the low-frequency limit

    SciTech Connect

    Drori, R.; Jerby, E.; Shahadi, A.

    1995-12-31

    Table-top free-electron maser (FEM) experiments operating in the low-frequency (< 1 GHz) low-energy ({approximately} 1 keV) limit are reported. These FEM devices employ parallel-stripline non-dispersive waveguides (which support TEM-modes), and planar folded-foil wigglers. Thermionic cathodes and carbon-fiber cold-cathodes are used in these experiments. Results of oscillator and amplifier experiments are presented and compared with theory.

  18. A multiple system of high-mass YSOs surrounded by disks in NGC 7538 IRS1 . Gas dynamics on scales of 10-700 AU from CH3OH maser and NH3 thermal lines

    NASA Astrophysics Data System (ADS)

    Moscadelli, L.; Goddi, C.

    2014-06-01

    Context. It has been claimed that NGC 7538 IRS1 is a high-mass young stellar object (YSO) with 30 M⊙, surrounded by a rotating Keplerian disk, probed by a linear distribution of methanol masers. The YSO is also powering a strong compact Hii region or ionized wind, and is driving at least one molecular outflow. The axis orientations of the different structures (ionized gas, outflow, and disk) are, however, misaligned, which has led to the different competing models proposed to explain individual structures. Aims: We investigate the 3D kinematics and dynamics of circumstellar gas with very high linear resolution, from tens to 1500 AU, with the ultimate goal of building a comprehensive dynamical model for what is considered the best high-mass accretion disk candidate around an O-type young star in the northern hemisphere. Methods: We used high-angular resolution observations of 6.7 GHz CH3OH masers with the EVN, NH3 inversion lines with the JVLA B-Array, and radio continuum with the VLA A-Array. In particular, we employed four different observing epochs of EVN data at 6.7 GHz, spanning almost eight years, which enabled us to measure line-of-sight (l.o.s.) accelerations and proper motions of CH3OH masers, besides l.o.s. velocities and positions (as done in previous works). In addition, we imaged highly excited NH3 inversion lines, from (6,6) to (13,13), which enabled us to probe the hottest molecular gas very close to the exciting source(s). Results: We confirm previous results that five 6.7 GHz maser clusters (labeled from "A" to "E") are distributed over a region extended N-S across ≈1500 AU, and are associated with three components of the radio continuum emission. We propose that these maser clusters identify three individual high-mass YSOs in NGC 7538 IRS1, named IRS1a (associated with clusters "B" and "C"), IRS1b (associated with cluster "A"), and IRS1c (associated with cluster "E"). We find that the 6.7 GHz masers distribute along a line, with a regular

  19. VERY LARGE ARRAY DETECTION OF THE 36 GHz ZEEMAN EFFECT IN DR21W REVISITED

    SciTech Connect

    Momjian, Emmanuel; Sjouwerman, Lorant O.; Fish, Vincent L.

    2012-09-20

    We report on the observation of the 36 GHz methanol maser line in the star-forming region DR21W to accurately measure the Zeeman effect. The Zeeman signature reported by Fish et al. became suspicious after an instrumental effect was discovered in the early days of the commissioning of the Very Large Array Wide-band Digital Architecture correlator. We conclude that the previously reported magnetic field strength of 58 mG (1.7 Hz mG{sup -1}/z) is instrumental in nature and thus incorrect. With the improved performance of the array, we now deduce a 3{sigma} limit of -4.7 to +0.4 mG (1.7 Hz mG{sup -1}/z) for the line-of-sight component of the magnetic field strength in DR21W.

  20. Formaldehyde Masers: Exclusive Tracers of High-mass Star Formation

    NASA Astrophysics Data System (ADS)

    Araya, E. D.; Olmi, L.; Morales Ortiz, J.; Brown, J. E.; Hofner, P.; Kurtz, S.; Linz, H.; Creech-Eakman, M. J.

    2015-11-01

    The detection of four formaldehyde (H2CO) maser regions toward young high-mass stellar objects in the last decade, in addition to the three previously known regions, calls for an investigation of whether H2CO masers are an exclusive tracer of young high-mass stellar objects. We report the first survey specifically focused on the search for 6 cm H2CO masers toward non high-mass star-forming regions (non HMSFRs). The observations were conducted with the 305 m Arecibo Telescope toward 25 low-mass star-forming regions, 15 planetary nebulae and post-AGB stars, and 31 late-type stars. We detected no H2CO emission in our sample of non HMSFRs. To check for the association between high-mass star formation and H2CO masers, we also conducted a survey toward 22 high-mass star-forming regions from a Hi-GAL (Herschel infrared Galactic Plane Survey) sample known to harbor 6.7 GHz CH3OH masers. We detected a new 6 cm H2CO emission line in G32.74-0.07. This work provides further evidence that supports an exclusive association between H2CO masers and young regions of high-mass star formation. Furthermore, we detected H2CO absorption toward all Hi-GAL sources, and toward 24 low-mass star-forming regions. We also conducted a simultaneous survey for OH (4660, 4750, 4765 MHz), H110α (4874 MHz), HCOOH (4916 MHz), CH3OH (5005 MHz), and CH2NH (5289 MHz) toward 68 of the sources in our sample of non HMSFRs. With the exception of the detection of a 4765 MHz OH line toward a pre-planetary nebula (IRAS 04395+3601), we detected no other spectral line to an upper limit of 15 mJy for most sources.

  1. SPLASH: Accurate OH maser positions

    NASA Astrophysics Data System (ADS)

    Walsh, Andrew; Gomez, Jose F.; Jones, Paul; Cunningham, Maria; Green, James; Dawson, Joanne; Ellingsen, Simon; Breen, Shari; Imai, Hiroshi; Lowe, Vicki; Jones, Courtney

    2013-10-01

    The hydroxyl (OH) 18 cm lines are powerful and versatile probes of diffuse molecular gas, that may trace a largely unstudied component of the Galactic ISM. SPLASH (the Southern Parkes Large Area Survey in Hydroxyl) is a large, unbiased and fully-sampled survey of OH emission, absorption and masers in the Galactic Plane that will achieve sensitivities an order of magnitude better than previous work. In this proposal, we request ATCA time to follow up OH maser candidates. This will give us accurate (~10") positions of the masers, which can be compared to other maser positions from HOPS, MMB and MALT-45 and will provide full polarisation measurements towards a sample of OH masers that have not been observed in MAGMO.

  2. Water maser emission in the Saturnian system

    NASA Astrophysics Data System (ADS)

    Horiuchi, Shinji; Cimo, Giuseppe; Gurvits, Leonid; Pogrebenko, Sergei; Molera Calves, Guifré

    2010-10-01

    Prompted by the recent discovery of a water vapour plume of Enceladus by the Cassini spacecraft, our team started an observational programme to search for possible 22 GHz water vapour maser emission associated with different objects in the Kronian system. The observations have been conducted so far with the 32 m Medicina radio telescope (INAF-IRA, Italy) and the 14 m Metsahovi radio telescope (Aalto University, MRO, Finland). During the 2006-2008 campaigns, more than 300 hours of data have been analysed, and initial results including maser detections up to 7.0 sigma level have been presented. The detections attracted considerable interest and attempts to confirm them and investigate the phenomenon in depth. No confirmations have been published so far. In order to provide critical verification of these detections and study the details of masing conditions efficiently, we request a total of 20 hours on the Tidbinbilla 70 m telescope (DSS43) to observe Saturn and its moons during several, non-consecutive days. Due to natural changes of the planetary target positions, targets' coordinates will be provided after the antenna time is allocated.

  3. Dust Grains and the Luminosity of Circumnuclear Water Masers in Active Galaxies

    NASA Technical Reports Server (NTRS)

    Collison, Alan J.; Watson, William D.

    1995-01-01

    In previous calculations for the luminosities of 22 GHz water masers, the pumping is reduced and ultimately quenched with increasing depth into the gas because of trapping of the infrared (approximately equals 30-150 micrometers), spectral line radiation of the water molecule. When the absorption (and reemission) of infrared radiation by dust grains is included, we demonstrate that the pumping is no longer quenched but remains constant with increasing optical depth. A temperature difference between the grains and the gas is required. Such conditions are expected to occur, for example, in the circumnuclear masing environments created by X-rays in active galaxies. Here, the calculated 22 GHz maser luminosities are increased by more than an order of magnitude. Application to the well-studied, circumnuclear masing disk in the galaxy NGC 4258 yields a maser luminosity near that inferred from observations if the observed X-ray flux is assumed to be incident onto only the inner surface of the disk.

  4. A dual-cavity ruby maser for the Ka-band link experiment

    NASA Technical Reports Server (NTRS)

    Shell, J.; Quinn, R. B.

    1994-01-01

    A 33.68-GHz dual-cavity ruby maser was built to support the Ka-Band Link Experiment (KABLE) conducted with the Mars Observer spacecraft. It has 25 dB of net gain and a 3-dB bandwidth of 85 MHz. Its noise temperature in reference to the cooled feedhorn aperture is 5 K.

  5. Evaluation of modern hydrogen masers

    NASA Technical Reports Server (NTRS)

    Kirk, A.; Kuhnle, P.; Sydnor, R. L.

    1983-01-01

    The masers were tested for environmental sensitivities (magnetic field, temperature, barometric pressure) and long-term aging. Allan variance runs of 72 days were made in order to attain averaging times from several seconds to 1 million seconds. Auto- and cross-correlation techniques were used to determine the effects of uncontrolled parameters such as humidity. Three-cornered-hat and other data reduction techniques were used to determine the characteristics of the individual masers.

  6. Saturation and beaming in astrophysical masers

    NASA Technical Reports Server (NTRS)

    Alcock, C.; Ross, R. R.

    1985-01-01

    A 'four-stream' model system of equations that are closely analogous to the equations of radiative transfer in a maser spectral line and are amenable to numerical solution are constructed. This model is used to investigate radiative transfer in asymmetric maser clouds. Competition between different beams of radiation for available pump photons is important in both unsaturated and saturated masers. Consequently, the radiation from a typical cloud will be highly beamed, even if the maser is saturated, because the shape of a typical cloud is not symmetric. In addition, it is shown that analysis of maser emission lines formed in expanding envelopes does not reveal the degree of saturation of the maser.

  7. A study of the region of massive star formation L379IRS1 in radio lines of methanol and other molecules

    NASA Astrophysics Data System (ADS)

    Kalenskii, S. V.; Shchurov, M. A.

    2016-04-01

    The results of spectral observations of the region of massive star formation L379IRS1 (IRAS18265-1517) are presented. The observations were carried out with the 30-m Pico Veleta radio telescope (Spain) at seven frequencies in the 1-mm, 2-mm, and 3-mm wavelength bands. Lines of 24 molecules were detected, from simple diatomic or triatomic species to complex eight- or nine-atom compounds such as CH3OCHO or CH3OCH3. Rotation diagrams constructed from methanol andmethyl cyanide lines were used to determine the temperature of the quiescent gas in this region, which is about 40-50 K. In addition to this warm gas, there is a hot component that is revealed through high-energy lines of methanol and methyl cyanide, molecular lines arising in hot regions, and the presence of H2O masers and Class II methanol masers at 6.7 GHz, which are also related to hot gas. One of the hot regions is probably a compact hot core, which is located near the southern submillimeter peak and is related to a group of methanol masers at 6.7 GHz. High-excitation lines at other positions may be associated with other hot cores or hot post-shock gas in the lobes of bipolar outflows. The rotation diagrams can be use to determine the column densities and abundances of methanol (10-9) and methyl cyanide (about 10-11) in the quiescent gas. The column densities of A- and E-methanol in L379IRS1 are essentually the same. The column densities of other observedmolecules were calculated assuming that the ratios of the molecular level abundances correspond to a temperature of 40 K. The molecular composition of the quiescent gas is close to that in another region of massive star formation, DR21(OH). The only appreciable difference is that the column density of SO2 in L379IRS1 is at least a factor of 20 lower than the value in DR21(OH). The SO2/CS and SO2/OCS abundance ratios, which can be used as chemical clocks, are lower in L379IRS1 than in DR21(OH), suggesting that L379IRS1 is probably younger than DR21(OH).

  8. Location of H2O maser in the double-nuclei system of NGC 6240

    NASA Astrophysics Data System (ADS)

    Hagiwara, Y.; Diamond, P. J.; Miyoshi, M.

    2003-03-01

    We performed VLA observations of the 22 GHz H2O; maser emission in the merging galaxy NGC 6240, which hosts the well-known double active nuclei. In a previous paper, we reported on the first solid detection of the H2O; maser emission in 2001. After two abortive attempts due to the weakness and probable variability of the emission, the maser was detected with the VLA in June 2002. The emission is unresolved at ~ 0.3 arcsec and coincides with the southern 22 GHz continuum peak to ~ 0.007 arcsec ( ~ 3 pc: D = 97 Mpc). The detection of the maser in the southern nucleus indicates that nuclear activity of the galaxy, which is significant in X-ray and far-infrared (FIR) bands, lies mainly in the southern nucleus, and the nucleus without a high brightness peak could be explained by thick dust emitting FIR radiation. We favour the idea that the maser in NGC 6240 is associated with the AGN-activity.

  9. Proper Motions of H2O Masers in the Water Fountain Source IRAS 19190+1102

    NASA Astrophysics Data System (ADS)

    Day, F. M.; Pihlström, Y. M.; Claussen, M. J.; Sahai, R.

    2010-04-01

    We report on the results of two epochs of Very Long Baseline Array observations of the 22 GHz water masers toward IRAS 19190+1102. The water maser emission from this object shows two main arc-shaped formations perpendicular to their NE-SW separation axis. The arcs are separated by ~280 mas in position and are expanding outward at an angular rate of 2.35 mas yr-1. We detect maser emission at velocities between -53.3 km s-1 and +78.0 km s-1, and there is a distinct velocity pattern where the NE masers are blueshifted and the SW masers are redshifted. The outflow has a three-dimensional outflow velocity of 99.8 km s-1 and a dynamical age of about 59 yr. A group of blueshifted masers not located along the arcs shows a change in velocity of more than 25 km s-1 between epochs, and may be indicative of the formation of a new lobe. These observations show that IRAS 19190+1102 is a member of the class of "water fountain" pre-planetary nebulae displaying bipolar structure.

  10. Water in Massive protostellar objects: first detection of THz water maser and water inner abundance.

    NASA Astrophysics Data System (ADS)

    Herpin, Fabrice

    2014-10-01

    The formation massive stars is still not well understood. Despite numerous water line observations with Herschel telescope, over a broad range of energies, in most of the observed sources the WISH-KP (Water In Star-forming regions with Herschel, Co-PI: F. Herpin) observations were not able to trace the emission from the hot core. Moreover, water maser model predict that several THz water maser should be detectable in these objects. We aim to detect for the first time the THz maser lines o-H2O 8(2,7)- 7(3,4) at 1296.41106 GHz and p-H2O 7(2,6)- 6(3,3) at 1440.78167 GHz as predicted by the model. We propose two sources for a northern flight as first priority and two other sources for a possible southern flight. This will 1) constrain the maser theory, 2) constrain the physical conditions and water abundance in the inner layers of the prostellar environnement. In addition, we will use the p-H2O 3(3,1)- 4(0,4) thermal line at 1893.68651 GHz (L2 channel) in order to probe the physical conditions and water abundance in the inner layers of the prostellar objects where HIFI-Herschel has partially failed.

  11. Superconducting magnet for a Ku-band maser.

    NASA Technical Reports Server (NTRS)

    Berwin, R.; Wiebe, E.; Dachel, P.

    1972-01-01

    A superconducting magnet to provide a uniform magnetic field of up to 8000 G in a 1.14-cm gap for the 15.3-GHz (Ku-band) traveling wave maser is described. The magnet operates in a persistent mode in the vacuum environment of a closed-cycle helium refrigerator (4.5 K). The features of a superconducting switch, which has both leads connected to 4.5 K heat stations and thereby does not receive heat generated by the magnet charging leads, are described.

  12. Detection of 183 GHz H2O megamaser emission towards NGC 4945

    NASA Astrophysics Data System (ADS)

    Humphreys, E. M. L.; Vlemmings, W. H. T.; Impellizzeri, C. M. V.; Galametz, M.; Olberg, M.; Conway, J. E.; Belitsky, V.; De Breuck, C.

    2016-08-01

    Aims: The aim of this work is to search Seyfert 2 galaxy NGC 4945, a well-known 22 GHz water megamaser galaxy, for H2O (mega)maser emission at 183 GHz. Methods: We used APEX SEPIA Band 5 (an ALMA Band 5 receiver on the APEX telescope) to perform the observations. Results: We detected 183 GHz H2O maser emission towards NGC 4945 with a peak flux density of ~3 Jy near the galactic systemic velocity. The emission spans a velocity range of several hundred km s-1. We estimate an isotropic luminosity of >1000 L⊙, classifying the emission as a megamaser. A comparison of the 183 GHz spectrum with that observed at 22 GHz suggests that 183 GHz emission also arises from the active galactic nucleus (AGN) central engine. If the 183 GHz emission originates from the circumnuclear disk, then we estimate that a redshifted feature at 1084 km s-1 in the spectrum should arise from a distance of 0.022 pc from the supermassive black hole (1.6 × 105 Schwarzschild radii), i.e. closer than the water maser emission previously detected at 22 GHz. This is only the second time 183 GHz maser emission has been detected towards an AGN central engine (the other galaxy being NGC 3079). It is also the strongest extragalactic millimetre/submillimetre water maser detected to date. Conclusions: Strong millimetre 183 GHz H2O maser emission has now been shown to occur in an external galaxy. For NGC 4945, we believe that the maser emission arises, or is dominated by, emission from the AGN central engine. Emission at higher velocity, i.e. for a Keplerian disk closer to the black hole, has been detected at 183 GHz compared with that for the 22 GHz megamaser. This indicates that millimetre/submillimetre H2O masers can indeed be useful for tracing out more of AGN central engine structures and dynamics than previously probed. Future observations using ALMA Band 5 should unequivocally determine the origin of the emission in this and other galaxies.

  13. Class I methanol megamasers: a potential probe of starburst activity and feedback in active galaxies

    NASA Astrophysics Data System (ADS)

    Chen, X.; Ellingsen, S. P.; Zhang, J.-S.; Wang, J.-Z.; Shen, Z.-Q.; Wu, Q.-W.; Wu, Z.-Z.

    2016-06-01

    Previous observations have shown that the distribution of 36.2-GHz class I methanol megamaser (MM) emission in Arp 220 is highly correlated with the diffuse X-rays. On this basis it was suggested that methanol MM may be produced either by the effects of galactic-outflow-driven shocks and/or cosmic rays. Here we report the results of a single-dish survey undertaken with the Greenbank Telescope (GBT) to improve our understanding of the pumping conditions of extragalactic class I methanol masers and their relationship to starburst and feedback processes within the host galaxies, towards a sample which includes 16 galaxies which show both extended soft X-ray emission, and either OH or H2O MM emission. Large baseline ripples in the GBT spectra limited our results to tentative detections towards 11 of the target galaxies. Analysis of these tentative detections shows that there are significant correlations between the methanol intensity and the host-galaxy infrared, radio and OH MM emission, but no correlation with the X-ray and H2O MM emission. Some sources show methanol emission significantly offset from the systemic velocity of the galaxy (by up to 1000 km s-1) and we propose that these are associated with galactic-scale outflows from active galactic nuclei (AGNs) feedback. The combined observational properties suggest that class I methanol MMs are related to significant starburst and molecular outflow activity and hence may provide a potential probe of AGN feedback and starburst processes in the host galaxies.

  14. WIDESPREAD METHANOL EMISSION FROM THE GALACTIC CENTER: THE ROLE OF COSMIC RAYS

    SciTech Connect

    Yusef-Zadeh, F.; Royster, M.; Cotton, W.; Viti, S.; Wardle, M.

    2013-02-20

    We report the discovery of a widespread population of collisionally excited methanol J = 4{sub -1} to 3{sub 0} E sources at 36.2 GHz from the inner 66' Multiplication-Sign 18' (160 Multiplication-Sign 43 pc) of the Galactic center. This spectral feature was imaged with a spectral resolution of 16.6 km s{sup -1} taken from 41 channels of a Very Large Array continuum survey of the Galactic center region. The revelation of 356 methanol sources, most of which are maser candidates, suggests a large abundance of methanol in the gas phase in the Galactic center region. There is also spatial and kinematic correlation between SiO (2-1) and CH{sub 3}OH emission from four Galactic center clouds: the +50 and +20 km s{sup -1} clouds and G0.13-0.13 and G0.25 + 0.01. The enhanced abundance of methanol is accounted for in terms of induced photodesorption by cosmic rays as they travel through a molecular core, collide, dissociate, ionize, and excite Lyman Werner transitions of H{sub 2}. A time-dependent chemical model in which cosmic rays drive the chemistry of the gas predicts CH{sub 3}OH abundance of 10{sup -8} to 10{sup -7} on a chemical timescale of 5 Multiplication-Sign 10{sup 4} to 5 Multiplication-Sign 10{sup 5} years. The average methanol abundance produced by the release of methanol from grain surfaces is consistent with the available data.

  15. Characteristics of advanced hydrogen maser frequency standards

    NASA Technical Reports Server (NTRS)

    Peters, H. E.

    1973-01-01

    In house research and development at Goddard Space Flight Center to provide advanced frequency and time standards for the most demanding applications is concentrated primarily in field operable atomic hydrogen masers. Some of the most important goals for the new maser designs have been improved long and short term stability, elimination of the need for auto tuning, increased maser oscillation level, improved hydrogen economy, increased operational life, minimization of operator control or monitoring, improvement in magnetic isolation or sensitivity, and reduction in size and weight. New design concepts which have been incorporated in these masers to achieve these goals are described. The basic maser assemblies and control systems have recently been completed; the masers are oscillating; and operational testing has begun. Data illustrating the improvements in maser performance was available and presented.

  16. Methanol as a Sensitive Probe for Spatial and Temporal Variations of the Proton-to-Electron Mass Ratio

    SciTech Connect

    Jansen, Paul; Ubachs, Wim; Bethlem, Hendrick L.; Xu Lihong; Kleiner, Isabelle

    2011-03-11

    The 6.7 and 12.2 GHz masers, corresponding to the 5{sub 1}{yields}6{sub 0}A{sup +} and 2{sub 0}{yields}3{sub -1}E transitions in methanol (CH{sub 3}OH), respectively, are among the brightest radio objects in the sky. We present calculations for the sensitivity of these and other transitions in the ground state of methanol to a variation of the proton-to-electron mass ratio. We show that the sensitivity is greatly enhanced due to a cancellation of energies associated with the hindered internal rotation and the overall rotation of the molecule. We find sensitivities of K{sub {mu}=}-42 and K{sub {mu}=}-33, for the 5{sub 1}{yields}6{sub 0}A{sup +} and 2{sub 0}{yields}3{sub -1}E transitions, respectively. The sensitivities of other transitions in the different isotopologues of methanol range from -88 to 330. This makes methanol a sensitive probe for spatial and temporal variations of the proton-to-electron mass ratio.

  17. FORMALDEHYDE MASERS: EXCLUSIVE TRACERS OF HIGH-MASS STAR FORMATION

    SciTech Connect

    Araya, E. D.; Brown, J. E.; Olmi, L.; Ortiz, J. Morales; Hofner, P.; Creech-Eakman, M. J.; Kurtz, S.; Linz, H.

    2015-11-15

    The detection of four formaldehyde (H{sub 2}CO) maser regions toward young high-mass stellar objects in the last decade, in addition to the three previously known regions, calls for an investigation of whether H{sub 2}CO masers are an exclusive tracer of young high-mass stellar objects. We report the first survey specifically focused on the search for 6 cm H{sub 2}CO masers toward non high-mass star-forming regions (non HMSFRs). The observations were conducted with the 305 m Arecibo Telescope toward 25 low-mass star-forming regions, 15 planetary nebulae and post-AGB stars, and 31 late-type stars. We detected no H{sub 2}CO emission in our sample of non HMSFRs. To check for the association between high-mass star formation and H{sub 2}CO masers, we also conducted a survey toward 22 high-mass star-forming regions from a Hi-GAL (Herschel infrared Galactic Plane Survey) sample known to harbor 6.7 GHz CH{sub 3}OH masers. We detected a new 6 cm H{sub 2}CO emission line in G32.74−0.07. This work provides further evidence that supports an exclusive association between H{sub 2}CO masers and young regions of high-mass star formation. Furthermore, we detected H{sub 2}CO absorption toward all Hi-GAL sources, and toward 24 low-mass star-forming regions. We also conducted a simultaneous survey for OH (4660, 4750, 4765 MHz), H110α (4874 MHz), HCOOH (4916 MHz), CH{sub 3}OH (5005 MHz), and CH{sub 2}NH (5289 MHz) toward 68 of the sources in our sample of non HMSFRs. With the exception of the detection of a 4765 MHz OH line toward a pre-planetary nebula (IRAS 04395+3601), we detected no other spectral line to an upper limit of 15 mJy for most sources.

  18. A CLASS I AND CLASS II CH{sub 3}OH MASER SURVEY OF EGOs FROM THE GLIMPSE SURVEY

    SciTech Connect

    Cyganowski, C. J.; Churchwell, E.; Brogan, C. L.; Hunter, T. R.

    2009-09-10

    We present the results of a high angular resolution Very Large Array (VLA) Class I 44 GHz and Class II 6.7 GHz CH{sub 3}OH maser survey of a sample of {approx}20 massive young stellar object (MYSO) outflow candidates selected on the basis of extended 4.5 {mu}m emission in Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire images. These 4.5 {mu}m selected candidates are referred to as extended green objects (EGOs), for the common coding of this band as green in three-color Infrared Array Camera images. The detection rate of 6.7 GHz Class II CH{sub 3}OH masers, which are associated exclusively with massive YSOs, toward EGOs is {approx}>64%-nearly double the detection rate of surveys using other MYSO selection criteria. The detection rate of Class I 44 GHz CH{sub 3}OH masers, which trace molecular outflows, is {approx}89% toward EGOs associated with 6.7 GHz CH{sub 3}OH masers. The two types of CH{sub 3}OH masers exhibit different spatial distributions: 6.7 GHz masers are centrally concentrated and usually coincide with 24 {mu}m emission, while 44 GHz masers are widely distributed and generally trace diffuse 4.5 {mu}m features. We also present results of a complementary James Clerk Maxwell Telescope (JCMT) single-pointing molecular line survey of EGOs in the outflow tracers HCO{sup +}(3-2) and SiO(5-4). The HCO{sup +} line profiles and high SiO detection rate (90%) are indicative of the presence of active outflows. No 44 GHz continuum emission is detected at the 5 mJy beam{sup -1} (5{sigma}) level toward 95% of EGOs surveyed, excluding bright ultracompact H II regions as powering sources for the 4.5 {mu}m outflows. The results of our surveys constitute strong evidence that EGOs are young, massive YSOs, with active outflows, presumably powered by ongoing accretion.

  19. Operation of an X -band dielectric Cherenkov maser amplifier

    SciTech Connect

    Garate, E.; Kosai, H.; Evans, K.; Fisher, A. ); Cherry, R.; Main, W. )

    1990-03-19

    A dielectric Cherenkov maser has operated as an amplifier at a frequency of 9.8 GHz. The amplifier consisted of an electron beam interacting with the TM{sub 01} mode of a cylindrical, dielectric lined waveguide with the rf input provided by a tunable (9--10 GHz), 10 kW magnetron. The dielectric constant of the liner was 10 with inner and outer radii of 1.0 and 1.27 cm, respectively. At electron beam voltage and current of 190 kV and 90 A, respectively, the measured power gain of the amplifier was 11 dB over a 21 cm interaction length with a pulse length of approximately 1 {mu}s.

  20. High-power dielectric Cherenkov maser oscillator experiments

    SciTech Connect

    Main, W. . Lab. for Plasma Research); Cherry, R. ); Garate, E. )

    1990-06-01

    This paper presents the results of a series of experiments conducted on the dielectric Cherenkov maser (DCM) oscillator. The device consists of a cylindrical metallic waveguide of inner radius 3.64 cm which is partially filled with a dielectric liner. Traveling through the lined waveguide is an annular relativistic electron beam. Liners of dielectric constant {epsilon} = 10, 5 and 2.3 were investigated for liner thicknesses of 4 and 6 mm. The 6-mm-thick, {epsilon} = 10 liner generated an RF output of 200 MW for 20 ns at 3.8 Hz with electron-beam parameters of 700 kV, 12 kA, and pulse duration of 100 ns. The maximum measured power output for the other configurations was 80 MW at a frequency of 7 GHz ({epsilon} = 5), with several MW of power output from the polyethylene liner ({epsilon} = 2.3) at a frequency of {approximately} 9 GHz.

  1. Accurate water maser positions from HOPS

    NASA Astrophysics Data System (ADS)

    Walsh, Andrew J.; Purcell, Cormac R.; Longmore, Steven N.; Breen, Shari L.; Green, James A.; Harvey-Smith, Lisa; Jordan, Christopher H.; Macpherson, Christopher

    2014-08-01

    We report on high spatial resolution water maser observations, using the Australia Telescope Compact Array, towards water maser sites previously identified in the H2O southern Galactic Plane Survey (HOPS). Of the 540 masers identified in the single-dish observations of Walsh et al., we detect emission in all but 31 fields. We report on 2790 spectral features (maser spots), with brightnesses ranging from 0.06 to 576 Jy and with velocities ranging from -238.5 to +300.5 km s-1. These spectral features are grouped into 631 maser sites. We have compared the positions of these sites to the literature to associate the sites with astrophysical objects. We identify 433 (69 per cent) with star formation, 121 (19 per cent) with evolved stars and 77 (12 per cent) as unknown. We find that maser sites associated with evolved stars tend to have more maser spots and have smaller angular sizes than those associated with star formation. We present evidence that maser sites associated with evolved stars show an increased likelihood of having a velocity range between 15 and 35 km s-1 compared to other maser sites. Of the 31 non-detections, we conclude they were not detected due to intrinsic variability and confirm previous results showing that such variable masers tend to be weaker and have simpler spectra with fewer peaks.

  2. Methanol test

    MedlinePlus

    ... sources of methanol in the body include fruits, vegetables, and diet drinks that contain aspartame. Methanol is ... eat or drink it in toxic amounts. Methanol poisoning mainly affects the digestive system, nervous system, and ...

  3. Water masers in the Kronian system

    NASA Astrophysics Data System (ADS)

    Pogrebenko, Sergei V.; Gurvits, Leonid I.; Elitzur, Moshe; Cosmovici, Cristiano B.; Avruch, Ian M.; Pluchino, Salvatore; Montebugnoli, Stelio; Salerno, Emma; Maccaferri, Giuseppe; Mujunen, Ari; Ritakari, Jouko; Molera, Guifre; Wagner, Jan; Uunila, Minttu; Cimo, Giuseppe; Schilliro, Francesco; Bartolini, Marco

    The presence of water has been considered for a long time as a key condition for life in planetary environments. The Cassini mission discovered water vapour in the Kronian system by detecting absorption of UV emission from a background star (Hansen et al. 2006). Prompted by this discovery, we started an observational campaign for search of another manifestation of the water vapour in the Kronian system, its maser emission at the frequency of 22 GHz (1.35 cm wavelength). Observations with the 32 m Medicina radio telescope (INAF-IRA, Italy) started in 2006 using Mk5A data recording and the JIVE-Huygens software correlator. Later on, an on-line spectrometer was used at Medicina. The 14 m Metsähovi radio telescope (TKK-MRO, Finland) joined the observational campaign in 2008 using a locally developed data capture unit and software spectrometer. More than 300 hours of observations were collected in 2006-2008 campaign with the two radio telescopes. The data were analysed at JIVE using the Doppler tracking technique to compensate the observed spectra for the radial Doppler shift for various bodies in the Kronian system (Pogrebenko et al. 2009). Here we report the observational results for Hyperion, Titan, Enceladus and Atlas, and their physical interpretation. Encouraged by these results we started a campaign of follow up observations including other radio telescopes.

  4. Water maser variability over 20 years in a large sample of star-forming regions: the complete database

    NASA Astrophysics Data System (ADS)

    Felli, M.; Brand, J.; Cesaroni, R.; Codella, C.; Comoretto, G.; Di Franco, S.; Massi, F.; Moscadelli, L.; Nesti, R.; Olmi, L.; Palagi, F.; Panella, D.; Valdettaro, R.

    2007-12-01

    Context: Water vapor emission at 22 GHz from masers associated with star-forming regions is highly variable. Aims: We present a database of up to 20 years of monitoring of a sample of 43 masers within star-forming regions. The sample covers a large range of luminosities of the associated IRAS source and is representative of the entire population of H2O masers of this type. The database forms a good starting point for any further study of H2O maser variability. Methods: The observations were obtained with the Medicina 32-m radiotelescope, at a rate of 4-5 observations per year. Results: To provide a database that can be easily accessed through the web, we give for each source: plots of the calibrated spectra, the velocity-time-flux density plot, the light curve of the integrated flux, the lower and upper envelopes of the maser emission, the mean spectrum, and the rate of the maser occurrence as a function of velocity. Figures for just one source are given in the text for representative purposes. Figures for all the sources are given in electronic form the appendix. A discussion of the main properties of the H2O variability in our sample will be presented in a forthcoming paper. Based on observations with the Medicina radiotelescope operated by INAF - Istituto di Radioastronomia.

  5. Design and analysis of optically pumped submillimeter waveguide maser amplifiers and oscillators

    NASA Technical Reports Server (NTRS)

    Galantowicz, T. A.

    1975-01-01

    The design and experimental measurements are described of an optically pumped far-infrared (FIR) waveguide maser; preliminary measurements on a FIR waveguide amplifier are presented. The FIR maser was found to operate satisfactorily in a chopped CW mode using either methanol (CH3OH) or acetonitrile (CH3CN) as the active molecule. Two other gases, difluoroethane and difluoroethylene, produced an unstable output with high threshold and low output power when operated in the chopped CW mode. Experimental measurements include FIR output versus cavity length, output beam pattern, output power versus pressure, and input power. The FIR output was the input to an amplifier which was constructed similar to the oscillator. An increase of 10% in output power was noted on the 118.8 microns line of methanol.

  6. Water Masers in the Andromeda Galaxy. II. Where Do Masers Arise?

    NASA Astrophysics Data System (ADS)

    Amiri, Nikta; Darling, Jeremy

    2016-08-01

    We present a comparative multiwavelength analysis of water-maser-emitting regions and non-maser-emitting luminous 24 μm star-forming regions in the Andromeda Galaxy (M31) to identify the sites most likely to produce luminous water masers useful for astrometry and proper motion studies. Included in the analysis are Spitzer 24 μm photometry, Herschel 70 and 160 μm photometry, Hα emission, dust temperature, and star-formation rate. We find significant differences between the maser-emitting and non-maser-emitting regions: water-maser-emitting regions tend to be more infrared-luminous and show higher star-formation rates. The five water masers in M31 are consistent with being analogs of water masers in Galactic star-forming regions and represent the high-luminosity tail of a larger (and as yet undetected) population. Most regions likely to produce water masers bright enough for proper motion measurements using current facilities have already been surveyed, but we suggest three ways to detect additional water masers in M31: (1) reobserve the most luminous mid- or far-infrared sources with higher sensitivity than was used in the Green Bank Telescope survey; (2) observe early-stage star-forming regions selected by millimeter continuum that have not already been selected by their 24 μm emission, and (3) reobserve the most luminous mid- or far-infrared sources and rely on maser variability for new detections.

  7. Extrapolation of the Dutch 1 MW tunable free electron maser to a 5 MW ECRH source

    SciTech Connect

    Caplan, M.; Nelson, S.; Kamin, G.; Antonsen, T. Levush, B.; Urbanus, W.; Tulupov, A.

    1995-04-01

    A Free Electron Maser (FEM) is now under construction at the FOM Institute (Rijnhuizen) Netherlands with the goal of producing 1 MW long pulse to CW microwave output in the range 130 GHz to 250 GHz with wall plug efficiencies of 50% (Verhoeven, et al EC-9 Conference). An extrapolated version of this device is proposed which by scaling up the beam current, would produce microwave power levels of up to 5 MW CW in order to reduce the cost per watt and increase the power per module, thus providing the fusion community with a practical ECRH source.

  8. The Zeeman effect in astrophysical water masers and the observation of strong magnetic fields in regions of star formation

    NASA Technical Reports Server (NTRS)

    Nedoluha, Gerald E.; Watson, William D.

    1992-01-01

    The present study solves the transfer equations for the polarized radiation of astrophysical 22-GHz water masers in the presence of a magnetic field which causes a Zeeman splitting that is much smaller than the spectral line breadth. The emphasis is placed on the relationship between the recently detected circular polarization in this maser radiation and the strength of the magnetic field. When the observed spectral line breadth is smaller than about 0.8 km/s (FWHM), it is calculated that the uncertainty is less than a factor of about 2. The accuracy is improved significantly when the angle between the line of sight and the direction of the magnetic field does not exceed about 45 deg. Uncertainty in the strength of the magnetic field due to lack of knowledge about which hyperfine transition is the source of the 22-GHz masers is removed. The 22-GHz maser feature is found to be the result of a merger of the three strongest hyperfine components.

  9. Galactic H2O maser surveys

    NASA Astrophysics Data System (ADS)

    Felli, Marcello; Palagi, Francesco

    The first part is devoted to give an updated situation of the single dish surveys of galactic H2O masers, with particular emphasis on those associated with star forming regions (SFR). The main input for this comes from the updated Arcetri Atlas of H2O masers obtained with the Medicina 32m radio telescope. Available information on variability of the maser emission is also briefly reviewed. The second part gives a description of the results derived from the comparison of VLA observations of H2O masers in SFR and near IR images. J, H, K images are able to reveal the stellar cluster present in these highly obscured regions. IT is found that a stellar source with strong H-K excess is almost always associated with the maser spots (and not necessarily with an ultracompact HII region) and represents the direct evidence of the Young Stellar Object (YSO) which is required for the maser pumping. There are several indications suggesting that the H2O maser/near IR source may represent one of the earliest manifestation of a recently formed star. Finally, the importance of a coordination between near IR full sky surveys and H2O maser surveys is briefly discussed.

  10. Cherenkov maser at millimeter wavelengths

    SciTech Connect

    Garate, E.P.; Walsh

    1985-12-01

    The dispersion relation for the transverse magnetic modes (TM/sub 0n/) of a partially filled, dielectric-lined, cylindrical waveguide driven by a cold relativistic electron beam is derived. The effect of a gap between the electron beam and the dielectric liner is included. The dispersion relation is then used to calculate the growth rate for the Cherenkov instability in the collective tenuous-beam limit. Expressions are developed for the minimum current necessary for oscillation threshold and for the power output of the Cerenkov maser in the collective regime.

  11. A 20-year H2O maser monitoring program with the Medicina 32-m telescope

    NASA Astrophysics Data System (ADS)

    Brand, J.; Felli, M.; Cesaroni, R.; Codella, C.; Comoretto, G.; Di Franco, S.; Massi, F.; Moscadelli, L.; Nesti, R.; Olmi, L.; Palagi, F.; Palla, F.; Panella, D.; Valdettaro, R.

    2007-03-01

    The Arcetri/Bologna H2O maser group has been monitoring the 1.3-cm water maser emission from a sample of 43 star-forming regions (SFRs) and 22 late-type stars for about 20 years at a sampling rate of 4-5 observations each year, using the 32-m Medicina Radio Telescope (HPBW 1.‧9 at 22 GHz). For the late-type stars we observe representative samples of OH/IR-stars, Mira's, semi-regular variables, and supergiants. The SFR-sample spans a large interval in FIR luminosity of the associated Young Stellar Object (YSO), from 20 L to 1.5 × 106 L, and offers a unique data base for the study of the long-term (years) variability of the maser emission in regions of star formation. This presentation concerns only the masers in SFRs. The information obtained from single-dish monitoring is complementary to what is extracted from higher-resolution (VLA and VLBI) observations, and can better explore the velocity domain and the long-term variability therein. We characterize the variability of the sources in various ways and we study how it depends on the luminosity and other properties of the associated YSO and its environment.

  12. H2O masers in a jet-driven bow shock: episodic ejection from a massive young stellar object

    NASA Astrophysics Data System (ADS)

    Burns, R. A.; Handa, T.; Nagayama, T.; Sunada, K.; Omodaka, T.

    2016-07-01

    We report the results of VERA (VLBI Exploration of Radio Astrometry) multi-epoch VLBI (very long baseline interferometry) 22 GHz water maser observations of S255IR-SMA1, a massive young stellar object located in the S255 star-forming region. By annual parallax the source distance was measured as D = 1.78^{+0.12}_{-0.11} kpc and the source systemic motion was (μαcos δ, μδ) = (-0.13 ± 0.20, -0.06 ± 0.27) mas yr-1. Masers appear to trace a U-shaped bow shock whose morphology and proper motions are well reproduced by a jet-driven outflow model with a jet radius of about 6 au. The maser data, in the context of other works in the literature, reveal ejections from S255IR-SMA1 to be episodic, operating on time-scales of ˜1000 yr.

  13. Cyclotron resonance maser experiments in a bifilar helical waveguide

    NASA Astrophysics Data System (ADS)

    Aharony, Alon; Drori, Rami; Jerby, Eli

    2000-11-01

    Oscillator and amplifier cyclotron-resonance-maser (CRM) experiments in a spiral bifilar waveguide are presented in this paper. The slow-wave CRM device employs a low-energy low-current electron beam (2-12 keV, ~0.5 A). The pitch angle of the helical waveguide is relatively small; hence, the phase velocity in this waveguide, Vph≅0.8c (where c is the speed of light), is much faster than the axial velocity of the electrons, Vez<=0.2c. Thus traveling-wave-tube-type interactions are eliminated in this device. According to the CRM theory, the dominant effect in this operating regime, VezGHz by varying the axial magnetic field. A fine-tuning is possible by the electron accelerating voltage. In the amplifier mode, this CRM experiment demonstrates an amplification up to 16 dB at 5 GHz. The immediate gain bandwidth is wider than 0.1 GHz (>2%). The wide tunable range of this CRM device due to the nondispersive bifilar helix is discussed.

  14. Cyclotron resonance maser experiments in a bifilar helical waveguide

    PubMed

    Aharony; Drori; Jerby

    2000-11-01

    Oscillator and amplifier cyclotron-resonance-maser (CRM) experiments in a spiral bifilar waveguide are presented in this paper. The slow-wave CRM device employs a low-energy low-current electron beam (2-12 keV, approximately 0.5 A). The pitch angle of the helical waveguide is relatively small; hence, the phase velocity in this waveguide, V(ph) congruent with0.8c (where c is the speed of light), is much faster than the axial velocity of the electrons, V(ez)GHz by varying the axial magnetic field. A fine-tuning is possible by the electron accelerating voltage. In the amplifier mode, this CRM experiment demonstrates an amplification up to 16 dB at 5 GHz. The immediate gain bandwidth is wider than 0.1 GHz (>2%). The wide tunable range of this CRM device due to the nondispersive bifilar helix is discussed.

  15. Self-consistent simulation of cyclotron autoresonance maser amplifiers

    SciTech Connect

    Pendergast, K.D.; Danly, B.G.; Temkin, R.J.; Wurtele, J.S.

    1988-04-01

    A self-consistent, one-dimensional model of the cyclotron autoresonance maser (CARM) amplifier is developed, and numerical simulations based on this model are described. Detailed studies of the CARM gain and efficiency for a wide range of initial energy and velocity spreads are presented. The interaction efficiency is found to be substantially increased when the axial magnetic field is tapered. For example, efficiencies of greater than 41 percent are obtained for a 140-GHz CARM amplifier with a tapered axial magnetic field and a 700-kV 4.5-A electron beam with parallel velocity spreads of less than 1 percent. A discussion of the nonlinear bandwidth and interaction sensitivity to axial field inhomogeneities is presented.

  16. 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.

  17. Hydrogen maser development at Laval University

    NASA Technical Reports Server (NTRS)

    Vanier, J.; Racine, G.; Kunski, R.; Picard, M.

    1981-01-01

    The physical construction of two hydrogen masers is described and results of measurements made on one of the masers are given. These include: cavity Q, thermal time constant, line Q, signal power output, magnetic shielding factor. Preliminary results indicate that the frequency stability will be mainly affected by the thermal of the cavity. The magnetic field and the barometric fluctuations should not affect the maser at the stability level above a few parts in 10 to the 15th power, which is the goal for averaging times of several hours.

  18. Intensity-dependent circular polarization and circumstellar magnetic fields from the observation of SiO masers

    NASA Technical Reports Server (NTRS)

    Nedoluha, Gerald E.; Watson, William D.

    1994-01-01

    A new aspect of the propagation of astrophysical maser radiation in the presence of a magnetic field is described in which circular polarization is created. The resulting antisymmetric spectral line profile for this circular polarization resembles that produced by the ordinary Zeeman effect when the Zeeman splittings are much less than the spectral line breadth. It is caused by the change, with increasing maser intensity, in the axis of symmetry for the molecular quantum states from a direction that is parallel to the magnetic field to a direction that is parallel to the direction of propagation. When the maser is radiatively saturated, and the rate for stimulated emission is within an order of magnitude of the Zeeman splitting in frequency units, this 'intensity-dependent circular polarization' is greater than that due to the ordinary Zeeman effect by factors as large as 1000. The circular polarization that is observed in the spectra of circumstellar SiO (J = 1-0) masers associated with late-type giants and supergiants may then be caused by magnetic fields as weak as about 10 mG. With the standard Zeeman interpretation of the observations, magnetic fields of 10-100 G are indicated. The lower fields are similar to the limits obtained from the observation of the 22 GHz water masers which are typically somewhat further from the central star. The observed tendency for the fractional linear polarization of SiO masers to increase with increasing angular momentum of the molecular state is shown to be a likely result of anisotropic pumping. Errors are identified that invalidate a recent conflicting claim in the literature about the basic theory of maser polarization in the regime that is relevant here.

  19. Mechanically and thermally stable maser cavity resonator

    NASA Technical Reports Server (NTRS)

    Vessot, R. F. C.; Hoffman, T. E.; Levine, M. W.

    1972-01-01

    New type cavity resonator is designed for hydrogen maser. Resonator consists of three pieces of glass-ceramic material having extremely low thermal coefficient of expansion and provides very stable mechanical tuning.

  20. Hydrogen masers and cesium fountains at NRC

    NASA Technical Reports Server (NTRS)

    Boulanger, J.-S.; Morris, D.; Douglas, R. J.; Gagne, M.-C.

    1994-01-01

    The NRC masers H-3 and H-4 have been operating since June 1993 with cavity servo control. These low-flux active H masers are showing stabilities of about 10(exp -15) from 1 hour to several days. Stability results are presented, and the current and planned uses of the masers are discussed. A cesium fountain primary frequency standard project has been started at NRC. Trapping and launching experiments with the goal of 7 m/s launches are beginning. We discuss our plans for a local oscillator and servo that exploit the pulsed aspect of cesium fountain standards, and meet the challenge of 10(exp -14) tau(exp -1/2) stability without requiring masers. At best, we expect to run this frequency standard initially for periods of hours each working day rather than continuously for years, and so frequency transfer to outside laboratories has been carefully considered. We conclude that masers (or other even better secondary clocks) are required to exploit this potential accuracy of the cesium fountain. We present and discuss our conclusion that it is feasible to transfer frequency in this way with a transfer-induced uncertainty of less than 10(exp -15), even in the presence of maser frequency drift and random walk noise.

  1. Performance of Soviet and US hydrogen masers

    NASA Technical Reports Server (NTRS)

    Uljanov, Adolph A.; Demidov, Nikolai A.; Mattison, Edward M.; Vessot, Robert F. C.; Allan, David W.; Winkler, Gernot M. R.

    1990-01-01

    The frequencies of Soviet- and U.S.-built hydrogen masers located at the Smithsonian Astrophysical Observatory and at the United States Naval Observatory (USNO) were compared with each other and, via Global Positioning System (GPS) common-view measurements, with three primary frequency-reference scales. The best masers were found to have fractional frequency stabilities as low as 6 times 10(exp -16) for averaging times of approximately 10(exp 4) s. Members of the USNO maser ensemble provided frequency prediction better than 1 times 10(exp 14) for periods up to a few weeks. The frequency residuals of these masers, after removal of frequency drift and rate of change of drift, had stabilities of a few parts in 10(exp -15), with serveral masers achieving residual stabilities well below 1 times 10(exp -15) for intervals from 10(exp 5)s to 2 times 10(exp 6)s. The fractional frequency drifts of the 13 masers studied, relative to the primary reference standards, ranged from -0.2 times 10(exp -15)/day to +9.6 times 10(exp -15)/day.

  2. EVOLUTION OF THE WATER MASER EXPANDING SHELL IN W75N VLA 2

    SciTech Connect

    Kim, Jeong-Sook; Kim, Sang Joon; Kim, Soon-Wook; Kurayama, Tomoharu; Honma, Mareki; Sasao, Tesuo; Surcis, Gabriele; Canto, Jorge; Torrelles, Jose M. E-mail: skim@kasi.re.kr

    2013-04-10

    We present Very Long Baseline Interferometry (VLBI) observations of 22 GHz H{sub 2}O masers in the high-mass star-forming region of W75N, carried out with VLBI Exploration of Radio Astrometry (VERA) for three epochs in 2007 with an angular resolution of {approx}1 mas. We detected H{sub 2}O maser emission toward the radio jet in VLA 1 and the expanding shell-like structure in VLA 2. The spatial distribution of the H{sub 2}O masers detected with VERA and measured proper motions around VLA 1 and VLA 2 are similar to those found with previous VLBI observations in epochs 1999 and 2005, with the masers in VLA 1 mainly distributed along a linear structure parallel to the radio jet and, on the other hand, forming a shell-like structure around VLA 2. We have made elliptical fits to the VLA 2 H{sub 2}O maser shell-like structure observed in the different epochs (1999, 2005, and 2007), and found that the shell is still expanding eight years after its discovery. From the difference in the size of the semi-major axes of the fitted ellipses in epochs 1999 ({approx_equal}71 {+-} 1 mas), 2005 ({approx_equal}97 {+-} 3 mas), and 2007 ({approx_equal}111 {+-} 1 mas), we estimate an average expanding velocity of {approx}5 mas yr{sup -1}, similar to the proper motions measured in the individual H{sub 2}O maser features. A kinematic age of {approx}20 yr is derived for this structure. In addition, our VERA observations indicate an increase in the ellipticity of the expanding shell around VLA 2 from epochs 1999 to 2007. In fact, the elliptical fit of the VERA data shows a ratio of the minor and major axes of {approx}0.6, in contrast with an almost circular shape for the shell detected in 1999 and 2005 (b/a {approx} 0.9). This suggests that we are probably observing the formation of a jet-driven H{sub 2}O maser structure in VLA2, evolving from a non-collimated pulsed-outflow event during the first stages of evolution of a massive young stellar object (YSO). This may support predictions made

  3. Present developments and status of electron sources for high power gyrotron tubes and free electron masers

    NASA Astrophysics Data System (ADS)

    Thumm, M.

    1997-02-01

    Gyrotron oscillators are mainly used as high power mm-wave sources for start-up, electron cyclotron heating (ECH) and diagnostics of magnetically confined plasmas for controlled thermonuclear fusion research. 140 GHz (110 GHz) gyrotrons with output power Pout = 0.55 MW (0.93 MW), pulse length τ = 3.0 s (2.0 s) and efficiency η = 40% (38%) are commercially available. Total efficiencies around 50% have been achieved using single-stage depressed collectors. Diagnostic gyrotrons deliver Pout = 40 kW with τ = 40 μs at frequencies up to 650 GHz ( η≥4%). Recently, gyrotron oscillators have also been successfully used in materials processing, for example sintering of high performance, structural and functional ceramics. Such technological applications require gyrotrons with f≥24 GHz, Pout = 10-100 kW, CW, η≥30%. This paper reports on recent achievements in the development of very high power mm-wave gyrotron oscillators for long pulse or CW operation. In addition a short overview of the present development status of gyrotrons for technological applications, gyroklystron amplifiers, gyro-TWT amplifiers, cyclotron autoresonance masers (CARMs) and free electron masers (FEMs) is given. The most impressive FEM output parameters are: Pout = 2GW, τ = 20 ns, η = 13% at 140 GHz (LLNL) and Pout = 15 kW, τ = 20 μs, η = 5% in the range from 120 to 900 GHz (UCSB). In gyro-devices, magnetron injection guns (MIGs) operating in the temperature limited current regime have thus far been used most successfully. Diode guns as well as triode guns with a modulating anode are employed. Tests of a MIG operated under space-charge limited conditions have been not very successful. Electrostatic CW FEMs are driven by thermionic Pierce guns whereas pulsed high power devices employ many types of accelerators as drivers for example pulse-line accelerators, microtrons and induction or rf linacs, using field and photo emission cathodes.

  4. Cyclotron resonance maser experiments in first and second harmonics

    NASA Astrophysics Data System (ADS)

    Shahadi, Avi; Drori, Rami; Jerby, Eli

    1995-09-01

    Cyclotron-resonance maser (CRM) oscillator experiments in a nondispersive (TEM-mode) waveguide are reported in this paper. The table-top CRM oscillator constructed in our laboratory operates with a low-energy (< 5 keV), low-current (< 1 A) electron beam. The electron beam is rotating in the cyclotron frequency due to an axial magnetic field produced by an external solenoid. The large electron transverse velocity, needed to obtain amplification in a TEM-CRM, is achieved by a strong kicker coil. The coplanar waveguide used in this experiment supports odd and even TEM-modes, and enables cyclotron interactions with both first and second harmonics. Microwave output power at the first cycoltron harmonic is observed in the range of 3-6 GHz, where the frequency is tuned by the axial magnetic field in this range. A considerable second harmonic emission is observed around 7 GHz frequency. This experiment may lead to the developement of a new compact high-power microwave source.

  5. SiO masers from AGB stars in the vibrationally excited v = 1, v = 2, and v = 3 states

    NASA Astrophysics Data System (ADS)

    Desmurs, J.-F.; Bujarrabal, V.; Lindqvist, M.; Alcolea, J.; Soria-Ruiz, R.; Bergman, P.

    2014-05-01

    Context. The v = 1 and v = 2 J = 1-0 (43 GHz), and v = 1 J = 2-1 (86 GHz) SiO masers are intense in asymptotic giant branch (AGB) stars and have been mapped using very long baseline interferometry (VLBI) showing ring-like distributions. Those of the v = 1, v = 2 J = 1-0 masers are similar, but the spots are rarely coincident, while the v = 1 J = 2-1 maser arises from a well-separated region farther out. These relative locations can be explained by models tools that include the overlap of two IR lines of SiO and H2O. The v = 3 J = 1-0 line is not directly affected by any line overlap and its spot structure and position, relative to the other lines, is a good test to the standard pumping models. Aims: The aim of this project are to gain insight into the properties and the general theoretical considerations of the different SiO masers that can help to understand them. Methods: We present single-dish and simultaneous VLBI observations of the v = 1, v = 2, and v = 3 J = 1-0 maser transitions of 28SiO in several AGB stars. The results are compared to the predictions of radiative models of SiO masers that both include and not include the effect of IR line overlap. Results: The spatial distribution of the SiO maser emission in the v = 3 J = 1-0 transition from AGB stars is systematically composed of a series of spots that occupy a ring-like structure (as often found in SiO masers). The overall ring structure is extremely similar to that found in the other 43 GHz transitions and is very different from the structure of the v = 1 J = 2-1 maser. The positions of the individual spots of the different 43 GHz lines are, however, very rarely coincident, which in general is separated by about 0.3 AU (between 1 and 5 mas). These results are very difficult to reconcile with standard pumping models, which predict that the masers of rotational transitions within a given vibrational state require very similar excitation conditions (since the levels are placed practically at the same

  6. Flexible bulb large storage box hydrogen maser

    NASA Technical Reports Server (NTRS)

    Reinhardt, V.

    1973-01-01

    The principal limitation on the accuracy of the hydrogen maser as a primary frequency standard has been the irreproducibility of the frequency shift caused by collisions of the radiating atoms with the walls of the vessel containing them. The flexible bulb-large storage box hydrogen maser allows correction for this wall shift within a single device, sidestepping the reproducibility problem, and reducing the frequency error from the wall shift to the level imposed by the device's stability. The principles of the device are discussed including the flexible bulb technique and the complications caused by a multiple region storage bulb. The stability of the device is discussed including a comparison with an ordinary hydrogen maser. Data is presented from a working flexible bulb-large storage box hydrogen maser demonstrating the feasibility of the device and showing some of its operating characteristics. The flexibility of the device is demonstrated by showing how the device's added degrees of freedom allow measurement of parameters unmeasurable in an ordinary hydrogen maser.

  7. Ammonia Masers in W51: Interferometric Studies

    NASA Astrophysics Data System (ADS)

    Wilson, Thomas L.; Clarke, T. E.; Boboltz, D. A.; Henkel, C.; Mauersberger, R.; Wootten, H. A.; Broullet, N.; Baudry, A.; Despois, D.

    2014-01-01

    The galactic continuum sources W51D and W51e1e2 have been long recognized as remarkable centers of ammonia maser phenomena in the centimeter wavelength range. Henkel et al. (2013 A&A 549, A90) have measured 19 masers, of which 13 are newly found for W51-IRS2, otherwise known as W51D. These arise from inversion-rotation transitions. The single dish data were taken with the Effelsberg 100-m radio telescope of the MPIfR with an angular resolution of 43 arc seconds. The conclusion that these lines were caused by maser action is based on: (1) time variability, and (2) narrow linewidths. In addition, some lines showed systematic velocity variations. High brightness temperatures and compact sizes are needed to conclusively prove maser action. We have measured a sub-set of these ammonia lines with the C array of the Jansky-Very Large Array of the National Radio Astronomy Observatory in June 2013 with an angular resolution of better than 1 arc second. Source sizes, positions, excitation models and reasons why W51 shows such a plethora of masers will be presented.

  8. Cryogenic masers. [frequency stability and design parameters

    NASA Technical Reports Server (NTRS)

    Berlinsky, A. J.; Hardy, W. N.

    1982-01-01

    Various factors affecting the frequency stability of hydrogen masers are described and related to maser design parameters. The long-term frequency stability of a hydrogen maser is limited by the mechanical stability of the cavity, and the magnitudes of the wall relaxation, spin exchange, and recombination rates which affect the Q of the line. Magnetic resonance studies of hydrogen atoms at temperatures below 1 K and in containers coated with liquid helium films demonstrated that cryogenic masers may allow substantial improvements in all of these parameters. In particular the thermal expansion coefficients of most materials are negligible at 1 K. Spin exchange broadening is three orders of magnitude smaller at 1 K than at room temperature, and the recombination and wall relaxation rates are negligible at 0.52 K where the frequency shift due to the 4 He-coated walls of the container has a broad minimum as a function of temperature. Other advantages of the helium-cooled maser result from the high purity, homogeneity, and resilence of helium-film-coated walls and the natural compatibility of the apparatus with helium-cooled amplifiers.

  9. The magnetic field of IRAS 16293-2422 as traced by shock-induced H2O masers

    NASA Astrophysics Data System (ADS)

    Alves, F. O.; Vlemmings, W. H. T.; Girart, J. M.; Torrelles, J. M.

    2012-06-01

    Context. Shock-induced H2O masers are important magnetic field tracers of very high density gas. Water masers are found in both high- and low-mass star-forming regions, and are a powerful tool for comparing magnetic field morphologies in both mass regimes. Aims: We present one of the first magnetic field determinations for the low-mass protostellar core IRAS 16293-2422 at volume densities as high as 108-10 cm-3. Our goal is to determine wether the collapsing regime of this source is controlled by magnetic fields or other factors such as turbulence. Methods: We used the Very Large Array (VLA) to carry out spectropolarimetric observations of the 22 GHz Zeeman emission from H2O masers. From the Stokes V line profile, we are then able to estimate the magnetic field strength in the dense regions around the protostar. Results: A blend of at least three maser features can be inferred from our relatively high spatial resolution data set (~0.1''), which is reproduced as a clear non-Gaussian line profile. The emission is very stable in terms of polarization fraction and position angle across the channels. The maser spots are aligned with some components of the complex outflow configuration of IRAS 16293-2422, and are excited in zones of compressed gas produced by shocks. The post-shock particle density is in the range of 1-3 × 109 cm-3, consistent with typical water-maser pumping densities. Zeeman emission is produced by a very strong line-of-sight magnetic field (B ~ 113 mG). Conclusions: The magnetic field pressure derived from our data is comparable to the ram pressure of the outflow dynamics. This indicates that the magnetic field is energetically important to the dynamical evolution of IRAS 16293-2422.

  10. Hydrogen Maser Clock (HMC) Experiment

    NASA Technical Reports Server (NTRS)

    Vessot, Robert F. C.; Mattison, Edward M.

    1997-01-01

    The Hydrogen Maser Clock (HMC) project was originally conceived to fly on a reflight of the European Space Agency (ESA) free flying platform, the European Recoverable Carrier (EURECA) that had been launched into space and recovered by NASA's Space Transportation System (STS). A Phase B study for operation of HMC as one of the twelve EURECA payload components was begun in July 1991, and completed a year later. Phase C/D of HMC began in August 1992 and continued into early 1995. At that time ESA decided not to refly EURECA, leaving HMC without access to space. Approximately 80% of the flight support electronics are presently operating the HMC's physics package in a vacuum tank at the Smithsonian Astrophysical Observatory, and are now considered to be well-tested flight electronics. The package will continue to be operated until the end of 1997 or until a flight opportunity becomes avaiable. Appendices: letters and trip report; proceedings of the symposium on frequency standards and metrology; milli-celsius-stability thermal control for an orbiting frequency standard.

  11. Exploration of Solar Wind Acceleration Region Using Interplanetary Scintillation of Water Vapor Maser Source and Quasars

    NASA Technical Reports Server (NTRS)

    Tokumaru, Munetoshi; Yamauchi, Yohei; Kondo, Tetsuro

    2001-01-01

    Single-station observations of interplanetary scintillation (IPS) at three microwave frequencies; 2 GHz, 8 GHz and 22 GHz have been carried out between 1989 and 1998 using a large (34 m farad) radio telescope at the Kashima Space Research Center of the Communications Research Laboratory. The aim of these observations is to explore the near-sun solar wind, which is the key region for the study of the solar wind acceleration mechanism. Strong quasars; 3C279 and 3C273B were used for Kashima IPS observations at 2 GHz and 8 GHz, and a water vapor maser source, IRC20431 was used for the IPS observations at 22 GHz. Solar wind velocities derived from Kashima IPS data suggest that the solar wind acceleration takes place at radial distances between 10 and 30 solar radii (R(sub s)) from the sun. Properties of the turbulence spectrum (e.g. anisotropy, spectral index, inner scale) inferred from Kashima data are found to change systematically in the solar wind acceleration region. While the solar wind in the maximum phase appears to be dominated by the slow wind, fast and rarefied winds associated with coronal holes are found to develop significantly at high latitudes as the solar activity declines. Nevertheless, Kashima data suggests that the location of the acceleration region is stable throughout the solar cycle.

  12. First operation of a dielectric-loaded double-stripline free-electron maser experiment

    SciTech Connect

    Einat, M.; Jerby, E.; Shahadi, A.

    1995-12-31

    A tabletop free-electron maser (FEM) experiment based on a dielectric-loaded double-stripline waveguide is presented. It employs a low-energy (8 keV, 0.5 A) electron beam and a folded-foil wiggler ({lambda}w = 2 cm). Metal striplines protects the dielectric slabs from the electron beam and support quasi-TEM modes in the waveguide. Radiation output is observed at f = 3.5 GHz, in agreement with the dielectric-loaded FEM tuning relation.

  13. A small, passively operated hydrogen maser

    NASA Technical Reports Server (NTRS)

    Howe, D. A.; Walls, F. L.; Bell, H. E.; Hellwig, H.

    1979-01-01

    The paper describes a compact passive hydrogen maser with unique features including a reduction in size. It uses a passive operation mode, permitting the use of a small microwave TE(011) cavity dielectrically loaded by a low loss alumina. The Teflon coated quartz bulb common in other masers has been replaced by a Teflon coating on the inside wall of the cavity producing a simpler designed and a more rugged H-maser package. The cavity and the attached endcaps comprise the vacuum envelope, allowing the use of a single vacuum system. The dimensional stability of the ceramic cavity under barometric changes is sufficiently within the range of the electronic cavity servo so that a second vacuum system is not required. For temperature control, a single oven is located in the magnetic shield nest.

  14. Molecular masers as tracers of early stellar evolution

    NASA Astrophysics Data System (ADS)

    Strel'Nitskii, V. S.

    The discovery, observation, and interpretation of molecular masers in regions of active star formation are discussed. OH masers noted in these regions are the product of the disintegration of dense molecular envelopes surrounding compact H-II regions of young OB stars, and they typically have densities of about 10 to the 6th/cu cm and temperatures of about 100 K. H2O masers are connected with still earlier stages of stellar evolution, and are located closer to their parent stars than the OH sources. Strong CH3OH 2.5-cm masers are closely associated with OH masers.

  15. Rubidium 87 gas cell studies, phase 2. [design and characteristics of rubidium maser

    NASA Technical Reports Server (NTRS)

    Vanier, J.

    1974-01-01

    The design, development, and characteristics of a rubidium 87 maser are discussed. The design of a receiver capable of locking a crystal oscillator to the maser signal is reported. The subjects considered are: (1) maser construction, (2) maser control electronics, (3) the characteristics of the receiver, and (4) results of experimental maser tests.

  16. Reflected-wave maser. [low noise amplifier

    NASA Technical Reports Server (NTRS)

    Clauss, R. C. (Inventor)

    1976-01-01

    A number of traveling-wave, slow-wave maser structures, containing active maser material but absent the typical ferrite isolators, are immersed in a nonuniform magnetic field. The microwave signal to be amplified is inserted at a circulator which directs the signal to a slow-wave structure. The signal travels through the slow-wave structure, being amplified according to the distance traveled. The end of the slow-wave structure farthest from the circulator is arranged to be a point of maximum reflection of the signal traveling through the slow-wave structure. As a consequence, the signal to be amplified traverses the slow-wave structure again, in the opposite direction (towards the circulator) experiencing amplification equivalent to that achieved by a conventional traveling-wave maser having twice the length. The circulator directs the amplified signal to following like stages of amplification. Isolators are used in between stages to prevent signals from traveling in the wrong direction, between the stages. Reduced signal loss is experienced at each stage. The high gain produced by each slow-wave structure is reduced to a moderate value by use of a nonuniform magnetic field which also broadens the line width of the maser material. The resulting bandwidth can be exceptionally wide. Cascaded stages provide high gain, exceptionally wide bandwith and very low noise temperature.

  17. A gravitationally lensed water maser in the early Universe.

    PubMed

    Impellizzeri, C M Violette; McKean, John P; Castangia, Paola; Roy, Alan L; Henkel, Christian; Brunthaler, Andreas; Wucknitz, Olaf

    2008-12-18

    Water masers are found in dense molecular clouds closely associated with supermassive black holes at the centres of active galaxies. On the basis of the understanding of the local water-maser luminosity function, it was expected that masers at intermediate and high redshifts would be extremely rare. However, galaxies at redshifts z > 2 might be quite different from those found locally, not least because of more frequent mergers and interaction events. Here we use gravitational lensing to search for masers at higher redshifts than would otherwise be possible, and find a water maser at redshift 2.64 in the dust- and gas-rich, gravitationally lensed type-1 quasar MG J0414+0534 (refs 6-13). The isotropic luminosity is 10,000 (, solar luminosity), which is twice that of the most powerful local water maser and half that of the most distant maser previously known. Using the locally determined luminosity function, the probability of finding a maser this luminous associated with any single active galaxy is 10(-6). The fact that we see such a maser in the first galaxy we observe must mean that the volume densities and luminosities of masers are higher at redshift 2.64.

  18. Maser and infrared studies of oxygen-rich late/post-asymptotic giant branch stars and water fountains: development of a new identification method

    SciTech Connect

    Yung, Bosco H. K.; Nakashima, Jun-ichi; Henkel, Christian

    2014-10-10

    We explored an efficient method to identify evolved stars with oxygen-rich envelopes in the late asymptotic giant branch (AGB) or post-AGB phase of stellar evolution, which include a rare class of objects—the 'water fountains (WF)'. Our method considers the OH and H{sub 2}O maser spectra, the near-infrared Q-parameters (these are color indices accounting for the effect of extinction), and far-infrared AKARI colors. Here we first present the results of a new survey on OH and H{sub 2}O masers. There were 108 color-selected objects: 53 of them were observed in the three OH maser lines (1612, 1665, and 1667 MHz), with 24 detections (16 new for 1612 MHz); and 106 of them were observed in the H{sub 2}O maser line (22 GHz), with 24 detections (12 new). We identify a new potential WF source, IRAS 19356+0754, with large velocity coverages of both OH and H{sub 2}O maser emission. In addition, several objects with high-velocity OH maser emission are reported for the first time. The Q-parameters as well as the infrared [09]–[18] and [18]–[65] AKARI colors of the surveyed objects are then calculated. We suggest that these infrared properties are effective in isolating aspherical from spherical objects, but the morphology may not necessarily be related to the evolutionary status. Nonetheless, by considering altogether the maser and infrared properties, the efficiency of identifying oxygen-rich late/post-AGB stars could be improved.

  19. CARM and harmonic gyro-amplifier experiments at 17 GHz

    SciTech Connect

    Menninger, W.L.; Danly, B.G.; Alberti, S.; Chen, C.; Rullier, J.L.; Temkin, R.J.; Giguet, E. |

    1993-11-01

    Cyclotron resonance maser amplifiers are possible sources for applications such as electron cyclotron resonance heating of fusion plasmas and driving high-gradient rf linear accelerators. For accelerator drivers, amplifiers or phase locked-oscillators are required. A 17 GHz cyclotron autoresonance maser (CARM) amplifier experiment and a 17 GHz third harmonic gyro-amplifier experiment are presently underway at the MIT Plasma Fusion Center. Using the SRL/MIT SNOMAD II introduction accelerator to provide a 380 kV, 180 A, 30 ns flat top electron beam, the gyro-amplifier experiment has produced 5 MW of rf power with over 50 dB of gain at 17 GHz. The gyro-amplifier operates in the TE{sub 31} mode using a third harmonic interaction. Because of its high power output, the gyro-amplifier will be used as the rf source for a photocathode rf electron gun experiment also taking place at MIT. Preliminary gyro-amplifier results are presented, including measurement of rf power, gain versus interaction length, and the far-field pattern. A CARM experiment designed to operate in the TE{sub 11} mode is also discussed.

  20. ABUNDANT CH{sub 3}OH MASERS BUT NO NEW EVIDENCE FOR STAR FORMATION IN GCM0.253+0.016

    SciTech Connect

    Mills, E. A. C.; Ott, J.; Butterfield, N.; Ludovici, D. A.; Lang, C. C.; Schmitz, S.; Morris, M. R.

    2015-05-20

    We present new observations of the quiescent giant molecular cloud GCM0.253+0.016 in the Galactic center, using the upgraded Karl G. Jansky Very Large Array. Observations were made at wavelengths near 1 cm, at the K (24–26 GHz) and Ka (27 and 36 GHz) bands, with velocity resolutions of 1–3 km s{sup −1} and spatial resolutions of ∼0.1 pc, at the assumed 8.4 kpc distance of this cloud. The continuum observations of this cloud are the most sensitive yet made, and reveal previously undetected emission which we attribute primarily to free–free emission from external ionization of the cloud. In addition to the sensitive continuum map, we produce maps of 12 molecular lines: 8 transitions of NH{sub 3}–(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6), (7, 7), and (9, 9), as well as the HC{sub 3}N (3–2) and (4–3) lines, and CH{sub 3}OH 4{sub −1}–3{sub 0}, the latter of which is known to be a collisionally excited maser. We identify 148 CH{sub 3}OH 4{sub −1}–3{sub 0} (36.2 GHz) sources, of which 68 have brightness temperatures in excess of the highest temperature measured for this cloud (400 K) and can be confirmed to be masers. The majority of these masers are concentrated in the southernmost part of the cloud. We find that neither these masers nor the continuum emission in this cloud provide strong evidence for ongoing star formation in excess of that previously inferred by the presence of an H{sub 2}O maser.

  1. Enhanced magnetic Purcell effect in room-temperature masers

    PubMed Central

    Breeze, Jonathan; Tan, Ke-Jie; Richards, Benjamin; Sathian, Juna; Oxborrow, Mark; Alford, Neil McN

    2015-01-01

    Recently, the world’s first room-temperature maser was demonstrated. The maser consisted of a sapphire ring housing a crystal of pentacene-doped p-terphenyl, pumped by a pulsed rhodamine-dye laser. Stimulated emission of microwaves was aided by the high quality factor and small magnetic mode volume of the maser cavity yet the peak optical pumping power was 1.4 kW. Here we report dramatic miniaturization and 2 orders of magnitude reduction in optical pumping power for a room-temperature maser by coupling a strontium titanate resonator with the spin-polarized population inversion provided by triplet states in an optically excited pentacene-doped p-terphenyl crystal. We observe maser emission in a thimble-sized resonator using a xenon flash lamp as an optical pump source with peak optical power of 70 W. This is a significant step towards the goal of continuous maser operation. PMID:25698634

  2. Far infrared maser communications technology

    NASA Technical Reports Server (NTRS)

    Claspy, P. C.; Pao, Y. H.

    1975-01-01

    An optically pumped FIR laser was constructed and tested. Optimum operating conditions were determined with CH3OH as the lasing medium. The laser was found to operate equally well with flowing gas or in a sealed off configuration. The FIR cavity stability and pump laser stability were found to have significant problems. The absorption coefficient per unit pressure of 1-1 difluoroethylene at the P(22) and P(24) lines of the 10.4 micron CO2 band was measured. The FIR line pumped by P(22) occurs at approximately 890 microns, which may be in an atmospheric transmission window. It was found that significant Stark tuning of absorption lines of methanol and 1-1 difluoroethylene can be accomplished, even at the usual 100 to 300 mTorr operating pressures of FIR lasers. This means that the use of Stark tuning may enable more effective use of pump laser output.

  3. Magnetic refrigeration for maser amplifier cooling

    NASA Technical Reports Server (NTRS)

    Johnson, D. L.

    1982-01-01

    The development of a multifrequency upconverter-maser system for the DSN has created the need to develop a closed-cycle refrigerator (CCR) capable of providing more than 3 watts of refrigeration capability at 4.5 K. In addition, operating concerns such as the high cost of electrical power consumption and the loss of maser operation due to CCR failures require that improvements be made to increase the efficiency and reliability of the CCR. One refrigeration method considered is the replacement of the Joule-Thomson expansion circuit with a magnetic refrigeration. Magnetic refrigerators can provide potentially reliable and highly efficient refrigeration at a variety of temperature ranges and cooling power. The concept of magnetic refrigeration is summarized and a literature review of existing magnetic refrigerator designs which have been built and tested and that may also be considered as possibilities as a 4 K to 15 K magnetic refrigeration stage for the DSN closed-cycle refrigerator is provided.

  4. Water masers in Compton-thick AGN. I. Detailed study of the new water megamaser in IRAS 15480-0344

    NASA Astrophysics Data System (ADS)

    Castangia, P.; Tarchi, A.; Caccianiga, A.; Severgnini, P.; Della Ceca, R.

    2016-02-01

    Context. A relationship between the water maser detection rate and large nuclear column densities in AGN has often been cited in the literature. Indeed, detailed studies of luminous water masers, typically associated with the nuclear activity, allow us to investigate the innermost regions of AGN, with an impact on the still debated Unified Model for this class of objects. Aims: We have recently entertained a search for maser emission in a well-defined sample of Compton-thick AGN aimed at investigating, on firm statistical bases, the aforementioned relationship. While the survey is still ongoing, and is the subject of a forthcoming publication, a new luminous water maser has been detected in the lenticular (field) S0 galaxy IRAS 15480-0344, whose origin, associated with an accretion disc or a nuclear outflow/jet, needs to be assessed. Methods: Multi-epoch single-dish observations and VLBI measurements were performed to investigate the distribution, spatial extension, and variability of the maser emission in order to infer the main characteristics of the water megamaser. Results: The new detection in IRAS 15480-0344 is reported: a megamaser with a total single-dish isotropic luminosity of ~200 L⊙ and a profile composed of two main features, a broad line with a full width to half maximum (FWHM) linewidth of ~90 km s-1 and a narrow (FWHM< 1 km s-1) one. We performed a follow-up to the detection with the Very Long Baseline Array (VLBA) and confidently detected only the narrow component, which is coincident with the nuclear radio continuum emission detected with the Very Large Array at 8.4 GHz. A weak narrow feature has also been detected in the velocity range of the broad feature and is located 15 pc to the north-west with respect to the stronger component. Neither maser spot is associated with the compact radio continuum sources derived from the same VLBA dataset. Conclusions: The different line profiles and the spatial separation between the two features in the

  5. Coaxial configuration of the dielectric Cherenkov maser

    SciTech Connect

    Gavate, E.P.; Fisher, A. . Dept. of Physics); Main, W.G. . Lab. for Plasma Research)

    1990-10-01

    The linearized Lorentz force, continuity equation, and Maxwell's equations are used to calculate the system dispersion relation for a coaxial configuration of the dielectric Cherenkov maser. The system consists of two coaxial conductors lined with dielectric and an annular relativistic electron beam, which propagates between the two liners. Using the linearized dispersion relation, the growth rate for the beam-TM{sub on} waveguide mode instability is calculated in the strong-coupling tenuous beam limit.

  6. The superconducting cavity stability ruby maser oscillator

    NASA Technical Reports Server (NTRS)

    Dick, G. J.; Strayer, D. M.

    1985-01-01

    Analysis of an application of the rudy maser to a superconducting Cavity Stabilized oscillator shows many attractive features. These derive from the mechancial stability inherent in an all-cryogenic design and from the properties of the ruby maser itself. A multiple-cavity design has been developed to allow physical separation of the high-Q superconducting cavity and the ruby element with its requried applied magnetic field. Mode selection is accomplished in this design by tuning the ruby by means of the applied field. We conclude that such an oscillator would perform well, even with cavity Q's as low as 10 to the 8th power allowing the use of a superconductor-on-sapphire resonator with its greater rigidity and lower thermal expansion. A first test of the Superconducting Cavity Stabilized Maser Oscillator (SCSMO) confirms the efficacy of the multiple-cavity design and the applicability of the ruby maser. Frequency variation less than 4x10 to the minus 11th power was measured in the stabilized mode and is attributed to the reference oscillator and to instabilities in the pump source. Variation of 10 to the minus 10th power was observed in the low-Q unstabilized mode, again attributable to pump fluctuations. Even so, direct scaling to a Q of 10 the 9th power predicts a stability better than 10 to the minus 15th power. Together with results showing the lowest losses to date in sapphire at microwave frequencies, and preliminary experiments on superconductor-on-sapphire resonators, frequency stability, levels as low as 10 to the minus 17th power are indicated.

  7. Water Masers in the Andromeda Galaxy. I. A Survey for Water Masers, Ammonia, and Hydrogen Recombination Lines

    NASA Astrophysics Data System (ADS)

    Darling, Jeremy; Gerard, Benjamin; Amiri, Nikta; Lawrence, Kelsey

    2016-07-01

    We report the results of a Green Bank Telescope survey for water masers, ammonia (1, 1) and (2, 2), and the H66α recombination line toward 506 luminous compact 24 μm emitting regions in the Andromeda Galaxy (M31). We include the 206 sources observed in the Darling water maser survey for completeness. The survey was sensitive enough to detect any maser useful for ˜10 μas yr‑1 astrometry. No new water masers, ammonia lines, or H66α recombination lines were detected individually or in spectral stacks reaching rms noise levels of ˜3 mJy and ˜0.2 mJy, respectively, in 3.1–3.3 km s‑1 channels. The lack of detections in individual spectra and in the spectral stacks is consistent with Galactic extrapolations. Contrary to previous assertions, there do not seem to be any additional bright water masers to be found in M31. The strong variability of water masers may enable new maser detections in the future, but variability may also limit the astrometric utility of known (or future) masers because flaring masers must also fade.

  8. Water Masers in the Andromeda Galaxy. I. A Survey for Water Masers, Ammonia, and Hydrogen Recombination Lines

    NASA Astrophysics Data System (ADS)

    Darling, Jeremy; Gerard, Benjamin; Amiri, Nikta; Lawrence, Kelsey

    2016-07-01

    We report the results of a Green Bank Telescope survey for water masers, ammonia (1, 1) and (2, 2), and the H66α recombination line toward 506 luminous compact 24 μm emitting regions in the Andromeda Galaxy (M31). We include the 206 sources observed in the Darling water maser survey for completeness. The survey was sensitive enough to detect any maser useful for ˜10 μas yr-1 astrometry. No new water masers, ammonia lines, or H66α recombination lines were detected individually or in spectral stacks reaching rms noise levels of ˜3 mJy and ˜0.2 mJy, respectively, in 3.1-3.3 km s-1 channels. The lack of detections in individual spectra and in the spectral stacks is consistent with Galactic extrapolations. Contrary to previous assertions, there do not seem to be any additional bright water masers to be found in M31. The strong variability of water masers may enable new maser detections in the future, but variability may also limit the astrometric utility of known (or future) masers because flaring masers must also fade.

  9. Monitoring the New Nuclear Water Maser in Centaurus A

    NASA Astrophysics Data System (ADS)

    Ott, Juergen; Henkel, Christian; Edwards, Philip; Meier, David; Walter, Fabian; Brunthaler, Andreas; Mao, Minnie; Peck, Alison; Impellizzeri, Caterina M. V.; McCoy, Mark

    2013-10-01

    Recently, we reported nuclear water maser emission in the heart of the nearest radio galaxy Centaurus A (distance: 3.8Mpc). The redshifted line is mostly in agreement with maser emission from a shock front that was created by the jet hitting a molecular cloud. Although the 'jet maser' model seems to be a good description, we cannot exclude a 'disk maser' emitted from the accretion disk that surrounds the supermassive black hole (SMBH) of the AGN. We propose a monitoring program of the maser emission to find transient maser features. They can provide information on the substructures of the molecular cloud, H2O dissociation events, as well as absorbing molecular material in front of the SMBH. We will also be sensitive to (and derive limits of) of blue and systemic components that could indicate a disk maser origin - such a maser would be an important contribution to the cosmological distance ladder as it can be used to derive a direct geometric distance via additional LBA observations. As a secondary goal we aim for deep spectra of other molecules along the line of sight, including ammonia, which will be used for an accurate temperature measurement.

  10. Stimulated Raman scattering and the extreme high-velocity H2O maser features in W49

    NASA Technical Reports Server (NTRS)

    Boyd, R. W.

    1977-01-01

    Stimulated Raman scattering of the intense 22.2-GHz water-vapor maser radiation within W49 is examined as a possible explanation of the extremely broad spectrum of W49 extending to + or - 200 km/sec apparent Doppler velocity. Under the most favorable conditions, Raman scattering from ammonia molecules is calculated to be observable. It is unlikely that the Raman process contributes appreciably in the case of W49, as it fails to predict the observed spatial and spectral distribution of the radiation.

  11. Measurement of the Fundamental Thermal Noise Limit in a Cryogenic Sapphire Frequency Standard Using Bimodal Maser Oscillations

    SciTech Connect

    Benmessai, Karim; Kersale, Yann; Giordano, Vincent; Creedon, Daniel Lloyd; Tobar, Michael Edmund; Bourgeois, Pierre-Yves

    2008-06-13

    We report observations of the Schawlow-Townes noise limit in a cryogenic sapphire secondary frequency standard. The effect causes a fundamental limit to the frequency stability, and was measured through the novel excitation of a bimodal maser oscillation of a Whispering Gallery doublet at 12.04 GHz. The beat frequency of 10 kHz between the oscillations enabled a sensitive probe for this measurement of fractional frequency instability of 10{sup -14}{tau}{sup -1/2} with only 0.5 pW of output power.

  12. Water Maser and Ammonia Survey toward IRAS Sources in the Galaxy I. H2O Maser Data

    NASA Astrophysics Data System (ADS)

    Sunada, Kazuyoshi; Nakazato, Takeshi; Ikeda, Norio; Hongo, Satoshi; Kitamura, Yoshimi; Yang, Ji

    2007-12-01

    We present H2O maser data from a survey toward IRAS sources in the Galaxy with the Nobeyama 45m telescope. This survey had a 1σ noise level as small as 0.24Jy, resulting in one of the most sensitive water-maser surveys. The maximum distance of the masers to be detected by our survey is estimated to be 3kpc for sources with Fν,1kpc < 10Jy and 10kpc for those with 10Jy ≤ Fν,1kpc < 100Jy, where Fν,1kpc is the maser flux density converted at a distance of 1kpc. For strong masers with Fν,1kpc ≥ 100Jy, our survey could detect all sources in the Galaxy. We carried out a total of 2229 observations toward 1563 sources and detected water-maser emission toward 222 sources. Our survey newly found masers from 75 of the 222 sources. The maser spectra of the new sources are shown in addition to the line parameters of all the detected sources. Furthermore, we discovered an extremely high-velocity component with VLSR = -146 km s-1 toward a well-known source, NGC 7538 IRS 11. For the three sources of NGC 1333 IRAS 4A/B, IRAS 05329-0512, and 06053-0622, we succeeded to spatially separate multiple-velocity components.

  13. Towards detecting methanol emission in low-mass protoplanetary discs with ALMA: the role of non-LTE excitation

    NASA Astrophysics Data System (ADS)

    Parfenov, S. Yu.; Semenov, D. A.; Sobolev, A. M.; Gray, M. D.

    2016-08-01

    The understanding of organic content of protoplanetary discs is one of the main goals of the planet formation studies. As an attempt to guide the observational searches for weak lines of complex species in discs, we modelled the (sub)millimetre spectrum of gaseous methanol (CH3OH), one of the simplest organic molecules, in the representative T Tauri system. We used 1+1D disc physical model coupled to the gas-grain ALCHEMIC chemical model with and without 2D-turbulent mixing. The computed CH3OH abundances along with the CH3OH scheme of energy levels of ground and excited torsional states were used to produce model spectra obtained with the non-local thermodynamic equilibrium (non-LTE) 3D line radiative transfer code LIME. We found that the modelled non-LTE intensities of the CH3OH lines can be lower by factor of >10-100 than those calculated under assumption of LTE. Though population inversion occurs in the model calculations for many (sub)millimetre transitions, it does not lead to the strong maser amplification and noticeably high line intensities. We identify the strongest CH3OH (sub)millimetre lines that could be searched for with the Atacama Large Millimeter Array (ALMA) in nearby discs. The two best candidates are the CH3OH 50 - 40A+ (241.791 GHz) and 5-1 - 4-1E (241.767 GHz) lines, which could possibly be detected with the ˜5σ signal-to-noise ratio after ˜3 h of integration with the full ALMA array.

  14. Outflow structure within 1000 au of high-mass YSOs. I. First results from a combined study of maser and radio continuum emission

    NASA Astrophysics Data System (ADS)

    Moscadelli, L.; Sánchez-Monge, Á.; Goddi, C.; Li, J. J.; Sanna, A.; Cesaroni, R.; Pestalozzi, M.; Molinari, S.; Reid, M. J.

    2016-01-01

    Context. In high-mass (≥7 M⊙) star formation (SF) studies, high-angular resolution is crucial for resolving individual protostellar outflows (and possibly accretion disks) from the complex contribution of nearby (high- and low-mass) young stellar objects (YSO). Previous interferometric studies have focused mainly on single objects. Aims: A sensitive survey at high angular resolution is required to investigate outflow processes in a statistically significant sample of high-mass YSOs and on spatial scales relevant to testing theories. Methods: We selected a sample of 40 high-mass YSOs from water masers observed within the BeSSeL Survey. We investigated the 3D velocity and spatial structures of the molecular component of massive outflows at milli-arcsecond angular resolution using multi-epoch Very Long Baseline Array (VLBA) observations of 22 GHz water masers. We also characterize the ionized component of the flows using deep images of the radio continuum emission with resolutions of ~0."2, at 6, 13, and 22 GHz with the Jansky Very Large Array (JVLA). Results: We report the first results obtained for a subset of 11 objects from the sample. The water maser measurements provide us with a very accurate description of the molecular gas kinematics. This in turn enables us to estimate the momentum rate of individual outflows, varying in the range 10-3-100M⊙ yr-1 km s-1, among the highest values reported in the literature. In all the observed objects, the continuum emission at 13 and 22 GHz has a compact structure, with its position coincident with that of the water masers. The 6 GHz continuum consists of either compact components (mostly well aligned with the 13 and/or 22 GHz sources) or extended emission (either highly elongated or approximately spherical), which can be offset by up to a few arcseconds from the water masers. The unresolved continuum emission associated with the water masers likely points to the YSO location. The comparison of the radio continuum

  15. New maser emission from nonmetastable ammonia in NGC 7538. IV. Coincident masers in adjacent states of para-ammonia

    SciTech Connect

    Hoffman, Ian M.; Joyce, Spenser A.

    2014-02-20

    We present the first detection of para-ammonia masers in NGC 7538: multiple epochs of observation of the {sup 14}NH{sub 3} (J, K) = (10, 8) and (9,8) lines. We detect both thermal absorption and nonthermal emission in the (10,8) and (9,8) transitions and the absence of a maser in the (11,8) transition. The (9,8) maser is observed to increase in intensity by 40% over six months. Using interferometric observations with a synthesized beam of 0.''25, we find that the (10,8) and (9,8) masers originate at the same sky position near IRS 1. With strong evidence that the (10,8) and (9,8) masers arise in the same volume, we discuss the application of pumping models for the simultaneous excitation of nonmetastable (J > K) para-ammonia states having the same value of K and consecutive values of J. We also present detections of thermal absorption in rotational states ranging in energy from E/k{sub B} ∼ 200 K to 2000 K, and several non-detections in higher-energy states. In particular, we describe the populations in eight adjacent rotational states with K = 6, including two maser transitions, along with the implications for ortho-ammonia pumping models. An existing torus model for molecular gas in the environment of IRS 1 has been applied to the masers; a variety of maser species are shown to agree with the model. Historical and new interferometric observations of {sup 15}NH{sub 3} (3,3) masers in the region indicate a precession of the rotating torus at a rate comparable to continuum-emission-based models of the region. We discuss the general necessity of interferometric observations for diagnosing the excitation state of the masers and for determining the geometry of the molecular environment.

  16. Slow-wave electron cyclotron maser

    SciTech Connect

    Kho, T.H.; Lin, A.T.

    1988-09-15

    The basic physics of a slow-wave electron cyclotron maser (ECM) operating in the Cherenkov regime is considered. This device has the advantage over fast-wave ECM's in that it can be operated with direct axial injection of the electron beam, thus allowing for better control over beam quality and a potentially more compact design. The nonlinear evolution and saturation of the instability are studied using computer simulation. It is shown that high efficiency is attainable and, furthermore, that beam momentum spread is better tolerated in the Doppler-shift-dominated regime than is the case for a fast-wave ECM.

  17. New Observations Deepen Mystery Surrounding Water Masers in Elliptical Galaxy

    NASA Astrophysics Data System (ADS)

    New observations with the National Science Foundation's Very Long Baseline Array (VLBA) radio telescope have deepened the mystery surrounding water molecules in a galaxy 65 million light- years away. The water molecules are acting as natural masers -- amplifiers of microwave radio emissions -- and these cosmic masers within the galaxy NGC 1052 are raising difficult questions for astronomers trying to explain them. Results of the new observations, which pinpoint the location of water masers in NGC 1052, were announced today at the American Astronomical Society meeting in Toronto, Ontario. The researchers are: Jim Braatz of Harvard University in Cambridge, Massachusetts, Mark Claussen and Phil Diamond of the National Radio Astronomy Observatory in Socorro, New Mexico, Andrew Wilson of the University of Maryland in College Park, Maryland, and Christian Henkel of the Max Planck Institute fur Radioastronomie in Bonn, Germany. Water masers have been detected in several other galaxies. However, most galaxies containing water "megamasers" such as those in NGC 1052 are spiral galaxies. NGC 1052 is one of only two elliptical galaxies in which water megamasers have been detected. Because ellipticals tend to have much less gas and dust than spirals, the existence of the water masers in NGC 1052 is surprising by itself, though that galaxy does have more gas and dust than the typical elliptical. Located in the constellation Cetus, NGC 1052 also has an active nucleus, believed to be powered by the gravitational energy of a supermassive black hole at its core. The new VLBA observations produced an additional mystery. In other galaxies with water megamasers, the masers are believed to lie within a disk of molecules orbiting the galaxy's central black hole. This is the case, for example, in the now-famous galaxy NGC 4258, where the movement of the orbiting disk can be traced by measuring both the Doppler shift of radio emission from the masers and by tracking the motion of

  18. Modelling of Cosmic Molecular Masers: Introduction to a Computation Cookbook

    NASA Astrophysics Data System (ADS)

    Sobolev, Andrej M.; Gray, Malcolm D.

    2012-07-01

    Numerical modeling of molecular masers is necessary in order to understand their nature and diagnostic capabilities. Model construction requires elaboration of a basic description which allows computation, that is a definition of the parameter space and basic physical relations. Usually, this requires additional thorough studies that can consist of the following stages/parts: relevant molecular spectroscopy and collisional rate coefficients; conditions in and around the masing region (that part of space where population inversion is realized); geometry and size of the masing region (including the question of whether maser spots are discrete clumps or line-of-sight correlations in a much bigger region) and propagation of maser radiation. Output of the maser computer modeling can have the following forms: exploration of parameter space (where do inversions appear in particular maser transitions and their combinations, which parameter values describe a `typical' source, and so on); modeling of individual sources (line flux ratios, spectra, images and their variability); analysis of the pumping mechanism; predictions (new maser transitions, correlations in variability of different maser transitions, and the like). Described schemes (constituents and hierarchy) of the model input and output are based mainly on the experience of the authors and make no claim to be dogmatic.

  19. Exploration of Solar Wind Acceleration Region Using Interplanetary Scintillation of Water Vapor Maser Source and Quasars

    NASA Technical Reports Server (NTRS)

    Tokumaru, Munetoshi; Yamauchi, Yohei; Kondo, Tetsuro

    2001-01-01

    Single-station observations of interplanetary scintillation UPS) at three microwave frequencies 2, 8, and 22GHz, were carried out between 1989 and 1998 using a large (34-micro farad) radio telescope at the Kashima Space Research Center of the Communications Research Laboratory. The aim of these observations was to explore the near-sun solar wind, which is the key region for the study of the solar wind acceleration mechanism. Strong quasars, 3C279 and 3C273B, were used for the Kashima IPS observations at 2 and 8GHz, and a water-vapor maser source, IRC20431, was used for the IPS observations at 22GHz. Solar wind speeds derived from Kashima IPS data suggest that the solar wind acceleration takes place at radial distances between 10 and 30 solar radii (Rs) from the sun. The properties of the turbulence spectrum (e.g. anisotropy, spectral index, inner scale) inferred from the Kashima data were found to change systematically in the solar wind acceleration region. While the solar wind in the maximum phase appears to be dominated by the slow wind, fast and rarefied winds associated with the coronal holes were found to develop significantly at high latitudes as the solar activity declined. Nevertheless, the Kashima data suggests that the location of the acceleration region is stable throughout the solar cycle.

  20. A reflected-wave ruby maser with K-band tuning range and large instantaneous bandwidth

    NASA Technical Reports Server (NTRS)

    Moore, C. R.; Clauss, R. C.

    1979-01-01

    A novel maser concept is outlined and a unique design described which permits wide bandwidth and waveguide tuning range by employing four stages cascaded via cryogenically cooled circulators. Theoretical considerations for gain, bandwidth, gain ripple, and noise temperature are included. Operated on a closed-cycle helium refrigerator with a superconducting persistence-mode magnet, the four-stage amplifier is tunable from 18.3 to 26.6 GHz with 30 dB of net gain and achieves 240 MHz of 3-dB bandwidth near the center of this band. The measured noise temperature is 13 + or - 2 K referred to the room-temperature input flange. Applications are foreseen utilizing cooled parametric downconverters and upconverters with this amplifier at IF to extend the low-noise performance up to millimeter frequencies and down to L-band for radio astronomy and planetary spacecraft communications.

  1. MM-wave cyclotron auto-resonance maser for plasma heating

    NASA Astrophysics Data System (ADS)

    Ceccuzzi, S.; Dattoli, G.; Di Palma, E.; Doria, A.; Gallerano, G. P.; Giovenale, E.; Mirizzi, F.; Spassovsky, I.; Ravera, G. L.; Surrenti, V.; Tuccillo, A. A.

    2014-02-01

    Heating and Current Drive systems are of outstanding relevance in fusion plasmas, magnetically confined in tokamak devices, as they provide the tools to reach, sustain and control burning conditions. Heating systems based on the electron cyclotron resonance (ECRH) have been extensively exploited on past and present machines DEMO, and the future reactor will require high frequencies. Therefore, high power (≥1MW) RF sources with output frequency in the 200 - 300 GHz range would be necessary. A promising source is the so called Cyclotron Auto-Resonance Maser (CARM). Preliminary results of the conceptual design of a CARM device for plasma heating, carried out at ENEA-Frascati will be presented together with the planned R&D development.

  2. High-power, high-frequency, annular-beam free-electron maser

    SciTech Connect

    Fazio, M.V.; Carlsten, B.E.; Earley, L.M.; Fortgang, C.M.; Haynes, W.B.; Haddock, P.C.

    1998-11-01

    The authors have developed a 15--17 GHz free electron maser (FEM) capable of producing high power pulses with a phase stability appropriate for linear collider applications. The electron beam source is a 1 {micro}s, 800 kV, 5 kA, 6-cm-dia annular electron beam machine called BANSHEE. The beam interacts with the TM{sub 02} mode Raman FEM amplifier in a corrugated cylindrical waveguide where the beam runs close to the interaction device walls to reduce the power density in the fields. They studied the phase stability by analyzing the dispersion relation for an axial FEL, in which the rf field was transversely wiggled and the electron trajectories were purely longitudinal. Detailed particle-in-cell simulations demonstrated the transverse wiggling of the rf mode and the axial FEL interaction and explicit calculations of the growing root of the dispersion relation are included to verify the phase stability.

  3. MM-wave cyclotron auto-resonance maser for plasma heating

    SciTech Connect

    Ceccuzzi, S.; Ravera, G. L.; Tuccillo, A. A.; Dattoli, G.; Di Palma, E.; Doria, A.; Gallerano, G. P.; Giovenale, E.; Spassovsky, I.; Surrenti, V.; Mirizzi, F.

    2014-02-12

    Heating and Current Drive systems are of outstanding relevance in fusion plasmas, magnetically confined in tokamak devices, as they provide the tools to reach, sustain and control burning conditions. Heating systems based on the electron cyclotron resonance (ECRH) have been extensively exploited on past and present machines DEMO, and the future reactor will require high frequencies. Therefore, high power (≥1MW) RF sources with output frequency in the 200 - 300 GHz range would be necessary. A promising source is the so called Cyclotron Auto-Resonance Maser (CARM). Preliminary results of the conceptual design of a CARM device for plasma heating, carried out at ENEA-Frascati will be presented together with the planned R and D development.

  4. Search for 54-MHz Maser Emission from Interstellar Hydroxyl Using the Long Wavelength Array

    NASA Astrophysics Data System (ADS)

    Hoffman, Ian M.

    2015-01-01

    We present the results of an observational campaign using the Long Wavelength Array (LWA). The level splitting of the rotational ground state of the hydroxyl (OH) molecule gives rise to the four familiar 1.7-GHz (18-cm) transitions by which OH is known in the interstellar medium. There are also two magnetic-dipole transitions among these states at frequencies of 53.2 MHz and 55.1 MHz. These 54-MHz transitions have never been detected astronomically. Because of the relative weakness of the magnetic-dipole radiative process, it is expected that only maser emission will generate a detectable 54-MHz signal. Many of the prevailing pumping models for 18-cm masers are also suggestive of population inversions of the 54-MHz transitions. We have targeted our search toward Galactic locations that are known to exhibit strong 1720-MHz maser emission from OH with the expectation that either of the 54-MHz transitions will also be overpopulated.Using the LWA station LWA1, we have searched the sources NGC 7538, G33.64-0.21, W75N, and Sgr A. For each target we employed 20 hours of integration time in beam-formed mode. We employed 1024 spectral channels in a 250-kHz observing band for each of the two transitions, resulting in a velocity resolution of approximately 1.4 km/s. We did not detect masers in either transition toward any of the sources. Previously reported observations of W75N using LOFAR also resulted in a non-detection; none of the other sources have been searched previously for either 53.2- or 55.1-MHz emission. We discuss the results in the context of previous and ongoing searches for 54-MHz emission.This work is supported by Wittenberg University through the Physics Department. Construction of the LWA has been supported by the Office of Naval Research under Contract N00014-07-C-0147. Support for operations and continuing development of the LWA1 is provided by the National Science Foundation under grants AST-1139963 and AST-1139974 of the University Radio Observatory

  5. [Methanol metabolism in plants].

    PubMed

    Stepanov, S S; Zolotar'ova, O K

    2011-01-01

    Methabolism of methanol in plant organisms is considered in the paper. Enzymes of consecutive oxidation of methanol and enzymes responsible for incorporation of carbon from methanol molecule to methyl groups of phospholipids, carboxylic acids and carbohydrates have been described. The peculiarity of plant organisms is in interaction of reactions of methanol transformation with pathways of photorespiration and C1-metabolism and in the capacity to use methanol carbon to form organic matter through photosynthesis. The inclusion of methanol metabolites in anabolic processes occurs at the level of formaldehyde and formiate. As a result, exogenous methanol at low concentrations can stimulate the photosynthetic efficiency of plants.

  6. Spectra of circularly polarized radiation from astrophysical OH masers

    NASA Technical Reports Server (NTRS)

    Nedoluha, Gerald E.; Watson, William D.

    1990-01-01

    A striking feature of astrophysical masers is the tendency for either one or the other of the circular polarizations to dominate in the radiation from the strong, widely observed masing transitions of OH at 18 cm. Spectral line profiles are calculated for polarized maser radiation due to the combined effects of a velocity gradient and, as is indicated for these transitions, a Zeeman splitting that is at least comparable with the thermal contributions to the breadths of the spectral lines. The resulting spectral features are similar in appearance, including the presence of large net circular polarization and narrow line breadths, to the commonly observed spectra of OH masers in molecular clouds. The calculations presented here are performed as a function of frequency without making the approximations of a large velocity gradient. Rapid cross relaxation, which has been advocated by others for the OH masers, is assumed.

  7. Mega-masers, Dark Energy and the Hubble Constant

    SciTech Connect

    Lo, Fred K.Y.

    2007-10-15

    Powerful water maser emission (water mega-masers) can be found in accretion disks in the nuclei of some galaxies. Besides providing a measure of the mass at the nucleus, such mega-masers can be used to determine the distance to the host galaxy, based on a kinematic model. We will explain the importance of determining the Hubble Constant to high accuracy for constraining the equation of state of Dark Energy and describe the Mega-maser Cosmology Project that has the goal of determining the Hubble Constant to better than 3%. Time permitting, we will also present the scientific capabilities of the current and future NRAO facilities: ALMA, EVLA, VLBA and GBT, for addressing key astrophysical problems

  8. Atomic hydrogen maser active oscillator cavity and bulb design optimization

    NASA Technical Reports Server (NTRS)

    Peters, H. E.; Washburn, P. J.

    1984-01-01

    The performance characteristics and reliability of the active oscillator atomic hydrogen maser depend upon oscillation parameters which characterize the interaction region of the maser, the resonant cavity and atom storage bulb assembly. With particular attention to use of the cavity frequency switching servo (1) to reduce cavity pulling, it is important to maintain high oscillation level, high atomic beam flux utilization efficiency, small spin exchange parameter and high cavity quality factor. It is also desirable to have a small and rigid cavity and bulb structure and to minimize the cavity temperature sensitivity. Curves for a novel hydrogen maser cavity configuration which is partially loaded with a quartz dielectric cylinder and show the relationships between cavity length, cavity diameter, bulb size, dielectric thickness, cavity quality factor, filling factor and cavity frequency temperature coefficient are presented. The results are discussed in terms of improvement in maser performance resulting from particular design choices.

  9. Performance evaluation of the SAO VLG-11 atomic hydrogen masers

    NASA Technical Reports Server (NTRS)

    Levine, M. W.; Vessot, R. F.; Mattison, E. M.

    1978-01-01

    A new generation of frequency standards, the VLG-11 hydrogen maser, has been designed and built at the Smithsonian Astrophysical Observatory (SAO). A comprehensive series of environmental and short-term stability tests on three VLG-11 masers has been completed and evaluated. The test results reported here show substantial improvements over previous hydrogen masers in measured sensitivity to variations in ambient temperature, barometric pressure, and magnetic fields. The maser frequency stability, as represented by the two-sample (Allan) variance, has been measured for averaging times ranging from 1 to 100,00 seconds. The variance is lower than 1 x 10 to the -15th for averaging intervals between 1400 and 20,000 seconds. For times shorter than 4000 seconds, the measured stability data agree remarkably well with theoretical values calculated from thermal noise mechanisms and the 'noise within the linewidth' regime is clearly discernable in the data.

  10. In-Vacuum Dissociator for Atomic-Hydrogen Masers

    NASA Technical Reports Server (NTRS)

    Vessot, R. F.

    1987-01-01

    Thermal control and vacuum sealing achieved while contamination avoided. Simple, relatively inexpensive molecular-hydrogen dissociator for atomic-hydrogen masers used on Earth or in vacuum of space. No air cooling required, and absence of elastomeric O-ring seals prevents contamination. In-vacuum dissociator for atomic hydrogen masers, hydrogen gas in glass dissociator dissociated by radio-frequency signal transmitted from surrounding 3-turn coil. Heat in glass conducted away by contacting metal surfaces.

  11. Timescale algorithms combining cesium clocks and hydrogen masers

    NASA Technical Reports Server (NTRS)

    Breakiron, Lee A.

    1992-01-01

    The United States Naval Observatory (USNO) atomic timescale, formerly based on an ensemble of cesium clocks, is now produced by an ensemble of cesium clocks and hydrogen masers. In order to optimize stability and reliability, equal clock weighting has been replaced by a procedure reflecting the relative, time-varying noise characteristics of the two different types of clocks. Correlation of frequency drift is required, and residual drift is avoided by the eventual complete deweighting of the masers.

  12. Analysis of the electron cyclotron maser instability

    NASA Astrophysics Data System (ADS)

    Kuo, S. P.; Cheo, B. R.

    1984-07-01

    The nonlinear evolution of the electron cyclotron maser instability is investigated analytically, with a focus on the saturation due to phase trapping of gyrating particles in the wave. The equations of motion of a single electron moving in the wave are solved; the collective response of electrons to wave fields is obtained by averaging over the initial random phase distribution; and a single nonlinear equation governing the time evolution of the amplitude is derived self-consistently. Numerical results are presented in graphs and shown to be in good agreement with those of a particle simulation, at a significant savings in computational effort. The results are applicable to the improvement of high-power gyrotron-type mm and sub-mm emitters for radar communications or plasma heating in controlled-fusion devices.

  13. Nonlinear theory of a plasma Cherenkov maser

    SciTech Connect

    Choi, J.S.; Heo, E.G.; Choi, D.I.

    1995-12-31

    The nonlinear saturation state in a plasma Cherenkov maser (PCM) propagating the intense relativistic electron beam through a circular waveguide partially filled with a dense annular plasma, is analyzed from the nonlinear formulation based on the cold fluid-Maxwell equations. We obtain the nonlinear efficiency and the final operation frequency under consideration of the effects of the beam current, the beam energy and the slow wave structure. We show that the saturation mechanism of a PCM instablity is a close correspondence in that of the relativistic two stream instability by the coherent trapping of electrons in a single most-ustable wave. And the optimal conditions in PCM operation are also obtained from performing our nonliear analysis together with computer simulations.

  14. Plasma-filled dielectric Cherenkov maser

    SciTech Connect

    Kosai, H.; Garate, E.P.; Fisher, A. . Dept. of Physics)

    1990-12-01

    The effect of a background plasma on a dielectric Cherenkov maser is examined by solving the linearized, beam-plasma, dielectric-lined waveguide dispersion relation. The results indicate that introduction of the background plasma can produce a higher spatial growth rate for the beam-waveguide instability and can reduce the electric field at the dielectric surface when compared to the system with no background plasma present. Also, it is found that for some sets of waveguide parameters, the TM{sub On} electromagnetic modes can propagate frequencies that are below the background plasma frequency in the system. These modes have a finite cut-off frequency and are different from the Trivelpiece-Gould modes for the system.

  15. Proposal for a room-temperature diamond maser

    PubMed Central

    Jin, Liang; Pfender, Matthias; Aslam, Nabeel; Neumann, Philipp; Yang, Sen; Wrachtrup, Jörg; Liu, Ren-Bao

    2015-01-01

    The application of masers is limited by its demanding working conditions (high vacuum or low temperature). A room-temperature solid-state maser is highly desirable, but the lifetimes of emitters (electron spins) in solids at room temperature are usually too short (∼ns) for population inversion. Masing from pentacene spins in p-terphenyl crystals, which have a long spin lifetime (∼0.1 ms), has been demonstrated. This maser, however, operates only in the pulsed mode. Here we propose a room-temperature maser based on nitrogen-vacancy centres in diamond, which features the longest known solid-state spin lifetime (∼5 ms) at room temperature, high optical pumping efficiency (∼106 s−1) and material stability. Our numerical simulation demonstrates that a maser with a coherence time of approximately minutes is feasible under readily accessible conditions (cavity Q-factor ∼5 × 104, diamond size ∼3 × 3 × 0.5 mm3 and pump power <10 W). A room-temperature diamond maser may facilitate a broad range of microwave technologies. PMID:26394758

  16. A cloud collision model for water maser excitation.

    PubMed

    Tarter, J C; Welch, W J

    1986-06-01

    High-velocity collisions between small, dense, neutral clouds or between a dense cloud and a dense shell can provide the energy source required to excite H2O maser emission. The radiative precursor from the surface of the collisional shock front rapidly diffuses through the cloud, heating the dust grains but leaving the H2 molecules cool. Transient maser emission occurs as the conditions for the Goldreich and Kwan "hot-dust cold-gas" maser pump scheme are realized locally within the cloud. In time the local maser action quenches due to the heating of the H2 molecules by collisions against the grains. Although this model cannot explain the very long-lived steady maser features, it is quite successful in explaining a number of the observed properties of the high-velocity features in such sources as Orion, W51, and W49. In particular, it provides a natural explanation for the rapid time variations, the narrow line widths, juxtaposition of high- and low-velocity features, and the short lifetimes which are frequently observed for the so-called high-velocity maser "bullets" thought to be accelerated by strong stellar winds.

  17. A model for extremely powerful extragalactic water masers

    SciTech Connect

    Wu, Ying-Cheng; Alcock, C.

    1988-08-01

    The reasons for the differences between extremely powerful extragalatic water masers (EPEWMs) and strong Galactic H/sub 2/O masers are discussed. This model quite successfully explains many important characteristics of EPEWMs; the rapid time variations, the broad range and random velocity distribution, the extremely high luminosities, the various heights or widths of features in spectra, the strong infrared radiation from the galaxies, how an active nucleus contributes to an EPEWM, how some parts of EPEWMs producing strong features are pumped, why this pump mechanism can work, and why EPEWMs are different from strong Galactic H/sub 2/O masers. Recent observations of extragalactic water masers which have extremely high luminosities raise the possibility that the stimulated emission rate in the maser emission line in these regions is much higher than in Galactic masers. It is possible that the local stimulated emission rate exceeds the local bandwidth for the radiation. In this case the standard expression relating the photon emission rate to the profile averaged mean intensity does not apply. A new expression for the photon emission rate is derived.

  18. Detection of a weak maser emission pedestal associated with the SiO maser. [in variable late stars

    NASA Technical Reports Server (NTRS)

    Snyder, L. E.; Dickinson, D. F.; Brown, L. W.; Buhl, D.

    1978-01-01

    Results are reported for high-spectral-resolution observations of the v = 1, J = 1-0 SiO maser sources at 43,122.027 MHz (6.95 mm wavelength) associated with the variable stars Omega Cet, NML Tau, VY CMa, R Leo, W Hya, VX Sgr, NML Cyg, and R Cas. A weak underlying maser emission pedestal is clearly observed in the spectra of all but NML Cyg and R Cas. The data indicate that the underlying pedestal of SiO emission appears to originate in a shell-like region around the star, has a thermal appearance even though it must be due to weak maser emission, and appears to be part of the spectral signature of SiO maser emission from late-type stars. It is found that the center velocities of the pedestals may be used to determine stellar radial velocities. Observations of large-scale time variations in the intensity of the Ori A SiO maser and the detection of weak maser pedestals associated with each of the two strong emission-feature groups in Orion are also discussed. It is suggested that the Orion molecular cloud might contain two late-type long-period variable stars that may be semiregular variables.

  19. Graphene based GHz detectors

    NASA Astrophysics Data System (ADS)

    Boyd, Anthony K.; El Fatimy, Abdel; Barbara, Paola; Nath, Anindya; Campbell, Paul M.; Myers-Ward, Rachael; Daniels, Kevin; Gaskill, D. Kurt

    Graphene demonstrates great promise as a detector over a wide spectral range especially in the GHz range. This is because absorption is enhanced due to the Drude contribution. In the GHz range there are viable detection mechanisms for graphene devices. With this in mind, two types of GHz detectors are fabricated on epitaxial graphene using a lift off resist-based clean lithography process to produce low contact resistance. Both device types use asymmetry for detection, consistent with recent thoughts of the photothermoelectric effect (PTE) mechanism. The first is an antenna coupled device. It utilizes two dissimilar contact metals and the work function difference produces the asymmetry. The other device is a field effect transistor constructed with an asymmetric top gate that creates a PN junction and facilitates tuning the photovoltaic response. The response of both device types, tested from 100GHz to 170GHz, are reported. This work was sponsored by the U.S. Office of Naval Research (Award Number N000141310865).

  20. Ground-Based Investigations with the Cryogenic Hydrogen Maser

    NASA Technical Reports Server (NTRS)

    Walsworth, Ronald L.; Mattison, Edward; Vessot, Robert F. C.

    2003-01-01

    The cryogenic hydrogen maser (CHM) developed at the Smithsonian Astrophysical Observatory (SAO) was designed to be functionally similar to SAO room temperature hydrogen masers with appropriate modifications made for operation at cryogenic temperatures. A schematic of the SAO CHM is shown in Figure 1, and a description of this device and its operation follows. A beam of molecular hydrogen is dissociated into atoms at room temperature. The resultant beam of atomic hydrogen is then cooled, magnetically state selected, and focused into a quartz storage bulb centered inside of a microwave cavity resonant with the hydrogen hyperfine transition at 1420 MHz. The quartz storage bulb is coated with a superfluid He-4 film, and both the bulb and cavity are maintained near 0.5 K. The maser signal is coupled out inductively and carried to room temperature via semi-rigid coaxial cable. After passing through a room temperature isolator and preamp, the maser signal is detected with a low-noise heterodyne receiver as used in the room temperature SAO hydrogen masers. The maser temperature is lowered to 0.5 K using a recirculating He-3 refrigerator. This refrigerator consists of several cooling stages: a liquid nitrogen stage at 77 K, a liquid 4He bath at 4.2 K, a pumped He-4 pot at approximately 1.7 K, and the pumped, recirculating He-3 stage at 0.5 K. The atomic hydrogen beam, state selector, storage bulb and cavity are all connected inside a single, maser vacuum chamber (MVC). This space is pumped out from below by a turbo pump. Above the MVC, an inlet to the space allows for the input of flowing superfluid 4He film. External to the MVC is a second, outer vacuum chamber (OVC), maintained for operation of the cryostat and also pumped by a turbo pump. Inside the OVC, there is radiation shielding at 77 K and 1.7 K.

  1. Nuclear Spin Maser at Highly Stabilized Low Magnetic Field and Search for Atomic EDM

    SciTech Connect

    Yoshimi, A.; Asahi, K.; Inoue, T.; Uchida, M.; Hatakeyama, N.; Tsuchiya, M.; Kagami, S.

    2009-08-04

    A nuclear spin maser is operated at a low static field through an active feedback scheme based on an optical nuclear spin detection and succeeding spin control by a transverse field application. The frequency stability of this optical-coupling spin maser is improved by installation of a low-noise current source for a solenoid magnet producing a static magnetic field in the maser operation. Experimental devices for application of the maser to EDM experiment are being developed.

  2. Theoretical models for the polarization of astronomical masers

    NASA Astrophysics Data System (ADS)

    Western, L. R.

    Theoretical models for the creation of linear polarization in astronomical masers are developed. Equations are obtained that describe the transfer of the linearly polarized radiation in two and three dimensional astronomical masers. The transfer equations presented here include both polarization and intersecting maser rays. The transfer equations are integrated to find the intensity of radiation emitted by spheres, spherical shells and thin disks. The calculations show that apparent sizes due to beaming are still quite small and comparable to those obtained using the scalar molecular approximation. Long tails and substantial differences between the two linear polarizations occur in the angular distributions calculated here, especially for disk-like geometries, due to the effect of individual magnetic substates. Further calculations show that small anisotropies (approximately 10%) in the excitation can lead to very high linear polarization (approximately 90%) of the radiation from saturated astronomical masers. Separate calculations are performed for the transfer of the vibrational radiation of molecular SiO through a spherical gas shell. A major result is that magnetic fields alone can not account for the high linear polarization observations of the SiO v = 1, J = 2 ranges to 1 astronomical maser.

  3. Torsion-rotation intensities in methanol

    NASA Astrophysics Data System (ADS)

    Pearson, John

    Methanol exists in numerous kinds of astronomical objects featuring a wide range of local conditions. The light nature of the molecule coupled with the internal rotation of the methyl group with respect to the hydroxyl group results in a rich, strong spectrum that spans the entire far-infrared region. As a result, any modest size observational window will have a number of strong methanol transitions. This has made it the gas of choice for testing THz receivers and to extract the local physical conditions from observations covering small frequency windows. The latter has caused methanol to be dubbed the Swiss army knife of astrophysics. Methanol has been increasingly used in this capacity and will be used even more for subsequent investigations into the Herschel archive, and with SOFIA and ALMA. Interpreting physical conditions on the basis of a few methanol lines requires that the molecular data, line positions, intensities, and collision rates, be complete, consistent and accurate to a much higher level than previously required for astrophysics. The need for highly reliable data is even more critical for modeling the two classes of widespread maser action and many examples of optical pumping through the torsional bands. Observation of the torsional bands in the infrared will be a unique opportunity to directly connect JWST observations with those of Herschel, SOFIA, and ALMA. The theory for the intensities of torsion-rotation transitions in a molecule featuring a single internally rotating methyl group is well developed after 70 years of research. However, other than a recent very preliminary and not completely satisfactory investigation of a few CH3OH torsional bands, this theory has never been experimentally tested for any C3V internal rotor. More alarming is a set of recent intensity calibrated microwave measurements that showed deviations relative to calculations of up to 50% in some ground state rotational transitions commonly used by astronomers to extract

  4. Microwave Spectrum of the Ethanol-Methanol Dimer

    NASA Astrophysics Data System (ADS)

    Finneran, Ian A.; Carroll, Brandon; Mead, Griffin; Blake, Geoffrey

    2016-06-01

    The hydrogen bond donor/acceptor competition in mixed alcohol clusters remains a fundamental question in physical chemistry. Previous theoretical work on the prototype ethanol-methanol dimer has been inconclusive in predicting the energetically preferred structure. Here, we report the microwave spectrum of the ethanol-methanol dimer between 8-18 GHz, using a chirped pulse Fourier transform microwave spectrometer. With the aid of ab initio calculations, 36 transitions have been fit and assigned to a t-ethanol-acceptor, methanol-donor structure in an argon-backed expansion. In a helium-backed expansion, a second excited conformer has been observed, and tentatively assigned to a g-ethanol-acceptor, methanol-donor structure. No ethanol-donor, methanol-acceptor structures have been found, suggesting such structures are energetically disfavored.

  5. Simultaneous VLBA polarimetric observations of the v = {1,2} J = 1-0 and v = 1, J = 2-1 SiO maser emission towards VY CMa II: component-level polarization analysis

    NASA Astrophysics Data System (ADS)

    Richter, L.; Kemball, A.; Jonas, J.

    2016-09-01

    This paper presents a component-level comparison of the polarized v = 1 J = 1-0, v = 2 J = 1-0 and v = 1 J = 2-1 SiO maser emission towards the supergiant star VY CMa at milliarcsecond-scale, as observed using the Very Long Baseline Array at λ = 7 and 3 mm. An earlier paper considered overall maser morphology and constraints on SiO maser excitation and pumping derived from these data. The goal of the current paper is to use the measured polarization properties of individual co-spatial components detected across multiple transitions to provide constraints on several competing theories for the transport of polarized maser emission. This approach minimizes the significant effects of spatial blending. We present several diagnostic tests designed to distinguish key features of competing theoretical models for maser polarization. The number of coincident features is limited by sensitivity however, particularly in the v = 1 J = 2-1 transition at 86 GHz, and deeper observations are needed. Preliminary conclusions based on the current data provide some support for: (i) spin-independent solutions for linear polarization; (ii) the influence of geometry on the distribution of fractional linear polarization with intensity; and, (iii) π/2 rotations in linear polarization position angle arising from transitions across the Van Vleck angle (sin 2θ = 2/3) between the maser line of sight and magnetic field. There is weaker evidence for several enumerated non-Zeeman explanations for circular polarization. The expected 2:1 ratio in circular polarization between J = 1-0 and J = 2-1 predicted by standard Zeeman theory cannot unfortunately be tested conclusively due to insufficient coincident components.

  6. Amplification of OAM radiation by astrophysical masers

    NASA Astrophysics Data System (ADS)

    Gray, M. D.; Pisano, G.; Maccalli, S.; Schemmel, P.

    2014-12-01

    We extend the theory of astrophysical maser propagation through a medium with a Zeeman-split molecular response to the case of a non-uniform magnetic field, and allow a component of the electric field of the radiation in the direction of propagation: a characteristic of radiation with orbital angular momentum. A classical reduction of the governing equations leads to a set of nine differential equations for the evolution of intensity-like parameters for each Fourier component of the radiation. Four of these parameters correspond to the standard Stokes parameters, whilst the other five represent the z-component of the electric field, and its coupling to the conventional components in the x-y-plane. A restricted analytical solution of the governing equations demonstrates a non-trivial coupling of the Stokes parameters to those representing orbital angular momentum: the z-component of the electric field can grow from a background in which only Stokes-I is non-zero. A numerical solution of the governing equations reveals radiation patterns with a radial and angular structure for the case of an ideal quadrupole magnetic field perpendicular to the propagation direction. In this ideal case, generation of radiation orbital angular momentum, like polarization, can approach 100 per cent.

  7. Beam maser measurements of HDO hyperfine structure

    NASA Astrophysics Data System (ADS)

    Fry, H. A.; Kukolich, S. G.

    1982-05-01

    The 431←432, 532←533, and 321←414 transition in HDO were measured in a beam maser spectrometer. Accurate values for rotational transiton frequencies, the deuterium quadrupole coupling tensor, and hydrogen spin-rotation tensor were obtained from the present data combined with previous results on other transitions. Resonance line widths of 2 kHz were obtained for most of the data. Measured quadrupole coupling tensor elements eqQ(D)gg and spin-rotation tensor elements C(X)gg in kHz are as follows: eqQ(D)aa = 276.45±0.88, eqQ(D)bb = -110.97±1.46, eqQ(D)cc = -165.77±1.10, C(D)aa = -1.33±0.20, C(D)bb = -4.38±0.36, C(D)cc = -2.99±0.24, C(H)aa = -58.42±0.47, C(H)bb = -5.46±0.83, C(H)cc = -24.11±0.55.

  8. Cyclotron autoresonance maser in the millimeter region

    NASA Astrophysics Data System (ADS)

    Nikolov, N. A.; Spasovski, I. P.; Kostov, K. G.; Velichkov, J. N.; Spasov, V. A.

    1990-06-01

    This paper investigates the optimal experimental conditions for a cyclotron autoresonance maser (CARM) regime realized by a nonadiabatic magnetic beam pumping in the millimeter wavelength region. In the experiment, a Blumline-type accelerator with a voltage up to 650 kV and maximal current up to 10 kA is used to generate a hollow beam with a pulse duration of 30 ns. The electron beam, emitted from a graphite cathode with a 10-mm diameter, propagates in a cylindrical drift tube of 56 mm diam and a length of 500 mm. The external magnetic field B, provided by a solenoidal magnet, is homogeneous along the drift tube up to a distance of 300 mm from the cathode. The experiment demonstrated the generation of microwave radiation in the time interval from 0.0016 to 0.0023 sec after the switch-on of the external magnetic field. Two maxima of the output microwave power (8 and 10 MW) at a wavelength of 5 and 5.5 mm, respectively, were observed.

  9. Stimulated Raman scattering of water maser lines in astrophysical plasmas

    NASA Astrophysics Data System (ADS)

    Gangadhara, R. T.; Deguchi, Shuji; Lesch, H.

    1999-10-01

    Radiative transfer equations are derived and solved for the stimulated Raman scattering of water maser lines in the astrophysical plasmas with electrons density of about 106-107 cm-3. In stimulated Raman scattering, the energy of the water maser line is transferred to the side band modes: Stokes mode and anti-Stokes mode. The Stokes mode is easily produced by backward Raman scattering while the anti-Stokes mode is created by the interacting intersecting masers in the plasma. The intensity of the Stokes mode is higher than that of the anti-Stokes mode. These side band modes are proposed as explanation for the extreme velocity features observed in the galaxy NGC 4258. The threshold value of the brightness temperature for the Raman scattering is about 1016-1019 K, and it is satisfied in the case of NGC 4258.

  10. Non-Zeeman circular polarization of molecular maser spectral lines

    SciTech Connect

    Houde, Martin

    2014-11-01

    We apply the anisotropic resonant scattering model developed to explain the presence of non-Zeeman circular polarization signals recently detected in the {sup 12}CO (J = 2 → 1) and (J = 1 → 0) transitions in molecular clouds to Stokes V spectra of SiO v = 1 and v = 2, (J = 1 → 0) masers commonly observed in evolved stars. It is found that the observed antisymmetric 'S'- and symmetric '∪'- or '∩'-shaped spectral profiles naturally arise when the maser radiation scatters off populations of foreground molecules located outside the velocity range covered by the background maser radiation. Using typical values for the relevant physical parameters, it is estimated that magnetic field strengths on the order of a few times 15 mG are sufficient to explain the observational results found in the literature.

  11. NASA hydrogen maser accuracy and stability in relation to world standards

    NASA Technical Reports Server (NTRS)

    Peters, H. E.; Percival, D. B.

    1973-01-01

    Frequency comparisons were made among five NASA hydrogen masers in 1969 and again in 1972 to a precision of one part in 10 to the 13th power. Frequency comparisons were also made between these masers and the cesium-beam ensembles of several international standards laboratories. The hydrogen maser frequency stabilities as related to IAT were comparable to the frequency stabilities of individual time scales with respect to IAT. The relative frequency variations among the NASA masers, measured after the three-year interval, were 2 + or - 2 parts in 10 to the 13th power. Thus time scales based on hydrogen masers would have excellent long-term stability and uniformity.

  12. A correlational analysis of the effects of changing environmental conditions on the NR atomic hydrogen maser

    NASA Technical Reports Server (NTRS)

    Dragonette, Richard A.; Suter, Joseph J.

    1992-01-01

    An extensive statistical analysis has been undertaken to determine if a correlation exists between changes in an NR atomic hydrogen maser's frequency offset and changes in environmental conditions. Correlation analyses have been performed comparing barometric pressure, humidity, and temperature with maser frequency offset as a function of time for periods ranging from 5.5 to 17 days. Semipartial correlation coefficients as large as -0.9 have been found between barometric pressure and maser frequency offset. Correlation between maser frequency offset and humidity was small compared to barometric pressure and unpredictable. Analysis of temperature data indicates that in the most current design, temperature does not significantly affect maser frequency offset.

  13. X-band ultralow-noise maser amplifier performance

    NASA Technical Reports Server (NTRS)

    Glass, G. W.; Ortiz, G. G.; Johnson, D. L.

    1994-01-01

    Noise temperature measurements of an 8440-MHz ultralow noise maser amplifier (ULNA) have been performed at subatmospheric, liquid-helium temperatures. The traveling-wave maser was operated while immersed in a liquid helium bath. The lowest input noise temperature measured was 1.43 +/- 0.16 K at a physical temperature of 1.60 K. At this physical temperature, the observed gain per centimeter of ruby was 4.9 dB/cm. The amplifier had a 3-dB bandwidth of 76 MHz.

  14. N-bursty emission from Uranus: A cyclotron maser source?

    NASA Technical Reports Server (NTRS)

    Curran, D. B.; Menietti, J. D.

    1993-01-01

    Ray tracing studies of RX-mode emission from the north polar regions of Uranus indicate that the n-bursty radio emission may have a source along field lines with footprints near the northern magnetic pole (perhaps in the cusp), but not necessarily associated with regions of strong UV emission. This is in contrast with similar studies for the Uranus nightside smooth radio emission, which are believed to be due to the cyclotron maser instability. Source regions can be found for both hollow and filled emission cones and for frequencies well above the local gyrofreuquency implying that mechanisms other than the cyclotron maser mechanism may be operating.

  15. The far distance to G7.47+0.06 from proper motion measurement of H2O masers

    NASA Astrophysics Data System (ADS)

    Yamauchi, Aya; Yamashita, Kazuyoshi; Honma, Mareki; Sunada, Kazuyoshi; Nakagawa, Akiharu; Ueno, Yuji

    2016-08-01

    We report on a distance measurement of 22 GHz H2O maser features associated with an ultra-compact H II region G7.47+0.06 using VERA (VLBI Exploration of Radio Astrometry). Since the source is located farther away than 10 kpc, it turned out to be difficult to derive the distance from annual parallax measurement. Meanwhile, we clearly detected the source's proper motion parallel to the Galactic plane. The proper motion is μ = -5.03 ± 0.07 mas yr-1 and is approaching the Galactic center. We applied a new method to determine the source distance based on absolute proper motions. Considering uncertainties of the Galactic rotation curve and the solar peculiar motion, the detected proper motion leads to a source distance of D = 20 ± 2 kpc, demonstrating that astrometric observation can provide an accurate distance measurement at a 10% level even for sources too distant to measure the annual parallax. Lastly, we scale the physical parameters of the H II region estimated in a previous paper to be 20 kpc, and show that the H2O maser features are associated with a massive star-forming region corresponding to the spectral type of O5.5.

  16. The Methanol Economy Project

    SciTech Connect

    Olah, George; Prakash, G. K.

    2014-02-01

    The Methanol Economy Project is based on the concept of replacing fossil fuels with methanol generated either from renewable resources or abundant natural (shale) gas. The full methanol cycle was investigated in this project, from production of methanol through bromination of methane, bireforming of methane to syngas, CO2 capture using supported amines, co-electrolysis of CO2 and water to formate and syngas, decomposition of formate to CO2 and H2, and use of formic acid in a direct formic acid fuel cell. Each of these projects achieved milestones and provided new insights into their respective fields.

  17. OH maser outburst in the W3 nebula

    NASA Astrophysics Data System (ADS)

    Gosachinskij, I. V.; Grenkov, S. A.; Ipatov, A. V.; Rakhimov, I. A.

    2016-07-01

    We report the results of three-year long observations of OH masers at 1665 MHz in the W3(OH) source carried out with the 32-m antenna of Svetloe Radio Astronomical Observatory.We found that the strongest activity during the period from December 2011 through March 2012 was exhibited by the region at radial velocity -46.2km s-1. The region showed no activity in the ensuing time. The most striking outburst was the event that occurred on January 23, 2013 at UT 03:27. At that time the flux of the region increased by a factor of seven in 90 s, and then decreased down to the initial level. Such a time scale yields the upper estimate of 0.18 AU (2.7 × 1012 cm) for the linear size of the maser dot. In 2013-2014 intensity variations were found the -47.6 and -45.1km s-1 components with time scales on the order of 10 hours and anticorrelated behavior of the left- and right-hand polarization fluxes. This is the first time that such phenomena have been found in the behavior of OH maser emission, and they cannot be explained by any existing models of maser variability.

  18. SiO and CH3OH mega-masers in NGC 1068

    NASA Astrophysics Data System (ADS)

    Wang, Junzhi; Zhang, Jiangshui; Gao, Yu; Zhang, Zhi-Yu; Li, Di; Fang, Min; Shi, Yong

    2014-11-01

    Maser is an acronym for microwave amplification by stimulated emission of radiation; in astronomy mega-masers are masers in galaxies that are ≥106 times more luminous than typical galactic maser sources. Observational studies of mega-masers can help us to understand their origins and characteristics. More importantly, mega-masers can be used as diagnostic tracers to probe the physical properties of their parent galaxies. Since the late 1970s, only three types of molecules have been found to form mega-masers: H2O, OH and H2CO. Here we report the detection of both SiO and CH3OH mega-masers near the centre of Seyfert 2 galaxy NGC 1068 at millimetre wavelengths, obtained using the IRAM 30-m telescope. We argue that the SiO mega-maser originated from the nuclear disk and the CH3OH mega-maser originated from shock fronts. High-resolution observations in the future will enable us to investigate AGN feedback and determine the masses of central supermassive black holes in such galaxies.

  19. SiO and CH3OH mega-masers in NGC 1068.

    PubMed

    Wang, Junzhi; Zhang, Jiangshui; Gao, Yu; Zhang, Zhi-Yu; Li, Di; Fang, Min; Shi, Yong

    2014-11-11

    Maser is an acronym for microwave amplification by stimulated emission of radiation; in astronomy mega-masers are masers in galaxies that are ≥ 10(6) times more luminous than typical galactic maser sources. Observational studies of mega-masers can help us to understand their origins and characteristics. More importantly, mega-masers can be used as diagnostic tracers to probe the physical properties of their parent galaxies. Since the late 1970s, only three types of molecules have been found to form mega-masers: H2O, OH and H2CO. Here we report the detection of both SiO and CH3OH mega-masers near the centre of Seyfert 2 galaxy NGC 1068 at millimetre wavelengths, obtained using the IRAM 30-m telescope. We argue that the SiO mega-maser originated from the nuclear disk and the CH3OH mega-maser originated from shock fronts. High-resolution observations in the future will enable us to investigate AGN feedback and determine the masses of central supermassive black holes in such galaxies.

  20. SiO and CH3OH mega-masers in NGC 1068

    PubMed Central

    Wang, Junzhi; Zhang, Jiangshui; Gao, Yu; Zhang, Zhi-Yu; Li, Di; Fang, Min; Shi, Yong

    2014-01-01

    Maser is an acronym for microwave amplification by stimulated emission of radiation; in astronomy mega-masers are masers in galaxies that are ≥106 times more luminous than typical galactic maser sources. Observational studies of mega-masers can help us to understand their origins and characteristics. More importantly, mega-masers can be used as diagnostic tracers to probe the physical properties of their parent galaxies. Since the late 1970s, only three types of molecules have been found to form mega-masers: H2O, OH and H2CO. Here we report the detection of both SiO and CH3OH mega-masers near the centre of Seyfert 2 galaxy NGC 1068 at millimetre wavelengths, obtained using the IRAM 30-m telescope. We argue that the SiO mega-maser originated from the nuclear disk and the CH3OH mega-maser originated from shock fronts. High-resolution observations in the future will enable us to investigate AGN feedback and determine the masses of central supermassive black holes in such galaxies. PMID:25386834

  1. SiO and CH3OH mega-masers in NGC 1068.

    PubMed

    Wang, Junzhi; Zhang, Jiangshui; Gao, Yu; Zhang, Zhi-Yu; Li, Di; Fang, Min; Shi, Yong

    2014-01-01

    Maser is an acronym for microwave amplification by stimulated emission of radiation; in astronomy mega-masers are masers in galaxies that are ≥ 10(6) times more luminous than typical galactic maser sources. Observational studies of mega-masers can help us to understand their origins and characteristics. More importantly, mega-masers can be used as diagnostic tracers to probe the physical properties of their parent galaxies. Since the late 1970s, only three types of molecules have been found to form mega-masers: H2O, OH and H2CO. Here we report the detection of both SiO and CH3OH mega-masers near the centre of Seyfert 2 galaxy NGC 1068 at millimetre wavelengths, obtained using the IRAM 30-m telescope. We argue that the SiO mega-maser originated from the nuclear disk and the CH3OH mega-maser originated from shock fronts. High-resolution observations in the future will enable us to investigate AGN feedback and determine the masses of central supermassive black holes in such galaxies. PMID:25386834

  2. An H2O Maser survey towards BGPS sources in the Outer Galaxy

    NASA Astrophysics Data System (ADS)

    Xi, Hong-Wei; Zhou, Jian-Jun; Esimbek, Jarken; Wu, Gang; He, Yu-Xin; Ji, Wei-Guang; Tang, Xiao-Ke; Yuan, Ye

    2016-06-01

    We performed an H2O maser survey towards 274 Bolocam Galactic Plane Survey (BGPS) sources with 85° < l < 193° using the Nanshan 25 m radio telescope. We detected 25 H2O masers, and five of them are new detections. The detection rate of H2O masers in our sample is 9% which is very low. The detection rate of H2O masers increases as the 1.1 mm flux density of BGPS sources increases, and both the peak flux density and luminosity of H2O masers increase as the sources evolve. The detection rate of H2O masers toward BGPS sources without HCO+ emission is low. The BGPS sources associated with both H2O and CH3OH masers seem to be more compact than those only associated with H2O masers. This indicates that the sources with both masers may be in a relatively later evolutionary stage. The strongest H2O maser source G133.715+01.217, also well known as W3 IRS 5 which has a flux density of 2.9×103 Jy, was detected at eight different nearby positions. By measuring the correlation between the flux densities of these H2O masers and their angular distance from the true source location, we get the influence radius r = \\frac{1}{{0.8}}log ≤ft({\\frac{{F_0}}{{3\\text{rms}}}}\\right). For our observations, strong sources can be detected anywhere within this radius. It is helpful to determine whether or not a weak maser nearby the strong maser is a true detection.

  3. A 2.3-GHz low-noise cryo-FET amplifier

    NASA Technical Reports Server (NTRS)

    Loreman, J.

    1988-01-01

    A cryogenic cooled, low-noise Field Effect Transistor (FET) amplifier assembly for use at 2.2 to 2.3 GHz was developed for the DSN to meet the requirements of a Very Long Baseline Interferometry (VLBI) upgrade. An amplifier assembly was developed at JPL that uses a commercial closed-cycle helium refrigerator (CCR) to cool a FET amplifier to an operating temperature of 15 K. A cooled probe waveguide-to-coaxial transition similar to that used in the research and development Ultra-Low-Noise S-band Traveling Wave Maser (TWM) is used to minimize input line losses. Typical performance includes an input flange equivalent noise contribution of 14.5 K, a gain slope of less than 0.05 dB/MHz across a bandwidth of 2.2 to 2.3 GHz, an input VSWR of 1.5:1 at 2.25 GHz, and an insertion gain of 45 + or - 1 dB across the bandwidth of 2.2 to 2.3 GHz. Three 2.3 GHz FET/CCR assemblies were delivered to the DSN in the spring of 1987.

  4. Methanol partial oxidation reformer

    DOEpatents

    Ahmed, S.; Kumar, R.; Krumpelt, M.

    1999-08-17

    A partial oxidation reformer is described comprising a longitudinally extending chamber having a methanol, water and an air inlet and an outlet. An igniter mechanism is near the inlets for igniting a mixture of methanol and air, while a partial oxidation catalyst in the chamber is spaced from the inlets and converts methanol and oxygen to carbon dioxide and hydrogen. Controlling the oxygen to methanol mole ratio provides continuous slightly exothermic partial oxidation reactions of methanol and air producing hydrogen gas. The liquid is preferably injected in droplets having diameters less than 100 micrometers. The reformer is useful in a propulsion system for a vehicle which supplies a hydrogen-containing gas to the negative electrode of a fuel cell. 7 figs.

  5. Methanol partial oxidation reformer

    DOEpatents

    Ahmed, Shabbir; Kumar, Romesh; Krumpelt, Michael

    1999-01-01

    A partial oxidation reformer comprising a longitudinally extending chamber having a methanol, water and an air inlet and an outlet. An igniter mechanism is near the inlets for igniting a mixture of methanol and air, while a partial oxidation catalyst in the chamber is spaced from the inlets and converts methanol and oxygen to carbon dioxide and hydrogen. Controlling the oxygen to methanol mole ratio provides continuous slightly exothermic partial oxidation reactions of methanol and air producing hydrogen gas. The liquid is preferably injected in droplets having diameters less than 100 micrometers. The reformer is useful in a propulsion system for a vehicle which supplies a hydrogen-containing gas to the negative electrode of a fuel cell.

  6. Methanol partial oxidation reformer

    DOEpatents

    Ahmed, Shabbir; Kumar, Romesh; Krumpelt, Michael

    2001-01-01

    A partial oxidation reformer comprising a longitudinally extending chamber having a methanol, water and an air inlet and an outlet. An igniter mechanism is near the inlets for igniting a mixture of methanol and air, while a partial oxidation catalyst in the chamber is spaced from the inlets and converts methanol and oxygen to carbon dioxide and hydrogen. Controlling the oxygen to methanol mole ratio provides continuous slightly exothermic partial oxidation reactions of methanol and air producing hydrogen gas. The liquid is preferably injected in droplets having diameters less than 100 micrometers. The reformer is useful in a propulsion system for a vehicle which supplies a hydrogen-containing gas to the negative electrode of a fuel cell.

  7. Methanol partial oxidation reformer

    DOEpatents

    Ahmed, S.; Kumar, R.; Krumpelt, M.

    1999-08-24

    A partial oxidation reformer is described comprising a longitudinally extending chamber having a methanol, water and an air inlet and an outlet. An igniter mechanism is near the inlets for igniting a mixture of methanol and air, while a partial oxidation catalyst in the chamber is spaced from the inlets and converts methanol and oxygen to carbon dioxide and hydrogen. Controlling the oxygen to methanol mole ratio provides continuous slightly exothermic partial oxidation reactions of methanol and air producing hydrogen gas. The liquid is preferably injected in droplets having diameters less than 100 micrometers. The reformer is useful in a propulsion system for a vehicle which supplies a hydrogen-containing gas to the negative electrode of a fuel cell. 7 figs.

  8. Phase and gain measurements in a distributed-loss cyclotron-resonance maser amplifier

    NASA Astrophysics Data System (ADS)

    Kesar, Amit; Jerby, Eli

    2002-03-01

    The control of gain and phase delay in a cyclotron-resonance maser (CRM) amplifier is essential for a variety of applications. In this experiment, the gain and phase-delay variations are measured with respect to controlling parameters; the electron-beam current and the axial magnetic field. Following Chu et al. [Phys. Rev. Lett. 74, 1103 (1995)], the CRM amplifier comprises of a distributed-loss waveguide to enable high gain without oscillations. Our experiment yields an amplification up to 26 dB, and a phase-delay control range of 360°. In order to keep a fixed gain with the varying phase delay, the two controlling parameters (i.e., the solenoid field and the beam current) are operated together in a compensating mode. The experiment is conducted in a frequency of 7.3 GHz, with an electron beam of 18-kV voltage and 0.25-0.4-A current. The experimental results are compared with a theoretical model. Practical implementations of gain and phase control in CRM devices are discussed.

  9. Experimental demonstration of a high-power slow wave electron cyclotron maser utilizing corrugated metal structure

    SciTech Connect

    Minami, K.; Ogura, K.; Kurashina, K; Kim, W.; Watanabe, Tsuguhiro; Carmel, Y.; Destler, W.W.; Granatstein, V.L.

    1994-12-31

    High-power microwave (HPM) sources based on electron cyclotron resonance (ECR) such as gyrotrons are fast wave devices and velocity component of electron beam perpendicular to guiding magnetic field is the origin of HPM. HPM sources based on Cherenkove mechanism are slow wave devices and can be driven by a beam without initial perpendicular velocity. The authors present here the experimental result that seems to be the first demonstration of high-power slow wave electron cyclotron maser (ECM) consisting of a large diameter sinusoidally corrugated metal waveguide driven by a beam with predominant parallel velocity. The designed size parameters of slow wave structure (SWS) are as follows: average radius 30 mm, corrugation pitch 3.4 mm, its amplitude h = 1.7 mm and total length 238 mm. They use an annular beam with radius 26.3 mm, energy 55 keV, current 200 A in their experiment. Expected Cherenkov oscillation frequency of TM01 mode is 20 GHz. The observed high-power microwaves can be quantitatively explained by a backward wave oscillation with Cherenkov mechanism enhanced by positive feedback of anomalous Doppler slow cyclotron wave. In conclusion, the slow wave ECM presented here will be a competitive candidate against gyrotrons for generating multi-MW millimeter microwaves available in fusion plasma research.

  10. WATER MASERS IN THE ANDROMEDA GALAXY: THE FIRST STEP TOWARD PROPER MOTION

    SciTech Connect

    Darling, Jeremy

    2011-05-01

    We have detected and confirmed five water maser complexes in the Andromeda Galaxy (M31) using the Green Bank Telescope. These masers will provide the high brightness temperature point sources needed for proper motion studies of M31, enabling measurement of its full three-dimensional velocity vector and its geometric distance via proper rotation. The motion of M31 is the keystone of Local Group dynamics and a gateway to the dark matter profiles of galaxies in general. Our survey for water masers selected 206 luminous compact 24 {mu}m emitting regions in M31 and was sensitive enough to detect any maser useful for {approx}10 {mu}as yr{sup -1} astrometry. The newly discovered masers span the isotropic luminosity range (0.3-1.9) x 10{sup -3} L{sub sun} in single spectral components and are analogous to luminous Galactic masers. The masers are distributed around the molecular ring, including locations close to the major and minor axes, which is nearly ideal for proper motion studies. We find no correlation between 24 {mu}m luminosity and water maser luminosity, suggesting that while water masers arise in star-forming regions, the nonlinear amplification pathways and beamed nature of the water masers means that they are not predictable based on IR luminosity alone. This suggests that there are additional bright masers to be found in M31. We predict that the geometric distance and systemic proper motion of M31 can be measured in 2-3 years with current facilities. A 'moving cluster' observation of diverging masers as M31 approaches the Galaxy may be possible in the long term.

  11. Correlation of circumstellar SiO maser spot distribution with the stellar light curve

    NASA Astrophysics Data System (ADS)

    Oyadomari, M.; Imai, H.; Nagayama, T.; Oyama, T.; Matsumoto, N.; Nakashima, J.; Cho, S.-H.

    2016-07-01

    We have investigated the distributions of silicon monoxide (SiO) v = 2 and v = 3 J = 1 → 0 masers around long-period variables (LPVs) in VLBI observations using the VLBI Exploration of Radio Astrometry (VERA) combined with the Nobeyama 45 m telescope. We find some examples of correlation of a maser spot distribution with the stellar light curve, which may provide a clue to elucidating the pumping mechanism of circumstellar SiO masers.

  12. The cyclotron maser theory of AKR and Z-mode radiation. [Auroral Kilometric Radiation

    NASA Technical Reports Server (NTRS)

    Wu, C. S.

    1985-01-01

    The cyclotron maser mechanism which may be responsible for the generation of auroral kilometric radiation and Z-mode radiation is discussed. Emphasis is placed on the basic concepts of the cyclotron maser theory, particularly the relativistic effect of the cyclotron resonance condition. Recent development of the theory is reviewed. Finally, the results of a computer simulation study which helps to understand the nonlinear saturation of the maser instability are reported.

  13. Dietary methanol and autism.

    PubMed

    Walton, Ralph G; Monte, Woodrow C

    2015-10-01

    The authors sought to establish whether maternal dietary methanol during pregnancy was a factor in the etiology of autism spectrum disorders. A seven item questionnaire was given to women who had given birth to at least one child after 1984. The subjects were solicited from a large primary care practice and several internet sites and separated into two groups - mothers who had given birth to a child with autism and those who had not. Average weekly methanol consumption was calculated based on questionnaire responses. 550 questionnaires were completed by women who gave birth to a non-autistic child. On average these women consumed 66.71mg. of methanol weekly. 161 questionnaires were completed by women who had given birth to an autistic child. The average estimated weekly methanol consumption for this group was 142.31mg. Based on the results of the Wilcoxon rank sum-test, we see a significant difference between the reported methanol consumption rates of the two groups. This study suggests that women who have given birth to an autistic child are likely to have had higher intake of dietary sources of methanol than women who have not. Further investigation of a possible link of dietary methanol to autism is clearly warranted.

  14. Two New SiO Maser Sources in High-Mass Star-forming Regions

    NASA Astrophysics Data System (ADS)

    Cho, Se-Hyung; Yun, Youngjoo; Kim, Jaeheon; Liu, Tie; Kim, Kee-Tae; Choi, Minho

    2016-08-01

    Silicon monoxide (SiO) masers are rare in star-forming regions, with the exception of five known SiO maser sources. However, we detected two new SiO maser sources from infrared-loud clumps of the high-mass star-forming regions G19.61‑0.23 and G75.78+0.34. High angular resolution observations toward G19.61‑0.23 suggest that the deeply embedded young stellar object (YSO) of SMA1 is powering the SiO masers. In addition, the SiO v = 1, J = 1 \\to 0 line shows four spike features, while the v = 2 maser shows combined features of one spike and broad wing components, implying energetic activities of the YSO of SMA1 in the G19.61‑0.23 hot molecular core. The SiO v = 0, J = 2 \\to 1 emission shows bipolar outflows in the NE–SW direction with respect to the center of the SiO maser source. A high angular resolution map of the SiO v = 1, J = 2 \\to 1 maser in G75.78+0.34 shows that the SiO maser is associated with the CORE source at the earliest stage of high-mass star formation. Therefore, the newly detected SiO masers and their associated outflows will provide good probes for investigating this early high-mass star formation.

  15. Nonlinear saturation characteristics of a dielectric Cherenkov maser

    SciTech Connect

    Choi, J.S.; Heo, E.G.; Choi, D.I.

    1995-12-31

    The nonlinear saturation state in a dielectric Cherenkov maser (DCM) with the TM mode and the intense relativistic electron beam is analyzed from the nonlinear formulation based on the cold fluid-Maxwell equations. We obtain the nonlinear efficiency and the final operation frequency under consideration of the effects of the beam current, the beam energy and the dielectric materials and show that the characteristics of a DCM instablity has a strong resemblance to that of the relativistic two stream instability by the coherent trapping of electrons in a single most-ustable wave. Finally, the nonlinear analysis shows that the Cherenkov maser operation with a lower-energy beam can be more efficient in the higher frequency regime for the case of the high power DCM with a high current.

  16. Massive Black Holes in Water Maser Merging Galaxies

    NASA Astrophysics Data System (ADS)

    Darling, Jeremy

    2014-09-01

    We propose to observe the massive black holes (MBHs) in two merging galaxies identified by water masers. Both galaxies offer the opportunity to study the mass and accretion rate of MBHs in the early (IC 750) and late (IIZw40) stages of merging, crucial times for black hole growth and feedback. IIZw40, an advanced merger of two gas-rich dwarf galaxies, is a crucial window on the growth of black holes in the early universe. IC 750 is a spiral in a close pair with interaction-induced morphology, possibly activating the AGN, and a valuable case study of the initial conditions for major mergers and the growth of MBHs. Chandra observations will identify central black holes (perhaps two in IIZw40), constrain the maser excitation, and measure the accretion rate, key for feedback studies.

  17. CEPHEID VARIABLES IN THE MASER-HOST GALAXY NGC 4258

    SciTech Connect

    Hoffmann, Samantha L.; Macri, Lucas M.

    2015-06-15

    We present results of a ground-based survey for Cepheid variables in NGC 4258. This galaxy plays a key role in the Extragalactic Distance Scale due to its very precise and accurate distance determination via very long baseline interferometry observations of water masers. We imaged two fields within this galaxy using the Gemini North telescope and the Gemini Multi-Object Spectrograph, obtaining 16 epochs of data in the Sloan Digital Sky Survey gri bands over 4 yr. We carried out point-spread function photometry and detected 94 Cepheids with periods between 7 and 127 days, as well as an additional 215 variables which may be Cepheids or Population II pulsators. We used the Cepheid sample to test the absolute calibration of theoretical gri Period–Luminosity relations and found good agreement with the maser distance to this galaxy. The expected data products from the Large Synoptic Survey Telescope should enable Cepheid searches out to at least 10 Mpc.

  18. POLARIZED EMISSION FROM SiO MASERS IN IK Tauri

    SciTech Connect

    Cotton, W. D.; Ragland, S.; Danchi, W. C.

    2011-08-01

    We present high spatial and frequency resolution images of the SiO masers in Stokes I, Q, U, and V around the asymptotic giant branch star IK Tau and describe and exploit a new technique for making accurate calibration of Stokes V. This technique also resulted in improved images of Stokes I. An evaluation of the results suggests that the circular polarization is neither the result of Zeeman splitting nor an alternate propagation effect. The pattern of circular and linear polarization across the maser lines shows no tendency toward that expected for simple Zeeman splitting. The fractional circular polarization greatly exceeds that expected from the alternate mechanism. The overall shape of the masing ring has changed from the elliptical form repeatedly observed over the last decade and a half.

  19. Methanol Cannon Demonstrations Revisited.

    ERIC Educational Resources Information Center

    Dolson, David A.; And Others

    1995-01-01

    Describes two variations on the traditional methanol cannon demonstration. The first variation is a chain reaction using real metal chains. The second example involves using easily available components to produce sequential explosions that can be musical in nature. (AIM)

  20. The Water Maser in II Zw 96: Scientific Justification

    SciTech Connect

    Wiggins, Brandon Kerry

    2015-08-06

    We propose a VLBI search to image and locate the water emission in II Zw 96. We propose 3 sites within II Zw 96 for VLBI followup (see the proposed target listing below). We request 2.5 hours of on-source integration time with the VLBA per source. The array will achieve ~ 65µJy sensitivity in K band in this time which will be sufficient to detect luminous water maser features.

  1. FEM (Free Electron Maser) for tokamak: Final report

    SciTech Connect

    Not Available

    1987-01-01

    This paper studies the feasibility of a microwave source for heating a tokamak reactor. The free electron maser (FEM) shows great promise for being this source. The topics covered in this paper are microwave generation with FEM, efficiency enhancement, parameter scaling, space charge scaling, beam energy spread and efficiency scaling, electron beam line with energy recovery, achromatic bend, multi-stage depressed voltage electron beam collector, and development plans. 12 refs., 10 figs., 5 tabs. (LSP)

  2. Precision timekeeping using a small passive hydrogen maser

    NASA Technical Reports Server (NTRS)

    Walls, F. L.; Howe, D. A.

    1981-01-01

    The timekeeping ability of a prototype passive hydrogen maser which is a factor of 5 smaller in size, weight, and cost than any previously designed, was compared to UTC (NBS) based on 10 cesium frequency standards including a large primary standard, NBS-4. The frequency of the prototype was monitored as a function of source pressure, cavity temperature, microwave power, modulation width, and magnetic field. Based on these measurements, a frequency stability of better than 6 x 10 to the -15 power was expected, implying a timekeeping ability of order 0.5 ns/day. Measurements vs UTC(NBS) indicate a joint timekeeping a stability of order 1.2 ns/day. Simultaneous measurements made between NBS-4, UTC(6600), and the small passive me maser show peak to peak time variations of the small maser vs UTC(6600) was 10 ns for the full 32 days if the average rate and drift are considered. Frequency stability of the small prototype vs UTC (NBS) was to 1.1 x 10 to the -14th power for tau = 1 to 8 days.

  3. The system design of a rubidium maser frequency standard

    NASA Technical Reports Server (NTRS)

    Xiong, C. X.

    1984-01-01

    The Rubidium Maser Frequency Standard is a precision frequency source with excellent short-term stability. A type PBR-II Rb maser frequency standard was developed by the Beijing Institute of Radio Metrology and Measurement (BIRMM). The time-domain frequency stability (two-sample variance) of this frequency standard is less than 1/5 times 10 to the 13th power for t=10ms yields 1.0s, fh=1.0 KHz. Two PBR-II frequency standards were used as reference frequency sources in a frequency stability measurement system. Some important system characteristics for the PBR-II Rb maser frequency standard such as phase noise and frequency stability transfer characteristics are discussed. Furthermore, the design of the frequency standard for optimum frequency stability of the output signal; the choice of a voltage controlled crystal oscillator for the frequency standard; the design of the phase-locked loop; and the frequency stability test results on the PBR-II are discussed.

  4. Ground-Based Investigations with the Cryogenic Hydrogen Maser

    NASA Technical Reports Server (NTRS)

    Walsworth, Ronald L.; Mattison, Edward; Vessot, Robert F. C.

    2001-01-01

    The room temperature hydrogen maser is an active atomic oscillator used as a high-frequency-stability local oscillator for radio astronomy, metrology, and spacecraft navigation, and in tests of fundamental physics. The cryogenic hydrogen maser (CHM) operates at 0.5 K, employing superfluid helium-coated walls to store the masing hydrogen atoms. We are investigating whether the CHM may provide better frequency stability than the room temperature hydrogen maser: one to three orders of magnitude improvement may be possible because of greatly reduced thermal noise and larger signal power. Exceptional frequency stability will be required for spacecraft tracking in future deep-space missions, for space-based tests of relativity and gravitation, and for local (i.e., flywheel) oscillators used with absolute frequency standards such as laser-cooled atomic fountains and linear ion traps. These new devices are passive high-resolution frequency discriminators. Alone, they cannot function as superior atomic clocks; their effective operation depends on being integrated with an active local oscillator with excellent short term stability - such as that possible with the CHM.

  5. Numerical investigation of auroral cyclotron maser processes

    SciTech Connect

    Speirs, D. C.; Ronald, K.; McConville, S. L.; Gillespie, K. M.; Phelps, A. D. R.; Cross, A. W.; Robertson, C. W.; Whyte, C. G.; He, W.; Bingham, R.; Vorgul, I.; Cairns, R. A.; Kellett, B. J.

    2010-05-15

    When a mainly rectilinear electron beam is subject to significant magnetic compression, conservation of magnetic moment results in the formation of a horseshoe shaped velocity distribution. It has been shown that such a distribution is unstable to cyclotron emission and may be responsible for the generation of auroral kilometric radiation--an intense rf emission sourced at high altitudes in the terrestrial auroral magnetosphere. Particle-in-cell code simulations have been undertaken to investigate the dynamics of the cyclotron emission process in the absence of cavity boundaries with particular consideration of the spatial growth rate, spectral output and rf conversion efficiency. Computations reveal that a well-defined cyclotron emission process occurs albeit with a low spatial growth rate compared with waveguide bounded simulations. The rf output is near perpendicular to the electron beam with a slight backward-wave character reflected in the spectral output with a well defined peak at 2.68 GHz, just below the relativistic electron cyclotron frequency. The corresponding rf conversion efficiency of 1.1% is comparable to waveguide bounded simulations and consistent with the predictions of kinetic theory that suggest efficient, spectrally well defined emission can be obtained from an electron horseshoe distribution in the absence of radiation boundaries.

  6. VLA Monitoring of the Water Masers in the Water Fountain Nebula IRAS16342-3814

    NASA Astrophysics Data System (ADS)

    Fagrelius, Eric; Claussen, M.; Sahai, R.; Morris, M.

    2010-01-01

    This study of water maser emission from the "water fountain" pre-planetary nebula IRAS16342-3814 used 1.35 cm observations made with the Very Large Array of the National Radio Astronomy Observatory. Seven observing epochs over one year sampled an LSR velocity range of 370 km/sec (since masers are known over a range of more than 250 km/s). The wide range reveals maser spots at several different velocities, including the well-known features at extreme red-shifted ( LSR +180 km/sec) and blue-shifted ( LSR -66 km/sec) velocities, relative to the stellar velocity. Identification of maser spots over time gives a better picture of the growth, orientation, and physical nature of the bipolar outflow lobes. The data reveals maser spots at previously unreported velocities ( LSR -10 to +5 km/s). Some maser spots identified in the past are no longer seen. Masers from different velocity ranges differ in intensity by 100x. Within the year, some individual masers vary in intensity by 10x. Besides revealing growth and decline of the different masers, we hoped to observe the separation of the extremely shifted masers. Previous studies measured about 3 arcsec in breadth. The angular resolution of the VLA images was typically 0.7 - 1.2 arcseconds, and the data were imaged with 0.2 arcsec per pixel, so we expected to resolve the separation of extremely shifted masers by 15 pixels. This separation was not observed. Existing, near-simultaneous observations with the Very Large Baseline Array will be used to investigate this expected separation. This research was performed under the National Science Foundation's Research Experience for Teachers program during the summer of 2009. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. RS and MM were funded by a Long Term Space Astrophysics award from NASA for this work

  7. Complete the development and construction of a spaceborne hydrogen maser clock

    NASA Technical Reports Server (NTRS)

    Vessot, Robert F. C.

    1990-01-01

    The objective, to complete the development of an engineering model of a spaceborne hydrogen maser, was successfully achieved. A layout of the maser and detail drawings of the physics package was completed during the first 7 months of the contract. A computer model was made for the maser's thermal design. Using numerical computations, heater resistances were established for 7 temperature controlled zones. The physics package includes: a vacuum manifold that houses four sorption pumps capable of scavenging hydrogen for 4 years, a titanium vacuum tank housing the cavity, metallic seals for all vacuum joints, an RF dissociator within the vacuum envelope, a two-layer printed circuit solenoid and four layers of moly-permalloy magnetic shields. Problems were encountered and overcome in the procurements of the PC solenoid and the magnetic shields. After completion of the fabrication of the maser's components, the maser was assembled using these parts and other components made available by SAO, NRL, and NASA from earlier development work. In March, 1990, the vacuum system was assembled, and by May the maser assembly was completed. The magnetic shielding was poor and the shields were removed, reannealed by a local vendor, and the maser was reassembled. The maser began tests in early June and has been oscillating since that time. The test results of the maser are very good and a life test of the maser is being conducted. It is anticipated that the development and construction of a maser to be tested in space under a new contract from NASA's Marshall Space Flight Center will continue.

  8. Physico-Chemical Research on the Sounding Rocket Maser 13

    NASA Astrophysics Data System (ADS)

    Lockowandt, Christian; Kemi, Stig; Abrahamsson, Mattias; Florin, Gunnar

    MASER is a sounding rocket platform for short-duration microgravity experiments, providing the scientific community with an excellent microgravity tool. The MASER programme has been running by SSC from 1987 and has up to 2012 provided twelve successful flights for microgravity missions with 6-7 minutes of microgravity, the g-level is normally below 1x10-5 g. The MASER 13 is planned to be launched in spring 2015 from Esrange Space Center in Northern Sweden. The rocket will carry four ESA financed experiment modules. The MASER 13 vehicle will be propelled by the 2-stage solid fuel VSB-30 rocket motor, which provided the 390 kg payload with an apogee of 260 km and 6 and a half minutes of microgravity. Swedish Space Corporation carries out the MASER missions for ESA and the program is also available for other customers. The payload comprise four different experiment modules of which three could be defined as physic-chemical research; XRMON-SOL, CDIC-3, MEDI. It also comprises the Maser Service Module and the recovery system. The Service Module provided real-time 5 Mbps down-link of compressed experiment digital video data from the on-board cameras, as well as high-speed housekeeping telemetry data. XRMON-SOL In this experiment the influence of gravity on the formation of an equiaxed microstructure will be investigated. Special attention will be put on the aspect of nucleation, segregation and impingement. The experiment scope is to melt and solidify an AlCu-alloy sample in microgravity. The solidification will be performed in an isothermal environment. The solidification process will be monitored and recorded with X-ray image during the whole flight, images will also be down-linked to ground for real-time monitoring and possible interaction. CDIC-3 The goal is to study in migrogravity the spatio-temporal dynamics of a chemical front travelling in a thin solution layer open to the air and specifically the respective role of Marangoni and density-related hydrodynamic

  9. CRC handbook of laser science and technology. Volume 1. Lasers and masers

    SciTech Connect

    Weber, M.J.

    1982-01-01

    This book describes various types of lasers and masers. The following topics are discussed in detail: types and comparisons of laser sources, crystal and glass lasers, semiconductor lasers, organic dye and other liquid lasers, free-electron and x-ray lasers, masers and laser safety.

  10. Methanol in dark clouds

    NASA Technical Reports Server (NTRS)

    Friberg, P.; Hjalmarson, A.; Madden, S. C.; Irvine, W. M.

    1988-01-01

    The first observation of methanol in cold dark clouds TMC 1, L 134 N, and B 335 is reported. In all three clouds, the relative abundance of methanol was found to be in the range of 10 to the -9th (i.e., almost an order of magnitude more abundant than acetaldehyde), with no observable variation between the clouds. Methanol emission showed a complex velocity structure; in TMC 1, clear indications of non-LTE were observed. Dimethyl ether was searched for in L 134 N; the upper limit of the column density of dimethyl ether in L 134 N was estimated to be 4 x 10 to the 12th/sq cm, assuming 5 K rotation temperature and LTE. This limit makes the abundance ratio (CH3)2O/CH3OH not higher than 1/5, indicating that dimethyl ether is not overabundant in this dark cloud.

  11. HIGH-MASS STAR FORMATION IN THE NEAR AND FAR 3 kpc ARMS

    SciTech Connect

    Green, J. A.; McClure-Griffiths, N. M.; Caswell, J. L.; Voronkov, M. A.; Ellingsen, S. P.; Fuller, G. A.; Quinn, L.

    2009-05-10

    We report on the presence of 6.7 GHz methanol masers, known tracers of high-mass star formation, in the 3 kpc arms of the inner Galaxy. We present 49 detections from the Methanol Multibeam Survey, the largest Galactic plane survey for 6.7 GHz methanol masers, which coincide in longitude, latitude, and velocity with the recently discovered far-side 3 kpc arm and the well-known near-side 3 kpc arm. The presence of these masers is significant evidence for high-mass star formation actively occurring in both 3 kpc arms.

  12. Handel's Maser-Soliton Theory of ball lightning: The creation of stable three-dimensional cavitons by an atmospheric maser within an open resonator

    NASA Astrophysics Data System (ADS)

    Carlson, Glenn Andrew

    This dissertation develops details of Handel's Maser-Soliton Theory of ball lightning. The atmosphere between a thundercloud and the Earth's surface is modeled as an idealized stable open resonator with water vapor as the active medium and the thundercloud and Earth's surface as reflecting surfaces. The stable resonator generates a maser beam that narrows to the beam waist at the Earth's surface, which is assumed to be planar. Two candidate rotational transitions are identified within the ν1ν 2ν3 = 010 vibrational band of water having wavelengths of 13.9 cm and 1.12 cm, and relevant spectroscopic parameters are retrieved from the HITRAN 2008 molecular spectroscopic database. The maser is modeled as a continuously pumped four-level maser that includes the effects of nonradiative relaxation due to molecular collisions and of microwave absorption in atmospheric oxygen. Since maser spiking is highly unlikely to occur due to the high rate of collisional relaxation at normal atmospheric pressure, the electrical breakdown of air must be achieved by the steady state output of the atmospheric maser. A parametric analysis is performed to relate the size of the atmospheric maser to the pumping rate needed to create a steady state population inversion sufficient to generate maser radiation intense enough at the beam waist to result in the electrical breakdown of air. The analysis suggests that electric field intensities at the beam waist sufficient to cause electrical breakdown of air could only be created through huge pumping rates (˜105 to 107 times the critical pumping rate) and only for the most highly curved clouds (g ≈ 0) that give the narrowest beam waists.

  13. Confirmation of the association of water masers with the planetary nebulae IRAS 12405-6219 and IRAS 16333-4807

    NASA Astrophysics Data System (ADS)

    Uscanga, Lucero; Gomez, Jose F.; Miranda, Luis F.; Torrelles, Jose M.; Gomez, Yolanda; Anglada, Guillem; Tafoya, Daniel; Suarez, Olga; Boumis, Panayotis

    2011-10-01

    Water maser emission was not expected to persist in the planetary nebulae (PNe) phase, when the envelope is starting to be ionized. However three PNe, in their very first stages of evolution, have been confirmed to have water maser emission. These objects are key to understand the AGB to PN transition and, in particular, the role that disks and collimated outflows play in the formation of PNe. We have carried out a survey for water masers toward evolved stars, using the antennas at Robledo (Spain) and Parkes (Australia), which resulted in 5 new maser detections toward sources classified as PNe. VLA observations of the Robledo detections allowed us to confirm the third case of a water-maser-emitting PN. Here we propose to perform H2O maser and continuum observations with ATCA, to obtain accurate positions of the two Parkes detections, and confirm the association between the water masers and the PN candidates.

  14. Confirmation of the association of water masers with the planetary nebulae IRAS 12405-6219 and IRAS 16333-4807

    NASA Astrophysics Data System (ADS)

    Uscanga, Lucero; Gomez, Jose F.; Miranda, Luis F.; Torrelles, Jose M.; Anglada, Guillem; Tafoya, Daniel; Suarez, Olga; Boumis, Panayotis

    2012-10-01

    Water maser emission was not expected to persist in the planetary nebulae (PNe) phase, when the envelope is starting to be ionized. However three PNe, in their very first stages of evolution, have been confirmed to have water maser emission. These objects are key to understand the AGB to PN transition and, in particular, the role that disks and collimated outflows play in the formation of PNe. We have carried out a survey for water masers toward evolved stars, using the antennas at Robledo (Spain) and Parkes (Australia), which resulted in 5 new maser detections toward sources classified as PNe. VLA observations of the Robledo detections allowed us to confirm the third case of a water-maser-emitting PN. Here we propose to perform H2O maser and continuum observations with ATCA, to obtain accurate positions of the two Parkes detections, and confirm the association between the water masers and the PN candidates.

  15. A WATER MASER AND NH{sub 3} SURVEY OF GLIMPSE EXTENDED GREEN OBJECTS

    SciTech Connect

    Cyganowski, C. J.; Koda, J.; Towers, S.; Meyer, J. Donovan; Rosolowsky, E.; Egusa, F.; Momose, R.; Robitaille, T. P.

    2013-02-10

    We present the results of a Nobeyama 45 m H{sub 2}O maser and NH{sub 3} survey of all 94 northern GLIMPSE extended green objects (EGOs), a sample of massive young stellar objects (MYSOs) identified based on their extended 4.5 {mu}m emission. We observed the NH{sub 3}(1,1), (2,2), and (3,3) inversion lines, and detected emission toward 97%, 63%, and 46% of our sample, respectively (median rms {approx} 50 mK). The H{sub 2}O maser detection rate is 68% (median rms {approx} 0.11 Jy). The derived H{sub 2}O maser and clump-scale gas properties are consistent with the identification of EGOs as young MYSOs. To explore the degree of variation among EGOs, we analyze subsamples defined based on mid-infrared (MIR) properties or maser associations. H{sub 2}O masers and warm dense gas, as indicated by emission in the higher-excitation NH{sub 3} transitions, are most frequently detected toward EGOs also associated with both Class I and II CH{sub 3}OH masers. Ninety-five percent (81%) of such EGOs are detected in H{sub 2}O (NH{sub 3}(3,3)), compared to only 33% (7%) of EGOs without either CH{sub 3}OH maser type. As populations, EGOs associated with Class I and/or II CH{sub 3}OH masers have significantly higher NH{sub 3} line widths, column densities, and kinetic temperatures than EGOs undetected in CH{sub 3}OH maser surveys. However, we find no evidence for statistically significant differences in H{sub 2}O maser properties (such as maser luminosity) among any EGO subsamples. Combining our data with the 1.1 mm continuum Bolocam Galactic Plane Survey, we find no correlation between isotropic H{sub 2}O maser luminosity and clump number density. H{sub 2}O maser luminosity is weakly correlated with clump (gas) temperature and clump mass.

  16. Mixing properties of the one-atom maser

    NASA Astrophysics Data System (ADS)

    Bruneau, Laurent

    2014-06-01

    We study the relaxation properties of the quantized electromagnetic field in a cavity under repeated interactions with single two-level atoms, so-called one-atom maser. We improve the ergodic results obtained in Bruneau and Pillet (J Stat Phys 134(5-6):1071-1095, 2009) and prove that, whenever the atoms are initially distributed according to the canonical ensemble at temperature , all the invariant states are mixing. Under some non-resonance condition this invariant state is known to be thermal equilibirum at some renormalized temperature and we prove that the mixing is then arbitrarily slow, in other words that there is no lower bound on the relaxation speed.

  17. Backward wave cyclotron-maser emission in the auroral magnetosphere.

    PubMed

    Speirs, D C; Bingham, R; Cairns, R A; Vorgul, I; Kellett, B J; Phelps, A D R; Ronald, K

    2014-10-10

    In this Letter, we present theory and particle-in-cell simulations describing cyclotron radio emission from Earth's auroral region and similar phenomena in other astrophysical environments. In particular, we find that the radiation, generated by a down-going electron horseshoe distribution is due to a backward-wave cyclotron-maser emission process. The backward wave nature of the radiation contributes to upward refraction of the radiation that is also enhanced by a density inhomogeneity. We also show that the radiation is preferentially amplified along the auroral oval rather than transversely. The results are in agreement with recent Cluster observations. PMID:25375713

  18. Maser radiometer for cosmic background radiation anisotropy measurements

    NASA Astrophysics Data System (ADS)

    Fixsen, D. J.; Wilkinson, D. T.

    1982-06-01

    A maser amplifier was incorporated into a low noise radiometer designed to measure large-scale anisotropy in the 3 deg K microwave background radiation. To minimize emission by atmospheric water vapor and oxygen, the radiometer is flown in a small balloon to an altitude to 25 km. Three successful flights were made - two from Palestine, Texas and one from Sao Jose dos Campos, Brazil. Good sky coverage is important to the experiment. Data from the northern hemisphere flights has been edited and calibrated.

  19. Kinetic analysis of two dimensional metallic grating Cerenkov maser

    SciTech Connect

    Zhao Ding

    2011-08-15

    The dispersion relation of two dimensional metallic grating Cerenkov maser has been given by using kinetic analysis, in which the influence of electron movement is directly considered without using an equivalent dielectric medium assumption. The effects of structural parameters and beam state on the interaction gain and synchronous frequency have also been investigated in detail by numerical calculations. To an illustrative case, the quantitative relations produced from varying the gap distance between electron beam and metallic grating, beam current, electron transverse to axial velocity ratio, and electron axial velocity spread have been obtained. The developed method can be used to predict the real interaction system performances.

  20. Maser radiometer for cosmic background radiation anisotropy measurements

    NASA Technical Reports Server (NTRS)

    Fixsen, D. J.; Wilkinson, D. T.

    1982-01-01

    A maser amplifier was incorporated into a low noise radiometer designed to measure large-scale anisotropy in the 3 deg K microwave background radiation. To minimize emission by atmospheric water vapor and oxygen, the radiometer is flown in a small balloon to an altitude to 25 km. Three successful flights were made - two from Palestine, Texas and one from Sao Jose dos Campos, Brazil. Good sky coverage is important to the experiment. Data from the northern hemisphere flights has been edited and calibrated.

  1. Backward wave cyclotron-maser emission in the auroral magnetosphere.

    PubMed

    Speirs, D C; Bingham, R; Cairns, R A; Vorgul, I; Kellett, B J; Phelps, A D R; Ronald, K

    2014-10-10

    In this Letter, we present theory and particle-in-cell simulations describing cyclotron radio emission from Earth's auroral region and similar phenomena in other astrophysical environments. In particular, we find that the radiation, generated by a down-going electron horseshoe distribution is due to a backward-wave cyclotron-maser emission process. The backward wave nature of the radiation contributes to upward refraction of the radiation that is also enhanced by a density inhomogeneity. We also show that the radiation is preferentially amplified along the auroral oval rather than transversely. The results are in agreement with recent Cluster observations.

  2. Methanol from coal

    NASA Technical Reports Server (NTRS)

    Miller, D. R.

    1978-01-01

    Economic feasibility of methanol or methyl fuel produced from coal using existing technology is discussed. Other factors considered include environmental, safety, toxicity, transportation, so storage, ease of burning, and retrofitting of present boilers. Demonstrations of its uses as a boiler fuel and as a turbine fuel are cited.

  3. A Study of the Variability of Water Maser Emission in a Sample of Young Stellar Objects

    NASA Astrophysics Data System (ADS)

    Trinidad, M. A.; Rojas, V.; Plascencia, J. C.; Ricalde, A.; Curiel, S.; Rodríguez, L. F.

    We present results of water maser observations in a sample of young stellar objects. The observations were made using the Haystack 37 m antenna during a span of time of about eight months. The sample was selected to study the variability of the water maser emission in young sources with far-infrared luminosities between 260 and 2.5×10^4 L[sun]. The results are shown in a series of plots that allow the analysis of the variation of the maser emission and to discuss the global properties of the sample. The results show that in all the observed sources the water maser emission varies with time. Based on the observed variability, the sample shows two kinds of behavior. About half of the sources show large variations in the peak flux density of at least one feature (by more than an order of magnitude) in time spans between one and several months, while in all the sources there is more than one feature where the changes in peak flux density are smaller (by less than a factor of 10) but in similar time scales. Finally, the variability of the observed water maser emission does not show a clear periodicity pattern in time and we do not find a clear relationship between the luminosity of the sources and the water maser variability. >From a statistical point of view, the H[2]O maser variability can be described as due to small (10%) Gaussian fluctuations in the line opacity.

  4. Accelerating a water maser face-on jet from a high mass young stellar object

    NASA Astrophysics Data System (ADS)

    Motogi, Kazuhito; Sorai, Kazuo; Honma, Mareki; Hirota, Tomoya; Hachisuka, Kazuya; Niinuma, Kotaro; Sugiyama, Koichiro; Yonekura, Yoshinori; Fujisawa, Kenta

    2016-10-01

    We report on long-term single-dish and VLBI monitoring for intermittent flare activities of a dominant blue-shifted H2O maser associated with a southern high mass young stellar object, G353.273+0.641. Bi-weekly single-dish monitoring using the Hokkaido University Tomakomai 11 m radio telescope has shown that a systematic acceleration continues over four years beyond the lifetime of individual maser features. This fact suggests that the H2O maser traces a region where molecular gas is steadily accelerated. There were five maser flares during the five years of monitoring, and maser distributions in four of them were densely monitored by VLBI Exploration of Radio Astrometry (VERA). The overall distribution of the maser features suggests the presence of a bipolar jet, with the 3D kinematics indicating that it is almost face-on (inclination angle of ˜ 8°-17° from the line of sight). Most maser features were recurrently excited within a region of 100×100 au2 around the radio continuum peak, while their spatial distributions significantly varied between each flare. This confirms that episodic propagations of outflow shocks recurrently invoke intermittent flare activities. We also measured annual parallax, deriving a source distance of 1.70^{+0.19}_{-0.16} kpc that is consistent with the commonly used photometric distance.

  5. Water Masers and YSOs in H II Regions: Preliminary Results of a VLA survey

    NASA Astrophysics Data System (ADS)

    Healy, K. R.; Claussen, M. J.; Hester, J. J.

    2000-12-01

    We present preliminary results of a two-epoch VLA survey for water maser activity associated with young stars in several H II regions: NGC 2264, S140, M16, and M20. In all, we detected 4 masers previously reported in the literature and 4 previously unknown. Of those previously unreported, 3 show clear association with active star formation. In M20, we found a ~1 Jy maser coincident with a 2MASS K-band point source. This object is not visible at shorter wavelengths. This maser appears to be previously undetected. We tentatively identify this object as a heavily obscured YSO. In M16, we detected 3 new masers in and around the columns in the Eagle Nebula. One of the masers is not associated with any obvious optical, near-infrared, or radio emission. As yet, we do not have an identification for this source. The other two masers are associated with cloud cores seen in sub-mm SCUBA images of White et al. (1999). We discuss the significance of these protostars in the star formation environment of M16. K.R.H. acknowledges support from the Arizona State University NASA Space Grant Program. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

  6. Cosmic Fire Hydrants: The nature of 11 high-velocity water masers in our Galaxy

    NASA Astrophysics Data System (ADS)

    Harvey-Smith, Lisa; Walsh, Andrew; Breen, Shari; Green, jimi; Purcell, Cormac; Longmore, Steve N.

    2015-08-01

    Water masers act as excellent cosmic markers for the motion of dynamic astronomical regions such as young massive circumstellar disks and outflows from evolved stars. Studying fast water masers gives us a very rare insight into two very a significant stages of stellar evolution.In high-mass star forming regions, water masers are formed in the walls of conical outflows, in collimated jets and in some cases under the influence of a circumstellar disk wind. High-resolution studies of these masers therefore enable us to probe the accretion mechanism for massive star formation. Water masers in post-Asymptotic Giant Branch (AGB) stars probe the very brief phase of aspherical mass-loss before the outer layers of the circumstellar envelope are ionised and the star becomes a Planetary Nebula. The process of aspherical Planetary Nebula formation is still the subject of considerable debate, with the binary hypothesis and magnetic collimation of fast winds being the leading explanations at present.We selected the eleven water maser sites from the H2O Southern Galactic Plane Survey that have differential radial velocities greater than 200 km/s. The water maser sites were subsequently re-observed at higher angular resolution to localise the maser positions with respect to other astronomical emission in the vicinity and where possible, to probe the internal velocity gradients. We conducted a multi-wavelength study of these sites of water masers to determine the stage of stellar evolution, their physical size and a number of other attributes. We present several significant new results and open questions that demand further investigation.

  7. Using Two-Dimensional Distributed Feedback for Synchronization of Radiation from Two Parallel-Sheet Electron Beams in a Free-Electron Maser.

    PubMed

    Arzhannikov, A V; Ginzburg, N S; Kalinin, P V; Kuznetsov, S A; Malkin, A M; Peskov, N Yu; Sergeev, A S; Sinitsky, S L; Stepanov, V D; Thumm, M; Zaslavsky, V Yu

    2016-09-01

    A spatially extended planar 75 GHz free-electron maser with a hybrid two-mirror resonator consisting of two-dimensional upstream and traditional one-dimensional downstream Bragg reflectors and driven by two parallel-sheet electron beams 0.8  MeV/1  kA has been elaborated. For the highly oversized interaction space (cross section 45×2.5 vacuum wavelengths), the two-dimensional distributed feedback allowed realization of stable narrow-band generation that includes synchronization of emission from both electron beams. As a result, spatially coherent radiation with the output power of 30-50 MW and a pulse duration of ∼100  ns was obtained in each channel. PMID:27661696

  8. Using Two-Dimensional Distributed Feedback for Synchronization of Radiation from Two Parallel-Sheet Electron Beams in a Free-Electron Maser

    NASA Astrophysics Data System (ADS)

    Arzhannikov, A. V.; Ginzburg, N. S.; Kalinin, P. V.; Kuznetsov, S. A.; Malkin, A. M.; Peskov, N. Yu.; Sergeev, A. S.; Sinitsky, S. L.; Stepanov, V. D.; Thumm, M.; Zaslavsky, V. Yu.

    2016-09-01

    A spatially extended planar 75 GHz free-electron maser with a hybrid two-mirror resonator consisting of two-dimensional upstream and traditional one-dimensional downstream Bragg reflectors and driven by two parallel-sheet electron beams 0.8 MeV /1 kA has been elaborated. For the highly oversized interaction space (cross section 45 ×2.5 vacuum wavelengths), the two-dimensional distributed feedback allowed realization of stable narrow-band generation that includes synchronization of emission from both electron beams. As a result, spatially coherent radiation with the output power of 30-50 MW and a pulse duration of ˜100 ns was obtained in each channel.

  9. Using Two-Dimensional Distributed Feedback for Synchronization of Radiation from Two Parallel-Sheet Electron Beams in a Free-Electron Maser.

    PubMed

    Arzhannikov, A V; Ginzburg, N S; Kalinin, P V; Kuznetsov, S A; Malkin, A M; Peskov, N Yu; Sergeev, A S; Sinitsky, S L; Stepanov, V D; Thumm, M; Zaslavsky, V Yu

    2016-09-01

    A spatially extended planar 75 GHz free-electron maser with a hybrid two-mirror resonator consisting of two-dimensional upstream and traditional one-dimensional downstream Bragg reflectors and driven by two parallel-sheet electron beams 0.8  MeV/1  kA has been elaborated. For the highly oversized interaction space (cross section 45×2.5 vacuum wavelengths), the two-dimensional distributed feedback allowed realization of stable narrow-band generation that includes synchronization of emission from both electron beams. As a result, spatially coherent radiation with the output power of 30-50 MW and a pulse duration of ∼100  ns was obtained in each channel.

  10. Van Der Pol model of a Cerenkov maser

    SciTech Connect

    Kleckner, M.; Ron, A.; Botton, M.

    1995-12-31

    A non-linear analysis of a Cerenkov maser is presented. The system consists of a ring configuration of a cylindrical waveguide filled with a dielectric material. A single transverse-magnetic mode is assumed to propagate in the system. A low-density pencil electron beam travels in part of the ring, confined by a strong axial magnetic field. Using the single-particle description for the beam and the wave equation for the field, we obtain a set of two coupled non-linear differential equations describing the slowly varying amplitude and phase of the electromagnetic mode. The gain per path is assumed to be small and the spatial growth of the field is neglected. The resulting time dependent amplitude includes the exponential gain of the linear stage and the saturation to its maximum value. The time dependent frequency is also calculated. The two equations are combined to a single Van Der Pol equation with a non-linear restoring force. This description demonstrates the similarities and differences between the Cerenkov maser and other lasing systems.

  11. Comparison of Three Statistical Classification Techniques for Maser Identification

    NASA Astrophysics Data System (ADS)

    Manning, Ellen M.; Holland, Barbara R.; Ellingsen, Simon P.; Breen, Shari L.; Chen, Xi; Humphries, Melissa

    2016-04-01

    We applied three statistical classification techniques-linear discriminant analysis (LDA), logistic regression, and random forests-to three astronomical datasets associated with searches for interstellar masers. We compared the performance of these methods in identifying whether specific mid-infrared or millimetre continuum sources are likely to have associated interstellar masers. We also discuss the interpretability of the results of each classification technique. Non-parametric methods have the potential to make accurate predictions when there are complex relationships between critical parameters. We found that for the small datasets the parametric methods logistic regression and LDA performed best, for the largest dataset the non-parametric method of random forests performed with comparable accuracy to parametric techniques, rather than any significant improvement. This suggests that at least for the specific examples investigated here accuracy of the predictions obtained is not being limited by the use of parametric models. We also found that for LDA, transformation of the data to match a normal distribution led to a significant improvement in accuracy. The different classification techniques had significant overlap in their predictions; further astronomical observations will enable the accuracy of these predictions to be tested.

  12. Linear quadratic stochastic control of atomic hydrogen masers.

    PubMed

    Koppang, P; Leland, R

    1999-01-01

    Data are given showing the results of using the linear quadratic Gaussian (LQG) technique to steer remote hydrogen masers to Coordinated Universal Time (UTC) as given by the United States Naval Observatory (USNO) via two-way satellite time transfer and the Global Positioning System (GPS). Data also are shown from the results of steering a hydrogen maser to the real-time USNO mean. A general overview of the theory behind the LQG technique also is given. The LQG control is a technique that uses Kalman filtering to estimate time and frequency errors used as input into a control calculation. A discrete frequency steer is calculated by minimizing a quadratic cost function that is dependent on both the time and frequency errors and the control effort. Different penalties, chosen by the designer, are assessed by the controller as the time and frequency errors and control effort vary from zero. With this feature, controllers can be designed to force the time and frequency differences between two standards to zero, either more or less aggressively depending on the application.

  13. Historical Cost Curves for Hydrogen Masers and Cesium Beam Frequency and Timing Standards

    NASA Technical Reports Server (NTRS)

    Remer, D. S.; Moore, R. C.

    1985-01-01

    Historical cost curves were developed for hydrogen masers and cesium beam standards used for frequency and timing calibration in the Deep Space Network. These curves may be used to calculate the cost of future hydrogen masers or cesium beam standards in either future or current dollars. The cesium beam standards are decreasing in cost by about 2.3% per year since 1966, and hydrogen masers are decreasing by about 0.8% per year since 1978 relative to the National Aeronautics and Space Administration inflation index.

  14. Saturation and beaming in astrophysical masers. II - The fully saturated limit

    NASA Technical Reports Server (NTRS)

    Alcock, C.; Ross, R. R.

    1985-01-01

    Radiative transfer in fully saturated maser clouds has been investigated using the 'four-stream' model equations of Alcock and Ross (1985). It is shown that a modest elongation of the maser cloud produces a substantial asymmetry in the maser output. The ratio of output fluxes in different directions is a strong function of the ratio of the corresponding chord lengths across the cloud. Arguments are presented that the asymmetries reported here for the 'four-stream' models closely mimic the asymmetries that should be expected in a real master cloud.

  15. A Search for Compact OH(1720 MHz) Maser Emission toward Southern Supernova Remnants

    NASA Astrophysics Data System (ADS)

    Moffett, D. A.

    1999-12-01

    The last four fields from a single dish OH(1720 MHz) maser survey toward supernova remnants (Frail et al. 1996; Green et al. 1997) have been imaged at high spatial (6'') and spectral (0.34 km/s) resolution to search for compact maser emission. An additional remnant, G347.5-0.5, discovered after the survey, was also searched. Only one of the fields, toward SNR G332.0+0.2, was found to have compact OH(1720) maser emission; however, it lies well outside the radio shell.

  16. Hydrogen bond competition in the ethanol-methanol dimer.

    PubMed

    Finneran, Ian A; Carroll, P Brandon; Mead, Griffin J; Blake, Geoffrey A

    2016-08-10

    Previous theoretical work on the ethanol-methanol dimer has been inconclusive in predicting the preferred hydrogen bond donor/acceptor configuration. Here, we report the microwave spectrum of the dimer using a chirped pulse Fourier transform microwave spectrometer from 8-18 GHz. In an argon-backed expansion, 50 transitions have been assigned to a trans-ethanol-acceptor/methanol-donor structure that is likely stabilized by a secondary weak C-HO hydrogen bond. A higher energy conformer was observed in a helium-backed expansion and tentatively assigned to a gauche-ethanol-acceptor/methanol-donor structure. No ethanol-donor/methanol-acceptor dimers have been found, suggesting such interactions are energetically disfavored. A preliminary analysis of the A-E splitting due to the internal rotation of the methanol methyl group in the ground state species is also presented. We find evidence of the Ubbelohde effect in the measured A-E splittings of three deuterated isotopologues and the normal species of this conformer. PMID:27472828

  17. Eucomic acid methanol monosolvate

    PubMed Central

    Li, Guo-Qiang; Li, Yao-Lan; Wang, Guo-Cai; Liang, Zhi-Hong; Jiang, Ren-Wang

    2011-01-01

    In the crystal structure of the title compound [systematic name: 2-hy­droxy-2-(4-hy­droxy­benz­yl)butane­dioic acid methanol monosolvate], C11H12O6·CH3OH, the dihedral angles between the planes of the carboxyl groups and the benzene ring are 51.23 (9) and 87.97 (9)°. Inter­molecular O—H⋯O hydrogen-bonding inter­actions involving the hy­droxy and carb­oxy­lic acid groups and the methanol solvent mol­ecule give a three-dimensional structure. PMID:22091200

  18. Cherenkov maser operation at 1-2 mm wavelengths

    SciTech Connect

    Garate, E.P.; Moustaizis, S.; Buzzi, J.M.; Rouille, C.; Lamain, H.

    1986-05-19

    The interaction of a dense n approx 10/sup 12//cc, mildly relativistic (1.8 < gamma < 3) electron beam and a cylindrical, dielectric-lined waveguide produced tunable microwave radiation in the 150-310 GHZ frequency range with an estimated power output of 500 kW at 150 GHz and 10 kW at 310 GHz. The measured output frequency agrees well with the frequency for which the phase velocity of the TM/sub 1/ mode of the dielectric-lined guide is synchronous with the electron-beam velocity.

  19. Methanol in dark clouds.

    PubMed

    Friberg, P; Madden, S C; Hjalmarson, A; Irvine, W M

    1988-01-01

    We report observations, for the first time, of the 2(0) - 1(0)A+ and E, 2(-1) - 1(-1) E, and 1(0) - 0(0)A+ lines of methanol (CH3OH) in three dark cold clouds, TMC1, L134N, and B335. The CH3OH emission is extended in these clouds and shows a complex velocity structure. Clear indications of non LTE excitation are observed in TMC 1. Estimated column densities are a few 10(13) cm-2. Although less abundant than formaldehyde (H2CO), methanol is almost an order of magnitude more abundant than acetaldehyde (CH3CHO), in these clouds. Dimethyl ether was searched for in L134N, to an upper limit of 4 10(12) cm-2 (3 sigma). Implications for dark cloud excitation and chemistry are discussed. A new, more accurate, rest frequency 96741.39(0.01) MHz is determined for the 2(0) - 1(0) A+ E line of methanol.

  20. The toxicity of methanol

    SciTech Connect

    Tephly, T.R. )

    1991-01-01

    Methanol toxicity in humans and monkeys is characterized by a latent period of many hours followed by a metabolic acidosis and ocular toxicity. This is not observed in most lower animals. The metabolic acidosis and blindness is apparently due to formic acid accumulation in humans and monkeys, a feature not seen in lower animals. The accumulation of formate is due to a deficiency in formate metabolism which is, in turn, related, in part, to low hepatic tetrahydrofolate (H{sub 4}folate). An excellent correlation between hepatic H{sub 4} folate and formate oxidation rates has been shown within and across species. Thus, humans and monkeys possess low hepatic H{sub 4}folate levels, low rates of formate oxidation and accumulation of formate after methanol. Formate, itself, produces blindness in monkeys in the absence of metabolic acidosis. In addition to low hepatic H{sub 4}folate concentrations, monkeys and humans also have low hepatic 10-formyl H{sub 4}folate dehydrogenase levels, the enzyme which is the ultimate catalyst for conversion of formate to carbon dioxide. This review presents the basis for the role of folic acid-dependent reactions in the regulation of methanol toxicity.

  1. California methanol assessment. Volume 2: Technical report

    NASA Technical Reports Server (NTRS)

    Otoole, R.; Dutzi, E.; Gershman, R.; Heft, R.; Kalema, W.; Maynard, D.

    1983-01-01

    Energy feedstock sources for methanol; methanol and other synfuels; transport, storage, and distribution; air quality impact of methanol use in vehicles, chemical methanol production and use; methanol utilization in vehicles; methanol utilization in stationary applications; and environmental and regulatory constraints are discussed.

  2. A 20-GHz IMPATT transmitter

    NASA Technical Reports Server (NTRS)

    Chan, J. L.; Sun, C.

    1983-01-01

    The engineering development of a solid state transmitter amplifier operating in the 20 GHz frequency band. The development effort involved a variety of disciplines including IMPATT device development, circulator design, simple and multiple diode circuits designs, and amplifier integration and test.

  3. The saturation of the electron-cyclotron maser instability and the interpretation of solar millisecond spikes

    NASA Technical Reports Server (NTRS)

    Aschwanden, M. J.

    1990-01-01

    A self-consistent numeric two-dimensional code of the kinetic wave-particle equations developed to investigate the maser dynamics in the solar context is applied to solar millisecond-spike observations in order to improve the diagnostic capabilities of the theory of the electron-cyclotron maser instablitity. Attention is given to the inhomogeneity of the magnetic field selecting magneto-ionic modes with relatively short saturation lengths and suppressing mechanisms such as collisional deflection, free-free absorption, and gyroresonance absorption. The time scales of maser saturation in respect to time scales of global particle changes in a magnetic loop are covered, relevant observations of solar millisecond spikes are described, and the interpretation in terms of physical parameters deduced from the quasi-linear maser simulations are presented. It is demonstrated that the quasi-linear simulations make it possible to constrain the physical parameters from the observed time scale and frequency.

  4. State of the art and future directions for the atomic hydrogen maser

    NASA Technical Reports Server (NTRS)

    Vessot, Robert F. C.

    1990-01-01

    The present status of technology development for atomic hydrogen masers (H-masers) is reviewed. The limitations to frequency stability and accuracy are discussed with emphasis on the problems associated with cavity resonator instability and the lack of reproducibility and stability of the storage volume wall coating frequency shift. New types of coating developed in the Soviet Union and better, cavity resonator materials, are expected to make possible frequency at the 10(exp -16) level at 10(exp 4) sec. Better control of systematic effects should extend the long-term stability to levels better than 10(exp -15) for intervals beyond one day. Present use of H-masers as flywheel oscillators in timekeeping systems is discussed as is the outlook for the future cryogenic and room temperature H-masers as flywheel oscillators to operate very high resolution frequency discriminators based on the newly evolving technology of trapped and cooled ions and atoms.

  5. PV Diagrams For The Maser Emission Coming From A Keplerian Ring

    NASA Astrophysics Data System (ADS)

    Uscanga, Lucero; Cantó, J.; Raga, A. C.

    2008-03-01

    We studied the maser emission coming from a thin, planar, gaseous ring in Keplerian rotation around a central mass observed edge-on. Assuming that the absorption coefficient follows a power-law dependence on the distance from the central mass (κ=κ0r-q), we calculated position-velocity (PV) diagrams for the strongest maser emission using different values of the exponent q. We found that, depending on the value of q, these diagrams can be qualitatively different. Specifically, when qɭ the PV diagram is qualitatively similar to the one observed for the water maser emission in the nucleus of the galaxy NGC 4258. This suggests that the absorption coefficient should be a decreasing function of the distance from the central mass in order to have significant emission coming from the inner edge of the amplifying ring, and hence explain the form of the PV diagram delineated by the water masers in this galaxy.

  6. Distribution of SiO and OH Maser Stars in the Galactic Plane

    NASA Astrophysics Data System (ADS)

    Jiang, Bi-Wei; Jia, Shu-Mei

    2001-04-01

    The observational results of the Nobeyama 45-m SiO maser survey and the Arecibo 305-m OH maser survey are assembled for an analysis of the distribution and kinematics of late-type stars in the Galactic plane. It is found that neither SiO maser stars nor OH maser stars show any concentration to the spiral arms, which imply that they do not belong to the arm population and quite possibly they are low-mass stars in late stage of evolution. A rotational curve is also derived for these objects and a few features which may be real are discussed and compared with those derived from planetary nebulae and AGB stars.

  7. ITEL Experiment Module and its Flight on MASER9

    NASA Astrophysics Data System (ADS)

    Löth, K.; Schneider, H.; Larsson, B.; Jansson, O.; Houltz, Y.

    2002-01-01

    The ITEL (Interfacial Turbulence in Evaporating Liquid) module is built under contract from the European Space Agency (ESA) and is scheduled to fly onboard a Sounding Rocket (MASER 9) in March 2002. The project is conducted by Swedish Space Corporation (SSC) with Lambda-X as a subcontractor responsible for the optical system. The Principle Investigator is Pierre Colinet from Université Libre de Bruxelles (ULB). The experiment in ITEL on Maser 9 is part of a research program, which will make use of the International Space Station. The purpose of the flight on Maser 9 is to observe the cellular convection (Marangoni-Bénard instability) which arise when the surface tension varies with temperature yielding thermocapillary instabilities. During the 6 minutes of microgravity of the ITEL experiment, a highly volatile liquid layer (ethyl alcohol) will be evaporated, and the convection phenomena generated by the evaporation process will be visualized. Due to the cooling by latent heat consumption at the level of the evaporating free surface, a temperature gradient is induced perpendicularly to it. The flight experiment module contains one experiment cell, including a gas system for regulation of nitrogen flow over the evaporating surface and an injection unit that is used for injection of liquid into the cell both initially and during surface regulation. The experiment cell is equipped with pressure and flow sensors as well as thermocouples both inside the liquid and at different positions in the cell. Two optical diagnostic systems have been developed around the experiment cell. An interferometric optical tomograph measures the 3-dimensional distribution of temperature in the evaporating liquid and a Schlieren system visualizes the temperature gradients inside the liquid together with the liquid surface deformation. A PC/104 based electronic system is used for management and control of the experiment. The electronic system handles measurements, housekeeping, image

  8. Saturation of cyclotron maser instability driven by an electron loss-cone distribution

    NASA Technical Reports Server (NTRS)

    Kuo, S. P.; Lee, M. C.

    1986-01-01

    The resonance diffusion of electrons in velocity space caused by the excited EM wave fields is considered to be the dominant saturation process of cyclotron maser instability that is driven by an electron loss-cone distribution. An upper bound of the saturation level is derived analytically. Since the resulting saturation level is low, the resonance diffusion is indeed responsible for the saturation of the cyclotron maser instability.

  9. Measurement of the power spectral density of phase of the hydrogen maser

    NASA Technical Reports Server (NTRS)

    Sward, A.

    1972-01-01

    Hydrogen masers are being developed for the Deep Space Network as improved frequency standards, in order to achieve better timing accuracies, reduced Doppler residuals, and lower phase noise in the tracking system. Performance data for the masers are given in two forms: time domain performance, useful for analyzing time keeping systems and Doppler systems; and frequency domain performance, useful for analyzing tracking systems. Particular attention is given to frequency domain performance, as obtained from both time domain measurements and direct measurements.

  10. Advances in the development of piezoelectric quartz-crystal oscillators, hydrogen masers, and superconducting frequency standards

    NASA Technical Reports Server (NTRS)

    Suter, Joseph J.

    1988-01-01

    This paper describes recent research advances made in the development of radiation-hardened piezoelectric quartz oscillators, hydrogen masers, and superconducting oscillators, with emphasis placed on the principles involved in the operation of these oscillators and the factors affecting the operation. Particular attention is given to the radiation-susceptibility studies of quartz-crystal resonators, the hydrogen-maser relaxation process and noise sources, and low-phase-noise superconducting oscillators. Diagrams of these devices and performance graphs are included.

  11. Design and characterization of the DC acceleration and transport system required for the FOM 1 MW free electron maser experiment

    SciTech Connect

    Caplan, M.; Urbanus, W.H.; Geer, C. van der

    1995-12-31

    A Free Electron Maser (FEM) has been constructed and is soon to be tested at the FOM Institute (Rijnhuizen) Netherlands with the goal of producing 1 MW long pulse to CW microwave output in the range 130 GHz to 250 GHz. The design uses a DC beam system in a depressed collector configuration in order to make the overall wall plug efficiency 50%. The high voltage ({approximately} 2 MeV) power supply provides only the body interception current ({approximately} 30 mA) while the 12 amp beam current is supplied by the 100-200 keV collector supplies. Some of the design features to ensure low interception current, which is critical to long pulse (CW) operation are: (1) DC beam in-line transport and acceleration system, (2) emittance conserving solenoid focusing system, (3) halo suppression techniques at cathode edge, and (4) very low beam fill factor (<20%). A relativistic version of the Herman Optical theory developed for microwave tubes is used to determine current distribution functions everywhere along the beam from the electron gun, through the DC accelerator and transport system to the wiggler. This theory takes into account thermals far out on the gaussian tail which translates into beam current far outside the ideal beam edge. This theory is applied to the FOM beam line design to predict a series of beam envelope contours containing various percentages of total beam current up to 99.9%. Predictions of body interception current due to finite emittance (effective temperature) are presented and compared with measured experimental results.

  12. Weak maser emission of methyl formate toward Sagittarius B2(N) in the green bank telescope PRIMOS survey

    SciTech Connect

    Faure, A.; Wiesenfeld, L.; Szalewicz, K.

    2014-03-10

    A non-LTE radiative transfer treatment of cis-methyl formate (HCOOCH{sub 3}) rotational lines is presented for the first time using a set of theoretical collisional rate coefficients. These coefficients have been computed in the temperature range 5-30 K by combining coupled-channel scattering calculations with a high accuracy potential energy surface for HCOOCH{sub 3}-He. The results are compared to observations toward the Sagittarius B2(N) molecular cloud using the publicly available PRIMOS survey from the Green Bank Telescope. A total of 49 low-lying transitions of methyl formate, with upper levels below 25 K, are identified. These lines are found to probe a presumably cold (∼30 K), moderately dense (∼10{sup 4} cm{sup –3}), and extended region surrounding Sgr B2(N). The derived column density of ∼4 × 10{sup 14} cm{sup –2} is only a factor of ∼10 larger than the column density of the trans conformer in the same source. Provided that the two conformers have the same spatial distribution, this result suggests that strongly non-equilibrium processes must be involved in their synthesis. Finally, our calculations show that all detected emission lines with a frequency below 30 GHz are (collisionally pumped) weak masers amplifying the continuum of Sgr B2(N). This result demonstrates the importance and generality of non-LTE effects in the rotational spectra of complex organic molecules at centimeter wavelengths.

  13. Free-electron masers vs. gyrotrons: prospects for high-power sources at millimeter and submillimeter wavelengths

    NASA Astrophysics Data System (ADS)

    Thumm, Manfred

    2002-05-01

    The possible applications of high-power millimeter (mm) and sub-mm waves from free-electron masers (FEMs) and gyro-devices span a wide range of technologies. The plasma physics community has already taken advantage of recent advances in applying high-power mm waves generated by long pulse or continuous wave (CW) gyrotron oscillators and short pulse very high-power FEMs in the areas of RF-plasma production, heating, non-inductive current drive, plasma stabilization and active plasma diagnostics for magnetic confinement thermonuclear fusion research, such as electron cyclotron resonance heating (28-170 GHz), electron cyclotron current drive , collective Thomson scattering , microwave transmission and heat-wave propagation experiments. Continuously frequency tunable FEMs could widen these fields of applications. Another important application of CW gyrotrons is industrial materials processing, e.g. sintering of high-performance functional and structural nanostructured ceramics. Sub-mm wave sources are employed in high-frequency broadband electron paramagnetic resonance and other types of spectroscopy. Future applications which await the development of novel high-power FEM amplifiers and gyro-amplifiers include high-resolution radar ranging and imaging in atmospheric and planetary science as well as deep-space and specialized satellite communications and RF drivers for next-generation high-gradient linear accelerators (supercolliders). The present paper reviews the state-of-the-art and future prospects of these recent applications of gyro-devices and FEMs and compares their specific advantages.

  14. Peculiarities of the Mode Spectrum in Free-Electron Masers Based on Oversized Bragg Resonators with a Corrugation Phase Step

    NASA Astrophysics Data System (ADS)

    Peskov, N. Yu.; Kaminsky, A. K.; Kuzikov, S. V.; Perel'shtein, E. A.; Sedykh, S. N.; Sergeev, A. S.

    2016-03-01

    We study the operating mode splitting caused by interaction of the neighboring Bragg scattering zones in an oversized Bragg resonator with a corrugation phase step, which is operated at the coupled forward and backward waveguide modes with different transverse structures. This effect is described within the framework of the coupled-wave approach using an advanced four-wave model. It is shown that this effect deteriorates the selective properties of the resonator and, finally, restricts the output power and reduces stability of the narrow-band operating regime in the free-electron masers (FEMs) based on such resonators. The results of the theoretical analysis were corroborated by 3D simulations and "cold" electrodynamic tests. Experimental studies of 30-GHz FEMs with the Bragg resonators having different corrugation depths demonstrated the onset of both narrow-band single-mode and multifrequency multimode oscillation regimes in such resonators. The possibility of power enhancement by using passive compression of the FEM output pulse in a double-frequency oscillation regime is discussed.

  15. Radiation beam steering by cyclotron-resonance maser array

    NASA Astrophysics Data System (ADS)

    Kesar, Amit; Jerby, Eli

    1999-02-01

    A concept of power beaming by a cyclotron-resonance maser (CRM) array is presented theoretically. In this scheme, the CRM-array operates as an active phased-array antenna, and radiates directly from its output aperture. The gain and phase of each CRM element in the array are controlled by the voltage and current of its electron gun. The consequent phase difference between the CRM-element outputs enables the steering of the radiation beam in the far field. A simplified linear model is presented for a CRM-array antenna with uncoupled elements. It provides radiation patterns which demonstrate the main feature of power-beam steering. A wide angular steering range (+/-35°) is obtained by an analog electronic control of the CRM array. The feasibility of practical CRM-array antennas is discussed.

  16. Normal and anomalous Doppler effects in periodic waveguide cyclotron maser

    SciTech Connect

    Korol, M.; Jerby, E.

    1995-12-31

    A linear analysis of the periodic-waveguide cyclotron (PWC) maser shows that the PWC interaction with fast-waves possesses properties of the known anomalous Doppler resonance interaction if the wave impedance of the resonant spatial harmonic, Z{sub n}, is much smaller than the free space impedance, i.e. if Z{sub n} {much_lt} Z{sub 0}. The feasibility of a fast-wave PWC interaction in a low impedance waveguide is examined theoretically in this paper. A practical scheme of a slotted-waveguide PWC operating in the fundamental harmonic near cutoff is proposed for a future experiment. The possible advantages of the quasi-anomalous Doppler effect in the fast-wave-PWC operating regime are the alleviation of the initial electron rotation and a high-efficiency operation.

  17. Simulations of dielectric Cerenkov masers at moderate to high power

    SciTech Connect

    Mardahl, P.; Verboncoeur, J.P.; Birdsall, C.K.

    1996-12-31

    A dielectric Cerenkov maser amplifier is simulated with XOOPIC and results are compared to experiment and theory. The device examined is azimuthally symmetric with a circular crossection. The dispersion has been obtained and agrees well with the experiment. The efficiency, power and gain will be compared for the parameters of the Dartmouth experiment. Other configurations of interest include devices of higher beam energy and current such as the experiment of Main. This device generated a peak microwave power of 280 MW for 3ns before experiencing RF quenching, possibly due to the formation of a plasma at the wall, which they intend to investigate further. The authors also examine various techniques of reducing the field stresses which may cause breakdown in this class of device. Also, increasing microwave power and efficiency via grading the dielectric constant to match the beam velocity will be examined.

  18. Discovery of pulsed OH maser emission stimulated by a pulsar.

    PubMed

    Weisberg, Joel M; Johnston, Simon; Koribalski, Bärbel; Stanimirovic, Snezana

    2005-07-01

    Stimulated emission of radiation has not been directly observed in astrophysical situations up to this time. Here we demonstrate that photons from pulsar B1641-45 stimulate pulses of excess 1720-megahertz line emission in an interstellar hydroxyl (OH) cloud. As this stimulated emission is driven by the pulsar, it varies on a few-millisecond time scale, which is orders of magnitude shorter than the quickest OH maser variations previously detected. Our 1612-megahertz spectra are inverted copies of the 1720-megahertz spectra. This "conjugate line" phenomenon enables us to constrain the properties of the interstellar OH line-producing gas. We also show that pulsar signals undergo significantly deeper OH absorption than do other background sources, which confirms earlier tentative findings that OH clouds are clumpier on small scales than are neutral hydrogen clouds.

  19. Mass loss and OH maser emission from Mira variables

    NASA Technical Reports Server (NTRS)

    Michalitsianos, A. G.; Kafatos, M.

    1978-01-01

    The mass, radius, and luminosity of 26 Mira variables that are known OH sources of radio emission at 1612 MHz have been estimated. The time-independent solution of Salpeter's (1974) stellar-wind equation and a period-density relation are used to solve for basic stellar parameters, with the aid of the terminal expansion velocity of the OH maser cloud. Masses obtained from these calculations are consistent with other estimated values for masses of Mira variables. Good agreement is obtained when comparing the rate of mass loss as determined from Reimers's (1977) semiempirical relation with estimates of the mass-loss rate as deduced from theoretical models involving radiation pressure on grains. These calculations suggest a strong correlation between the mass-loss rate and the pulsation period. Arguments concerning the general properties of silicate grains from radiation-pressure-driven stellar-wind equations are discussed.

  20. [Probing Planck-scale Physics with a Ne-21/He-3 Zeeman Maser

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Ne-21/He-3 Zeeman maser is a recently developed device which employs co-located ensembles of Ne-21 and He-3 atoms to provide sensitive differential measurements of the noble gas nuclear Zeeman splittings as a function of time, thereby greatly attenuating common-mode systematic effects such as uniform magnetic field variations. The Ne-21 maser will serve as a precision magnetometer to stabilize the system's static magnetic field, while the He-3 maser is used as a sensitive probe for violations of CPT and Lorentz symmetry by searching for small variations in the 3He maser frequency as the spatial orientation of the apparatus changes due to the rotation of the Earth (or placement on a rotating table). In the context of a general extension of the Standard Model of particle physics, the Ne-21/He-3 maser will provide the most sensitive search to date for CPT and Lorentz violation of the neutron: better than 10(exp -32) GeV, an improvement of more than an order of magnitude over past experiments. This exceptional precision will offer a rare opportunity to probe physics at the Planck scale. A future space-based Ne-21/He-3 maser or related device could provide even greater sensitivity to violations of CPT and Lorentz symmetry, and hence to Planck-scale physics, because of isolation from dominant systematic effects associated with ground-based operation, and because of access to different positions in space-time.

  1. Emergence of a Narrow H2O Maser Feature in NGC 1052

    NASA Astrophysics Data System (ADS)

    Kameno, Seiji; Nakai, Naomasa; Sawada-Satoh, Satoko; Sato, Naoko; Haba, Arisa

    2005-02-01

    We report the emergence of a narrow H2O maser feature with an FWHM of 21 km s-1 in the LINER NGC 1052, which has been known to show only a broad (FWHM>100 km s-1) maser line profile with relatively bright continuum radio emission. The new narrow maser feature with a peak flux density of 47 mJy at VLSR=1787 km s-1 is redshifted by 328 km s-1 with respect to the systemic velocity. Broad features with peak velocities of 1510 and 1704 km s-1, more redward than ever observed before, are also detected. The profile of the new narrow feature possibly shows brightening by 16%+/-9% and narrowing by 30%+/-12% between 2003 May 30 and June 2. During the same time, the continuum flux density has increased by 21%. Synchronous variation of maser and continuum flux densities on a timescale of days resembles that in Mrk 348, which is also a broad megamaser source with a bright radio continuum. Continuum and maser brightening and narrowing indicate that an increase of the background seed photon and an increase of maser gain have occurred simultaneously. A jet component running behind a mixture of ionized regions and X-ray dissociation regions at a subrelativistic velocity can produce such short-time variation. Another explanation is an interaction between the jet and molecular clouds.

  2. Stimulated Raman scattering as an explanation for the extreme high-velocity features of water maser emission

    NASA Astrophysics Data System (ADS)

    Deguchi, Shuji

    1994-01-01

    Extreme high-velocity features in the water maser spectra with velocity shifts of about +/- 900 km/s have recently been detected in the extragalactic water maser source, NGC 4258. We explain these extreme high-velocity features of water masers by stimulated Raman scattering in the plasma of the electron density of about 106-107/cu cm. For the Raman masers to occur, the brightness temperature of the original masers must be greater than about 1016-1019 K (depending on the maser beam solid angles, etc.), and the amplification path length of the maser must be about 3 x 1014 cm. We show that the frequency-downshifted (Stokes) photons are produced by the backward scattering and that upshifted (anti-Stokes) photons are created by interacting intersecting masers in the plasma. The intensity of the upshifted component is slightly lower than the intensity of the downshifted component. Time variations of upshifted and downshifted features must be independent. A crucial test for the Raman maser model is proposed.

  3. Methanol simplifies gas processing

    SciTech Connect

    Minkkinen, A.; Jonchere, J.P.

    1997-12-31

    Recent development of a simple single solvent technology goes far to meet the complete gas processing needs. The use of methanol, as practiced in the IPFEXOL process, where it is used not only as a hydrate inhibitor and antifreeze agent but as an acid gas extraction solvent makes the complete gas processing scheme simple and probably the most cost effective as well. This paper presents several gas processing applications where water, hydrocarbon liquids and acid gases are removed from natural wellhead production gases. Water and hydrocarbon liquids removal is achieved to the extent necessary to make a pipeline transportable gas or meet downstream cryogenic processing demands. These are illustrated with recent applications of the IFPEX-1 process successfully operating today in North America and the Far East. A recent North Sea offshore project is highlighted showing the particular advantages in offshore applications. For the removal of water and hydrocarbon liquids together with a substantial quantity of not only CO{sub 2} but H{sub 2}S, the most complete methanol use scheme is presented. This is illustrated with the development of an advanced version of the IFPEX-2 process containing some innovative but simple equipment concepts which yields high pressure dry acid gases for reinjection or a high quality acid gas destined to Claus type sulfur recovery.

  4. Atomic hydrogen for low temperature atomic hydrogen masers and in-vacuum dissociators for VLG-11 series masers

    NASA Technical Reports Server (NTRS)

    Vessot, R. F. C.

    1984-01-01

    The operation of a cryogenically-cooled hydrogen maser using an RF plasma dissociator operating at liquid nitrogen temperature (77K) in confunction with a state selector magnet whose dimensions are suitable for slow atoms is studied. The focusing characteristics for a hexapole state selector magnet with maximum fields at the pole tips, provide a maximum acceptance angle for atoms at the most probable velocity in the beam. By thermally isolating the RF circuitry from the dissociator glassware, only dielectric losses in the glass and the energy coupled to the plasma will result in the boil-off of liquid nitrogen. It is estimated that this is about one watt and thus a loss rate of approximately .022 liters pr hour is anticipated.

  5. 338-GHz Semiconductor Amplifier Module

    NASA Technical Reports Server (NTRS)

    Samoska, Lorene A.; Gaier, Todd C.; Soria, Mary M.; Fung, King Man; Rasisic, Vesna; Deal, William; Leong, Kevin; Mei, Xiao Bing; Yoshida, Wayne; Liu, Po-Hsin; Uyeda, Jansen; Lai, Richard

    2010-01-01

    Research findings were reported from an investigation of new gallium nitride (GaN) monolithic millimeter-wave integrated circuit (MMIC) power amplifiers (PAs) targeting the highest output power and the highest efficiency for class-A operation in W-band (75-110 GHz). W-band PAs are a major component of many frequency multiplied submillimeter-wave LO signal sources. For spectrometer arrays, substantial W-band power is required due to the passive lossy frequency multipliers.

  6. Sixty GHz IMPATT diode development

    NASA Technical Reports Server (NTRS)

    Ma, Y. E.; Chen, J.; Benko, E.; Barger, M. J.; Nghiem, H.; Trinh, T. Q.; Kung, J.

    1985-01-01

    The objective of this program is to develop 60 GHz GaAs IMPATT Diodes suitable for communications applications. The performance goal of the 60 GHz IMPATT is 1W CW output power with a conversion efficiency of 15 percent and 10 year life time. During the course of the program, double drift (DD) GaAs IMPATT Diodes have been developed resulting in the state of the art performance at V band frequencies. A CW output power of 1.12 W was demonstrated at 51.9 GHz with 9.7 percent efficiency. The best conversion efficiency achieved was 15.3 percent. V band DD GaAs IMPATTs were developed using both small signal and large signal analyses. GaAs wafers of DD flat, DD hybrid, and DD Read profiles using molecular beam epitaxy (MBE) were developed with excellent doping profile control. Wafer evaluation was routinely made by the capacitance versus voltage (C-V) measurement. Ion mass spectrometry (SIMS) analysis was also used for more detailed profile evaluation.

  7. Magnetic fields around evolved stars: further observations of H2O maser polarization

    NASA Astrophysics Data System (ADS)

    Leal-Ferreira, M. L.; Vlemmings, W. H. T.; Kemball, A.; Amiri, N.

    2013-06-01

    Context. A low- or intermediate-mass star is believed to maintain a spherical shape throughout the evolution from the main sequence to the asymptotic giant branch (AGB) phase. However, many post-AGB objects and planetary nebulae exhibit non-spherical symmetry. Several candidates have been suggested as factors that can play a role in this change of morphology, but the problem is still not well understood. Magnetic fields are one of these possible agents. Aims: We aim to detect the magnetic field and infer its properties around four AGB stars using H2O maser observations. The sample we observed consists of the following sources: the semi-regular variable RT Vir, and the Mira variables AP Lyn, IK Tau, and IRC+60370. Methods: We observed the 61,6 -52,3 H2O maser rotational transition in full-polarization mode to determine its linear and circular polarization. Based on the Zeeman effect, one can infer the properties of the magnetic field from the maser polarization analysis. Results: We detected a total of 238 maser features in three of the four observed sources. No masers were found toward AP Lyn. The observed masers are all located between 2.4 and 53.0 AU from the stars. Linear and circular polarization was found in 18 and 11 maser features, respectively. Conclusions: We more than doubled the number of AGB stars in which a magnetic field has been detected from H2O maser polarization. Our results confirm the presence of fields around IK Tau, RT Vir, and IRC+60370. The strength of the field along the line of sight is found to be between 47 and 331 mG in the H2O maser region. Extrapolating this result to the surface of the stars, assuming a toroidal field (∝ r-1), we find magnetic fields of 0.3-6.9 G on the stellar surfaces. If, instead of a toroidal field, we assume a poloidal field (∝ r-2), then the extrapolated magnetic field strength on the stellar surfaces are in the range between 2.2 and ~115 G. Finally, if a dipole field (∝ r-3) is assumed, the field

  8. Z45: A new 45-GHz band dual-polarization HEMT receiver for the NRO 45-m radio telescope

    NASA Astrophysics Data System (ADS)

    Nakamura, Fumitaka; Ogawa, Hideo; Yonekura, Yoshinori; Kimura, Kimihiko; Okada, Nozomi; Kozu, Minato; Hasegawa, Yutaka; Tokuda, Kazuki; Ochiai, Tetsu; Mizuno, Izumi; Dobashi, Kazuhito; Shimoikura, Tomomi; Kameno, Seiji; Taniguchi, Kotomi; Shinnaga, Hiroko; Takano, Shuro; Kawabe, Ryohei; Nakajima, Taku; Iono, Daisuke; Kuno, Nario; Onishi, Toshikazu; Momose, Munetake; Yamamoto, Satoshi

    2015-12-01

    We developed a dual-linear-polarization HEMT (High Electron Mobility Transistor) amplifier receiver system of the 45-GHz band (hereafter Z45), and installed it in the Nobeyama 45-m radio telescope. The receiver system is designed to conduct polarization observations by taking the cross-correlation of two linearly polarized components, from which we process full Stokes spectroscopy. We aim to measure the magnetic field strength through the Zeeman effect of the emission line of CCS (JN = 43-32) toward pre-protostellar cores. A linear-polarization receiver system has a smaller contribution of instrumental polarization components to the Stokes V spectra than that of the circular polarization system, so that it is easier to obtain the Stokes V spectra. The receiver has an RF frequency of 42-46 GHz and an intermediate frequency (IF) band of 4-8 GHz. The typical noise temperature is about 50 K, and the system noise temperature ranges from 100 to 150 K over the frequency of 42-46 GHz. The receiver system is connected to two spectrometers, SAM45 and PolariS. SAM45 is a highly flexible FX-type digital spectrometer with a finest frequency resolution of 3.81 kHz. PolariS is a newly developed digital spectrometer with a finest frequency resolution of 60 Hz, and which has a capability to process the full-Stokes spectroscopy. The half-power beam width (HPBW) was measured to be 37″ at 43 GHz. The main beam efficiency of the Gaussian main beam was derived to be 0.72 at 43 GHz. The SiO maser observations show that the beam pattern is reasonably round at about 10% of the peak intensity and the side-lobe level was less than 3% of the peak intensity. Finally, we present some examples of astronomical observations using Z45.

  9. SiO Masers around WX Psc Mapped with the KVN and VERA Array (KaVA)

    NASA Astrophysics Data System (ADS)

    Yun, Youngjoo; Cho, Se-Hyung; Imai, Hiroshi; Kim, Jaeheon; Asaki, Yoshiharu; Chibueze, James O.; Choi, Yoon Kyung; Dodson, Richard; Kim, Dong-Jin; Kusuno, Kozue; Matsumoto, Naoko; Min, Cheulhong; Oyadomari, Miyako; Rioja, María J.; Yoon, Dong-Hwan; Byun, Do-Young; Chung, Hyunsoo; Chung, Moon-Hee; Hagiwara, Yoshiaki; Han, Myoung-Hee; Han, Seog-Tae; Hirota, Tomoya; Honma, Mareki; Hwang, Jung-Wook; Je, Do-Heung; Jike, Takaaki; Jung, Dong-Kyu; Jung, Taehyun; Kang, Ji-Hyun; Kang, Jiman; Kang, Yong-Woo; Kan-ya, Yukitoshi; Kanaguchi, Masahiro; Kawaguchi, Noriyuki; Kim, Bong Gyu; Ryoung Kim, Hyo; Kim, Hyun-Goo; Kim, Jongsoo; Kim, Kee-Tae; Kim, Mikyoung; Kobayashi, Hideyuki; Kono, Yusuke; Kurayama, Tomoharu; Lee, Changhoon; Lee, Jeewon; Lee, Jeong Ae; Lee, Jung-Won; Lee, Sang Hyun; Lee, Sang-Sung; Lyo, A.-Ran; Minh, Young Chol; Oh, Chungsik; Oh, Se-Jin; Oyama, Tomoaki; Roh, Duk-Gyoo; Sawada-Satoh, Satoko; Shibata, Katsunori M.; Sohn, Bong Won; Song, Min-Gyu; Tamura, Yoshiaki; Wi, Seog-Oh; Yeom, Jae-Hwan

    2016-05-01

    We present the first images of the v = 1 and v = 2 J = 1 → 0 SiO maser lines taken with KaVA, i.e., the combined array of the Korean Very Long Baseline Interferometry (VLBI) Network and the VLBI Exploration of Radio Astrometry (VERA), toward the OH/IR star WX Psc. The combination of long and short antenna baselines enabled us to detect a large number of maser spots, which exhibit a typical ring-like structure in both the v = 1 and v = 2 J = 1 → 0 SiO masers as those that have been found in previous VLBI observational results of WX Psc. The relative alignment of the v = 1 and v = 2 SiO maser spots are precisely derived from astrometric analysis, due to the absolute coordinates of the reference maser spot that were well determined in an independent astrometric observation with VERA. The superposition of the v = 1 and v = 2 maser spot maps shows a good spatial correlation between the v = 1 and v = 2 SiO maser features. Nevertheless, it is also shown that the v = 2 SiO maser spot is distributed in an inner region compared to the v = 1 SiO maser by about 0.5 mas on average. These results provide good support for the recent theoretical studies of the SiO maser pumping, in which both the collisional and the radiative pumping predict the strong spatial correlation and the small spatial discrepancy between the v = 1 and v = 2 SiO maser.

  10. OTEC energy via methanol production

    SciTech Connect

    Avery, W.H.; Richards, D.; Niemeyer, W.G.; Shoemaker, J.D.

    1983-01-01

    The conceptual design of an 160 MW/sub e/ OTEC plantship has been documented; it is designed to produce 1000 tonne/day of fuel-grade methanol from coal slurry shipped to the plantship, using oxygen and hydrogen from the on-board electrolysis of water. Data and components are used that were derived by Brown and Root Development, Inc. (BARDI) in designing a barge-mounted plant to make methanol from natural gas for Litton Industries and in the design and construction of a coal-to-ammonia demonstration plant in operation at Muscle Shoals, Alabama, for the Tennessee Valley Authority (TVA). The OTEC-methanol plant design is based on the use of the Texaco gasifier and Lurgi synthesis units. The sale price of OTEC methanol delivered to port from this first-of-a-kind plant is estimated to be marginally competitive with methanol from other sources at current market prices.

  11. Bragg Resonator Cyclotron Resonance Maser Experiments Driven by a Microsecond, Intense Electron Beam Accelerator

    NASA Astrophysics Data System (ADS)

    Choi, Jin Joo

    The cyclotron resonance maser (CRM) has proven to be attractive for many high power microwave applications such as fusion plasma heating, radar/communications, and high gradient RF accelerators. Most of the previous CRM experiments with MV electron beams have been conducted with short (<0.1 musec) pulses. The present work contains the first comprehensive experimental study on mode competition in a high-Q Bragg resonator CRM employing a microsecond, relativistic electron beam. We have designed and fabricated a high-Q sinusoidal Bragg resonator designed to excite high frequency CARM oscillation of the TE_{31} cylindrical cavity mode at 18.9 GHz. The measured reflectivity of the TE_{31} mode is consistent with the prediction of uncoupled single mode theory. A high quality annular electron beam with low velocity spread and energy spread is produced through an apertured mask-anode. The apertured electron beam has been characterized by the use of glass plate diagnostics. The measured beam velocity ratio, v_{| }/v_{|}, was shown to be in agreement with computer simulation results and the theoretical predictions. Experiments have been performed for 4 cases: (1) Bragg resonator with ripples half-inward, (2) large diameter smooth tube without Bragg resonator, (3) Bragg resonator with ripples fully-outward, and (4) small diameter smooth tube without Bragg resonator. The Bragg resonator with ripples half-inward generated high power microwave radiation from TE_ {11} gyro-BWO interactions, TE _{21} absolute instability, and high harmonic gyrotron modes. Considerably less power from the TE_{11} gyro -BWO was observed for the Bragg resonator with ripples fully -outward. The microwave emission from the TE_ {21} absolute instability in the Bragg resonator with ripples fully-outward was successfully suppressed by lowering the cavity magnetic field. These three undesired oscillations, (TE _{21} absolute instability, TE _{11} gyro-BWO, TE _{51} second and third harmonic), were the most

  12. 183 GHz water line variation: An energetic outburst in orion KL

    NASA Technical Reports Server (NTRS)

    Kuiper, T. B. H.; Kuiper, E. N. R.; Swanson, P. N.; Dickinson, D. F.; Klein, M. J.; Zimmermann, P.

    1984-01-01

    Observations of the 3(13)-2(20) transition of water vapor in the direction of Ori MC1 in 1980 February show a 50% flux increase and an apparent additional red shift of approximately 2 km/s relative to the line observed in 1977 December. From a detailed examination of the amplitude and frequency calibration, it appears unlikely that the effect is due to systematic error. The increase is attributed to the appearance of a new component at a velocity of 12 km/s with respect to the local standard of rest. The new component also has broad wings. Increased emission from a region in the high-velocity core of Ori MC1 can be due either to additional far-IR radiation to pump the 1983 GHz transition or to a change in the physical conditions in the gas. Statistical equilibrium calculations using the large-velocity-gradient formalism were carried out to develop a model for the emission. The calculations support a model in which the gas in the region of enhanced emission is hotter than the dust. The temporal coincidence between the 183 GHZ increase and the 22 GH1 water maser outburst suggests a common, impulsive cause, which has heated the gas in a part of the HV source, enhancing the emission in both transitions.

  13. California methanol assessment. Volume 1: Summary report

    NASA Technical Reports Server (NTRS)

    Otoole, R.; Dutzi, E.; Gershman, R.; Heft, R.; Kalema, W.; Maynard, D.

    1983-01-01

    The near term methanol industry, the competitive environment, long term methanol market, the transition period, air quality impacts of methanol, roles of the public and private sectors are considered.

  14. Photoinjector-driven chirped-pulse free-electron maser

    NASA Astrophysics Data System (ADS)

    Hartemann, Frederic V.; Le Sage, Gregory P.; Fochs, Scott N.; Feng, Helena X.; Laurent, L. L.; Rosenau, S. A.; Luhmann, Neville C., Jr.

    1995-09-01

    A compact, high repetition rate (2.142 GHz in burst mode), relativistic (5 MeV) photoinjector facility is currently under construction at the UC Davis Department of Applied Science, on the LLNL site. Photoelectron bunches are produced by irradiating a high quantum efficiency Cs2Te photocathode with a train of 100 UV (210 nm), ultrashort (250 fs) laser pulses. These bunches are accelerated in a 1-1/2 cell, (pi) -mode, X-band rf structure energized by a 20 MW, 8.568 GHz SLAC klystron. The peak current is 0.25 kA (0.25 nC, 1 ps bunches), with a normalized emittance (epsilon) < 2.5 (pi) mm-mrad. This prebunched electron beam is then transversally accelerated in a cylindrical waveguide by a 30-mm period, 10 period long helical wiggler. The peak wiggler field is adjusted to 8.5 kG, so that the group velocity of the radiated electromagnetic waves matches the axial velocity of the electron bunch (grazing condition). Chirped pulses in excess of 2 MW power are produced with an instantaneous bandwidth extending from 125 GHz to 225 GHz, and pulse duration of 15 ps.

  15. Monolithic 20-GHz Transmitting Module

    NASA Technical Reports Server (NTRS)

    Kascak, T.; Kaelin, G.; Gupta, A.

    1986-01-01

    20-GHz monolithic microwave/millimeter-wave integrated circuit (MMIC) with amplification and phase-shift (time-delay) capabilities developed. Use of MMIC module technology promises to make feasible development of weight- and cost-effective phased-array antenna systems, identified as major factor in achieving minimum cost and efficient use of frequency and orbital resources of future generations of communication satellite systems. Use of MMIC transmitting modules provides for relatively simple method for phase-shift control of many separate radio-frequency (RF) signals required for phased-array antenna systems.

  16. OH and H2O maser variations in W33B

    NASA Astrophysics Data System (ADS)

    Colom, P.; Lekht, E. E.; Pashchenko, M. I.; Rudnitskij, G. M.

    2015-03-01

    Context. The active star-forming region W33B is a source of OH and H2O maser emission located in distinct zones around the central object. Aims: The aim was to obtain the complete Stokes pattern of polarised OH maser emission and to trace its variability and to investigate flares and long-term variability of the H2O maser and evolution of individual emission features. Methods: Observations in the OH lines at a wavelength of 18 cm were carried out on the Nançay radio telescope (France) at a number of epochs in 2008-2014; H2O line observations (long-term monitoring) at λ = 1.35 cm were performed on the 22 m radio telescope of the Pushchino Radio Astronomy Observatory (Russia) between 1981 and 2014. Results: We have observed strong variability of the emission features in the main 1665- and 1667 MHz OH lines as well as in the 1612 MHz satellite line. Zeeman splitting has been detected in the 1665 MHz OH line at 62 km s-1 and in the 1667 MHz line at 62 and 64 km s-1. The magnetic field intensity was estimated to be from 2 to 3 mG. The H2O emission features form filaments, chains with radial-velocity gradients, or more complicated structures including large-scale ones. Conclusions: Long-term observations of the hydroxyl maser in the W33B region have revealed narrowband polarised emission in the 1612 MHz line with a double-peak profile characteristic of type IIb circumstellar masers. The 30 year monitoring of the water-vapour maser in W33B showed several strong flares of the H2O line. The observed radial-velocity drift of the H2O emission features suggests propagation of an excitation wave in the masering medium with a gradient of radial velocities. In OH and H2O masers some turbulent motions of material are inferred. The spectra of Fig. 7 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A49 or at http://comet.sai.msu.ru/~gmr/Maser_monitoring/W33B

  17. Solar and stellar radio spikes - Limits on the saturation of the electron-cyclotron maser

    NASA Technical Reports Server (NTRS)

    Wentzel, Donat G.; Aschwanden, Markus J.

    1991-01-01

    The solar millisecond radio 'spikes' have been explained in terms of X-mode radiation generated by a maser near the electron gyrofrequency, acting on fast coronal electrons with a loss cone. This maser is a phenomenon described by quasi-linear theory. It is sensitive to the small first-relativistic correction to the gyrofrequency. Thus, it might be disrupted rather easily by nonlinear effects. The maximum radiation density that can be reached before the radiation entrains (phase-locks) the electrons and saturates the maser is discussed. If the observed durations of solar radio spikes are a measure of the rate of scattering into the loss-cone, then the inferred energy density is at least two orders of magnitude less than the energy density at which entrainment sets in. Also, maser emission from auroral kilometric radiation does not reach wave energies critical for electron entrainment. Maser emissions from flare stars, however, show 3-4 orders of magnitude higher radio fluxes and brightness temperatures than for the solar case and are likely to be saturated by entrainment.

  18. The electron-cyclotron maser instability as a source of plasma radiation. [Solar radio bursts

    NASA Technical Reports Server (NTRS)

    Winglee, R. M.; Dulk, G. A.

    1986-01-01

    The generation of continuum bursts from the sun at dm and m wavelengths (in particular, type IV bursts) via the electron-cyclotron-maser instability is examined. The maser instability can be driven by an electron distribution with either a loss-cone anisotropy or a peak at large pitch angles. For omega(p)/Omega(e) much greater than 1, the maser emission is produced by electrons interacting through a harmonic (cyclotron) resonance and is electrostatic, being in the upper hybrid mode at frequencies approximately equal to omega(p). Coalescence processes are required to convert the electrostatic waves into transverse radiation which can escape from the source region. Whether the resultant spectrum is nearly a smooth continuum or has a zebra-stripe pattern (both of which occur in type IV bursts) depends on the form of the electron distribution, inhomogeneities in the density and magnetic field, and whether the maser reaches saturation. For at least the case of some type IV dm bursts with fine structure, comparison with observations seems to indicate that the electrons producing the emission are more likely to have a loss-cone distribution, and that the maser instability is not at saturation.

  19. Probing the circumstellar environments of very young low-mass stars using water masers

    NASA Technical Reports Server (NTRS)

    Terebey, S.; Vogel, S. N.; Myers, P. C.

    1992-01-01

    The VLA is used to search nearby very young low-mass stars for water maser emission. The sample consists of 26 low-luminosity IRAS sources embedded in dense molecular cores, a class of sources suspected to be newly forming low-mass stars on the order of a few hundred thousand years old. Three sources were detected. High spatial resolution maps show the region of maser emission is generally confined to an area smaller than about 0.5 arcsec near the star, and the velocities of individual components span intervals ranging from 20 to 40 km/s. It is inferred from the fact that the maser velocities are too large to be due to gravitational motions in at least two of the sources that the masers are associated with the winds from the young low-mass stars. A comparison of the high spatial resolution maser data to lower-resolution CO data shows no evidence for higher collimation close to the star; the stellar wind cavity appears to have similar collimation at 10 exp 15 cm as at 10 exp 7 to 10 exp 18 cm.

  20. DISTANCES TO DARK CLOUDS: COMPARING EXTINCTION DISTANCES TO MASER PARALLAX DISTANCES

    SciTech Connect

    Foster, Jonathan B.; Jackson, James M.; Stead, Joseph J.; Hoare, Melvin G.; Benjamin, Robert A. E-mail: jackson@bu.edu E-mail: mgh@ast.leeds.ac.uk

    2012-06-01

    We test two different methods of using near-infrared extinction to estimate distances to dark clouds in the first quadrant of the Galaxy using large near-infrared (Two Micron All Sky Survey and UKIRT Infrared Deep Sky Survey) surveys. Very long baseline interferometry parallax measurements of masers around massive young stars provide the most direct and bias-free measurement of the distance to these dark clouds. We compare the extinction distance estimates to these maser parallax distances. We also compare these distances to kinematic distances, including recent re-calibrations of the Galactic rotation curve. The extinction distance methods agree with the maser parallax distances (within the errors) between 66% and 100% of the time (depending on method and input survey) and between 85% and 100% of the time outside of the crowded Galactic center. Although the sample size is small, extinction distance methods reproduce maser parallax distances better than kinematic distances; furthermore, extinction distance methods do not suffer from the kinematic distance ambiguity. This validation gives us confidence that these extinction methods may be extended to additional dark clouds where maser parallaxes are not available.

  1. 47 CFR 25.136 - Licensing provisions for user transceivers in the 1.6/2.4 GHz, 1.5/1.6 GHz, and 2 GHz Mobile...

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... the 1.6/2.4 GHz, 1.5/1.6 GHz, and 2 GHz Mobile Satellite Services. 25.136 Section 25.136 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS..., 1.5/1.6 GHz, and 2 GHz Mobile Satellite Services. In addition to the technical...

  2. 47 CFR 25.136 - Licensing provisions for user transceivers in the 1.6/2.4 GHz, 1.5/1.6 GHz, and 2 GHz Mobile...

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... the 1.6/2.4 GHz, 1.5/1.6 GHz, and 2 GHz Mobile Satellite Services. 25.136 Section 25.136 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS..., 1.5/1.6 GHz, and 2 GHz Mobile Satellite Services. In addition to the technical...

  3. 47 CFR 25.136 - Licensing provisions for user transceivers in the 1.6/2.4 GHz, 1.5/1.6 GHz, and 2 GHz Mobile...

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... the 1.6/2.4 GHz, 1.5/1.6 GHz, and 2 GHz Mobile Satellite Services. 25.136 Section 25.136 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS..., 1.5/1.6 GHz, and 2 GHz Mobile Satellite Services. In addition to the technical...

  4. A 17 GHz molecular rectifier

    NASA Astrophysics Data System (ADS)

    Trasobares, J.; Vuillaume, D.; Théron, D.; Clément, N.

    2016-10-01

    Molecular electronics originally proposed that small molecules sandwiched between electrodes would accomplish electronic functions and enable ultimate scaling to be reached. However, so far, functional molecular devices have only been demonstrated at low frequency. Here, we demonstrate molecular diodes operating up to 17.8 GHz. Direct current and radio frequency (RF) properties were simultaneously measured on a large array of molecular junctions composed of gold nanocrystal electrodes, ferrocenyl undecanethiol molecules and the tip of an interferometric scanning microwave microscope. The present nanometre-scale molecular diodes offer a current density increase by several orders of magnitude compared with that of micrometre-scale molecular diodes, allowing RF operation. The measured S11 parameters show a diode rectification ratio of 12 dB which is linked to the rectification behaviour of the direct current conductance. From the RF measurements, we extrapolate a cut-off frequency of 520 GHz. A comparison with the silicon RF-Schottky diodes, architecture suggests that the RF-molecular diodes are extremely attractive for scaling and high-frequency operation.

  5. Electron Cyclotron Maser Emissions from Evolving Fast Electron Beams

    NASA Astrophysics Data System (ADS)

    Tang, J. F.; Wu, D. J.; Chen, L.; Zhao, G. Q.; Tan, C. M.

    2016-05-01

    Fast electron beams (FEBs) are common products of solar active phenomena. Solar radio bursts are an important diagnostic tool for understanding FEBs and the solar plasma environment in which they propagate along solar magnetic fields. In particular, the evolution of the energy spectrum and velocity distribution of FEBs due to the interaction with the ambient plasma and field during propagation can significantly influence the efficiency and properties of their emissions. In this paper, we discuss the possible evolution of the energy spectrum and velocity distribution of FEBs due to energy loss processes and the pitch-angle effect caused by magnetic field inhomogeneity, and we analyze the effects of the evolution on electron-cyclotron maser (ECM) emission, which is one of the most important mechanisms for producing solar radio bursts by FEBs. Our results show that the growth rates all decrease with the energy loss factor Q, but increase with the magnetic mirror ratio σ as well as with the steepness index δ. Moreover, the evolution of FEBs can also significantly influence the fastest growing mode and the fastest growing phase angle. This leads to the change of the polarization sense of the ECM emission. In particular, our results also reveal that an FEB that undergoes different evolution processes will generate different types of ECM emission. We believe the present results to be very helpful for a more comprehensive understanding of the dynamic spectra of solar radio bursts.

  6. BIM experiment module and its flight on MASER 10

    NASA Astrophysics Data System (ADS)

    Holm, Per; Löfgren, Oscar; Huijser, Ron; Willemsen, Harry

    2005-08-01

    The Biology In Microgravity (BIM) experiment module was flown in microgravity during 6 minutes on the sounding rocket MASER 10 on May 2, 2005. Swedish Space Corporation, Dutch Space and CCM developed the BIM module under contract from the European Space Agency (ESA). Two cell biology experiments were flown in the BIM module: ACTIN, Role of microgravity on actin metabolism in mammalian cells. Investigator: Prof. Dr. Johannes Boonstra, University of Utrecht (NL). AMUSE, Influence of micrograviy on activation of NF-κB, a principal regulator of inflammation and immunity. Investigator: Prof. Dr. Maikel Peppelenbosch, University of Groningen (NL). The BIM experiments were performed in 48 experiment units containing culture chambers and liquid storage reservoirs with additives, which were added to the culture chambers during the microgravity period of six minutes. Cultures in microgravity and on a 1xg reference centrifuge on-board the module were activated simultaneously with a reference on-ground. The experiment units were prepared hours before launch and were integrated in late access insert systems. The flight system was installed in the module via a hatch. The ground system, with the reference experiment units, was placed in an incubator. During the flight, when microgravity was achieved, all actions were performed to activate and, just before end of microgravity, fixate the experiment samples. The thermal control and the centrifuge worked properly. Due to a hard landing the module was severely damaged, nevertheless almost all experiments could be saved.

  7. Electron-cyclotron maser and solar microwave millisecond spike emission

    NASA Technical Reports Server (NTRS)

    Li, Hong-Wei; Li, Chun-Sheng; Fu, Qi-Jun

    1986-01-01

    An intense solar microwave millisecond spike emission (SMMSE) event was observed on May 16, 1981 by Zhao and Jin at Beijing Observatory. The peak flux density of the spikes is high to 5 x 100,000 s.f.u. and the corresponding brightness temperature (BT) reaches approx. 10 to the 15th K. In order to explain the observed properties of SMMSE, it is proposed that a beam of electrons with energy of tens KeV injected from the acceleration region downwards into an emerging magnetic arch forms so-called hollow beam distribution and causes electron-cyclotron maser (ECM) instability. The growth rate of second harmonic X-mode is calculated and its change with time is deduced. It is shown that the saturation time of ECM is t sub s approx. equals 0.42 ms and only at last short stage (delta t less than 0.2 t sub s) the growth rate decreases to zero rather rapidly. So a SMMSE with very high BT will be produced if the ratio of number density of nonthermal electrons to that of background electrons, n sub s/n sub e, is larger than 4 x .00001.

  8. Spectral dynamics of a collective free electron maser

    SciTech Connect

    Eecen, P.J.; Schep, T.J.; Tulupov, A.V.

    1995-12-31

    A theoretical and numerical study of the nonlinear spectral dynamics of a Free Electron Maser (FEM) is reported. The electron beam is modulated by a step-tapered undulator consisting of two sections with different strengths and lengths. The sections have equal periodicity and are separated by a field-free gap. The millimeter wave beam is guided through a rectangular corrugated waveguide. The electron energy is rather low and the current density is large, therefore, the FEM operates in the collective (Raman) regime. Results of a computational study on the spectral dynamics of the FEM are presented. The numerical code is based on a multifrequency model in the continuous beam limit with a 3D description of the electron beam. Space-charge forces are included by a Fourier expansion. These forces strongly influence the behaviour of the generated spectrum of the FEM. The linear gain of the FEM is high, therefore, the system quickly reaches the nonlinear regime. In saturation the gain is still relatively high and the spectral signal at the resonant frequency of the second undulator is suppressed. The behaviour of the sidebands is analysed and their dependence on mirror reflectivity and undulator parameters will be discussed.

  9. Methanol crossover in direct methanol fuel cell systems.

    SciTech Connect

    Pivovar, B. S.; Bender, G.; Davey, J. R.; Zelenay, P.

    2003-01-01

    Direct methanol fuel cells (DMFCs) are currently being investigated for a number of different applications from several milliwatts to near kilowatt size scales (cell phones, laptops, auxiliary power units, etc .). Because methanol has a very high energy density, over 6000 W hr/kg, a DMFC can possibly have greatly extended lifetimes compared to the batteries, doesn't present the storage problems associated with hydrogen fuel cells and can possibly operate more efficiently and cleanly than internal combustion engines.

  10. MMIC Amplifiers for 90 to 130 GHz

    NASA Technical Reports Server (NTRS)

    Samoska, Lorene; Pukala, David; Peralta, Alejandro; Bryerton, Eric; Morgan, Matt; Boyd, T.; Hu, Ming; Schmitz, Adele

    2007-01-01

    This brief describes two monolithic microwave integrated-circuit (MMIC) amplifier chips optimized to function in the frequency range of 90 to 130 GHz, covering nearly all of F-band (90 - 140 GHz). These amplifiers were designed specifically for local-oscillator units in astronomical radio telescopes such as the Atacama Large Millimeter Array (ALMA). They could also be readily adapted for use in electronic test equipment, automotive radar systems, and communications systems that operate between 90 and 130 GHz.

  11. SiO and H2O Maser Survey toward Post-asymptotic Giant Branch and Asymptotic Giant Branch Stars

    NASA Astrophysics Data System (ADS)

    Yoon, Dong-Hwan; Cho, Se-Hyung; Kim, Jaeheon; Yun, Young joo; Park, Yong-Sun

    2014-03-01

    We performed simultaneous observations of SiO v = 1, 2, 29SiO v = 0, J = 1-0 and H2O 616-523 maser lines toward 143 AGB and 164 post-asymptotic giant branch (AGB) stars in order to investigate how evolutionary characteristics from AGB to post-AGB stars appear in both SiO and H2O maser emissions. The observations were carried out from 2011 February to 2012 March using the Korean VLBI Network single-dish telescopes. We have detected SiO and/or H2O maser emission from 21 sources out of 164 post-AGB stars including 12 new detections. Of 143 AGB stars, we detected SiO and/or H2O maser emission from 44 stars including 24 new detections. SiO v = 2, J = 1-0 maser emission without a SiO v = 1 maser was detected from 7 sources among 14 SiO-detected post-AGB stars, and the intensity of the SiO v = 2, J = 1-0 maser tends to be much stronger than that of SiO v = 1, which is different from those of AGB stars. This may be related to the development of hot dust shells according to the evolutionary processes of post-AGB stars. We also found that both SiO and H2O masers were detected in the blue group (LI, or Left of IRAS), while only the H2O maser was detected in the red group (RI, or Right of IRAS) for post-AGB stars. These different detection rates between SiO and H2O masers may originate from the different abundances of masing molecules in the circumstellar envelope according to the different mass and expansion velocity between LI and RI regions together with their evolutionary stages.

  12. Cold hydrogen maser research at SAO (Smithsonian Astrophysical Observatory) and related developments

    SciTech Connect

    Vessot, R.F.C.; Mattison, E.M.; Imbier, E.

    1983-01-01

    The cryogenically-cooled maser provides a means for measuring frequency shifts and relaxation properties of storage wall coating materials that can be frozen in place from substances normally in the gaseous phase. We report initial measurements for FEP-120 Teflon between 77K and 48K and compare them with the 372K to 77K data of de Saintfuscien. Some of the design features of the maser are described. The cryomaser's hydrogen dissociator is located entirely within the vacuum enclosure and operates at 77K. The in-vacuum dissociator and other developments that have been adapted and tested in a room temperature maser, and that are applicable for both space and terrestrial use, are also discussed.

  13. Development of cross-correlation spectrometry and the coherent structures of maser sources

    NASA Astrophysics Data System (ADS)

    Takefuji, Kazuhiro; Imai, Hiroshi; Sekido, Mamoru

    2016-10-01

    We have developed a new method of data processing for radio telescope observation data to measure time-dependent temporal coherence, and we have named it "cross-correlation spectrometry" (XCS). XCS is an autocorrelation procedure that expands time lags over the integration time and is applied to data obtained from a single-dish observation. The temporal coherence property of received signals is enhanced by XCS. We tested the XCS technique using the data of strong H2O masers in W 3 (H2O), W 49 N, and W 75 N. We obtained the temporal coherent lengths of the maser emission to be 17.95 ± 0.33 μs, 26.89 ± 0.49 μs, and 15.95 ± 0.46 μs for W 3 (H2O), W 49 N, and W 75 N, respectively. These results may indicate the existence of a coherent astrophysical maser.

  14. Millimeter Wave and Terahertz Spectra of C-13 Methanol

    NASA Astrophysics Data System (ADS)

    Xu, Li-Hong; Lees, Ronald M.; Müller, Holger S. P.; Endres, Christian P.; Lewen, Frank; Schlemmer, Stephan; Menten, Karl M.

    2009-06-01

    Methanol is a very ubiquitous molecule in space. A previous combined analysis of microwave and millimeter wave spectra of C-13 methanol together with Fourier transform far-infrared spectra was limited to the first two torsional states (i.e. v_t = 0 and 1 for J values up to 20). We have recently carried out new millimeter and terahertz measurements for ^{13}CH_3OH on several different spectrometers in the Cologne laboratory to overcome the limits in frequency and quantum number coverage. The new measurements have been carried out in the frequency windows 34-70 GHz, 75-120 GHz, 240-340 GHz, 370-500 GHz and 1.12-1.35 THz. With the new data, we are extending our previous global treatment to include the first three torsional states (i.e. v_t = 0, 1 and 2 for J values up to 30). We hope to provide the radio astronomical community with a C-13 methanol database that will have been improved substantially compared to the existing one. The new database will be available in the Cologne Database for Molecular Spectroscopy, CDMS, in support of present and future astronomical studies associated with the launch of HIFI (Heterodyne Instrument for the Far-Infrared) on board the Herschel Space Observatory, the flying of SOFIA (Stratospheric Observatory For Infrared Astronomy) and the commissioning of ALMA (Atacama Large Millimeter/Submillimeter Array). Li-Hong Xu, M. S. Walsh, R. M. Lees, 1996, J. Mol. Spectrosc. 179, 269-281. Li-Hong Xu, F. J. Lovas, 1997, J. Phys. Chem. Ref. Data, 26, 17-156; also available in the CDMS, see ^c. H. S. P. Müller, S. Thorwirth, D. A. Roth, G. Winnewisser, 2001, Astron. Astrophys. 370, L49-L52 H. S. P. Müller, F. Schlöder, J. Stutzki, G. Winnewisser, 2005 J. Mol. Struct. 742, 215-227; web-page: http://www.astro.uni-koeln.de/cdms/.

  15. Methanol Oxidation on Pt3Sn(111) for Direct Methanol Fuel Cells: Methanol Decomposition.

    PubMed

    Lu, Xiaoqing; Deng, Zhigang; Guo, Chen; Wang, Weili; Wei, Shuxian; Ng, Siu-Pang; Chen, Xiangfeng; Ding, Ning; Guo, Wenyue; Wu, Chi-Man Lawrence

    2016-05-18

    PtSn alloy, which is a potential material for use in direct methanol fuel cells, can efficiently promote methanol oxidation and alleviate the CO poisoning problem. Herein, methanol decomposition on Pt3Sn(111) was systematically investigated using periodic density functional theory and microkinetic modeling. The geometries and energies of all of the involved species were analyzed, and the decomposition network was mapped out to elaborate the reaction mechanisms. Our results indicated that methanol and formaldehyde were weakly adsorbed, and the other derivatives (CHxOHy, x = 1-3, y = 0-1) were strongly adsorbed and preferred decomposition rather than desorption on Pt3Sn(111). The competitive methanol decomposition started with the initial O-H bond scission followed by successive C-H bond scissions, (i.e., CH3OH → CH3O → CH2O → CHO → CO). The Brønsted-Evans-Polanyi relations and energy barrier decomposition analyses identified the C-H and O-H bond scissions as being more competitive than the C-O bond scission. Microkinetic modeling confirmed that the vast majority of the intermediates and products from methanol decomposition would escape from the Pt3Sn(111) surface at a relatively low temperature, and the coverage of the CO residue decreased with an increase in the temperature and decrease in partial methanol pressure.

  16. Methanol related deaths in Edirne.

    PubMed

    Azmak, Derya

    2006-01-01

    In this retrospective autopsy study, a detailed analysis of methanol related deaths in Trakya region of Turkey is presented and departmental autopsy records, toxicology and histopathology results are analyzed. We found that methanol poisonings comprise 2.83% of all forensic autopsies (n:18), 88.8% of the cases were male, most of the victims were aged between 41 and 45. Blood methanol concentrations range widely from 55 to 479 mg per 100ml. Ethyl alcohol was detected in 44.4% of the cases. Most of the cases died in hospital and were poisoned through the consumption of alcoholic beverages from illicit sources and colognes. It is important for physicians to be aware of methanol poisoning symptoms and for forensic pathologists to obtain samples for toxicology during autopsies. Some preventative strategies including to routine control of the stores, to prevent the production of illegal alcoholic beverages, etc. should be developed.

  17. H2O and OH masers associated with cold infrared sources

    NASA Astrophysics Data System (ADS)

    Colom, P.; Lekht, E. E.; Pashchenko, M. I.; Rudnitskii, G. M.; Tolmachev, A. M.

    2015-08-01

    We present the results of our monitoring of four maser sources associated with cold infrared sources. The observations were performed in the water-vapor line at 1.35 cm with the 22-m radio telescope at the Pushchino Radio Astronomy Observatory and in the hydroxyl lines at 18 cm with the Nançay radio telescope. Cyclic variability of the H2O maser emission was detected in all four sources. The durations of the cycles are different and lie within the range 1.8-5.5 yr. In each source, the cycles differed by a factor from 1.5 to 2.25. A fairly periodic pattern of variability was observed in IRAS 20126+4104 on a time scale from 3.6 to 5.3 yr. Models of the maser sources are discussed. In IRAS 20126+4104, we detected strong variability of the maser emission in the main OH 1665 and 1667 MHz lines. We calculated the magnetic field strength for two maser features from the Zeeman splitting of the OH line: in IRAS 18265-1517 (1.3 mG at epoch 2008) and IRAS 20126+4104 (10 mG at epoch 2014). Variability of the magnetic field was detected in the second feature. In the same sources, we detected maser emission in the 1667 MHz OH line. The presence of emission in both main OH 1665 and 1667 MHz lines is consistent with the existing model calculations and will allow the gas density in the masing regions to be refined.

  18. VizieR Online Data Catalog: Arcetri Catalogue of H2O Maser Sources (Brand+ 1994)

    NASA Astrophysics Data System (ADS)

    Brand, J.; Cesaroni, R.; Caselli, P.; Catarzi, M.; Codella, C.; Comoretto, G.; Curioni, G. P.; Curioni, P.; di, Franco S.; Felli, M.; Giovanardi, C.; Olmi, L.; Palagi, F.; Palla, F.; Panella, D.; Pareschi, G.; Rossi, E.; Speroni, N.; Tofani, G.

    1993-11-01

    An update is presented of the Arcetri Atlas of water masers (Comoretto et al. 1990A&AS...84..179C). It contains the results of observations of water masers with the Medicina 32-m antenna. The observed sources were all discovered in the period 1989-1993, and were found either directly in the course of our own programs or were taken from the literature in which case they were re-observed at Medicina. We give the observed parameters of 214 sources in tabular form, and present all the spectra of the 141 detections. (2 data files).

  19. Probing Planck-Scale physics with a Ne-21/He-3 Zeeman maser

    NASA Technical Reports Server (NTRS)

    Walsworth, Ronald L.; Phillips, David

    2004-01-01

    We completed a search for a sidereal annual variation in the frequency difference between co-located Xe-129 and He-3 Zeeman masers. This search sets a stringent limit of approximately 10(exp -27) GeV on boost-dependent Lorentz and CPT violation involving the neutron. A paper reporting this result has been accepted for publication in Physical Review Letters. We also completed detailed modeling and design of the next-generation dual-noble-gas Zeeman maser for an improved test of Lorentz and CPT violation, and begin construction of this device.

  20. Resonant electron diffusion as a saturation process of the synchrotron maser instability. [of auroral kilometric radiation

    NASA Technical Reports Server (NTRS)

    Lee, M. C.; Kuo, S. P.

    1986-01-01

    The theory of resonant electron diffusion as an effective saturation process of the auroral kilometric radiation has been formulated. The auroral kilometric radiation is assumed to be amplified by the synchrotron maser instability that is driven by an electron distribution of the loss-cone type. The calculated intensity of the saturated radiation is found to have a significantly lower value in comparison with that caused by the quasi-linear diffusion process as an alternative saturation process. This indicates that resonant electron diffusion dominates over quasi-linear diffusion in saturating the synchrotron maser instability.

  1. Relativistic dispersion modifications to the cyclotron maser theory of planetary radio emissions

    NASA Technical Reports Server (NTRS)

    Pritchett, P. L.; Strangeway, R. J.

    1986-01-01

    The effects of relativistic dispersion on the electron-cyclotron maser instability are investigated by linear theory, electromagnetic particle simulation, and quasilinear theory. When vsq/csq greater than or = omega pesq/Omega sq for the energetic electrons, the instability is localized just below k c/Omega e = 1, and the growth rate is strongly peaked for emission at 90 deg to the magnetic field. Saturation of the instability is due to perpendicular diffusion in momentum space, and the saturation level increases as omega pe/Omega e is decreased. Applications of the maser instability to the generation of the Earth's auroral kilometric radiation are discussed.

  2. ACCRETION DISK WARPING BY RESONANT RELAXATION: THE CASE OF MASER DISK NGC 4258

    SciTech Connect

    Bregman, Michal; Alexander, Tal

    2009-08-01

    The maser disk around the massive black hole (MBH) in active galaxy NGC 4258 exhibits an O(10 deg.) warp on the O(0.1 pc) scale. The physics driving the warp is still debated. Suggested mechanisms include torquing by relativistic frame dragging or by radiation pressure. We propose here a new warping mechanism: resonant torquing of the disk by stars in the dense cusp around the MBH. We show that resonant torquing can induce such a warp over a wide range of observed and deduced physical parameters of the maser disk.

  3. Probing AGN with Masers and X-Rays-SAX Proposals

    NASA Technical Reports Server (NTRS)

    Wilkes, Belinda J.; White, Nicholas (Technical Monitor)

    2001-01-01

    We have made BeppoSAX observations of the Seyfert 2/1.9 galaxy ESO103-G35, which contains a nuclear maser source and is known to be heavily absorbed in the X-rays. Analysis of the X-ray spectra observed by SAX in October 1996 and 1997 yields an energy index = 0.74 +/- 0.07, typical of Seyfert galaxies and consistent with earlier observations of this source. The strong, soft X-ray absorption has a column density, N_H of (1.79 +/- 0.09)E23 cmE-02, again consistent with earlier results. The best fitting spectrum is that of a power law with a high energy cutoff at 29 +/- 10 keV, a cold (E=6.3 +/- 0.1 keV, rest frame), marginally resolved (sigma = 0.35 +/- 0.14 keV, FWHM approximately (31 +/- 12)E03 km/s) FeKalpha line with EW 290 +100 -80 eV (1996) and a mildly ionized Fe K-edge at 7.37 +0.15 -0.21 keV, tau 0.24 +0.06 -0.09. The Fe Kalpha line and cold absorption are consistent with origin in a accretion disk/torus through which our line-of-sight passes at a radial distance of approximately 0.01 pc. The Fe K-edge is mildly ionized suggesting the presence of ionized gas probably in the inner accretion disk, close to the central source or in a separate warm absorber. The data quality is too low to distinguish between these possibilities but the edge-on geometry implied by the water maser emission favors the former. Comparison with earlier observations of ESO103-G35 shows little/no change in spectral parameters while the flux changes by factors of a few on timescales of a few months. The 2-10 keV flux decreased by a factor of approximately 2.7 between Oct 1996 and Oct 1997 with no detectable change in the count rate greater than 20 keV (i.e. the PDS data). Spectral fits to the combined datasets indicate either a significant hardening of the spectrum (energy index approximately 0.5) or an approximate constant or delayed response reflection component. The high energy cutoff (29 +/- 10 keV) is lower than the typical approximately 300 keV values seen in Seyfert galaxies. A

  4. Teleportation of a 3-dimensional GHZ State

    NASA Astrophysics Data System (ADS)

    Cao, Hai-Jing; Wang, Huai-Sheng; Li, Peng-Fei; Song, He-Shan

    2012-05-01

    The process of teleportation of a completely unknown 3-dimensional GHZ state is considered. Three maximally entangled 3-dimensional Bell states function as quantum channel in the scheme. This teleportation scheme can be directly generalized to teleport an unknown d-dimensional GHZ state.

  5. The MALT 90 GHz Pilot Survey

    NASA Astrophysics Data System (ADS)

    Jackson, James; Rathborne, Jill; Muller, Erik; Cunningham, Maria; Brooks, Kate; Fuller, Gary; Barnes, Peter; Ellingsen, Simon; Longmore, Steven; Wyrowski, Friedrich; Walsh, Andrew; Peretto, Nicolas

    2009-04-01

    In early November, 2008, Australian and international Galactic astronomers met to plan future surveys of the Galactic plane with ATNF facilities. We intend to coordinate our efforts so that such surveys produce the maximum scientific return with minimal overlap in observations. To this end, the Millimetre Astronomers Large-area multi-Transition (MALT) team was formed. The MALT team has identified key Galactic plane surveys: a 42--50 GHz survey, a 90 GHz survey and a 115 GHz survey. In this proposal, we aim to conduct a pilot survey to explore options in the 90 GHz (3 mm) range. This pilot survey will provide detection rates, typical line strengths, and source sizes for various "finder charts" for high-mass star-forming cores. Such information is crucial for a rational design of a complete 90 GHz MALT survey.

  6. MULTIPLE HIGH-VELOCITY SiO MASER FEATURES FROM THE HIGH-MASS PROTOSTAR W51 NORTH

    SciTech Connect

    Cho, Se-Hyung; Kim, Jaeheon; Byun, Do-Young E-mail: jhkim@kasi.re.kr

    2011-02-01

    We present the detection of multiple high-velocity silicon monoxide (SiO v = 1, 2, J = 1-0) maser features in the high-mass protostar W51 North which are distributed over an exceedingly large velocity range from 105 to 230 km s{sup -1}. The SiO v = 1, J = 1-0 maser emission shows 3-5 narrow components which span a velocity range from 154 to 230 km s{sup -1} according to observational epochs. The SiO v = 2, J = 1-0 maser also shows 3-5 narrow components that do not correspond to the SiO v = 1 maser and span a velocity range from 105 to 154 km s{sup -1}. The multiple maser components show significant changes on very short timescales (<1 month) from epoch to epoch. We suggest that the high-velocity SiO masers may be emanated from massive star-forming activity of the W51 North protostar as SiO maser jets and will be a good probe of the earliest evolutionary stages of high-mass star formation via an accretion model. Further high angular resolution observations will be required for confirmation.

  7. Analytical methods for measuring the parameters of interstellar gas using methanol observations

    NASA Astrophysics Data System (ADS)

    Kalenskii, S. V.; Kurtz, S.

    2016-08-01

    The excitation of methanol in the absence of external radiation is analyzed, and LTE methods for probing interstellar gas considered. It is shown that rotation diagrams correctly estimate the gas kinetic temperature only if they are constructed using lines whose upper levels are located in the same K-ladders, such as the J 0- J -1 E lines at 157 GHz, the J 1- J 0 E lines at 165 GHz, and the J 2- J 1 E lines at 25 GHz. The gas density must be no less than 107 cm-3. Rotation diagrams constructed from lines with different K values for their upper levels (e.g., 2 K -1 K at 96 GHz, 3 K -2 K at 145 GHz, 5 K -4 K at 241 GHz) significantly underestimate the temperature, but enable estimation of the density. In addition, diagrams based on the 2 K -1 K lines can be used to estimate the methanol column density within a factor of about two to five. It is suggested that rotation diagrams should be used in the following manner. First, two rotation diagrams should be constructed, one from the lines at 96, 145, or 241 GHz, and another from the lines at 157, 165, or 25 GHz. The former diagram is used to estimate the gas density. If the density is about 107 cm-3 or higher, the latter diagram reproduces the temperature fairly well. If the density is around 106 cm-3, the temperature obtained from the latter diagram should be multiplied by a factor of 1.5-2. If the density is about 105 cm-3 or lower, then the latter diagram yields a temperature that is lower than the kinetic temperature by a factor of three or more, and should be used only as a lower limit for the kinetic temperature. The errors in the methanol column density determined from the integrated intensity of a single line can be more than an order of magnitude, even when the gas temperature is well known. However, if the J 0-( J - 1)0 E lines, as well as the J 1-( J - 1)1 A + or A - lines are used, the relative error in the column density is no more than a factor of a few.

  8. Rapid starting methanol reactor system

    DOEpatents

    Chludzinski, Paul J.; Dantowitz, Philip; McElroy, James F.

    1984-01-01

    The invention relates to a methanol-to-hydrogen cracking reactor for use with a fuel cell vehicular power plant. The system is particularly designed for rapid start-up of the catalytic methanol cracking reactor after an extended shut-down period, i.e., after the vehicular fuel cell power plant has been inoperative overnight. Rapid system start-up is accomplished by a combination of direct and indirect heating of the cracking catalyst. Initially, liquid methanol is burned with a stoichiometric or slightly lean air mixture in the combustion chamber of the reactor assembly. The hot combustion gas travels down a flue gas chamber in heat exchange relationship with the catalytic cracking chamber transferring heat across the catalyst chamber wall to heat the catalyst indirectly. The combustion gas is then diverted back through the catalyst bed to heat the catalyst pellets directly. When the cracking reactor temperature reaches operating temperature, methanol combustion is stopped and a hot gas valve is switched to route the flue gas overboard, with methanol being fed directly to the catalytic cracking reactor. Thereafter, the burner operates on excess hydrogen from the fuel cells.

  9. Water-maser emission from a planetary nebula with a magnetized torus.

    PubMed

    Miranda, L F; Gómez, Y; Anglada, G; Torrelles, J M

    2001-11-15

    A star like the Sun becomes a planetary nebula towards the end of its life, when the envelope ejected during the earlier giant phase becomes photoionized as the surface of the remnant star reaches a temperature of approximately 30,000 K. The spherical symmetry of the giant phase is lost in the transition to a planetary nebula, when non-spherical shells and powerful jets develop. Molecules that were present in the giant envelope are progressively destroyed by the radiation. The water-vapour masers that are typical of the giant envelopes therefore are not expected to persist in planetary nebulae. Here we report the detection of water-maser emission from the planetary nebula K3-35. The masers are in a magnetized torus with a radius of about 85 astronomical units and are also found at the surprisingly large distance of about 5,000 astronomical units from the star, in the tips of bipolar lobes of gas. The precessing jets from K3-35 are probably involved in the excitation of the distant masers, although their existence is nevertheless puzzling. We infer that K3-35 is being observed at the very moment of its transformation from a giant star to a planetary nebula. PMID:11713522

  10. Effects of hydrogen atom spin exchange collisions on atomic hydrogen maser oscillation frequency

    NASA Technical Reports Server (NTRS)

    Crampton, S. B.

    1979-01-01

    Frequency shifts due to collisions between hydrogen atoms in an atomic hydrogen maser frequency standard are studied. Investigations of frequency shifts proportional to the spin exchange frequency shift cross section and those proportional to the duration of exchange collisions are discussed. The feasibility of operating a hydrogen frequency standard at liquid helium temperatures is examined.

  11. Hot-gas cold-dust pumping for water masers associated with H II regions

    NASA Technical Reports Server (NTRS)

    Deguchi, S.

    1981-01-01

    A collisional pump with an internal sink is proposed for the water masers associated with H II regions, where the population inversion occurs due to the absorption by cold ice-mantle grains in a highly dusty cloud of the far-infrared line radiation of hot water vapor. A new escape probability method is developed to calculate the transfer of line radiation in dusty medium. The pump mechanism explains the power of usual maser sources associated with H II regions and the enormous power of the sources associated with W49 N and external galaxies. Models of maser clouds have a radius of 5 x 10 to the 15th-10 to the 16th cm, an H2 number density of 4 x 10 to the 9th/cu cm, an expansion velocity of 10-30 km/s, a kinetic temperature of 350 K, and a grain temperature of 100 K. Giant maser sources require grains of the size about 1 micron. The apparent size of the emission spots (approximately 10 to the 13th cm) observed by VLBI is interpreted as due to a fluctuation in the cloud, and the assembly of the spots is spread within a size of 10 to the 16th cm. The temperature difference between the dust and gas is due to a relaxation process after an infrared burst accompanying protostar formation.

  12. Maser emission of the most abundant SiO isotopomers in O-rich stars

    NASA Astrophysics Data System (ADS)

    Rizzo, J. R.; García Miró, C.; Cernicharo, J.

    2015-05-01

    SiO maser emission constitutes one of the most puzzling cases in spectroscopy. The overall inversion of the rotational transitions in each vibrational ladder is rather well understood. However, there are a number of anomalies in specific rotational transitions that are still unexplained. O-rich stars are probably the most powerful maser emitters known to date, and therefore the best candidates to model the SiO maser emission at different rotational and vibrational levels. In order to properly tackle the SiO excitation problem, it is vital to simultaneously observe a large number of SiO (and isotopomers) lines in a large and varied sample of sources. We profit the availability of new wideband backends to carry out a deep survey of ^{28}SiO, ^{29}SiO, and ^{30}SiO maser emission, in a sample of 67 evolved O-rich stars. The survey was done using the DSS-54 antenna at the Madrid Deep Space Communications complex in Robledo, and the IRAM 30m radio telescope at Pico Veleta. A total of 61 lines were observed, including rotational transitions from J=1→0 to J=5→4, for vibrational levels from 0 to 6. In this contribution, overall results of the survey are presented.

  13. Electron-cyclotron maser instability driven by a loss-cone distribution

    SciTech Connect

    Lau, Y.Y.; Chu, K.

    1983-01-24

    It is shown that the electron-cyclotron maser instabilities may readily be excited in a plasma with a loss-cone distribution when the electron temperature exceeds a few tens of kiloelectronvolts. The growth rate is typically a few percent of the electron-cyclotron frequency. The appearance of the instability can be avoided by proper control of the plasma density.

  14. Progress Report on the Development of a Laser/Maser Vocabulary.

    ERIC Educational Resources Information Center

    Lerner, Rita G.

    The development of a laser/maser vocabulary follows the pattern established earlier in two similar projects--(1) Development of a Multi-Coordinate Vocabulary--Chemical Physics, and (2) Development of a Multi-Coordinate Index--Plasma Physics. A set of lists of terms judged to be important to a user of information was developed by a specialist in…

  15. Position-Velocity Diagrams for the Maser Emission Coming from a Keplerian Ring

    NASA Astrophysics Data System (ADS)

    Uscanga, Lucero; Cantó, Jorge; Raga, Alejandro C.

    2007-07-01

    We have studied the maser emission from a thin, planar, gaseous ring in Keplerian rotation around a central mass observed edge-on. The absorption coefficient within the ring is assumed to follow a power-law dependence on the distance from the central mass as κ=κ0r-q. We have calculated position-velocity diagrams for the most intense maser features, for different values of the exponent q. We have found that, depending on the value of q, these diagrams can be qualitatively different. The most intense maser emission at a given velocity can come mainly from either regions close to the inner or outer edges of the amplifying ring or the line perpendicular to the line of sight and passing through the central mass (as is commonly assumed). Particularly, when q>1 the position-velocity diagram is qualitatively similar to the one observed for the water maser emission in the nucleus of the galaxy NGC 4258. In the context of this simple model, we conclude that in this object the absorption coefficient depends on the radius of the amplifying ring as a decreasing function, in order to have significant emission coming from the inner edge of the ring.

  16. Test of relativistic gravitation with a space-borne hydrogen maser

    NASA Technical Reports Server (NTRS)

    Vessot, R. F. C.; Levine, M. W.; Mattison, E. M.; Blomberg, E. L.; Hoffman, T. E.; Nystrom, G. U.; Farrel, B. F.; Decher, R.; Eby, P. B.; Baugher, C. R.

    1980-01-01

    The results of a test of general relativity with use of a hydrogen-maser frequency standard in a spacecraft launched nearly vertically upward to 10,000 km are reported. The agreement of the observed relativistic frequency shift with prediction is at the 70 x 10 to the -6th level.

  17. Ball Lightning With Spiking and Cold Emission in the Maser-Caviton Interaction

    NASA Astrophysics Data System (ADS)

    Handel, P. H.; Carlson, G. A.; Leitner, J.

    2007-05-01

    The nonlinear system of maser and cold plasma caviton can sustain spiking oscillations around the stationary state. This is shown here in the linearized limit of small oscillations. The role of ionization and cold emission effects is considered, and the case of large spiking amplitudes is discussed qualitatively on this basis. This calculation allows us to predict the frequency of the often observed humming of ball lightning. Furthermore, four basic experiments are suggested, that should be performed in order to verify and further develop the present Maser-Soliton theory of ball lightning: comparative atmospheric absorption spectroscopy in thunderstorm conditions, electric field pulse experiment, wind tunnel experiment and laboratory ball lightning generation experiment. The latter experiment suggested is based on a 10-20KW Klystron amplifier with negative feedback, trying to simulate the behavior of the atmospheric maser. The klystron is connected through a directional coupler to a tuned resonator that serves as discharge chamber. From there, a wave guide completes the loop. An optical feedback strengthens the natural tendency of the klystron to spike almost instantaneously when the load decreases. The discharge sought is a glow at atmospheric pressure, at much lower temperature than the lowest temperature arch discharge ever obtained so far at normal pressure. At these low temperatures there are no electrons that could sustain the discharge. However, right when the discharge is dying, a powerful klystron spike is automatically caused by the sudden decrease of the load. This extracts electrons through cold (Fowler) emission, and rekindles the discharge. However, like in the case of the atmospheric maser, the presence of the large spike automatically stops the klystron power. The optical feedback is responsible in part for the fast reaction. Then the spiking cycle repeats itself. Our Maser-Soliton BL theory allows for the first time not only to understand the

  18. OBSERVATIONAL STUDY OF THE CONTINUUM AND WATER MASER EMISSION IN THE IRAS 19217+1651 REGION

    SciTech Connect

    Rodriguez-Esnard, T.; Trinidad, M. A.; Migenes, V. E-mail: trinidad@astro.ugto.mx

    2012-12-20

    We report interferometric observations of the high-mass star-forming region IRAS 19217+1651. We observed the radio continuum (1.3 cm and 3.6 cm) and water maser emission using the Very Large Array (VLA-EVLA) in transition mode (configuration A). Two radio continuum sources were detected at both wavelengths, I19217-A and I19217-B. In addition, 17 maser spots were observed distributed mainly in two groups, M1 and M2, and one isolated maser. This latter could be indicating the relative position of another continuum source which we did not detect. The results indicate that I19217-A appears to be consistent with an ultracompact H II region associated with a zero-age main-sequence B0-type star. Furthermore, the 1.3 cm continuum emission of this source suggests a cometary morphology. In addition, I19217-B appears to be an H II region consisting of at least two stars, which may be contributing to its complex structure. It was also found that the H{sub 2}O masers of the group M1 are apparently associated with the continuum source I19217-A. These are tracing motions which are not gravitationally bound according to their spatial distribution and kinematics. They also seem to be describing outflows in the direction of the elongated cometary region. On the other hand, the second maser group, M2, could be tracing the base of a jet. Finally, infrared data from Spitzer, Midcourse Space Experiment, and IRIS show that IRAS 19217+1651 is embedded inside a large open bubble, like a broken ring, which possibly has affected the morphology of the cometary H II region observed at 1.3 cm.

  19. 23 GHz ferroelectric electron gun based gyrotron

    NASA Astrophysics Data System (ADS)

    Ben-Moshe, R.; Einat, M.

    2011-04-01

    Ferroelectric cathodes have been explored as an alternative electron source for microwave tubes. Past experiments have demonstrated operation at frequencies of 2-10 GHz. Since the ferroelectric cathode is based on surface plasma, the relatively high energy spread limits the tube operation frequency. Hence, the possibility to obtain higher frequencies remained questionable. In this experimental work a gyrotron oscillator was designed with the operation frequency increased toward that of millimeter waves. A cylindrical tube with a cutoff frequency of ˜22 GHz was integrated to a ferroelectric electron gun. Pulses of ˜0.5 μs duration with a frequency of 23 GHz were obtained.

  20. a Chirped-Pulse Fourier Transform Spectrometer Operating from 110 TO 170 GHZ

    NASA Astrophysics Data System (ADS)

    Bernier, Lauren E.; Shipman, Steven

    2014-06-01

    A chirped-pulse Fourier transform spectrometer operating from 110 - 170 GHz was constructed. The design of this spectrometer is directly adapted from that of the 260 - 295 GHz chirped-pulse spectrometer built by Steber and co-workers at the University of Virginia. In this instrument, an arbitrary waveform generator (AWG) produces a chirped pulse which is frequency shifted to a range between 9.2 and 14.1 GHz and then multiplied by a factor of 12 via an active multiplier chain to a range between 110 and 170 GHz. As in the Pate lab design, the AWG also serves as a local oscillator (LO) source; this LO is multiplied and used to downconvert the molecular emission, allowing it to be collected by a 40 GS/s digitizer. Benchmark measurements were taken for methanol at room temperature, and details of the instrument's performance will be discussed. A.L. Steber, B.J. Harris, J.L. Neill, and B.H. Pate, J. Mol. Spectrosc., 280, 3 (2012)

  1. Operating and environmental characteristics of Sigma Tau hydrogen masers used in the Very Long Baseline Array (VLBA)

    NASA Technical Reports Server (NTRS)

    Tucker, T. K.

    1989-01-01

    Presented here are the results obtained from performance evaluation of a pair of Sigma Tau Standards Corporation Model VLBA-112 active hydrogen maser frequency standards. These masers were manufactured for the National Radio Astronomy Observatory (NRAO) for use on the Very Long Baseline Array (VLBA) project and were furnished to the Jet Propulsion Laboratory (JPL) for the purpose of these tests. Tests on the two masers were performed in the JPL Frequency Standards Laboratory (FSL) and included the characterization of output frequency stability versus environmental factors such as temperature, humidity, magnetic field, and barometric pressure. The performance tests also included the determination of phase noise and Allan variance using both FSL and Sigma Tau masers as references. All tests were conducted under controlled laboratory conditions, with only the desired environmental and operational parameters varied to determine sensitivity to external environment.

  2. Air Breathing Direct Methanol Fuel Cell

    DOEpatents

    Ren; Xiaoming

    2003-07-22

    A method for activating a membrane electrode assembly for a direct methanol fuel cell is disclosed. The method comprises operating the fuel cell with humidified hydrogen as the fuel followed by running the fuel cell with methanol as the fuel.

  3. Cryogenic 160-GHz MMIC Heterodyne Receiver Module

    NASA Technical Reports Server (NTRS)

    Samoska, Lorene A.; Soria, Mary M.; Owen, Heather R.; Dawson, Douglas E.; Kangaslahti, Pekka P.; Gaier, Todd C.; Voll, Patricia; Lau, Judy; Sieth, Matt; Church, Sarah

    2011-01-01

    A cryogenic 160-GHz MMIC heterodyne receiver module has demonstrated a system noise temperature of 100 K or less at 166 GHz. This module builds upon work previously described in Development of a 150-GHz MMIC Module Prototype for Large-Scale CMB Radiation (NPO-47664), NASA Tech Briefs, Vol. 35, No. 8 (August 2011), p. 27. In the original module, the local oscillator signal was saturating the MMIC low-noise amplifiers (LNAs) with power. In order to suppress the local oscillator signal from reaching the MMIC LNAs, the W-band (75 110 GHz) signal had to be filtered out before reaching 140 170 GHz. A bandpass filter was developed to cover 120 170 GHz, using microstrip parallel-coupled lines to achieve the desired filter bandwidth, and ensure that the unwanted W-band local oscillator signal would be sufficiently suppressed. With the new bandpass filter, the entire receiver can work over the 140 180-GHz band, with a minimum system noise temperature of 460 K at 166 GHz. The module was tested cryogenically at 20 K ambient temperature, and it was found that the receiver had a noise temperature of 100 K over an 8-GHz bandwidth. The receiver module now includes a microstrip bandpass filter, which was designed to have a 3-dB bandwidth of approximately 120-170 GHz. The filter was fabricated on a 3-mil-thick alumina substrate. The filter design was based on a W-band filter design made at JPL and used in the QUIET (Q/U Imaging ExperimenT) radiometer modules. The W-band filter was scaled for a new center frequency of 150 GHz, and the microstrip segments were changed accordingly. Also, to decrease the bandwidth of the resulting scaled design, the center gaps between the microstrip lines were increased (by four micrometers in length) compared to the gaps near the edges. The use of the 150-GHz bandpass filter has enabled the receiver module to function well at room temperature. The system noise temperature was measured to be less than 600 K (at room temperature) from 154 to 168 GHz

  4. Enhanced methanol utilization in direct methanol fuel cell

    DOEpatents

    Ren, Xiaoming; Gottesfeld, Shimshon

    2001-10-02

    The fuel utilization of a direct methanol fuel cell is enhanced for improved cell efficiency. Distribution plates at the anode and cathode of the fuel cell are configured to distribute reactants vertically and laterally uniformly over a catalyzed membrane surface of the fuel cell. A conductive sheet between the anode distribution plate and the anodic membrane surface forms a mass transport barrier to the methanol fuel that is large relative to a mass transport barrier for a gaseous hydrogen fuel cell. In a preferred embodiment, the distribution plate is a perforated corrugated sheet. The mass transport barrier may be conveniently increased by increasing the thickness of an anode conductive sheet adjacent the membrane surface of the fuel cell.

  5. Air breathing direct methanol fuel cell

    DOEpatents

    Ren, Xiaoming

    2002-01-01

    An air breathing direct methanol fuel cell is provided with a membrane electrode assembly, a conductive anode assembly that is permeable to air and directly open to atmospheric air, and a conductive cathode assembly that is permeable to methanol and directly contacting a liquid methanol source.

  6. 47 CFR 15.251 - Operation within the bands 2.9-3.26 GHz, 3.267-3.332 GHz, 3.339-3.3458 GHz, and 3.358-3.6 GHz.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 1 2014-10-01 2014-10-01 false Operation within the bands 2.9-3.26 GHz, 3.267-3.332 GHz, 3.339-3.3458 GHz, and 3.358-3.6 GHz. 15.251 Section 15.251 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators Radiated Emission...

  7. 47 CFR 15.251 - Operation within the bands 2.9-3.26 GHz, 3.267-3.332 GHz, 3.339-3.3458 GHz, and 3.358-3.6 GHz.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 1 2013-10-01 2013-10-01 false Operation within the bands 2.9-3.26 GHz, 3.267-3.332 GHz, 3.339-3.3458 GHz, and 3.358-3.6 GHz. 15.251 Section 15.251 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators Radiated Emission...

  8. 47 CFR 15.251 - Operation within the bands 2.9-3.26 GHz, 3.267-3.332 GHz, 3.339-3.3458 GHz, and 3.358-3.6 GHz.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 1 2011-10-01 2011-10-01 false Operation within the bands 2.9-3.26 GHz, 3.267-3.332 GHz, 3.339-3.3458 GHz, and 3.358-3.6 GHz. 15.251 Section 15.251 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators Radiated Emission...

  9. Observation of Ammonia and Methanol in comet 67P with MIRO onboard Rosetta

    NASA Astrophysics Data System (ADS)

    Biver, N.; Gulkis, S.; Schloerb, F. P.; von Allmen, P.; Beaudin, G.; Bockelée-Morvan, D.; Choukroun, M.; Crovisier, J.; Encrenaz, T.; Encrenaz, P.; Freking, M.; Hartogh, P.; Hofstadter, M.; Ip, WH; Janssen, M.; Jarchow, C.; Lee, S.; Lellouch, E.; Leyrat, C.; Rezac, L.

    2015-10-01

    The Microwave Instrument on the Rosetta Orbiter (MIRO) [5] makes submillimeter- and millimeterwavelength observations of the nucleus and coma of the target of the Rosetta mission: comet 67P/Churyumov-Gerasimenko. MIRO is probing both the continuum emission of the nucleus at 0.5 and 1.6mm wavelength and the gaseous emission via highresolution spectroscopic measurements of 8 molecular lines in the submillimeter range (H2O, H17 2 O, H18 2 O, CO, NH3, and three lines of CH3OH). Since Rosetta arrived in the vicinity of comet 67P/Churyumov-Gerasimenko in July 2014, MIRO has been observing the coma almost continuously. Water emission at 556.9 GHz has been detected since early June 2014 [6] and the water outgassing of the comet and its spatial distribution has been regularly monitored and mapped [4, 6, 7]. MIRO is also observing the fundamental rotational transition JK=(10 - 00) of ammonia at 572.5 GHz and three lines of methanol: JK=(3-2 - 2-1E) at 568.6 GHz, (8+1 - 70E) at 553.1 GHz and (12-1 - 11-1E) at 579.2 GHz. The ammonia line and the lowest energy (3-2 - 2-1E) methanol line have been detected in absorption against the nucleus of the comet (Fig.1,2) and in emission in the coma since August 2014, when Rosetta was at distances between #10 to #100 km from the nucleus. We will present the results of one year of monitoring of the ammonia andmethanol emissions. Themeasured NH3 and CH3OH abundances relative to water in comet 67P/Churyumov-Gerasimenko will be compared to remote measurements made in several other comets [1, 2, 3].

  10. The direct methanol fuel cell

    SciTech Connect

    Halpert, G.; Narayanan, S.R.; Frank, H.

    1995-08-01

    This presentation describes the approach and progress in the ARPA-sponsored effort to develop a Direct Methanol, Liquid-Feed Fuel Cell (DMLFFC) with a solid Polymer Electrolyte Membrane (PEM) for battery replacement in small portable applications. Using Membrane Electrode Assemblies (MEAs) developed by JPL and Giner, significant voltage was demonstrated at relatively high current densities. The DMLFFC utilizes a 3 percent aqueous solution of methanol that is oxidized directly in the anode (fuel) chamber and oxygen (air) in the cathode chamber to produce water and significant power. The only products are water and CO{sub 2}. The ARPA effort is aimed at replacing the battery in the BA 5590 military radio.

  11. Methanol production method and system

    DOEpatents

    Chen, Michael J.; Rathke, Jerome W.

    1984-01-01

    Ethanol is selectively produced from the reaction of methanol with carbon monoxide and hydrogen in the presence of a transition metal carbonyl catalyst. Methanol serves as a solvent and may be accompanied by a less volatile co-solvent. The solution includes the transition metal carbonyl catalysts and a basic metal salt such as an alkali metal or alkaline earth metal formate, carbonate or bicarbonate. A gas containing a high carbon monoxide to hydrogen ratio, as is present in a typical gasifer product, is contacted with the solution for the preferential production of ethanol with minimal water as a byproduct. Fractionation of the reaction solution provides substantially pure ethanol product and allows return of the catalysts for reuse.

  12. Coaxial configuration for a wide-bandwidth dielectric Cherenkov maser amplifier

    SciTech Connect

    Shlapakovskii, A.S.

    1995-11-01

    A coaxial dielectric-lined waveguide is considered as the slow-wave supporting structure of the dielectric Cherenkov maser amplifier. Its basic ``quasi-TEM`` mode has very weak dispersion at phase velocities closed to the speed of light. This feature is attractive since it may provide the amplifier with very large bandwidth values. The system dispersion relation is derived for an infinitely thin hollow electron beam within a coaxial waveguide loaded with one dielectric liner located at either inner or outer conductor. Spatial growth rates are calculated numerically at various parameters of the slow-wave structure and electron beam. Bandwidth dependences on parameters are examined compared to those of the conventional dielectric Cherenkov maser configuration Constructive peculiarities of the coaxial configuration allowing original approaches to the problems of electron beam dumping and RF input and output matching are discussed.

  13. Test of an orbiting hydrogen maser clock system using laser time transfer

    NASA Technical Reports Server (NTRS)

    Vessot, Robert F. C.; Mattison, Edward M.; Nystrom, G. U.; Decher, Rudolph

    1992-01-01

    We describe a joint Smithsonian Astrophysical Laboratory/National Aeronautics and Space Administration (SAO/NASA) program for flight testing a atomic hydrogen maser clock system designed for long-term operation in space. The clock system will be carried by a shuttle-launched EURECA spacecraft. Comparisons with earth clocks to measure the clock's long-term frequency stability (tau = 10(exp 4) seconds) will be made using laser time transfer from existing NASA laser tracking stations. We describe the design of the maser clock and its control systems, and the laser timing technique. We describe the precision of station time synchronization and the limitations in the comparison between the earth and space time scales owing to gravitational and relativistic effects. We will explore the implications of determining the spacecraft's location by an on-board Global Position System (GPS) receiver, and of using microwave techniques for time and frequency transfer.

  14. Basic theory for polarized, astrophysical maser radiation in a magnetic field

    NASA Technical Reports Server (NTRS)

    Watson, William D.

    1994-01-01

    Fundamental alterations in the theory and resulting behavior of polarized, astrophysical maser radiation in the presence of a magnetic field have been asserted based on a calculation of instabilities in the radiative transfer. I reconsider the radiative transfer and find that the relevant instabilities do not occur. Calculational errors in the previous investigation are identified. In addition, such instabilities would have appeared -- but did not -- in the numerous numerical solutions to the same radiative transfer equations that have been presented in the literature. As a result, all modifications that have been presented in a recent series of papers (Elitzur 1991, 1993) to the theory for polarized maser radiation in the presence of a magnetic field are invalid. The basic theory is thus clarified.

  15. Withanolide artifacts formed in methanol.

    PubMed

    Cao, Cong-Mei; Zhang, Huaping; Gallagher, Robert J; Timmermann, Barbara N

    2013-11-22

    Methanol solutions of the main withanolides (6-8) naturally present in Physalis longifolia yielded five artificial withanolides (1-5), including three new compounds (1-3). Withanolides 1 and 2 were identified as intramolecular Michael addition derivatives, while withanolides 3-5 were the result of intermolecular Michael addition. A comprehensive literature investigation was conducted to identify potential withanolide Michael addition artifacts isolated from Solanaceous species to date.

  16. Millimeter wave absorption in the nonhuman primate eye at 35 GHz and 94 GHz.

    PubMed

    Chalfin, Steven; D'Andrea, John A; Comeau, Paul D; Belt, Michael E; Hatcher, Donald J

    2002-07-01

    The purpose of this study was to evaluate anterior segment bioeffects of pulsed 35 GHz and 94 GHz microwave exposure in the nonhuman primate eye. Five juvenile rhesus monkeys (Macaca mulatta) underwent baseline anterior segment ocular assessment consisting of slit lamp examination, corneal topography, specular microscopy, and pachymetry. These studies were repeated after exposure of one eye to pulsed 35 GHz or 94 GHz microwaves at varied fluences, with the other eye serving as a control. The mean fluence required to produce a threshold corneal lesion (faint epithelial edema and fluorescein staining) was 7.5 J cm(-2) at 35 GHz and 5 J cm(-2) at 94 GHz. Transient changes in corneal topography and pachymetry were noted at these fluences. Endothelial cell counts remained unchanged. Threshold corneal injury from 35 GHz and 94 GHz microwave exposure is produced at fluences below those previously reported for CO2 laser radiation. These data may help elucidate the mechanism of thermal injury to the cornea, and resolve discrepancies between IEEE C95.1 (1999), NCRP (1986), and ICNIRP (1998) safety standards for exposure to non-ionizing radiation at millimeter wavelengths.

  17. Studies on methanol - oxidizing yeast. III. Enzyme.

    PubMed

    Volfová, O

    1975-01-01

    Oxidation of methanol, formaldehyde and formic acid was studied in cells and cell-free extract of the yeast Candida boidinii No. 11Bh. Methanol oxidase, an enzyme oxidizing methanol to formaldehyde, was formed inducibly after the addition of methanol to yeast cells. The oxidation of methanol by cell-free extract was dependent on the presence of oxygen and independent of any addition of nicotine-amide nucleotides. Temperature optimum for the oxidation of methanol to formaldehyde was 35 degrees C, pH optimum was 8.5. The Km for methanol was 0.8mM. The cell-free extract exhibited a broad substrate specificity towards primary alcohols (C1--C6). The activity of methanol oxidase was not inhibited by 1mM KCN, EDTA or monoiodoacetic acid. The strongest inhibitory action was exerted by p-chloromercuribenzoate. Both the cells and the cell-free extract contained catalase which participated in the oxidation of methanol to formaldehyde; the enzyme was constitutively formed by the yeast. The pH optimum for the degradation of H2O2 was in the same range as the optimum for methanol oxidation, viz. at 8.5. Catalase was more resistant to high pH than methanol oxidase. The cell-free extract contained also GSH-dependent NAD-formaldehyde dehydrogenase with Km = 0.29mM and NAD-formate dehydrogenase with Km = 55mM. PMID:240764

  18. Cherenkov maser and Cherenkov laser devices. Final report, 10 September 1979-9 September 1982

    SciTech Connect

    Walsh, J.E.

    1982-12-01

    Four documents, which together serve as a review of experimental verification and the theoretical description of stimulated Cherenkov masers, is presented. Multi-hundred kW power levels have been obtained in the longer mm wavelength range and significant power at wavelengths shorter than 1.5 mm have been observed. The relations between resonator dimensions and beam parameters which determine wavelength, gain, and output power, have been established.

  19. Erratum: BeppoSAX Observations of the Maser Seyfert 2 Galaxy ESO 103-G35

    NASA Astrophysics Data System (ADS)

    Wilkes, Belinda J.; Mathur, Smita; Fiore, Fabrizio; Antonelli, Angelo; Nicastro, Fabrizio

    2001-08-01

    In the paper ``BeppoSAX Observations of the Maser Seyfert 2 Galaxy ESO 103-G35'' by Belinda J. Wilkes, Smita Mathur, Fabrizio Fiore, Angelo Antonelli, and Fabrizio Nicastro (ApJ, 549, 248 [2001]), the size of the line-emitting region derived from the line width should read 0.01 pc and not 50 pc as currently listed in the abstract, § 3.4, and § 4.

  20. USSR national time unit keeping over long interval using an ensemble of H-masers

    NASA Technical Reports Server (NTRS)

    Koshelyaevsky, N. B.; Pushkin, S. B.

    1990-01-01

    The U.S.S.R. State Time and Frequency Service (STFS) is discussed. The STFS is responsible for time and frequency measurement unification both in the field of atomic, TA(SU) and UTC(SU) and universal time UT1(SU) over the whole territory of the U.S.S.R. The U.S.S.R. national time unit keeping over long interval using an ensemble of H-masers is also discussed.

  1. Direct methanol fuel cell and system

    DOEpatents

    Wilson, Mahlon S.

    2004-10-26

    A fuel cell having an anode and a cathode and a polymer electrolyte membrane located between anode and cathode gas diffusion backings uses a methanol vapor fuel supply. A permeable polymer electrolyte membrane having a permeability effective to sustain a carbon dioxide flux equivalent to at least 10 mA/cm.sup.2 provides for removal of carbon dioxide produced at the anode by reaction of methanol with water. Another aspect of the present invention includes a superabsorpent polymer material placed in proximity to the anode gas diffusion backing to hold liquid methanol or liquid methanol solution without wetting the anode gas diffusion backing so that methanol vapor from the liquid methanol or liquid methanol-water solution is supplied to the membrane.

  2. THE VELOCITY CENTROID PERIODICITY OF L2 PUPPIS' SiO MASER EMISSION

    SciTech Connect

    McIntosh, Gordon C.; Indermuehle, Balthasar

    2013-09-01

    We report the first short term velocity centroid (VC) periodicity derived from SiO maser emission. L2 Puppis, a semi-regular AGB star, was observed using the Mopra radio telescope of the Australia Telescope National Facility in the SiO v = 1, J = 1-0 and v = 1, J = 2-1 transitions. It exhibits a 139 day period in its SiO maser VC based on a period folding analysis and a Lomb Scargle analysis. L2 Pup's SiO maser emission has an unusually large velocity range and an unusual three-peaked spectrum. To create the change in VC the entire spectrum does not shift in velocity, but changes in the relative emission of the peaks generate the variation. The changes in the VC may be due to differential illumination, an asymmetric circumstellar distribution of material, or a mixture of causes. The unusual velocity structure, similar to that observed in Orion source 1, may be due to revolution of the circumstellar material or asymmetries in the circumstellar environment.

  3. Energetics of the Beamed Zombie Turbulence Maser Action Mechanism for Remote Detection of Submerged Oceanic Turbulence

    NASA Astrophysics Data System (ADS)

    Gibson, C. H.; Bondur, V. G.; Keeler, R. N.; Leung, P. T.

    2011-11-01

    Sea surface brightness spectral anomalies from a Honolulu municipal outfall have been detected from space satellites in 200 km2 areas extending 20 km from the wastewater diffuser (Bondur 2005, Keeler et al. 2005, Gibson et al. 2005). Dropsonde and towed body microstructure measurements show outfall enhanced viscous and temperature dissipation rates above the turbulence trapping layer. Fossil turbulence waves and secondary (zombie, zebra) turbulence waves break as they propagate near-vertically and then break again near the surface to produce wind ripple smoothing in narrow frequency band (zebra) patterns from soliton-like sources of secondary turbulence energy acting on fossils advected from the outfall. The 30-250 m solitons reflect a nonlinear cascade from tidal and current kinetic energy to boundary layer turbulence events, to fossil turbulence waves, to internal soliton and tidal waves. Secondary (zombie) turbulence acts on outfall fossil patches to amplify, channel in chimneys, and vertically beam ambient internal wave energy just as energized metastable molecules around stars amplify and beam quantum frequencies in astrophysical masers. Kilowatts of buoyancy power from the treatment plant produces fossil turbulence patches trapped below the thermocline. Beamed zombie turbulence maser action (BZTMA) in mixing chimneys amplifies these kilowatts into the megawatts of surface turbulence dissipation required to affect brightness on wide sea surface areas by maser action vertical beaming of fossil-wave-power extracted from gigawatts dissipated by intermittent bottom turbulence events on topography from the tides and currents.

  4. The Sizes of 1720 MHZ OH Masers: VLBA and MERLIN Observations of the Supernova Remnants W44 and W28

    NASA Astrophysics Data System (ADS)

    Claussen, M. J.; Goss, W. M.; Frail, D. A.; Desai, K.

    1999-09-01

    We have used the NRAO Very Long Baseline Array (VLBA) to image OH (1720 MHz) masers in the supernova remnants (SNR) W28 and W44 at a resolution of 40 mas. We also used MERLIN to observe the same OH (1720 MHz) masers in W44 at a resolution of 290×165 mas. All the masers are resolved by these VLBA and MERLIN observations. The measured sizes range from 50 to 180 mas and yield brightness temperature estimates from 0.3 to 20×108 K. We investigate whether these measured angular sizes are intrinsic and hence originate as a result of the physical conditions in the supernova remnant shock, or whether they are scatter-broadened sizes produced by the turbulent ionized gas along the line of sight. While the current data on the temporal and angular broadening of pulsars, masers, and extragalactic sources toward W44 and W28 can be understood in terms of scattering, we cannot rule out that these large sizes are intrinsic. Recent theoretical modeling by Lockett, Gauthier, & Elitzur suggests that the physical parameters in the shocked region are indicative of densities and OH abundances that lead to estimates of sizes as large as what we have measured. If the sizes and structure are intrinsic, then the OH (1720 MHz) masers may be more like the OH (1612 MHz) masers in circumstellar shells than OH masers associated with H II regions. At two locations in W28 we observe the classical S-shapes in the Stokes V profiles caused by Zeeman splitting and use it to infer magnetic fields of order 2 mG.

  5. A 30 GHz monolithic receive module

    NASA Technical Reports Server (NTRS)

    Mondal, J.; Contolatis, T.; Geddes, J.; Bauhahn, P.; Sokolov, V.

    1990-01-01

    The technical achievements and deliveries made during the duration of the program to develop a 30 GHz monolithic receive module for communication feed array applications and to deliver submodules and 30 GHz monolithic receive modules for experimental evaluation are discussed. Key requirements include an overall receive module noise figure of 5 dB, a 30 dB RF-to-RF gain with six levels of intermediate gain control, a five bit phase shifter, and a maximum power consumption of 250 mW. In addition, the monolithic receive module design addresses a cost goal of less than one thousand dollars (1980 dollars) per module in unit buys of 5,000 or more, and a mechanical configuration that is applicable to a spaceborne phase array system. An additional task for the development and delivery of 32 GHz phase shifter integrated circuit (IC) for deep space communication is also described.

  6. Two compact preamps cover 38-GHz bandwidth

    NASA Astrophysics Data System (ADS)

    Osbrink, N. K.; Fake, S. R.; Rosenberg, J. C.

    1985-09-01

    The design and performance characteristics of two compact preamplifiers that provide complete coverage of the 2-18 and 18-40 GHz frequency bands are examined. The 2-18-GHz prototype amplifier consists of four stages of thin-film hybrid microwave integrated circuit (MIC) amplification modules each of which incorporates a single GaAs distributed microwave integrated circuit (MMIC). The amplifier weights about 2 ounces and measures 1.75 x 1.15 x 0.67 inches. The 18-40-GHz amplifier consists of five thin-film MIC balanced gain stages and a MIC voltage regulator module with a throughline. The amplifier displays worst-case noise figures of 11.6 dB at the low frequency end of the band and less than 8 dB over much of the band.

  7. 17 GHz High Gradient Accelerator Research

    SciTech Connect

    Temkin, Richard J.; Shapiro, Michael A.

    2013-07-10

    This is a report on the MIT High Gradient Accelerator Research program which has included: Operation of the 17 GHz, 25 MeV MIT/Haimson Research Corp. electron accelerator at MIT, the highest frequency, stand-alone accelerator in the world; collaboration with members of the US High Gradient Collaboration, including the design and test of novel structures at SLAC at 11.4 GHz; the design, construction and testing of photonic bandgap structures, including metallic and dielectric structures; the investigation of the wakefields in novel structures; and the training of the next generation of graduate students and postdoctoral associates in accelerator physics.

  8. 95 GHz Gyrotron with Ferroelectric Cathode

    NASA Astrophysics Data System (ADS)

    Einat, M.; Pilossof, M.; Ben-Moshe, R.; Hirshbein, H.; Borodin, D.

    2012-11-01

    Ferroelectric cathodes were reported as a feasible electron source for microwave tubes. However, due to the surface plasma emission characterizing this cathode, operation of millimeter wave tubes based on it remains questionable. Nevertheless, the interest in compact high power sources of millimeter waves and specifically 95 GHz is continually growing. In this experiment, a ferroelectric cathode is used as an electron source for a gyrotron with the output frequency extended up to 95 GHz. Power above a 5 kW peak and ˜0.5μs pulses are reported; a duty cycle of 10% is estimated to be achievable.

  9. 47 CFR 25.136 - Licensing provisions for user transceivers in the 1.6/2.4 GHz, 1.5/1.6 GHz, and 2 GHz Mobile...

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Footnote 5.353A in 47 CFR 2.106 and the priority and real-time preemption requirements imposed by Footnote... the 1.6/2.4 GHz, 1.5/1.6 GHz, and 2 GHz Mobile-Satellite Services. 25.136 Section 25.136 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE...

  10. Metabolic methanol: molecular pathways and physiological roles.

    PubMed

    Dorokhov, Yuri L; Shindyapina, Anastasia V; Sheshukova, Ekaterina V; Komarova, Tatiana V

    2015-04-01

    Methanol has been historically considered an exogenous product that leads only to pathological changes in the human body when consumed. However, in normal, healthy individuals, methanol and its short-lived oxidized product, formaldehyde, are naturally occurring compounds whose functions and origins have received limited attention. There are several sources of human physiological methanol. Fruits, vegetables, and alcoholic beverages are likely the main sources of exogenous methanol in the healthy human body. Metabolic methanol may occur as a result of fermentation by gut bacteria and metabolic processes involving S-adenosyl methionine. Regardless of its source, low levels of methanol in the body are maintained by physiological and metabolic clearance mechanisms. Although human blood contains small amounts of methanol and formaldehyde, the content of these molecules increases sharply after receiving even methanol-free ethanol, indicating an endogenous source of the metabolic methanol present at low levels in the blood regulated by a cluster of genes. Recent studies of the pathogenesis of neurological disorders indicate metabolic formaldehyde as a putative causative agent. The detection of increased formaldehyde content in the blood of both neurological patients and the elderly indicates the important role of genetic and biochemical mechanisms of maintaining low levels of methanol and formaldehyde.

  11. Design and Operation of an Electrochemical Methanol Concentration Sensor for Direct Methanol Fuel Cell Systems

    NASA Technical Reports Server (NTRS)

    Narayanan, S. R.; Valdez, T. I.; Chun, W.

    2000-01-01

    The development of a 150-Watt packaged power source based on liquid feed direct methanol fuel cells is being pursued currently at the Jet propulsion Laboratory for defense applications. In our studies we find that the concentration of methanol in the fuel circulation loop affects the electrical performance and efficiency the direct methanol fuel cell systems significantly. The practical operation of direct methanol fuel cell systems, therefore, requires accurate monitoring and control of methanol concentration. The present paper reports on the principle and demonstration of an in-house developed electrochemical sensor suitable for direct methanol fuel cell systems.

  12. Recent Studies on Methanol Crossover in Liquid-Feed Direct Methanol Fuel Cells

    NASA Technical Reports Server (NTRS)

    Valdez, T. I.; Narayanan, S. R.

    2000-01-01

    In this work, the effects of methanol crossover and airflow rates on the cathode potential of an operating direct methanol fuel cell are explored. Techniques for quantifying methanol crossover in a fuel cell and for separating the electrical performance of each electrode in a fuel cell are discussed. The effect of methanol concentration on cathode potential has been determined to be significant. The cathode is found to be mass transfer limited when operating on low flow rate air and high concentrations of methanol. Improvements in cathode structure and operation at low methanol concentration have been shown to result in improved cell performance.

  13. Towards a methanol economy based on homogeneous catalysis: methanol to H2 and CO2 to methanol.

    PubMed

    Alberico, E; Nielsen, M

    2015-04-21

    The possibility to implement both the exhaustive dehydrogenation of aqueous methanol to hydrogen and CO2 and the reverse reaction, the hydrogenation of CO2 to methanol and water, may pave the way to a methanol based economy as part of a promising renewable energy system. Recently, homogeneous catalytic systems have been reported which are able to promote either one or the other of the two reactions under mild conditions. Here, we review and discuss these developments.

  14. Accurate positions of SiO masers in active star-forming regions - Orion-KL, W51-IRS2, and Sagittarius-B2 MD5

    NASA Astrophysics Data System (ADS)

    Morita, Koh-Ichiro; Hasegawa, Tetsuo; Ukita, Nobuharu; Okumura, Sachiko K.; Ishiguro, Masato

    1992-08-01

    Accurate positional measurements of SiO J = 1-0 masers in active star-forming regions, Orion-KL, W51-IRS2, and Sgr-B2 MD5, were made with the Nobeyama Millimeter Array. Absolute positional accuracies of 0.12-0.6 arcsec were achieved. The SiO maser in W51-IRS2 is located within 0.4 arcsec (0.5 x 10 exp 17 cm at the distance of W51-IRS2) of the strongest H2O masers. In Sgr-B2 MD5, the SiO maser coincides with the strongest H2O masers, most of the strong OH masers, and the peak of radio continuum emission from the ultracompact H II region within 0.7 arcsec (0.8 x 10 exp 17 cm at the distance of Sgr-B2). Peaks of the emission from hot NH3 were found to exist within about 1 arcsec of the SiO masers in both regions. The precise positional coincidence confirms our former conclusion that the SiO masers in W51-IRS2 and Sgr-B2 MD5 are actually associated with the ongoing activity of star formation, as is the case of Orion-KL.

  15. Propagation handbook, frequencies above 10 GHz

    NASA Astrophysics Data System (ADS)

    Ippolito, Louis J.

    1988-08-01

    The progress and accomplishments in the developmet of the Fourth Edition of the NASA Propagation Effects Handbook for Satellite Systems Design, for frequencies 10 to 100 GHz, NASA Reference Publication 1082(04), dated May 1988, prepared by Westighouse Electric Corporation for the Jet Propulsion Laboratory are discussed.

  16. Propagation handbook, frequencies above 10 GHz

    NASA Technical Reports Server (NTRS)

    Ippolito, Louis J.

    1988-01-01

    The progress and accomplishments in the developmet of the Fourth Edition of the NASA Propagation Effects Handbook for Satellite Systems Design, for frequencies 10 to 100 GHz, NASA Reference Publication 1082(04), dated May 1988, prepared by Westighouse Electric Corporation for the Jet Propulsion Laboratory are discussed.

  17. Methods of conditioning direct methanol fuel cells

    DOEpatents

    Rice, Cynthia; Ren, Xiaoming; Gottesfeld, Shimshon

    2005-11-08

    Methods for conditioning the membrane electrode assembly of a direct methanol fuel cell ("DMFC") are disclosed. In a first method, an electrical current of polarity opposite to that used in a functioning direct methanol fuel cell is passed through the anode surface of the membrane electrode assembly. In a second method, methanol is supplied to an anode surface of the membrane electrode assembly, allowed to cross over the polymer electrolyte membrane of the membrane electrode assembly to a cathode surface of the membrane electrode assembly, and an electrical current of polarity opposite to that in a functioning direct methanol fuel cell is drawn through the membrane electrode assembly, wherein methanol is oxidized at the cathode surface of the membrane electrode assembly while the catalyst on the anode surface is reduced. Surface oxides on the direct methanol fuel cell anode catalyst of the membrane electrode assembly are thereby reduced.

  18. Propane Clathrate Hydrate Formation Accelerated by Methanol.

    PubMed

    Amtawong, Jaruwan; Guo, Jin; Hale, Jared S; Sengupta, Suvrajit; Fleischer, Everly B; Martin, Rachel W; Janda, Kenneth C

    2016-07-01

    The role of methanol as both an inhibitor and a catalyst for the formation of clathrate hydrates (CHs) has been a topic of intense study. We report a new quantitative study of the kinetics of propane CH formation at 253 K from the reaction of propane gas with <75 μm ice particles that have been doped with varying amounts of methanol. We find that methanol significantly accelerates the formation reaction with quite small doping quantities. Even for only 1 methanol molecule per 10 000 water molecules, the maximum uptake rate of propane into CHs is enhanced and the initiation pressure is reduced. These results enable more efficient production of CHs for gas storage. This remarkable acceleration of the CH formation reaction by small quantities of methanol may place constraints on the mechanism of the inhibition effect observed under other conditions, usually employing much larger quantities of methanol. PMID:27275862

  19. A novel process for methanol synthesis

    SciTech Connect

    Tierney, J.W.; Wender, I.

    1992-01-28

    A bench-scale reactor is being used to conduct studies of the conversion of synthesis gas to methanol by a novel process. In previous reports, we provided evidence for a two step reaction in series: the carbonylation of methanol to methyl formate taking place in a non-equilibrium region in the vicinity of the copper chromite surface, and the hydrogenolysis of methyl formate to methanol taking place on the surface of the copper chromite. The synergism between the two catalysts enhances the rate of methanol formation. In this quarter, we tested several copper chromites (with different surface areas and stabilizing agents) on the rate of methanol synthesis. It seems likely that pore diffusion limitations control the hydrogenolysis reaction since the rate of methanol formation is proportional to the square root of the copper chromite surface area. Elemental analyses using Inductively Coupled Plasma analysis and pore size distribution analysis of copper chromite were carried out.

  20. Asymptomatic blood methanol in emergency room patients.

    PubMed

    Wargotz, E S; Werner, M

    1987-06-01

    Over a four-month period, methanol was found in the blood of 18 patients among 687 sequential emergency room admissions screened for alcohols by gas chromatography. In the patients with positive results, blood ethanol ranged from 6 to 570 mg/dL (1.3-123.7 mmol/L), blood methanol from 2.3 to 4.0 mg/dL (0.72-1.25 mmol/L). Methanol exposure during preparation of the sampling site or in the course of specimen handling, ingestion of denatured alcohol, as well as methanol production from the metabolism of aspartame are ruled out as causes for these findings. The authors conclude that endogenous methanol production is the probable major cause, while methanol as a fermentation congener may be a contributory minor cause.

  1. Method of steam reforming methanol to hydrogen

    DOEpatents

    Beshty, Bahjat S.

    1990-01-01

    The production of hydrogen by the catalyzed steam reforming of methanol is accomplished using a reformer of greatly reduced size and cost wherein a mixture of water and methanol is superheated to the gaseous state at temperatures of about 800.degree. to about 1,100.degree. F. and then fed to a reformer in direct contact with the catalyst bed contained therein, whereby the heat for the endothermic steam reforming reaction is derived directly from the superheated steam/methanol mixture.

  2. Air breathing direct methanol fuel cell

    DOEpatents

    Ren, Xiaoming; Gottesfeld, Shimshon

    2002-01-01

    An air breathing direct methanol fuel cell is provided with a membrane electrode assembly, a conductive anode assembly that is permeable to air and directly open to atmospheric air, and a conductive cathode assembly that is permeable to methanol and directly contacting a liquid methanol source. Water loss from the cell is minimized by making the conductive cathode assembly hydrophobic and the conductive anode assembly hydrophilic.

  3. Bioinduced Room-Temperature Methanol Reforming.

    PubMed

    Heim, Leo E; Thiel, Daniel; Gedig, Christian; Deska, Jan; Prechtl, Martin H G

    2015-08-24

    Imitating nature's approach in nucleophile-activated formaldehyde dehydrogenation, air-stable ruthenium complexes proved to be exquisite catalysts for the dehydrogenation of formaldehyde hydrate as well as for the transfer hydrogenation to unsaturated organic substrates at loadings as low as 0.5 mol %. Concatenation of the chemical hydrogen-fixation route with an oxidase-mediated activation of methanol gives an artificial methylotrophic in vitro metabolism providing methanol-derived reduction equivalents for synthetic hydrogenation purposes. Moreover, for the first time methanol reforming at room temperature was achieved on the basis of this bioinduced dehydrogenation path delivering hydrogen gas from aqueous methanol.

  4. Methanol-Resistant Oxygen-Reduction Catalysts for Direct Methanol Fuel Cells

    NASA Astrophysics Data System (ADS)

    Shukla, A. K.; Raman, R. K.

    2003-08-01

    Methanol oxidation in the cathode compartment of the fuel cell, which occurs during the oxygen-reduction reaction on Pt-based cathodes, constitutes a significant performance loss in the direct methanol fuel cells. Over the past decade, four types of methanol-resistant oxygen-reduction catalysts have been developed to circumvent this problem. Among these, transition-metal chalcogenides, and in particular RuSe, have shown effective selectivity to oxygen-reduction reaction in the presence of methanol. These catalysts not only can enhance the performance of the conventional direct methanol fuel cells but also could provide a route to develop mixed-reactants direct methanol fuel cells, which could be highly cost-effective in comparison with the conventional direct methanol fuel cells. This article is a brief update on the preparation, characterization, and implications of methanol-resistant oxygen-reduction catalysts.

  5. Classification of GHZ-type, W-type, and GHZ-W-type multiqubit entanglement

    SciTech Connect

    Chen Lin; Chen Yixin

    2006-12-15

    We propose the concept of SLOCC-equivalent basis in the multiqubit space. In particular, two special SEBs, the Greenberger-Horne-Zeilinger-(GHZ-) type and the W-type basis are introduced. They can make up a more general family of multiqubit states, the GHZ-W-type states, which is a useful kind of entanglement for quantum teleportation and error correction. We completely characterize the property of this type of state, and mainly classify the GHZ-type and the W-type states in a regular way, which is related to the enumerative combinatorics. Many concrete examples are given to exhibit our method of classification. We also propose the condition on which two GHZ-W-type states are interconvertible with probability 1.

  6. Realization of GHZ states and the GHZ test via cavity QED

    NASA Astrophysics Data System (ADS)

    Guerra, E. S.

    2005-09-01

    In this article we discuss the realization of atomic GHZ states involving three-level atoms and we show explicitly how to use this state to perform the GHZ test in which it is possible to decide between local realism theories and quantum mechanics. The experimental realizations proposed make use of the interaction of the Rydberg atoms with a cavity prepared in a coherent state.

  7. Modifications to the relationship between the magnetic field and weak Zeeman features in the spectra of astrophysical masers

    NASA Technical Reports Server (NTRS)

    Nedoluha, Gerald E.; Watson, William D.

    1990-01-01

    Numerical solutions are presented for the equations of radiative transfer for astrophysical masers in a magnetic field to describe the observed weak circular polarization of H2O and SiO masers. Previously unrecognized intensity-dependent effects are found to produce circular polarization which resembles that of the usual Zeeman effect. Astrophysical H2O, SiO, and perhaps other masers are likely to be radiatively saturated with rates for stimulated emission that are within 1-2 orders of magnitude of the Zeeman frequency. Under these conditions, the circular polarization found here tends to be larger (but can be smaller) and may be of opposite sign from that given by the standard treatment for polarized Zeeman spectra.

  8. Comparative study of millimeter wave propagation at 30 GHz and 60 GHz in indoor environment

    NASA Astrophysics Data System (ADS)

    Polydorou, A.; Stratakos, G.; Capsalis, C.; Uzunoglu, N.

    1995-10-01

    The millimeter wave band appears to be a favourable choice for personal wireless communication systems for indoor environment, as it meets the requirements for sufficient bandwidth, small terminal dimensions and sporadic usage for commercial applications. In this paper measurements of millimeter wave propagation in both 30 GHz and 60 GHz bands, are presented in a comparative way. The topology of measurements covers both a line-of-sight situation and also a case where a direct path between transmitter and receiver does not exist. Although the second case does not seem obvious for outdoor applications in these frequencies, in indoor environment the multipath signals produced by objects like walls, doors, furniture etc., can be utilised in order to overcome the man-made shadowing. Both slow and fast fading characteristics of the received signal are studied and the measurements are modelled by the conventional Rician and Rayleigh distributions. Both frequency bands offer advantages for usage in in-house wireless communication systems. Although in 30 GHz band the coverage area is bigger than in 60 GHz (with the same transmitting power), frequency reuse is easier in 60 GHz band. because even if millimeter waves ‘escape’ through ‘windows’, the specific attenuation due to atmospheric oxygen (15 dB/km) at 60 GHz eliminates the interference between communication channels in neighbouring buildings.

  9. Biogeochemical Cycle of Methanol in Anoxic Deep-Sea Sediments

    PubMed Central

    Yanagawa, Katsunori; Tani, Atsushi; Yamamoto, Naoya; Hachikubo, Akihiro; Kano, Akihiro; Matsumoto, Ryo; Suzuki, Yohey

    2016-01-01

    The biological flux and lifetime of methanol in anoxic marine sediments are largely unknown. We herein reported, for the first time, quantitative methanol removal rates in subsurface sediments. Anaerobic incubation experiments with radiotracers showed high rates of microbial methanol consumption. Notably, methanol oxidation to CO2 surpassed methanol assimilation and methanogenesis from CO2/H2 and methanol. Nevertheless, a significant decrease in methanol was not observed after the incubation, and this was attributed to the microbial production of methanol in parallel with its consumption. These results suggest that microbial reactions play an important role in the sources and sinks of methanol in subseafloor sediments. PMID:27301420

  10. Identification of oxygen-rich evolved stars by maser surveys and statistical studies on infrared data

    NASA Astrophysics Data System (ADS)

    Yung, Bosco H.-K.

    2013-10-01

    The post-asymptotic giant branch (post-AGB) phase is a short episode in the life of a star with mass between 0.8 to 8 M⊙. It comes after the AGB phase, and before the planetary nebula phase. A rapid change in many physical properties of a star is suggested to happen in this phase, for example the onset of jets. However, a lot of details are still unknown. In this thesis, three major problems are addressed: insufficient samples of post-AGB stars, identification of post-AGB stars, and the true status of a special class of objects called the "water fountains (WFs)". WFs are evolved stars associated with high velocity collimated bipolar jets that can be traced by H2O maser emissions. For the first two problems, new searching criteria are introduced with two new maser surveys on oxygen-rich post-AGB stars. It is necessary to collect more samples of post-AGB stars for further studies. Nonetheless, there has been no systematic searching method because most of the post-AGB stars are dim in optical and near-infrared wavelengths, which increases the difficulty in identification. Maser thus becomes a good alternative tool. In the first survey which focused only on H2O masers, over 200 AGB or post-AGB star candidates have been selected and observed. Those candidates were mainly chosen by new colour criteria with the far-infrared AKARI data. In particular, four characteristic maser sources were found, and they are currently suggested as possible very young post-AGB stars. In the second survey, another 100 objects were observed in OH and/or H2O masers. Three possible high velocity objects were discovered, including a new rare member of WFs. The colour criteria are proved to be quite sensitive in distinguishing post-AGB stars from AGB stars or other types of objects, even though there are still some contamination from young stellar objects. A follow-up study shows that the Q-parameters are effective in isolating objects with spherical or aspherical envelopes, which are also

  11. 47 CFR 15.251 - Operation within the bands 2.9-3.26 GHz, 3.267-3.332 GHz, 3.339-3.3458 GHz, and 3.358-3.6 GHz.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 1 2012-10-01 2012-10-01 false Operation within the bands 2.9-3.26 GHz, 3.267..., Additional Provisions § 15.251 Operation within the bands 2.9-3.26 GHz, 3.267-3.332 GHz, 3.339-3.3458 GHz... spectrum analyzer or equivalent measuring receiver; (2) The angular separation between the direction...

  12. 47 CFR 15.251 - Operation within the bands 2.9-3.26 GHz, 3.267-3.332 GHz, 3.339-3.3458 GHz, and 3.358-3.6 GHz.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Operation within the bands 2.9-3.26 GHz, 3.267..., Additional Provisions § 15.251 Operation within the bands 2.9-3.26 GHz, 3.267-3.332 GHz, 3.339-3.3458 GHz... spectrum analyzer or equivalent measuring receiver; (2) The angular separation between the direction...

  13. Linearly polarized radiation from astrophysical masers due to magnetic fields when the rate for stimulated emission exceeds the Zeeman frequency

    NASA Technical Reports Server (NTRS)

    Deguchi, Shuji; Watson, William D.

    1990-01-01

    The results are presented of reformulating the treatment of polarized maser radiation in the presence of magnetic fields in a way that seems somewhat more convenient for calculations with masing states having angular momenta greater than J = 1 and 0. Calculations are then performed for the case of small Zeeman splitting using idealizations which are equivalant to those made previously in calculations for a J = 1-0 transition. The results provide a complete, general description of the polarization characteristics of astrophysical maser radiation involving states of higher angular momentum of closed-shell molecules.

  14. OH Masers from Andromeda to the Peak of Cosmic Star Formation

    NASA Astrophysics Data System (ADS)

    Willett, Kyle

    2011-01-01

    OH masers are well-known astronomical phenomena in which 18-cm radiation is amplified through the process of stimulated emission. My dissertation research focuses on the study of OH masers in multiple environments. The first portion is a Spitzer spectroscopic study of OH megamaser host galaxies. Several infrared properties of the host galaxy are shown to strongly correlate with the presence of an OH megamaser. These requirements include a smooth, optically thick dust environment and dust temperatures of 40-100 K in the circumnuclear region. I also demonstrate that the presence of an AGN highly selects against the presence of a megamaser - OHM hosts are dominated by starburst galaxies. I also use combined radio and IR data to make the first detailed test of an OH pumping model using the global parameters of the host galaxies. Based on our analysis, current models must be updated to include much higher optical depths and a variety of dust geometries. Secondly, I describe results from a new high-redshift search for OH megamasers using the Green Bank Telescope. The combination of new OHM detections and upper limits are used to construct an expanded OH luminosity function. Since the presence of an OHM traces both merging galaxies and extreme star formation, megamasers can serve as a powerful probe of galaxy evolution across cosmic time. The discovery of OHMs at z 1 is crucial for achieving this goal. Finally, I describe results of a new and complete OH survey of the Andromeda galaxy (M31). The goal of this survey is to find masers that can be used to measure M31's proper motion, which is as yet unknown. Any constraints on this will significantly impact our understanding of the Local Group's dynamics, history, and future evolution.

  15. Laboratory Modeling of Spike-like Operation of Magnetospheric Cyclotron Masers

    NASA Astrophysics Data System (ADS)

    Golubev, S. V.; Razin, S. V.; Zorin, V. G.; Vodopyanov, A. V.; Mansfeld, D. A.; Demekhov, A. G.; Trakhtengerts, V. Y.

    We present a study of pulsating regimes of whistler cyclotron instability in a labora- tory magnetic mirror trap. This study is aimed at searching common and specific fea- tures of spike-like regimes of magnetospheric and laboratory cyclotron masers. The plasma with hot-electron population is produced in the trap by the ECR discharge. The energetic electrons with anisotropic velocity distribution have energies of about 5 to 100 keV. Quasi-periodic spikes of precipitated energetic electrons are detected by the current pulses produced by these electrons hitting semiconductor detectors (pin-diodes) at the ends of the trap. Associated with these spikes is the electromagnetic emission propagating quasi-parallel to the magnetic field. The emission spectrum is bounded from above by the frequency which is below the electron gyrofrequency in the central cross-section of the trap. Precipitation of energetic electrons is found to be quasi- uniform across the trap. These and other features allow us to identify the electron precipitation mechanism as the turbulent diffusion at whistler-mode waves generated by the cyclotron instability of the energetic electrons. We study the dynamics of pulsating regime as dependent on the ambient gas pres- sure, power of the heating pulse, mirror ratio, and the position of the gyroresonance level for the heating radiation with respect to the trap center. Several mechanisms of spike formation are considered. In particular, we discuss the role of wave reflection at the ends of the plasma column, the heating of the background plasma by the excited radiation, and nonlinear modification of the hot-electron distribution function. We found that the spike-like regimes of precipitation observed in the laboratory trap are generally consistent with the theory of cyclotron masers and can have much in common with similar regimes in space cyclotron masers, in particular, in magneto- spheric radiation belts and solar flare loops.

  16. 47 CFR 101.525 - 24 GHz system operations.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false 24 GHz system operations. 101.525 Section 101.525 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES 24 GHz Service and Digital Electronic Message Service § 101.525 24 GHz...

  17. 47 CFR 101.525 - 24 GHz system operations.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false 24 GHz system operations. 101.525 Section 101.525 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES 24 GHz Service and Digital Electronic Message Service § 101.525 24 GHz...

  18. 77 FR 45503 - 4.9 GHz Band

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-01

    ... errors in these provisions. These changes affecting the 4.9 GHz band in particular will improve spectrum... GHz Band AGENCY: Federal Communications Commission. ACTION: Final rule. SUMMARY: The Commission adopts...-4990 MHz (4.9 GHz) band applicants from certified frequency coordination. Next, the Commission...

  19. Multiple teleportation via partially entangled GHZ state

    NASA Astrophysics Data System (ADS)

    Xiong, Pei-Ying; Yu, Xu-Tao; Zhan, Hai-Tao; Zhang, Zai-Chen

    2016-08-01

    Quantum teleportation is important for quantum communication. We propose a protocol that uses a partially entangled Greenberger-Horne-Zeilinger (GHZ) state for single hop teleportation. Quantum teleportation will succeed if the sender makes a Bell state measurement, and the receiver performs the Hadamard gate operation, applies appropriate Pauli operators, introduces an auxiliary particle, and applies the corresponding unitary matrix to recover the transmitted state.We also present a protocol to realize multiple teleportation of partially entangled GHZ state without an auxiliary particle. We show that the success probability of the teleportation is always 0 when the number of teleportations is odd. In order to improve the success probability of a multihop, we introduce the method used in our single hop teleportation, thus proposing a multiple teleportation protocol using auxiliary particles and a unitary matrix. The final success probability is shown to be improved significantly for the method without auxiliary particles for both an odd or even number of teleportations.

  20. SEVENTH HARMONIC 20 GHz CO-GENERATOR

    SciTech Connect

    Hirshfield, Jay L

    2014-04-08

    To satisfy the need for multi-MW rf sources in frequency ranges where commercial sources do not exist, a study was undertaken on a class of devices based on gyro-harmonic frequency multiplication. This mechanism relies upon adding energy in gyrating motion to a linear electron beam that traverses a rotating-mode TE111-mode drive cavity in a dc magnetic field. The beam then drifts along the magnetic field into a second cavity, operating in the TEn11-mode tuned to the nth harmonic of the drive cavity. Studies of this configuration have been carried out for 2 < n < 7. Results are given for multi-MW, efficient operation of a 7th harmonic device operating at 20 GHz, and a 2nd harmonic device operating at 22.4 GHz.

  1. Tree attenuation at 20 GHz: Foliage effects

    NASA Technical Reports Server (NTRS)

    Vogel, Wolfhard J.; Goldhirsh, Julius

    1993-01-01

    Static tree attenuation measurements at 20 GHz (K-Band) on a 30 deg slant path through a mature Pecan tree with and without leaves showed median fades exceeding approximately 23 dB and 7 dB, respectively. The corresponding 1% probability fades were 43 dB and 25 dB. Previous 1.6 GHz (L-Band) measurements for the bare tree case showed fades larger than those at K-Band by 3.4 dB for the median and smaller by approximately 7 dB at the 1% probability. While the presence of foliage had only a small effect on fading at L-Band (approximately 1 dB additional for the median to 1% probability range), the attenuation increase was significant at K-Band, where it increased by about 17 dB over the same probability range.

  2. Developmental and Reproductive Toxicology of Methanol

    EPA Science Inventory

    Methanol is a high production volume chemical used as a feedstock for chemical syntheses and as a solvent and fuel additive. Methanol is acutely toxic to humans, causing acidosis, blindness in death at high dosages, but its developmental and reproductive toxicity in humans is poo...

  3. Methanol Steam Reforming for Hydrogen Production

    SciTech Connect

    Palo, Daniel R.; Dagle, Robert A.; Holladay, Jamie D.

    2007-09-11

    Review article covering developments in methanol steam reforming in the context of PEM fuel cell power systems. Subjects covered include methanol background, use, and production, comparison to other fuels, power system considerations, militrary requirements, competing technologies, catalyst development, and reactor and system development and demonstration.

  4. Effect of electron-beam momentum spread on cyclotron resonance maser operation at two resonant frequencies

    NASA Astrophysics Data System (ADS)

    Hunter, G. J.; McNeil, B. W. J.; Robb, G. R. M.

    2001-09-01

    We present a theoretical analysis of cyclotron resonance maser (CRM) operation at two resonant frequencies including the effects of momentum spread in the electron beam. A linear analysis of the system equations is presented in the limit of small momentum spreads. Numerical solutions to the system equations are also given and are in agreement with the linear theory. The results predict that for realistic momentum spreads, operation of the CRM at the higher of the two resonant frequencies should be possible, extending its operating frequency range. An experiment currently under development at Strathclyde University is described and modeled numerically.

  5. Co-axial Ka-band Free Electron Maser Using Two-dimensional Feedback

    SciTech Connect

    Phelps, A. D. R.; Konoplev, I. V.; McGrane, P.; Cross, A. W.; He, W.; Whyte, C. G.; Ronald, K.; Thumm, M. K.; Ginzburg, N. S.; Peskov, N. Yu.; Sergeev, A. S.

    2006-01-03

    The first successful experimental studies of microwave radiation from a co-axial Free-Electron Maser (FEM) based on two-dimensional (2D) distributed feedback have been recently conducted. This paper contains a description of the experimental set-up and the results obtained. The high-power pulsed power supply and high-current accelerator (HCA) developed and used to drive the FEM are discussed. The results of the experimental study of the FEM operating in the Ka frequency band are presented and compared with theoretical predictions.

  6. Upper limits on the cosmological gravitational wave background and maser clocks in space

    NASA Astrophysics Data System (ADS)

    Polnarev, A. G.; Roxburgh, I. W.

    1995-04-01

    We consider the possibility of detecting gravitational waves through the measurement of a time varying phase shift using a hydrogen maser clock on a satellite. Such measurements enable us to put interesting upper limits on the contribution of the gravitational-wave background to the dimensionless density of the Universe. The requirements on residual accelerations and the sensitivity of an accelerometer on the spacecraft are shown to be realistic and could be achieved using the accelerometer technology developed by ONERA for the ARISTOTELES mission. Such an experiment placing upper limits on the cosmological gravitational wave background could be conducted using the proposed Russian satellite “Millimetron”.

  7. Enhancing the efficiency of slow-wave electron cyclotron masers with the tapered refractive index

    SciTech Connect

    Kong Lingbao; Hou Zhiling; Jing Jian; Jin Haibo; Du Chaohai

    2013-04-15

    The nonlinear analysis of slow-wave electron cyclotron masers (ECM) based on anomalous Doppler effect in a slab waveguide is presented. A method of tapered refractive index (TRI) is proposed to enhance the efficiency of slow-wave ECM. The numerical calculations show that the TRI method can significantly enhance the efficiency of slow-wave ECM with the frequency ranging from the microwave to terahertz band. The effect of beam velocity spread on the efficiency has also been studied. Although the velocity spread suppresses the efficiency significantly, a great enhancement of efficiency can still be introduced by the TRI method.

  8. The 1- to 4-K refrigeration techniques for cooling masers on a beam waveguide antenna

    NASA Technical Reports Server (NTRS)

    Johnson, D. L.

    1986-01-01

    The status of technology is reported for various 1- to 4-K commercially available refrigeration systems capable of producing 1.5-K refrigeration to cool masers and superconducting cavity oscillators on the proposed beam waveguide antenna. The design requirements for the refrigeration system and the cryostat are presented. A continuously operating evaporation refrigerator that uses capillary tubing to provide a continuous, self-regulating flow of helium at approximately 1.5 K has been selected as the first refrigerator design for the beam waveguide antenna.

  9. A kinetic cyclotron maser instability associated with a hollow beam of electrons

    NASA Technical Reports Server (NTRS)

    Wu, C. S.; Freund, H. P.

    1984-01-01

    A kinetic cyclotron maser instability associated with a hollow-beam distribution function is studied. The instability differs from that discussed for the gyrotron device in two respects: in the present case the momentum dispersion is substantial, and furthermore there exists a low-energy background plasma. On the basis of physical arguments it can be demonstrated that the hollow-beam distribution is far more unstable than the loss cone distribution which has been extensively investigated in recent years. A criterion for maximum growth rate is established on the basis of consideration of the resonance ellipse. The validity of this criterion is supported by the results of numerical calculation.

  10. Three dimensional nonlinear analysis of a single-grating rectangular waveguide Cerenkov maser

    SciTech Connect

    Xie, Wenqiu; Wang, Zi-Cheng; Luo, Jirun; Zhao, Ding

    2015-04-15

    A three dimensional (3-D) nonlinear model for illustrating the beam-wave interaction in a single-grating rectangular waveguide sheet-beam Cerenkov maser is presented. The dynamical equations and the equations of motion are solved self-consistently to predict the device performance. Space-charge effects and Ohmic losses are considered in the model. A 1.03 THz backward wave oscillator and a 0.65 THz traveling wave tube are discussed as two illustrative examples.

  11. VLBI survey at 2. 29 GHz

    SciTech Connect

    Preston, R.A.; Morabito, D.D.; Williams, J.G.; Faulkner, J.; Jauncey, D.L.

    1985-09-01

    VLBI observations at 2.29 GHz with fringe spacings of about 3 milliarcsec have been performed on 1398 radio sources spread over the entire sky. 917 sources were detected, including 93 percent of the identified BL Lacertae objects, 86 percent of the quasars, and 36 percent of the galaxies. The resulting catalog of compact radio sources is useful for various astrophysical studies and in the formation of VLBI celestial reference frames. 252 references.

  12. Australia 31-GHz brightness temperature exceedance statistics

    NASA Technical Reports Server (NTRS)

    Gary, B. L.

    1988-01-01

    Water vapor radiometer measurements were made at DSS 43 during an 18 month period. Brightness temperatures at 31 GHz were subjected to a statistical analysis which included correction for the effects of occasional water on the radiometer radome. An exceedance plot was constructed, and the 1 percent exceedance statistics occurs at 120 K. The 5 percent exceedance statistics occurs at 70 K, compared with 75 K in Spain. These values are valid for all of the three month groupings that were studied.

  13. The 30-GHz monolithic receive module

    NASA Technical Reports Server (NTRS)

    Sokolov, V.; Geddes, J.; Bauhahn, P.

    1983-01-01

    Key requirements for a 30 GHz GaAs monolithic receive module for spaceborne communication antenna feed array applications include an overall receive module noise figure of 5 dB, a 30 dB RF to IF gain with six levels of intermediate gain control, a five-bit phase shifter, and a maximum power consumption of 250 mW. The RF designs for each of the four submodules (low noise amplifier, some gain control, phase shifter, and RF to IF sub-module) are presented. Except for the phase shifter, high frequency, low noise FETs with sub-half micron gate lengths are employed in the submodules. For the gain control, a two stage dual gate FET amplifier is used. The phase shifter is of the passive switched line type and consists of 5-bits. It uses relatively large gate width FETs (with zero drain to source bias) as the switching elements. A 20 GHz local oscillator buffer amplifier, a FET compatible balanced mixer, and a 5-8 GHz IF amplifier constitute the RF/IF sub-module. Phase shifter fabrication using ion implantation and a self-aligned gate technique is described. Preliminary RF results obtained on such phase shifters are included.

  14. The 60 GHz IMPATT diode development

    NASA Technical Reports Server (NTRS)

    Dat, Rovindra; Ayyagari, Murthy; Hoag, David; Sloat, David; Anand, Yogi; Whitely, Stan

    1986-01-01

    The objective is to develop 60 GHz IMPATT diodes suitable for communications applications. The performance goals of the 60 GHz IMPATT is 1W CW output power with a conversion efficiency of 15 percent and 10-year lifetime. The final design of the 60 GHz IMPATT structure evolved from computer simulations performed at the University of Michigan. The initial doping profile, involving a hybrid double-drift (HDD) design, was derived from a drift-diffusion model that used the static velocity-field characteristics for GaAs. Unfortunately, the model did not consider the effects of velocity undershoot and delay of the avalanche process due to energy relaxation. Consequently, the initial devices were oscillating at a much lower frequency than anticipated. With a revised simulation program that included the two effects given above, a second HDD profile was generated and was used as a basis for fabrication efforts. In the area of device fabrication, significant progress was made in epitaxial growth and characterization, wafer processing, and die assembly. The organo-metallic chemical vapor deposition (OMCVD) was used. Starting with a baseline X-Band IMPATT technology, appropriate processing steps were modified to satisfy the device requirements at V-Band. In terms of efficiency and reliability, the device requirements dictate a reduction in its series resistance and thermal resistance values. Qualitatively, researchers were able to reduce the diodes' series resistance by reducing the thickness of the N+ GaAs substrate used in its fabrication.

  15. Deuterated methanol in the pre-stellar core L1544

    NASA Astrophysics Data System (ADS)

    Bizzocchi, L.; Caselli, P.; Spezzano, S.; Leonardo, E.

    2014-09-01

    Context. High methanol (CH3OH) deuteration has been revealed in Class 0 protostars with the detection of singly, doubly, and even triply D-substituted forms. Methanol is believed to form during the pre-collapse phase via gas-grain chemistry and then eventually injected into the gas when the heating produced by the newly formed protostar sublimates the grain mantles. The molecular deuterium fraction of the warm gas is thus a relic of the cold pre-stellar era and provides hints of the past history of the protostars. Aims: Pre-stellar cores represent the preceding stages in the process of star formation. We aim at measuring methanol deuteration in L1544, a prototypical dense and cold core on the verge of gravitational collapse. The aim is to probe the deuterium fractionation process while the "frozen" molecular reservoir is accumulated onto dust grains. Methods: Using the IRAM 30 m telescope, we mapped the methanol emission in the pre-stellar core L1544 and observed singly deuterated methanol (CH2DOH and CH3OD) towards the dust peak of L1544. Non-LTE radiative transfer modelling was performed on three CH3OH emissions lines at 96.7 GHz, using a Bonnor-Ebert sphere as a model for the source. We have also assumed a centrally decreasing abundance profile to take the molecule freeze-out in the inner core into account. The column density of CH2DOH was derived assuming LTE excitation and optically thin emission. Results: The CH3OH emission has a highly asymmetric morphology, resembling a non-uniform ring surrounding the dust peak, where CO is mainly frozen onto dust grains. The observations provide an accurate measure of methanol deuteration in the cold pre-stellar gas. The derived abundance ratio is [CH2DOH]/[CH3OH] = 0.10 ± 0.03, which is significantly smaller than the ones found in low-mass Class 0 protostars and smaller than the deuterium fraction measured in other molecules towards L1544. The singly-deuterated form CH3OD was not detected at 3σ sensitivity of 7 mK km s

  16. Recent Results on the Accurate Measurements of the Dielectric Constant of Seawater at 1.413GHZ

    NASA Technical Reports Server (NTRS)

    Lang, R.H.; Tarkocin, Y.; Utku, C.; Le Vine, D.M.

    2008-01-01

    Measurements of the complex. dielectric constant of seawater at 30.00 psu, 35.00 psu and 38.27 psu over the temperature range from 5 C to 3 5 at 1.413 GHz are given and compared with the Klein-Swift results. A resonant cavity technique is used. The calibration constant used in the cavity perturbation formulas is determined experimentally using methanol and ethanediol (ethylene glycol) as reference liquids. Analysis of the data shows that the measurements are accurate to better than 1.0% in almost all cases studied.

  17. A comparison of the velocity parameters of SiO V = 1, J = 1 − 0, and J = 2 − 1 maser emission in semiregular variables

    SciTech Connect

    McIntosh, Gordon; Indermuehle, Balthasar E-mail: balt.indermuehle@csiro.au

    2015-03-01

    We have determined and compared the SiO maser velocity parameters of semiregular variables in the v = 1, J = 1 − 0 (J10{sup 1}) and the v = 1, J = 2 − 1 (J21) transitions. Fourteen sources in the Mopra SiO Maser Catalogue are classified as semiregular variables of types SR, SRa, SRb, or SRc. (L2 Puppis, an SRa star with an unusual SiO maser spectrum, has been analyzed individually.) We have previously presented the overall and phase dependent velocity parameters of SiO masers associated with long period variables (LPVs) of well-established periods and maxima. A comparison of the velocity centroid (VC) difference, VC21–VC10, shows mixed results for the variable types. Some differences are negative and some positive. The SRc difference is negative, large, and relatively stable. The SRb difference has the widest distribution. The velocity ranges (VRs) of the maser emission have been compared using arithmetic averages, Gaussian fits to the distributions, and Weibull fits to the distributions. For LPVs, SRs, SRas, and SRcs the VR10 is one to a few km s{sup −1} greater than the VR21. SRcs have the largest VRs by a factor of two or three indicating the greater range over which the conditions necessary for masers to originate exist in these supergiant stars. SRbs are the only classification of semiregular variable in which the VR21 exceeds the VR10. The larger VR21 compared to VR10 for SRbs appears in all comparisons. The difference in the SRb SiO maser velocity parameters may be due to a difference in the oscillation mechanism of the star. The suggested overtone oscillations of SRbs may affect the circumstellar cloud dynamics. Little theoretical work has specifically addressed the masers in semiregular variables. Qualitative comparisons of the data with the existing models of the SiO masers in LPVs are made.

  18. Galactic rotation curve and spiral density wave parameters from 73 masers

    NASA Astrophysics Data System (ADS)

    Bobylev, V. V.; Bajkova, A. T.

    2013-12-01

    Based on kinematic data on masers with known trigonometric parallaxes and measurements of the velocities of HI clouds at tangential points in the inner Galaxy, we have refined the parameters of the Allen-Santillan model Galactic potential and constructed the Galactic rotation curve in a wide range of Galactocentric distances, from 0 to 20 kpc. The circular rotation velocity of the Sun for the adopted Galactocentric distance R 0 = 8 kpc is V 0 = 239 ± 16 km s-1. We have obtained the series of residual tangential, Δ V θ , and radial, V R , velocities for 73 masers. Based on these series, we have determined the parameters of the Galactic spiral density wave satisfying the linear Lin-Shu model using the method of periodogram analysis that we proposed previously. The tangential and radial perturbation amplitudes are f θ = 7.0±1.2 km s-1 and f R = 7.8±0.7 km s-1, respectively, the perturbation wave length is λ = 2.3±0.4 kpc, and the pitch angle of the spiral pattern in a two-armed model is i = -5.2° ±0.7°. The phase of the Sun ζ ⊙ in the spiral density wave is -50° ± 15° and -160° ± 15° from the residual tangential and radial velocities, respectively.

  19. Mid Infrared Hydrogen Recombination Line Emission from the Maser Star MWC 349A

    NASA Technical Reports Server (NTRS)

    Smith, Howard A.; Strelnitski, V.; Miles, J. W.; Kelly, D. M.; Lacy, J. H.

    1997-01-01

    We have detected and spectrally resolved the mid-IR hydrogen recombination lines H6(alpha)(12.372 micrometers), H7(alpha)(19.062 micrometers), H7(beta)(l1.309 micrometers) and H8(gamma)(12.385 micrometers) from the star MWC349A. This object has strong hydrogen maser emission (reported in the millimeter and submillimeter hydrogen recombination lines from H36(alpha) to H21(alpha)) and laser emission (reported in the H15(alpha), H12(alpha) and H10(alpha) lines). The lasers/masers are thought to arise predominantly in a Keplerian disk around the star. The mid-IR lines do not show evident signs of lasing, and can be well modeled as arising from the strong stellar wind, with a component arising from a quasi-static atmosphere around the disk, similar to what is hypothesized for the near IR (less than or equal to 4 micrometers) recombination lines. Since populations inversions in the levels producing these mid-IR transitions are expected at densities up to approximately 10(exp 11)/cu cm, these results imply either that the disk does not contain high-density ionized gas over long enough path lengths to produce a gain approximately 1, and/or that any laser emission from such regions is small compared to the spontaneous background emission from the rest of the source as observed with a large beam. The results reinforce the interpretation of the far-IR lines as true lasers.

  20. Estudio de Maseres Circunestelares de Monoxido de Silicio con muy alta Resolucion Espacial

    NASA Astrophysics Data System (ADS)

    Soria-Ruiz, Rebeca

    2006-03-01

    We present high-spatial and high-spectral resolution studies of SiO masers in the circumstellar envelopes of late-type stars. These masers occur in the inner layers of the CSEs, in a region dominated by the stellar pulsation, thus being good (if not the only) probes available to understand the physics in these regions. Using the NRAO Very Long Baseline Array, we have produced maps of the 28SiO v=1 and v=2 J=1-0 and J=2-1 transitions towards several AGB stars: two Mira-type (TXCam and RLeo), one OH/IR (IRC+10011) and one S-type (xCyg) stars. The 29SiO v=0 J=1-0 and J=2-1 emission has also been studied. The spatial distributions retrieved, some of them for the first time, are in clear contradiction with the predictions of the models developed to date. We suggest that spectral line overlap may explain the results obtained. This work has been conducted by Dr. Javier Alcolea Jimenez and Dr. Francisco Colomer Sanmartin, at Observatorio Astronomico Nacional (Spain). The PhD thesis manuscript, in spanish, is available at ftp://ftp.oan.es/pub/users/r.soria/TESIS-RSoria.pdf .

  1. OH satellite-line masers in the nucleus of NGC 253

    NASA Astrophysics Data System (ADS)

    Frayer, D. T.; Seaquist, E. R.; Frail, D. A.

    1998-02-01

    We report the detection of 1720 and 1612 MHz OH ground-state satellite-line maser regions in the starburst galaxy NGC 253. We find 10 compact maser features, all of which are located along the narrow ridge of bright radio continuum emission within the central 10 sq arcsec of the nucleus. The compact OH features appear physically associated with regions of dense molecular gas, supernova remnants, and H II regions. The data for several of the features are consistent with collisional inversion from the interaction of supernova remnant shocks with molecular gas, similar to that found for Galactic supernova remnants by Frail et al. (1994, 1996). For many other features near the nucleus of NGC 253, we find conjugate behavior in the 1720 and 1612 MHz lines, with one line showing stimulated emission and the other showing stimulated absorption. These results suggest the importance of infrared pumping associated with the active star formation in NGC 253 and are consistent with large column densities of molecular gas.

  2. Engineering Escherichia coli for methanol conversion.

    PubMed

    Müller, Jonas E N; Meyer, Fabian; Litsanov, Boris; Kiefer, Patrick; Potthoff, Eva; Heux, Stéphanie; Quax, Wim J; Wendisch, Volker F; Brautaset, Trygve; Portais, Jean-Charles; Vorholt, Julia A

    2015-03-01

    Methylotrophic bacteria utilize methanol and other reduced one-carbon compounds as their sole source of carbon and energy. For this purpose, these bacteria evolved a number of specialized enzymes and pathways. Here, we used a synthetic biology approach to select and introduce a set of "methylotrophy genes" into Escherichia coli based on in silico considerations and flux balance analysis to enable methanol dissimilation and assimilation. We determined that the most promising approach allowing the utilization of methanol was the implementation of NAD-dependent methanol dehydrogenase and the establishment of the ribulose monophosphate cycle by expressing the genes for hexulose-6-phosphate synthase (Hps) and 6-phospho-3-hexuloisomerase (Phi). To test for the best-performing enzymes in the heterologous host, a number of enzyme candidates from different donor organisms were selected and systematically analyzed for their in vitro and in vivo activities in E. coli. Among these, Mdh2, Hps and Phi originating from Bacillus methanolicus were found to be the most effective. Labeling experiments using (13)C methanol with E. coli producing these enzymes showed up to 40% incorporation of methanol into central metabolites. The presence of the endogenous glutathione-dependent formaldehyde oxidation pathway of E. coli did not adversely affect the methanol conversion rate. Taken together, the results of this study represent a major advancement towards establishing synthetic methylotrophs by gene transfer.

  3. A 75-116-Ghz LNA with 23-K Noise Temperature at 108 Ghz

    NASA Technical Reports Server (NTRS)

    Varonen, Mikko; Reeves, Rodrigo; Kangaslahti, Pekka; Samoska, Lorene; Cleary, Kieran; Gawande, Rohit; Fung, Andy; Gaier, Todd; Weinreb, Sander; Readhead, Anthony C. S.; Sarkozy, Stephen; Lai, Richard

    2013-01-01

    In this paper we present the design and measurement results, both on-wafer and in package, of an ultra-low-noise and wideband monolithic microwave integrated circuit (MMIC) amplifier in the frequency range of 75 to 116 GHz. The three-stage amplifier packaged in a WR10 waveguide housing and fabricated using a 35-nm InP HEMT technology achieves a record noise temperature of 23 K at 108 GHz when cryogenically cooled to 27 K. The measured gain is 22 to 27 dB for frequency range of 75 to 116 GHz. Furthermore, the amplifier utilizes four finger devices with total gate width of 60 um resulting for improved linearity.

  4. Spacecraft mass trade-offs versus radio-frequency power and antenna size at 8 GHz and 32 GHz

    NASA Technical Reports Server (NTRS)

    Gilchriest, C. E.

    1987-01-01

    The purpose of this analysis is to help determine the relative merits of 32 GHz over 8 GHz for future deep space communications. This analysis is only a piece of the overall analysis and only considers the downlink communication mass, power, and size comparisons for 8 and 32 GHz. Both parabolic antennas and flat-plate arrays are considered. The Mars Sample Return mission is considered in some detail as an example of the tradeoffs involved; for this mission the mass, power, and size show a definite advantage of roughly 2:1 in using the 32 GHz over 8 GHz.

  5. Formation of GPS-Linked Global Ensemble of Hydrogen Masers, and Comparison to JPL's Linear Ion Trap

    NASA Technical Reports Server (NTRS)

    Young, L. E.; Jefferson, D. C.; Lichten, S. M.; Tjoelker, R. L.; Maleki, L.

    1996-01-01

    This paper will describe the use of precision GPS time transfer to form an ensemble of hydrogen maser clocks. The performance of this ensemble, including the GPS time-transfer system, was measured relative to a stable Linear Ion Trap Standard.

  6. Unravelling the Structure of Aspherical Protoplanetary Nebulae I. HST Imaging and OH Maser-Line Observations of Roberts 22

    NASA Technical Reports Server (NTRS)

    Sahai, R.; Zijlstra, A.; Bujarrabal, V.; Hekkert, P. L.

    1998-01-01

    We have obtained high-resolution wide-band, narrow-band and polarimetric images of the bipolar protoplanetary nebula Roberts 22 with the Wide-Field & Planetary Camera 2 on HST. OH maser-line emission has also been observed using the Australia Telescope Compact Array.

  7. Advanced direct methanol fuel cells. Final report

    SciTech Connect

    Hamdan, Monjid; Kosek, John A.

    1999-11-01

    The goal of the program was an advanced proton-exchange membrane (PEM) for use as the electrolyte in a liquid feed direct methanol fuel cell which provides reduced methanol crossover while simultaneously providing high conductivity and low membrane water content. The approach was to use a membrane containing precross-linked fluorinated base polymer films and subsequently to graft the base film with selected materials. Over 80 different membranes were prepared. The rate of methanol crossover through the advanced membranes was reduced 90%. A 5-cell stack provided stable performance over a 100-hour life test. Preliminary cost estimates predicted a manufacturing cost at $4 to $9 per kW.

  8. DISCOVERY OF CANDIDATE H{sub 2}O DISK MASERS IN ACTIVE GALACTIC NUCLEI AND ESTIMATIONS OF CENTRIPETAL ACCELERATIONS

    SciTech Connect

    Greenhill, Lincoln J.; Moran, James M.; Tilak, Avanti; Kondratko, Paul T.

    2009-12-10

    Based on spectroscopic signatures, about one-third of known H{sub 2}O maser sources in active galactic nuclei (AGNs) are believed to arise in highly inclined accretion disks around central engines. These 'disk maser candidates' are of interest primarily because angular structure and rotation curves can be resolved with interferometers, enabling dynamical study. We identify five new disk maser candidates in studies with the Green Bank Telescope, bringing the total number published to 30. We discovered two (NGC 1320, NGC 17) in a survey of 40 inclined active galaxies (v {sub sys} < 20, 000 km s{sup -1}). The remaining three disk maser candidates were identified in monitoring of known sources: NGC 449, NGC 2979, and NGC 3735. We also confirm a previously marginal case in UGC 4203. For the disk maser candidates reported here, inferred rotation speeds are 130-500 km s{sup -1}. Monitoring of three more rapidly rotating candidate disks (CG 211, NGC 6264, VV 340A) has enabled measurement of likely orbital centripetal acceleration, and estimation of central masses ((2-7) x10{sup 7} M {sub sun}) and mean disk radii (0.2-0.4 pc). Accelerations may ultimately permit estimation of distances when combined with interferometer data. This is notable because the three AGNs are relatively distant (10,000 km s{sup -1} masers also provide robust orientation references that allow analysis of (mis)alignment between AGNs and surrounding galactic stellar disks, even without extensive interferometric mapping. We find no preference among published disk maser candidates to lie in high-inclination galaxies. This provides independent support for conclusions that in late-type galaxies, central engine accretion disks and galactic plane orientations are not

  9. Dielectric properties of muscle and liver from 500 MHz-40 GHz.

    PubMed

    Abdilla, Lourdes; Sammut, Charles; Mangion, Louis Zammit

    2013-06-01

    Dielectric properties are the most important parameters determining energy deposition when biological tissues are exposed to radio frequency and microwave fields. Energy absorption is determined by the specific absorption rate (SAR). SAR distributions can be computed accurately only if the complex relative permittivity of the target tissue is known to a sufficiently high accuracy, and currently there is a lack of data on the dielectric properties of biological tissues at high frequencies. In this study, tissue dielectric properties are measured using an open-ended coaxial probe technique from 500 MHz up to 40 GHz. We present dielectric data for ex vivo bovine and porcine muscle and liver tissues at 37 °C. One-pole Cole-Cole model is used to fit the measured data as a function of frequency and the dispersion parameters are presented. This data is supported by an accurate study on reference liquids such as methanol and ethanediol.

  10. Performance of the 12GHz, 200 watt transmitter experiment package for the Hermes satellite

    NASA Technical Reports Server (NTRS)

    Alexovich, R. E.

    1977-01-01

    Performance characteristics from on-orbit tests of the Transmitter Experiment Package (TEP) for the Hermes Satellite are presented. The TEP consists of a Power Processing System (PPS), an Output Stage Tube (OST) and a Variable Conductance Heat Pipe System (VCHPS), all of which are described. The OST is a coupled-cavity Traveling Wave Tube (TWT) with a Multistage Depressed Collector (MDC) and a stepped velocity-tapered slow wave structure for efficiency enhancement. It has an RF output power of 233 watts and overall efficiency of 50.75 percent at a center band frequency of 12.080 GHz. The PPS provides the required operating voltages, regulation, control and protection for the OST. The VCHPS consists of a fin radiator and three dual-artery stainless steel heat pipes using methanol and a mixture of inert gases. Test results presented include efficiencies, RF output power and body current. A discussion of thermal anomalies which occurred is presented.

  11. The 30-GHz monolithic receive module

    NASA Technical Reports Server (NTRS)

    Bauhahn, P.; Geddes, J.; Sokolov, V.; Contolatis, T.

    1988-01-01

    The fourth year progress is described on a program to develop a 27.5 to 30 GHz GaAs monolithic receive module for spaceborne-communication antenna feed array applications, and to deliver submodules for experimental evaluation. Program goals include an overall receive module noise figure of 5 dB, a 30 dB RF to IF gain with six levels of intermediate gain control, a five bit phase shifter, and a maximum power consumption of 250 mW. Submicron gate length single and dual gate FETs are described and applied in the development of monolithic gain control amplifiers and low noise amplifiers. A two-stage monolithic gain control amplifier based on ion implanted dual gate MESFETs was designed and fabricated. The gain control amplifier has a gain of 12 dB at 29 GHz with a gain control range of over 13 dB. A two-stage monolithic low noise amplifier based on ion implanted MESFETs which provides 7 dB gain with 6.2 dB noise figure at 29 GHz was also developed. An interconnected receive module containing LNA, gain control, and phase shifter submodules was built using the LNA and gain control ICs as well as a monolithic phase shifter developed previously under this program. The design, fabrication, and evaluation of this interconnected receiver is presented. Progress in the development of an RF/IF submodule containing a unique ion implanted diode mixer diode and a broadband balanced mixer monolithic IC with on-chip IF amplifier and the initial design of circuits for the RF portion of a two submodule receiver are also discussed.

  12. The 8-18 GHz radar spectrometer

    NASA Technical Reports Server (NTRS)

    Bush, T. F.; Ulaby, F. T.

    1973-01-01

    The design, construction, testing, and accuracy of an 8-18 GHz radar spectrometer, an FM-CW system which employs a dual antenna system, is described. The antennas, transmitter, and a portion of the receiver are mounted at the top of a 26 meter hydraulic boom which is in turn mounted on a truck for system mobility. HH and VV polarized measurements are possible at incidence angles ranging from 0 deg. to 80 deg. Calibration is accomplished by referencing the measurements against a Luneberg lens of known radar cross section.

  13. 600-GHz Electronically Tunable Vector Measurement System

    NASA Technical Reports Server (NTRS)

    Dengler, Robert; Maiwald, Frank; Siegel, Peter

    2007-01-01

    A compact, high-dynamic-range, electronically tunable vector measurement system that operates in the frequency range from approximately 560 to approximately 635 GHz has been developed as a prototype of vector measurement systems that would be suitable for use in nearly-real-time active submillimeter-wave imaging. As used here, 'vector measurement system" signifies an instrumentation system that applies a radio-frequency (RF) excitation to an object of interest and measures the resulting amplitude and phase response, relative to either the applied excitatory signal or another reference signal related in a known way to applied excitatory signal.

  14. A wideband 12 GHz down converter

    NASA Technical Reports Server (NTRS)

    Newman, B. A.; Rosenbaum, F. J.

    1972-01-01

    The design, fabrication, and evaluation of a single ended 12 GHz down-converter suitable for use in a low cost satellite ground terminal is described. The mixer uses waveguide, coaxial and MIC (microwave integrated circuit) transmission line components. Theoretical and experimental analyses of several microstrip circuit elements are presented including the traveling wave-directional filter, quarter wave-length proximity directional coupler, low pass filter and the quarterwave band stop filter. The optimum performance achieved for the mixer using a packaged diode was 9.4 db conversion loss and a bandwidth of 275 MHz.

  15. An LTCC 94 GHz Antenna Array

    SciTech Connect

    Aguirre, J; Pao, H; Lin, H; Garland, P; O'Neill, D; Horton, K

    2007-12-21

    An antenna array is designed in low-temperature cofired ceramic (LTCC) Ferro A6M{trademark} for a mm-wave application. The antenna is designed to operate at 94 GHz with a few percent bandwidth. A key manufacturing technology is the use of 3 mil diameter vias on a 6 mil pitch to construct the laminated waveguides that form the beamforming network and radiating elements. Measurements for loss in the laminated waveguide are presented. The slot-fed cavity-radiating element is designed to account for extremely tight mutual coupling between elements. The array incorporates a slot-fed multi-layer beamforming network.

  16. Homogeneous catalyst formulations for methanol production

    DOEpatents

    Mahajan, Devinder; Sapienza, Richard S.; Slegeir, William A.; O'Hare, Thomas E.

    1990-01-01

    There is disclosed synthesis of CH.sub.3 OH from carbon monoxide and hydrogen using an extremely active homogeneous catalyst for methanol synthesis directly from synthesis gas. The catalyst operates preferably between 100.degree.-150.degree. C. and preferably at 100-150 psia synthesis gas to produce methanol. Use can be made of syngas mixtures which contain considerable quantities of other gases, such as nitrogen, methane or excess hydrogen. The catalyst is composed of two components: (a) a transition metal carbonyl complex and (b) an alkoxide component. In the simplest formulation, component (a) is a complex of nickel tetracarbonyl and component (b) is methoxide (CH.sub.3 O.sup.13 ), both being dissolved in a methanol solvent system. The presence of a co-solvent such as p-dioxane, THF, polyalcohols, ethers, hydrocarbons, and crown ethers accelerates the methanol synthesis reaction.

  17. Homogeneous catalyst formulations for methanol production

    DOEpatents

    Mahajan, Devinder; Sapienza, Richard S.; Slegeir, William A.; O'Hare, Thomas E.

    1991-02-12

    There is disclosed synthesis of CH.sub.3 OH from carbon monoxide and hydrogen using an extremely active homogeneous catalyst for methanol synthesis directly from synthesis gas. The catalyst operates preferably between 100.degree.-150.degree. C. and preferably at 100-150 psia synthesis gas to produce methanol. Use can be made of syngas mixtures which contain considerable quantities of other gases, such as nitrogen, methane or excess hydrogen. The catalyst is composed of two components: (a) a transition metal carbonyl complex and (b) an alkoxide component. In the simplest formulation, component (a) is a complex of nickel tetracarbonyl and component (b) is methoxide (CH.sub.3 O.sup.-), both being dissolved in a methanol solvent system. The presence of a co-solvent such as p-dioxane, THF, polyalcohols, ethers, hydrocarbons, and crown ethers accelerates the methanol synthesis reaction.

  18. Advances in direct oxidation methanol fuel cells

    NASA Technical Reports Server (NTRS)

    Surampudi, S.; Narayanan, S. R.; Vamos, E.; Frank, H.; Halpert, G.; Laconti, Anthony B.; Kosek, J.; Prakash, G. K. Surya; Olah, G. A.

    1993-01-01

    Fuel cells that can operate directly on fuels such as methanol are attractive for low to medium power applications in view of their low weight and volume relative to other power sources. A liquid feed direct methanol fuel cell has been developed based on a proton exchange membrane electrolyte and Pt/Ru and Pt catalyzed fuel and air/O2 electrodes, respectively. The cell has been shown to deliver significant power outputs at temperatures of 60 to 90 C. The cell voltage is near 0.5 V at 300 mA/cm(exp 2) current density and an operating temperature of 90 C. A deterrent to performance appears to be methanol crossover through the membrane to the oxygen electrode. Further improvements in performance appear possible by minimizing the methanol crossover rate.

  19. Methanol: A Versatile Fuel for Immediate Use

    ERIC Educational Resources Information Center

    Reed, T. B.; Lerner, R. M.

    1973-01-01

    Advocates the large-scale production and use of methanol as a substitute for the diminishing reserves of low-cost petroleum resources. Describes the manufacturing process and advantages of the versatile fuel. (JR)

  20. BHP may scale up methanol production

    SciTech Connect

    Alperowicz, N.

    1993-06-23

    Broken Hill Pty. (BHP: Melbourne) says otherwise uneconomic gas reserves in the Timor Sea off northwest Australia could be developed if the company`s plans to commercialize a novel gas-to-methanol technology prove to be viable. BHP is building an A$70-million ($50 million) research unit in Victoria using ICI`s Leading Concept Methanol gas-to-methanol process. If this unit proves viable, it could be put on a vessel and taken to Timor Sea where BHP has oil exploration and production interests. Timor gas is not economically viable because of lack of nearby markets. The 54,000-m.t./year research plant, located at Werrbee near Melbourne, is scheduled to start production in the second half of 1994, according to BHP manager Joe Evon. The plant is being built by Davy/John Brown. Provided the economic climate is right, BHP is expected to build a world-scale methanol plant offshore.

  1. Esterification of acrylic acid with methanol

    SciTech Connect

    Chubarov, G.A.; Danov, S.M.; Logutov, V.I.; Obmelyukhina, T.N.

    1984-01-01

    The esterification of acrylic acid with methanol in the absence of catalysis by strong mineral acids has been studied. The esterification rate was estimated from the amount of methyl acrylate formed at the end of a definite time, and the reaction rate was found to be first order with respect to methanol and second order with respect to acrylic acid. Mathematical relationships in good agreement with experimental data were derived from the results of the kinetic studies.

  2. A 17 GHz molecular rectifier

    PubMed Central

    Trasobares, J.; Vuillaume, D.; Théron, D.; Clément, N.

    2016-01-01

    Molecular electronics originally proposed that small molecules sandwiched between electrodes would accomplish electronic functions and enable ultimate scaling to be reached. However, so far, functional molecular devices have only been demonstrated at low frequency. Here, we demonstrate molecular diodes operating up to 17.8 GHz. Direct current and radio frequency (RF) properties were simultaneously measured on a large array of molecular junctions composed of gold nanocrystal electrodes, ferrocenyl undecanethiol molecules and the tip of an interferometric scanning microwave microscope. The present nanometre-scale molecular diodes offer a current density increase by several orders of magnitude compared with that of micrometre-scale molecular diodes, allowing RF operation. The measured S11 parameters show a diode rectification ratio of 12 dB which is linked to the rectification behaviour of the direct current conductance. From the RF measurements, we extrapolate a cut-off frequency of 520 GHz. A comparison with the silicon RF-Schottky diodes, architecture suggests that the RF-molecular diodes are extremely attractive for scaling and high-frequency operation. PMID:27694833

  3. 28 GHz Gyrotron ECRH on LDX

    NASA Astrophysics Data System (ADS)

    Woskov, P. P.; Kesner, J.; Michael, P. C.; Garnier, D. T.; Mauel, M. E.

    2010-12-01

    A 10 kW, CW, 28 GHz gyrotron has been implemented on LDX to increase the plasma density and to more fully explore the potential of high beta plasma stability in a dipole magnetic configuration. This added power represents about a 60% increase in ECRH to a new total of 26.9 kW with sources at 2.45, 6.4, and 10.5 GHz. The 1 Tesla resonances in LDX form small rings encompassing the entire plasma cross-section above and below the floating coil (F-coil) near the dipole axial region. A 32.5 mm diameter TE01 waveguide with a partial Vlasov step cut launches a diverging beam from above the F-coil that depends on internal wall reflections for plasma coupling. Initial gyrotron only plasmas exhibit steep natural profiles with fewer hot electrons than with the other sources. The background scattered radiation suggests that only about half the power is being absorbed with the present launcher.

  4. Methanol-tolerant cathode catalyst composite for direct methanol fuel cells

    DOEpatents

    Zhu, Yimin; Zelenay, Piotr

    2006-09-05

    A direct methanol fuel cell (DMFC) having a methanol fuel supply, oxidant supply, and its membrane electrode assembly (MEA) formed of an anode electrode and a cathode electrode with a membrane therebetween, a methanol oxidation catalyst adjacent the anode electrode and the membrane, an oxidant reduction catalyst adjacent the cathode electrode and the membrane, comprises an oxidant reduction catalyst layer of Pt.sub.3Cr/C so that oxidation at the cathode of methanol that crosses from the anode through the membrane to the cathode is reduced with a concomitant increase of net electrical potential at the cathode electrode.

  5. Methanol-Tolerant Cathode Catalyst Composite For Direct Methanol Fuel Cells

    DOEpatents

    Zhu, Yimin; Zelenay, Piotr

    2006-03-21

    A direct methanol fuel cell (DMFC) having a methanol fuel supply, oxidant supply, and its membrane electrode assembly (MEA) formed of an anode electrode and a cathode electrode with a membrane therebetween, a methanol oxidation catalyst adjacent the anode electrode and the membrane, an oxidant reduction catalyst adjacent the cathode electrode and the membrane, comprises an oxidant reduction catalyst layer of a platinum-chromium alloy so that oxidation at the cathode of methanol that crosses from the anode through the membrane to the cathode is reduced with a concomitant increase of net electrical potential at the cathode electrode.

  6. Transesterification of waste vegetable oil under pulse sonication using ethanol, methanol and ethanol–methanol mixtures

    SciTech Connect

    Martinez-Guerra, Edith; Gude, Veera Gnaneswar

    2014-12-15

    Highlights: • Pulse sonication effect on transesterification of waste vegetable oil was studied. • Effects of ethanol, methanol, and alcohol mixtures on FAMEs yield were evaluated. • Effect of ultrasonic intensity, power density, and its output rates were evaluated. • Alcohol mixtures resulted in higher biodiesel yields due to better solubility. - Abstract: This study reports on the effects of direct pulse sonication and the type of alcohol (methanol and ethanol) on the transesterification reaction of waste vegetable oil without any external heating or mechanical mixing. Biodiesel yields and optimum process conditions for the transesterification reaction involving ethanol, methanol, and ethanol–methanol mixtures were evaluated. The effects of ultrasonic power densities (by varying sample volumes), power output rates (in W), and ultrasonic intensities (by varying the reactor size) were studied for transesterification reaction with ethanol, methanol and ethanol–methanol (50%-50%) mixtures. The optimum process conditions for ethanol or methanol based transesterification reaction of waste vegetable oil were determined as: 9:1 alcohol to oil ratio, 1% wt. catalyst amount, 1–2 min reaction time at a power output rate between 75 and 150 W. It was shown that the transesterification reactions using ethanol–methanol mixtures resulted in biodiesel yields as high as >99% at lower power density and ultrasound intensity when compared to ethanol or methanol based transesterification reactions.

  7. Vacuum-Ultraviolet (VUV) Photoionization of Small Methanol and Methanol-Water Clusters

    SciTech Connect

    Kostko, Oleg; Belau, Leonid; Wilson, Kevin R.; Ahmed, Musahid

    2008-04-24

    In this work, we report on the vacuum-ultraviolet (VUV) photoionization of small methanol and methanol-water clusters. Clusters of methanol with water are generated via co-expansion of the gas phase constituents in a continuous supersonic jet expansion of methanol and water seeded in Ar. The resulting clusters are investigated by single photon ionization with tunable vacuum-ultraviolet synchrotron radiation and mass analyzed using reflectron mass spectrometry. Protonated methanol clusters of the form (CH3OH)nH+(n = 1-12) dominate the mass spectrum below the ionization energy of the methanol monomer. With an increase in water concentration, small amounts of mixed clusters of the form (CH3OH n(H2O)H+ (n = 2-11) are detected. The only unprotonated species observed in this work are the methanol monomer and dimer. Appearance energies are obtained from the photoionization efficiency (PIE) curves for CH3OH+, (CH3OH)2+, (CH3OH)nH+ (n = 1-9), and (CH3OH)n(H2O)H+ (n = 2-9) as a function of photon energy. With an increasein the water content in the molecular beam, there is an enhancement of photoionization intensity for the methanol dimer and protonated methanol monomer at threshold. These results are compared and contrasted to previous experimental observations.

  8. Vacuum-ultraviolet (VUV) photoionization of small methanol and methanol-water clusters

    SciTech Connect

    Ahmed, Musahid; Ahmed, Musahid; Wilson, Kevin R.; Belau, Leonid; Kostko, Oleg

    2008-05-12

    In this work we report on thevacuum-ultraviolet (VUV) photoionization of small methanol and methanol-water clusters. Clusters of methanol with water are generated via co-expansion of the gas phase constituents in a continuous supersonic jet expansion of methanol and water seeded in Ar. The resulting clusters are investigated by single photon ionization with tunable vacuumultraviolet synchrotron radiation and mass analyzed using reflectron mass spectrometry. Protonated methanol clusters of the form (CH3OH)nH + (n=1-12) dominate the mass spectrum below the ionization energy of the methanol monomer. With an increase in water concentration, small amounts of mixed clusters of the form (CH3OH)n(H2O)H + (n=2-11) are detected. The only unprotonated species observed in this work are the methanol monomer and dimer. Appearance energies are obtained from the photoionization efficiency (PIE) curves for CH3OH +, (CH 3OH)2 +, (CH3OH)nH + (n=1-9), and (CH 3OH)n(H2O)H + (n=2-9 ) as a function of photon energy. With an increase in the water content in the molecular beam, there is an enhancement of photoionization intensity for methanol dimer and protonated methanol monomer at threshold. These results are compared and contrasted to previous experimental observations.

  9. Microfluidic distillation chip for methanol concentration detection.

    PubMed

    Wang, Yao-Nan; Liu, Chan-Chiung; Yang, Ruey-Jen; Ju, Wei-Jhong; Fu, Lung-Ming

    2016-03-17

    An integrated microfluidic distillation system is proposed for separating a mixed ethanol-methanol-water solution into its constituent components. The microfluidic chip is fabricated using a CO2 laser system and comprises a serpentine channel, a boiling zone, a heating zone, and a cooled collection chamber filled with de-ionized (DI) water. In the proposed device, the ethanol-methanol-water solution is injected into the microfluidic chip and driven through the serpentine channel and into the collection chamber by means of a nitrogen carrier gas. Following the distillation process, the ethanol-methanol vapor flows into the collection chamber and condenses into the DI water. The resulting solution is removed from the collection tank and reacted with a mixed indicator. Finally, the methanol concentration is inversely derived from the absorbance measurements obtained using a spectrophotometer. The experimental results show the proposed microfluidic system achieves an average methanol distillation efficiency of 97%. The practicality of the proposed device is demonstrated by detecting the methanol concentrations of two commercial fruit wines. It is shown that the measured concentration values deviate by no more than 3% from those obtained using a conventional bench top system.

  10. Decay of N-qubit GHZ states in Pauli channels

    NASA Astrophysics Data System (ADS)

    Chen, Xiao-Yu; Wang, Ting-Ting

    2015-08-01

    An N-qubit Greenberger-Horne-Zeilinger (GHZ) state has many applications in various quantum information tasks and can be realized in different experimental schemes. A GHZ diagonal state evolves to another GHZ diagonal state in independent parallel Pauli channels. We give the explicit expression of the resultant GHZ diagonal state in terms of the initial state and channel parameters. If the initial state is a pure N qubit GHZ state or a three-qubit GHZ diagonal state admits a condition, the full separability criterion of the Pauli noisy state is equivalent to positive partial transpose (PPT) criterion. Thus the fully separable condition follows. Project supported by the National Natural Science Foundation of China (Grant No. 11375152).

  11. Pharmacokinetics of methanol and formate in female cynomolgus monkeys exposed to methanol vapors.

    PubMed

    Medinsky, M A; Dorman, D C; Bond, J A; Moss, O R; Janszen, D B; Everitt, J I

    1997-06-01

    The 1990 Clean Air Act Amendments contain mandates for reduced automotive emissions and add new requirements for the use of alternative fuels such as methanol to reduce certain automotive pollutants. Methanol is acutely toxic in humans at relatively low doses, and the potential for exposure to methanol will be increased if it is used in automotive fuel. Formate is the metabolite responsible for neurotoxic effects of acute methanol exposure. Since formate metabolism is dependent on folate, potentially sensitive folate-deficient subpopulations, such as pregnant women, may accumulate formate and be at higher risk from low-level methanol exposure. Our objective was to determine the pharmacokinetics of 14C-methanol and 14C-formate in normal and folate-deficient monkeys after exposure to 14C-methanol vapors at environmentally relevant concentrations: below the threshold limit value (TLV), at the TLV of 200 parts per million (ppm), and above the TLV. Four normal adult female cynomolgus monkeys were individually anesthetized with isoflurane, and each was exposed by endotracheal intubation to 10, 45, 200, or 900 ppm 14C-methanol for 2 hours. Concentrations of the inhaled and exhaled 14C-methanol, blood concentrations of 14C-methanol and 14C-formate, exhaled 14C-carbon dioxide (14CO2), and respiratory parameters were measured during exposure. After exposure, 14C-methanol and 14CO2 exhaled, 14C-methanol and 14C-formate excreted in urine, and 14C-methanol and 14C-formate in blood were quantified. The amounts of exhaled 14C-methanol and 14CO2, blood concentrations of 14C-methanol and 14C-formate, and 14C-methanol and 14C-formate excreted in urine were linearly related to methanol exposure concentration. For all exposures, blood concentrations of 14C-methanol-derived formate were 10 to 1000 times lower than endogenous blood formate concentrations (100 to 200 mM) reported for monkeys and were several orders of magnitude lower than levels of formate known to be toxic. Since the

  12. Preliminary Bremstrahlung Measurements on VENUS at 18 and 28 GHz

    SciTech Connect

    Lyneis, C.M.; Leitner, D.

    2005-03-15

    The bremstrahlung produced by the VENUS ECR ion source at 18 GHz and 28 GHz in the axial direction has been measured with a germanium detector. The bremstrahlung spectrum goes out beyond 1 MeV at 28 GHz and this complicates analysis of the data and the design of the collimators and detection system. Preliminary spectra and the geometry of the detection system will be described.

  13. A 94/183 GHz multichannel radiometer for Convair flights

    NASA Technical Reports Server (NTRS)

    Gagliano, J. A.; Stratigos, J. A.; Forsythe, R. E.; Schuchardt, J. M.

    1979-01-01

    A multichannel 94/183 GHz radiometer was designed, built, and installed on the NASA Convair 990 research aircraft to take data for hurricane penetration flights, SEASAT-A underflights for measuring rain and water vapor, and Nimbus-G underflights for new sea ice signatures and sea surface temperature data (94 GHz only). The radiometer utilized IF frequencies of 1, 5, and 8.75 GHz about the peak of the atmospheric water vapor absorption line, centered at 183.3 GHz, to gather data needed to determine the shape of the water molecule line. Another portion of the radiometer operated at 94 GHz and obtained data on the sea brightness temperature, sea ice signatures, and on areas of rain near the ocean surface. The radiometer used a multiple lens antenna/temperature calibration technique using 3 lenses and corrugated feed horns at 94 GHz and 183 GHz. Alignment of the feed beams at 94 GHz and 183 GHz was accomplished using a 45 deg oriented reflecting surface which permitted simultaneous viewing of the feeds on alternate cycles of the chopping intervals.

  14. Synchrotron Spectral Curvature from 22 MHZ to 23 GHZ

    NASA Technical Reports Server (NTRS)

    Kogut, Alan J.

    2012-01-01

    We combine surveys of the radio sky at frequencies 22 MHz to 1.4 GHz with data from the ARCADE-2 instrument at frequencies 3 GHz to 10 GHz to characterize the frequency spectrum of diffuse synchrotron emission in the Galaxy. The radio spectrum steepens with frequency from 22 MHz to 10 GHz. The projected spectral index at 23 GHz derived from the low-frequency data agrees well with independent measurements using only data at frequencies 23 GHz and above. Comparing the spectral index at 23 GHz to the value from previously published analyses allows extension of the model to higher frequencies. The combined data are consistent with a power-law index beta = -2.64 +/-= 0.03 at 0.31 GHz, steepening by an amount of Delta-beta = 0.07 every octave in frequency. Comparison of the radio data to models including the cosmic-ray energy spectrum suggests that any break in the synchrotron spectrum must occur at frequencies above 23 GHz.

  15. Searching for dark matter and variation of fundamental constants with laser and maser interferometry.

    PubMed

    Stadnik, Y V; Flambaum, V V

    2015-04-24

    Any slight variations in the fundamental constants of nature, which may be induced by dark matter or some yet-to-be-discovered cosmic field, would characteristically alter the phase of a light beam inside an interferometer, which can be measured extremely precisely. Laser and maser interferometry may be applied to searches for the linear-in-time drift of the fundamental constants, detection of topological defect dark matter through transient-in-time effects, and for a relic, coherently oscillating condensate, which consists of scalar dark matter fields, through oscillating effects. Our proposed experiments require either minor or no modifications of existing apparatus, and offer extensive reach into important and unconstrained spaces of physical parameters.

  16. Method of producing a storage bulb for an atomic hydrogen maser

    NASA Technical Reports Server (NTRS)

    Erpenbach, H. (Inventor)

    1975-01-01

    A storage bulb for an atomic hydrogen maser is produced by coating its internal surface with an emulsion containing both TFE and FEP particles. The emulsion is produced by mixing a first quantity of TFE in an aqueous dispersion with a second quantity of FEP in an aqueous dispersion, with a third quantity of distilled water. The emulsion is poured into the bulb to coat it uniformly so as to form a thin film of emulsion on the bulb's internal surface. After excess emulsion is drained out of the bulb the emulsion in the bulb is dried to remove the water and most of the aqueous matter therefrom. The remaining emulsion is then cured by heating the bulb to a temperature of at least 380 C.

  17. A frequency-locked, high-power, X-band dielectric Cerenkov maser

    SciTech Connect

    Weatherall, J.C. )

    1992-06-01

    Most research on the dielectric Cerenkov maser (DCM) has focused only on free running oscillators. Presented in this paper, is a high-power frequency-locked oscillator. The device consists of an annular electron beam traveling down a dielectric-lined waveguide (wall radius 1.74 cm, liner thickness 2-3 mm, liner {epsilon} = 10). A 100 kW input signal is injected into the drift tube between the diode and liner, through a rectangular TE{sub 10} to cylindrical TM{sub 01} mode converter. When operated with a beam current of 500 A and a total output power of 13 MW, the device displays no RF quenching through the full width of the 100 ns beam pulse. Two higher current cases are presented with power as high as 280 MW but severe RF quenching. The results are compared with linear theory, and quenching mechanisms are discussed.

  18. Self-amplification of coherent spontaneous emission in a cherenkov free-electron maser

    PubMed

    Wiggins; Jaroszynski; McNeil; Robb; Aitken; Phelps; Cross; Ronald; Ginzburg; Shpak; Yalandin; Shunailov; Ulmaskulov

    2000-03-13

    Ultrashort pulses of microwave radiation have been produced in a dielectric-lined Cherenkov free-electron maser (FEM) amplifier. An intense initial seed pulse, due to coherent spontaneous emission (CSE), arises at the leading edge of the electron pulse. There is evidence to show that 3-4 cycle spikes are produced through the amplification of these seed pulses. A strong dependence of the start-up power on the rise time of the electron pulse has been found. The experimental results are verified by a theoretical analysis. Our study shows that amplification in a FEM amplifier is always initiated by CSE arising from the edge of the electron pulse when the rise time is comparable to the electromagnetic wave period. PMID:11018893

  19. Linearly polarized radiation from astrophysical masers due to magnetic fields of intermediate strength

    NASA Technical Reports Server (NTRS)

    Nedoluha, Gerald E.; Watson, William D.

    1990-01-01

    Previous solutions for polarization of astrophysical maser radiation due to closed-shell molecules in a magnetic field have potentially serious limitations. These solutions are mostly based on the approximation that the Zeeman frequency g-Omega is much greater than the rate for stimulated emission R and the rate for decay Gamma of the molecular state. Others are asymptotic solutions obtained for an angular momentum J = 1-0 transition. It has been unclear whether the polarizations due to plausible Zeeman splittings are adequately represented by the solutions obtained for g-Omega/Gamma much greater than 1 and g-Omega/R much greater than 1. Actual masing transitions tend to involve molecular states with angular momenta that are higher than J = 1 and 0. Numerical solutions for the linear polarization are presented here which do not have the foregoing restrictions on the g-Omega and which are not limited to a J = 1-0 transition.

  20. Linear analysis of a rectangular waveguide cyclotron maser with a sheet electron beam

    SciTech Connect

    Zhao Ding; Ding Yaogen; Wang Yong; Ruan Cunjun

    2010-11-15

    A linear theory for a rectangular waveguide cyclotron maser with a sheet electron beam is developed by using the Laplace transformation approach. This theory can be applied to any TE{sub mn} rectangular waveguide mode. The corresponding equations for the TM{sub mn} mode in the rectangular waveguide are also derived as a useful reference. Especially, the effect from the coupling between degenerate modes, which is induced by the nonideal rectangular waveguide walls, on the dispersion relation is considered in order to provide a more accurate model for the real devices. Through numerical calculations, the linear growth rate, launching loss, and spontaneous oscillations (caused by the absolute instability and backward wave oscillation) of this new structure can be analyzed in detail. It is worthwhile to point out that the operation at higher power levels of the rectangular waveguide sheet beam system is possible.

  1. Spatial distribution and luminosity function of OH/IR maser sources

    NASA Astrophysics Data System (ADS)

    Tong, Y.; Sun, J.; Xie, S.-D.; Yang, X.-X.

    1984-12-01

    Published observational data on 127 OH-maser sources for which visible or IR identifications and distance estimates are available (mainly from the list of Engels, 1979) are analyzed statistically to determine their Galactic distribution and luminosity function. The results are presented graphically and discussed. A density distribution with a steep peak at about 7.5 kpc from the Galactic center and FWHM 2.1 kpc, similar to that found for Mira variables by Glass et al. (1982) and markedly different from that of Baud et al. (1979 and 1981) for unidentified objects, is observed. The luminosity function rho(L) is found to be equal to 189.67 L exp -1.79, like that for unidentified objects, despite the fact that the observed luminosity range (0.16-1000 Jy kpc sq) of the identified sources is wider than that determined by Bowers (1978) for unidentified sources.

  2. Evolution of the axial electron cyclotron maser instability, with applications to solar microwave spikes

    NASA Technical Reports Server (NTRS)

    Vlahos, Loukas; Sprangle, Phillip

    1987-01-01

    The nonlinear evolution of cyclotron radiation from streaming and gyrating electrons in an external magnetic field is analyzed. The nonlinear dynamics of both the fields and the particles are treated fully relativistically and self-consistently. The model includes a background plasma and electrostatic effects. The analytical and numerical results show that a substantial portion of the beam particle energy can be converted to electromagnetic wave energy at frequencies far above the electron cyclotron frequency. In general, the excited radiation can propagate parallel to the magnetic field and, hence, escape gyrothermal absorption at higher cyclotron harmonics. The high-frequency Doppler-shifted cyclotron instability can have saturation efficiencies far higher than those associated with well-known instabilities of the electron cyclotron maser type. Although the analysis is general, the possibility of using this model to explain the intense radio emission observed from the sun is explored in detail.

  3. Injection locking of an electronic maser in the hard excitation mode

    SciTech Connect

    Yakunina, K. A.; Kuznetsov, A. P.; Ryskin, N. M.

    2015-11-15

    The phenomenon of hard excitation is natural for many electronic oscillators. In particular, in a gyrotron, a maximal efficiency is often attained in the hard excitation regime. In this paper, we study the injection-locking phenomena using two models of an electronic maser in the hard excitation mode. First, bifurcation analysis is performed for the quasilinear model described by ordinary differential equations for the slow amplitude and phase. Two main scenarios of transition to the injection-locked mode are described, which are generalizations of the well-known phase-locking and suppression mechanisms. The results obtained for the quasilinear model are confirmed by numerical simulations of a gyrotron with fixed Gaussian structure of the RF field.

  4. ORIGIN OF ELECTRON CYCLOTRON MASER INDUCED RADIO EMISSIONS AT ULTRACOOL DWARFS: MAGNETOSPHERE-IONOSPHERE COUPLING CURRENTS

    SciTech Connect

    Nichols, J. D.; Burleigh, M. R.; Casewell, S. L.; Cowley, S. W. H.; Wynn, G. A.; Clarke, J. T.; West, A. A.

    2012-11-20

    A number of ultracool dwarfs emit circularly polarized radio waves generated by the electron cyclotron maser instability. In the solar system such radio is emitted from regions of strong auroral magnetic-field-aligned currents. We thus apply ideas developed for Jupiter's magnetosphere, being a well-studied rotationally dominated analog in our solar system, to the case of fast-rotating UCDs. We explain the properties of the radio emission from UCDs by showing that it would arise from the electric currents resulting from an angular velocity shear in the fast-rotating magnetic field and plasma, i.e., by an extremely powerful analog of the process that causes Jupiter's auroras. Such a velocity gradient indicates that these bodies interact significantly with their space environment, resulting in intense auroral emissions. These results strongly suggest that auroras occur on bodies outside our solar system.

  5. GHz Electroluminescence Modulation in Nanoscale Subwavelength Emitters.

    PubMed

    Rossella, Francesco; Piazza, Vincenzo; Rocci, Mirko; Ercolani, Daniele; Sorba, Lucia; Beltram, Fabio; Roddaro, Stefano

    2016-09-14

    We investigate light emission from nanoscale point-sources obtained in hybrid metal-GaAs nanowires embedding two sharp axial Schottky barriers. Devices are obtained via the formation of Ni-rich metallic alloy regions in the nanostructure body thanks to a technique of controlled thermal annealing of Ni/Au electrodes. In agreement with recent findings, visible-light electroluminescence can be observed upon suitable voltage biasing of the junctions. We investigate the time-resolved emission properties of our devices and demonstrate an electrical modulation of light generation up to 1 GHz. We explore different drive configurations and discuss the intrinsic bottlenecks of the present device architecture. Our results demonstrate a novel technique for the realization of fast subwavelength light sources with possible applications in sensing and microscopy beyond the diffraction limit. PMID:27532324

  6. Operation of the SUPARAMP at 33GHz

    NASA Technical Reports Server (NTRS)

    Chiao, R. Y.; Parrish, P. T.

    1975-01-01

    A 9mm degenerate parametric amplifier was constructed using a linear, series array of unbiased Josephson junctions as the active, nonlinear element. A balanced diode mixer was used as a synchronous detector, with a single source serving both as the pump and as the mixer local oscillator. A stable, net gain of 15 dB in an instantaneous bandwith (FWHM) of 3.4 GHz was achieved. A system noise temperature of 220 K + or - 5 K (DSB) was measured with a SUPARAMP contribution of only 20 K x or - 10 K. Output saturation was observed and complicates the interpretation of the noise temperature measurements and may render them upper limits. A comparison was made with the results of an earlier 3 cm suparamp. The data is in substantial agreement with theoretical predictions.

  7. The 94 GHz MMW imaging radar system

    NASA Technical Reports Server (NTRS)

    Alon, Yair; Ulmer, Lon

    1993-01-01

    The 94 GHz MMW airborne radar system that provides a runway image in adverse weather conditions is now undergoing tests at Wright-Patterson Air Force Base (WPAFB). This system, which consists of a solid state FMCW transceiver, antenna, and digital signal processor, has an update rate of 10 times per second, 0.35x azimuth resolution and up to 3.5 meter range resolution. The radar B scope (range versus azimuth) image, once converted to C scope (elevation versus azimuth), is compatible with the standard TV presentation and can be displayed on the Head Up Display (HUD) or Head Down Display (HDD) to aid the pilot during landing and takeoff in limited visibility conditions.

  8. Direct satellite TV - The 12-GHz challenge

    NASA Astrophysics Data System (ADS)

    Fawcette, J.

    1982-02-01

    Manufacturers in Japan and Europe are developing the hardware necessary for commercially feasible direct broadcast satellite TV, including high-frequency circuits and mini-dishes for spacecasting. US companies are lagging behind due to formidable regulatory and legal difficulties. The article focuses on efforts to develop simple, inexpensive receivers which will be able to convert 12-GHz satellite transmissions into high-quality TV images. Three basic receiver designs are being developed: the mixer-downcaster, microwave integrated circuits using FET-preamplifier front ends with transistors connected by bond-wires, and monolithic gallium arsenide integrated circuits. Several companies are on the verge of introducing commercialized receivers utilizing these different basic designs.

  9. Contact gating at GHz frequency in graphene

    PubMed Central

    Wilmart, Q.; Inhofer, A.; Boukhicha, M.; Yang, W.; Rosticher, M.; Morfin, P.; Garroum, N.; Fève, G.; Berroir, J.-M.; Plaçais, B.

    2016-01-01

    The paradigm of graphene transistors is based on the gate modulation of the channel carrier density by means of a local channel gate. This standard architecture is subject to the scaling limit of the channel length and further restrictions due to access and contact resistances impeding the device performance. We propose a novel design, overcoming these issues by implementing additional local gates underneath the contact region which allow a full control of the Klein barrier taking place at the contact edge. In particular, our work demonstrates the GHz operation of transistors driven by independent contact gates. We benchmark the standard channel and novel contact gating and report for the later dynamical transconductance levels at the state of the art. Our finding may find applications in electronics and optoelectronics whenever there is need to control independently the Fermi level and the electrostatic potential of electronic sources or to get rid of cumbersome local channel gates. PMID:26879709

  10. Quantum limited quasiparticle mixers at 100 GHz

    SciTech Connect

    Mears, C.A; Hu, Qing; Richards, P.L. ); Worsham, A.H.; Prober, D.E. . Dept. of Applied Physics); Raeisaenen, A.V. . Radio Lab.)

    1990-09-01

    We have made accurate measurements of the noise and gain of superconducting-insulating-superconducting (SIS) mixers employing small area (1{mu}m{sup 2}) Ta/Ta{sub 2}O{sub 5}/Pb{sub 0.9}Bi{sub 0.1} tunnel junctions. We have measured an added mixer noise of 0.61 +/{minus} 0.31 quanta at 95.0 GHz, which is within 25 percent of the quantum limit of 0.5 quanta. We have carried out a detailed comparison between theoretical predictions of the quantum theory of mixing and experimentally measured noise and gain. We used the shapes of I-V curves pumped at the upper and lower sideband frequencies to deduce values of the embedding admittances at these frequencies. Using these admittances, the mixer noise and gain predicted by quantum theory are in excellent agreement with experiment. 21 refs., 9 figs.

  11. Contact gating at GHz frequency in graphene

    NASA Astrophysics Data System (ADS)

    Wilmart, Q.; Inhofer, A.; Boukhicha, M.; Yang, W.; Rosticher, M.; Morfin, P.; Garroum, N.; Fève, G.; Berroir, J.-M.; Plaçais, B.

    2016-02-01

    The paradigm of graphene transistors is based on the gate modulation of the channel carrier density by means of a local channel gate. This standard architecture is subject to the scaling limit of the channel length and further restrictions due to access and contact resistances impeding the device performance. We propose a novel design, overcoming these issues by implementing additional local gates underneath the contact region which allow a full control of the Klein barrier taking place at the contact edge. In particular, our work demonstrates the GHz operation of transistors driven by independent contact gates. We benchmark the standard channel and novel contact gating and report for the later dynamical transconductance levels at the state of the art. Our finding may find applications in electronics and optoelectronics whenever there is need to control independently the Fermi level and the electrostatic potential of electronic sources or to get rid of cumbersome local channel gates.

  12. Assessment of methanol electro-oxidation for direct methanol-air fuel cells

    SciTech Connect

    Fritts, S.D.; Sen, R.K.

    1988-07-01

    The Office of Energy Storage and Distribution of the US Department of Energy (DOE) supports the development of a methanol-air fuel cell for transportation application. The approach used at Los Alamos National Laboratory converts the methanol fuel to a hydrogen-rich gas in a reformer, then operates the fuel cell on hydrogen and air. The reformer tends to be bulky (raising vehicle packaging problems), has a long startup period, and is not well suited for the transient operation required in a vehicle. Methanol, however, can be oxidized electrochemically in the fuel cell. If this process can be conducted efficiently, a direct methanol-air fuel cell can be used, which does not require a reformer. The objective of this study is to assess the potential of developing a suitable catalyst for the direct electrochemical oxidation of methanol. The primary conclusion of this study is that no acceptable catalysts exist can efficiently oxidize methanol electrochemically and have the desired cost and lifetime for vehicle applications. However, recent progress in understanding the mechanism of methanol oxidation indicates that a predictive base can be developed to search for methanol oxidation catalysts and can be used to methodically develop improved catalysts. Such an approach is strongly recommended. The study also recommends that until further progress in developing high-performance catalysts is achieved, research in cell design and testing is not warranted. 43 refs., 12 figs., 1 tab.

  13. Transesterification of waste vegetable oil under pulse sonication using ethanol, methanol and ethanol-methanol mixtures.

    PubMed

    Martinez-Guerra, Edith; Gude, Veera Gnaneswar

    2014-12-01

    This study reports on the effects of direct pulse sonication and the type of alcohol (methanol and ethanol) on the transesterification reaction of waste vegetable oil without any external heating or mechanical mixing. Biodiesel yields and optimum process conditions for the transesterification reaction involving ethanol, methanol, and ethanol-methanol mixtures were evaluated. The effects of ultrasonic power densities (by varying sample volumes), power output rates (in W), and ultrasonic intensities (by varying the reactor size) were studied for transesterification reaction with ethanol, methanol and ethanol-methanol (50%-50%) mixtures. The optimum process conditions for ethanol or methanol based transesterification reaction of waste vegetable oil were determined as: 9:1 alcohol to oil ratio, 1% wt. catalyst amount, 1-2 min reaction time at a power output rate between 75 and 150 W. It was shown that the transesterification reactions using ethanol-methanol mixtures resulted in biodiesel yields as high as >99% at lower power density and ultrasound intensity when compared to ethanol or methanol based transesterification reactions.

  14. Opportunities for coal to methanol conversion

    SciTech Connect

    Not Available

    1980-04-01

    The accumulations of mining residues in the anthracite coal regions of Pennsylvania offer a unique opportunity to convert the coal content into methanol that could be utilized in that area as an alternative to gasoline or to extend the supplies through blending. Additional demand may develop through the requirements of public utility gas turbines located in that region. The cost to run this refuse through coal preparation plants may result in a clean coal at about $17.00 per ton. After gasification and synthesis in a 5000 ton per day facility, a cost of methanol of approximately $3.84 per million Btu is obtained using utility financing. If the coal is to be brought in by truck or rail from a distance of approximately 60 miles, the cost of methanol would range between $4.64 and $5.50 per million Btu depending upon the mode of transportation. The distribution costs to move the methanol from the synthesis plant to the pump could add, at a minimum, $2.36 per million Btu to the cost. In total, the delivered cost at the pump for methanol produced from coal mining wastes could range between $6.20 and $7.86 per million Btu.

  15. On the Identification of High-Mass Star Forming Regions Using IRAS: Contamination by Low-Mass Protostars

    NASA Astrophysics Data System (ADS)

    Bourke, Tyler L.; Hyland, A. R.; Robinson, Garry

    2005-06-01

    We present the results of a survey of a small sample (14) of low-mass protostars (LIR<103 Lsolar) for 6.7 GHz methanol maser emission performed using the ATNF Parkes radio telescope. No new masers were discovered. We find that the lower luminosity limit for maser emission is near 103 Lsolar by comparison of the sources in our sample with previously detected methanol maser sources. We examine the IRAS properties of our sample and compare them with sources previously observed for methanol maser emission, almost all of which satisfy the Wood & Churchwell criterion for selecting candidate UC H II regions. We find that about half of our sample satisfy this criterion, and in addition, almost all of this subgroup have integrated fluxes between 25 and 60 μm that are similar to sources with detectable methanol maser emission. By identifying a number of low-mass protostars in this work and from the literature that satisfy the Wood & Churchwell criterion for candidate UC H II regions, we show conclusively for the first time that the fainter flux end of their sample is contaminated by lower mass nonionizing sources, confirming the suggestion by van der Walt and Ramesh & Sridharan.

  16. A Study of Dielectric Properties of Proteinuria between 0.2 GHz and 50 GHz

    PubMed Central

    Mun, Peck Shen; Ting, Hua Nong; Ong, Teng Aik; Wong, Chew Ming; Ng, Kwan Hong; Chong, Yip Boon

    2015-01-01

    This paper investigates the dielectric properties of urine in normal subjects and subjects with chronic kidney disease (CKD) at microwave frequency of between 0.2 GHz and 50 GHz. The measurements were conducted using an open-ended coaxial probe at room temperature (25°C), at 30°C and at human body temperature (37°C). There were statistically significant differences in the dielectric properties of the CKD subjects compared to those of the normal subjects. Statistically significant differences in dielectric properties were observed across the temperatures for normal subjects and CKD subjects. Pearson correlation test showed the significant correlation between proteinuria and dielectric properties. The experimental data closely matched the single-pole Debye model. The relaxation dispersion and relaxation time increased with the proteinuria level, while decreasing with the temperature. As for static conductivity, it increased with proteinuria level and temperature. PMID:26066351

  17. 100-GHz and 300-GHz coherent radio-over-fiber transmission using optical frequency comb source

    NASA Astrophysics Data System (ADS)

    Kanno, Atsushi; Kuri, Toshiaki; Hosako, Iwao; Kawanishi, Tetsuya; Yasumura, Yoshihiro; Yoshida, Yuki; Kitayama, Ken-ichi

    2013-01-01

    Millimeter-wave and sub-millimeter-wave radio-over-fiber (RoF) technology with digital-signal-processing­ aided coherent detection can be a promising candidate for high-speed radio transmission links with a capacity of greater than 10 Gb/s if the energy consumption does not increase drastically. We demonstrate 100-GHz­ and 300-GHz-band simultaneous RoF signal generation using an optical frequency comb source comprising an optical frequency shifter in an amplified optical fiber loop, and its radio transmission over the air. 10-Gbaud quadrature-phase-shift-keying provides a capacity of 18.6 Gb /s with a 7% forward error correction overhead in single carrier signal transmission as well as in multi-carrier transmission.

  18. Noise in waveguide between 18 GHz and 26.5 GHz

    NASA Astrophysics Data System (ADS)

    Allal, D.

    2016-01-01

    This report summarises the results of the Key Comparison CCEM.RF-K22.W on noise temperature, performed between October 2007 and February 2011. In this comparison, the available noise temperature of three noise sources was determined by six National Metrology Institutes (NMIs) in the frequency range from 18 GHz to 26.5 GHz. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  19. A 250 GHz Gyrotron with a 3 GHz Tuning Bandwidth for Dynamic Nuclear Polarization

    PubMed Central

    Barnes, Alexander B.; Nanni, Emilio A.; Herzfeld, Judith; Griffin, Robert G.; Temkin, Richard J.

    2012-01-01

    We describe the design and implementation of a novel tunable 250 GHz gyrotron oscillator with >10 W output power over most of a 3 GHz band and >35 W peak power. The tuning bandwidth and power are sufficient to generate a >1 MHz nutation frequency across the entire nitroxide EPR lineshape for cross effect DNP, as well as to excite solid effect transitions utilizing other radicals, without the need for sweeping the NMR magnetic field. Substantially improved tunability is achieved by implementing a long (23 mm) interaction cavity that can excite higher order axial modes by changing either the magnetic field of the gyrotron or the cathode potential. This interaction cavity excites the rotating TE5,2,q mode, and an internal mode converter outputs a high-quality microwave beam with >94% Gaussian content. The gyrotron was integrated into a DNP spectrometer, resulting in a measured DNP enhancement of 54 on the membrane protein bacteriorhodopsin. PMID:22743211

  20. Rectenna Technology Program: Ultra light 2.45 GHz rectenna 20 GHz rectenna

    NASA Technical Reports Server (NTRS)

    Brown, William C.

    1987-01-01

    The program had two general objectives. The first objective was to develop the two plane rectenna format for space application at 2.45 GHz. The resultant foreplane was a thin-film, etched-circuit format fabricated from a laminate composed of 2 mil Kapton F sandwiched between sheets of 1 oz copper. The thin-film foreplane contains half wave dipoles, filter circuits, rectifying Schottky diode, and dc bussing lead. It weighs 160 grams per square meter. Efficiency and dc power output density were measured at 85% and 1 kw/sq m, respectively. Special testing techniques to measure temperature of circuit and diode without perturbing microwave operation using the fluoroptic thermometer were developed. A second objective was to investigate rectenna technology for use at 20 GHz and higher frequencies. Several fabrication formats including the thin-film scaled from 2.45 GHz, ceramic substrate and silk-screening, and monolithic were investigated, with the conclusion that the monolithic approach was the best. A preliminary design of the monolithic rectenna structure and the integrated Schottky diode were made.