Cloud chamber researches in nuclear physics and cosmic radiation

International Nuclear Information System (INIS)

Blackett, P.

1984-01-01

An extract from Blackett's Nobel Prize speech of 1948, this recounts the work done by the author on particle tracks in a Wilson cloud chamber in 1932 at the Cavendish Laboratory, Cambridge. In particular he studied the energetic particles in cosmic rays using a cloud chamber and camera. The improvements to the equipment are recounted and photographs of cosmic ray showers taken with it are shown. (UK)

Cloud chamber development for didactic use

International Nuclear Information System (INIS)

Straube, B; Carrillo, M; Mangussi J

2012-01-01

The goal of this project was the design and construction of an Expansion Cloud Chamber from daily use material in order to make visible during a lesson, the trajectories of particles emitted by a radioactive material (author)

Radon diffusion chamber

International Nuclear Information System (INIS)

Pretzsch, G.; Boerner, E.; Lehmann, R.; Sarenio, O.

1986-01-01

The invention relates to the detection of radioactive gases emitting alpha particles like radon, thoron and their alpha-decaying daughters by means of a diffusion chamber with a passive detector, preferably with a solid state track detector. In the chamber above and towards the detector there is a single metallized electret with negative polarity. The distance between electret and detector corresponds to the range of the alpha particles of radon daughters in air at the most. The electret collects the positively charged daughters and functions as surface source. The electret increases the sensitivity by the factor 4

Radon progeny distribution in cylindrical diffusion chambers

International Nuclear Information System (INIS)

Pressyanov, Dobromir S.

2008-01-01

An algorithm to model the diffusion of radioactive decay chain atoms is presented. Exact mathematical solutions in cylindrical geometry are given. They are used to obtain expressions for the concentrations of 222 Rn progeny atoms in the volume and deposited on the wall surface in cylindrical diffusion chambers. The dependence of volume fractions of 222 Rn progeny and chamber sensitivity on the coefficient of diffusion of 222 Rn progeny atoms in air is modeled.

How to build a cloud chamber?; Comment realiser une chambre a bouillard?

Energy Technology Data Exchange (ETDEWEB)

Mariaud, C. [Lycee Rene Descartes, 37000 Tours (France)

2012-01-15

The cloud chamber had its heyday in the first half of last century and allowed the discovery of new particles such as the anti-electron, the muon and the neutral and the charged kaon. The bubble chamber replaced it in the mid fifties. This article recalls the principle of the cloud chamber and shows, in a detailed way, how to proceed to build one with on-the-shelf materials. This design is based on the use of isopropanol whose liquefaction through the form of droplets materializes the track of the particle and on the use of combined Peltier cells (instead of CO{sub 2} snow) to cool the chamber. This cloud chamber has been successfully used in schools to observe particles mainly electrons, alphas and muons generated by cosmic rays. (A.C.)

Laser-filament-induced snow formation in a subsaturated zone in a cloud chamber: experimental and theoretical study.

Science.gov (United States)

Ju, Jingjing; Sun, Haiyi; Sridharan, Aravindan; Wang, Tie-Jun; Wang, Cheng; Liu, Jiansheng; Li, Ruxin; Xu, Zhizhan; Chin, See Leang

2013-12-01

1 kHz, 2 mJ, 45 fs, 800 nm laser pulses were fired into a laboratory diffusion cloud chamber through a subsaturated zone (relative humidity ∼73%, T ∼ 4.3 °C). After 60 min of laser irradiation, an oval-shaped snow pile was observed right below the filament center and weighed ∼12.0 mg. The air current velocity at the edge of the vortices was estimated to be ∼16.5 cm/s. Scattering scenes recorded from the side show that filament-induced turbulence were formed inside the cloud chamber with two vortices below the filament. Two-dimensional simulations of the air flow motion in two cross sections of the cloud chamber confirm that the turbulent vortices exist below the filament. Based upon this simulation, we deduce that the vortices indeed have a three-dimensional elliptical shape. Hence, we propose that inside vortices where the humidity was supersaturated or saturated the condensation nuclei, namely, HNO(3), N(2)(+), O(2)(+) and other aerosols and impurities, were activated and grew in size. Large-sized particles would eventually be spun out along the fast moving direction towards the cold plate and formed an oval-shaped snow pile at the end.

The User-friendly On-Line Diffusion Chamber

CERN Document Server

Aviles Acosta, Jaime

2015-01-01

The On-Line Diffusion Chamber is a stand-alone apparatus built to carry out short-live radiotracer diffusion studies. The availability of the on-demand production of isotopes in the ISOLDE facility, and the design of the apparatus to streamline the implantation process, annealing treatment, ion gun ablation with a tape transport system, and radiation intensity measurement with a Ge gamma detector all in the same apparatus, gives the On-Line Diffusion Chamber a unique ability to studies with short-lived radioisotopes or isomer states that are not possible in any other facility in the world.

Satellite retrieval of cloud condensation nuclei concentrations by using clouds as CCN chambers

Science.gov (United States)

Rosenfeld, Daniel; Zheng, Youtong; Hashimshoni, Eyal; Pöhlker, Mira L.; Jefferson, Anne; Pöhlker, Christopher; Yu, Xing; Zhu, Yannian; Liu, Guihua; Yue, Zhiguo; Fischman, Baruch; Li, Zhanqing; Giguzin, David; Goren, Tom; Artaxo, Paulo; Pöschl, Ulrich

2016-01-01

Quantifying the aerosol/cloud-mediated radiative effect at a global scale requires simultaneous satellite retrievals of cloud condensation nuclei (CCN) concentrations and cloud base updraft velocities (Wb). Hitherto, the inability to do so has been a major cause of high uncertainty regarding anthropogenic aerosol/cloud-mediated radiative forcing. This can be addressed by the emerging capability of estimating CCN and Wb of boundary layer convective clouds from an operational polar orbiting weather satellite. Our methodology uses such clouds as an effective analog for CCN chambers. The cloud base supersaturation (S) is determined by Wb and the satellite-retrieved cloud base drop concentrations (Ndb), which is the same as CCN(S). Validation against ground-based CCN instruments at Oklahoma, at Manaus, and onboard a ship in the northeast Pacific showed a retrieval accuracy of ±25% to ±30% for individual satellite overpasses. The methodology is presently limited to boundary layer not raining convective clouds of at least 1 km depth that are not obscured by upper layer clouds, including semitransparent cirrus. The limitation for small solar backscattering angles of <25° restricts the satellite coverage to ∼25% of the world area in a single day. PMID:26944081

Measurement of optical blurring in a turbulent cloud chamber

Science.gov (United States)

Packard, Corey D.; Ciochetto, David S.; Cantrell, Will H.; Roggemann, Michael C.; Shaw, Raymond A.

2016-10-01

Earth's atmosphere can significantly impact the propagation of electromagnetic radiation, degrading the performance of imaging systems. Deleterious effects of the atmosphere include turbulence, absorption and scattering by particulates. Turbulence leads to blurring, while absorption attenuates the energy that reaches imaging sensors. The optical properties of aerosols and clouds also impact radiation propagation via scattering, resulting in decorrelation from unscattered light. Models have been proposed for calculating a point spread function (PSF) for aerosol scattering, providing a method for simulating the contrast and spatial detail expected when imaging through atmospheres with significant aerosol optical depth. However, these synthetic images and their predicating theory would benefit from comparison with measurements in a controlled environment. Recently, Michigan Technological University (MTU) has designed a novel laboratory cloud chamber. This multiphase, turbulent "Pi Chamber" is capable of pressures down to 100 hPa and temperatures from -55 to +55°C. Additionally, humidity and aerosol concentrations are controllable. These boundary conditions can be combined to form and sustain clouds in an instrumented laboratory setting for measuring the impact of clouds on radiation propagation. This paper describes an experiment to generate mixing and expansion clouds in supersaturated conditions with salt aerosols, and an example of measured imagery viewed through the generated cloud is shown. Aerosol and cloud droplet distributions measured during the experiment are used to predict scattering PSF and MTF curves, and a methodology for validating existing theory is detailed. Measured atmospheric inputs will be used to simulate aerosol-induced image degradation for comparison with measured imagery taken through actual cloud conditions. The aerosol MTF will be experimentally calculated and compared to theoretical expressions. The key result of this study is the

Laser-filamentation-induced condensation and snow formation in a cloud chamber.

Science.gov (United States)

Ju, Jingjing; Liu, Jiansheng; Wang, Cheng; Sun, Haiyi; Wang, Wentao; Ge, Xiaochun; Li, Chuang; Chin, See Leang; Li, Ruxin; Xu, Zhizhan

2012-04-01

Using 1 kHz, 9 mJ femtosecond laser pulses, we demonstrate laser-filamentation-induced spectacular snow formation in a cloud chamber. An intense updraft of warm moist air is generated owing to the continuous heating by the high-repetition filamentation. As it encounters the cold air above, water condensation and large-sized particles spread unevenly across the whole cloud chamber via convection and cyclone like action on a macroscopic scale. This indicates that high-repetition filamentation plays a significant role in macroscopic laser-induced water condensation and snow formation.

Diffusion and deposition of the Schooner clouds

Energy Technology Data Exchange (ETDEWEB)

Crawford, Todd V [Lawrence Radiation Laboratory, University of California, Livermore, CA (United States)

1970-05-01

Schooner was a 31-kt nuclear cratering experiment done as part of the U.S. Atomic Energy Commission's Plowshare Program. Detonation was at 0800 PST on December 8, 1968 at the Nevada Test Site. The resulting cloud had ceased its dynamic growth by about H+4 min. Two distinct parts, a base surge and a main cloud, were evident. Thereafter, further cloud growth was by diffusion and fallout as the cloud moved downwind. Aircraft sampling of the cloud at H+12.5 min revealed that the main cloud part contained about 10 times as much radioactivity as the base surge part. Later aircraft data, local fallout field measurements, and airborne particle size data indicate that the H+12.5-min cloud burdens, primarily the tungsten isotopes, were depleted by a factor of about 2, due to fallout, over the next few hours. The remaining airborne cloud burdens for each cloud were used as input to diffusion calculations. Calculated main cloud center concentrations using observed cloud sizes, cloud burdens, and meteorology agree with measurements to better than a factor of 2 over 1 1/2 days. These postshot calculations and data are about a factor of 3 higher than calculations done preshot. Base surge calculations are consistent with available data to within about a factor of 4, but the data needed to perform as complete an analysis as was done for the main cloud do not exist. Fallout, as distinguished from deposition of nonfalling debris, was important to a distance of about 500 km for the main cloud and to a distance of about 100 km for the base surge. At distances closer to ground zero, diffusion calculations under-predicted ground level concentration and deposition, but an isotopically scaled external gross gamma fallout calculation was within about a factor of 3 of the data. At larger distances downwind for the base surge, ground level exposure rate calculations and deposition for a variety of nuclides agree to within about a factor of 3 of measurements. (author)

Evaluation of tecniques for controlling UF6 release clouds in the GAT environmental chamber

International Nuclear Information System (INIS)

Lux, C.J.

1982-01-01

Studies designed to characterize the reaction between UF 6 and atmospheric moisture, evaluate environmental variables of UF 6 cloud formation and ultimate cloud fate, and UF 6 release cloud control procedure have been conducted in the 1200 cu. ft. GAT environmental chamber. In earlier chamber experiments, 30 separate UF 6 release tests indicated that variations of atmospheric conditions and sample sizes had no significant effect on UO 2 F 2 particle size distribution, release cloud formation, or cloud settling rates. During the past year, numerous procedures have been evaluated for accelerating UF 6 cloud knockdown in a series of 37 environmental chamber releases. Knockdown procedures included: coarse water spray; air jet; steam spray (electrostatically charged and uncharged); carbon dioxide; Freon-12; fine water mist (uncharged); boric acid mist (charged and uncharged); and an ionized dry air stream. UF 6 hydrolysis cloud settling rates monitored by a laser/powermeter densitometer, indicated the relative effectiveness of various cloud knockdown techniques. Electrostatically charged boric acid/water mist, and electrostatically ionized dry air were both found to be very effective, knocking down the UO 2 F 2 release cloud particles in two to five minutes. Work to adapt these knockdown techniques for use under field conditions is continuing, taking into account recovery of the released uranium as well as nuclear criticality constraints

Explosion-induced combustion of hydrocarbon clouds in a chamber

International Nuclear Information System (INIS)

Neuwald, P; Reichenbach, H; Kuhl, A L

2001-01-01

The interaction of the detonation of a solid HE-charge with a non-premixed cloud of hydro-carbon fuel in a chamber was studied in laboratory experiments. Soap bubbles filled with a flammable gas were subjected to the blast wave created by the detonation of PETN-charges (0.2 g < mass < 0.5 g). The dynamics of the combustion system were investigated by means of high-speed photography and measurement of the quasi-static chamber pressure

Comparing contact and immersion freezing from continuous flow diffusion chambers

Directory of Open Access Journals (Sweden)

B. Nagare

2016-07-01

Full Text Available Ice nucleating particles (INPs in the atmosphere are responsible for glaciating cloud droplets between 237 and 273 K. Different mechanisms of heterogeneous ice nucleation can compete under mixed-phase cloud conditions. Contact freezing is considered relevant because higher ice nucleation temperatures than for immersion freezing for the same INPs were observed. It has limitations because its efficiency depends on the number of collisions between cloud droplets and INPs. To date, direct comparisons of contact and immersion freezing with the same INP, for similar residence times and concentrations, are lacking. This study compares immersion and contact freezing efficiencies of three different INPs. The contact freezing data were obtained with the ETH CoLlision Ice Nucleation CHamber (CLINCH using 80 µm diameter droplets, which can interact with INPs for residence times of 2 and 4 s in the chamber. The contact freezing efficiency was calculated by estimating the number of collisions between droplets and particles. Theoretical formulations of collision efficiencies gave too high freezing efficiencies for all investigated INPs, namely AgI particles with 200 nm electrical mobility diameter, 400 and 800 nm diameter Arizona Test Dust (ATD and kaolinite particles. Comparison of freezing efficiencies by contact and immersion freezing is therefore limited by the accuracy of collision efficiencies. The concentration of particles was 1000 cm−3 for ATD and kaolinite and 500, 1000, 2000 and 5000 cm−3 for AgI. For concentrations  <  5000 cm−3, the droplets collect only one particle on average during their time in the chamber. For ATD and kaolinite particles, contact freezing efficiencies at 2 s residence time were smaller than at 4 s, which is in disagreement with a collisional contact freezing process but in accordance with immersion freezing or adhesion freezing. With “adhesion freezing”, we refer to a contact nucleation

Diffusion and scattering in multifractal clouds

Energy Technology Data Exchange (ETDEWEB)

Lovejoy, S. [McGill Univ., Montreal, Quebec (Canada); Schertzer, D. [Universite Pierre et Marie Curie, Paris (France); Waston, B. [St. Lawrence Univ., Canton, NY (United States)] [and others

1996-04-01

This paper describes investigations of radiative properties of multifractal clouds using two different approaches. In the first, diffusion is considered by examining the scaling properties of one dimensional random walks on media with multifractal diffusivities. The second approach considers the scattering statistics associated with radiative transport.

A review of optical measurements at the aerosol and cloud chamber AIDA

International Nuclear Information System (INIS)

Wagner, Robert; Linke, Claudia; Naumann, Karl-Heinz; Schnaiter, Martin; Vragel, Marlen; Gangl, Martin; Horvath, Helmuth

2009-01-01

This paper provides a survey of recent studies on the optical properties of aerosol and cloud particles that have been conducted at the AIDA facility of Forschungszentrum Karlsruhe (Aerosol Interactions and Dynamics in the Atmosphere). Reflecting the broad accessible temperature range of the AIDA chamber which extends from ambient temperature down to 183 K, the investigations feature a broad diversity of research topics, such as the wavelength-dependence of the specific absorption cross sections of soot and mineral dust aerosols at room temperature, depolarization and infrared extinction measurements of ice crystal clouds generated at temperatures below 235 K, and the optical properties of polar stratospheric cloud constituents whose formation was studied in chamber experiments at temperatures well below 200 K. After reviewing the AIDA research activity of the past decade and introducing the optical instrumentation of the AIDA facility, this paper presents illustrative examples of ongoing and already published work on optical measurements of soot aerosols, mineral dust particles, and ice crystal clouds.

Corona discharge induced snow formation in a cloud chamber.

Science.gov (United States)

Ju, Jingjing; Wang, Tie-Jun; Li, Ruxin; Du, Shengzhe; Sun, Haiyi; Liu, Yonghong; Tian, Ye; Bai, Yafeng; Liu, Yaoxiang; Chen, Na; Wang, Jingwei; Wang, Cheng; Liu, Jiansheng; Chin, S L; Xu, Zhizhan

2017-09-18

Artificial rainmaking is in strong demand especially in arid regions. Traditional methods of seeding various Cloud Condensation Nuclei (CCN) into the clouds are costly and not environment friendly. Possible solutions based on ionization were proposed more than 100 years ago but there is still a lack of convincing verification or evidence. In this report, we demonstrated for the first time the condensation and precipitation (or snowfall) induced by a corona discharge inside a cloud chamber. Ionic wind was found to have played a more significant role than ions as extra CCN. In comparison with another newly emerging femtosecond laser filamentation ionization method, the snow precipitation induced by the corona discharge has about 4 orders of magnitude higher wall-plug efficiency under similar conditions.

Beam Measurements of a CLOUD (Cosmics Leaving OUtdoor Droplets) Chamber

CERN Document Server

Kirkby, Jasper

2001-01-01

A striking correlation has recently been observed between global cloud cover and the flux of incident cosmic rays. The effect of natural variations in the cosmic ray flux is large, causing estimated changes in the Earth's energy radiation balance that are comparable to those attributed to greenhouse gases from the burning of fossil fuels since the Industrial Revolution. However a direct link between cosmic rays and cloud formation has not been unambiguously established. We therefore propose to experimentally measure cloud (water droplet) formation under controlled conditions in a test beam at CERN with a CLOUD chamber, duplicating the conditions prevailing in the troposphere. These data, which have never been previously obtained, will allow a detailed understanding of the possible effects of cosmic rays on clouds and confirm, or otherwise, a direct link between cosmic rays, global cloud cover and the Earth's climate. The measurements will, in turn, allow more reliable calculations to be made of the residual e...

OH+ IN DIFFUSE MOLECULAR CLOUDS

International Nuclear Information System (INIS)

Porras, A. J.; Federman, S. R.; Welty, D. E.; Ritchey, A. M.

2014-01-01

Near ultraviolet observations of OH + and OH in diffuse molecular clouds reveal a preference for different environments. The dominant absorption feature in OH + arises from a main component seen in CH + (that with the highest CH + /CH column density ratio), while OH follows CN absorption. This distinction provides new constraints on OH chemistry in these clouds. Since CH + detections favor low-density gas with small fractions of molecular hydrogen, this must be true for OH + as well, confirming OH + and H 2 O + observations with the Herschel Space Telescope. Our observed correspondence indicates that the cosmic ray ionization rate derived from these measurements pertains to mainly atomic gas. The association of OH absorption with gas rich in CN is attributed to the need for a high enough density and molecular fraction before detectable amounts are seen. Thus, while OH + leads to OH production, chemical arguments suggest that their abundances are controlled by different sets of conditions and that they coexist with different sets of observed species. Of particular note is that non-thermal chemistry appears to play a limited role in the synthesis of OH in diffuse molecular clouds

CN radical in diffuse interstellar clouds

International Nuclear Information System (INIS)

Federman, S.R.; Danks, A.C.; Lambert, D.L.

1984-01-01

A survey of 15 lines of sight for the CN B 2 Σ + --X 2 Σ + interstellar absorption lines shows that the CN column density in diffuse interstellar clouds follows the relation log N(CN)proportionalm log N(H 2 ), where mroughly-equal3. This result is reproduced by a reaction network in which CN is produced primarily from C 2 by the neutral-neutral reaction C 2 +N → CN+C, and photodissociation is the main destruction pathway for the neutral molecules CH, C 2 , and CN. The CN radical is the first molecular species observed in diffuse clouds that requires a neutral-neutral reaction for its formation in the gas phase. The network also reproduces the observed ratio N(CN)/N(H 2 )

Cloud chamber experiments on the origin of ice crystal complexity in cirrus clouds

Directory of Open Access Journals (Sweden)

M. Schnaiter

2016-04-01

Full Text Available This study reports on the origin of small-scale ice crystal complexity and its influence on the angular light scattering properties of cirrus clouds. Cloud simulation experiments were conducted at the AIDA (Aerosol Interactions and Dynamics in the Atmosphere cloud chamber of the Karlsruhe Institute of Technology (KIT. A new experimental procedure was applied to grow and sublimate ice particles at defined super- and subsaturated ice conditions and for temperatures in the −40 to −60 °C range. The experiments were performed for ice clouds generated via homogeneous and heterogeneous initial nucleation. Small-scale ice crystal complexity was deduced from measurements of spatially resolved single particle light scattering patterns by the latest version of the Small Ice Detector (SID-3. It was found that a high crystal complexity dominates the microphysics of the simulated clouds and the degree of this complexity is dependent on the available water vapor during the crystal growth. Indications were found that the small-scale crystal complexity is influenced by unfrozen H2SO4 / H2O residuals in the case of homogeneous initial ice nucleation. Angular light scattering functions of the simulated ice clouds were measured by the two currently available airborne polar nephelometers: the polar nephelometer (PN probe of Laboratoire de Métérologie et Physique (LaMP and the Particle Habit Imaging and Polar Scattering (PHIPS-HALO probe of KIT. The measured scattering functions are featureless and flat in the side and backward scattering directions. It was found that these functions have a rather low sensitivity to the small-scale crystal complexity for ice clouds that were grown under typical atmospheric conditions. These results have implications for the microphysical properties of cirrus clouds and for the radiative transfer through these clouds.

Assessment of pathogen survival potential during managed aquifer recharge with diffusion chambers.

Science.gov (United States)

Sidhu, J P S; Toze, S

2012-09-01

To evaluate the efficacy of using in situ diffusion chambers for pathogen decay studies in the aquifer. A comparative microbial inactivation study was carried out in groundwater by seeding selected pathogens and indicators in laboratory microcosms and Teflon diffusion chambers (in situ) fitted with 0.010- and 0.025-μm pore-size membranes. The results have shown that there is a difference in the decay rates obtained from the laboratory microcosms and in situ diffusion chambers for several pathogens. The results suggest that the use of laboratory microcosms to determine pathogen decay during the Managed Aquifer Recharge (MAR) may lead to underestimation of decay of adenovirus and Cryptosporidium and subsequent inaccurate assessment of the required residence time in the aquifer for pathogens to be removed from the recharged water. The decay rate of two indicator bacteria, Salmonella enterica and adenovirus, was found to be significantly slower (t-test, P aquifers. Reliable assessment of potential public health risks from the presence of pathogens in groundwater is essential for proper management of the MAR schemes. The results of this study suggest that in situ assessment of pathogen survival potential in diffusion chambers provided more reliable data for pathogen risk assessment and subsequent risk mitigation plans for MAR schemes. © 2012 The Authors Journal of Applied Microbiology © 2012 The Society for Applied Microbiology.

Design of an ionization diffusion chamber detector

International Nuclear Information System (INIS)

Sugiarto, S.

1976-01-01

Prototype of an Ionization Diffusion Chamber detector has been made. It is a silindrical glass, 20 cm in diameter, 13,5 cm in height, air gas filled, operated at room pressure and room temperature at the top of this instrument while for the box temperature dry ice (CO 2 solid) temperature is used. This detector is ready for seeing alpha and beta particle tracks. (author)

Decoherence and Determinism in a One-Dimensional Cloud-Chamber Model

Science.gov (United States)

Sparenberg, Jean-Marc; Gaspard, David

2018-03-01

The hypothesis (Sparenberg et al. in EPJ Web Conf 58:01016, [1]. https://doi.org/10.1051/epjconf/20135801016) that the particular linear tracks appearing in the measurement of a spherically-emitting radioactive source in a cloud chamber are determined by the (random) positions of atoms or molecules inside the chamber is further explored in the framework of a recently established one-dimensional model (Carlone et al. Comm Comput Phys 18:247, [2]. https://doi.org/10.4208/cicp.270814.311214a). In this model, meshes of localized spins 1/2 play the role of the cloud-chamber atoms and the spherical wave is replaced by a linear superposition of two wave packets moving from the origin to the left and to the right, evolving deterministically according to the Schrödinger equation. We first revisit these results using a time-dependent approach, where the wave packets impinge on a symmetric two-sided detector. We discuss the evolution of the wave function in the configuration space and stress the interest of a non-symmetric detector in a quantum-measurement perspective. Next we use a time-independent approach to study the scattering of a plane wave on a single-sided detector. Preliminary results are obtained, analytically for the single-spin case and numerically for up to 8 spins. They show that the spin-excitation probabilities are sometimes very sensitive to the parameters of the model, which corroborates the idea that the measurement result could be determined by the atom positions. The possible origin of decoherence and entropy increase in future models is finally discussed.

A basic radiation-education method using a handy-type cloud chamber and natural radiation sources

International Nuclear Information System (INIS)

Kushita, K. N.

2010-10-01

Nuclear human resources development becomes increasingly important due to the world trend of expanding nuclear energy utilization in this century. At the Nuclear Human Resource Development Center of the Japan Atomic Energy Agency, many kinds of nuclear and radiation education have been conducted consistently and continuously through its half-century history though having several organizational changes. High level education is required for the specialists of nuclear technology including nuclear power plants operators and engineers, while basic knowledge on nuclear energy and, specially, on radiations and radioisotopes should be given to school students and public. Besides lectures on radiation and radioisotopes, some basic experiments are useful to understand what are radiations and radioisotopes. One of such basic experiments is the cloud chamber experiment. It is a great fun and excitement even for small children as one can actually see the radiation tracks by his/her naked eyes at hand. While there are many types of cloud chambers, we have developed a new-type cloud chamber to use for the radiation education and training s. Using the new-type cloud chamber, we have further developed a new method of this experiment so that the participants can more deeply understand the phenomena and the nature of radiation and radioisotopes. In this method, using a radiation source of natural uranium ore and gaseous radiation source containing Rn-220 obtained from thorium-containing material, they not only observe the radiation tracks but also measure the length and count the number of the tracks. Then they can calculate the energy of the radiation (alpha ray) and can estimate the half-life of the radioisotope (Rn-220). This method can be applied for high-school and general university students as well as for the public as a useful and effective method in the radiation education. (Author)

A basic radiation-education method using a handy-type cloud chamber and natural radiation sources

Energy Technology Data Exchange (ETDEWEB)

Kushita, K. N., E-mail: Kushita.kouhei@iaea.go.j [Japan Atomic Energy Agency, Nuclear Human Resource Development Center, 2-4 Shirakata-Shirane, Tokai, Naka, Ibaraki 309-1195 (Japan)

2010-10-15

Nuclear human resources development becomes increasingly important due to the world trend of expanding nuclear energy utilization in this century. At the Nuclear Human Resource Development Center of the Japan Atomic Energy Agency, many kinds of nuclear and radiation education have been conducted consistently and continuously through its half-century history though having several organizational changes. High level education is required for the specialists of nuclear technology including nuclear power plants operators and engineers, while basic knowledge on nuclear energy and, specially, on radiations and radioisotopes should be given to school students and public. Besides lectures on radiation and radioisotopes, some basic experiments are useful to understand what are radiations and radioisotopes. One of such basic experiments is the cloud chamber experiment. It is a great fun and excitement even for small children as one can actually see the radiation tracks by his/her naked eyes at hand. While there are many types of cloud chambers, we have developed a new-type cloud chamber to use for the radiation education and training s. Using the new-type cloud chamber, we have further developed a new method of this experiment so that the participants can more deeply understand the phenomena and the nature of radiation and radioisotopes. In this method, using a radiation source of natural uranium ore and gaseous radiation source containing Rn-220 obtained from thorium-containing material, they not only observe the radiation tracks but also measure the length and count the number of the tracks. Then they can calculate the energy of the radiation (alpha ray) and can estimate the half-life of the radioisotope (Rn-220). This method can be applied for high-school and general university students as well as for the public as a useful and effective method in the radiation education. (Author)

Sensitivity test of tumor cell to anticancer drug using diffusion chamber

Energy Technology Data Exchange (ETDEWEB)

Soejima, S [Hirosaki Univ., Aomori (Japan). School of Medicine

1978-11-01

The diffusion chamber method and xenogeneic transplantation of human cancer cells in rats were studied clinically to test the sensitivity of these cells to anticancer drugs. The growth of Hirosaki sarcoma in a diffusion chamber inserted in to Wistar rats was influenced by the difference in tumor cell counts in the chamber. The growth rate in the chamber inserted in to the subcutaneous tissue was more constant than in the abdominal cavity, but the degree of proliferation of tumor cells in the abdominal cavity was more than in the subcutaneous tissue. Sarcoma and solid type sarcoma were affected by mitomycin C (MMC). The effect was greater in dd-mice than in Donryu rats. Solid type Yoshida sarcoma inserted in to the subcutaneous tissue of Donryu rat was not affected by MMC. The degree of sensitivity of methylcholanthrene induced tumor cells, inserted in to the subcutaneous tissue of Donryu rats, to MMC differed according to various conditions of the hosts. Clinically, the influences of anticancer drugs on human cancer cells inserted in to the subcutaneous tissue of /sup 60/Co-irradiated Donryu rats were observed. There were various grades of sensitivity of gastric cancer cells to anticancer drugs. MMC was effective in 53% of the cases, Cyclophosphamide in 40%, 5-FU in 54%, cytosine arabinoside in 32%, and FT-207 in 57%. Twenty-seven percent were not affected by anticancer drugs. On histological examination, tubular adenocarcinoma cells had a high sensitivity to anticancer drugs, while poorly differentiated adenocarcinoma cells had a low sensitive. Anticancer drugs selected according to the sensitivity of human cancer cells had a marked effective on advanced cancer cells. The diffusion chamber method was useful in determining the degree of bone marrow toxicity of anticancer drugs.

Local Interactions of Hydrometeors by Diffusion in Mixed-Phase Clouds

Science.gov (United States)

Baumgartner, Manuel; Spichtinger, Peter

2017-04-01

Mixed-phase clouds, containing both ice particles and liquid droplets, are important for the Earth-Atmosphere system. They modulate the radiation budget by a combination of albedo effect and greenhouse effect. In contrast to liquid water clouds, the radiative impact of clouds containing ice particles is still uncertain. Scattering and absorption highly depends in microphysical properties of ice crystals, e.g. size and shape. In addition, most precipitation on Earth forms via the ice phase. Thus, better understanding of ice processes as well as their representation in models is required. A key process for determining shape and size of ice crystals is diffusional growth. Diffusion processes in mixed-phase clouds are highly uncertain; in addition they are usually highly simplified in cloud models, especially in bulk microphysics parameterizations. The direct interaction between cloud droplets and ice particles, due to spatial inhomogeneities, is ignored; the particles can only interact via their environmental conditions. Local effects as supply of supersaturation due to clusters of droplets around ice particles are usually not represented, although they form the physical basis of the Wegener-Bergeron-Findeisen process. We present direct numerical simulations of the interaction of single ice particles and droplets, especially their local competition for the available water vapor. In addition, we show an approach to parameterize local interactions by diffusion. The suggested parameterization uses local steady-state solutions of the diffusion equations for water vapor for an ice particle as well as a droplet. The individual solutions are coupled together to obtain the desired interaction. We show some results of the scheme as implemented in a parcel model.

Penetration of Cosmic Rays into Dense Molecular Clouds: Role of Diffuse Envelopes

Science.gov (United States)

Ivlev, A. V.; Dogiel, V. A.; Chernyshov, D. O.; Caselli, P.; Ko, C.-M.; Cheng, K. S.

2018-03-01

A flux of cosmic rays (CRs) propagating through a diffuse ionized gas can excite MHD waves, thus generating magnetic disturbances. We propose a generic model of CR penetration into molecular clouds through their diffuse envelopes, and identify the leading physical processes controlling their transport on the way from a highly ionized interstellar medium to the dense interior of the cloud. The model allows us to describe a transition between a free streaming of CRs and their diffusive propagation, determined by the scattering on the self-generated disturbances. A self-consistent set of equations, governing the diffusive transport regime in an envelope and the MHD turbulence generated by the modulated CR flux, is characterized by two dimensionless numbers. We demonstrate a remarkable mutual complementarity of different mechanisms leading to the onset of the diffusive regime, which results in a universal energy spectrum of the modulated CRs. In conclusion, we briefly discuss implications of our results for several fundamental astrophysical problems, such as the spatial distribution of CRs in the Galaxy as well as the ionization, heating, and chemistry in dense molecular clouds. This paper is dedicated to the memory of Prof. Vadim Tsytovich.

Experimental project - Cloud chamber

International Nuclear Information System (INIS)

Nour, Elena; Quinchard, Gregory; Soudon, Paul

2015-01-01

This document reports an academic experimental project dealing with the general concepts of radioactivity and their application to the cloud room experiment. The author first recalls the history of the design and development of a cloud room, and some definitions and characteristics of cosmic radiation, and proposes a description of the principle and physics of a cloud room. The second part is a theoretical one, and addresses the involved particles, the origins of electrons, and issues related to the transfer of energy (Bremsstrahlung effect, Bragg peak). The third part reports the experimental work with the assessment of a cloud droplet radius, the identification of a trace for each particle (alphas and electrons), and the study of the magnetic field deviation

HIGH-ENERGY COSMIC-RAY DIFFUSION IN MOLECULAR CLOUDS: A NUMERICAL APPROACH

International Nuclear Information System (INIS)

Fatuzzo, M.; Melia, F.; Todd, E.; Adams, F. C.

2010-01-01

The propagation of high-energy cosmic rays (CRs) through giant molecular clouds constitutes a fundamental process in astronomy and astrophysics. The diffusion of CRs through these magnetically turbulent environments is often studied through the use of energy-dependent diffusion coefficients, although these are not always well motivated theoretically. Now, however, it is feasible to perform detailed numerical simulations of the diffusion process computationally. While the general problem depends upon both the field structure and particle energy, the analysis may be greatly simplified by dimensionless analysis. That is, for a specified purely turbulent field, the analysis depends almost exclusively on a single parameter-the ratio of the maximum wavelength of the turbulent field cells to the particle gyration radius. For turbulent magnetic fluctuations superimposed over an underlying uniform magnetic field, particle diffusion depends on a second dimensionless parameter that characterizes the ratio of the turbulent to uniform magnetic field energy densities. We consider both of these possibilities and parametrize our results to provide simple quantitative expressions that suitably characterize the diffusion process within molecular cloud environments. Doing so, we find that the simple scaling laws often invoked by the high-energy astrophysics community to model CR diffusion through such regions appear to be fairly robust for the case of a uniform magnetic field with a strong turbulent component, but are only valid up to ∼50 TeV particle energies for a purely turbulent field. These results have important consequences for the analysis of CR processes based on TeV emission spectra associated with dense molecular clouds.

Characterisation of organic contaminants in the CLOUD chamber at CERN

CERN Document Server

Schnitzhofer, R; Breitenlechner, M; Jud, W; Heinritzi, M; Menezes, L-P; Duplissy, J; Guida, R; Haider, S; Kikby, J; Mathot, S; Minginette, P; Onnela, A; Walther, H; Wasem, A; Hansel, A; CLOUD Team

2014-01-01

The CLOUD experiment (Cosmics Leaving OUtdoor Droplets) investigates the nucleation of new particles and how this process is influenced by galactic cosmic rays in an electropolished, stainless-steel environmental chamber at CERN (European Organization for Nuclear Research). Since volatile organic compounds (VOCs) can act as precursor gases for nucleation and growth of particles, great efforts have been made to keep their unwanted background levels as low as possible and to quantify them. In order to be able to measure a great set of VOCs simultaneously in the low parts per trillion (pptv) range, proton-transfer-reaction mass spectrometry (PTR-MS) was used. Initially the total VOC background concentration strongly correlated with ozone in the chamber and ranged from 0.1 to 7 parts per billion (ppbv). Plastic used as sealing material in the ozone generator was found to be a major VOC source. Especially oxygen-containing VOCs were generated together with ozone. These parts were replaced by stainless steel after ...

MAGNETIZATION OF CLOUD CORES AND ENVELOPES AND OTHER OBSERVATIONAL CONSEQUENCES OF RECONNECTION DIFFUSION

International Nuclear Information System (INIS)

Lazarian, A.; Esquivel, A.; Crutcher, R.

2012-01-01

Recent observational results for magnetic fields in molecular clouds reviewed by Crutcher seem to be inconsistent with the predictions of the ambipolar diffusion theory of star formation. These include the measured decrease in mass to flux ratio between envelopes and cores, the failure to detect any self-gravitating magnetically subcritical clouds, the determination of the flat probability distribution function (PDF) of the total magnetic field strengths implying that there are many clouds with very weak magnetic fields, and the observed scaling B∝ρ 2/3 that implies gravitational contraction with weak magnetic fields. We consider the problem of magnetic field evolution in turbulent molecular clouds and discuss the process of magnetic field diffusion mediated by magnetic reconnection. For this process that we termed 'reconnection diffusion', we provide a simple physical model and explain that this process is inevitable in view of the present-day understanding of MHD turbulence. We address the issue of the expected magnetization of cores and envelopes in the process of star formation and show that reconnection diffusion provides an efficient removal of magnetic flux that depends only on the properties of MHD turbulence in the core and the envelope. We show that as the amplitude of turbulence as well as the scale of turbulent motions decrease from the envelope to the core of the cloud, the diffusion of the magnetic field is faster in the envelope. As a result, the magnetic flux trapped during the collapse in the envelope is being released faster than the flux trapped in the core, resulting in much weaker fields in envelopes than in cores, as observed. We provide simple semi-analytical model calculations which support this conclusion and qualitatively agree with the observational results. Magnetic reconnection is also consistent with the lack of subcritical self-gravitating clouds, with the observed flat PDF of field strengths, and with the scaling of field strength

MAGNETIZATION OF CLOUD CORES AND ENVELOPES AND OTHER OBSERVATIONAL CONSEQUENCES OF RECONNECTION DIFFUSION

Energy Technology Data Exchange (ETDEWEB)

Lazarian, A. [Astronomy Department, University of Wisconsin, Madison, WI 53706 (United States); Esquivel, A. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-543, 04510 Mexico D.F. (Mexico); Crutcher, R. [Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 W. Green Street, Urbana, IL 61801 (United States)

2012-10-01

Recent observational results for magnetic fields in molecular clouds reviewed by Crutcher seem to be inconsistent with the predictions of the ambipolar diffusion theory of star formation. These include the measured decrease in mass to flux ratio between envelopes and cores, the failure to detect any self-gravitating magnetically subcritical clouds, the determination of the flat probability distribution function (PDF) of the total magnetic field strengths implying that there are many clouds with very weak magnetic fields, and the observed scaling B{proportional_to}{rho}{sup 2/3} that implies gravitational contraction with weak magnetic fields. We consider the problem of magnetic field evolution in turbulent molecular clouds and discuss the process of magnetic field diffusion mediated by magnetic reconnection. For this process that we termed 'reconnection diffusion', we provide a simple physical model and explain that this process is inevitable in view of the present-day understanding of MHD turbulence. We address the issue of the expected magnetization of cores and envelopes in the process of star formation and show that reconnection diffusion provides an efficient removal of magnetic flux that depends only on the properties of MHD turbulence in the core and the envelope. We show that as the amplitude of turbulence as well as the scale of turbulent motions decrease from the envelope to the core of the cloud, the diffusion of the magnetic field is faster in the envelope. As a result, the magnetic flux trapped during the collapse in the envelope is being released faster than the flux trapped in the core, resulting in much weaker fields in envelopes than in cores, as observed. We provide simple semi-analytical model calculations which support this conclusion and qualitatively agree with the observational results. Magnetic reconnection is also consistent with the lack of subcritical self-gravitating clouds, with the observed flat PDF of field strengths, and

submitter Phase transition observations and discrimination of small cloud particles by light polarization in expansion chamber experiments

CERN Document Server

Nichman, Leonid; Järvinen, Emma; Ignatius, Karoliina; Höppel, Niko Florian; Dias, Antonio; Heinritzi, Martin; Simon, Mario; Tröstl, Jasmin; Wagner, Andrea Christine; Wagner, Robert; Williamson, Christina; Yan, Chao; Connolly, Paul James; Dorsey, James Robert; Duplissy, Jonathan; Ehrhart, Sebastian; Frege, Carla; Gordon, Hamish; Hoyle, Christopher Robert; Kristensen, Thomas Bjerring; Steiner, Gerhard; McPherson Donahue, Neil; Flagan, Richard; Gallagher, Martin William; Kirkby, Jasper; Möhler, Ottmar; Saathoff, Harald; Schnaiter, Martin; Stratmann, Frank; Tomé, António

2016-01-01

Cloud microphysical processes involving the ice phase in tropospheric clouds are among the major uncertainties in cloud formation, weather, and general circulation models. The detection of aerosol particles, liquid droplets, and ice crystals, especially in the small cloud particle-size range below 50 μm, remains challenging in mixed phase, often unstable environments. The Cloud Aerosol Spectrometer with Polarization (CASPOL) is an airborne instrument that has the ability to detect such small cloud particles and measure the variability in polarization state of their backscattered light. Here we operate the versatile Cosmics Leaving OUtdoor Droplets (CLOUD) chamber facility at the European Organization for Nuclear Research (CERN) to produce controlled mixed phase and other clouds by adiabatic expansions in an ultraclean environment, and use the CASPOL to discriminate between different aerosols, water, and ice particles. In this paper, optical property measurements of mixed-phase clouds and viscous secondary ...

Design of a new multi-phase experimental simulation chamber for atmospheric photosmog, aerosol and cloud chemistry research

Directory of Open Access Journals (Sweden)

J. Wang

2011-11-01

Full Text Available A new simulation chamber has been built at the Interuniversitary Laboratory of Atmospheric Systems (LISA. The CESAM chamber (French acronym for Experimental Multiphasic Atmospheric Simulation Chamber is designed to allow research in multiphase atmospheric (photo- chemistry which involves both gas phase and condensed phase processes including aerosol and cloud chemistry. CESAM has the potential to carry out variable temperature and pressure experiments under a very realistic artificial solar irradiation. It consists of a 4.2 m³ stainless steel vessel equipped with three high pressure xenon arc lamps which provides a controlled and steady environment. Initial characterization results, all carried out at 290–297 K under dry conditions, concerning lighting homogeneity, mixing efficiency, ozone lifetime, radical sources, NO_y wall reactivity, particle loss rates, background PM, aerosol formation and cloud generation are given. Photolysis frequencies of NO₂ and O₃ related to chamber radiation system were found equal to (4.2 × 10⁻³ s⁻¹ for J_NO2 and (1.4 × 10⁻⁵ s⁻¹ for J_O¹D which is comparable to the solar radiation in the boundary layer. An auxiliary mechanism describing NO_y wall reactions has been developed. Its inclusion in the Master Chemical Mechanism allowed us to adequately model the results of experiments on the photo-oxidation of propene-NO_x-Air mixtures. Aerosol yields for the α-pinene + O₃ system chosen as a reference were determined and found in good agreement with previous studies. Particle lifetime in the chamber ranges from 10 h to 4 days depending on particle size distribution which indicates that the chamber can provide high quality data on aerosol aging processes and their effects. Being evacuable, it is possible to generate in this new chamber

Survival and ice nucleation activity of bacteria as aerosols in a cloud simulation chamber

Science.gov (United States)

Amato, P.; Joly, M.; Schaupp, C.; Attard, E.; Möhler, O.; Morris, C. E.; Brunet, Y.; Delort, A.-M.

2015-06-01

The residence time of bacterial cells in the atmosphere is predictable by numerical models. However, estimations of their aerial dispersion as living entities are limited by a lack of information concerning survival rates and behavior in relation to atmospheric water. Here we investigate the viability and ice nucleation (IN) activity of typical atmospheric ice nucleation active bacteria (Pseudomonas syringae and P. fluorescens) when airborne in a cloud simulation chamber (AIDA, Karlsruhe, Germany). Cell suspensions were sprayed into the chamber and aerosol samples were collected by impingement at designated times over a total duration of up to 18 h, and at some occasions after dissipation of a cloud formed by depressurization. Aerosol concentration was monitored simultaneously by online instruments. The cultivability of airborne cells decreased exponentially over time with a half-life time of 250 ± 30 min (about 3.5 to 4.5 h). In contrast, IN activity remained unchanged for several hours after aerosolization, demonstrating that IN activity was maintained after cell death. Interestingly, the relative abundance of IN active cells still airborne in the chamber was strongly decreased after cloud formation and dissipation. This illustrates the preferential precipitation of IN active cells by wet processes. Our results indicate that from 106 cells aerosolized from a surface, one would survive the average duration of its atmospheric journey estimated at 3.4 days. Statistically, this corresponds to the emission of 1 cell that achieves dissemination every ~ 33 min m-2 of cultivated crops fields, a strong source of airborne bacteria. Based on the observed survival rates, depending on wind speed, the trajectory endpoint could be situated several hundreds to thousands of kilometers from the emission source. These results should improve the representation of the aerial dissemination of bacteria in numeric models.

Laboratory and Cloud Chamber Studies of Formation Processes and Properties of Atmospheric Ice Particles

Science.gov (United States)

Leisner, T.; Abdelmonem, A.; Benz, S.; Brinkmann, M.; Möhler, O.; Rzesanke, D.; Saathoff, H.; Schnaiter, M.; Wagner, R.

2009-04-01

The formation of ice in tropospheric clouds controls the evolution of precipitation and thereby influences climate and weather via a complex network of dynamical and microphysical processes. At higher altitudes, ice particles in cirrus clouds or contrails modify the radiative energy budget by direct interaction with the shortwave and longwave radiation. In order to improve the parameterisation of the complex microphysical and dynamical processes leading to and controlling the evolution of tropospheric ice, laboratory experiments are performed at the IMK Karlsruhe both on a single particle level and in the aerosol and cloud chamber AIDA. Single particle experiments in electrodynamic levitation lend themselves to the study of the interaction between cloud droplets and aerosol particles under extremely well characterized and static conditions in order to obtain microphysical parameters as freezing nucleation rates for homogeneous and heterogeneous ice formation. They also allow the observation of the freezing dynamics and of secondary ice formation and multiplication processes under controlled conditions and with very high spatial and temporal resolution. The inherent droplet charge in these experiments can be varied over a wide range in order to assess the influence of the electrical state of the cloud on its microphysics. In the AIDA chamber on the other hand, these processes are observable under the realistic dynamic conditions of an expanding and cooling cloud- parcel with interacting particles and are probed simultaneously by a comprehensive set of analytical instruments. By this means, microphysical processes can be studied in their complex interplay with dynamical processes as for example coagulation or particle evaporation and growth via the Bergeron - Findeisen process. Shortwave scattering and longwave absorption properties of the nucleating and growing ice crystals are probed by in situ polarised laser light scattering measurements and infrared extinction

A Monte Carlo study of radon detection in cylindrical diffusion chambers

Energy Technology Data Exchange (ETDEWEB)

Rickards, Jorge, E-mail: rickards@fisica.unam.m [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Circuito de la Investigacion Cientifica, Ciudad Universitaria, Delegacion Coyoacan, 04520 Mexico, D.F. (Mexico); Golzarri, Jose-Ignacio, E-mail: golzarri@fisica.unam.m [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Circuito de la Investigacion Cientifica, Ciudad Universitaria, Delegacion Coyoacan, 04520 Mexico, D.F. (Mexico); Espinosa, Guillermo, E-mail: espinosa@fisica.unam.m [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Circuito de la Investigacion Cientifica, Ciudad Universitaria, Delegacion Coyoacan, 04520 Mexico, D.F. (Mexico)

2010-05-15

The functioning of radon diffusion chambers was studied using the Monte Carlo code RAMMX developed here. The alpha particles from radon are assumed randomly produced in the volume of the cylinder, and those from the progeny are assumed to originate randomly at the cylindrical surface. The energy spectrum, the distribution of incident angles, and the distribution of path lengths of the alpha particles on the detector were obtained. These quantities vary depending on input parameters such as initial alpha particle energy, radius and depth of the diffusion chamber, detector size and atmospheric pressure. The calculated energy spectrum for both {sup 222}Rn and {sup 220}Rn was compared with experiment, permitting the identification of each peak and its origin, and a better understanding of radon monitoring. Three aspects not considered in previous calculations are progeny alphas coming from surfaces of the monitor, taking into account the atmospheric pressure, and including the isotope {sup 220}Rn.

A low-pressure cloud chamber to study the spatial distribution of ionizations

International Nuclear Information System (INIS)

Hodges, D.C.; Marshall, M.

1977-01-01

To further the understanding of the biological effects of radiation a knowledge of the spatial distribution of ionizations in small volumes is required. A cloud chamber capable of resolving the droplets formed on individual ions in the tracks of low-energy electrons has been constructed. It is made to high-vacuum specifications and contains a mixture of permanent gases and vapours, unsaturated before expansion, at a total pressure of 10 kPa. Condensation efficiencies close to 100% are obtained without significant background from condensation on uncharged particles and molecular aggregates. This paper describes the chamber, associated equipment and method of operation and discusses the performance of the system. Photographs of the droplets produced from the interaction of low-energy X-rays in the chamber gas for various modes of operation are presented. The mean energy loss per ion pair for electrons produced by the interaction of Al X-rays in the chamber gas (8130 Pa H 2 , 700 Pa C 2 H 5 OH, 690 Pa H 2 O, 400 Pa He, 70 Pa air) has been measured as 29.8 +- 0.7 eV per ion pair compared with a calculated value of 29.6 +- 0.4 eV per ion pair. (author)

Investigation into electron cloud effects in the International Linear Collider positron damping ring

Energy Technology Data Exchange (ETDEWEB)

Crittenden, J. A.; Conway, J.; Dugan, G. F.; Palmer, M. A.; Rubin, D. L.; Shanks, J.; Sonnad, K. G.; Boon, L.; Harkay, K.; Ishibashi, T.; Furman, M. A.; Guiducci, S.; Pivi, M. T. F.; Wang, L.

2014-03-01

We report modeling results for electron cloud buildup and instability in the International Linear Collider positron damping ring. Updated optics, wiggler magnets, and vacuum chamber designs have recently been developed for the 5 GeV, 3.2-km racetrack layout. An analysis of the synchrotron radiation profile around the ring has been performed, including the effects of diffuse and specular photon scattering on the interior surfaces of the vacuum chamber. The results provide input to the cloud buildup simulations for the various magnetic field regions of the ring. The modeled cloud densities thus obtained are used in the instability threshold calculations. We conclude that the mitigation techniques employed in this model will suffice to allow operation of the damping ring at the design operational specifications

Numerical simulations of mixing conditions and aerosol dynamics in the CERN CLOUD chamber

CERN Document Server

Voigtländer, J; Rondo, L; Kürten, A; Stratmann, F

2012-01-01

To study the effect of galactic cosmic rays on aerosols and clouds, the Cosmics Leaving OUtdoor Droplets (CLOUD) project was established. Experiments are carried out at a 26.1 m3 tank at CERN (Switzerland). In the experiments, the effect of ionizing radiation on H2SO4 particle formation and growth is investigated. To evaluate the experimental configuration, the experiment was simulated using a coupled multidimensional computational fluid dynamics (CFD) – particle model. In the model the coupled fields of gas/vapor species, temperature, flow velocity and particle properties were computed to investigate mixing state and mixing times of the CLOUD tank's contents. Simulation results show that a 1-fan configuration, as used in first experiments, may not be sufficient to ensure a homogeneously mixed chamber. To mix the tank properly, two fans and sufficiently high fan speeds are necessary. The 1/e response times for instantaneous changes of wall temperature and saturation ratio were found to be in the order of fe...

Semi-empirical approach for calibration of CR-39 detectors in diffusion chambers for radon measurements

International Nuclear Information System (INIS)

Pereyra A, P.; Lopez H, M. E.; Palacios F, D.; Sajo B, L.; Valdivia, P.

2016-10-01

Simulated and measured calibration of PADC detectors is given for cylindrical diffusion chambers employed in environmental radon measurements. The method is based on determining the minimum alpha energy (E min ), average critical angle (<Θ c >), and fraction of 218 Po atoms; the volume of the chamber (f 1 ), are compared to commercially available devices. Radon concentration for exposed detectors is obtained from induced track densities and the well-established calibration coefficient for NRPB monitor. Calibration coefficient of a PADC detector in a cylindrical diffusion chamber of any size is determined under the same chemical etching conditions and track analysis methodology. In this study the results of numerical examples and comparison between experimental calibration coefficients and simulation purpose made code. Results show that the developed method is applicable when uncertainties of 10% are acceptable. (Author)

Simple computation of reaction–diffusion processes on point clouds

KAUST Repository

Macdonald, Colin B.

2013-05-20

The study of reaction-diffusion processes is much more complicated on general curved surfaces than on standard Cartesian coordinate spaces. Here we show how to formulate and solve systems of reaction-diffusion equations on surfaces in an extremely simple way, using only the standard Cartesian form of differential operators, and a discrete unorganized point set to represent the surface. Our method decouples surface geometry from the underlying differential operators. As a consequence, it becomes possible to formulate and solve rather general reaction-diffusion equations on general surfaces without having to consider the complexities of differential geometry or sophisticated numerical analysis. To illustrate the generality of the method, computations for surface diffusion, pattern formation, excitable media, and bulk-surface coupling are provided for a variety of complex point cloud surfaces.

Simple computation of reaction–diffusion processes on point clouds

KAUST Repository

Macdonald, Colin B.; Merriman, Barry; Ruuth, Steven J.

2013-01-01

The study of reaction-diffusion processes is much more complicated on general curved surfaces than on standard Cartesian coordinate spaces. Here we show how to formulate and solve systems of reaction-diffusion equations on surfaces in an extremely simple way, using only the standard Cartesian form of differential operators, and a discrete unorganized point set to represent the surface. Our method decouples surface geometry from the underlying differential operators. As a consequence, it becomes possible to formulate and solve rather general reaction-diffusion equations on general surfaces without having to consider the complexities of differential geometry or sophisticated numerical analysis. To illustrate the generality of the method, computations for surface diffusion, pattern formation, excitable media, and bulk-surface coupling are provided for a variety of complex point cloud surfaces.

Formaldehyde in the Diffuse Interstellar Cloud MBM40

Science.gov (United States)

Joy, Mackenzie; Magnani, Loris A.

2018-06-01

MBM40, a high-latitude molecular cloud, has been extensively studied using different molecular tracers. It appears that MBM40 is composed of a relatively dense, helical filament embedded in a more diffuse substrate of low density molecular gas. In order to study the transition between the two regimes, this project presents the first high-resolution mapping of MBM40 using the 110-111 hyperfine transition of formaldehyde (H2CO) at 4.83 GHz. We used H2CO spectra obtained with the Arecibo telescope more than a decade ago to construct this map. The results can be compared to previous maps made from the CO(1-0) transition to gain further understanding of the structure of the cloud. The intensity of the H2CO emission was compared to the CO emission. Although a correlation exists between the H2CO and CO emissivity, there seems to be a saturation of H2CO line strength for stronger CO emissivity. This is probably a radiative transfer effect of the CO emission. We have also found that the velocity dispersion of H2CO in the lower ridge of the cloud is significantly lower than in the rest of the cloud. This may indicate that this portion of the cloud is a coherent structure (analogous to an eddy) in a turbulent flow.

Semi-empirical approach for calibration of CR-39 detectors in diffusion chambers for radon measurements

Energy Technology Data Exchange (ETDEWEB)

Pereyra A, P.; Lopez H, M. E. [Pontificia Universidad Catolica del Peru, Av. Universitaria 1801, San Miguel Lima 32 (Peru); Palacios F, D.; Sajo B, L. [Universidad Simon Bolivar, Laboratorio de Fisica Nuclear, Apartado 89000 Caracas (Venezuela, Bolivarian Republic of); Valdivia, P., E-mail: ppereyr@pucp.edu.pe [Universidad Nacional de Ingenieria, Av. Tupac Amaru s/n, Rimac, Lima 25 (Peru)

2016-10-15

Simulated and measured calibration of PADC detectors is given for cylindrical diffusion chambers employed in environmental radon measurements. The method is based on determining the minimum alpha energy (E{sub min}), average critical angle (<Θ{sub c}>), and fraction of {sup 218}Po atoms; the volume of the chamber (f{sub 1}), are compared to commercially available devices. Radon concentration for exposed detectors is obtained from induced track densities and the well-established calibration coefficient for NRPB monitor. Calibration coefficient of a PADC detector in a cylindrical diffusion chamber of any size is determined under the same chemical etching conditions and track analysis methodology. In this study the results of numerical examples and comparison between experimental calibration coefficients and simulation purpose made code. Results show that the developed method is applicable when uncertainties of 10% are acceptable. (Author)

Development of a turn-key cloud chamber in collaboration with non-academic science enthusiasts

Science.gov (United States)

Muenkel, Jessica; Harrington, Meghan; Bellis, Matthew; Waldman, Ariel; Bergey, Nathan; Cooper, Ivan; Bombosch, Juliane

2014-03-01

Science Hack Day is an event that brings together scientists and science enthusiasts for 24 hours to ``hack'' a science project. These events serve two purposes. The first and most obvious is to provide a structured environment for science outreach. Academics and researchers have the opportunity for ``boots-on-the-ground'' interactions with the general public. The second purpose, though more challenging, is to enable science enthusiasts to donate their skills so that they are able to push back to educators and researchers in a fashion that that benefits their work. We discuss our experiences at the 2013 San Francisco Science Hack Day at the California Academy of Sciences. We worked with attendees of the conference to create a cloud chamber that worked with Peltier thermocoolers, rather than dry ice. In this fashion, we educated attendees about radiation and particle physics, while also benefitting from the experience and knowledge of the attendees in constructing the device. This ``turn-key'' cloud chamber is now in use at Siena College as an outreach and educational device. The properties of this device and the story of its construction will be presented. Representing CMS.

Reliability Analysis Based on a Jump Diffusion Model with Two Wiener Processes for Cloud Computing with Big Data

Directory of Open Access Journals (Sweden)

Yoshinobu Tamura

2015-06-01

Full Text Available At present, many cloud services are managed by using open source software, such as OpenStack and Eucalyptus, because of the unification management of data, cost reduction, quick delivery and work savings. The operation phase of cloud computing has a unique feature, such as the provisioning processes, the network-based operation and the diversity of data, because the operation phase of cloud computing changes depending on many external factors. We propose a jump diffusion model with two-dimensional Wiener processes in order to consider the interesting aspects of the network traffic and big data on cloud computing. In particular, we assess the stability of cloud software by using the sample paths obtained from the jump diffusion model with two-dimensional Wiener processes. Moreover, we discuss the optimal maintenance problem based on the proposed jump diffusion model. Furthermore, we analyze actual data to show numerical examples of dependability optimization based on the software maintenance cost considering big data on cloud computing.

A long-term time series of global and diffuse photosynthetically active radiation in the Mediterranean: interannual variability and cloud effects

Directory of Open Access Journals (Sweden)

P. Trisolino

2018-06-01

Full Text Available Measurements of global and diffuse photosynthetically active radiation (PAR have been carried out on the island of Lampedusa, in the central Mediterranean Sea, since 2002. PAR is derived from observations made with multi-filter rotating shadowband radiometers (MFRSRs by comparison with a freshly calibrated PAR sensor and by relying on the on-site Langley plots. In this way, a long-term calibrated record covering the period 2002–2016 is obtained and is presented in this work. The monthly mean global PAR peaks in June, with about 160 W m−2, while the diffuse PAR reaches 60 W m−2 in spring or summer. The global PAR displays a clear annual cycle with a semi amplitude of about 52 W m−2. The diffuse PAR annual cycle has a semi amplitude of about 12 W m−2. A simple method to retrieve the cloud-free PAR global and diffuse irradiances in days characterized by partly cloudy conditions has been implemented and applied to the dataset. This method allows retrieval of the cloud-free evolution of PAR and calculation of the cloud radiative effect, CRE, for downwelling PAR. The cloud-free monthly mean global PAR reaches 175 W m−2 in summer, while the diffuse PAR peaks at about 40 W m−2. The cloud radiative effect, CRE, on global and diffuse PAR is calculated as the difference between all-sky and cloud-free measurements. The annual average CRE is about −14.7 W m−2 for the global PAR and +8.1 W m−2 for the diffuse PAR. The smallest CRE is observed in July, due to the high cloud-free condition frequency. Maxima (negative for the global, and positive for the diffuse component occur in March–April and in October, due to the combination of elevated PAR irradiances and high occurrence of cloudy conditions. Summer clouds appear to be characterized by a low frequency of occurrence, low altitude, and low optical thickness, possibly linked to the peculiar marine boundary layer structure. These properties also contribute

Magnetic diffusion and ionization fractions in dense molecular clouds: The role of charged grains

International Nuclear Information System (INIS)

Elmegreen, B.G.

1979-01-01

The ionization fraction is determined for dense molecular clouds by considering charge exchange, dissociative recombination, radiative recombination, and collisions between grains and charged species. The inclusion of grains tends to lower the ionization fraction for a given cosmic-ray ionization rate zeta and metal depletion delta. The observed values of the ionization fractions in dense cloud cores (i.e., -8 ) are obtained for reasonable values of zeta=10 -17 s -1 and delta=0.1.For temperatures less than 30 K, each grain alternates in charge between -e and 0. The resulting motion of the grains in a self-graviting cloud that contains a magnetic field will be periodic; their response to electromagnetic forces will depend on their instantaneous charge. This complex motion is calculated in order to determine the average viscous force between the grains and the neutral molecules in the cloud. The grain-neutral viscous force combines with the ion-neutral viscous force to regulate the motion of the neutral molecules relative to the magnetic field. The resultant The result neutral drift leads to a diffusion of the magnetic field out of the cloud. The time scale for this diffusion is calculated. Grain-related viscous forces dominate ion-related forces for ionization fractions less than 5 x 10 -8 . The magnetic diffusion time in a self-gravitating cloud that is supported by an internal magnetic field is shown to be at least 10 times larger thanthe free-fall time even when the ionization fraction is much less than 10 -8

Observational Constraints for Modeling Diffuse Molecular Clouds

Science.gov (United States)

Federman, S. R.

2014-02-01

Ground-based and space-borne observations of diffuse molecular clouds suggest a number of areas where further improvements to modeling efforts is warranted. I will highlight those that have the widest applicability. The range in CO fractionation caused by selective isotope photodissociation, in particular the large 12C16O/13C16O ratios observed toward stars in Ophiuchus, is not reproduced well by current models. Our ongoing laboratory measurements of oscillator strengths and predissociation rates for Rydberg transitions in CO isotopologues may help clarify the situtation. The CH+ abundance continues to draw attention. Small scale structure seen toward ζ Per may provide additional constraints on the possible synthesis routes. The connection between results from optical transitions and those from radio and sub-millimeter wave transitions requires further effort. A study of OH+ and OH toward background stars reveals that these species favor different environments. This brings to focus the need to model each cloud along the line of sight separately, and to allow the physical conditions to vary within an individual cloud, in order to gain further insight into the chemistry. Now that an extensive set of data on molecular excitation is available, the models should seek to reproduce these data to place further constraints on the modeling results.

Laser-filamentation-induced water condensation and snow formation in a cloud chamber filled with different ambient gases.

Science.gov (United States)

Liu, Yonghong; Sun, Haiyi; Liu, Jiansheng; Liang, Hong; Ju, Jingjing; Wang, Tiejun; Tian, Ye; Wang, Cheng; Liu, Yi; Chin, See Leang; Li, Ruxin

2016-04-04

We investigated femtosecond laser-filamentation-induced airflow, water condensation and snow formation in a cloud chamber filled respectively with air, argon and helium. The mass of snow induced by laser filaments was found being the maximum when the chamber was filled with argon, followed by air and being the minimum with helium. We also discussed the mechanisms of water condensation in different gases. The results show that filaments with higher laser absorption efficiency, which result in higher plasma density, are beneficial for triggering intense airflow and thus more water condensation and precipitation.

THE IMPLICATIONS OF A HIGH COSMIC-RAY IONIZATION RATE IN DIFFUSE INTERSTELLAR CLOUDS

International Nuclear Information System (INIS)

Indriolo, Nick; Fields, Brian D.; McCall, Benjamin J.

2009-01-01

Diffuse interstellar clouds show large abundances of H + 3 which can only be maintained by a high ionization rate of H 2 . Cosmic rays are the dominant ionization mechanism in this environment, so the large ionization rate implies a high cosmic-ray flux, and a large amount of energy residing in cosmic rays. In this paper, we find that the standard propagated cosmic-ray spectrum predicts an ionization rate much lower than that inferred from H + 3 . Low-energy (∼10 MeV) cosmic rays are the most efficient at ionizing hydrogen, but cannot be directly detected; consequently, an otherwise unobservable enhancement of the low-energy cosmic-ray flux offers a plausible explanation for the H + 3 results. Beyond ionization, cosmic rays also interact with the interstellar medium by spalling atomic nuclei and exciting atomic nuclear states. These processes produce the light elements Li, Be, and B, as well as gamma-ray lines. To test the consequences of an enhanced low-energy cosmic-ray flux, we adopt two physically motivated cosmic-ray spectra which by construction reproduce the ionization rate inferred in diffuse clouds, and investigate the implications of these spectra on dense cloud ionization rates, light-element abundances, gamma-ray fluxes, and energetics. One spectrum proposed here provides an explanation for the high ionization rate seen in diffuse clouds while still appearing to be broadly consistent with other observables, but the shape of this spectrum suggests that supernovae remnants may not be the predominant accelerators of low-energy cosmic rays.

Aerosol-cloud feedbacks in a turbulent environment: Laboratory measurements representative of conditions in boundary layer clouds

Science.gov (United States)

Cantrell, W. H.; Chandrakar, K. K.; Karki, S.; Kinney, G.; Shaw, R.

2017-12-01

Many of the climate impacts of boundary layer clouds are modulated by aerosol particles. As two examples, their interactions with incoming solar and upwelling terrestrial radiation and their propensity for precipitation are both governed by the population of aerosol particles upon which the cloud droplets formed. In turn, clouds are the primary removal mechanism for aerosol particles smaller than a few micrometers and larger than a few nanometers. Aspects of these interconnected phenomena are known in exquisite detail (e.g. Köhler theory), but other parts have not been as amenable to study in the laboratory (e.g. scavenging of aerosol particles by cloud droplets). As a complicating factor, boundary layer clouds are ubiquitously turbulent, which introduces fluctuations in the water vapor concentration and temperature, which govern the saturation ratio which mediates aerosol-cloud interactions. We have performed laboratory measurements of aerosol-cloud coupling and feedbacks, using Michigan Tech's Pi Chamber (Chang et al., 2016). In conditions representative of boundary layer clouds, our data suggest that the lifetime of most interstitial particles in the accumulation mode is governed by cloud activation - particles are removed from the Pi Chamber when they activate and settle out of the chamber as cloud droplets. As cloud droplets are removed, these interstitial particles activate until the initially polluted cloud cleans itself and all particulates are removed from the chamber. At that point, the cloud collapses. Our data also indicate that smaller particles, Dp defined through the use of the Dämkohler number, the ratio of the characteristic turbulence timescale to the cloud's microphysical response time. Chang, K., et al., 2016. A laboratory facility to study gas-aerosol-cloud interactions in a turbulent environment: The Π Chamber. Bull. Amer. Meteor. Soc., doi:10.1175/BAMS-D-15-00203.1

Technical Note: A numerical test-bed for detailed ice nucleation studies in the AIDA cloud simulation chamber

Directory of Open Access Journals (Sweden)

R. J. Cotton

2007-01-01

Full Text Available The AIDA (Aerosol Interactions and Dynamics in the Atmosphere aerosol and cloud chamber of Forschungszentrum Karlsruhe can be used to test the ice forming ability of aerosols. The AIDA chamber is extensively instrumented including pressure, temperature and humidity sensors, and optical particle counters. Expansion cooling using mechanical pumps leads to ice supersaturation conditions and possible ice formation. In order to describe the evolving chamber conditions during an expansion, a parcel model was modified to account for diabatic heat and moisture interactions with the chamber walls. Model results are shown for a series of expansions where the initial chamber temperature ranged from −20°C to −60°C and which used desert dust as ice forming nuclei. During each expansion, the initial formation of ice particles was clearly observed. For the colder expansions there were two clear ice nucleation episodes. In order to test the ability of the model to represent the changing chamber conditions and to give confidence in the observations of chamber temperature and humidity, and ice particle concentration and mean size, ice particles were simply added as a function of time so as to reproduce the observations of ice crystal concentration. The time interval and chamber conditions over which ice nucleation occurs is therefore accurately known, and enables the model to be used as a test bed for different representations of ice formation.

Large Interstellar Polarisation Survey. II. UV/optical study of cloud-to-cloud variations of dust in the diffuse ISM

Science.gov (United States)

Siebenmorgen, R.; Voshchinnikov, N. V.; Bagnulo, S.; Cox, N. L. J.; Cami, J.; Peest, C.

2018-03-01

It is well known that the dust properties of the diffuse interstellar medium exhibit variations towards different sight-lines on a large scale. We have investigated the variability of the dust characteristics on a small scale, and from cloud-to-cloud. We use low-resolution spectro-polarimetric data obtained in the context of the Large Interstellar Polarisation Survey (LIPS) towards 59 sight-lines in the Southern Hemisphere, and we fit these data using a dust model composed of silicate and carbon particles with sizes from the molecular to the sub-micrometre domain. Large (≥6 nm) silicates of prolate shape account for the observed polarisation. For 32 sight-lines we complement our data set with UVES archive high-resolution spectra, which enable us to establish the presence of single-cloud or multiple-clouds towards individual sight-lines. We find that the majority of these 35 sight-lines intersect two or more clouds, while eight of them are dominated by a single absorbing cloud. We confirm several correlations between extinction and parameters of the Serkowski law with dust parameters, but we also find previously undetected correlations between these parameters that are valid only in single-cloud sight-lines. We find that interstellar polarisation from multiple-clouds is smaller than from single-cloud sight-lines, showing that the presence of a second or more clouds depolarises the incoming radiation. We find large variations of the dust characteristics from cloud-to-cloud. However, when we average a sufficiently large number of clouds in single-cloud or multiple-cloud sight-lines, we always retrieve similar mean dust parameters. The typical dust abundances of the single-cloud cases are [C]/[H] = 92 ppm and [Si]/[H] = 20 ppm.

Diffusion chamber culture of mouse bone marrow cells, (1)

International Nuclear Information System (INIS)

Sigeta, Chiharu; Tanaka, Kimio; Kawakami, Masahito; Takahashi, Hiroshi; Ohkita, Takeshi

1980-01-01

Mouse bone marrow cells were cultured in diffusion chambers (DC) implanted in the peritoneal cavity of host mice. Host mice were subjected to (1) irradiation ( 60 Co 800 rad) and/or (2) phenylhydrazine induced anemia and then receiving irradiation ( 60 Co 600 rad). After culture periods of 3-7 days, the total number of cells in DC was increased. A marked increase in DC is due to the proliferation of granulocyte series. When host mice were subjected to anemia and irradiation, the start of cell proliferation in DC was delay about two days. On the whole, anemia and irradiation host reduced a little cell growth in DC. The number of immature granulocytes grown in DC in irradiated hosts or anemia and irradiated hosts increased and reached a plateu at day 5. During the plateu period, the proportions between immature and mature granulocytes in DC were kept constantly. The number of macrophages showed a two-phase increasing. Erythroid cells and lymphocytes rapidly disappeared from the chambers during 3 days. The number of erythroid cells was not significantly influenced even in anemia and irradiation hosts. (author)

A new laboratory facility to study the interactions of aerosols, cloud droplets/ice crystals, and trace gases in a turbulent environment: The Π Chamber

Science.gov (United States)

Cantrell, W. H., II; Chang, K.; Ciochetto, D.; Niedermeier, D.; Bench, J.; Shaw, R. A.

2014-12-01

A detailed understanding of gas-aerosol-cloud interaction within the turbulent atmosphere is of prime importance for an accurate understanding of Earth's climate system. As one example: While every cloud droplet began as an aerosol particle, not every aerosol particle becomes a cloud droplet. The particle to droplet transformation requires that the particle be exposed to some critical concentration of water vapor, which differs for different combinations of particle size and chemical composition. Similarly, the formation of ice particles in mixed phase clouds is also catalyzed by aerosol particles. Even in the simplest scenarios it is challenging to gain a full understanding of the aerosol activation and ice nucleation processes. At least two other factors contribute significantly to the complexity observed in the atmosphere. First, aerosols and cloud particles are not static entities, but are continuously interacting with their chemical environment, and therefore changing in their properties. Second, clouds are ubiquitously turbulent, so thermodynamic and compositional variables, such as water vapor or other trace gas concentrations, fluctuate in space and time. Indeed, the coupling between turbulence and microphysical processes is one of the major research challenges in cloud physics. We have developed a multiphase, turbulent reaction chamber, (dubbed the Π Chamber, after the internal volume of 3.14 cubic meters) designed to address the problems outlined above. It is capable of pressures ranging from sea level to ~ 100 mbar, and can sustain temperatures of +40 to -55 ºC. We can independently control the temperatures on the surfaces of three heat transfer zones. This allows us to establish a temperature gradient between the floor and ceiling inducing Rayleigh-Benard convection and inducing a turbulent environment. Interior surfaces are electropolished stainless steel to facilitate cleaning before and after chemistry experiments. At present, supporting

Cosmic-ray cloud-chamber contributions to the discovery of the strange particles in the decade 1947-1957

International Nuclear Information System (INIS)

Rochester, G.D.

1989-01-01

This paper looks at the discovery and investigation of strange particles in the 1950s and points to the importance of two factors in achieving this, namely, penetrating-shower selection and counter control in cloud chambers. Experiments at Pic-du-Mide are detailed as is the Bagneres de Bigorre conference and concludes with some of the work done on charged strange particles. (UK)

Loss of ions in cavity ionization chambers

International Nuclear Information System (INIS)

Takata, N.; Tran, N.T.; Kim, E.; Marsoem, P.; Kurosawa, T.; Koyama, Y.

2005-01-01

Ion losses due to initial recombination, volume recombination, and back diffusion were each determined by measurements and calculations for different size cylindrical ionization chambers and spherical ionization chambers. By measuring signal currents from these ionization chambers irradiated with 60 Co gamma rays, two groups of ion losses were obtained. (Group 1) Ion loss due to initial recombination and diffusion, which changes proportionally to the inverse of the voltage applied to the ionization chambers; (and group 2) ion loss due to volume recombination, which changes proportionally to the inverse of the square of the applied voltage. The diffusion loss was obtained separately by computing electric field distributions in the ionization chambers. It was found that diffusion loss is larger than initial recombination loss for the cylindrical ionization chambers and vise versa for the spherical ionization chambers

New Particle Formation in an Urban Atmosphere: The Role of Various Ingredients Investigated in the CLOUD Chamber

Science.gov (United States)

Baltensperger, U.; Xiao, M.; Hoyle, C.; Dada, L.; Garmash, O.; Stolzenburg, D.; Molteni, U.; Lehtipalo, K.; El-Haddad, I.; Dommen, J.

2017-12-01

Atmospheric aerosols play an important role on climate via aerosol-radiation interaction and aerosol-cloud interaction. The latter is strongly influenced by new particle formation (NPF). The physical and chemical mechanisms behind the NPF process are still under investigation. Great advancements were made in resolving chemical and physical mechanisms of NPF with a series of experiments conducted at the CLOUD (Cosmics Leaving Outdoor Droplets) chamber facility at CERN (Geneva, Switzerland), including binary nucleation of sulfuric acid - water, ternary nucleation of sulfuric acid - water with ammonia or dimethylamine as well as oxidation products (highly oxygenated molecules, HOMs) from biogenic precursors with and without the presence of sulfuric acid. Here, we investigate possible NPF mechanisms in urban atmospheres, where large populations are exposed to high aerosol concentrations; these mechanisms are still missing and are urgently needed. Urban atmospheres are highly polluted with high concentrations of SO2, ammonia, NOx and volatile organic vapors from anthropogenic activity as well as with high particle concentrations, which provide a high condensation sink for condensable gases. Aromatic hydrocarbons from industrial activities, traffic and residential combustion are present at high concentrations and contribute significantly to photochemical smog in the urban environment.The experiments were conducted at the CLOUD chamber facility during the CLOUD11 campaign in fall 2016. Three aromatic hydrocarbons were selected: toluene, 1,2,4-trimethylbenzene (1,2,4-TMB) and naphthalene (NPT). Experiments were also conducted with mixtures of the three aromatic hydrocarbons to better represent the urban atmosphere. All the experiments were conducted in the presence of sulfuric acid concentrations with or without the addition of ammonia and NOx. New particle formation rates and early growth rates derived for each precursor and their mixture, together with sulfuric acid and

The Carrier Gas Pressure Effect in a Laminar Flow Diffusion Chamber, Homogeneous Nucleation of n-Butanol in Helium

Czech Academy of Sciences Publication Activity Database

Hyvärinen, A-P.; Brus, David; Ždímal, Vladimír; Smolík, Jiří; Kulmala, M.; Viisanen, V.; Lihavainen, H.

2006-01-01

Roč. 124, č. 22 (2006), Art. No. 224304 ISSN 0021-9606 R&D Projects: GA AV ČR(CZ) IAA2076203 Institutional research plan: CEZ:AV0Z40720504 Keywords : supersaturated vapor * cloud chamber * background gas es Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.166, year: 2006

Digital simulation of an enrichment process for solutions by means of an advection-diffusion chamber

International Nuclear Information System (INIS)

Artucio, G.; Suarez, R.; Uruguay Catholic University)

1995-01-01

An ab-initio digital simulation of the space-time dynamics of the concentration field of a solute in an advection-diffusion chamber is done. Some questions related to the digital simulation of the concentration field using the analytical solution obtained in a previous paper are discussed

Investigation concerning the existence of quarks near the nuclei of great air showers with the help of a cloud chamber

International Nuclear Information System (INIS)

Wiemken, U.

1974-01-01

In order to compare the results of McCusker's (1969) experiment, this paper presents an experiment with improved technical details. For this purpose, a large cloud chamber in connection with the Kiel air shower set-up was available. First, the expected quark induced ionisation has been determined by a calibration measurement on minimum ionising muons. These data are in extremely good agreement with values from the literature. Then, measurements in air showers with a mean primary energy of 10 16 eV have been performed during an effective measuring time of 66 days. The mean distance from the nucleus amounts to about 9 m. In contradiction to the quark abundance of McCusker, which predicts six quarks for the Kiel set-up, no track was found with 'quark suspicion'. Some tracks with low droplet densities could be explained already in a preliminary stage of the evaluation by normal cloud chamber effects. (orig.) [de

submitter Modeling the thermodynamics and kinetics of sulfuric acid-dimethylamine-water nanoparticle growth in the CLOUD chamber

CERN Document Server

Ahlm, L; Schobesberger, S; Praplan, A P; Kim, J; Tikkanen, O -P; Lawler, M J; Smith, J N; Tröstl, J; Acosta Navarro, J C; Baltensperger, U; Bianchi, F; Donahue, N M; Duplissy, J; Franchin, A; Jokinen, T; Keskinen, H; Kirkby, J; Kürten, A; Laaksonen, A; Lehtipalo, K; Petäjä, T; Riccobono, F; Rissanen, M P; Rondo, L; Schallhart, S; Simon, M; Winkler, P M; Worsnop, D R; Virtanen, A; Riipinen, I

2016-01-01

Dimethylamine (DMA) has a stabilizing effect on sulfuric acid (SA) clusters, and the SA and DMA molecules and clusters likely play important roles in both aerosol particle formation and growth in the atmosphere. We use the monodisperse particle growth model for acid-base chemistry in nanoparticle growth (MABNAG) together with direct and indirect observations from the CLOUD4 and CLOUD7 experiments in the cosmics leaving outdoor droplets (CLOUD) chamber at CERN to investigate the size and composition evolution of freshly formed particles consisting of SA, DMA, and water as they grow to 20 nm in dry diameter. Hygroscopic growth factors are measured using a nano-hygroscopicity tandem differential mobility analyzer (nano-HTDMA), which combined with simulations of particle water uptake using the thermodynamic extended-aerosol inorganics model (E-AIM) constrain the chemical composition. MABNAG predicts a particle-phase ratio between DMA and SA molecules of 1.1–1.3 for a 2 nm particle and DMA gas-phase mixing ratio...

Chamber and Diffusive Based Carbon Flux Measurements in an Alaskan Arctic Ecosystem

Science.gov (United States)

Wilkman, E.; Oechel, W. C.; Zona, D.

2013-12-01

consumption, whereas chamber and eddy covariance methodologies only document net production from the surface. Also, the capability to measure spring, summer and fall chamber fluxes, and to continuously determine year-round CO2 and CH4 fluxes under even the most extreme weather conditions, allows an unprecedented level of data continuity and local spatial coverage. Comparison to a nearby eddy covariance tower measuring CO2 and CH4 fluxes with an LGR Fast Greenhouse Gas Analyzer add additional power to this set of measurements. Thus, inter-comparison between diffusive, chamber, and tower-based carbon fluxes should lend much insight into the spatial and temporal controls on carbon cycling in this ecosystem.

Simulated Field Trials Using an Indoor Aerosol Test Chamber

National Research Council Canada - National Science Library

Semler, D. D; Roth, A. P; Semler, K. A; Nolan, P. M

2004-01-01

.... In this method, the aerosol chamber control software manipulates circulation fan speeds, chamber vacuum and agent spray times to produce a simulated dynamic cloud within the aerosol test chamber...

Simulated Field Trials Using An Indoor Aerosol Test Chamber

National Research Council Canada - National Science Library

Semler, D. D; Roth, A. P; Semler, K. A; Nolan, P. M

2004-01-01

.... In this method, the aerosol chamber control software manipulates circulation fan speeds, chamber vacuum and agent spray times to produce a simulated dynamic cloud within the aerosol test chamber...

Radon exhalation rates corrected for leakage and back diffusion – Evaluation of radon chambers and radon sources with application to ceramic tile

Directory of Open Access Journals (Sweden)

M. Abo-Elmagd

2014-10-01

Full Text Available The natural radon decay, leakage and back diffusion are the main removal processes of radon from its container. Ignoring these processes leads to underestimate the measured value of radon related parameters like exhalation rate and radium content. This work is aimed to evaluate two different radon chambers through determining their leakage rate λv and evaluation of radon source by determine its back diffusion rate λb inside the evaluated radon chambers as well as a small sealed cup. Two different methods are adapted for measuring both the leakage rate and the back diffusion rate. The leakage rate can be determined from the initial slope of the radon decay curve or from the exponential fitting of the whole decay curve. This can be achieved if a continuous monitoring of radon concentration inside the chamber is available. Also, the back diffusion rate is measured by sealing the radon source in the chamber and used the initial slope of the buildup curve to determine λb and therefore the exhalation rate of the source. This method was compared with simple equation for λb based on the ratio of the source to the chamber volume. The obtained results are applied to ceramic tile as an important radon source in homes. The measurement is targeted the ceramic glaze before and after firing as well as the obtained tile after adhere the glaze on the tile main body. Also, six different tile brands from Egyptian market are subjected to the study for comparison.

The role of ions in new particle formation in the CLOUD chamber

Directory of Open Access Journals (Sweden)

R. Wagner

2017-12-01

Full Text Available The formation of secondary particles in the atmosphere accounts for more than half of global cloud condensation nuclei. Experiments at the CERN CLOUD (Cosmics Leaving OUtdoor Droplets chamber have underlined the importance of ions for new particle formation, but quantifying their effect in the atmosphere remains challenging. By using a novel instrument setup consisting of two nanoparticle counters, one of them equipped with an ion filter, we were able to further investigate the ion-related mechanisms of new particle formation. In autumn 2015, we carried out experiments at CLOUD on four systems of different chemical compositions involving monoterpenes, sulfuric acid, nitrogen oxides, and ammonia. We measured the influence of ions on the nucleation rates under precisely controlled and atmospherically relevant conditions. Our results indicate that ions enhance the nucleation process when the charge is necessary to stabilize newly formed clusters, i.e., in conditions in which neutral clusters are unstable. For charged clusters that were formed by ion-induced nucleation, we were able to measure, for the first time, their progressive neutralization due to recombination with oppositely charged ions. A large fraction of the clusters carried a charge at 1.5 nm diameter. However, depending on particle growth rates and ion concentrations, charged clusters were largely neutralized by ion–ion recombination before they grew to 2.5 nm. At this size, more than 90 % of particles were neutral. In other words, particles may originate from ion-induced nucleation, although they are neutral upon detection at diameters larger than 2.5 nm. Observations at Hyytiälä, Finland, showed lower ion concentrations and a lower contribution of ion-induced nucleation than measured at CLOUD under similar conditions. Although this can be partly explained by the observation that ion-induced fractions decrease towards lower ion concentrations, further investigations

Kinematical analysis with the Emulsion Cloud Chamber in the OPERA experiment

CERN Document Server

Di Capua, F

2010-01-01

The OPERA experiment aims at measuring for the first time neutrino oscil- lation in appearance mode through the detection of ni-tau in an almost pure niμ beam produced at CERN SPS (CNGS), 730 km far from the detector. The ni-tau appearance signal is identified through the measurement of the decay daughter particles of the " lepton produced in CC ni-tau interactions. Since the short-lived " particle has, at the energy of the beam, an average decay length shorter than a 1 mm, a micrometric detection resolution is needed. The OPERA appara- tus is hybrid, using nuclear emulsion as high precision tracker and electronic detectors for the time stamp, event localization in the target and muon recon- struction. The Emulsion Cloud Chamber technique fulfils the requirement of a microscopic resolution together with a large target mass. The kinematical analysis allowed by this technique is described.

Exact and near backscattering measurements of the linear depolarisation ratio of various ice crystal habits generated in a laboratory cloud chamber

Science.gov (United States)

Smith, Helen R.; Connolly, Paul J.; Webb, Ann R.; Baran, Anthony J.

2016-07-01

Ice clouds were generated in the Manchester Ice Cloud Chamber (MICC), and the backscattering linear depolarisation ratio, δ, was measured for a variety of habits. To create an assortment of particle morphologies, the humidity in the chamber was varied throughout each experiment, resulting in a range of habits from the pristine to the complex. This technique was repeated at three temperatures: -7 °C, -15 °C and -30 °C, in order to produce both solid and hollow columns, plates, sectored plates and dendrites. A linearly polarised 532 nm continuous wave diode laser was directed through a section of the cloud using a non-polarising 50:50 beam splitter. Measurements of the scattered light were taken at 178°, 179° and 180°, using a Glan-Taylor prism to separate the co- and cross-polarised components. The intensities of these components were measured using two amplified photodetectors and the ratio of the cross- to co-polarised intensities was measured to find the linear depolarisation ratio. In general, it was found that Ray Tracing over-predicts the linear depolarisation ratio. However, by creating more accurate particle models which better represent the internal structure of ice particles, discrepancies between measured and modelled results (based on Ray Tracing) were reduced.

Behavior of aerosols undergoing Brownian coagulation, Brownian diffusion and gravitational settling in a closed chamber

International Nuclear Information System (INIS)

Okuyama, Kikuo; Kousaka, Yasuo; Yoshida, Tetsuo

1976-01-01

The behavior of aerosols undergoing Brownian coagulation. Brownian diffusion and gravitational settling in a closed chamber was studied by solving the basic equation, the so-called population balance equation, numerically for a polydisperse aerosol system and analytically for a monodisperse system, and then the results were examined by experiment. In solving the basic equation, two dimensionless parameters, which are determined by the initial properties of an aerosol and the chamber dimension and also characterize the relative effects of Brownian coagulation and Brownian diffusion to gravitational settling, were introduced in order to generalize the behavior under arbitrary conditions. The calculated results, the time-dependent changes in particle number concentration and particle size distribution for a polydisperse system, were presented graphically by using the above two parameters. And further using these parameters, the domains of the three controlling factors were mapped to show the extent of each effect of these factors under various conditions for a monodisperse system. Some of the calculated results were compared with the experimental results obtained by the ultramicroscopic size analysis previously developed by the authors. (auth.)

Gaseous diffusion system

International Nuclear Information System (INIS)

Garrett, G.A.; Shacter, J.

1978-01-01

A gaseous diffusion system is described comprising a plurality of diffusers connected in cascade to form a series of stages, each of the diffusers having a porous partition dividing it into a high pressure chamber and a low pressure chamber, and means for combining a portion of the enriched gas from a succeeding stage with a portion of the enriched gas from the low pressure chamber of each stage and feeding it into one extremity of the high pressure chamber thereof

On CLOUD nine

CERN Multimedia

2009-01-01

The team from the CLOUD experiment - the world’s first experiment using a high-energy particle accelerator to study the climate - were on cloud nine after the arrival of their new three-metre diameter cloud chamber. This marks the end of three years’ R&D and design, and the start of preparations for data taking later this year.

The influence of clouds and diffuse radiation on ecosystem-atmosphere CO2 and CO18O exhanges

Energy Technology Data Exchange (ETDEWEB)

Still, C.J.; Riley, W.J.; Biraud, S.C.; Noone, D.C.; Buenning, N.H.; Randerson, J.T.; Torn, M.S.; Welker, J.; White, J.W.C.; Vachon, R.; Farquhar, G.D.; Berry, J.A.

2009-05-01

This study evaluates the potential impact of clouds on ecosystem CO{sub 2} and CO{sub 2} isotope fluxes ('isofluxes') in two contrasting ecosystems (a broadleaf deciduous forest and a C{sub 4} grassland), in a region for which cloud cover, meteorological, and isotope data are available for driving the isotope-enabled land surface model, ISOLSM. Our model results indicate a large impact of clouds on ecosystem CO{sub 2} fluxes and isofluxes. Despite lower irradiance on partly cloudy and cloudy days, predicted forest canopy photosynthesis was substantially higher than on clear, sunny days, and the highest carbon uptake was achieved on the cloudiest day. This effect was driven by a large increase in light-limited shade leaf photosynthesis following an increase in the diffuse fraction of irradiance. Photosynthetic isofluxes, by contrast, were largest on partly cloudy days, as leaf water isotopic composition was only slightly depleted and photosynthesis was enhanced, as compared to adjacent clear sky days. On the cloudiest day, the forest exhibited intermediate isofluxes: although photosynthesis was highest on this day, leaf-to-atmosphere isofluxes were reduced from a feedback of transpiration on canopy relative humidity and leaf water. Photosynthesis and isofluxes were both reduced in the C{sub 4} grass canopy with increasing cloud cover and diffuse fraction as a result of near-constant light limitation of photosynthesis. These results suggest that some of the unexplained variation in global mean {delta}{sup 18}O of CO{sub 2} may be driven by large-scale changes in clouds and aerosols and their impacts on diffuse radiation, photosynthesis, and relative humidity.

Application of the monazite radiation source to the petri dish-type cloud chamber and the influence of several factors on occurrence of tracks

International Nuclear Information System (INIS)

Hayakawa, Issei; Sago, Yutaka; Mori, Chizuo

2012-01-01

Monazite radiation source (2.5 mmΦ) proved to be useful as a radiation source of cloud chamber without the dispersion of powder or its adhesion because of a sintered body. After the track appeared within one minute after having put the petri dish on the dry ice, the number increased rapidly followed by the tendency to decrease gradually after that. The tracks can be observed for about 20 minutes after cooled with dry ice. The size of dry ice should be chosen to enter the inside of the bottom edge of the petri dish. The same number of tracks as using conventional mantle radiation source was obtained by utilizing 3 pieces of monazite sintered body separated mutually by about 7.5 mm. Hence the petri dish-type cloud chamber with the monazite sintered body as radiation source revealed to make the observation of track easy and prompt. (author)

Atmospheric cloud physics laboratory project study

Science.gov (United States)

Schultz, W. E.; Stephen, L. A.; Usher, L. H.

1976-01-01

Engineering studies were performed for the Zero-G Cloud Physics Experiment liquid cooling and air pressure control systems. A total of four concepts for the liquid cooling system was evaluated, two of which were found to closely approach the systems requirements. Thermal insulation requirements, system hardware, and control sensor locations were established. The reservoir sizes and initial temperatures were defined as well as system power requirements. In the study of the pressure control system, fluid analyses by the Atmospheric Cloud Physics Laboratory were performed to determine flow characteristics of various orifice sizes, vacuum pump adequacy, and control systems performance. System parameters predicted in these analyses as a function of time include the following for various orifice sizes: (1) chamber and vacuum pump mass flow rates, (2) the number of valve openings or closures, (3) the maximum cloud chamber pressure deviation from the allowable, and (4) cloud chamber and accumulator pressure.

Structure and characteristics of diffuse interstellar clouds

International Nuclear Information System (INIS)

Arshutkin, L.N.; Kolesnik, I.G.

1978-01-01

The results of model calculations for spherically symmetrical interstellar clouds being under external pressure are given. Thermal balance of gas clouds is considered. Ultraviolet radiation fields in clouds and equilibrium for chemical elements are calculated for this purpose. Calculations were carried out in the case when cooling is under way mainly by carbon atoms and ions. The clouds with mass up to 700 Msub(sun) under external pressure from 800 to 3000 K cm -3 are considered. In typical for Galactic disk conditions, clouds have dense n > or approximately 200 cm -3 , and cold T approximately 20-30 K state clouds depending on external pressure is given. The critical mass for clouds at the Galactic disk is approximately 500-600 Msub(sun). It is less than the isothermal solution by a factor of approximately 1.5. The massive gas-dust cloud formation problem is discussed

Design of monolithic preamplifiers employing diffused n-JFETs for ionization chamber colorimeters

International Nuclear Information System (INIS)

Demicheli, M.; Manfredi, P.F.; Speziali, V.; Radeka, V.; Rescia, S.

1990-01-01

Silicon n-channel JFETs obtained by diffusing the gate into the epitaxial layer which contains the channel still feature unsurpassed noise performances in charge measurements with radiation detectors. Compared to implanted-gate junction field-effect devices, they have a better behaviour in the low-frequency noise, while the thermal noise in the channel more closely conforms to the expected g m -dependence. With respect to MOSFETs they feature, besides lower noise, superior radiation hardness and resistance to electrostatic discharges into the gate. The actual paper discusses the basic design considerations of a preamplifier for ionization chamber calorimeters, which is intended for monolithic integration based on a dielectrically isolated process. (orig.)

Enhanced nitrogen removal in single-chamber microbial fuel cells with increased gas diffusion areas

KAUST Repository

Yan, Hengjing

2012-11-23

Single-chamber microbial fuel cells (MFCs) with nitrifiers pre-enriched at the air cathodes have previously been demonstrated as a passive strategy for integrating nitrogen removal into current-generating bioelectrochemical systems. To further define system design parameters for this strategy, we investigated in this study the effects of oxygen diffusion area and COD/N ratio in continuous-flow reactors. Doubling the gas diffusion area by adding an additional air cathode or a diffusion cloth significantly increased the ammonia and COD removal rates (by up to 115% and 39%), ammonia removal efficiency (by up to 134%), the cell voltage and cathode potentials, and the power densities (by a factor of approximately 2). When the COD/N ratio was lowered from 13 to 3, we found up to 244% higher ammonia removal rate but at least 19% lower ammonia removal efficiency. An increase of COD removal rate by up to 27% was also found when the COD/N ratio was lowered from 11 to 3. The Coulombic efficiency was not affected by the additional air cathode, but decreased by an average of 11% with the addition of a diffusion cloth. Ammonia removal by assimilation was also estimated to understand the ammonia removal mechanism in these systems. These results showed that the doubling of gas diffusion area enhanced N and COD removal rates without compromising electrochemical performance. © 2012 Wiley Periodicals, Inc.

Effects of stratocumulus, cumulus, and cirrus clouds on the UV-B diffuse to global ratio: Experimental and modeling results

International Nuclear Information System (INIS)

López, María Laura; Palancar, Gustavo G.; Toselli, Beatriz M.

2012-01-01

Broadband measurements of global and diffuse UV-B irradiance (280-315 nm) together with modeled and measured diffuse to global ratios (DGR) have been used to characterize the influence of different types of clouds on irradiance at the surface. Measurements were carried out during 2000-2001 in Córdoba City, Argentina. The Tropospheric Ultraviolet Visible (TUV) model was used to analyze the behavior of the modeled DGRs for different cloud optical depths and at different altitudes and solar zenith angles (SZA). Different cloud altitudes were also tested, although only the results for a cloud placed at 1.5-2.5 km of altitude are shown. A total of 16 day with stratocumulus, 12 with cumulus, and 16 with cirrus have been studied and compared among them and also against 21 clear sky days. Different behaviors were clearly detected and also differentiated through the analysis of the averages and the standard deviations of the DGRs: 1.02±0.06 for stratocumulus, 0.74±0.18 for cumulus, 0.63±0.12 for cirrus, and 0.60±0.13 for the clear sky days, respectively. Stratocumulus clouds showed a low variability in the DGR values, which were concentrated close to one at all SZAs. DGR values for cumulus clouds presented a large variability at all SZAs, mostly associated with the different optical depths. Finally, the closeness between the DGR values for cirrus clouds and the DGR values for clear days showed that these clouds generally do not strongly affect the UV-B irradiance at the surface at any SZA. In the opposite side, stratocumulus clouds were identified as those with the largest effects, at all SZAs, on the UV-B irradiance at the surface.

MAGNETIC FIELD STRUCTURE OF THE LARGE MAGELLANIC CLOUD FROM FARADAY ROTATION MEASURES OF DIFFUSE POLARIZED EMISSION

Energy Technology Data Exchange (ETDEWEB)

Mao, S. A. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); McClure-Griffiths, N. M.; McConnell, D. [Australia Telescope National Facility, CSIRO Astronomy and Space Science, Epping, NSW 1710 (Australia); Gaensler, B. M. [Sydney Institute for Astronomy, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia); Haverkorn, M. [Department of Astrophysics, Radboud University, P.O. Box 9010, 6500-GL Nijmegen (Netherlands); Beck, R. [Max-Planck-Institut fuer Radioastronomie, D-53121 Bonn (Germany); Wolleben, M. [Square Kilometre Array South Africa, The Park, Pinelands 7405 (South Africa); Stanimirovic, S. [Department of Astronomy, University of Wisconsin, Madison, WI 53706 (United States); Dickey, J. M. [Physics Department, University of Tasmania, Hobart, TAS 7001 (Australia); Staveley-Smith, L., E-mail: mao@astro.wisc.edu [International Centre for Radio Astronomy Research (ICRAR), The University of Western Australia, Crawley, WA 6009 (Australia)

2012-11-01

We present a study of the magnetic field of the Large Magellanic Cloud (LMC), carried out using diffuse polarized synchrotron emission data at 1.4 GHz acquired at the Parkes Radio Telescope and the Australia Telescope Compact Array. The observed diffuse polarized emission is likely to originate above the LMC disk on the near side of the galaxy. Consistent negative rotation measures (RMs) derived from the diffuse emission indicate that the line-of-sight magnetic field in the LMC's near-side halo is directed coherently away from us. In combination with RMs of extragalactic sources that lie behind the galaxy, we show that the LMC's large-scale magnetic field is likely to be of quadrupolar geometry, consistent with the prediction of dynamo theory. On smaller scales, we identify two brightly polarized filaments southeast of the LMC, associated with neutral hydrogen arms. The filaments' magnetic field potentially aligns with the direction toward the Small Magellanic Cloud (SMC). We suggest that tidal interactions between the SMC and the LMC in the past 10{sup 9} years are likely to have shaped the magnetic field in these filaments.

Exact and near backscattering measurements of the linear depolarisation ratio of various ice crystal habits generated in a laboratory cloud chamber

International Nuclear Information System (INIS)

Smith, Helen R.; Connolly, Paul J.; Webb, Ann R.; Baran, Anthony J.

2016-01-01

Ice clouds were generated in the Manchester Ice Cloud Chamber (MICC), and the backscattering linear depolarisation ratio, δ, was measured for a variety of habits. To create an assortment of particle morphologies, the humidity in the chamber was varied throughout each experiment, resulting in a range of habits from the pristine to the complex. This technique was repeated at three temperatures: −7 °C, −15 °C and −30 °C, in order to produce both solid and hollow columns, plates, sectored plates and dendrites. A linearly polarised 532 nm continuous wave diode laser was directed through a section of the cloud using a non-polarising 50:50 beam splitter. Measurements of the scattered light were taken at 178°, 179° and 180°, using a Glan–Taylor prism to separate the co- and cross-polarised components. The intensities of these components were measured using two amplified photodetectors and the ratio of the cross- to co-polarised intensities was measured to find the linear depolarisation ratio. In general, it was found that Ray Tracing over-predicts the linear depolarisation ratio. However, by creating more accurate particle models which better represent the internal structure of ice particles, discrepancies between measured and modelled results (based on Ray Tracing) were reduced. - Highlights: • Linear depolarisation ratio was measured for various crystal habits. • Measurements were taken at 178°, 179° and 180°. • Various crystal properties were modelled and tested in ray tracing. • Measured and modelled results are discussed. • Modelled results are generally found to overpredict LDR.

The CO Transition from Diffuse Molecular Gas to Dense Clouds

Science.gov (United States)

Rice, Johnathan S.; Federman, Steven

2017-06-01

The atomic to molecular transitions occurring in diffuse interstellar gas surrounding molecular clouds are affected by the local physical conditions (density and temperature) and the radiation field penetrating the material. Our optical observations of CH, CH^{+}, and CN absorption from McDonald Observatory and the European Southern Observatory are useful tracers of this gas and provide the velocity structure needed for analyzing lower resolution ultraviolet observations of CO and H_{2} absorption from Far Ultraviolet Spectroscopic Explorer. We explore the changing environment between diffuse and dense gas by using the column densities and excitation temperatures from CO and H_{2} to determine the gas density. The resulting gas densities from this method are compared to densities inferred from other methods such as C_{2} and CN chemistry. The densities allow us to interpret the trends from the combined set of tracers. Groupings of sight lines, such as those toward h and χ Persei or Chameleon provide a chance for further characterization of the environment. The Chameleon region in particular helps illuminate CO-dark gas, which is not associated with emission from H I at 21 cm or from CO at 2.6 mm. Expanding this analysis to include emission data from the GOT C+ survey allows the further characterization of neutral diffuse gas, including CO-dark gas.

Molecular clouds without detectable CO

International Nuclear Information System (INIS)

Blitz, L.; Bazell, D.; Desert, F.X.

1990-01-01

The clouds identified by Desert, Bazell, and Boulanger (DBB clouds) in their search for high-latitude molecular clouds were observed in the CO (J = 1-0) line, but only 13 percent of the sample was detected. The remaining 87 percent are diffuse molecular clouds with CO abundances of about 10 to the -6th, a typical value for diffuse clouds. This hypothesis is shown to be consistent with Copernicus data. The DBB clouds are shown to be an essentially complete catalog of diffuse molecular clouds in the solar vicinity. The total molecular surface density in the vicinity of the sun is then only about 20 percent greater than the 1.3 solar masses/sq pc determined by Dame et al. (1987). Analysis of the CO detections indicates that there is a sharp threshold in extinction of 0.25 mag before CO is detectable and is derived from the IRAS I(100) micron threshold of 4 MJy/sr. This threshold is presumably where the CO abundance exhibits a sharp increase 18 refs

The mass spectrum of interstellar clouds

International Nuclear Information System (INIS)

Dickey, J.M.; Garwood, R.W.

1989-01-01

The abundances of diffuse clouds and molecular clouds in the inner Galaxy and at the solar circle are compared. Using results of recent low-latitude 21 cm absorption studies, the number of diffuse clouds per kiloparsec along the line of sight is derived as a function of the cloud column density, under two assumptions relating cloud densities and temperatures. The density of clouds is derived as a function of cloud mass. The results are consistent with a single, continuous mass spectrum for interstellar clouds from less than 1 solar mass to 1,000,000 solar masses, with perhaps a change of slope at masses where the atomic and molecular mass fractions are roughly equal. 36 refs

Diffusion chamber system for testing of collagen-based cell migration barriers for separation of ligament enthesis zones in tissue-engineered ACL constructs.

Science.gov (United States)

Hahner, J; Hoyer, M; Hillig, S; Schulze-Tanzil, G; Meyer, M; Schröpfer, M; Lohan, A; Garbe, L-A; Heinrich, G; Breier, A

2015-01-01

A temporary barrier separating scaffold zones seeded with different cell types prevents faster growing cells from overgrowing co-cultured cells within the same construct. This barrier should allow sufficient nutrient diffusion through the scaffold. The aim of this study was to test the effect of two variants of collagen-based barriers on macromolecule diffusion, viability, and the spreading efficiency of primary ligament cells on embroidered scaffolds. Two collagen barriers, a thread consisting of a twisted film tape and a sponge, were integrated into embroidered poly(lactic-co-caprolactone) and polypropylene scaffolds, which had the dimension of lapine anterior cruciate ligaments (ACL). A diffusion chamber system was designed and established to monitor nutrient diffusion using fluorescein isothiocyanate-labeled dextran of different molecular weights (20, 40, 150, 500 kDa). Vitality of primary lapine ACL cells was tested at days 7 and 14 after seeding using fluorescein diacetate and ethidium bromide staining. Cell spreading on the scaffold surface was measured using histomorphometry. Nuclei staining of the cross-sectioned scaffolds revealed the penetration of ligament cells through both barrier types. The diffusion chamber was suitable to characterize the diffusivity of dextran molecules through embroidered scaffolds with or without integrated collagen barriers. The diffusion coefficients were generally significantly lower in scaffolds with barriers compared to those without barriers. No significant differences between diffusion coefficients of both barrier types were detected. Both barriers were cyto-compatible and prevented most of the ACL cells from crossing the barrier, whereby the collagen thread was easier to handle and allowed a higher rate of cell spreading.

Diffuse sound field: challenges and misconceptions

DEFF Research Database (Denmark)

Jeong, Cheol-Ho

2016-01-01

Diffuse sound field is a popular, yet widely misused concept. Although its definition is relatively well established, acousticians use this term for different meanings. The diffuse sound field is defined by a uniform sound pressure distribution (spatial diffusion or homogeneity) and uniform...... tremendously in different chambers because the chambers are non-diffuse in variously different ways. Therefore, good objective measures that can quantify the degree of diffusion and potentially indicate how to fix such problems in reverberation chambers are needed. Acousticians often blend the concept...... of mixing and diffuse sound field. Acousticians often refer diffuse reflections from surfaces to diffuseness in rooms, and vice versa. Subjective aspects of diffuseness have not been much investigated. Finally, ways to realize a diffuse sound field in a finite space are discussed....

Simulation of the electron cloud density in BEPC II

International Nuclear Information System (INIS)

Liu Yudong; Guo Zhiyuan; Wang Jiuqing

2004-01-01

Electron Cloud Instability (ECI) may take place in positron storage ring when the machine is operated with multi-bunch positron beam. According to the actual shape of the vacuum chamber in the BEPC II, a program has been developed. With the code, authors can calculate the electron density in the chamber with different length of antechamber and the different secondary electron yield respectively. By the simulation, the possibility to put clearing electrodes in the chamber to reduce the electron density in the central region of the chamber is investigated. The simulation provides meaningful and important results for the BEPC II project and electron cloud instability research

Re-evaluation of the Pressure Effect for Nucleation in Laminar Flow Diffusion Chamber Experiments with Fluent and the Fine Particle Model

Czech Academy of Sciences Publication Activity Database

Herrmann, E.; Hyvärinen, A.-P.; Brus, David; Lihavainen, H.; Kulmala, M.

2009-01-01

Roč. 113, č. 8 (2009), s. 1434-1439 ISSN 1089-5639 Institutional research plan: CEZ:AV0Z40720504 Keywords : laminar flow diffusion chamber * experimental data * fine particle model Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.899, year: 2009

Proposal to negotiate a collaboration agreement for the design and prototyping of a machine for laser treatment of metallic vacuum chamber walls for electron cloud mitigation at the High Luminosity LHC

CERN Document Server

2016-01-01

Proposal to negotiate a collaboration agreement for the design and prototyping of a machine for laser treatment of metallic vacuum chamber walls for electron cloud mitigation at the High Luminosity LHC

LS1 Report: the clouds are lifting

CERN Multimedia

Anaïs Schaeffer

2014-01-01

To combat the problem of electron clouds, which perturbate the environment of the particle beams in our accelerators, the Vacuum team have turned to amorphous carbon. This material is being applied to the interior of 16 magnets in the SPS during LS1 and will help prevent the formation of the secondary particles which are responsible for these clouds.   This photo shows the familiar coils of an SPS dipole magnet in brown. The vacuum chamber is the metallic rectangular part in the centre. The small wheeled device you can see in the vacuum chamber carries the hollow cathodes  along the length of the chamber. When a particle beam circulates at high energy in a vacuum chamber, it unavoidably generates secondary particles. These include electrons produced by the ionisation of residual molecules in the vacuum or indirectly generated by synchrotron radiation. When these electrons hit the surface of the vacuum chamber, they produce other electrons which, through an avalanche-like process, re...

LHC Report: Out of the clouds

CERN Multimedia

Giovanni Rumolo, Giovanni Iadarola and Hannes Bartosik for the LHC team

2015-01-01

In order for the LHC to deliver intense proton beams to the experiments, operators have to perform “scrubbing” of the beam pipes. This operation is necessary to reduce the formation of electron clouds, which would generate instabilities in the colliding beams.   Electron clouds are generated in accelerators running with positively charged particles when electrons - produced by the ionisation of residual molecules in the vacuum or by the photoelectric effect from synchrotron radiation - are accelerated by the beam field and hit the surface of the vacuum chamber producing other electrons. This avalanche-like process can result in the formation of clouds of electrons. Electron clouds are detrimental to the beam for a few reasons. First, the electrons impacting the walls desorb molecules and degrade the ultra-high vacuum in the beam chamber. Furthermore, they interact electromagnetically with the beam, leading to the oscillation and expansion of the particle bunches. This increases...

Uncertainty in counting ice nucleating particles with continuous flow diffusion chambers

Science.gov (United States)

Garimella, Sarvesh; Rothenberg, Daniel A.; Wolf, Martin J.; David, Robert O.; Kanji, Zamin A.; Wang, Chien; Rösch, Michael; Cziczo, Daniel J.

2017-09-01

This study investigates the measurement of ice nucleating particle (INP) concentrations and sizing of crystals using continuous flow diffusion chambers (CFDCs). CFDCs have been deployed for decades to measure the formation of INPs under controlled humidity and temperature conditions in laboratory studies and by ambient aerosol populations. These measurements have, in turn, been used to construct parameterizations for use in models by relating the formation of ice crystals to state variables such as temperature and humidity as well as aerosol particle properties such as composition and number. We show here that assumptions of ideal instrument behavior are not supported by measurements made with a commercially available CFDC, the SPectrometer for Ice Nucleation (SPIN), and the instrument on which it is based, the Zurich Ice Nucleation Chamber (ZINC). Non-ideal instrument behavior, which is likely inherent to varying degrees in all CFDCs, is caused by exposure of particles to different humidities and/or temperatures than predicated from instrument theory of operation. This can result in a systematic, and variable, underestimation of reported INP concentrations. We find here variable correction factors from 1.5 to 9.5, consistent with previous literature values. We use a machine learning approach to show that non-ideality is most likely due to small-scale flow features where the aerosols are combined with sheath flows. Machine learning is also used to minimize the uncertainty in measured INP concentrations. We suggest that detailed measurement, on an instrument-by-instrument basis, be performed to characterize this uncertainty.

Uncertainty in counting ice nucleating particles with continuous flow diffusion chambers

Directory of Open Access Journals (Sweden)

S. Garimella

2017-09-01

Full Text Available This study investigates the measurement of ice nucleating particle (INP concentrations and sizing of crystals using continuous flow diffusion chambers (CFDCs. CFDCs have been deployed for decades to measure the formation of INPs under controlled humidity and temperature conditions in laboratory studies and by ambient aerosol populations. These measurements have, in turn, been used to construct parameterizations for use in models by relating the formation of ice crystals to state variables such as temperature and humidity as well as aerosol particle properties such as composition and number. We show here that assumptions of ideal instrument behavior are not supported by measurements made with a commercially available CFDC, the SPectrometer for Ice Nucleation (SPIN, and the instrument on which it is based, the Zurich Ice Nucleation Chamber (ZINC. Non-ideal instrument behavior, which is likely inherent to varying degrees in all CFDCs, is caused by exposure of particles to different humidities and/or temperatures than predicated from instrument theory of operation. This can result in a systematic, and variable, underestimation of reported INP concentrations. We find here variable correction factors from 1.5 to 9.5, consistent with previous literature values. We use a machine learning approach to show that non-ideality is most likely due to small-scale flow features where the aerosols are combined with sheath flows. Machine learning is also used to minimize the uncertainty in measured INP concentrations. We suggest that detailed measurement, on an instrument-by-instrument basis, be performed to characterize this uncertainty.

C+/CO Transitions in the Diffuse ISM: Transitional Cloud Sample from the GOT C+ Survey of [CII] in the inner Galaxy at l = -30deg to 30deg

Science.gov (United States)

Velusamy, T.; Pineda, J. L.; Langer, W. D.; Willacy, K.; Goldsmith, P. F.

2011-05-01

Our knowledge of interstellar gas has been limited primarily to the diffuse atomic phase traced by HI and the well-shielded molecular phase traced by CO. Recently, using the first results of the Herschel Key Project GOT C+, a HIFI C+ survey of the Galactic plane, Velusamy, Langer, Pineda et al. (A&A 521, L18, 2010) have shown that in the diffuse interstellar transition clouds a significant fraction of the carbon exists primarily as C^+ with little C^0 and CO in a warm 'dark gas' layer in which hydrogen is mostly H_2 with little atomic H, surrounding a modest 12CO-emitting core. The [CII] fine structure transition, at 1.9 THz (158 μm) is the best tracer of this component of the interstellar medium, which is critical to our understanding of the atomic to molecular cloud transitions. The Herschel Key Project GOT C+ is designed to study such clouds by observing with HIFI the [CII] line emission along 500 lines of sight (LOSs) throughout the Galactic disk. Here we present the identification and chemical status of a few hundred diffuse and transition clouds traced by [CII], along with auxiliary HI and CO data covering ~100 LOSs in the inner Galaxy between l= -30° and 30°. We identify transition clouds as [CII] components that are characterized by the presence of both HI and 12CO, but no 13CO emission. The intensities, I(CII) and I(HI), are used as measures of the visual extinction, AV, in the cloud up to the C^+/C^0/CO transition layer and a comparison with I(12CO) yields a more complete H_2 molecular inventory. Our results show that [CII] emission is an excellent tool to study transition clouds and their carbon chemistry in the ISM, in particular as a unique tracer of molecular H_2, which is not easily observed by other means. The large sample presented here will serve as a resource to study the chemical and physical status of diffuse transition clouds in a wide range of Galactic environments and constrain the physical parameters such as the FUV intensity and cosmic

Wave Augmented Diffuser for Centrifugal Compressor

Science.gov (United States)

Skoch, Gary J. (Inventor); Paxson, Daniel E. (Inventor)

2001-01-01

A wave augmented diffuser for a centrifugal compressor surrounds the outlet of an impeller that rotates on a drive shaft having an axis of rotation. The impeller brings flow in in an axial direction and imparts kinetic energy to the flow discharging it in radial and tangential directions. The flow is discharged into a plurality of circumferentially disposed wave chambers. The wave chambers are periodically opened and closed by a rotary valve such that the flow through the diffuser is unsteady. The valve includes a plurality of valve openings that are periodically brought into and out of fluid communication with the wave chambers. When the wave chambers are closed, a reflected compression wave moves upstream towards the diffuser bringing the flow into the wave chamber to rest. This action recovers the kinetic energy from the flow and limits any boundary layer growth. The flow is then discharged in an axial direction through an opening in the valve plate when the valve plate is rotated to an open position. The diffuser thus efficiently raises the static pressure of the fluid and discharges an axially directed flow at a radius that is predominantly below the maximum radius of the diffuser.

Role of visualization of nuclear radiation in public education on atomic energy. Visualization of natural nuclear radiation using a cloud chamber

International Nuclear Information System (INIS)

Kaneko, Junichi H.; Fujita, Fumiyuki; Narabayashi, Tadashi

2008-01-01

Nuclear radiation is indispensable tool, i.e., medical diagnostic systems and industrial nondestructive measurement systems, for our life. On the other hand, ordinary people sometimes have bad image for nuclear radiation. To improve this undesirable situation, many individuals and groups keep holding public educational meeting on nuclear radiation. For this purpose, visualization of natural nuclear radiation by a cloud chamber is very effective way; participants feel existence of nuclear radiation directly. In this talk, public educational activity of Hokkaido University and Japan Atomic Energy Society Hokkaido branch will be reported. (author)

Effects of different diffuser types on the diffusivity in reverberation chambers

DEFF Research Database (Denmark)

Nolan, Melanie; Vercammen, Martijn; Jeong, Cheol-Ho

2015-01-01

Knowledge of sound absorption properties of typical building materials is essential for all tasks related to room acoustic design. The Sabine absorption coefficient is measured in a reverberation chamber according to the international standard ISO 354. It is known that inter-laboratory reproducib...

Electron Cloud Buildup Characterization Using Shielded Pickup Measurements and Custom Modeling Code at CESRTA

CERN Document Server

Crittenden, James A

2013-01-01

The Cornell Electron Storage Ring Test Accelerator experimental program includes investigations into electron cloud buildup, applying various mitigation techniques in custom vacuum chambers. Among these are two 1.1-m-long sections located symmetrically in the east and west arc regions. These chambers are equipped with pickup detectors shielded against the direct beam-induced signal. They detect cloud electrons migrating through an 18-mm-diameter pattern of small holes in the top of the chamber. A digitizing oscilloscope is used to record the signals, providing time-resolved information on cloud development. Carbon-coated, TiN-coated and uncoated aluminum chambers have been tested. Electron and positron beams of 2.1, 4.0 and 5.3 GeV with a variety of bunch populations and spacings in steps of 4 and 14 ns have been used. Here we report on results from the ECLOUD modeling code which highlight the sensitivity of these measurements to the physical phenomena determining cloud buildup such as the photoelectron produ...

On-line determination of ammonia at low pptv mixing ratios in the CLOUD chamber

CERN Document Server

Bianchi, F; Mathot, S; Baltensperger, U

2012-01-01

A new instrument for the on-line determination of ammonia was developed. Since ammonia is a rather sticky compound, sampling losses were minimised with a new sam- pling device where the ammonia was transferred to the liq- uid phase only 5 mm after the inlet tip. The liquid phase was then analyzed by long pathlength absorption spectrophotom- etry using the Berthelot reaction with phenol and hypochlo- rite as reagents. The measurements were made during the CLOUD3 campaign at CERN where the influence of ammo- nia on the nucleation rate was studied. At stable conditions the detection limit reached with this instrument was 35 pptv (air flow rate of 2 l min − 1 , liquid flow rate of 0.3 ml min − 1 ), although occasionally the instrument was affected by back- ground problems. The range of mixing ratios during this campaign was varied from the background contamination ( < 35 pptv) up to around 2 ppbv. The measured ammonia concentration was correlated with the rate of ammonia in- jected into the chamber, but wi...

Precombination Cloud Collapse and Baryonic Dark Matter

Science.gov (United States)

Hogan, Craig J.

1993-01-01

A simple spherical model of dense baryon clouds in the hot big bang 'strongly nonlinear primordial isocurvature baryon fluctuations' is reviewed and used to describe the dependence of cloud behavior on the model parameters, baryon mass, and initial over-density. Gravitational collapse of clouds before and during recombination is considered including radiation diffusion and trapping, remnant type and mass, and effects on linear large-scale fluctuation modes. Sufficiently dense clouds collapse early into black holes with a minimum mass of approx. 1 solar mass, which behave dynamically like collisionless cold dark matter. Clouds below a critical over-density, however, delay collapse until recombination, remaining until then dynamically coupled to the radiation like ordinary diffuse baryons, and possibly producing remnants of other kinds and lower mass. The mean density in either type of baryonic remnant is unconstrained by observed element abundances. However, mixed or unmixed spatial variations in abundance may survive in the diffuse baryon and produce observable departures from standard predictions.

Effect of daily low dose gamma irradiation on growth and differentiation of human myeloid leukaemic bone marrow in diffusion chambers

Energy Technology Data Exchange (ETDEWEB)

Greenberger, J S [Joint Center for Radiation Therapy, Department of Radiation and Sidney Farber Cancer Institute; Chang, J M; King, V; Fulmer, S; Balzuno, S; Moloney, W C [Division of Hematology, Department of Medicine, Brigham and Women' s Hospital Harvard Medical School, Boston, USA

1981-01-01

Bone marrow from each of 8 untreated patients with myeloproliferative disorders was grown in diffusion chambers in 760 rad total body irradiated rats. Rats were exposed to 11.5, 57.5, or 108.5 rad daily for 14-21 and cell growth compared to that detected in unirradiated chambers. Cells from acute myelogenous leukaemia patients exposed to 11.5 rad per d grew for 11-21 d and there was no consistent stimulation of differentiation of immature granulocytic cells to mature granulocytes that was attributable to irradiation. Cells from a chronic myeloid leukaemia patient in chronic phase or blast crisis, and a polycythaemia vera patient with myeloid metaplasia showed signigicant morphologic differentiation from immature to mature granulocytes in control chambers with no additional effect of daily irradiation. Marrow specimens from 2 AML patients exposed to each of 3 daily dose fractions over 14 d revealed a dose-dependent decrease in immature granulocytes with no persistent increase in mature granulocytes. In both irradiated and control chambers, macrophages increased over 21 d. Thus, cells from patients with myeloprofilerative disorders may not necessarily differentiate to mature granulocytes following in vivo exposure to ionizing irradiation.

H2 Equilibrium Pressure with a Neg-Coated Vacuum Chamber as a Function of Temperature and H2 Concentration

CERN Document Server

Rossi, Adriana

2006-01-01

Non Evaporable Getter (NEG) coating is used in the Large Hadron Collider (LHC) room-temperature sections to ensure a low residual gas pressure for its properties of distributed pumping, low outgassing and desorption under particle bombardment; and to limit or cure electron cloud build-up due to its low secondary electron emission. In certain regions of the LHC, and in particular close to the beam collimators, the temperature of the vacuum chamber is expected to rise due to energy deposition from particle losses. Hydrogen molecules are pumped by the NEG via dissociation on the surface, sorption at the superficial sites and diffusion into the NEG bulk. In the case of hydrogen, the sorption is thermally reversible, causing the dissociation pressure to increase with NEG temperature and amount of H2 pumped. Measurements were carried out on a stainless steel chamber coated with TiZrV NEG as a function of the H2 concentration and the chamber temperature, to estimate the residual gas pressure in the collimator region...

Dynamic consideration of smog chamber experiments

Science.gov (United States)

Chuang, Wayne K.; Donahue, Neil M.

2017-08-01

Recent studies of the α-pinene + ozone reaction that address particle nucleation show relatively high molar yields of highly oxidized multifunctional organic molecules with very low saturation concentrations that can form and grow new particles on their own. However, numerous smog-chamber experiments addressing secondary organic aerosol (SOA) mass yields, interpreted via equilibrium partitioning theory, suggest that the vast majority of SOA from α-pinene is semivolatile. We explore this paradox by employing a dynamic volatility basis set (VBS) model that reproduces the new-particle growth rates observed in the CLOUD experiment at CERN and then modeling SOA mass yield experiments conducted at Carnegie Mellon University (CMU). We find that the base-case simulations do overpredict observed SOA mass but by much less than an equilibrium analysis would suggest; this is because delayed condensation of vapors suppresses the apparent mass yields early in the chamber experiments. We further find that a second VBS model featuring substantial oligomerization of semivolatile monomers can match the CLOUD growth rates with substantially lower SOA mass yields; this is because the lighter monomers have a higher velocity and thus a higher condensation rate for a given mass concentration. The oligomerization simulations are a closer match to the CMU experiments than the base-case simulations, though they overpredict the observations somewhat. However, we also find that if the chemical conditions in CLOUD and the CMU chamber were identical, substantial nucleation would have occurred in the CMU experiments when in fact none occurred. This suggests that the chemical mechanisms differed in the two experiments, perhaps because the high oxidation rates in the SOA formation experiments led to rapid termination of peroxy radical chemistry.

LHC Report: out of the clouds (part II)

CERN Multimedia

Giovanni Rumolo for the LHC team

2015-01-01

A large fraction of the LHC beam-time over the last two weeks has been devoted to the second phase of the scrubbing of the vacuum chambers. This was aimed at reducing the formation of electron clouds in the beam pipes, this time performed with 25-nanosecond spaced bunches. This operation is designed to prepare the machine for a smooth intensity ramp-up for physics with this type of beam.   The scrubbing of the accelerator beam pipes is done by running the machine under an intense electron cloud regime while respecting beam stability constraints. When electron cloud production becomes sufficiently intense, the probability of creating secondary electrons at the chamber walls decreases and this inhibits the whole process. In this way, the scrubbing operation eventually reduces the formation of electron clouds, which would otherwise generate instabilities in the colliding beams. The second phase of LHC scrubbing started on Saturday, 25 July, when 25 ns beams were circulated again in the LHC...

A Study of the Link between Cosmic Rays and Clouds with a Cloud Chamber at the CERN PS

CERN Multimedia

Laakso, L K; Lehtipalo, K; Miettinen, P K; Duarte branco da silva santos, F; Stojkov, Y; Jud, W; Wurm, F; Pinterich, T; Dommen, J; Curtius, J; Kreissl, F C; Minginette, P; Azeredo lima, J M; Kulmala, M T; Petaja, T T; Volkamer, R M; Schafer, M; Rodrigues tome, A; Viisanen, Y A; Onnela, A T O; Kristic, R; Ehrhart, S K; Amorim, A J; Maksumov, O; Kupc, A; Sitals, R P; Dunne, E M; Riipinen, I A; Downard, A J; Virtanen, A; Tsagkogeorgas, G; Schuchmann, S; Kvashnin, A; Hansel, A; Gonzalez carracedo, L R; Vrtala, A; Schallhart, S; Yan, C; Stratmann, F; Pinto mogo, S I; Makhmutov, V; Riccobono, F; Weingartner, E P; Kurten, C A; Rondo, L; Ruuskanen, T M; Finkenzeller, H F; Laaksonen, A J; De menezes, L; Hauser, D; Kajos, M K; Schmitt, T M; Mathot, S; Wasem, A; Guida, R; Metzger, A E; Baltensperger, U; Kirkby, J; Duplissy, J; Franchin, A; Rorup, B; Flagan, R C; Wex, H D

2002-01-01

Three recent independent observations suggest that galactic cosmic rays may exert a significant influence on the climate. Firstly, satellite data suggest a positive correlation between variations of cosmic ray intensity and the fraction of Earth covered by low clouds. Secondly, palaeoclimatic data provide extensive evidence for an association between cosmic ray intensity and climate over the last 10 kyr and at earlier times. Finally, the presence of ion-induced nucleation of new aerosol in the atmosphere is supported by recent observations. If cosmic rays do indeed enhance aerosol production and low cloud formation, this could exert a strong cooling influence on the radiative energy balance of Earth. Physical mechanisms by which cosmic rays may affect aerosol and clouds have been proposed and modelled, but definitive experiments are lacking. The aim of CLOUD is to investigate the nature and significance of cosmic ray-aerosol-cloud mechanisms under controlled laboratory conditions using the T11 beam at the CER...

Dynamic consideration of smog chamber experiments

Directory of Open Access Journals (Sweden)

W. K. Chuang

2017-08-01

Full Text Available Recent studies of the α-pinene + ozone reaction that address particle nucleation show relatively high molar yields of highly oxidized multifunctional organic molecules with very low saturation concentrations that can form and grow new particles on their own. However, numerous smog-chamber experiments addressing secondary organic aerosol (SOA mass yields, interpreted via equilibrium partitioning theory, suggest that the vast majority of SOA from α-pinene is semivolatile. We explore this paradox by employing a dynamic volatility basis set (VBS model that reproduces the new-particle growth rates observed in the CLOUD experiment at CERN and then modeling SOA mass yield experiments conducted at Carnegie Mellon University (CMU. We find that the base-case simulations do overpredict observed SOA mass but by much less than an equilibrium analysis would suggest; this is because delayed condensation of vapors suppresses the apparent mass yields early in the chamber experiments. We further find that a second VBS model featuring substantial oligomerization of semivolatile monomers can match the CLOUD growth rates with substantially lower SOA mass yields; this is because the lighter monomers have a higher velocity and thus a higher condensation rate for a given mass concentration. The oligomerization simulations are a closer match to the CMU experiments than the base-case simulations, though they overpredict the observations somewhat. However, we also find that if the chemical conditions in CLOUD and the CMU chamber were identical, substantial nucleation would have occurred in the CMU experiments when in fact none occurred. This suggests that the chemical mechanisms differed in the two experiments, perhaps because the high oxidation rates in the SOA formation experiments led to rapid termination of peroxy radical chemistry.

Measurements of the electron cloud in the APS storage ring

International Nuclear Information System (INIS)

Harkey, K. C.

1999-01-01

Synchrotron radiation interacting with the vacuum chamber walls in a storage ring produce photoelectrons that can be accelerated by the beam, acquiring sufficient energy to produce secondary electrons in collisions with the walls. If the secondary-electron yield (SEY) coefficient of the wall material is greater than one, as is the case with the aluminum chambers in the Advanced Photon Source (APS) storage ring, a runaway condition can develop. As the electron cloud builds up along a train of stored positron or electron bunches, the possibility exists that a transverse perturbation of the head bunch will be communicated to trailing bunches due to interaction with the cloud. In order to characterize the electron cloud, a special vacuum chamber was built and inserted into the ring. The chamber contains 10 rudimentary electron-energy analyzers, as well as three targets coated with different materials. Measurements show that the intensity and electron energy distribution are highly dependent on the temporal spacing between adjacent bunches and the amount of current contained in each bunch. Furthermore, measurements using the different targets are consistent with what would be expected based on the SEY of the coatings. Data for both positron and electron beams are presented

HYDROGEN CHLORIDE IN DIFFUSE INTERSTELLAR CLOUDS ALONG THE LINE OF SIGHT TO W31C (G10.6-0.4)

Energy Technology Data Exchange (ETDEWEB)

Monje, R. R.; Lis, D. C.; Phillips, T. G. [California Institute of Technology, MC 301-17, 1200 E. California Blvd., Pasadena, CA 91125-4700 (United States); Roueff, E. [Observatoire de Paris-Meudon, LUTH UMR 8102, 5 Pl. Jules Janssen, F-92195 Meudon Cedex (France); Gerin, M.; De Luca, M. [LERMA, CNRS, Observatoire de Paris and ENS, F-75231 Paris Cedex (France); Neufeld, D. A. [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Godard, B., E-mail: raquel@caltech.edu [Departamento de Astrofisica, Centro de Astrobiologia (CAB), INTA-CSIC, Crta. Torrejon km 4, E-28850 Torrejon de Ardoz, Madrid (Spain)

2013-04-10

We report the detection of hydrogen chloride, HCl, in diffuse molecular clouds on the line of sight toward the star-forming region W31C (G10.6-0.4). The J = 1-0 lines of the two stable HCl isotopologues, H{sup 35}Cl and H{sup 37}Cl, are observed using the 1b receiver of the Heterodyne Instrument for the Far-Infrared (HIFI) on board the Herschel Space Observatory. The HCl line is detected in absorption, over a wide range of velocities associated with diffuse clouds along the line of sight to W31C. The analysis of the absorption strength yields a total HCl column density of a few 10{sup 13} cm{sup -2}, implying that HCl accounts for {approx}0.6% of the total gas-phase chlorine, which exceeds the theoretical model predictions by a factor of {approx}6. This result is comparable to those obtained from the chemically related species H{sub 2}Cl{sup +} and HCl{sup +}, for which large column densities have also been reported on the same line of sight. The source of discrepancy between models and observations is still unknown; however, the detection of these Cl-bearing molecules provides key constraints for the chlorine chemistry in the diffuse gas.

Drift chamber detectors

International Nuclear Information System (INIS)

Duran, I.; Martinez Laso, L.

1989-01-01

A review of High Energy Physics detectors based on drift chambers is presented. The ionization, drift diffusion, multiplication and detection principles are described. Most common drift media are analysied, and a classification of the detectors according to its geometry is done. Finally the standard read-out methods are displayed and the limits of the spatial resolution are discussed. (Author)

Dimethylamine and ammonia measurements with ion chromatography during the CLOUD4 campaign

CERN Document Server

Praplan, A P; Dommen, J; Baltensperger, U

2012-01-01

The CLOUD project investigates the influence of galactic cosmic rays on the nucleation of new particles in an environmental chamber at CERN. Dimethylamine (DMA) was injected intentionally into the CLOUD chamber to reach atmospherically relevant levels away from sources (up to 100 pptv) in order to study its effect on nucleation with sulphuric acid and water at 278 K. Quantification of DMA and also background ammonia (NH 3 ) was performed with ion chromatography (IC). The IC method used together with the sampling line developed for CLOUD in order to measure NH 3 and DMA at low pptv levels is described; the overall sampling efficiency of the method is discussed; and, finally, mixing ratios of NH 3 and DMA measured during CLOUD4 are reported.

Electron Cloud Parameterization Studies in the LHC

CERN Document Server

Dominguez, O; Baglin, V; Bregliozzi, G; Jimenez, J M; Metral, E; Rumolo, G; Schulte, D; Zimmermann, F

2011-01-01

During LHC beam commissioning with 150, 75 and 50-ns bunch spacing, important electron-cloud effects, like pressure rise, cryogenic heat load, beam instabilities or emittance growth, were observed. The main strategy to combat the LHC electron cloud, defined about ten years ago, relies on the surface conditioning arising from the chamber-surface bombardment with cloud electrons. In a standard model, the conditioning state of the beam-pipe surface is characterized by three parameters: 1. most importantly, the secondary emission yield δmax; 2. the incident electron energy at which the yield is maximum, ε_max; and 3. the probability of elastic reflection of low-energy primary electrons hitting the chamber wall, R. Since at the LHC no in-situ secondary-yield measurements are available, we compare the relative local pressure-rise measurements taken for different beam configurations against simulations in which surface parameters are scanned. This benchmarking of measurements and simulations is used to infer the s...

Electron cloud buildup studies for the LHC

CERN Document Server

AUTHOR|(CDS)2160803; Boine-Frankenheim, Oliver

Electron clouds can develop in accelerators operating with positively charged particles. The con- sequences of e-cloud related effects are very important for the operation of the Large Hadron Collider (LHC) at CERN, and for the design of future accelerators including the LHC luminosity upgrade (HL-LHC). High electron densities are generated by an interaction between the beam and the confining chamber. Primary electrons, that can be generated through various mecha- nisms, are accelerated by the beam and impinge on the chamber walls, thereby extracting more electrons from the material. Furthermore they also deposit their kinetic energy in the process, which has to be compensated by the cooling system. Especially in cryogenic environments, as it is the case for a large part of the LHC, high heat loads can pose a serious problem. In order to improve the understanding of the electron cloud, simulation studies are performed with the code PyECLOUD, developed at CERN. The work of the first half of the project is desc...

Radon-222 measurements aboard an airplane for the description of atmospheric diffusion

International Nuclear Information System (INIS)

Bogen, J.

1973-01-01

Radon-222 is absorbed aboard an airplane in tubes filled with 50 g of selected charcoal and cooked in Dewars by carbon dioxide and freon. After air collection at different heights up to 5 km, the tubes are evacuated and heated in the laboratory for desorption of the gas molecules and for transfer into a decay chamber covered with zinc-sulfide serving as a scintillator for the detection of alpha activity from radon-222 and its daughters. In general, the measurements show an exponential decrease of the concentration up to 5 km in height, if there is no cloud layer. The height for a reduction by a factor of two is about 900 meters. Assuming a constant diffusion coefficient K 0 up to 5 km, the measurements yield a K 0 of approximately 3.7 x 10 4 cm 2 s -1 . For flights in stratiform clouds a decrease is observed of the concentration up to a certain height, then radon-222 is again increasing or remains constant. This must be explained with respect to the meteorological situation. Assuming only a constant value for K 0 between the different flying heights, it was possible to appraise the development of the eddy diffusion coefficient with height

Model calculations for the airborne Fast Ice Nuclei CHamber FINCH-HALO

Science.gov (United States)

Nillius, B.; Bingemer, H.; Bundke, U.; Jaenicke, R.; Reimann, B.; Wetter, T.

2009-04-01

Ice nuclei (IN) initiate the formation of primary ice in tropospheric clouds. In mixed phase clouds the primary ice crystals can grow very fast by the Bergeron-Findeisen process (Findeisen, 1938) at the expense of evaporating water droplets, and form precipitation. Thus, IN are essential for the development of precipitation in mixed phase clouds in the middle latitude. However, the role of IN in the development of clouds is still poorly understood and needs to be studied (Levin and Cotton, 2007). A Fast Ice Nuclei CHamber (FINCH-HALO) for airborne operation on the High And LOng Range research aircraft (HALO) is under development at the Institute for Atmosphere and Environment University Frankfurt. IN particles are activated within the chamber at certain ice super-saturation and temperature by mixing three gas flows, a warm moist, a cold dry, and an aerosol flow. After activation the particles will grow within a processing chamber. In an optical depolarisation detector droplets and ice crystals are detected separately. The setup of the new FINCH-HALO instrument is based on the ground based IN counter FINCH (Bundke, 2008). In FINCH-HALO a new cooling unit is used. Thus, measurements down to -40°C are possible. Furthermore minor changes of the inlet section where the mixing occurs were done. The contribution will present 3D model calculations with FLUENT of the flow conditions in the new inlet section for different pressure levels during a flight typical for HALO. Growth rates of ice crystals in the chamber at different temperature and super-saturation will be shown. References: Bundke U., B. Nillius, R. Jaenicke, T. Wetter, H. Klein, H. Bingemer, (2008). The Fast Ice Nucleus Chamber FINCH, Atmospheric Research, doi:10.1016/j.atmosres.2008.02.008 Findeisen, R., (1938). Meteorologisch-physikalische Begebenheiten der Vereisung in der Atmosphäre. Hauptversammlung 1938 der Lilienthal-Gesellschaft. Levin, Z., W. Cotton, (2007). Aerosol pollution impact on precipitation

Small-sized reverberation chamber for the measurement of sound absorption

International Nuclear Information System (INIS)

Rey, R. del; Alba, J.; Bertó, L.; Gregori, A.

2017-01-01

This paper presents the design, construction, calibration and automation of a reverberation chamber for small samples. A balance has been sought between reducing sample size, to reduce the manufacturing costs of materials, and finding the appropriate volume of the chamber, to obtain reliable values at high and mid frequencies. The small-sized reverberation chamber, that was built, has a volume of 1.12 m3 and allows for the testing of samples of 0.3 m2. By using diffusers, to improve the diffusion degree, and automating measurements, we were able to improve the reliability of the results, thus reducing test errors. Several comparison studies of the measurements of the small-sized reverberation chamber and the standardised reverberation chamber are shown, and a good degree of adjustment can be seen between them, within the range of valid frequencies. This paper presents a small laboratory for comparing samples and making decisions before the manufacturing of larger sizes. [es

The spectral energy distribution of the scattered light from dark clouds

Science.gov (United States)

Mattila, Kalevi; Schnur, G. F. O.

1989-01-01

A dark cloud is exposed to the ambient radiation field of integrated starlight in the Galaxy. Scattering of starlight by the dust particles gives rise to a diffuse surface brightness of the dark nebula. The intensity and the spectrum of this diffuse radiation can be used to investigate, e.g., the scattering parameters of the dust, the optical thickness of the cloud, and as a probe of the ambient radiation field at the location of the cloud. An understanding of the scattering process is also a prerequisite for the isolation of broad spectral features due to fluorescence or to any other non-scattering origin of the diffuse light. Model calculations are presented for multiple scattering in a spherical cloud. These calculations show that the different spectral shapes of the observed diffuse light can be reproduced with standard dust parameters. The possibility to use the observed spectrum as a diagnostic tool for analyzing the thickness of the cloud and the dust particle is discussed.

Using satellite-derived optical thickness to assess the influence of clouds on terrestrial carbon uptake

Science.gov (United States)

S.J. Cheng; A.L. Steiner; D.Y. Hollinger; G. Bohrer; K.J. Nadelhoffer

2016-01-01

Clouds scatter direct solar radiation, generating diffuse radiation and altering the ratio of direct to diffuse light. If diffuse light increases plant canopy CO2 uptake, clouds may indirectly influence climate by altering the terrestrial carbon cycle. However, past research primarily uses proxies or qualitative categories of clouds to connect...

Drift Chambers detectors

International Nuclear Information System (INIS)

Duran, I.; Martinez laso, L.

1989-01-01

We present here a review of High Energy Physics detectors based on drift chambers. The ionization, drift diffusion, multiplication and detection principles are described. Most common drift media are analysed, and a classification of the detectors according to its geometry is done. Finally the standard read-out methods are displayed and the limits of the spatial resolution are discussed. (Author) 115 refs

Electron Cloud Effect in the Linear Colliders

International Nuclear Information System (INIS)

Pivi, M

2004-01-01

Beam induced multipacting, driven by the electric field of successive positively charged bunches, may arise from a resonant motion of electrons, generated by secondary emission, bouncing back and forth between opposite walls of the vacuum chamber. The electron-cloud effect (ECE) has been observed or is expected at many storage rings [1]. In the beam pipe of the Damping Ring (DR) of a linear collider, an electron cloud is produced initially by ionization of the residual gas and photoelectrons from the synchrotron radiation. The cloud is then sustained by secondary electron emission. This electron cloud can reach equilibrium after the passage of only a few bunches. The electron-cloud effect may be responsible for collective effects as fast coupled-bunch and single-bunch instability, emittance blow-up or incoherent tune shift when the bunch current exceeds a certain threshold, accompanied by a large number of electrons in the vacuum chamber. The ECE was identified as one of the most important R and D topics in the International Linear Collider Report [2]. Systematic studies on the possible electron-cloud effect have been initiated at SLAC for the GLC/NLC and TESLA linear colliders, with particular attention to the effect in the positron main damping ring (MDR) and the positron Low Emittance Transport which includes the bunch compressor system (BCS), the main linac, and the beam delivery system (BDS). We present recent computer simulation results for the main features of the electron cloud generation in both machine designs. Thus, single and coupled-bunch instability thresholds are estimated for the GLC/NLC design

NEG coating of the non-standard LSS vacuum chambers

CERN Document Server

Costa-Pinto, P

2005-01-01

The vacuum chambers of nearly all the warm magnets of the LHC (MBXW, MQW, MSI, MSD, etc…) will be coated with a Ti-Zr-V thin film by magnetron sputtering. The NEG coating is necessary to provide uniform pumping speed along the chambers and to suppress electron cloud instabilities and dynamic outgassing. The about 300 chambers will be coated using the existing facility, developed for the production of the standard LSS chambers, after minor modifications mainly due to the different cross sections. In order to cope with the present installation schedule, the production planning will allow processing of different families of chambers in parallel by using two or three coating systems simultaneously. After a brief introduction to the Ti-Zr-V characteristics and performances, the coating facility and strategy will be illustrated as well as the possible conflicts due to uncertainties in the planning of the experimental beam pipes and the standard LSS chambers.

Study of the transport parameters of cloud lightning plasmas

International Nuclear Information System (INIS)

Chang, Z. S.; Yuan, P.; Zhao, N.

2010-01-01

Three spectra of cloud lightning have been acquired in Tibet (China) using a slitless grating spectrograph. The electrical conductivity, the electron thermal conductivity, and the electron thermal diffusivity of the cloud lightning, for the first time, are calculated by applying the transport theory of air plasma. In addition, we investigate the change behaviors of parameters (the temperature, the electron density, the electrical conductivity, the electron thermal conductivity, and the electron thermal diffusivity) in one of the cloud lightning channels. The result shows that these parameters decrease slightly along developing direction of the cloud lightning channel. Moreover, they represent similar sudden change behavior in tortuous positions and the branch of the cloud lightning channel.

Velocity-resolved [{\\rm{C}}\\,{\\rm{II}}] Emission from Cold Diffuse Clouds in the Interstellar Medium

Science.gov (United States)

Goldsmith, Paul F.; Pineda, Jorge L.; Neufeld, David A.; Wolfire, Mark G.; Risacher, Christophe; Simon, Robert

2018-04-01

We have combined emission from the 158 μm fine structure transition of C+ observed with the GREAT and upGREAT instruments on SOFIA with 21 cm absorption spectra and visual extinction to characterize the diffuse interstellar clouds found along the lines of sight. The weak [C II] emission is consistent in velocity and line width with the strongest H I component produced by the cold neutral medium. The H I column density and kinetic temperature are known from the 21 cm data and, assuming a fractional abundance of ionized carbon, we calculate the volume density and thermal pressure of each source, which vary considerably, with 27 {cm}}-3≤slant n({{{H}}}0) ≤slant 210 cm‑3 considering only the atomic hydrogen along the lines of sight to be responsible for the C+, while 13 {cm}}-3≤slant n({{{H}}}0+{{{H}}}2)≤slant 190 cm‑3 including the hydrogen in both forms. The thermal pressure varies widely with 1970 cm‑3 K ≤slant {P}th}/k≤slant 10,440 cm‑3 K for H0 alone and 750 cm‑3 K ≤ P th/k ≤ 9360 cm‑3 K including both H0 and H2. The molecular hydrogen fraction varies between 0.10 and 0.67. Photoelectric heating is the dominant heating source, supplemented by a moderately enhanced cosmic ray ionization rate, constrained by the relatively low 45 K to 73 K gas temperatures of the clouds. The resulting thermal balance for the two lower-density clouds is satisfactory, but for the two higher-density clouds, the combined heating rate is insufficient to balance the observed C+ cooling.

A study of the link between cosmic rays and clouds with a cloud chamber at the CERN PS

CERN Document Server

Fastrup, B; Lillestøl, Egil; Thorn, E; Bosteels, Michel; Gonidec, A; Harigel, G G; Kirkby, Jasper; Mele, S; Minginette, P; Nicquevert, Bertrand; Schinzel, D; Seidl, W; Grundsøe, P; Marsh, N D; Polny, J; Svensmark, H; Viisanen, Y; Kurvinen, K L; Orava, Risto; Hämeri, K; Kulmala, M; Laakso, I; Mäkelä, J M; O'Dowd, C D; Afrosimov, V; Basalaev, A; Panov, M; Laaksonen, B D; Joutsensaari, J; Ermakov, V; Makhmutov, V S; Maksumov, O; Pokrevsky, P; Stozhkov, Yu I; Svirzhevsky, N S; Carslaw, K; Yin, Y; Trautmann, T; Arnold, F; Wohlfrom, K H; Hagen, D; Schmitt, J; Whitefield, P; Aplin, K; Harrison, R G; Bingham, R; Close, Francis Edwin; Gibbins, C; Irving, A; Kellett, B; Lockwood, M; Petersen, D; Szymanski, W W; Wagner, P E; Vrtala, A; CERN. Geneva. SPS-PS Experiments Committee

2000-01-01

Recent satellite data have revealed a surprising correlation between galactic cosmic ray (GCR) intensity and the fraction of the Earth covered by clouds. If this correlation were to be established by a causal mechanism, it could provide a crucial step in understanding the long-sought mechanism connecting solar and climate variability. The Earth's climate seems to be remarkably sensitive to solar activity, but variations of the Sun's electromagnetic radiation appear to be too small to account for the observed climate variability. However, since the GCR intensity is strongly modulated by the solar wind, a GCR-cloud link may provide a sufficient amplifying mechanism. Moreover if this connection were to be confirmed, it could have profound consequences for our understanding of the solar contributions to the current global warming. The CLOUD (Cosmics Leaving OUtdoor Droplets) project proposes to test experimentally the existence a link between cosmic rays and cloud formation, and to understand the microphysical me...

Time-resolved Shielded-Pickup Measurements and Modeling of Beam Conditioning Effects on Electron Cloud Buildup at CesrTA

CERN Document Server

Crittenden, J A; Liu, X; Palmer, M A; Santos, S; Sikora, J P; Kato, S; Calatroni, S; Rumolo, G

2012-01-01

The Cornell Electron Storage Ring Test Accelerator program includes investigations into electron cloud buildup in vacuum chambers with various coatings. Two 1.1-mlong sections located symmetrically in the east and west arc regions are equipped with BPM-like pickup detectors shielded against the direct beam-induced signal. They detect cloud electrons migrating through an 18-mm-diameter pattern of 0.76 mm-diameter holes in the top of the chamber. A digitizing oscilloscope is used to record the signals, providing time-resolved information on cloud development. We present new measurements of the effect of beam conditioning on a newly-installed amorphous carbon coated chamber, as well as on an extensively conditioned chamber with a diamond-like carbon coating. The ECLOUD modeling code is used to quantify the sensitivity of these measurements to model parameters, differentiating between photoelectron and secondary-electron production processes.

Shielded button electrodes for time-resolved measurements of electron cloud buildup

International Nuclear Information System (INIS)

Crittenden, J.A.; Billing, M.G.; Li, Y.; Palmer, M.A.; Sikora, J.P.

2014-01-01

We report on the design, deployment and signal analysis for shielded button electrodes sensitive to electron cloud buildup at the Cornell Electron Storage Ring. These simple detectors, derived from a beam-position monitor electrode design, have provided detailed information on the physical processes underlying the local production and the lifetime of electron densities in the storage ring. Digitizing oscilloscopes are used to record electron fluxes incident on the vacuum chamber wall in 1024 time steps of 100 ps or more. The fine time steps provide a detailed characterization of the cloud, allowing the independent estimation of processes contributing on differing time scales and providing sensitivity to the characteristic kinetic energies of the electrons making up the cloud. By varying the spacing and population of electron and positron beam bunches, we map the time development of the various cloud production and re-absorption processes. The excellent reproducibility of the measurements also permits the measurement of long-term conditioning of vacuum chamber surfaces

Origin of CH+ in diffuse molecular clouds. Warm H2 and ion-neutral drift

Science.gov (United States)

Valdivia, Valeska; Godard, Benjamin; Hennebelle, Patrick; Gerin, Maryvonne; Lesaffre, Pierre; Le Bourlot, Jacques

2017-04-01

Context. Molecular clouds are known to be magnetised and to display a turbulent and complex structure where warm and cold phases are interwoven. The turbulent motions within molecular clouds transport molecules, and the presence of magnetic fields induces a relative velocity between neutrals and ions known as the ion-neutral drift (vd). These effects all together can influence the chemical evolution of the clouds. Aims: This paper assesses the roles of two physical phenomena which have previously been invoked to boost the production of CH+ under realistic physical conditions: the presence of warm H2 and the increased formation rate due to the ion-neutral drift. Methods: We performed ideal magnetohydrodynamical (MHD) simulations that include the heating and cooling of the multiphase interstellar medium (ISM), and where we treat dynamically the formation of the H2 molecule. In a post-processing step we compute the abundances of species at chemical equilibrium using a solver that we developed. The solver uses the physical conditions of the gas as input parameters, and can also prescribe the H2 fraction if needed. We validate our approach by showing that the H2 molecule generally has a much longer chemical evolution timescale compared to the other species. Results: We show that CH+ is efficiently formed at the edge of clumps, in regions where the H2 fraction is low (0.3-30%) but nevertheless higher than its equilibrium value, and where the gas temperature is high (≳ 300 K). We show that warm and out of equilibrium H2 increases the integrated column densities of CH+ by one order of magnitude up to values still 3-10 times lower than those observed in the diffuse ISM. We balance the Lorentz force with the ion-neutral drag to estimate the ion-drift velocities from our ideal MHD simulations. We find that the ion-neutral drift velocity distribution peaks around 0.04 km s-1, and that high drift velocities are too rare to have a significant statistical impact on the

Computation of shear-induced collective-diffusivity in emulsions

Science.gov (United States)

Malipeddi, Abhilash Reddy; Sarkar, Kausik

2017-11-01

The shear-induced collective-diffusivity of drops in an emulsion is calculated through simulation. A front-tracking finite difference method is used to integrate the Navier-Stokes equations. When a cloud of drops is subjected to shear flow, after a certain time, the width of the cloud increases with the 1/3 power of time. This scaling of drop-cloud-width with time is characteristic of (sub-)diffusion that arises from irreversible two-drop interactions. The collective diffusivity is calculated from this relationship. A feature of the procedure adopted here is the modest computational requirement, wherein, a few drops ( 70) in shear for short time ( 70 strain) is found to be sufficient to get a good estimate. As far as we know, collective-diffusivity has not been calculated for drops through simulation till now. The computed values match with experimental measurements reported in the literature. The diffusivity in emulsions is calculated for a range of Capillary (Ca) and Reynolds (Re) numbers. It is found to be a unimodal function of Ca , similar to self-diffusivity. A sub-linear increase of the diffusivity with Re is seen for Re < 5 . This work has been limited to a viscosity matched case.

Properties of the electron cloud in a high-energy positron and electron storage ring

International Nuclear Information System (INIS)

Harkay, K.C.; Rosenberg, R.A.

2003-01-01

Low-energy, background electrons are ubiquitous in high-energy particle accelerators. Under certain conditions, interactions between this electron cloud and the high-energy beam can give rise to numerous effects that can seriously degrade the accelerator performance. These effects range from vacuum degradation to collective beam instabilities and emittance blowup. Although electron-cloud effects were first observed two decades ago in a few proton storage rings, they have in recent years been widely observed and intensely studied in positron and proton rings. Electron-cloud diagnostics developed at the Advanced Photon Source enabled for the first time detailed, direct characterization of the electron-cloud properties in a positron and electron storage ring. From in situ measurements of the electron flux and energy distribution at the vacuum chamber wall, electron-cloud production mechanisms and details of the beam-cloud interaction can be inferred. A significant longitudinal variation of the electron cloud is also observed, due primarily to geometrical details of the vacuum chamber. Such experimental data can be used to provide realistic limits on key input parameters in modeling efforts, leading ultimately to greater confidence in predicting electron-cloud effects in future accelerators.

Effect of chamber enclosure time on soil respiration flux: A comparison of linear and non-linear flux calculation methods

DEFF Research Database (Denmark)

Kandel, Tanka P; Lærke, Poul Erik; Elsgaard, Lars

2016-01-01

One of the shortcomings of closed chamber methods for soil respiration (SR) measurements is the decreased CO2 diffusion rate from soil to chamber headspace that may occur due to increased chamber CO2 concentrations. This feedback on diffusion rate may lead to underestimation of pre-deployment flu......One of the shortcomings of closed chamber methods for soil respiration (SR) measurements is the decreased CO2 diffusion rate from soil to chamber headspace that may occur due to increased chamber CO2 concentrations. This feedback on diffusion rate may lead to underestimation of pre...... was placed on fixed collars, and CO2 concentration in the chamber headspace were recorded at 1-s intervals for 45 min. Fluxes were measured in different soil types (sandy, sandy loam and organic soils), and for various manipulations (tillage, rain and drought) and soil conditions (temperature and moisture......) to obtain a range of fluxes with different shapes of flux curves. The linear method provided more stable flux results during short enclosure times (few min) but underestimated initial fluxes by 15–300% after 45 min deployment time. Non-linear models reduced the underestimation as average underestimation...

Global vertical mass transport by clouds - A two-dimensional model study

International Nuclear Information System (INIS)

Olofsson, Mats

1988-05-01

A two-dimensional global dispersion model, where vertical transport in the troposphere carried out by convective as well as by frontal cloud systems is explicitly treated, is developed from an existing diffusion model. A parameterization scheme for the cloud transport, based on global cloud statistics, is presented. The model has been tested by using Kr-85, Rn-222 and SO 2 as tracers. Comparisons have been made with observed distributions of these tracers, but also with model results without the cloud transport, using eddy diffusion as the primary means of vertical transport. The model results indicate that for trace species with a turnover time of days to weeks, the introduction of cloud-transport gives much more realistic simulations of their vertical distribution. Layers of increased mixing ratio with height, which can be found in real atmosphere, are reproduced in our cloud-transport model profiles, but can never be simulated with a pure eddy diffusion model. The horizontal transport in the model, by advection and eddy diffusion, gives a realistic distribution between the hemispheres of the more long-lived tracers (Kr-85). A combination of vertical transport by convective and frontal cloud systems is shown to improve the model simulations, compared to limiting it to convective transport only. The importance of including cumulus clouds in the convective transport scheme, in addition to the efficient transport by cumulonimbus clouds, is discussed. The model results are shown to be more sensitive to the vertical detrainment distribution profile than to the absolute magnitude of the vertical mass transport. The scavenging processes for SO 2 are parameterized without the introduction of detailed chemistry. An enhanced removal, due to the increased contact with droplets in the in-cloud lifting process, is introduced in the model. (author)

Properties of low-pressure drift chambers

International Nuclear Information System (INIS)

Breskin, A.; Trautner, N.

1976-01-01

Drift chambers operated with methylal vapour or ethylene at pressures in the range of 10-110 torr are described. A systematic study of position resolution, pulse height and rise time shows that especially for ethylene they are strongly influenced by electron diffusion. Intrinsic position resolution was found to be at least as good as found at atmospheric pressure. A relative pulse height resolution of 10% was obtained with 5.5 MeV alpha-particles. A simple mathematical model which can describe the processes in the drift chamber is presented. (Auth.)

Comprehensive models of diffuse interstellar clouds : physical conditions and molecular abundances

NARCIS (Netherlands)

Dishoeck, van E.F.; Black, J.H.

1986-01-01

The limitations of steady state models of interstellar clouds are explored by means of comparison with observational data corresponding to clouds in front of Zeta Per, Zeta Oph, Chi Oph, and Omicron Per. The improved cloud models were constructed to reproduce the observed H and H2(J) column

submitter Aqueous phase oxidation of sulphur dioxide by ozone in cloud droplets

CERN Document Server

Hoyle, C R; Järvinen, E; Saathoff, H; Dias, A; El Haddad, I; Gysel, M; Coburn, S C; Tröstl, J; Bernhammer, A -K; Bianchi, F; Breitenlechner, M; Corbin, J C; Craven, J; Donahue, N M; Duplissy, J; Ehrhart, S; Frege, C; Gordon, H; Höppel, N; Heinritzi, M; Kristensen, T B; Molteni, U; Nichman, L; Pinterich, T; Prévôt, A S H; Simon, M; Slowik, J G; Steiner, G; Tomé, A; Vogel, A L; Volkamer, R; Wagner, A C; Wagner, R; Wexler, A S; Williamson, C; Winkler, P M; Yan, C; Amorim, A; Dommen, J; Curtius, J; Gallagher, M W; Flagan, R C; Hansel, A; Kirkby, J; Kulmala, M; Möhler, O; Stratmann, F; Worsnop, D R; Baltensperger, U

2016-01-01

The growth of aerosol due to the aqueous phase oxidation of sulfur dioxide by ozone was measured in laboratory-generated clouds created in the Cosmics Leaving OUtdoor Droplets (CLOUD) chamber at the European Organization for Nuclear Research (CERN). Experiments were performed at 10 and −10 °C, on acidic (sulfuric acid) and on partially to fully neutralised (ammonium sulfate) seed aerosol. Clouds were generated by performing an adiabatic expansion – pressurising the chamber to 220 hPa above atmospheric pressure, and then rapidly releasing the excess pressure, resulting in a cooling, condensation of water on the aerosol and a cloud lifetime of approximately 6 min. A model was developed to compare the observed aerosol growth with that predicted using oxidation rate constants previously measured in bulk solutions. The model captured the measured aerosol growth very well for experiments performed at 10 and −10 °C, indicating that, in contrast to some previous studies, the oxidation rates of SO2 in ...

Cosmic rays,Climate and the CERN CLOUD Experiment

CERN Multimedia

CERN. Geneva

2011-01-01

For more than two centuries, scientists have been puzzled by observations of solar-climate variability yet the lack of any established physical mechanism. Some recent observations, although disputed, suggest that clouds may be influenced by cosmic rays, which are modulated by the solar wind. The CLOUD experiment aims to settle the question of whether or not cosmic rays have a climatically-significant effect on clouds by carrying out a series of carefully-controlled measurements in a large cloud chamber exposed to a beam from the CERN PS. This talk will present the scientific motivation for CLOUD and the first results, which have recently been published in Nature (Kirkby et al. (2011). Role of sulphuric acid, ammonia and galactic cosmic rays in atmospheric aerosol nucleation. Nature 476, 429-433).

Laboratory Course on Drift Chambers

International Nuclear Information System (INIS)

Garcia-Ferreira, Ix-B.; Garcia-Herrera, J.; Villasenor, L.

2006-01-01

Drift chambers play an important role in particle physics experiments as tracking detectors. We started this laboratory course with a brief review of the theoretical background and then moved on to the the experimental setup which consisted of a single-sided, single-cell drift chamber. We also used a plastic scintillator paddle, standard P-10 gas mixture (90% Ar, 10% CH4) and a collimated 90Sr source. During the laboratory session the students performend measurements of the following quantities: a) drift velocities and their variations as function of the drift field; b) gas gains and c) diffusion of electrons as they drifted in the gas

The Horizontal Ice Nucleation Chamber (HINC): INP measurements at conditions relevant for mixed-phase clouds at the High Altitude Research Station Jungfraujoch

Science.gov (United States)

Lacher, Larissa; Lohmann, Ulrike; Boose, Yvonne; Zipori, Assaf; Herrmann, Erik; Bukowiecki, Nicolas; Steinbacher, Martin; Kanji, Zamin A.

2017-12-01

In this work we describe the Horizontal Ice Nucleation Chamber (HINC) as a new instrument to measure ambient ice-nucleating particle (INP) concentrations for conditions relevant to mixed-phase clouds. Laboratory verification and validation experiments confirm the accuracy of the thermodynamic conditions of temperature (T) and relative humidity (RH) in HINC with uncertainties in T of ±0.4 K and in RH with respect to water (RHw) of ±1.5 %, which translates into an uncertainty in RH with respect to ice (RHi) of ±3.0 % at T > 235 K. For further validation of HINC as a field instrument, two measurement campaigns were conducted in winters 2015 and 2016 at the High Altitude Research Station Jungfraujoch (JFJ; Switzerland, 3580 m a. s. l. ) to sample ambient INPs. During winters 2015 and 2016 the site encountered free-tropospheric conditions 92 and 79 % of the time, respectively. We measured INP concentrations at 242 K at water-subsaturated conditions (RHw = 94 %), relevant for the formation of ice clouds, and in the water-supersaturated regime (RHw = 104 %) to represent ice formation occurring under mixed-phase cloud conditions. In winters 2015 and 2016 the median INP concentrations at RHw = 94 % was below the minimum detectable concentration. At RHw = 104 %, INP concentrations were an order of magnitude higher, with median concentrations in winter 2015 of 2.8 per standard liter (std L-1; normalized to standard T of 273 K and pressure, p, of 1013 hPa) and 4.7 std L-1 in winter 2016. The measurements are in agreement with previous winter measurements obtained with the Portable Ice Nucleation Chamber (PINC) of 2.2 std L-1 at the same location. During winter 2015, two events caused the INP concentrations at RHw = 104 % to significantly increase above the campaign average. First, an increase to 72.1 std L-1 was measured during an event influenced by marine air, arriving at the JFJ from the North Sea and the Norwegian Sea. The contribution from anthropogenic or other

Heterogeneous ice nucleation activity of bacteria: new laboratory experiments at simulated cloud conditions

Directory of Open Access Journals (Sweden)

O. Möhler

2008-10-01

Full Text Available The ice nucleation activities of five different Pseudomonas syringae, Pseudomonas viridiflava and Erwinia herbicola bacterial species and of Snomax™ were investigated in the temperature range between −5 and −15°C. Water suspensions of these bacteria were directly sprayed into the cloud chamber of the AIDA facility of Forschungszentrum Karlsruhe at a temperature of −5.7°C. At this temperature, about 1% of the Snomax™ cells induced immersion freezing of the spray droplets before the droplets evaporated in the cloud chamber. The living cells didn't induce any detectable immersion freezing in the spray droplets at −5.7°C. After evaporation of the spray droplets the bacterial cells remained as aerosol particles in the cloud chamber and were exposed to typical cloud formation conditions in experiments with expansion cooling to about −11°C. During these experiments, the bacterial cells first acted as cloud condensation nuclei to form cloud droplets. Then, only a minor fraction of the cells acted as heterogeneous ice nuclei either in the condensation or the immersion mode. The results indicate that the bacteria investigated in the present study are mainly ice active in the temperature range between −7 and −11°C with an ice nucleation (IN active fraction of the order of 10⁻⁴. In agreement to previous literature results, the ice nucleation efficiency of Snomax™ cells was much larger with an IN active fraction of 0.2 at temperatures around −8°C.

Diffusive-to-ballistic transition of the modulated heat transport in a rarefied air chamber

Directory of Open Access Journals (Sweden)

C. L. Gomez-Heredia

2017-01-01

Full Text Available Modulated heat transfer in air subject to pressures from 760 Torr to 10-4 Torr is experimentally studied by means of a thermal-wave resonant cavity placed in a vacuum chamber. This is done through the analysis of the amplitude and phase delay of the photothermal signal as a function of the cavity length and pressure through of the Knudsen’s number. The viscous, transitional, and free molecular regimes of heat transport are observed for pressures P>1.5 Torr, 25 mTorrdiffusive and ballistic heat transport.

Vertical microphysical profiles of convective clouds as a tool for obtaining aerosol cloud-mediated climate forcings

Energy Technology Data Exchange (ETDEWEB)

Rosenfeld, Daniel [Hebrew Univ. of Jerusalem (Israel)

2015-12-23

Quantifying the aerosol/cloud-mediated radiative effect at a global scale requires simultaneous satellite retrievals of cloud condensation nuclei (CCN) concentrations and cloud base updraft velocities (Wb). Hitherto, the inability to do so has been a major cause of high uncertainty regarding anthropogenic aerosol/cloud-mediated radiative forcing. This can be addressed by the emerging capability of estimating CCN and Wb of boundary layer convective clouds from an operational polar orbiting weather satellite. Our methodology uses such clouds as an effective analog for CCN chambers. The cloud base supersaturation (S) is determined by Wb and the satellite-retrieved cloud base drop concentrations (Ndb), which is the same as CCN(S). Developing and validating this methodology was possible thanks to the ASR/ARM measurements of CCN and vertical updraft profiles. Validation against ground-based CCN instruments at the ARM sites in Oklahoma, Manaus, and onboard a ship in the northeast Pacific showed a retrieval accuracy of ±25% to ±30% for individual satellite overpasses. The methodology is presently limited to boundary layer not raining convective clouds of at least 1 km depth that are not obscured by upper layer clouds, including semitransparent cirrus. The limitation for small solar backscattering angles of <25º restricts the satellite coverage to ~25% of the world area in a single day. This methodology will likely allow overcoming the challenge of quantifying the aerosol indirect effect and facilitate a substantial reduction of the uncertainty in anthropogenic climate forcing.

Pre-eruptive magmatic processes re-timed using a non-isothermal approach to magma chamber dynamics.

Science.gov (United States)

Petrone, Chiara Maria; Bugatti, Giuseppe; Braschi, Eleonora; Tommasini, Simone

2016-10-05

Constraining the timescales of pre-eruptive magmatic processes in active volcanic systems is paramount to understand magma chamber dynamics and the triggers for volcanic eruptions. Temporal information of magmatic processes is locked within the chemical zoning profiles of crystals but can be accessed by means of elemental diffusion chronometry. Mineral compositional zoning testifies to the occurrence of substantial temperature differences within magma chambers, which often bias the estimated timescales in the case of multi-stage zoned minerals. Here we propose a new Non-Isothermal Diffusion Incremental Step model to take into account the non-isothermal nature of pre-eruptive processes, deconstructing the main core-rim diffusion profiles of multi-zoned crystals into different isothermal steps. The Non-Isothermal Diffusion Incremental Step model represents a significant improvement in the reconstruction of crystal lifetime histories. Unravelling stepwise timescales at contrasting temperatures provides a novel approach to constraining pre-eruptive magmatic processes and greatly increases our understanding of magma chamber dynamics.

New Electron Cloud Detectors for the PS Main Magnets

CERN Document Server

Yin Vallgren, Ch; Gilardoni, S; Taborelli, M; Neupert, H; Ferreira Somoza, J

2014-01-01

Electron cloud (EC) has already been observed during normal operation of the PS, therefore it is necessary to study its in fluence on any beam instability for the future LHC Injector Upgrade (LIU). Two new electron cloud detectors have been discussed, developed and installed during the Long Shutdown (LS1) in one of the PS main magnets. The first measurement method is based on current measurement by using a shielded button-type pick-up. Due to the geometry and space limitation in the PS magnet, the button-type pick-up made of a 96%Al2O3 block coated with a thin layer of solvent-based Ag painting, placed 30 degrees to the bottom part of the vacuum chamber was installed in the horizontal direction where the only opening of the magnet coil is. The other newly developed measurement method is based on detection of photons emitted by the electrons from the electron cloud impinging on the vacuum chamber walls. The emitted photons are reected to a quartz window. A MCP-PMT (Micro-Channel Plate Photomultiplier Tube) wit...

Multipassage diffuser

International Nuclear Information System (INIS)

Lalis, A.; Rouviere, R.; Simon, G.

1976-01-01

A multipassage diffuser having 2p passages comprises a leak-tight cylindrical enclosure closed by a top cover and a bottom end-wall, parallel porous tubes which are rigidly assembled in sectors between tube plates and through which the gas mixture flows, the tube sectors being disposed at uniform intervals on the periphery of the enclosure. The top tube plates are rigidly fixed to an annular header having the shape of a half-torus and adapted to communicate with the tubes of the corresponding sector. Each passage is constituted by a plurality of juxtaposed sectors in which the mixture circulates in the same direction, the header being divided into p portions limited by radial partition-walls and each constituting two adjacent passages. The diffuser is provided beneath the bottom end-wall with p-1 leak-tight chambers each adapted to open into two different portions of the header, and with two collector-chambers each fitted with a nozzle for introducing the gas mixture and discharging the fraction of the undiffused mixture. By means of a central orifice formed in the bottom end-wall the enclosure communicates with a shaft for discharging the diffused fraction of the gas mixture

Atmospheric transport, diffusion, and deposition of radioactivity

International Nuclear Information System (INIS)

Crawford, T.V.

1969-01-01

From a meteorological standpoint there are two types of initial sources for atmospheric diffusion from Plowshare applications. One is the continuous point-source plume - a slow, small leak from an underground engineering application. The other is the large cloud produced almost instantaneously from a cratering application. For the purposes of this paper the effluent from neither type has significant fall speed. Both are carried by the prevailing wind, but the statistics of diffusion for each type are different. The use of constant altitude, isobaric and isentropic techniques for predicting the mean path of the effluent is briefly discussed. Limited data are used to assess the accuracy of current trajectory forecast techniques. Diffusion of continuous point-source plumes has been widely studied; only a brief review is given of the technique used and the variability of their results with wind speed and atmospheric stability. A numerical model is presented for computing the diffusion of the 'instantaneously-produced' large clouds. This model accounts for vertical and diurnal changes in atmospheric turbulence, wet and dry deposition, and radioactivity decay. Airborne concentrations, cloud size, and deposition on the ground are calculated. Pre- and post-shot calculations of cloud center, ground level concentration of gross radioactivity, and dry and wet deposition of iodine-131 are compared with measurements on Cabriolet and Buggy. (author)

Atmospheric transport, diffusion, and deposition of radioactivity

Energy Technology Data Exchange (ETDEWEB)

Crawford, T V [Lawrence Radiation Laboratory, Livermore, CA (United States)

1969-07-01

From a meteorological standpoint there are two types of initial sources for atmospheric diffusion from Plowshare applications. One is the continuous point-source plume - a slow, small leak from an underground engineering application. The other is the large cloud produced almost instantaneously from a cratering application. For the purposes of this paper the effluent from neither type has significant fall speed. Both are carried by the prevailing wind, but the statistics of diffusion for each type are different. The use of constant altitude, isobaric and isentropic techniques for predicting the mean path of the effluent is briefly discussed. Limited data are used to assess the accuracy of current trajectory forecast techniques. Diffusion of continuous point-source plumes has been widely studied; only a brief review is given of the technique used and the variability of their results with wind speed and atmospheric stability. A numerical model is presented for computing the diffusion of the 'instantaneously-produced' large clouds. This model accounts for vertical and diurnal changes in atmospheric turbulence, wet and dry deposition, and radioactivity decay. Airborne concentrations, cloud size, and deposition on the ground are calculated. Pre- and post-shot calculations of cloud center, ground level concentration of gross radioactivity, and dry and wet deposition of iodine-131 are compared with measurements on Cabriolet and Buggy. (author)

Molecular clouds near supernova remnants

International Nuclear Information System (INIS)

Wootten, H.A.

1978-01-01

The physical properties of molecular clouds near supernova remnants were investigated. Various properties of the structure and kinematics of these clouds are used to establish their physical association with well-known remmnants. An infrared survey of the most massive clouds revealed embedded objects, probably stars whose formation was induced by the supernova blast wave. In order to understand the relationship between these and other molecular clouds, a control group of clouds was also observed. Excitation models for dense regions of all the clouds are constructed to evaluate molecular abundances in these regions. Those clouds that have embedded stars have lower molecular abundances than the clouds that do not. A cloud near the W28 supernova remnant also has low abundances. Molecular abundances are used to measure an important parameter, the electron density, which is not directly observable. In some clouds extensive deuterium fractionation is observed which confirms electron density measurements in those clouds. Where large deuterium fractionation is observed, the ionization rate in the cloud interior can also be measured. The electron density and ionization rate in the cloud near W28 are higher than in most clouds. The molecular abundances and electron densities are functions of the chemical and dynamical state of evolution of the cloud. Those clouds with lowest abundances are probably the youngest clouds. As low-abundance clouds, some clouds near supernova remnants may have been recently swept from the local interstellar material. Supernova remnants provide sites for star formation in ambient clouds by compressing them, and they sweep new clouds from more diffuse local matter

Diffusion of protein through the human cornea.

Science.gov (United States)

Charalel, Resmi A; Engberg, Kristin; Noolandi, Jaan; Cochran, Jennifer R; Frank, Curtis; Ta, Christopher N

2012-01-01

To determine the rate of diffusion of myoglobin and bovine serum albumin (BSA) through the human cornea. These small proteins have hydrodynamic diameters of approximately 4.4 and 7.2 nm, and molecular weights of 16.7 and 66 kDa, for myoglobin and BSA, respectively. Diffusion coefficients were measured using a diffusion chamber where the protein of interest and balanced salt solution were in different chambers separated by an ex vivo human cornea. Protein concentrations in the balanced salt solution chamber were measured over time. Diffusion coefficients were calculated using equations derived from Fick's law and conservation of mass in a closed system. Our experiments demonstrate that the diffusion coefficient of myoglobin is 5.5 ± 0.9 × 10(-8) cm(2)/s (n = 8; SD = 1.3 × 10(-8) cm(2)/s; 95% CI: 4.6 × 10(-8) to 6.4 × 10(-8) cm(2)/s) and the diffusion coefficient of BSA is 3.1 ± 1.0 × 10(-8) cm(2)/s (n = 8; SD = 1.4 × 10(-8) cm(2)/s; 95% CI: 2.1 × 10(-8) to 4.1 × 10(-8) cm(2)/s). Our study suggests that molecules as large as 7.2 nm may be able to passively diffuse through the human cornea. With applications in pharmacotherapy and the development of an artificial cornea, further experiments are warranted to fully understand the limits of human corneal diffusion and its clinical relevance. Copyright © 2012 S. Karger AG, Basel.

DIFFUSION OF MAGNETIC FIELD AND REMOVAL OF MAGNETIC FLUX FROM CLOUDS VIA TURBULENT RECONNECTION

International Nuclear Information System (INIS)

Santos-Lima, R.; De Gouveia Dal Pino, E. M.; Lazarian, A.; Cho, J.

2010-01-01

The diffusion of astrophysical magnetic fields in conducting fluids in the presence of turbulence depends on whether magnetic fields can change their topology via reconnection in highly conducting media. Recent progress in understanding fast magnetic reconnection in the presence of turbulence reassures that the magnetic field behavior in computer simulations and turbulent astrophysical environments is similar, as far as magnetic reconnection is concerned. This makes it meaningful to perform MHD simulations of turbulent flows in order to understand the diffusion of magnetic field in astrophysical environments. Our studies of magnetic field diffusion in turbulent medium reveal interesting new phenomena. First of all, our three-dimensional MHD simulations initiated with anti-correlating magnetic field and gaseous density exhibit at later times a de-correlation of the magnetic field and density, which corresponds well to the observations of the interstellar media. While earlier studies stressed the role of either ambipolar diffusion or time-dependent turbulent fluctuations for de-correlating magnetic field and density, we get the effect of permanent de-correlation with one fluid code, i.e., without invoking ambipolar diffusion. In addition, in the presence of gravity and turbulence, our three-dimensional simulations show the decrease of the magnetic flux-to-mass ratio as the gaseous density at the center of the gravitational potential increases. We observe this effect both in the situations when we start with equilibrium distributions of gas and magnetic field and when we follow the evolution of collapsing dynamically unstable configurations. Thus, the process of turbulent magnetic field removal should be applicable both to quasi-static subcritical molecular clouds and cores and violently collapsing supercritical entities. The increase of the gravitational potential as well as the magnetization of the gas increases the segregation of the mass and magnetic flux in the

Experimental evidence for millisecond activation timescales using the Fast IN Chamber (FINCH) measurements

Science.gov (United States)

Bundke, U.; Jaenicke, R.; Klein, H.; Nillius, B.; Reimann, B.; Wetter, T.; Bingemer, H.

2009-04-01

Ice formation in clouds is a subject of great practical and fundamental importance since the occurrence of ice particle initializes dramatic changes in the microphysical structure of the cloud, which finally ends in the formation of precipitation. The initially step of ice formation is largely unknown. Homogenous nucleation of ice occurs only below -40 °C. If an ice nucleus (IN) is present, heterogeneous nucleation may occur at higher temperature. Here deposition freezing, condensation and immersion freezing as well as contact freezing are known. Also growth rates of ice particles are known as function of crystal surface properties, temperature and super saturation. Timescales for homogenous freezing activation in the order of 0.01 seconds and nucleation rates have been measured by Anderson et al. (1980) and Hagen et al., (1981) using their expansion cloud chamber. This contribution of deposition mode freezing measurements by the ice nucleus counter FINCH presents evidence that the activation timescale of this freezing mode is in the order of 1E-3 seconds. FINCH is an Ice Nucleus counter which activates IN in a supersaturated environment at freezing temperatures. The activation conditions are actively controlled by mixing three gas flows (aerosol, particle-free cold-dry and warm-humid flows).See Bundke et al. 2008 for details. In a special operation mode of FINCH we are able to produce a controlled peak super saturation in the order of 1 ms duration. For several test aerosols the results observed in this particular mode are comparable to normal mode operations, where the maximum super saturation remains for more than a second, thus leading to the conclusion that the time for activation is in the order of 1ms or less. References: R.J. Anderson et al, "A Study of Homogeneous Condensation Freezing Nucleation of Small Water Droplets in an Expansion Cloud Chamber, Journal of the Atmospheric Sciences, Vol. 37, 2508-2520, 1980 U.Bundke et al., "The fast Ice Nucleus

Results from the CERN pilot CLOUD experiment

DEFF Research Database (Denmark)

Duplissy, J.; Enghoff, Martin Andreas Bødker; Aplin, K. L.

2009-01-01

is involved in the nucleation of atmospheric aerosols. However, sulphuric acid alone is not able to explain the observed rapid growth rates, which suggests the presence of additional trace vapours in the aerosol chamber, whose identity is unknown. By analysing the charged fraction, a few of the aerosol bursts...... are needed in controlling the experimental variables and in the reproducibility of the experiments. Finally, concerning technical aspects, the most important lessons for the CLOUD design include the stringent requirement of internal cleanliness of the aerosol chamber, as well as maintenance of extremely...

Islands in the Sky: Ecophysiological Cloud-Vegetation Linkages in Southern Appalachian Mountain Cloud Forests

Science.gov (United States)

Reinhardt, K.; Emanuel, R. E.; Johnson, D. M.

2013-12-01

photosynthesis occurs during high-light, diffuse-light conditions such as occurs during diffuse 'sunflecks' inside the cloud fog. Additionally, the capacity to respond to brief, intermittent sunflecks ('photosynthetic induction', e.g., time to maximum photosynthesis) was high in our MCF species. 3) Data quantifying limitations to photosynthesis were contradictory, underscoring complex relationships among photosynthesis, light, carbon and water relations. While stomatal response to atmospheric moisture demand was sensitive (e.g., 80% drop in stomatal conductance in a conifer species), stem xylem hydraulic conductivity suggested strong drought tolerance capabilities. CONCLUSIONS: Clouds and cloud-fog exert strong influence on canopy-tree and ecosystem carbon relations. MCF are dynamic light environments. In these highly variable but ultimately light-limited ecosystems, vegetation must be able to both fix carbon when cloudy and dark but also be able to capitalize on saturating sunlight when possible.

Behavior of explosion debris clouds

International Nuclear Information System (INIS)

Anon.

1986-01-01

In the normal course of events the behavior of debris clouds created by explosions will be of little concern to the atomic energy industry. However, two situations, one of them actual and one postulated, exist where the rise and spread of explosion clouds can affect site operations. The actual occurrence would be the detonation of nuclear weapons and the resultant release and transport of radioactive debris across the various atomic energy installations. Although the activity of the diffusing cloud is not of biological concern, it may still be sufficiently above background to play havoc with the normal readings of sensitive monitoring instruments. If it were not known that these anomalous readings resulted from explosion debris, considerable time and expense might be required for on-site testing and tracing. Fortunately it is usually possible, with the use of meteorological data and forecasts, to predict when individual sites are affected by nuclear weapon debris effects. The formation rise, and diffusion of weapon clouds will be discussed. The explosion of an atomic reactor is the postulated situation. It is common practice in reactor hazard analysis to assume a combination of circumstances which might result in a nuclear incident with a release of material to the atmosphere. It is not within the scope of this report to examine the manifold plausibilities that might lead to an explosion or the possible methods of release of gaseous and/or particulates from such an occurrence. However, if the information of a cloud is assumed and some idea of its energy content is obtainable, estimates of the cloud behavior in the atmosphere can be made

The Horizontal Ice Nucleation Chamber (HINC: INP measurements at conditions relevant for mixed-phase clouds at the High Altitude Research Station Jungfraujoch

Directory of Open Access Journals (Sweden)

L. Lacher

2017-12-01

Full Text Available In this work we describe the Horizontal Ice Nucleation Chamber (HINC as a new instrument to measure ambient ice-nucleating particle (INP concentrations for conditions relevant to mixed-phase clouds. Laboratory verification and validation experiments confirm the accuracy of the thermodynamic conditions of temperature (T and relative humidity (RH in HINC with uncertainties in T of ±0.4 K and in RH with respect to water (RHw of ±1.5 %, which translates into an uncertainty in RH with respect to ice (RHi of ±3.0 % at T > 235 K. For further validation of HINC as a field instrument, two measurement campaigns were conducted in winters 2015 and 2016 at the High Altitude Research Station Jungfraujoch (JFJ; Switzerland, 3580 m a. s. l.  to sample ambient INPs. During winters 2015 and 2016 the site encountered free-tropospheric conditions 92 and 79 % of the time, respectively. We measured INP concentrations at 242 K at water-subsaturated conditions (RHw = 94 %, relevant for the formation of ice clouds, and in the water-supersaturated regime (RHw = 104 % to represent ice formation occurring under mixed-phase cloud conditions. In winters 2015 and 2016 the median INP concentrations at RHw = 94 % was below the minimum detectable concentration. At RHw = 104 %, INP concentrations were an order of magnitude higher, with median concentrations in winter 2015 of 2.8 per standard liter (std L−1; normalized to standard T of 273 K and pressure, p, of 1013 hPa and 4.7 std L−1 in winter 2016. The measurements are in agreement with previous winter measurements obtained with the Portable Ice Nucleation Chamber (PINC of 2.2 std L−1 at the same location. During winter 2015, two events caused the INP concentrations at RHw = 104 % to significantly increase above the campaign average. First, an increase to 72.1 std L−1 was measured during an event influenced by marine air, arriving at the JFJ

On the discrepancies between theoretical and measured below-cloud particle scavenging coefficients for rain – a numerical investigation using a detailed one-dimensional cloud microphysics model

Directory of Open Access Journals (Sweden)

X. Wang

2011-11-01

Full Text Available Existing theoretical formulations for the size-resolved scavenging coefficient Λ(d for atmospheric aerosol particles scavenged by rain predict values lower by one to two orders of magnitude than those estimated from field measurements of particle-concentration changes for particles smaller than 3 μm in diameter. Vertical turbulence is not accounted for in the theoretical formulations of Λ(d but does contribute to the field-derived estimates of Λ(d due to its influence on the overall concentration changes of aerosol particles in the layers undergoing impaction scavenging. A detailed one-dimensional cloud microphysics model has been used to simulate rain production and below-cloud particle scavenging, and to quantify the contribution of turbulent diffusion to the overall Λ(d values calculated from particle concentration changes. The relative contribution of vertical diffusion to below-cloud scavenging is found to be largest for submicron particles under weak precipitation conditions. The discrepancies between theoretical and field-derived Λ(d values can largely be explained by the contribution of vertical diffusion to below-cloud particle scavenging for all particles larger than 0.01 μm in diameter for which field data are available. The results presented here suggest that the current theoretical framework for Λ(d can provide a reasonable approximation of below-cloud aerosol particle scavenging by rain in size-resolved aerosol transport models if vertical diffusion is also considered by the models.

Accelerated search of gamma-quantum families in a X-ray emulsion chamber

International Nuclear Information System (INIS)

Takibaev, Zh.S.; Bajgubekov, A.S.; Sadykov, T.Kh.

1977-01-01

The criteria are derived allowing to considerably accelerate the process of detecting the pure gamma-quantum families. The suitable criterion is the apparent size of the distribution of black spots due to electromagnetic cascades inside a circle of specific radius. The results of assaying 27 gamma-families with energies above 3 TeV generated in a target above the chamber are presented. The method of search for the target families suggested in this paper allows to cut four-fold the roentgen-emulsion cloud chamber treatment time

Secondary Electron Yield Measurements and Groove Chambers Tests in the PEP-II Beam Line Straights Sections

International Nuclear Information System (INIS)

Pivi, M

2008-01-01

Beam instability caused by the electron cloud has been observed in positron and proton storage rings and it is expected to be a limiting factor in the performance of the positron Damping Ring (DR) of future Linear Colliders such as ILC and CLIC [1, 2]. In the Positron Low Energy Ring (LER) of the PEP-II accelerator, we have installed vacuum chambers with rectangular grooves in a straight magnetic-free section to test this promising possible electron cloud mitigation technique. We have also installed a special chamber to monitor the secondary electron yield of TiN and TiZrV (NEG) coating, Copper, Stainless Steel and Aluminum under the effect of electron and photon conditioning in situ in the beam line. In this paper, we describe the ongoing R and D effort to mitigate the electron cloud effect for the ILC damping ring, the latest results on in situ secondary electron yield conditioning and recent update on the groove tests in PEP-II

An improved algorithm for calculating cloud radiation

International Nuclear Information System (INIS)

Yuan Guibin; Sun Xiaogang; Dai Jingmin

2005-01-01

Clouds radiation characteristic is very important in cloud scene simulation, weather forecasting, pattern recognition, and other fields. In order to detect missiles against cloud backgrounds, to enhance the fidelity of simulation, it is critical to understand a cloud's thermal radiation model. Firstly, the definition of cloud layer infrared emittance is given. Secondly, the discrimination conditions of judging a pixel of focal plane on a satellite in daytime or night time are shown and equations are given. Radiance such as reflected solar radiance, solar scattering, diffuse solar radiance, solar and thermal sky shine, solar and thermal path radiance, cloud blackbody and background radiance are taken into account. Thirdly, the computing methods of background radiance for daytime and night time are given. Through simulations and comparison, this algorithm is proved to be an effective calculating algorithm for cloud radiation

Vacuum chamber-free centrifuge with magnetic bearings.

Science.gov (United States)

Park, Cheol Hoon; Kim, Soohyun; Kim, Kyung-Soo

2013-09-01

Centrifuges are devices that separate particles of different densities and sizes through the application of a centrifugal force. If a centrifuge could be operated under atmospheric conditions, all vacuum-related components such as the vacuum chamber, vacuum pump, diffusion pump, and sealing could be removed from a conventional centrifuge system. The design and manufacturing procedure for centrifuges could then be greatly simplified to facilitate the production of lightweight centrifuge systems of smaller volume. Furthermore, the maintenance costs incurred owing to wear and tear due to conventional ball bearings would be eliminated. In this study, we describe a novel vacuum chamber-free centrifuge supported by magnetic bearings. We demonstrate the feasibility of the vacuum chamber-free centrifuge by presenting experimental results that verify its high-speed support capability and motoring power capacity.

A new thermal gradient ice nucleation diffusion chamber instrument: design, development and first results using Saharan mineral dust

Directory of Open Access Journals (Sweden)

J. B. McQuaid

2009-06-01

Full Text Available A new Thermal Gradient ice nucleation Diffusion Chamber (TGDC capable of investigating ice nucleation efficiency of atmospherically important aerosols, termed Ice Nuclei (IN, has been designed, constructed and validated. The TGDC can produce a range of supersaturations with respect to ice (SS_i over the temperature range of −10 to −34°C for sufficiently long time needed to observe the ice nucleation by the particles. The novel aspect of this new TGDC is that the chamber is run in static mode with aerosol particles supported on a Teflon substrate, which can be raised and lowered in a controlled way through the SS_i profile within the chamber, and nucleation events are directly observed using digital photography. The TGDC consists of two ice coated plates to which a thermal gradient is applied to produce the range of SS_i. The design of the TGDC gives the ability to understand time-related ice nucleation event information and to perform experiments at different temperatures and SS_i conditions for different IN without changing the thermal gradient within the TGDC. The temperature and SS_i conditions of the experimental system are validated by observing (NH₄₂SO₄ deliquescence and the results are in good agreement with the literature data. First results are presented of the onset ice nucleation for mineral dust sampled from the Saharan Desert, including images of nucleation and statistical distributions of onset ice nucleation SS_i as a function of temperature. This paper illustrates how useful this new TGDC is for process level studies of ice nucleation and more experimental investigations are needed to better quantify the role of ice formation in the atmosphere.

Biological aerosol particles in the atmosphere and their impact on clouds (BIOCLOUDS)

Science.gov (United States)

Amato, Pierre; Attard, Eleonore; Deguillaume, Laurent; Delort, Anne-Marie; Flossmann, Andrea; Good, Nicholas; Joly, Muriel; Koop, Thomas; Möhler, Ottmar; Monier, Marie; Morris, Cindy; Oehm, Caroline; Pöschl, Ulrich; Sancelme, Martine

2015-04-01

The project BIOCLOUDS aimed at investigating and quantifying the role of bioaerosols in tropospheric clouds. We focused on the studies on microorganisms, mainly bacteria. To reach our objective we (1) isolated and identified INA bacterial strains in cloud waters, (2) studied in more details IN properties of bacteria isolated from cloud waters in laboratories and cloud chamber, (3) used new data as input to cloud models. 1. Isolation and Identification of INA bacterial strains in cloud waters Cloud water samples were collected at the puy de Dôme station under sterile conditions, microorganisms were cultured on agar plates and further identified by DNA sequencing coding for16SrRNA. 257 bacterial strains isolated from 25 cloud events were screened and 44 isolates were selected as they belonged to Pseudomonas, Xanthomonas and Erwinia genera which are potential INA candidates. Using the classical "Droplet Freezing method" as ice nucleation test, 7 strains were shown INA+. Their cumulative IN frequency profiles were established and showed that some of them are very efficient, for example the strain Pseudomonas syringae 13b74 started to nucleate a t-3°C and 4% of the cells were active at- 5°C. 2. Further laboratory investigations of IN properties of cloud bacterial strains All the experiments presented in this section were carried out with 3 Pseudomonas syringae strains. We tested the influence of O3, NO, UV and pH, which are atmospheric markers of anthropogenic activity, on the IN activity of the Pseudomonas strains. It was clearly shown that pH had a main influence, acidic pHs decreased the IN activity of the strains. This suggests a negative impact of human emissions on the natural capacity of bacteria to precipitate with rain. The 3 Pseudomas strains were sprayed in the AIDA cloud chamber. The survival of these strains with time before cloud formation was measured and will be used in the future to parameterize models for bacterial transport. After cloud formation

Progress in Studies of Electron-Cloud-Induced Optics Distortions at CesrTA

International Nuclear Information System (INIS)

Crittenden, James; Penn, Gregory; Venturini, Marco; Harkay, Katherine; Holtzapple, Robert; Pivi, Mauro; Wang, Lanfa

2012-01-01

The Cornell Electron Storage Ring Test Accelerator (CesrTA) program has included extensive measurements of coherent betatron tune shifts for a variety of electron and positron beam energies, bunch population levels, and bunch train configurations. The tune shifts have been shown to result primarily from the interaction of the beam with the space-charge field of the beam-induced low-energy electron cloud in the vacuum chamber. Comparison to several advanced electron cloud simulation codes has allowed determination of the sensitivity of these measurements to physical parameters characterizing the synchrotron radiation flux, the production of photo-electrons on the vacuum chamber wall, the beam emittance, lattice optics, and the secondary-electron yield model. We report on progress in understanding the cloud buildup and decay mechanisms in magnetic fields and in field-free regions, addressing quantitatively the precise determination of the physical parameters of the modeling. Validation of these models will serve as essential input in the design of damping rings for future high-energy linear colliders.

Multipactor for e-cloud diagnostics

CERN Document Server

Costa Pinto, P; Edwards, P; Holz, M; Taborelli, M

2012-01-01

Electron cloud in particle accelerators can be mitigated by coating the vacuum beam pipe with thin films of low secondary electron yield (SEY). SEY of small samples can be measured in the laboratory. Verifying the performance of long pipes is more complex, since it requires their insertion in the accelerator and the subsequent measurement of the beam induced pressure rise. RF induced multipacting in a coaxial waveguide configuration is proposed as a test before insertion in the machine. The technique is applied to two main bending dipoles of the SPS, where the RF power is fed through a tungsten wire stretched along the vacuum chamber (6.4 m). A dipole with a bare stainless steel chamber shows a clear power threshold initiating an abrupt rise in reflected power and pressure. The effect is enhanced at RF frequencies corresponding to cyclotron resonances for given magnetic fields. Preliminary results show that the dipole with a carbon coated vacuum chamber does not exhibit any pressure rise or reflected RF power...

Drift Chambers detectors; Detectores de deriva

Energy Technology Data Exchange (ETDEWEB)

Duran, I; Martinez laso, L

1989-07-01

We present here a review of High Energy Physics detectors based on drift chambers. The ionization, drift diffusion, multiplication and detection principles are described. Most common drift media are analysed, and a classification of the detectors according to its geometry is done. Finally the standard read-out methods are displayed and the limits of the spatial resolution are discussed. (Author) 115 refs.

Search for C2- in Diffuse Clouds

Czech Academy of Sciences Publication Activity Database

Civiš, Svatopluk; Hosaki, Y.; Kagi, E.; Izumiura, H.; Yanagisawa, K.; Šedivcová, Tereza; Kawaguchi, K.

2005-01-01

Roč. 57, - (2005), 605-609 ISSN 0004-6264 R&D Projects: GA AV ČR(CZ) IAA4040104; GA MŠk(CZ) LC512 Grant - others:JSPS(JP) C13640247; JSPS(JP) A14204018 Institutional research plan: CEZ:AV0Z40400503; CEZ:AV0Z40550506 Keywords : ISM : clouds * ISM : lines and bands * ISM : molecules * molecular processes Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.376, year: 2005

The Case Of The Elusive Electron Cloud

CERN Multimedia

2001-01-01

Fig. 1 Electron cloud following a controlled beam bump. 'Elementary my dear Watson, you see this footprint proves it was the butler in the foyer with the butcher's knife.' Sir Arthur Conan Doyle's Sherlock Holmes may at first appear a long way from particle physics, but first appearances are often deceiving... The mysteries behind the 'Electron Cloud Effect', a dangerous electron multiplication phenomenon which could possibly limit the LHC's performance, have recently been under a detective level investigation that is yielding data that would make even the valiant Holmes balk. The electron cloud, a group of free floating electrons in the collider, is caused by electron multiplication on the vacuum chamber wall and was first observed in 1976. The cloud that develops is a serious problem because it can lead to beam growth, increased gas release from the collider surface, and a supplementary heat load to the LHC cryogenic system. The phenomenon has been observed since 1999 in the SPS where unexpected pressure...

Estimation of diffuse from measured global solar radiation

International Nuclear Information System (INIS)

Moriarty, W.W.

1991-01-01

A data set of quality controlled radiation observations from stations scattered throughout Australia was formed and further screened to remove residual doubtful observations. It was then divided into groups by solar elevation, and used to find average relationships for each elevation group between relative global radiation (clearness index - the measured global radiation expressed as a proportion of the radiation on a horizontal surface at the top of the atmosphere) and relative diffuse radiation. Clear-cut relationships were found, which were then fitted by polynomial expressions giving the relative diffuse radiation as a function of relative global radiation and solar elevation. When these expressions were used to estimate the diffuse radiation from the global, the results had a slightly smaller spread of errors than those from an earlier technique given by Spencer. It was found that the errors were related to cloud amount, and further relationships were developed giving the errors as functions of global radiation, solar elevation, and the fraction of sky obscured by high cloud and by opaque (low and middle level) cloud. When these relationships were used to adjust the first estimates of diffuse radiation, there was a considerable reduction in the number of large errors

Distribution of multi-component solvents in solvent vapor extraction chamber

Energy Technology Data Exchange (ETDEWEB)

Das, S. [Society of Petroleum Engineers, Richardson, TX (United States)]|[Marathon Oil Corp., Houston, TX (United States)

2008-10-15

Vapex process performance is sensitive to operating pressures, temperatures and the types of solvent used. The hydrocarbon solvents used in Vapex processes typically have between 5 and 10 per cent hydrocarbon impurities, and the accumulation of dense phases inside the vapor chamber reduces gravity drainage potential. This study investigated the partitioning of solvent compounds inside the vapor chamber during in situ Vapex processes.The aim of the study was to examine how the different components of the mixed solvent partitioned inside the extracted chamber during the oil and vapor phase. A 2-D homogenous reservoir model was used to simulate the Vapex process with a solvent mixture comprised of propane and methane at various percentages. The effect of injecting a hot solvent vapor was also investigated. The study showed that injected methane accumulated at both the top and the extraction interface. Accumulations near the top had a positive impact on solvent confinement in thin reservoirs. Diffusion of the solvent component was controlled by gas phase molecular diffusion, and was much faster than the diffusion of solvent molecules in the liquid phase. The use of hot solvent mixtures slowed the extraction process due to lower solvent solubility in the oil phase. It was concluded that the negative impact on viscosity reduction by dilution was not compensated by rises in temperature. 6 refs., 11 figs.

Cloud Processing of Secondary Organic Aerosol from Isoprene and Methacrolein Photooxidation.

Science.gov (United States)

Giorio, Chiara; Monod, Anne; Brégonzio-Rozier, Lola; DeWitt, Helen Langley; Cazaunau, Mathieu; Temime-Roussel, Brice; Gratien, Aline; Michoud, Vincent; Pangui, Edouard; Ravier, Sylvain; Zielinski, Arthur T; Tapparo, Andrea; Vermeylen, Reinhilde; Claeys, Magda; Voisin, Didier; Kalberer, Markus; Doussin, Jean-François

2017-10-12

Aerosol-cloud interaction contributes to the largest uncertainties in the estimation and interpretation of the Earth's changing energy budget. The present study explores experimentally the impacts of water condensation-evaporation events, mimicking processes occurring in atmospheric clouds, on the molecular composition of secondary organic aerosol (SOA) from the photooxidation of methacrolein. A range of on- and off-line mass spectrometry techniques were used to obtain a detailed chemical characterization of SOA formed in control experiments in dry conditions, in triphasic experiments simulating gas-particle-cloud droplet interactions (starting from dry conditions and from 60% relative humidity (RH)), and in bulk aqueous-phase experiments. We observed that cloud events trigger fast SOA formation accompanied by evaporative losses. These evaporative losses decreased SOA concentration in the simulation chamber by 25-32% upon RH increase, while aqueous SOA was found to be metastable and slowly evaporated after cloud dissipation. In the simulation chamber, SOA composition measured with a high-resolution time-of-flight aerosol mass spectrometer, did not change during cloud events compared with high RH conditions (RH > 80%). In all experiments, off-line mass spectrometry techniques emphasize the critical role of 2-methylglyceric acid as a major product of isoprene chemistry, as an important contributor to the total SOA mass (15-20%) and as a key building block of oligomers found in the particulate phase. Interestingly, the comparison between the series of oligomers obtained from experiments performed under different conditions show a markedly different reactivity. In particular, long reaction times at high RH seem to create the conditions for aqueous-phase processing to occur in a more efficient manner than during two relatively short cloud events.

Neutral barium cloud evolution at different altitudes

International Nuclear Information System (INIS)

Li Lei; Xu Ronglan

2002-01-01

Considering the joint effects of diffusion, collision, oxidation and photoionization, the authors study the evolution of the barium cloud at different altitudes in the space plasma active experiment. The results present the variation of the loss rate, number density distribution and brightness of the barium cloud over the range from 120 to 260 km. This can be divided into oxidation, oxidation plus photoionization and photoionization regions

An open-walled ionization chamber appropriate to tritium monitoring for glovebox

International Nuclear Information System (INIS)

Chen Zhilin; Chang Ruiming; Mu Long; Song Guoyang; Wang Heyi; Wu Guanyin; Wei Xiye

2010-01-01

An open-walled ionization chamber is developed to monitor the tritium concentration in gloveboxes in tritium processing systems. Two open walls are used to replace the sealed wall in common ionization chambers, through which the tritium gas can diffuse into the chamber without the aid of pumps and pipelines. Some basic properties of the chamber are examined to evaluate its performance. Results turn out that an open-walled chamber of 1 l in volume shows a considerably flat plateau over 700 V for a range of tritium concentration. The chamber also gives a good linear response to gamma fields over 4 decades under a pressure condition of 1 atm. The pressure dependence characteristics show that the ionization current is only sensitive at low pressures. The pressure influence becomes weaker as the pressure increases mainly due to the decrease in the mean free path of β particles produced by tritium decay. The minimum detection limit of the chamber is 3.7x10 5 Bq/m 3 .

The effect of thickness in the through-diffusion experiment

International Nuclear Information System (INIS)

Lehikoinen, J.; Uusheimo, K.; Valkiainen, M.

1994-01-01

The publication contains an experimental study of diffusion in the water filled pores of rock samples. The samples studied are rapakivi granite from Loviisa, southern Finland. The drill-core sample was sectioned perpendicularly with diamond saw and three cylinder formed samples were obtained. The nominal thicknesses (heights of the cylinders) are 2, 4 and 6 cm. For the diffusion measurement the sample holders were pressed between two chambers. One of the chambers was filled with 0.0044 molar sodium chloride solution spiked with tracers. Another chamber was filled with inactive solution. Tritium (HTO) considered to be water equivalent tracer and anionic 36 Cl were used as tracers. (9 refs., 19 figs., 2 tabs.)

The molecular chemistry of diffuse and translucent clouds in the line-of-sight to Sgr B2: Absorption by simple organic and inorganic molecules in the GBT PRIMOS survey

Science.gov (United States)

Corby, J. F.; McGuire, B. A.; Herbst, E.; Remijan, A. J.

2018-02-01

The 1-50 GHz PRebiotic Interstellar MOlecular Survey (PRIMOS) contains 50 molecular absorption lines observed in clouds located in the line-of-sight to Sgr B2(N). The line-of-sight material is associated with diffuse and translucent clouds located in the Galactic center, bar, and spiral arms in the disk. We measured the column densities and estimate abundances, relative to H2, of 11 molecules and additional isotopologues observed in this material. We used absorption by optically thin transitions of c-C3H2 to estimate the molecular hydrogen columns, and argue that this method is preferable to more commonly used methods. We discuss the kinematic structure and abundance patterns of small molecules including the sulfur-bearing species CS, SO, CCS, H2CS, and HCS+; oxygen-bearing molecules OH, SiO, and H2CO; and simple hydrocarbon molecules c-C3H2, l-C3H, and l-C3H+. Finally, we discuss the implications of the observed chemistry for the structure of the gas and dust in the ISM. Highlighted results include the following. First, whereas gas in the disk has a molecular hydrogen fraction of 0.65, clouds on the outer edge of the Galactic bar and in or near the Galactic center have molecular fractions of 0.85 and >0.9, respectively. Second, we observe trends in isotope ratios with Galactocentric distance; while carbon and silicon show enhancement of the rare isotopes at low Galactocentric distances, sulfur exhibits no trend with Galactocentric distance. We also determine that the ratio of c-C3H2/c-H13CCCH provides a good estimate of the 12C/13C ratio, whereas H2CO/H213CO exhibits fractionation. Third, we report the presence of l-C3H+ in diffuse clouds for the first time. Finally, we suggest that CS has an enhanced abundance within higher density clumps of material in the disk, and therefore may be diagnostic of cloud conditions. If this holds, the diffuse clouds in the Galactic disk contain multiple embedded hyperdensities in a clumpy structure, and the density profile is not

Dark matter limits froma 15 kg windowless bubble chamber

Energy Technology Data Exchange (ETDEWEB)

Szydagis, Matthew Mark [Univ. of Chicago, IL (United States)

2011-03-01

The COUPP collaboration has successfully used bubble chambers, a technology previously applied only to high-energy physics experiments, as direct dark matter detectors. It has produced the world's most stringent spin-dependent WIMP limits, and increasingly competitive spin-independent limits. These limits were achieved by capitalizing on an intrinsic rejection of the gamma background that all other direct detection experiments must address through high-density shielding and empirically-determined data cuts. The history of COUPP, including its earliest prototypes and latest results, is briefly discussed in this thesis. The feasibility of a new, windowless bubble chamber concept simpler and more inexpensive in design is discussed here as well. The dark matter limits achieved with a 15 kg windowless chamber, larger than any previous COUPP chamber (2 kg, 4 kg), are presented. Evidence of the greater radiopurity of synthetic quartz compared to natural is presented using the data from this 15 kg device, the first chamber to be made from synthetic quartz. The effective reconstruction of the three-dimensional positions of bubbles in a highly distorted optical field, with ninety-degree bottom lighting similar to cloud chamber lighting, is demonstrated. Another innovation described in this thesis is the use of the sound produced by bubbles recorded by an array of piezoelectric sensors as the primary means of bubble detection. In other COUPP chambers, cameras have been used as the primary trigger. Previous work on bubble acoustic signature differentiation using piezos is built upon in order to further demonstrate the ability to discriminate between alpha- and neutron-induced events.

Culture of normal human blood cells in a diffusion chamber system II. Lymphocyte and plasma cell kinetics

International Nuclear Information System (INIS)

Chikkappa, G.; Carsten, A.L.; Chanana, A.D.; Cronkite, E.P.

1979-01-01

Normal human blood leukocytes were cultured in Millipore diffusion chambers implanted into the peritoneal cavities of irradiated mice. The evaluation of survival and proliferation kinetics of cells in lymphyocytic series suggested that the lymphoid cells are formed from transition of small and/or large lymphocytes, and the lymphoblasts from the lymphoid cells. There was also evidence indicating that some of the cells in these two compartments are formed by proliferation. The evaluation of plasmacytic series suggested that the plasma cells are formed from plasmacytoid-lymphocytes by transition, and the latter from the transition of lymphocytes. In addition, relatively a small fraction of cells in these two compartments are formed by proliferation. mature plasma cells do not and immature plasma cells do proliferate. Estimation of magnitude of plasma cells formed in the cultures at day 18 indicated that at least one plasma cell is formed for every 6 normal human blood lymphocytes introduced into the culture

Electron-cloud build-up in hadron machines

International Nuclear Information System (INIS)

Furman, M.A.

2004-01-01

The first observations of electron-proton coupling effect for coasting beams and for long-bunch beams were made at the earliest proton storage rings at the Budker Institute of Nuclear Physics (BINP) in the mid-60's [1]. The effect was mainly a form of the two-stream instability. This phenomenon reappeared at the CERN ISR in the early 70's, where it was accompanied by an intense vacuum pressure rise. When the ISR was operated in bunched-beam mode while testing aluminum vacuum chambers, a resonant effect was observed in which the electron traversal time across the chamber was comparable to the bunch spacing [2]. This effect (''beam-induced multipacting''), being resonant in nature, is a dramatic manifestation of an electron cloud sharing the vacuum chamber with a positively-charged beam. An electron-cloud-induced instability has been observed since the mid-80's at the PSR (LANL) [3]; in this case, there is a strong transverse instability accompanied by fast beam losses when the beam current exceeds a certain threshold. The effect was observed for the first time for a positron beam in the early 90's at the Photon Factory (PF) at KEK, where the most prominent manifestation was a coupled-bunch instability that was absent when the machine was operated with an electron beam under otherwise identical conditions [4]. Since then, with the advent of ever more intense positron and hadron beams, and the development and deployment of specialized electron detectors [5-9], the effect has been observed directly or indirectly, and sometimes studied systematically, at most lepton and hadron machines when operated with sufficiently intense beams. The effect is expected in various forms and to various degrees in accelerators under design or construction. The electron-cloud effect (ECE) has been the subject of various meetings [10-15]. Two excellent reviews, covering the phenomenology, measurements, simulations and historical development, have been recently given by Frank Zimmermann [16

CHEMICAL ANALYSIS OF A DIFFUSE CLOUD ALONG A LINE OF SIGHT TOWARD W51: MOLECULAR FRACTION AND COSMIC-RAY IONIZATION RATE

Energy Technology Data Exchange (ETDEWEB)

Indriolo, Nick; Neufeld, D. A. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Gerin, M. [LERMA, CNRS, Observatoire de Paris and ENS, F-75231 Paris Cedex 05 (France); Geballe, T. R. [Gemini Observatory, Hilo, HI 96720 (United States); Black, J. H. [Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE-43992 Onsala (Sweden); Menten, K. M. [MPI fuer Radioastronomie, D-53121 Bonn (Germany); Goicoechea, J. R. [Departamento de Astrofisica, Centro de Astrobiologia (CSIC-INTA), E-28850 Madrid (Spain)

2012-10-20

Absorption lines from the molecules OH{sup +}, H{sub 2}O{sup +}, and H{sup +} {sub 3} have been observed in a diffuse molecular cloud along a line of sight near W51 IRS2. We present the first chemical analysis that combines the information provided by all three of these species. Together, OH{sup +} and H{sub 2}O{sup +} are used to determine the molecular hydrogen fraction in the outskirts of the observed cloud, as well as the cosmic-ray ionization rate of atomic hydrogen. H{sup +} {sub 3} is used to infer the cosmic-ray ionization rate of H{sub 2} in the molecular interior of the cloud, which we find to be {zeta}{sub 2} = (4.8 {+-} 3.4) Multiplication-Sign 10{sup -16} s{sup -1}. Combining the results from all three species we find an efficiency factor-defined as the ratio of the formation rate of OH{sup +} to the cosmic-ray ionization rate of H-of {epsilon} = 0.07 {+-} 0.04, much lower than predicted by chemical models. This is an important step in the future use of OH{sup +} and H{sub 2}O{sup +} on their own as tracers of the cosmic-ray ionization rate.

α spectrometry grid ionization chamber: improvement of the characteristics

International Nuclear Information System (INIS)

Le Du, R.; Miltenberger, B.

1968-01-01

The rise time of the signals obtained with a grid ionization chamber depends on the orientation in the chamber and on the mobility of the ionization components. Our grid chambers are fitted with an electronic system which analyses the signals due to the electronic ionization components which are collected on the plate and on the source holder. By obtaining coincidence between these two signals, it is possible to select paths of any given orientation. Using this principle we have built an electronic collimator which does not have the disadvantages of a mechanical collimator for alpha spectra studies, and which, further, considerably reduces the background of the chamber. Simultaneously with the study of the improvement of a spectra with our device, we have been able to dissociate the contributions of back-diffusion and of self-absorption phenomena to the activity of an alpha source; some results will be presented. (authors) [fr

Cosmic ray diffusion in a violent interstellar medium

International Nuclear Information System (INIS)

Bykov, A.M.; Toptygin, I.N.

1985-01-01

A variety of the avaiable observational data on the cosmic ray (CR) spectrum, anisotropy and composition are in good agreement with a suggestion on the diffusion propagation of CR with energy below 10(15) eV in the interstellar medium. The magnitude of the CR diffusion coefficient and its energy dependence are determined by interstellar medium (ISM) magnetic field spectra. Direct observational data on magnetic field spectra are still absent. A theoretical model to the turbulence generation in the multiphase ISM is resented. The model is based on the multiple generation of secondary shocks and concomitant large-scale rarefactions due to supernova shock interactions with interstellar clouds. The distribution function for ISM shocks are derived to include supernova statistics, diffuse cloud distribution, and various shock wave propagation regimes. This permits calculation of the ISM magnetic field fluctuation spectrum and CR diffusion coefficient for the hot phase of ISM

Electron cloud observations at the ISIS Proton Synchrotron

CERN Document Server

Pertica, A.

2013-04-22

The build up of electron clouds inside a particle accelerator vacuum chamber can produce strong transverse and longitudinal beam instabilities which in turn can lead to high levels of beam loss often requiring the accelerator to be run below its design specification. To study the behaviour of electron clouds at the ISIS Proton Synchrotron, a Micro-Channel Plate (MCP) based electron cloud detector has been developed. The detector is based on the Retarding Field Analyser (RFA) design and consists of a retarding grid, which allows energy analysis of the electron signal, and a MCP assembly placed in front of the collector plate. The MCP assembly provides a current gain over the range 300 to 25K, thereby increasing the signal to noise ratio and dynamic range of the measurements. This paper presents the first electron cloud observations at the ISIS Proton Synchrotron. These results are compared against signals from a beam position monitor and a fast beam loss monitor installed at the same location.

Theory and measurement of the electron cloud effect

CERN Document Server

Harkay, K C

1999-01-01

Photoelectrons produced through the interaction of synchrotron radiation and the vacuum chamber walls can be accelerated by a charged particle beam, acquiring sufficient energy to produce secondary electrons (SEs) in collisions with the walls. If the secondary-electron yield (SEY) coefficient of the wall material is greater than one, a runaway condition can develop. In addition to the SEY, the degree of amplification depends on the beam intensity and temporal distribution. As the electron cloud builds up along a train of stored bunches, a transverse perturbation of the head bunch can be communicated to trailing bunches in a wakefield-like interaction with the cloud. The electron cloud effect is especially of concern for the high-intensity PEP-II (SLAC) and KEK B-factories and at the Large Hadron Collider (LHC) at CERN. An initiative was undertaken at the Advanced Photon Source (APS) storage ring to characterize the electron cloud in order to provide realistic limits on critical input parameters in the models ...

Automatic semi-continuous accumulation chamber for diffuse gas emissions monitoring in volcanic and non-volcanic areas

Science.gov (United States)

Lelli, Matteo; Raco, Brunella; Norelli, Francesco; Virgili, Giorgio; Continanza, Davide

2016-04-01

Since various decades the accumulation chamber method is intensively used in monitoring activities of diffuse gas emissions in volcanic areas. Although some improvements have been performed in terms of sensitivity and reproducibility of the detectors, the equipment used for measurement of gas emissions temporal variation usually requires expensive and bulky equipment. The unit described in this work is a low cost, easy to install-and-manage instrument that will make possible the creation of low-cost monitoring networks. The Non-Dispersive Infrared detector used has a concentration range of 0-5% CO2, but the substitution with other detector (range 0-5000 ppm) is possible and very easy. Power supply unit has a 12V, 7Ah battery, which is recharged by a 35W solar panel (equipped with charge regulator). The control unit contains a custom programmed CPU and the remote transmission is assured by a GPRS modem. The chamber is activated by DataLogger unit, using a linear actuator between the closed position (sampling) and closed position (idle). A probe for the measure of soil temperature, soil electrical conductivity, soil volumetric water content, air pressure and air temperature is assembled on the device, which is already arranged for the connection of others external sensors, including an automatic weather station. The automatic station has been tested on the field at Lipari island (Sicily, Italy) during a period of three months, performing CO2 flux measurement (and also weather parameters), each 1 hour. The possibility to measure in semi-continuous mode, and at the same time, the gas fluxes from soil and many external parameters, helps the time series analysis aimed to the identification of gas flux anomalies due to variations in deep system (e.g. onset of volcanic crises) from those triggered by external conditions.

Transport and trapping of dust particles in a potential well created by inductively coupled diffused plasmas.

Science.gov (United States)

Choudhary, Mangilal; Mukherjee, S; Bandyopadhyay, P

2016-05-01

A versatile linear dusty (complex) plasma device is designed to study the transport and dynamical behavior of dust particles in a large volume. Diffused inductively coupled plasma is generated in the background of argon gas. A novel technique is used to introduce the dust particles in the main plasma by striking a secondary direct current glow discharge. These dust particles are found to get trapped in an electrostatic potential well, which is formed due to the combination of the ambipolar electric field caused by diffusive plasma and the field produced by the charged glass wall of the vacuum chamber. According to the requirements, the volume of the dust cloud can be controlled very precisely by tuning the plasma and discharge parameters. The present device can be used to address the underlying physics behind the transport of dust particles, self-excited dust acoustic waves, and instabilities. The detailed design of this device, plasma production and characterization, trapping and transport of the dust particle, and some of the preliminary experimental results are presented.

Theoretical calculation on CR-39 response for radon measurements and optimum diffusion chambers dimensions

Energy Technology Data Exchange (ETDEWEB)

Askari, H.R.; Ghandi, Kh. [Department of Physics, Faculty of Science, Vali-e-Asr University, Rafsanjan 7713936417 (Iran, Islamic Republic of); Rahimi, M. [Department of Physics, Faculty of Science, Vali-e-Asr University, Rafsanjan 7713936417 (Iran, Islamic Republic of)], E-mail: rahimi_bam@yahoo.com; Negarestani, A. [International Center for Science and High Technology and Environmental Sciences, Kerman (Iran, Islamic Republic of)

2008-11-11

One method to measure radon gas concentration in the air with a long time of radiation is trace chemical etching technique. There is a direct proportion between the number of traces on solid-state nuclear track detectors (SSNTDs) and activity concentration of radon. In this paper, calibration constant for a cylindrical chamber with CR-39 detector has been measured analytically. Using this measurement, trace curves on the base of concentration for chambers with different heights and radii have been drawn. The results show that to measure radon gas concentration, the optimum chamber should have a height between 3.5 and 4 cm and a radius between 2.5 and 3.2 cm.

Theoretical calculation on CR-39 response for radon measurements and optimum diffusion chambers dimensions

International Nuclear Information System (INIS)

Askari, H.R.; Ghandi, Kh.; Rahimi, M.; Negarestani, A.

2008-01-01

One method to measure radon gas concentration in the air with a long time of radiation is trace chemical etching technique. There is a direct proportion between the number of traces on solid-state nuclear track detectors (SSNTDs) and activity concentration of radon. In this paper, calibration constant for a cylindrical chamber with CR-39 detector has been measured analytically. Using this measurement, trace curves on the base of concentration for chambers with different heights and radii have been drawn. The results show that to measure radon gas concentration, the optimum chamber should have a height between 3.5 and 4 cm and a radius between 2.5 and 3.2 cm.

Single Particle Laser Mass Spectrometry Applied to Differential Ice Nucleation Experiments at the AIDA Chamber

International Nuclear Information System (INIS)

Gallavardin, S. J.; Froyd, Karl D.; Lohmann, U.; Moehler, Ottmar; Murphy, Daniel M.; Cziczo, Dan

2008-01-01

Experiments conducted at the Aerosol Interactions and Dynamics in the Atmosphere (AIDA) chamber located in Karlsruhe, Germany permit investigation of particle properties that affect the nucleation of ice at temperature and water vapor conditions relevant to cloud microphysics and climate issues. Ice clouds were generated by heterogeneous nucleation of Arizona test dust (ATD), illite, and hematite and homogeneous nucleation of sulfuric acid. Ice crystals formed in the chamber were inertially separated from unactivated, or 'interstitial' aerosol particles with a pumped counterflow virtual impactor (PCVI), then evaporated. The ice residue (i.e., the aerosol which initiated ice nucleation plus any material which was scavenged from the gas- and/or particle-phase), was chemically characterized at the single particle level using a laser ionization mass spectrometer. In this manner the species that first nucleated ice could be identified out of a mixed aerosol population in the chamber. Bare mineral dust particles were more effective ice nuclei (IN) than similar particles with a coating. Metallic particles from contamination in the chamber initiated ice nucleation before other species but there were few enough that they did not compromise the experiments. Nitrate, sulfate, and organics were often detected on particles and ice residue, evidently from scavenging of trace gas-phase species in the chamber. Hematite was a more effective ice nucleus than illite. Ice residue was frequently larger than unactivated test aerosol due to the formation of aggregates due to scavenging, condensation of contaminant gases, and the predominance of larger aerosol in nucleation

Interaction of clouds with the hot interstellar medium (HIM) and cosmic rays

International Nuclear Information System (INIS)

Voelk, H.J.

1983-01-01

The modification, by cosmic rays, of the interaction of interstellar clouds with the ambient HIM is considered. Small clouds should still evaporate and thereby exclude cosmic rays if they do so without cosmic rays. The possible mass accretion of massice clouds is reduced by the pressure of the compressed cosmic rays. The consequences for diffuse galactic #betta#-ray emisison are discussed. (orig.)

Investigation of long drift chambers for a nucleon-decay detector

International Nuclear Information System (INIS)

Price, L.E.; Dawson, J.; Ayres, D.; Denis, R.S.

1981-01-01

The use of long drift chambers for a nucleon-decay detector is discussed as a means of achieving a detector with very fine tracking, but with a modest number of readout channels. Strategies for reducing the attenuation of drifting electrons are considered, particularly the necessity of shaping the electric field to reduce the effects of diffusion and of nearby grounded conductors. Measured results are presented for a chamber with 1 cm drift gap and 50 cm maximum drift distance. The measured attenuation is 12%

Improved Cloud Condensation Nucleus Spectrometer

Science.gov (United States)

Leu, Ming-Taun

2010-01-01

An improved thermal-gradient cloud condensation nucleus spectrometer (CCNS) has been designed to provide several enhancements over prior thermal- gradient counters, including fast response and high-sensitivity detection covering a wide range of supersaturations. CCNSs are used in laboratory research on the relationships among aerosols, supersaturation of air, and the formation of clouds. The operational characteristics of prior counters are such that it takes long times to determine aerosol critical supersaturations. Hence, there is a need for a CCNS capable of rapid scanning through a wide range of supersaturations. The present improved CCNS satisfies this need. The improved thermal-gradient CCNS (see Figure 1) incorporates the following notable features: a) The main chamber is bounded on the top and bottom by parallel thick copper plates, which are joined by a thermally conductive vertical wall on one side and a thermally nonconductive wall on the opposite side. b) To establish a temperature gradient needed to establish a supersaturation gradient, water at two different regulated temperatures is pumped through tubes along the edges of the copper plates at the thermally-nonconductive-wall side. Figure 2 presents an example of temperature and supersaturation gradients for one combination of regulated temperatures at the thermally-nonconductive-wall edges of the copper plates. c) To enable measurement of the temperature gradient, ten thermocouples are cemented to the external surfaces of the copper plates (five on the top plate and five on the bottom plate), spaced at equal intervals along the width axis of the main chamber near the outlet end. d) Pieces of filter paper or cotton felt are cemented onto the interior surfaces of the copper plates and, prior to each experimental run, are saturated with water to establish a supersaturation field inside the main chamber. e) A flow of monodisperse aerosol and a dilution flow of humid air are introduced into the main

Dark matter limits from a 15 kg windowless bubble chamber

International Nuclear Information System (INIS)

Szydagis, Matthew Mark

2010-01-01

The COUPP collaboration has successfully used bubble chambers, a technology previously applied only to high-energy physics experiments, as direct dark matter detectors. It has produced the world's most stringent spin-dependent WIMP limits, and increasingly competitive spin-independent limits. These limits were achieved by capitalizing on an intrinsic rejection of the gamma background that all other direct detection experiments must address through high-density shielding and empirically-determined data cuts. The history of COUPP, including its earliest prototypes and latest results, is briefly discussed in this thesis. The feasibility of a new, windowless bubble chamber concept simpler and more inexpensive in design is discussed here as well. The dark matter limits achieved with a 15 kg windowless chamber, larger than any previous COUPP chamber (2 kg, 4 kg), are presented. Evidence of the greater radiopurity of synthetic quartz compared to natural is presented using the data from this 15 kg device, the first chamber to be made from synthetic quartz. The effective reconstruction of the three-dimensional positions of bubbles in a highly distorted optical field, with ninety-degree bottom lighting similar to cloud chamber lighting, is demonstrated. Another innovation described in this thesis is the use of the sound produced by bubbles recorded by an array of piezoelectric sensors as the primary means of bubble detection. In other COUPP chambers, cameras have been used as the primary trigger. Previous work on bubble acoustic signature differentiation using piezos is built upon in order to further demonstrate the ability to discriminate between alpha- and neutron-induced events.

Some basic mathematical methods of diffusion theory. [emphasis on atmospheric applications

Science.gov (United States)

Giere, A. C.

1977-01-01

An introductory treatment of the fundamentals of diffusion theory is presented, starting with molecular diffusion and leading up to the statistical methods of turbulent diffusion. A multilayer diffusion model, designed to permit concentration and dosage calculations downwind of toxic clouds from rocket vehicles, is described. The concepts and equations of diffusion are developed on an elementary level, with emphasis on atmospheric applications.

Cloud regimes as phase transitions

Science.gov (United States)

Stechmann, Samuel; Hottovy, Scott

2017-11-01

Clouds are repeatedly identified as a leading source of uncertainty in future climate predictions. Of particular importance are stratocumulus clouds, which can appear as either (i) closed cells that reflect solar radiation back to space or (ii) open cells that allow solar radiation to reach the Earth's surface. Here we show that these clouds regimes - open versus closed cells - fit the paradigm of a phase transition. In addition, this paradigm characterizes pockets of open cells (POCs) as the interface between the open- and closed-cell regimes, and it identifies shallow cumulus clouds as a regime of higher variability. This behavior can be understood using an idealized model for the dynamics of atmospheric water as a stochastic diffusion process. Similar viewpoints of deep convection and self-organized criticality will also be discussed. With these new conceptual viewpoints, ideas from statistical mechanics could potentially be used for understanding uncertainties related to clouds in the climate system and climate predictions. The research of S.N.S. is partially supported by a Sloan Research Fellowship, ONR Young Investigator Award N00014-12-1-0744, and ONR MURI Grant N00014-12-1-0912.

Preliminary laboratory studies of the optical scattering properties of the crystal clouds

Directory of Open Access Journals (Sweden)

C. Saunders

Full Text Available Ice crystal clouds have an influence on the radiative budget of the earth; however, the exact size and nature of this influence has yet to be determined. A laboratory cloud chamber experiment has been set up to provide data on the optical scattering behaviour of ice crystals at a visible wavelength in order to gain information which can be used in climate models concerning the radiative characteristics of cirrus clouds. A PMS grey-scale probe is used to monitor simultaneously the cloud microphysical properties in order to correlate these closely with the observed radiative properties. Preliminary results show that ice crystals scatter considerably more at 90° than do water droplets, and that the halo effects are visible in a laboratory-generated cloud when the ice crystal concentration is sufficiently small to prevent masking from multiple scattering.

Key words. Meteorology and atmosphere dynamics · Climatology · Radiative process · Atmospheric composition and structure · Cloud physics and chemistry

Mechanisms of differentiation in the Skaergaard magma chamber

Science.gov (United States)

Tegner, C.; Lesher, C. E.; Holness, M. B.; Jakobsen, J. K.; Salmonsen, L. P.; Humphreys, M. C. S.; Thy, P.

2012-04-01

The Skaergaard intrusion is a superb natural laboratory for studying mechanisms of magma chamber differentiation. The magnificent exposures and new systematic sample sets of rocks that solidified inwards from the roof, walls and floor of the chamber provide means to test the relative roles of crystal settling, diffusion, convection, liquid immiscibility and compaction in different regions of the chamber and in opposite positions relative to gravity. Examination of the melt inclusions and interstitial pockets has demonstrated that a large portion of intrusion crystallized from an emulsified magma chamber composed of immiscible silica- and iron-rich melts. The similarity of ratios of elements with opposite partitioning between the immiscible melts (e.g. P and Rb) in wall, floor and roof rocks, however, indicate that large-scale separation did not occur. Yet, on a smaller scale of metres to hundred of metres and close to the interface between the roof and floor rocks (the Sandwich Horizon), irregular layers and pods of granophyre hosted by extremely iron-rich cumulates point to some separation of the two liquid phases. Similar proportions of the primocryst (cumulus) minerals in roof, wall and floor rocks indicate that crystal settling was not an important mechanism. Likewise, the lack of fractionation of elements with different behavior indicate that diffusion and fluid-driven metasomatism played relatively minor roles. Compositional convection and/or compaction within the solidifying crystal mush boundary layer are likely the most important mechanisms. A correlation of low trapped liquid fractions (calculated from strongly incompatible elements) in floor rocks with high fractionation density (the density difference between the crystal framework and the liquid) indicate that compaction is the dominating process in expelling evolved liquid from the crystal mush layer. This is supported by high and variable trapped liquid contents in the roof rocks, where gravity

Cloud-turbulence interactions: Sensitivity of a general circulation model to closure assumptions

International Nuclear Information System (INIS)

Brinkop, S.; Roeckner, E.

1993-01-01

Several approaches to parameterize the turbulent transport of momentum, heat, water vapour and cloud water for use in a general circulation model (GCM) have been tested in one-dimensional and three-dimensional model simulations. The schemes differ with respect to their closure assumptions (conventional eddy diffusivity model versus turbulent kinetic energy closure) and also regarding their treatment of cloud-turbulence interactions. The basis properties of these parameterizations are discussed first in column simulations of a stratocumulus-topped atmospheric boundary layer (ABL) under a strong subsidence inversion during the KONTROL experiment in the North Sea. It is found that the K-models tend to decouple the cloud layer from the adjacent layers because the turbulent activity is calculated from local variables. The higher-order scheme performs better in this respect because internally generated turbulence can be transported up and down through the action of turbulent diffusion. Thus, the TKE-scheme provides not only a better link between the cloud and the sub-cloud layer but also between the cloud and the inversion as a result of cloud-top entrainment. In the stratocumulus case study, where the cloud is confined by a pronounced subsidence inversion, increased entrainment favours cloud dilution through enhanced evaporation of cloud droplets. In the GCM study, however, additional cloud-top entrainment supports cloud formation because indirect cloud generating processes are promoted through efficient ventilation of the ABL, such as the enhanced moisture supply by surface evaporation and the increased depth of the ABL. As a result, tropical convection is more vigorous, the hydrological cycle is intensified, the whole troposphere becomes warmer and moister in general and the cloudiness in the upper part of the ABL is increased. (orig.)

HINS R and D Collaboration on Electron Cloud Effects: Midyear Report

International Nuclear Information System (INIS)

Furman, M.A.; Sonnad, K.; Vay, J.-L.

2006-01-01

We present a report on ongoing activities on electron-cloud R and D for the MI upgrade. These results update and extend those presented in Refs. 1, 2. In this report we have significantly expanded the parameter range explored in bunch intensity Nb, RMS bunch length σ z and peak secondary emission yield (SEY) (delta) max , but we have constrained our simulations to a field-free region. We describe the threshold behaviors in all of the above three parameters. For (delta) max (ge) 1.5 we find that, even for N b = 1 x 10 11 , the electron cloud density, when averaged over the entire chamber, exceeds the beam neutralization level, but remains significantly below the local neutralization level (ie., when the electron density is computed in the neighborhood of the beam). This 'excess' of electrons is accounted for by narrow regions of high concentration of electrons very close to the chamber surface, especially at the top and bottom of the chamber, akin to virtual cathodes. These virtual cathodes are kept in equilibrium, on average, by a competition between space-charge forces (including their images) and secondary emission, a mechanism that shares some features with the space-charge saturation of the current in a diode at high fields. For N b = 3 x 10 11 the electron cloud build-up growth rate and saturation density have a strong dependence on σ z as σ z decreases below ∼ 0.4 m, when the average electron-wall impact energy roughly reaches the energy E max where (delta) peaks. We also present improved results on emittance growth simulations of the beam obtained with the code WARP/POSINST in quasi-static mode, in which the beam-(electron cloud) interaction is lumped into N s 'stations' around the ring, where N s = 1, 2,..., 9. The emittance shows a rapid growth of ∼ 20% during the first ∼ 100 turns, followed by a much slower growth rate of ∼ 0.03%/turn. Concerning the electron cloud detection technique using microwave transmission, we present an improved

Carbon Chemistry in Transitional Clouds from the GOT C+ Survey of CII 158 micron Emission in the Galactic Plane

Science.gov (United States)

Langer, W. D.; Velusamy, T.; Pineda, J.; Willacy, K.; Goldsmith, P. F.

2011-05-01

In understanding the lifecycle and chemistry of the interstellar gas, the transition from diffuse atomic to molecular gas clouds is a very important stage. The evolution of carbon from C+ to C0 and CO is a fundamental part of this transition, and C+ along with its carbon chemistry is a key diagnostic. Until now our knowledge of interstellar gas has been limited primarily to the diffuse atomic phase traced by HI and the dense molecular H2 phase traced by CO. However, we have generally been missing an important layer in diffuse and transition clouds, which is denoted by the warm "dark gas'', that is mostly H2 and little HI and CO, and is best traced with C+. Here, we discuss the chemistry in the transition from C+ to C0 and CO in these clouds as understood by a survey of the CII 1.9 THz (158 micron) line from a sparse survey of the inner galaxy over about 40 degrees in longitude as part of the Galactic Observations of Terahertz C+ (GOT C+) program, a Herschel Space Observatory Open Time Key Program to study interstellar clouds by sampling ionized carbon. Using the first results from GOT C+ along 11 LOSs, in a sample of 53 transition clouds, Velusamy, Langer et al. (A&A 521, L18, 2010) detected an excess of CII intensities indicative of a thick H2 layer (a significant warm H2, "dark gas'' component) around the 12CO core. Here we present a much larger, statistically significant sample of a few hundred diffuse and transition clouds traced by CII, along with auxiliary HI and CO data in the inner Galaxy between l=-30° and +30°. Our new and more extensive sample of transition clouds is used to elucidate the time dependent physical and carbon chemical evolution of diffuse to transition clouds, and transition layers. We consider the C+ to CO conversion pathways such as H++ O and C+ + H2 chemistry for CO production to constrain the physical parameters such as the FUV intensity and cosmic ray ionization rate that drive the CO chemistry in the diffuse transition clouds.

Photoelectron Yield and Photon Reflectivity from Candidate LHC Vacuum Chamber Materials with Implications to the Vacuum Chamber Design

CERN Document Server

Baglin, V; Gröbner, Oswald

1998-01-01

Studies of the photoelectron yield and photon reflectivity at grazing incidence (11 mrad) from candidate LHC vacuum chamber materials have been made on a dedicated beam line on the Electron Positron A ccumulator (EPA) ring at CERN. These measurements provide realistic input toward a better understanding of the electron cloud phenomena expected in the LHC. The measurements were made using synchrotro n radiation with critical photon energies of 194 eV and 45 eV; the latter corresponding to that of the LHC at the design energy of 7 TeV. The test materials are mainly copper, either, i) coated by co- lamination or by electroplating onto stainless steel, or ii) bulk copper prepared by special machining. The key parameters explored were the effect of surface roughness on the reflectivity and the pho toelectron yield at grazing photon incidence, and the effect of magnetic field direction on the yields measured at normal photon incidence. The implications of the results on the electron cloud phenom ena, and thus the L...

Study of glow discharge positive column with cloud of disperse particles

International Nuclear Information System (INIS)

Polyakov, D.N.; Shumova, V.V.; Vasilyak, L.M.; Fortov, V.E.

2011-01-01

The study aims to describe plasma parameters changes induced by clouds of disperse micron size particles. Dust clouds were formed in the positive column of glow discharge in air at pressure 0.1-0.6 torr and current 0.1-3 mA. The simultaneous registration of discharge voltage and dust cloud parameters was carried out. Experimental results were simulated using diffusion model. The dust cloud is shown to smooth the radial electron concentration profile, increase electric field strength and electron temperature and stabilize the discharge. The cloud is demonstrated to be a trap for positive ions without increase of discharge current. -- Highlights: → 25% increase of longitudinal electric field strength in discharge with dust cloud. → The smoothing effect of dust cloud on radial electron and ion concentration profiles. → Dust cloud as a trap for positive ions without increase of discharge current. → Increase of electron temperature in discharge with dust cloud. → Increase of discharge stability in presence of dust cloud.

Interstellar clouds toward 3C 154 and 3C 353

International Nuclear Information System (INIS)

Federman, S.R.; Evans, N.J. II; Willson, R.F.; Falgarone, E.; Combes, F.; Texas Univ., Austin; Tufts Univ., Medford, MA; Meudon, Observatoire, France)

1987-01-01

Molecular observations of the interstellar clouds toward the radio sources 3C 154 and 3C 353 were obtained in order to elucidate the physical conditions within the clouds. Maps of (C-12)O emission in the J = 1-0 and J = 2-1 lines were compared with observations of the (C-13)O, CH, and OH molecules. The peak emission in the (C-12)O transitions does not occur in the direction of the continuum sources, and thus, an incomplete picture arises when only one line of sight in the two clouds is analyzed. The cloud toward 3C 154 appears to have a low extinction, but a relatively high CO abundance, suggesting that it is similar to high-latitude clouds and CO-rich diffuse clouds. The cloud toward 3C 353 is considerably denser than that toward 3C 154 and may be more like a dark cloud. 32 references

Electron-microscope study of cloud and fog nuclei

Energy Technology Data Exchange (ETDEWEB)

Ogiwara, S; Okita, T

1952-01-01

Droplets of clouds on a mountain and of fog in an urban area were captured and the form, nature and size of their nuclei were studied by means of an electron-microscope and by a chamber of constant humidity. These nuclei have similar form and nature to the hygroscopic particles in haze and to the artificially produced combustion particles. No sea-salt nuclei were found in our observations, therefore, sea-spray appears to be an insignificant source of condensation nuclei. It was found that both the cloud and the fog nuclei originated in combustion products which were the mixture of hygroscopic and non-hygroscopic substances, and that the greater part of the nuclei did not contain pure sulfuric acid.

Turbulent eddy diffusion models in exposure assessment - Determination of the eddy diffusion coefficient.

Science.gov (United States)

Shao, Yuan; Ramachandran, Sandhya; Arnold, Susan; Ramachandran, Gurumurthy

2017-03-01

The use of the turbulent eddy diffusion model and its variants in exposure assessment is limited due to the lack of knowledge regarding the isotropic eddy diffusion coefficient, D T . But some studies have suggested a possible relationship between D T and the air changes per hour (ACH) through a room. The main goal of this study was to accurately estimate D T for a range of ACH values by minimizing the difference between the concentrations measured and predicted by eddy diffusion model. We constructed an experimental chamber with a spatial concentration gradient away from the contaminant source, and conducted 27 3-hr long experiments using toluene and acetone under different air flow conditions (0.43-2.89 ACHs). An eddy diffusion model accounting for chamber boundary, general ventilation, and advection was developed. A mathematical expression for the slope based on the geometrical parameters of the ventilation system was also derived. There is a strong linear relationship between D T and ACH, providing a surrogate parameter for estimating D T in real-life settings. For the first time, a mathematical expression for the relationship between D T and ACH has been derived that also corrects for non-ideal conditions, and the calculated value of the slope between these two parameters is very close to the experimentally determined value. The values of D T obtained from the experiments are generally consistent with values reported in the literature. They are also independent of averaging time of measurements, allowing for comparison of values obtained from different measurement settings. These findings make the use of turbulent eddy diffusion models for exposure assessment in workplace/indoor environments more practical.

Diffuse solar radiation estimation models for Turkey's big cities

International Nuclear Information System (INIS)

Ulgen, Koray; Hepbasli, Arif

2009-01-01

A reasonably accurate knowledge of the availability of the solar resource at any place is required by solar engineers, architects, agriculturists, and hydrologists in many applications of solar energy such as solar furnaces, concentrating collectors, and interior illumination of buildings. For this purpose, in the past, various empirical models (or correlations) have been developed in order to estimate the solar radiation around the world. This study deals with diffuse solar radiation estimation models along with statistical test methods used to statistically evaluate their performance. Models used to predict monthly average daily values of diffuse solar radiation are classified in four groups as follows: (i) From the diffuse fraction or cloudness index, function of the clearness index, (ii) From the diffuse fraction or cloudness index, function of the relative sunshine duration or sunshine fraction, (iii) From the diffuse coefficient, function of the clearness index, and (iv) From the diffuse coefficient, function of the relative sunshine duration or sunshine fraction. Empirical correlations are also developed to establish a relationship between the monthly average daily diffuse fraction or cloudness index (K d ) and monthly average daily diffuse coefficient (K dd ) with the monthly average daily clearness index (K T ) and monthly average daily sunshine fraction (S/S o ) for the three big cities by population in Turkey (Istanbul, Ankara and Izmir). Although the global solar radiation on a horizontal surface and sunshine duration has been measured by the Turkish State Meteorological Service (STMS) over all country since 1964, the diffuse solar radiation has not been measured. The eight new models for estimating the monthly average daily diffuse solar radiation on a horizontal surface in three big cites are validated, and thus, the most accurate model is selected for guiding future projects. The new models are then compared with the 32 models available in the

The effect of thickness in the through-diffusion experiment. Final report

International Nuclear Information System (INIS)

Valkiainen, M.; Aalto, H.; Lehikoinen, J.; Uusheimo, K.

1996-01-01

The report contains an experimental study of diffusion in the water-filled pores of rock samples. The samples studied are rapakivi granite from Loviisa, southern Finland. The drill-core sample was sectioned perpendicularly with a diamond saw and three cylindrical samples were obtained. The nominal thicknesses (heights of the cylinders) are 2, 4 and 6 cm. For the diffusion measurement the sample holders were pressed between two chambers. One of the chambers was filled with 0.0044 molar sodium chloride solution spiked with tracers. Another chamber was filled with inactive solution. Tritium (HTO) considered to be a water equivalent tracer and anionic 36 Cl - were used as tracers. The through diffusion was monitored about 1000 days after which time the diffusion cells were emptied and the sample holders dismantled. The samples were sectioned into 1 cm slices and the tracers were leached from the slices. The porosities of the slices were determined by the weighing method. The rock-capacity factors could be determined from the leaching results obtained. It was seen that the porosity values were in accordance with the rock capacity factors obtained with HTO. An anion exclusion can be seen comparing the results obtained with HTO and 36 Cl - . The concentration profile through even the thickest sample had reached a constant slope and the rate of diffusion was practically at a steady state. An anion exclusion effect was also seen in the effective diffusion coefficients. The effect of thickness on diffusion shows that the connectivity of the pores decreases in the thickness range 2-4 cm studied. The decrease as reflected in the diffusion coefficient was not dramatic and it can be said that especially for studying chemical interactions during diffusion, the thickness of 2 cm is adequate. (orig.) (12 refs.)

Tracking the debris cloud from a Chinese nuclear test

International Nuclear Information System (INIS)

Peterson, K.R.

1977-01-01

As the radioactive debris cloud from a Chinese nuclear test on September 26, 1976 began drifting eastward, the Laboratory's computational facilities were pressed into service to predict the possible environmental effects. ERDA asked us to calculate cloud trajectories and to estimate the fallout dose. The FAA asked us to provide dose estimates both for commercial aircraft flights within the U.S. and for transatlantic flights of the Concorde SST. Our dose estimates, calculated with 2BPUFF, a large-cloud diffusion code, proved to be accurate predictions, correlating well with later observations. At FAA and ERDA request, we also worked with EG and G to measure cabin dose rates in some transatlantic SST and subsonic flights while the debris cloud moved out over the Atlantic Ocean

GOT C+ Survey of Transition Clouds in the Inner Galaxy

Science.gov (United States)

Velusamy, Thangasamy; Langer, W. D.; Pineda, J. L.; Goldsmith, P. F.; Li, D.; Yorke, H. W.

2010-05-01

To understand star formation and the lifecycle of the interstellar gas we need detailed information about the transition of diffuse atomic to molecular clouds. The C+ line at 1.9 THz traces a so-far poorly studied stage in cloud evolution - the transitional clouds going from atomic HI to molecular H2 The transition cloud phase, which is difficult to observe in HI and CO alone, may be best characterized via CII emission or absorption. Here we present the first results on transition clouds along a few representative lines of sight in the inner Galaxy from longitude 325 degrees to 10 degrees, observed under the GOT C+ program, a HIFI Herschel Key Project to study the diffuse ISM. We can separate out the different ISM components along each line of sight by comparisons of the high spectral resolution ( 1 km/s) and high sensitivity (rms 0.1 K to 0.2 K) HIFI data on C+ with HI, 12CO, and 13CO spectra. These observations are being carried out with the Herschel Space Observatory. This research was conducted at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration. JLP is supported under the NASA Postdoctoral Program at JPL, Caltech, administered by Oak Ridge Associated Universities through a contract with NASA.

A simple dynamic rising nuclear cloud based model of ground radioactive fallout for atmospheric nuclear explosion

International Nuclear Information System (INIS)

Zheng Yi

2008-01-01

A simple dynamic rising nuclear cloud based model for atmospheric nuclear explosion radioactive prediction was presented. The deposition of particles and initial cloud radius changing with time before the cloud stabilization was considered. Large-scale relative diffusion theory was used after cloud stabilization. The model was considered reasonable and dependable in comparison with four U.S. nuclear test cases and DELFIC model results. (authors)

Application of a sawtooth surface to accelerator beam chambers with low electron emission rate

International Nuclear Information System (INIS)

Suetsugu, Y.; Tsuchiya, M.; Nishidono, T.; Kato, N.; Satoh, N.; Endo, S.; Yokoyama, T.

2003-01-01

One of the latest problems in positron or proton accelerators is a single-beam instability due to an electron cloud around the beam. The instability, for an example, causes a beam size blow up of the positron beam and deteriorates the performance of the electron-positron collider. the seed of the electron cloud is the electrons emitted from the surface of the beam chamber, which consists of electrons due to the synchrotron radiation (photoelectrons) and sometimes those multiplied by the multipactoring. Suppressing the electron emission from the surface is, therefore, an essential way to cure the instability. Here a rough surface with a sawtooth structure (sawtooth surface) is proposed to reduce the electron emission from the surface of the beam chamber. A new rolling-tap method is developed for this study to make the sawtooth surface in a circular beam chamber with a length of several meters. The first experiment using a test chamber at a photon beam line of the KEK Photon Factory verifies its validity. The photoelectron emission from the sawtooth surface reduces by one order of magnitude compared to the usual smooth surface. In the second experiment under a bunched positron beam in the KEK B-Factory, however, the electron emission is comparable to that of a smooth surface and the behavior is quite different from the previous one. The reason is that the beam field excites the multipactoring of electrons and the decrease of the photoelectron emission by the sawtooth surface is wiped out. The sawtooth surface will be effective to reduce the electron emission under the situation with external magnetic fields or without strong beam fields where the electron multipactoring hardly occurs

Design and testing of a chamber device to measure organic vapor fluxes from the unsaturated zone under natural conditions

International Nuclear Information System (INIS)

Tillman, F.D.; Choi, J-W.; Smith, J.A.

2002-01-01

As the difficulty and expense of achieving water quality standards at contaminated sites becomes more apparent, the U.S. Environmental Protection Agency is taking a closer look at natural attenuation processes for selected sites. To determine if a site has potential for natural attenuation, all natural processes affecting the fate and transport of volatile organic compounds (VOCs) in the subsurface must be identified and quantified. This research addresses the quantification of air-phase VOCs leaving the subsurface and entering the atmosphere, both through diffusion and soil-gas advection caused by barometric pumping. A simple, easy-to-use, and inexpensive device for measuring VOC flux under natural conditions was designed, constructed and tested both in a controlled laboratory environment and in a natural field setting. Design parameters for the chamber were selected using continuously stirred tank reactor (CSTR)-equation based modeling under several flux inputs. The final chamber design performs at greater than 95% efficiency for the simulated cases. Laboratory testing of the flux chamber under both diffusion and advection transport conditions was performed in a device constructed to simulate the unsaturated zone. Results indicate an average flux measurement accuracy of 83% over 3 orders of magnitude for diffusion-only fluxes and 94% for combined advection-diffusion fluxes. A field test of the chamber was performed and results compared with predictions made by a 1-dimensional unsaturated zone flow and transport model whose calibration and parameters were obtained from data collected at the site. Fluxes measured directly by the chamber were generally in good agreement with the fluxes calculated from the calibrated flow-and-transport model. (author)

Computer program for the sensitivity calculation of a CR-39 detector in a diffusion chamber for radon measurements

Energy Technology Data Exchange (ETDEWEB)

Nikezic, D., E-mail: nikezic@kg.ac.rs; Stajic, J. M. [Faculty of Science, University of Kragujevac, R. Domanovica 12, Kragujevac 34000 (Serbia); Yu, K. N. [Department of Physics and Materials Science, City University of Hong Kong, 83 Tat Chee Avenue (Hong Kong)

2014-02-15

Computer software for calculation of the sensitivity of a CR-39 detector closed in a diffusion chamber to radon is described in this work. The software consists of two programs, both written in the standard Fortran 90 programming language. The physical background and a numerical example are given. Presented software is intended for numerous researches in radon measurement community. Previously published computer programs TRACK-TEST.F90 and TRACK-VISION.F90 [D. Nikezic and K. N. Yu, Comput. Phys. Commun. 174, 160 (2006); D. Nikezic and K. N. Yu, Comput. Phys. Commun. 178, 591 (2008)] are used here as subroutines to calculate the track parameters and to determine whether the track is visible or not, based on the incident angle, impact energy, etching conditions, gray level, and visibility criterion. The results obtained by the software, using five different V functions, were compared with the experimental data found in the literature. Application of two functions in this software reproduced experimental data very well, while other three gave lower sensitivity than experiment.

GOT C+: A Herschel Space Observatory Key Program to Study the Diffuse ISM

Science.gov (United States)

Langer, William; Velusamy, T.; Goldsmith, P. F.; Li, D.; Pineda, J.; Yorke, H.

2010-01-01

Star formation activity is regulated by pressures in the interstellar medium, which in turn depend on heating and cooling rates, modulated by the gravitational potential, and shock and turbulent pressures. To understand these processes we need information about the diffuse atomic and diffuse molecular gas cloud properties. The ionized carbon CII fine structure line at 1.9 THz is an important tracer of the atomic gas in the diffuse regions and the atomic to molecular cloud transformation. Furthermore, C+ is a major ISM coolant, the Galaxy's strongest emission line, with a total luminosity about a 1000 times that of CO J=1-0. Galactic Observations of the Terahertz C+ Line (GOT C+) is a Herschel Space Observatory Open Time Key Program to study the diffuse interstellar medium by sampling CII line emission throughout the Galactic disk. GOT C+ will obtain high spectral resolution CII using the Heterodyne Instrument for the Far Infrared (HIFI) instrument. It employees deep integrations, wide velocity coverage (350 km s-1) with 0.22 km s-1 resolution, and systematic sparse sampling of the Galactic disk together with observations of selected targets, of over 900 lines of sight. It will be a resource of the atomic gas properties, in the (a) Galactic disk, (b) Galaxy's central 300pc, (c) Galactic warp, (d) high latitude HI clouds, and (e) Photon Dominated Regions (PDRs). Along with HI, CO isotopes, and CI spectra, our C+ data will provide the astronomical community with a rich statistical database of diffuse cloud properties, for understanding the role of barometric pressure and turbulence in cloud evolution in the Galactic ISM and, by extension, other galaxies. The GOT C+ project will provide a template for future even larger-scale CII surveys. This research was conducted at the Jet Propulsion Laboratory, California Institute of Technology and is supported by a NASA grant.

A State-of-the-Art Experimental Laboratory for Cloud and Cloud-Aerosol Interaction Research

Science.gov (United States)

Fremaux, Charles M.; Bushnell, Dennis M.

2011-01-01

The state of the art for predicting climate changes due to increasing greenhouse gasses in the atmosphere with high accuracy is problematic. Confidence intervals on current long-term predictions (on the order of 100 years) are so large that the ability to make informed decisions with regard to optimum strategies for mitigating both the causes of climate change and its effects is in doubt. There is ample evidence in the literature that large sources of uncertainty in current climate models are various aerosol effects. One approach to furthering discovery as well as modeling, and verification and validation (V&V) for cloud-aerosol interactions is use of a large "cloud chamber" in a complimentary role to in-situ and remote sensing measurement approaches. Reproducing all of the complex interactions is not feasible, but it is suggested that the physics of certain key processes can be established in a laboratory setting so that relevant fluid-dynamic and cloud-aerosol phenomena can be experimentally simulated and studied in a controlled environment. This report presents a high-level argument for significantly improved laboratory capability, and is meant to serve as a starting point for stimulating discussion within the climate science and other interested communities.

Radiation aging studies of CO2 hydrocarbon mixtures for the SLD drift chamber

International Nuclear Information System (INIS)

Venuti, J.P.; Chadwick, G.B.

1988-10-01

The SLD drift chamber requires a 'slow' drifting gas and low diffusion to allow wave form digitization. CO 2 provides this but requires an admixture of a quencher to provide more gain. A test chamber with an 8 sense wire cell, such as will appear in the final chamber, was exposed to an x-ray tube while containing a variety of binary admixtures of Co 2 : 8% isobutane, 8% ethane, and 2% isopropanol. It was determined that adding small fractions of water (≤0.66%) or isopropanol (1--2%) to the Co 2 : 8% ethane, or 8% isobutane extended the useful life of the chamber so that integrated charge collections of /approximately/1 C/cm are permissible. Results and discussions are presented. 10 refs., 7 figs., 1 tab

Trapping in stochastic mechanics and applications to covers of clouds and radiation belts

International Nuclear Information System (INIS)

Albeverio, S.; Blanchard, P.; Combe, P.; Rodriguez, R.; Sirugue, M.; Sirugue-Collin, M.

1984-11-01

It is possible to assign a stochastic acceleration to conservative stochastic diffusion processes. As a basic assumption, this stochastic acceleration is set equal to the deterministic smooth component of the external force acting on the particle, whereas the influences of the remainder is modelled by a diffusion coefficient. In this paper, we shall try to see whether it can account for the observation in two cases: the cover of clouds of planets and the radiation belts in the planetary magnetic field. We describe the basic properties of Newtonian Diffusion Stochastic Processes and indicate their connection with Schroedinger-like equations. Furthermore we give a heuristic interpretation of the nodal surfaces as impenetrable barriers for Newtonian Stochastic Diffusion Processes. The possible applications to the observed average cloud covering in the planetary atmosphere are presented we discuss the radiation belts (Van Allen Belts) along the previous ideas

Diffusion of tritiated water in coastal areas

International Nuclear Information System (INIS)

Fukuda, M.; Kasai, A.; Imai, T.; Amano, H.; Yanase, N.

1980-01-01

The diffusion of tritiated water discharged by Japan Atomic Energy Research Institute at shore line has been investigated. In continuous discharge, the concentration of tritiated water in samples taken at a point downstream fluctuates largely. To reveal the cause, dye diffusion experiments were made in the coastal area. The shapes of dye cloud were photographed by a remote-control camera suspended from a captive balloon as color pictures. The movement of dye is so complex that a three-dimensional model must be employed to assess the diffusion in coastal areas

Implementation of a Novel Educational Modeling Approach for Cloud Computing

Directory of Open Access Journals (Sweden)

Sara Ouahabi

2014-12-01

Full Text Available The Cloud model is cost-effective because customers pay for their actual usage without upfront costs, and scalable because it can be used more or less depending on the customers’ needs. Due to its advantages, Cloud has been increasingly adopted in many areas, such as banking, e-commerce, retail industry, and academy. For education, cloud is used to manage the large volume of educational resources produced across many universities in the cloud. Keep interoperability between content in an inter-university Cloud is not always easy. Diffusion of pedagogical contents on the Cloud by different E-Learning institutions leads to heterogeneous content which influence the quality of teaching offered by university to teachers and learners. From this reason, comes the idea of using IMS-LD coupled with metadata in the cloud. This paper presents the implementation of our previous educational modeling by combining an application in J2EE with Reload editor that consists of modeling heterogeneous content in the cloud. The new approach that we followed focuses on keeping interoperability between Educational Cloud content for teachers and learners and facilitates the task of identification, reuse, sharing, adapting teaching and learning resources in the Cloud.

Intercomparison study and optical asphericity measurements of small ice particles in the CERN CLOUD experiment

Science.gov (United States)

Nichman, Leonid; Järvinen, Emma; Dorsey, James; Connolly, Paul; Duplissy, Jonathan; Fuchs, Claudia; Ignatius, Karoliina; Sengupta, Kamalika; Stratmann, Frank; Möhler, Ottmar; Schnaiter, Martin; Gallagher, Martin

2017-09-01

Optical probes are frequently used for the detection of microphysical cloud particle properties such as liquid and ice phase, size and morphology. These properties can eventually influence the angular light scattering properties of cirrus clouds as well as the growth and accretion mechanisms of single cloud particles. In this study we compare four commonly used optical probes to examine their response to small cloud particles of different phase and asphericity. Cloud simulation experiments were conducted at the Cosmics Leaving OUtdoor Droplets (CLOUD) chamber at European Organisation for Nuclear Research (CERN). The chamber was operated in a series of multi-step adiabatic expansions to produce growth and sublimation of ice particles at super- and subsaturated ice conditions and for initial temperatures of -30, -40 and -50 °C. The experiments were performed for ice cloud formation via homogeneous ice nucleation. We report the optical observations of small ice particles in deep convection and in situ cirrus simulations. Ice crystal asphericity deduced from measurements of spatially resolved single particle light scattering patterns by the Particle Phase Discriminator mark 2 (PPD-2K, Karlsruhe edition) were compared with Cloud and Aerosol Spectrometer with Polarisation (CASPOL) measurements and image roundness captured by the 3View Cloud Particle Imager (3V-CPI). Averaged path light scattering properties of the simulated ice clouds were measured using the Scattering Intensity Measurements for the Optical detectioN of icE (SIMONE) and single particle scattering properties were measured by the CASPOL. We show the ambiguity of several optical measurements in ice fraction determination of homogeneously frozen ice in the case where sublimating quasi-spherical ice particles are present. Moreover, most of the instruments have difficulties of producing reliable ice fraction if small aspherical ice particles are present, and all of the instruments cannot separate perfectly

Characterization of injected aluminum oxide nanoparticle clouds in an rf discharge

Science.gov (United States)

Krüger, Harald; Killer, Carsten; Schütt, Stefan; Melzer, André

2018-02-01

An experimental setup to deagglomerate and insert nanoparticles into a radio frequency discharge has been developed to confine defined aluminum oxide nanoparticles in a dusty plasma. For the confined particle clouds we have measured the spatially resolved in situ size and density distributions. Implementing the whole plasma chamber into the sample volume of an FTIR spectrometer the infrared spectrum of the confined aluminum oxide nanoparticles has been obtained. We have investigated the dependency of the absorbance of the nanoparticles in terms of plasma power, pressure and cloud shape. The particles’ infrared phonon resonance has been identified.

Prognostic cloud water in the Los Alamos general circulation model

International Nuclear Information System (INIS)

Kristjansson, J.E.; Kao, C.Y.J.

1993-01-01

Most of today's general circulation models (GCMS) have a greatly simplified treatment of condensation and clouds. Recent observational studies of the earth's radiation budget have suggested cloud-related feedback mechanisms to be of tremendous importance for the issue of global change. Thus, there has arisen an urgent need for improvements in the treatment of clouds in GCMS, especially as the clouds relate to radiation. In the present paper, we investigate the effects of introducing pregnostic cloud water into the Los Alamos GCM. The cloud water field, produced by both stratiform and convective condensation, is subject to 3-dimensional advection and vertical diffusion. The cloud water enters the radiation calculations through the long wave emissivity calculations. Results from several sensitivity simulations show that realistic cloud water and precipitation fields can be obtained with the applied method. Comparisons with observations show that the most realistic results are obtained when more sophisticated schemes for moist convection are introduced at the same time. The model's cold bias is reduced and the zonal winds become stronger, due to more realistic tropical convection

''The ambipolar diffusion time scale and the location of star formation in magnetic interstellar clouds'': Setting the record straight

International Nuclear Information System (INIS)

Mouschovias, T.C.

1984-01-01

The point of a recent (1983) paper by Scott is that a previous paper (1979) by Mouschovias has concluded ''erroneously'' that star formation takes place off center in a cloud because of the use of an ''improver'' definition of a time scale for ambipolar diffusion. No such conclusion, Scott claims, follows from a ''proper'' definition, such as the ''traditional'' one by Spitzer. (i) Scott misrepresents the reasoning that led to the conclusion in the paper which he criticized. (ii) He is also wrong: both the ''traditional'' and the ''improper'' definitions vary similarly with radius, and both can have an off-center minimum; the spatial variation of the degree of ionization is the determining factor: not the specific value of the time scale at the origin, as Scott claims

New particle formation in the sulfuric acid-dimethylamine-water system: reevaluation of CLOUD chamber measurements and comparison to an aerosol nucleation and growth model

Science.gov (United States)

Kürten, Andreas; Li, Chenxi; Bianchi, Federico; Curtius, Joachim; Dias, António; Donahue, Neil M.; Duplissy, Jonathan; Flagan, Richard C.; Hakala, Jani; Jokinen, Tuija; Kirkby, Jasper; Kulmala, Markku; Laaksonen, Ari; Lehtipalo, Katrianne; Makhmutov, Vladimir; Onnela, Antti; Rissanen, Matti P.; Simon, Mario; Sipilä, Mikko; Stozhkov, Yuri; Tröstl, Jasmin; Ye, Penglin; McMurry, Peter H.

2018-01-01

A recent CLOUD (Cosmics Leaving OUtdoor Droplets) chamber study showed that sulfuric acid and dimethylamine produce new aerosols very efficiently and yield particle formation rates that are compatible with boundary layer observations. These previously published new particle formation (NPF) rates are reanalyzed in the present study with an advanced method. The results show that the NPF rates at 1.7 nm are more than a factor of 10 faster than previously published due to earlier approximations in correcting particle measurements made at a larger detection threshold. The revised NPF rates agree almost perfectly with calculated rates from a kinetic aerosol model at different sizes (1.7 and 4.3 nm mobility diameter). In addition, modeled and measured size distributions show good agreement over a wide range of sizes (up to ca. 30 nm). Furthermore, the aerosol model is modified such that evaporation rates for some clusters can be taken into account; these evaporation rates were previously published from a flow tube study. Using this model, the findings from the present study and the flow tube experiment can be brought into good agreement for the high base-to-acid ratios (˜ 100) relevant for this study. This confirms that nucleation proceeds at rates that are compatible with collision-controlled (a.k.a. kinetically controlled) NPF for the conditions during the CLOUD7 experiment (278 K, 38 % relative humidity, sulfuric acid concentration between 1 × 106 and 3 × 107 cm-3, and dimethylamine mixing ratio of ˜ 40 pptv, i.e., 1 × 109 cm-3).

CESR Conversion Damping Ring Studies of Electron Cloud Instabilities (CESR-TA)

International Nuclear Information System (INIS)

Rubin, David L.; Palmer, Mark A.

2011-01-01

In the International Linear Collider, two linear accelerators will accelerate bunches of positrons and electrons to over a hundred billion electron volts and collide them in a central detector. In order to obtain useful collision rates, the bunches, each containing twenty billion particles, must be compressed to a cross section of a few nanometers by a few hundred nanometers. In order to prepare these ultra high density bunches, damping rings (DRs) are employed before the linear accelerators. The DRs take the high emittance bunches that are provided by the electron and positron sources and, through the process of radiation damping, squeeze them into ultra low emittance beams that are ready for the main linear accelerators. In the damping rings, a number of effects can prevent the successful preparation of the beams. In the electron ring, an effect known as the fast ion instability can lead to beam growth and, in the positron ring, the build-up of an electron cloud (EC), which interacts with the circulating bunches, can produce the same effect. EC build-up and the subsequent interaction of the cloud with the positron beam in the DR have been identified as major risks for the successful construction of a linear collider. The CESRTA research program at the Cornell Electron Storage Ring (CESR) was developed in order to study the build-up of the EC, the details of its impact on ultra low emittance beams, as well as methods to mitigate the impact of the cloud. In the DR, the EC forms when synchrotron photons radiated from the circulating beam strike the walls of the vacuum chamber, resulting in the emission of photoelectrons. These low energy electrons can be accelerated across the vacuum chamber by the electric field of the beam, and strike the walls, causing the emission of secondary electrons. The secondary electrons are subsequently accelerated into the walls yet again via the same mechanism. The result is that the EC can rapidly begin to fill the vacuum chamber. In

CESR Conversion Damping Ring Studies of Electron Cloud Instabilities (CESR-TA)

Energy Technology Data Exchange (ETDEWEB)

Rubin, David L.; Palmer, Mark A.

2011-08-02

In the International Linear Collider, two linear accelerators will accelerate bunches of positrons and electrons to over a hundred billion electron volts and collide them in a central detector. In order to obtain useful collision rates, the bunches, each containing twenty billion particles, must be compressed to a cross section of a few nanometers by a few hundred nanometers. In order to prepare these ultra high density bunches, damping rings (DRs) are employed before the linear accelerators. The DRs take the high emittance bunches that are provided by the electron and positron sources and, through the process of radiation damping, squeeze them into ultra low emittance beams that are ready for the main linear accelerators. In the damping rings, a number of effects can prevent the successful preparation of the beams. In the electron ring, an effect known as the fast ion instability can lead to beam growth and, in the positron ring, the build-up of an electron cloud (EC), which interacts with the circulating bunches, can produce the same effect. EC build-up and the subsequent interaction of the cloud with the positron beam in the DR have been identified as major risks for the successful construction of a linear collider. The CESRTA research program at the Cornell Electron Storage Ring (CESR) was developed in order to study the build-up of the EC, the details of its impact on ultra low emittance beams, as well as methods to mitigate the impact of the cloud. In the DR, the EC forms when synchrotron photons radiated from the circulating beam strike the walls of the vacuum chamber, resulting in the emission of photoelectrons. These low energy electrons can be accelerated across the vacuum chamber by the electric field of the beam, and strike the walls, causing the emission of secondary electrons. The secondary electrons are subsequently accelerated into the walls yet again via the same mechanism. The result is that the EC can rapidly begin to fill the vacuum chamber. In

Cloud Experiment. View inside the chamber with Jasper Kirkby, Head leader of the project.

CERN Multimedia

Maximilien Brice

2009-01-01

CLOUD, the cutting-edge physics experiment that will shed light on climate-related matters, has finished its assembly phase and is starting taking data using a beam of protons from the Proton Synchrotron.

Sedimentation Efficiency of Condensation Clouds in Substellar Atmospheres

Science.gov (United States)

Gao, Peter; Marley, Mark S.; Ackerman, Andrew S.

2018-03-01

Condensation clouds in substellar atmospheres have been widely inferred from spectra and photometric variability. Up until now, their horizontally averaged vertical distribution and mean particle size have been largely characterized using models, one of which is the eddy diffusion–sedimentation model from Ackerman and Marley that relies on a sedimentation efficiency parameter, f sed, to determine the vertical extent of clouds in the atmosphere. However, the physical processes controlling the vertical structure of clouds in substellar atmospheres are not well understood. In this work, we derive trends in f sed across a large range of eddy diffusivities (K zz ), gravities, material properties, and cloud formation pathways by fitting cloud distributions calculated by a more detailed cloud microphysics model. We find that f sed is dependent on K zz , but not gravity, when K zz is held constant. f sed is most sensitive to the nucleation rate of cloud particles, as determined by material properties like surface energy and molecular weight. High surface energy materials form fewer, larger cloud particles, leading to large f sed (>1), and vice versa for materials with low surface energy. For cloud formation via heterogeneous nucleation, f sed is sensitive to the condensation nuclei flux and radius, connecting cloud formation in substellar atmospheres to the objects’ formation environments and other atmospheric aerosols. These insights could lead to improved cloud models that help us better understand substellar atmospheres. For example, we demonstrate that f sed could increase with increasing cloud base depth in an atmosphere, shedding light on the nature of the brown dwarf L/T transition.

ATOMIC AND MOLECULAR CARBON AS A TRACER OF TRANSLUCENT CLOUDS

International Nuclear Information System (INIS)

Burgh, Eric B.; France, Kevin; Jenkins, Edward B.

2010-01-01

Using archival, high-resolution far-ultraviolet Hubble Space Telescope/Space Telescope Imaging Spectrograph spectra of 34 Galactic O and B stars, we measure C I column densities and compare them with measurements from the literature of CO and H 2 with regard to understanding the presence of translucent clouds along the line of sight. We find that the CO/H 2 and CO/C I ratios provide good discriminators for the presence of translucent material, and both increase as a function of molecular fraction, f N = 2N(H 2 )/N(H). We suggest that sightlines with values below CO/H 2 ∼10 -6 and CO/C I ∼1 contain mostly diffuse molecular clouds, while those with values above sample clouds in the transition region between diffuse and dark. These discriminating values are also consistent with the change in slope of the CO versus H 2 correlation near the column density at which CO shielding becomes important, as evidenced by the change in photochemistry regime studied by Sheffer et al. Based on the lack of correlation of the presence of translucent material with traditional measures of extinction, we recommend defining 'translucent clouds' based on the molecular content rather than line-of-sight extinction properties.

Numerical Simulations for the Beam-Induced Electron Cloud in the LHC Beam Screen

CERN Document Server

Brüning, Oliver Sim

1998-01-01

The following work summarises simulation results obtained at CERN for the beam-induced electron cloud and looks at possible cures for the heat load in the LHC beam screen. The synchrotron radiation in the LHC creates a continuous flow of photoelectrons. These electrons are accelerated by the electric field of the bunch and hit the vacuum chamber on the opposite side of the beam pipe where they crea te secondary electrons which are again accelerated by the next bunch. For a large secondary emission yield the above mechanism leads to an exponential growth of the electron cloud which is limited by space charge forces. The simulations use a two-dimensional mesh for the space charge calculations and include the effect of image charges on the vacuum chamber wall. Depending on the quantum yield for the production of photoelectrons, the secondary emission yield and the reflectivity, the heat load can vary from 0.1 W/m to more than 15 W/m.

Electroluminescent drift chamber with 16 μm spatial resolution

International Nuclear Information System (INIS)

Baskakov, V.I.; Dolgoshein, V.A.; Lebedenko, V.N.

1978-01-01

Studied are the characteristics of the dft electroluminscent chamber of an original design. For insuring high spatial resolution, the chamber has been filled with xenon to a pressure of 20 atm, which substantially decreases the electron diffusion during drift. Located at the end of the drift gap is an anode wire, 50 μm in dia. A strong electric field available near the thin wire causes electroluminescence of the electrons. The signal is localized within a small volume and contribution of the luminescence time in the total duration of a signal is small. In this case no electron multiplication occurs at all and, consequently, no space charge of positive ions takes place, which makes it possible to operate at very high loadings (2x10 6 particle/s). The characteristics of the chamber are measured in a beam of the Serpukhov accelerator. Use has been made of a model comprising two chambers, 5 mm thick, located successively along the beam with the effective area being 40x40 mm. The studies and analysis performed reveal that the drift electroluminescent chamber operates reliably in the wide range of the working gas pressure at an intensity of the incident particles up to 10 5 particle/s. The best resolution is obtained at a pressure of 20 atm and it equals 16 μm

The origin of the cloud chamber;Les mysteres de la chambre a brouillard

Energy Technology Data Exchange (ETDEWEB)

Fadel, K. [Palais de la Decouverte, Dept. de Physique, 75 - Paris (France)

2009-09-15

This article draws the story of the Wilson chamber. In the second half of the 19. century, a general trend among scientists in Great-Britain was still the observation and the imitation of nature, this romantic approach was launched by Goethe 50 years before. In 1895, Wilson as a young physicist tried to reproduce fog in laboratory. His challenge was to reduce the role of dust particles in the Aitken method: the expansion of wet-saturated air loaded with dust particles creates fog. In 1896, at the Cavendish laboratory, he discovered that ions could be very efficient 'dust particles' to condensate vapor and in 1898 he wrote that the expansion method is probably one of the most sensitive method to detect radiation emitted by radioactive materials. The Wilson chamber got a full success only from the twenties and was intensively used for 30 years in particles and nuclear physics laboratories. This detector allowed the experimental discovery of the positron, the muon and strange particles. (A.C.)

Application of Molecular Adsorber Coatings in Chamber A for the James Webb Space Telescope

Science.gov (United States)

Abraham, Nithin S.

2017-01-01

As a coating made of highly porous zeolite materials, the Molecular Adsorber Coating (MAC) was developed to capture outgassed molecular contaminants, such as hydrocarbons and silicones. For spaceflight applications, the adsorptive capabilities of the coating can alleviate on-orbit outgassing concerns on or near sensitive surfaces and instruments within the spacecraft. Similarly, this sprayable paint technology has proven to be significantly beneficial for ground-based space applications, in particular, for vacuum chamber environments. This presentation describes the application of the MAC technology for the James Webb Space Telescope (JWST) at NASA Johnson Space Center (JSC). The coating was used as a mitigation tool to entrap outgassed contaminants, specifically silicone-based diffusion pump oil, from within JSCs cryogenic optical vacuum chamber test facility called Chamber A. This presentation summarizes the background, fabrication, installation, chemical analysis test results, and future plans for the MAC technology, which was effectively used to protect the JWST test equipment from vacuum chamber contamination. As a coating made of highly porous zeolite materials, the Molecular Adsorber Coating (MAC) was developed to capture outgassed molecular contaminants, such as hydrocarbons and silicones. For spaceflight applications, the adsorptive capabilities of the coating can alleviate on-orbit outgassing concerns on or near sensitive surfaces and instruments within the spacecraft. Similarly, this sprayable paint technology has proven to be significantly beneficial for ground-based space applications, in particular, for vacuum chamber environments. This presentation describes the application of the MAC technology for the James Webb Space Telescope (JWST) at NASA Johnson Space Center (JSC). The coating was used as a mitigation tool to entrap outgassed contaminants, specifically silicone-based diffusion pump oil, from within JSCs cryogenic optical vacuum chamber test

ICES IN THE QUIESCENT IC 5146 DENSE CLOUD

International Nuclear Information System (INIS)

Chiar, J. E.; Pendleton, Y. J.; Allamandola, L. J.; Ennico, K.; Greene, T. P.; Roellig, T. L.; Sandford, S. A.; Boogert, A. C. A.; Geballe, T. R.; Mason, R. E.; Keane, J. V.; Lada, C. J.; Tielens, A. G. G. M.; Werner, M. W.; Whittet, D. C. B.; Decin, L.; Eriksson, K.

2011-01-01

This paper presents spectra in the 2 to 20 μm range of quiescent cloud material located in the IC 5146 cloud complex. The spectra were obtained with NASA's Infrared Telescope Facility SpeX instrument and the Spitzer Space Telescope's Infrared Spectrometer. We use these spectra to investigate dust and ice absorption features in pristine regions of the cloud that are unaltered by embedded stars. We find that the H 2 O-ice threshold extinction is 4.03 ± 0.05 mag. Once foreground extinction is taken into account, however, the threshold drops to 3.2 mag, equivalent to that found for the Taurus dark cloud, generally assumed to be the touchstone quiescent cloud against which all other dense cloud and embedded young stellar object observations are compared. Substructure in the trough of the silicate band for two sources is attributed to CH 3 OH and NH 3 in the ices, present at the ∼2% and ∼5% levels, respectively, relative to H 2 O-ice. The correlation of the silicate feature with the E(J - K) color excess is found to follow a much shallower slope relative to lines of sight that probe diffuse clouds, supporting the previous results by Chiar et al.

CLEARING OF ELECTRON CLOUD IN SNS

International Nuclear Information System (INIS)

WANG, L.; LEE, Y.Y.; RAPRIA, D.

2004-01-01

In this paper we describe a mechanism using the clearing electrodes to remove the electron cloud in the Spallation Neutron Source (SNS) accumulator ring, where strong multipacting could happen at median clearing fields. A similar phenomenon was reported in an experimental study at Los Alamos laboratory's Proton Synchrotron Ring (PSR). We also investigated the effectiveness of the solenoid's clearing mechanism in the SNS, which differs from the short bunch case, such as in B-factories. The titanium nitride (TiN) coating of the chamber walls was applied to reduce the secondary electron yield (SEY)

Laboratory investigation of nitrile ices of Titan's stratospheric clouds

Science.gov (United States)

Nna Mvondo, D.; Anderson, C. M.; McLain, J. L.; Samuelson, R. E.

2017-09-01

Titan's mid to lower stratosphere contains complex cloud systems of numerous organic ice particles comprised of both hydrocarbon and nitrile compounds. Most of these stratospheric ice clouds form as a result of vapor condensation formation processes. However, there are additional ice emission features such as dicyanoacetylene (C4N2) and the 220 cm-1 ice emission feature (the "Haystack") that are difficult to explain since there are no observed vapor emission features associated with these ices. In our laboratory, using a high-vacuum chamber coupled to a FTIR spectrometer, we are engaged in a dedicated investigation of Titan's stratospheric ices to interpret and constrain Cassini Composite InfraRed Spectrometer (CIRS) far-IR data. We will present laboratory transmittance spectra obtained for propionitrile (CH3CH2CN), cyanogen (C2N2) and hydrogen cyanide (HCN) ices, as well as various combinations of their mixtures, to better understand the cloud chemistry occurring in Titan's stratosphere.

Dvizhenie aerozoľnoi kapli v termodiffuzionnoi kamere

Czech Academy of Sciences Publication Activity Database

Bakanov, S. P.; Ždímal, Vladimír; Zaripov, Sh. KH.; Smolík, Jiří

2002-01-01

Roč. 66, č. 1 (2002), s. 95-101 R&D Projects: GA ČR GA104/97/1198 Grant - others:RFFI(RU) 99-01-00169 Keywords : aerosol particle * thermal diffusion * cloud chamber Subject RIV: CI - Industrial Chemistry, Chemical Engineering

Prognostic cloud water in the Los Alamos general circulation model

International Nuclear Information System (INIS)

Kristjansson, J.E.; Kao, C.Y.J.

1994-01-01

Most of today's general circulation models (GCMs) have a greatly simplified treatment of condensation and clouds. Recent observational studies of the earth's radiation budget have suggested cloud-related feedback mechanisms to be of tremendous importance for the issue of global change. Thus, an urgent need for improvements in the treatment of clouds in GCMs has arisen, especially as the clouds relate to radiation. In this paper, we investigate the effects of introducing prognostic cloud water into the Los Alamos GCM. The cloud water field, produced by both stratiform and convective condensation, is subject to 3-dimensional advection and vertical diffusion. The cloud water enters the radiation calculations through the longwave emissivity calculations. Results from several sensitivity simulations show that realistic water and precipitation fields can be obtained with the applied method. Comparisons with observations show that the most realistic results are obtained when more sophisticated schemes for moist convection are introduced at the same time. The model's cold bias is reduced and the zonal winds becomes stronger because of more realistic tropical convection

Relating cloud condensation nuclei activity and oxidation level of alpha-pinene secondary organic aerosols

DEFF Research Database (Denmark)

Foverskov, Mia Frosch Mogensbæk; Bilde, M.; DeCarlo, P. F.

2011-01-01

During a series of smog chamber experiments, the effects of chemical and photochemical aging on the ability of organic aerosols generated from ozonolysis of alpha-pinene to act as cloud condensation nuclei (CCN) were investigated. In particular, the study focused on the relation between oxygenation...

Brown Carbon Production in Ammonium- or Amine-Containing Aerosol Particles by Reactive Uptake of Methylglyoxal and Photolytic Cloud Cycling.

Science.gov (United States)

De Haan, David O; Hawkins, Lelia N; Welsh, Hannah G; Pednekar, Raunak; Casar, Jason R; Pennington, Elyse A; de Loera, Alexia; Jimenez, Natalie G; Symons, Michael A; Zauscher, Melanie; Pajunoja, Aki; Caponi, Lorenzo; Cazaunau, Mathieu; Formenti, Paola; Gratien, Aline; Pangui, Edouard; Doussin, Jean-François

2017-07-05

The effects of methylglyoxal uptake on the physical and optical properties of aerosol containing amines or ammonium sulfate were determined before and after cloud processing in a temperature- and RH-controlled chamber. The formation of brown carbon was observed upon methylglyoxal addition, detected as an increase in water-soluble organic carbon mass absorption coefficients below 370 nm and as a drop in single-scattering albedo at 450 nm. The imaginary refractive index component k 450 reached a maximum value of 0.03 ± 0.009 with aqueous glycine aerosol particles. Browning of solid particles occurred at rates limited by chamber mixing (cloud events with chamber lights on, suggesting photosensitized brown carbon formation. Despite these changes in optical aerosol characteristics, increases in dried aerosol mass were rarely observed (<1 μg/m 3 in all cases), consistent with previous experiments on methylglyoxal. Under dry, particle-free conditions, methylglyoxal reacted (presumably on chamber walls) with methylamine with a rate constant k = (9 ± 2) × 10 -17 cm 3 molecule -1 s -1 at 294 K and activation energy E a = 64 ± 37 kJ/mol.

Building materials. VOC emissions, diffusion behaviour and implications from their use

International Nuclear Information System (INIS)

Katsoyiannis, Athanasios; Leva, Paolo; Barrero-Moreno, Josefa; Kotzias, Dimitrios

2012-01-01

Five cement- and five lime-based building materials were examined in an environmental chamber for their emissions of Volatile Organic Compounds (VOCs). Typical VOCs were below detection limits, whereas not routinely analysed VOCs, like neopentyl glycol (NPG), dominated the cement-based products emissions, where, after 72 h, it was found to occur, in levels as high as 1400 μg m −3 , accounting for up to 93% of total VOCs. The concentrations of NPG were not considerably changed between the 24 and 72 h of sampling. The permeability of building materials was assessed through experiments with a dual environmental chamber; it was shown that building materials facilitate the diffusion of chemicals through their pores, reaching equilibrium relatively fast (6 h). - Highlights: ► Neopentyl glycol is reported in emissions from building materials for the first time. ► Neopentyl glycol dominates the VOC emissions from cement-based building materials. ► A dual chamber was developed to control diffusion through building materials. ► Building materials facilitate diffusion of indoor air pollutants through their pores. - Neopentyl glycol was detected in high concentrations in emissions from building materials.

CLOUD COMPUTING ADOPTION STRATEGIES AT PT TASPEN INDONESIA, Tbk

Directory of Open Access Journals (Sweden)

Julirzal Sarmedy

2014-10-01

Full Text Available PT. Taspen as Indonesian institution, is responsible for managing social insuranceprograms of civil servants. With branch offices and business partners who are geographicallydispersed throughout Indonesia, information technology is very important to support thebusiness processes. Cloud computing is a model of information technology services that couldpotentially increase the effectiveness and efficiency of PT. Taspen information system. Thisstudy examines the phenomenon exists at PT. Taspen in order to adopt cloud computing inthe information system, by using the framework of Technology-Organization-Environment,Diffusion of Innovation theory, and Partial Least Square method. Organizational factor isthe most dominant for PT. Taspen to adopt cloud computing. Referring to these findings,then a SWOT analysis and TOWS matrix are performed, which in this study recommendsthe implementation of a strategy model of cloud computing services that are private andgradually in process.

Ash cloud aviation advisories

Energy Technology Data Exchange (ETDEWEB)

Sullivan, T.J.; Ellis, J.S. [Lawrence Livermore National Lab., CA (United States); Schalk, W.W.; Nasstrom, J.S. [EG and G, Inc., Pleasanton, CA (United States)

1992-06-25

During the recent (12--22 June 1991) Mount Pinatubo volcano eruptions, the US Air Force Global Weather Central (AFGWC) requested assistance of the US Department of Energy`s Atmospheric Release Advisory Capability (ARAC) in creating volcanic ash cloud aviation advisories for the region of the Philippine Islands. Through application of its three-dimensional material transport and diffusion models using AFGWC meteorological analysis and forecast wind fields ARAC developed extensive analysis and 12-hourly forecast ash cloud position advisories extending to 48 hours for a period of five days. The advisories consisted of ``relative`` ash cloud concentrations in ten layers (surface-5,000 feet, 5,000--10,000 feet and every 10,000 feet to 90,000 feet). The ash was represented as a log-normal size distribution of 10--200 {mu}m diameter solid particles. Size-dependent ``ashfall`` was simulated over time as the eruption clouds dispersed. Except for an internal experimental attempt to model one of the Mount Redoubt, Alaska, eruptions (12/89), ARAC had no prior experience in modeling volcanic eruption ash hazards. For the cataclysmic eruption of 15--16 June, the complex three-dimensional atmospheric structure of the region produced dramatically divergent ash cloud patterns. The large eruptions (> 7--10 km) produced ash plume clouds with strong westward transport over the South China Sea, Southeast Asia, India and beyond. The low-level eruptions (< 7 km) and quasi-steady-state venting produced a plume which generally dispersed to the north and east throughout the support period. Modeling the sequence of eruptions presented a unique challenge. Although the initial approach proved viable, further refinement is necessary and possible. A distinct need exists to quantify eruptions consistently such that ``relative`` ash concentrations relate to specific aviation hazard categories.

Phase B-final definition and preliminary design study for the initial Atmospheric Cloud Physics Laboratory (ACPL). A spacelab mission payload

Science.gov (United States)

1976-01-01

Progress in the development of the Atmospheric Cloud Physics Laboratory is outlined. The fluid subsystem, aerosol generator, expansion chamber, optical system, control systems, and software are included.

A track chamber with controlled heat centres as a vertex detector for very high energy physics experiments

International Nuclear Information System (INIS)

Shcherbakov, Yu.A.

1989-01-01

A high-pressure vertex detector for high energy experiments is proposed on the basis of development of a new track detector of charged particles, which is a chamber with controlled centres. A possible design of this chamber is discussed. Laser illumination of a streamer chamber allows enough light for reading the information by means of a CCD device. Some characteristics of the set-up are considered in the paper. A possibility of using a new method for suppression of diffusion is discussed. 30 refs.; 7 figs.; 3 tabs

Intercomparison study and optical asphericity measurements of small ice particles in the CERN CLOUD experiment

Directory of Open Access Journals (Sweden)

L. Nichman

2017-09-01

Full Text Available Optical probes are frequently used for the detection of microphysical cloud particle properties such as liquid and ice phase, size and morphology. These properties can eventually influence the angular light scattering properties of cirrus clouds as well as the growth and accretion mechanisms of single cloud particles. In this study we compare four commonly used optical probes to examine their response to small cloud particles of different phase and asphericity. Cloud simulation experiments were conducted at the Cosmics Leaving OUtdoor Droplets (CLOUD chamber at European Organisation for Nuclear Research (CERN. The chamber was operated in a series of multi-step adiabatic expansions to produce growth and sublimation of ice particles at super- and subsaturated ice conditions and for initial temperatures of −30, −40 and −50 °C. The experiments were performed for ice cloud formation via homogeneous ice nucleation. We report the optical observations of small ice particles in deep convection and in situ cirrus simulations. Ice crystal asphericity deduced from measurements of spatially resolved single particle light scattering patterns by the Particle Phase Discriminator mark 2 (PPD-2K, Karlsruhe edition were compared with Cloud and Aerosol Spectrometer with Polarisation (CASPOL measurements and image roundness captured by the 3View Cloud Particle Imager (3V-CPI. Averaged path light scattering properties of the simulated ice clouds were measured using the Scattering Intensity Measurements for the Optical detectioN of icE (SIMONE and single particle scattering properties were measured by the CASPOL. We show the ambiguity of several optical measurements in ice fraction determination of homogeneously frozen ice in the case where sublimating quasi-spherical ice particles are present. Moreover, most of the instruments have difficulties of producing reliable ice fraction if small aspherical ice particles are present, and all of the instruments cannot

Theory and measurement of the electron cloud effect

International Nuclear Information System (INIS)

Harkey, K. C.

1999-01-01

Photoelectrons produced through the interaction of synchrotrons radiation and the vacuum chamber walls can be accelerated by a charged particle beam, acquiring sufficient energy to produce secondary electrons (SES) in collisions with the walls. If the secondary-electron yield (SEY) coefficient of the wall material is greater than one, a run-away condition can develop. In addition to the SEY, the degree of amplification depends on the beam intensity and temporal distribution. As the electron cloud builds up along a train of stored bunches, a transverse perturbation of the head bunch can be communicated to trailing bunches in a wakefield-like interaction with the cloud. The electron cloud effect is especially of concern for the high-intensity PEP-II (SLAC) and KEK B-factories and at the Large Hadron Collider (LHC) at CERN. An initiative was undertaken at the Advanced Photon Source (APS) storage ring to characterize the electron cloud in order to provide realistic limits on critical input parameters in the models and improve their predictive capabilities. An intensive research program was undertaken at CERN to address key issues relating to the LHC. After giving an overview, the recent theoretical and experimental results from the APS and the other laboratories will be discussed

Stability of interstellar clouds containing magnetic fields

International Nuclear Information System (INIS)

Langer, W.D.; and Bell Laboratories, Crawford Hill Laboratory, Holmdel, NJ)

1978-01-01

The stability of interstellar clouds against gravitational collapse and fragmentation in the presence of magnetic fields is investigated. A magnetic field can provide pressure support against collapse if it is strongly coupled to the neutral gas; this coupling is mediated by ion-neutral collisions in the gas. The time scale for the growth of perturbations in the gas is found to be a sensitive function of the fractional ion abundance of the gas. For a relatively large fractional ion abundance, corresponding to strong coupling, the collapse of the gas is retarded. Star formation is inhibited in dense clouds and the collapse time for diffuse clouds cn exceed the limit on their lifetime set by disruptive processes. For a small fractional ion abundance, the magnetic fields do not inhibit collapse and the distribution of the masses of collapsing fragments are likely to be quite different in regions of differing ion abundance. The solutions also predict the existence of large-scale density waves corresponding to two gravitational-magnetoacoustic modes. The conditions which best support these modes correspond to those found in the giant molecular clouds

The shift to Cloud Computing : The impact of disruptive technology on the enterprise software business ecosystem

NARCIS (Netherlands)

Nieuwenhuis, Lambert J.M.; Ehrenhard, Michel L.; Prause, Lars

2017-01-01

The rapid diffusion of Cloud Computing influences the way enterprise software is developed, distributed, and implemented. This uptake of Cloud Computing has profound implications for the IT industry and related industries, as it does not only affect the vendors' business models but also the other

Cloud and radiance measurements with the VIS/NIR Daylight Whole Sky Imager at Lindenberg (Germany)

Energy Technology Data Exchange (ETDEWEB)

Feister, U. [Deutscher Wetterdienst, Meteorologisches Observatorium Lindenberg (Germany); Shields, J. [Scripps Inst. of Oceanography, Univ. of California, San Diego (United States)

2005-10-01

Ground-based cloud data acquired with the whole sky imager (WSI) are analyzed in relation to measurements of solar radiation performed at the Lindenberg Meteorological Observatory. Cloud fractions derived by the cloud detection algorithm from WSI images acquired during daylight hours between 2002 and 2004 are compared with conventional cloud observations for the two sites Potsdam and Lindenberg, and also with ceilometer data of cloud-base heights at Lindenberg. The comparison statistics are discussed in the context of different principles of measurement. A few case studies illustrate the strong scattering effect of clouds on solar radiance and irradiance measured at the ground in different spectral regions. Particularly clouds close to the apparent position of the sun lead to strong enhancements of solar diffuse irradiance incident on horizontal planes and hemispheres that substantially exceed corresponding clear-sky values. Irradiances derived from WSI sky radiance fields are shown in comparison to pyranometer data of diffuse irradiance and radiative transfer model calculations performed for clear sky conditions. Examples of spectral sky radiances with moving contrails illustrate the significant enhancement the contrails have compared to clear sky, even though they may have a relatively small direct effect on global irradiance values. As contrails are observed at Lindenberg for about 18 to 19% of daylight hours, and part of them become clouds, the indirect impact of these changes on solar irradiance received at the ground may not be negligible. (orig.)

The application of an eddy diffusivity model to the dispersion of radionuclides in the atmosphere and the calculation of cloud gamma exposure

International Nuclear Information System (INIS)

Maul, P.R.

1981-05-01

A model which has been applied successfully to the study of the mesoscale transport of sulphur compounds can be adapted for radionuclides released from nuclear power stations. Although more complicated than the conventional Gaussian plume models it has several important advantages including the better representation of dry deposition and the variation of dispersion parameters with height above the surface. Building entrainment can be included in a straightforward manner and an approximate method can be used to incorporate isotope-dependent deposition velocities. A new method of calculating cloud gamma exposure is described which is particularly suited to eddy diffusivity models. This model will be used as an alternative to Gaussian plume methods in the BNL safety code NECTAR. (author)

Results from the CERN pilot CLOUD experiment

International Nuclear Information System (INIS)

Duplissy, J.; David, A.; Hahn, F.; Kirkby, J.; Onnela, A.; Veenhof, R.; Wilhelmsson, M.; Enghoff, M.B.; Avngaard, M.; Bondo, T.; Marsh, N.D.; Pedersen, O.P.; Polny, J.; Svensmark, H.; Svensmark, J.; Aplin, K.L.; Bingham, R.; Kellett, B.; Lockwood, M.; Arnold, F.; Aufmhoff, H.; Reichl, U.; Verheggen, B.; Baltensperger, U.; Wehrle, G.; Weingartner, E.; Carslaw, K.; Curtius, J.; Fastrup, B.; Pedersen, E.; Gagne, S.; Kulmala, M.; Laakso, L.; Nieminen, T.; Sipila, M.; Harrison, R.G.; Laaksonen, A.; Lillestol, E.; Makela, J.; Makhmutov, V.; Stozhkov, Y.; Seinfeld, J.H.; Stratmann, F.; Wex, H.; Viisanen, Y.; Wagner, P.E.; Winkler, P.M.

2010-01-01

During a 4-week run in October-November 2006, a pilot experiment was performed at the CERN Proton Synchrotron in preparation for the Cosmics Leaving Outdoor Droplets (CLOUD) experiment, whose aim is to study the possible influence of cosmic rays on clouds. The purpose of the pilot experiment was firstly to carry out exploratory measurements of the effect of ionising particle radiation on aerosol formation from trace H2SO4 vapour and secondly to provide technical input for the CLOUD design. A total of 44 nucleation bursts were produced and recorded, with formation rates of particles above the 3 nm detection threshold of between 0.1 and 100 cm -3 s -1 , and growth rates between 2 and 37 nm h -1 . The corresponding H2SO4 concentrations were typically around 106 cm -3 or less. The experimentally-measured formation rates and H2SO4 concentrations are comparable to those found in the atmosphere, supporting the idea that sulphuric acid is involved in the nucleation of atmospheric aerosols. However, sulphuric acid alone is not able to explain the observed rapid growth rates, which suggests the presence of additional trace vapours in the aerosol chamber, whose identity is unknown. By analyzing the charged fraction, a few of the aerosol bursts appear to have a contribution from ion-induced nucleation and ion-ion recombination to form neutral clusters. Some indications were also found for the accelerator beam timing and intensity to influence the aerosol particle formation rate at the highest experimental SO2 concentrations of 6 ppb, although none was found at lower concentrations. Overall, the exploratory measurements provide suggestive evidence for ion-induced nucleation or ion-ion recombination as sources of aerosol particles. However in order to quantify the conditions under which ion processes become significant, improvements are needed in controlling the experimental variables and in the reproducibility of the experiments. Finally, concerning technical aspects, the most

Atmospheric diffusion wind tunnel with automatic measurement

Energy Technology Data Exchange (ETDEWEB)

Maki, S; Sakai, J; Murata, E

1974-01-01

A wind tunnel which permits estimates of atmospheric diffusion is described. Smoke from power plant smoke stacks, for example, can be simulated and traced to determine the manner of diffusion in the air as well as the grade of dilution. The wind tunnel is also capable of temperature controlled diffusion tests in which temperature distribution inside the wind tunnel is controlled. A minimum wind velocity of 10 cm can be obtained with accuracy within plus or minus 0.05 percent using a controlled direct current motor; diffusion tests are often made at low wind velocity. Fully automatic measurements can be obtained by using a minicomputer so that the operation and reading of the measuring instruments can be remotely controlled from the measuring chamber. (Air Pollut. Abstr.)

A preliminary comparative study of the electron-cloud effect for the PSR, ISIS, and the ESS

International Nuclear Information System (INIS)

Furman, M.A.; Pivi, M.T.F.

2003-01-01

We present preliminary electron-cloud simulation results for the Proton Storage Ring (PSR) at LANL, ISIS at RAL, and the European Spallation Source (ESS). For each storage ring, we simulate the build-up and dissipation of the electron cloud (EC) in a representative field-free section of the vacuum chamber. For all three cases, we choose the same residual gas temperature, secondary emission yield (SEY), and secondary emission spectrum. Other variables such as proton loss rate, bunch profile, intensity and energy, residual gas pressure and chamber geometry, are set at the corresponding values for each machine. Under these assumptions, we conclude that, of the three machines, the PSR is the most severely affected by the electron cloud effect (ECE), followed by the ESS, with ISIS a distant third. We illustrate a strong sensitivity of the ECE to the longitudinal bunch profile by choosing two different shapes for the case of the PSR, and a weak sensitivity to residual gas pressure. This preliminary study does not address the ECE in other regions of the machine, nor the beam instability that might arise from the EC

Dimethylether: a low velocity, low diffusion drift chamber gas

International Nuclear Information System (INIS)

Villa, F.

1983-01-01

There are two main motivations to look for a low electron mobility gas: the first is that a low drift velocity relaxes the need to measure drift times with nanosecond (or even subnanosecond) precision; the second is that (in an ideal drift geometry), the capability of resolving two closely spaced tracks depends upon the ratio of electron mobility to ion mobility μ/sub e//μ/sub i/. Since μ/sub i/ is rather constant, the way to separate two tracks is to slow down the electrons. Many other properties are required besides low mobility and low drifting electron temperature: the gas should have a large (> 10 3 ) stable gain; it must be chemically stable and not oxic; it should not attack materials commonly used to fabricate drift chambers, etc. With these requirements in mind, we have tried a few promising (on paper) gases, either pure or in admixture with Argon. One of the gases examined, dimethylether [(CH 3 ) 2 )], has shown interesting characteristics

HD 62542: Probing the Bare, Dense Core of an Interstellar Cloud

Science.gov (United States)

Welty, Daniel; Sonnentrucker, Paule G.; Rachford, Brian; Snow, Theodore; York, Donald G.

2018-01-01

We discuss the interstellar absorption from many atomic and molecular species seen in high-resolution HST/STIS UV spectra of the moderately reddened B3-5 V star HD 62542 [E(B-V) ~ 0.35; AV ~ 1.2]. This remarkable sight line exhibits both very steep far-UV extinction and a high fraction of hydrogen in molecular form -- with strong absorption from CH, C2, CN, and CO but weak absorption from CH+ and most of the commonly observed diffuse interstellar bands. Most of the material appears to reside in a single narrow velocity component -- thus offering a rare opportunity to probe the relatively dense, primarily molecular core of a single interstellar cloud, with little associated diffuse atomic gas.Detailed analyses of the absorption-line profiles seen in the UV spectra reveal a number of properties of the main diffuse molecular cloud toward HD 62542:1) The depletions of Mg, Si, and Fe are more severe than those seen in any other sight line, but the depletions of Cl and Kr are very mild; the overall pattern of depletions differs somewhat from those derived from larger samples of Galactic sight lines.2) The rotational excitation of H2 and C2 indicates that the gas is fairly cold (Tk = 40-45 K) and moderately dense (nH > 420 cm-3) somewhat higher densities are suggested by the fine-structure excitation of neutral carbon.3) The excitation temperatures characterizing the rotational populations of both 12CO (11.7 K) and 13CO (7.7 K) are higher than those typically found for Galactic diffuse molecular clouds.4) Carbon is primarily singly ionized -- N(C+) > N(CO) > N(C).5) The relative abundances of various trace neutral atomic species reflect the effects of both the steep far-UV extinction and the severe depletions of some elements.6) Differences in line widths for the various atomic and molecular species are suggestive of differences in spatial distribution within the main cloud.Support for this study was provided by NASA, via STScI grant GO-12277.008-A.

Development of a time projection chamber with micro-pixel electrodes

International Nuclear Information System (INIS)

Kubo, Hidetoshi; Miuchi, Kentaro; Nagayoshi, Tsutomu; Ochi, Atsuhiko; Orito, Reiko; Takada, Atsushi; Tanimori, Toru; Ueno, Masaru

2003-01-01

A time projection chamber (TPC) based on a gaseous chamber with micro-pixel electrodes (μ-PIC) has been developed for measuring three-dimensional tracks of charged particles. The μ-PIC with a detection area of 10x10 cm 2 consists of a double-sided printing circuit board. Anode pixels are formed with 0.4 mm pitch on strips aligned perpendicular to the cathode strips in order to obtain a two-dimensional position. In the TPC with drift length of 8 cm, 4 mm wide field cage electrodes are aligned at 1 mm spaces and a uniform electric field of about 0.4 kV/cm is produced. For encoding of the three-dimensional position a synchronous readout system has been developed using Field Programmable Gate Arrays with 40 MHz clock. This system enables us to reconstruct the three-dimensional track of the particle at successive points like a cloud chamber even at high event rate. The drift velocity of electrons in the TPC was measured with the tracks of cosmic muons for 3 days, during which the TPC worked stably with the gas gain of 3000. With a radioisotope of gamma-ray source the three-dimensional track of a Compton scattered electron was taken successfully

Formation of molecules in interstellar clouds from singly and multiply ionized atoms

International Nuclear Information System (INIS)

Langer, W.D.; and NASA, Institute for Space Studies, Goddard Space Flight Center, New York)

1978-01-01

Soft X-ray and cosmic rays produce multiply ionized atoms which may initiate molecule production in interstellar clouds. This molecule production can occur via ion-molecule reactions with H 2 , either directly from the multiply ionized atom (e.g.,C ++ + H 2 →CH + + H + ), or indirectly from the singly ionized atoms (e.g., N + + H 2 →NH + + H) that are formed from the recombination or charge transfer of the highly ionized atom (e.g., N ++ + e→N + + hv). We investigate the contribution of these reactions to the abundances of carbon-, nitrogen-, and oxygen-bearing molecules in isobaric models of diffuse clouds. In the presence of the average flux estimated for the diffuse soft X-ray background, multiply ionized atoms contribute only minimally (a few percent) to carbon-bearing molecules such as CH. In the neighborhood of diffuse structures or discrete sources, however, where the X-ray flux is enhanced, multiple ionization is considerably more important for molecule production

Results from the CERN pilot CLOUD experiment

DEFF Research Database (Denmark)

Duplissy, J.; Enghoff, Martin Andreas Bødker; Aplin, K.L.

2010-01-01

the charged fraction, a few of the aerosol bursts appear to have a contribution from ion-induced nucleation and ion-ion recombination to form neutral clusters. Some indications were also found for the accelerator beam timing and intensity to influence the aerosol particle formation rate at the highest...... become significant, improvements are needed in controlling the experimental variables and in the reproducibility of the experiments. Finally, concerning technical aspects, the most important lessons for the CLOUD design include the stringent requirement of internal cleanliness of the aerosol chamber...

Ionization chamber

International Nuclear Information System (INIS)

Jilbert, P.H.

1975-01-01

The invention concerns ionization chambers with particular reference to air-equivalent ionization chambers. In order to ensure that similar chambers have similar sensitivities and responses the surface of the chamber bounding the active volume carries a conducting material, which may be a colloidal graphite, arranged in the form of lines so that the area of the conducting material occupies only a small proportion of the area of said surface. (U.S.)

An aerosol chamber investigation of the heterogeneous ice nucleating potential of refractory nanoparticles

Directory of Open Access Journals (Sweden)

R. W. Saunders

2010-02-01

Full Text Available Nanoparticles of iron oxide (crystalline and amorphous, silicon oxide and magnesium oxide were investigated for their propensity to nucleate ice over the temperature range 180–250 K, using the AIDA chamber in Karlsruhe, Germany.

All samples were observed to initiate ice formation via the deposition mode at threshold ice super-saturations (RHi_thresh ranging from 105% to 140% for temperatures below 220 K. Approximately 10% of amorphous Fe₂O₃ particles (modal diameter = 30 nm generated in situ from a photochemical aerosol reactor, led to ice nucleation at RHi_thresh = 140% at an initial chamber temperature of 182 K. Quantitative analysis using a singular hypothesis treatment provided a fitted function [n_s(190 K=10^{(3.33×s_ice+8.16}] for the variation in ice-active surface site density (n_s:m⁻² with ice saturation (s_ice for Fe₂O₃ nanoparticles. This was implemented in an aerosol-cloud model to determine a predicted deposition (mass accommodation coefficient for water vapour on ice of 0.1 at temperatures appropriate for the upper atmosphere. Classical nucleation theory was used to determine representative contact angles (θ for the different particle compositions. For the in situ generated Fe₂O₃ particles, a slight inverse temperature dependence was observed with θ = 10.5° at 182 K, decreasing to 9.0° at 200 K (compared with 10.2° and 11.4° respectively for the SiO₂ and MgO particle samples at the higher temperature.

These observations indicate that such refractory nanoparticles are relatively efficient materials for the nucleation of ice under the conditions studied in the chamber which correspond to cirrus cloud formation in the upper troposphere. The results also show that Fe₂O₃ particles do not act as ice

Tiny Molybdenites Tell Diffusion Tales

Science.gov (United States)

Stein, H. J.; Hannah, J. L.

2014-12-01

Diffusion invokes micron-scale exchange during crystal growth and dissolution in magma chambers on short time-scales. Fundamental to interpreting such data are assumptions on magma-fluid dynamics at all scales. Nevertheless, elemental diffusion profiles are used to estimate time scales for magma storage, eruption, and recharge. An underutilized timepiece to evaluate diffusion and 3D mobility of magmatic fluids is high-precision Re-Os dating of molybdenite. With spatially unique molybdenite samples from a young ore system (e.g., 1 Ma) and a double Os spike, analytical errors of 1-3 ka unambiguously separate events in time. Re-Os ages show that hydrous shallow magma chambers locally recharge and expel Cu-Mo-Au-silica as superimposed stockwork vein networks at time scales less than a few thousand years [1]. Re-Os ages provide diffusion rates controlled by a dynamic crystal mush, accumulation and expulsion of metalliferous fluid, and magma reorganization after explosive crystallization events. Importantly, this approach has broad application far from ore deposits. Here, we use Re-Os dating of molybdenite to assess time scales for generating and diffusing metals through the deep crust. To maximize opportunity for chemical diffusion, we use a continental-scale Sveconorwegian mylonite zone for the study area. A geologically constrained suite of molybdenite samples was acquired from quarry exposures. Molybdenite, previously unreported, is extremely scarce. Tiny but telling molybdenites include samples from like occurrences to assure geologic accuracy in Re-Os ages. Ages range from mid-Mesoproterozoic to mid-Neoproterozoic, and correspond to early metamorphic dehydration of a regionally widespread biotite-rich gneiss, localized melting of gneiss to form cm-m-scale K-feldspar ± quartz pods, development of vapor-rich, vuggy mm stringers that serve as volatile collection surfaces in felsic leucosomes, and low-angle (relative to foliation) cross-cutting cm-scale quartz veins

Electron Cloud Mitigation in the Spallation Neutron Source Ring

International Nuclear Information System (INIS)

Wei, J.; Blaskiewicz, Michael; Brodowski, J.; Cameron, P.; Davino, Daniele; Fedotov, A.; He, P.; Hseuh, H.; Lee, Y.Y.; Ludewig, H.; Meng, W.; Raparia, D.; Tuozzolo, J.; Zhang, S.Y.; Catalan-Lasheras, N.; Macek, R.J.; Furman, Miguel A.; Aleksandrov, A.; Cousineau, S.; Danilov, V.; Henderson, S.

2008-01-01

The Spallation Neutron Source (SNS) accumulator ring is designed to accumulate, via H - injection, protons of 2 MW beam power at 1 GeV kinetic energy at a repetition rate of 60 Hz [1]. At such beam intensity, electron-cloud is expected to be one of the intensity-limiting mechanisms that complicate ring operations. This paper summarizes mitigation strategy adopted in the design, both in suppressing electron-cloud formation and in enhancing Landau damping, including tapered magnetic field and monitoring system for the collection of stripped electrons at injection, TiN coated beam chamber for suppression of the secondary yield, clearing electrodes dedicated for the injection region and parasitic on BPMs around the ring, solenoid windings in the collimation region, and planning of vacuum systems for beam scrubbing upon operation

Electron-Cloud Build-up in the FNAL Main Injector

International Nuclear Information System (INIS)

Furman, M.A.

2007-01-01

We present a summary on ongoing simulation results for the electron-cloud buildup in the context of the proposed FNAL Main Injector (MI) intensity upgrade [1] in a fieldfree region at the location of the RFA electron detector [2]. By combining our simulated results for the electron flux at the vacuum chamber wall with the corresponding measurements obtained with the RFA we infer that the peak secondary electron yield (SEY) (delta) max is ∼> 1.4, and the average electron density is n e ∼> 10 10 m -3 at transition energy for the specific fill pattern and beam intensities defined below. The sensitivity of our results to several variables remains to be explored in order to reach more definitive results. Effects from the electron cloud on the beam are being investigated separately [3

Electron-cloud mitigation in the spallation neutron source ring

International Nuclear Information System (INIS)

Wei, J.; Blaskiewicz, M.; Brodowski, J.; Cameron, P.; Davino, D.; Fedotov, A.; He, P.; Hseuh, H.; Lee, Y.Y.; Meng, W.; Raparia, D.; Tuozzolo, J.; Zhang, S.Y.; Danilov, V.; Henderson, S.; Furman, M.; Pivi, M.; Macek, R.

2003-01-01

The Spallation Neutron Source (SNS) accumulator ring is designed to accumulate, via H- injection, protons of 2 MW beam power at 1 GeV kinetic energy at a repetition rate of 60 Hz [1]. At such beam intensity, electron cloud is expected to be one of the intensity-limiting mechanisms that complicate ring operations. This paper summarizes mitigation strategy adopted in the design, both in suppressing electron-cloud formation and in enhancing Landau damping, including tapered magnetic field and monitoring system for the collection of stripped electrons at injection, TiN coated beam chamber for suppression of the secondary yield, clearing electrodes dedicated for the injection region and parasitic on BPMs around the ring, solenoid windings in the collimation region, and planning of vacuum systems for beam scrubbing upon operation

A 19m Deep Well – a Downward Thermal Diffusion Cloud Chamber?

OpenAIRE

Holub, R.F.

2013-01-01

An unusual phenomenon, first observed on a clear summer day after several rainy days, were droplets constantly hitting the water surface in a 19 m deep and 2.4 m diameter water well. This droplet formation was occurring during the night as well. Since the droplet formation was near continuous, we called it “the eternal rain”. The water well is about 230 years old and located in the Benedictine monastery in Broumov, Czech Republic.

Cloud Infrastructure & Applications - CloudIA

Science.gov (United States)

Sulistio, Anthony; Reich, Christoph; Doelitzscher, Frank

The idea behind Cloud Computing is to deliver Infrastructure-as-a-Services and Software-as-a-Service over the Internet on an easy pay-per-use business model. To harness the potentials of Cloud Computing for e-Learning and research purposes, and to small- and medium-sized enterprises, the Hochschule Furtwangen University establishes a new project, called Cloud Infrastructure & Applications (CloudIA). The CloudIA project is a market-oriented cloud infrastructure that leverages different virtualization technologies, by supporting Service-Level Agreements for various service offerings. This paper describes the CloudIA project in details and mentions our early experiences in building a private cloud using an existing infrastructure.

Glove box chamber

International Nuclear Information System (INIS)

Cox, M.E.; Cox, M.E.

1975-01-01

An environmental chamber is described which enables an operator's hands to have direct access within the chamber without compromising a special atmosphere within such chamber. A pair of sleeves of a flexible material are sealed to the chamber around associated access apertures and project outwardly from such chamber. Each aperture is closed by a door which is openable from within the sleeve associated therewith so that upon an operator inserting his hand and arm through the sleeve, the operator can open the door to have access to the interior of the chamber. A container which is selectively separable from the remainder of the chamber is also provided to allow objects to be transferred from the chamber without such objects having to pass through the ambient atmosphere. An antechamber permitting objects to be passed directly into the chamber from the ambient atmosphere is included. (auth)

In-situ measurements of ice nucleating particles with FINCH (Fast Ice Nucleus Chamber)

Science.gov (United States)

Kohl, Rebecca; Frank, Fabian; Curtius, Joachim; Rose, Diana

2017-04-01

Ice nucleating particles (INPs), which are a small fraction of the total aerosol population, are capable of triggering ice formation under atmospheric conditions. Since INPs play an important role for the radiative properties of clouds as well as for the formation of precipitation it is important to get quantitative information on the ice activity of various atmospheric aerosol species. With the Fast Ice Nucleus Chamber (FINCH; Bundke et al., 2008) the number concentration of INP is determined at different freezing temperatures and supersaturations. In contrast to other commonly used INP counters, i.e., continuous flow diffusion chambers (CFDCs, DeMott et al., 2011), in FINCH the supersaturation is reached by mixing the sample flow of ambient aerosol with a warm moist as well as a cold dry airflow. By changing the flow rates and temperatures of the individual airflows the freezing temperature (down to -50°C) and supersaturation (up to above water saturation) can be varied relatively quickly. Particles that are ice active at the prescribed freezing temperature and supersaturation grow to crystals and are counted by a home-built optical particle counter (OPC) mounted below the chamber (Bundke et al., 2010). FINCH was operated during the four-week INUIT-BACCHUS-ACTRIS field campaign in Cyprus in April 2016. The measuring site was the location of the Cyprus Atmospheric Observatory (CAO) at Agia Marina Xyliatou, which is typically influenced by dust from the Sahara and the Middle East, an aerosol that is known to have relatively good ice nucleating ability. First results from this campaign will be presented. Acknowledgements: The authors thank the entire INUIT-BACCHUS-ACTRIS campaign team for their cooperation and support. The INUIT-2 project is financed by the German Research Foundation DFG (FOR 1525). The INUIT-Cyprus campaign is a cooperation with the EU-funded project BACCHUS and is also funded by ACTRIS-TNA. References: Bundke, U., Nillius, B., Jaenicke, R

Cosmic-rays, gas, and dust in nearby anticentre clouds. II. Interstellar phase transitions and the dark neutral medium

Science.gov (United States)

Remy, Q.; Grenier, I. A.; Marshall, D. J.; Casandjian, J. M.

2018-03-01

Aim. H I 21-cm and 12CO 2.6-mm line emissions trace the atomic and molecular gas phases, respectively, but they miss most of the opaque H I and diffuse H2 present in the dark neutral medium (DNM) at the transition between the H I-bright and CO-bright regions. Jointly probing H I, CO, and DNM gas, we aim to constrain the threshold of the H I-H2 transition in visual extinction, AV, and in total hydrogen column densities, NHtot. We also aim to measure gas mass fractions in the different phases and to test their relation to cloud properties. Methods: We have used dust optical depth measurements at 353 GHz, γ-ray maps at GeV energies, and H I and CO line data to trace the gas column densities and map the DNM in nearby clouds toward the Galactic anticentre and Chamaeleon regions. We have selected a subset of 15 individual clouds, from diffuse to star-forming structures, in order to study the different phases across each cloud and to probe changes from cloud to cloud. Results: The atomic fraction of the total hydrogen column density is observed to decrease in the (0.6-1) × 1021 cm-2 range in NHtot (AV ≈ 0.4 mag) because of the formation of H2 molecules. The onset of detectable CO intensities varies by only a factor of 4 from cloud to cloud, between 0.6 × 1021 cm-2 and 2.5 × 1021 cm-2 in total gas column density. We observe larger H2 column densities than linearly inferred from the CO intensities at AV > 3 mag because of the large CO optical thickness; the additional H2 mass in this regime represents on average 20% of the CO-inferred molecular mass. In the DNM envelopes, we find that the fraction of diffuse CO-dark H2 in the molecular column densities decreases with increasing AV in a cloud. For a half molecular DNM, the fraction decreases from more than 80% at 0.4 mag to less than 20% beyond 2 mag. In mass, the DNM fraction varies with the cloud properties. Clouds with low peak CO intensities exhibit large CO-dark H2 fractions in molecular mass, in particular the

Security and efficiency data sharing scheme for cloud storage

International Nuclear Information System (INIS)

Han, Ke; Li, Qingbo; Deng, Zhongliang

2016-01-01

With the adoption and diffusion of data sharing paradigm in cloud storage, there have been increasing demands and concerns for shared data security. Ciphertext Policy Attribute-Based Encryption (CP-ABE) is becoming a promising cryptographic solution to the security problem of shared data in cloud storage. However due to key escrow, backward security and inefficiency problems, existing CP-ABE schemes cannot be directly applied to cloud storage system. In this paper, an effective and secure access control scheme for shared data is proposed to solve those problems. The proposed scheme refines the security of existing CP-ABE based schemes. Specifically, key escrow and conclusion problem are addressed by dividing key generation center into several distributed semi-trusted parts. Moreover, secrecy revocation algorithm is proposed to address not only back secrecy but efficient problem in existing CP-ABE based scheme. Furthermore, security and performance analyses indicate that the proposed scheme is both secure and efficient for cloud storage.

Relating pressure measurements to phenomena observed in high speed video recordings during tests of explosive charges in a semi-confined blast chamber

CSIR Research Space (South Africa)

Mostert, FJ

2012-09-01

Full Text Available initiation of the charge. It was observed in the video recordings that the detonation product cloud exhibited pulsating behaviour due to the reflected shocks in the chamber analogous to the behaviour of the gas bubble in underwater explosions. This behaviour...

The role of diatom nanostructures in biasing diffusion to improve uptake in a patchy nutrient environment.

Directory of Open Access Journals (Sweden)

James G Mitchell

Full Text Available BACKGROUND: Diatoms are important single-celled autotrophs that dominate most lit aquatic environments and are distinguished by surficial frustules with intricate designs of unknown function. PRINCIPAL FINDINGS: We show that some frustule designs constrain diffusion to positively alter nutrient uptake. In nutrient gradients of 4 to 160 times over <5 cm, the screened-chambered morphology of Coscincodiscus sp. biases the nutrient diffusion towards the cell by at least 3.8 times the diffusion to the seawater. In contrast, the open-chambers of Thalassiosira eccentrica produce at least a 1.3 times diffusion advantage to the membrane over Coscincodiscus sp. when nutrients are homogeneous. SIGNIFICANCE: Diffusion constraint explains the success of particular diatom species at given times and the overall success of diatoms. The results help answer the unresolved question of how adjacent microplankton compete. Furthermore, diffusion constraint by supramembrane nanostructures to alter molecular diffusion suggests that microbes compete via supramembrane topology, a competitive mechanism not considered by the standard smooth-surface equations used for nutrient uptake nor in microbial ecology and cell physiology.

DIFFUSION OF A CLOUD-BASED SAP ENTERPRISE SYSTEM TO DANISH MUNICIPALITITES

DEFF Research Database (Denmark)

Frisenvang, Jakob Fogh; Pedersen, Christoffer Ejerskov; Svejvig, Per

as a Service (ESaaS) (Svejvig, Storgaard, and Møller, 2013). ESaaS encompasses Enterprise systems such as ERP, CRM, and BI systems. From a purely cloud-computing perspective, the delivery of such services does not significantly distinguish itself from the SaaS model, but from a practice perspective...

Diffusion of a Cloud-based SAP Enterprise System to Danish Municipalities

DEFF Research Database (Denmark)

Fogh Frisenvang, Jakob; Ejerskov Pedersen, Christoffer; Svejvig, Per

as a Service (ESaaS) (Svejvig, Storgaard, and Møller, 2013). ESaaS encompasses Enterprise systems such as ERP, CRM, and BI systems. From a purely cloud-computing perspective, the delivery of such services does not significantly distinguish itself from the SaaS model, but from a practice perspective...

New particle formation in the sulfuric acid–dimethylamine–water system: reevaluation of CLOUD chamber measurements and comparison to an aerosol nucleation and growth model

Directory of Open Access Journals (Sweden)

A. Kürten

2018-01-01

Full Text Available A recent CLOUD (Cosmics Leaving OUtdoor Droplets chamber study showed that sulfuric acid and dimethylamine produce new aerosols very efficiently and yield particle formation rates that are compatible with boundary layer observations. These previously published new particle formation (NPF rates are reanalyzed in the present study with an advanced method. The results show that the NPF rates at 1.7 nm are more than a factor of 10 faster than previously published due to earlier approximations in correcting particle measurements made at a larger detection threshold. The revised NPF rates agree almost perfectly with calculated rates from a kinetic aerosol model at different sizes (1.7 and 4.3 nm mobility diameter. In addition, modeled and measured size distributions show good agreement over a wide range of sizes (up to ca. 30 nm. Furthermore, the aerosol model is modified such that evaporation rates for some clusters can be taken into account; these evaporation rates were previously published from a flow tube study. Using this model, the findings from the present study and the flow tube experiment can be brought into good agreement for the high base-to-acid ratios (∼ 100 relevant for this study. This confirms that nucleation proceeds at rates that are compatible with collision-controlled (a.k.a. kinetically controlled NPF for the conditions during the CLOUD7 experiment (278 K, 38 % relative humidity, sulfuric acid concentration between 1  ×  106 and 3  ×  107 cm−3, and dimethylamine mixing ratio of ∼  40 pptv, i.e., 1  ×  109 cm−3.

wire chamber

CERN Multimedia

Proportional multi-wire chamber. Multi-wire detectors contain layers of positively and negatively charged wires enclosed in a chamber full of gas. A charged particle passing through the chamber knocks negatively charged electrons out of atoms in the gas, leaving behind positive ions. The electrons are pulled towards the positively charged wires. They collide with other atoms on the way, producing an avalanche of electrons and ions. The movement of these electrons and ions induces an electric pulse in the wires which is collected by fast electronics. The size of the pulse is proportional to the energy loss of the original particle. Proportional wire chambers allow a much quicker reading than the optical or magnetoscriptive readout wire chambers.

Track resolution in the RPC chamber

International Nuclear Information System (INIS)

Cardarelli, R.; Aielli, G.; Camarri, P.; Di Ciaccio, A.; Liberti, B.; Santonico, R.

2007-01-01

A new very promising read out, in addition to the well-known charge centroid method, is proposed for improving the space resolution in the Resistive Plate Chamber (RPC) in the sub-millimeter range. The method is based on the read out of the signal propagating in the graphite electrode which was simulated using a distributed resistance-capacitance model in SPICE. The results show that a good space-time correlation in the diffusion process is only possible by suitable signal processing. Three RPC detectors with the new layout and dedicated electronics were tested. The measured space resolution was in the order of a few 100μm

Sea spray as a source of ice nucleating particles - results from the AIDA Ocean03 campaign

Science.gov (United States)

Salter, M. E.; Ickes, L.; Adams, M.; Bierbauer, S.; Bilde, M.; Christiansen, S.; Ekman, A.; Gorokhova, E.; Höhler, K.; Kiselev, A. A.; Leck, C.; Mohr, C.; Mohler, O.; Murray, B. J.; Porter, G.; Ullrich, R.; Wagner, R.

2017-12-01

Clouds and their radiative effects are one of the major influences on the radiative fluxes in the atmosphere, but at the same time they remain the largest uncertainty in climate models. This lack of understanding is especially pronounced in the high Arctic. Summertime clouds can persist over long periods in this region, which is difficult to replicate in models based on our current understanding. The clouds most often encountered in the summertime high Arctic consist of a mixture of ice crystals and super-cooled water droplets, so-called mixed-phase clouds. This cloud type is sensitive to the availability of aerosol particles, which can act as cloud condensation nuclei and ice nuclei. However, since the high Arctic is a pristine region, aerosol particles are not very abundant, and the hypothesis of open leads in the Arctic as a potentially important source of cloud and ice nucleating particles via bubble bursting has emerged. In this context, we have conducted a series of experiments at the AIDA chamber at KIT, designed to investigate the mechanisms linking marine biology, seawater chemistry and aerosol physics/potential cloud impacts. During this campaign, two marine diatom species (Melosira arctica and Skeletonema marinoi) as well as sea surface microlayer samples collected during several Arctic Ocean research cruises were investigated. To aerosolize the samples, a variety of methods were used including a sea spray simulation chamber to mimic the process of bubble-bursting. The ice nucleating efficiency (mixed-phase cloud regime) of the samples was determined either directly in the AIDA chamber during adiabatic expansions, or using the INKA continuous flow diffusion chamber, or a cold stage. Results from the campaign along with the potential implications are presented.

Test chamber

NARCIS (Netherlands)

Leferink, Frank Bernardus Johannes

2009-01-01

A test chamber for measuring electromagnetic radiation emitted by an apparatus to be tested or for exposing an apparatus to be tested to an electromagnetic radiation field. The test chamber includes a reverberation chamber made of a conductive tent fabric. To create a statistically uniform field in

Method for measurement of radon diffusion and solubility in solid materials

Science.gov (United States)

Maier, Andreas; Weber, Uli; Dickmann, Jannis; Breckow, Joachim; van Beek, Patrick; Schardt, Dieter; Kraft, Gerhard; Fournier, Claudia

2018-02-01

In order to study the permeation i.e. the diffusion and solubility of radon gas in biological material, a new setup was constructed and a novel analysis was applied to obtain diffusion and solubility coefficients. Thin slabs of solid materials were installed between detector housing and the surrounding radon exposure chamber of 50 Ls volume. In this setup radon can diffuse through thin test samples into a cylindrical volume of 5 mm height and 20 mm diameter and reach an α-particle detector. There the 5.49 MeV α-decay of the penetrating radon atoms is measured by a silicon surface barrier detector. The time dependent activities inside the small detector volume are recorded after injection of a known radon activity concentration into the outer chamber. Analyzing the time behavior of the integral α-activity from radon in the small vessel, both, the diffusion coefficient and solubility of the test material can be determined, based on a new mathematical model of the diffusion process concerning the special boundary conditions given by the experimental setup. These first measurements were intended as proof of concept for the detection system and the data analysis. Thin polyethylene foils (LDPE) were selected as material for the diffusion measurements and the results were in agreement with data from literature. In further measurements, we will concentrate on biological material like bone, fat and other tissues.

Measurements of the angular distribution of diffuse irradiance

DEFF Research Database (Denmark)

Andersen, Elsa; Nielsen, Kristian Pagh; Dragsted, Janne

2015-01-01

Advanced solar resource assessment and forecasting is necessary for optimal solar energy utilization. In order to investigate the short-term resource variability, for instance caused by clouds it is necessary to investigate how clouds affect the solar irradiance, including the angular distribution...... of the solar irradiance. The investigation is part of the Danish contribution to the taskforce 46 within the International Energy Agency and financed by the Danish Energy Agency. The investigation focuses on the distribution of the diffuse solar irradiance and is based on horizontal measurements of the solar...

Formation of Massive Molecular Cloud Cores by Cloud-cloud Collision

OpenAIRE

Inoue, Tsuyoshi; Fukui, Yasuo

2013-01-01

Recent observations of molecular clouds around rich massive star clusters including NGC3603, Westerlund 2, and M20 revealed that the formation of massive stars could be triggered by a cloud-cloud collision. By using three-dimensional, isothermal, magnetohydrodynamics simulations with the effect of self-gravity, we demonstrate that massive, gravitationally unstable, molecular cloud cores are formed behind the strong shock waves induced by the cloud-cloud collision. We find that the massive mol...

Analysis of the contribution of sedimentation to bacterial mass transport in a parallel plate flow chamber

NARCIS (Netherlands)

Li, Jiuyi; Busscher, Henk J.; Norde, Willem; Sjollema, Jelmer

2011-01-01

In order to investigate bacterium-substratum interactions, understanding of bacterial mass transport is necessary. Comparisons of experimentally observed initial deposition rates with mass transport rates in parallel-plate-flow-chambers (PPFC) predicted by convective-diffusion yielded deposition

Production of a large area diffuse arc plasma with multiple cathode

International Nuclear Information System (INIS)

Wang Cheng; Cui Hai-Chao; Li Wan-Wan; Liao Meng-Ran; Xia Wei-Dong; Xia Wei-Luo

2017-01-01

An arc channel at atmospheric pressure tends to shrink generally. In this paper, a non-transferred DC arc plasma device with multiple cathode is introduced to produce a large area arc plasma at atmospheric pressure. This device is comprised of a 42-mm diameter tubular chamber, multiple cathode which is radially inserted into the chamber, and a tungsten anode with a nozzle in its center. In argon/helium atmosphere, a large area and circumferential homogenous diffuse arc plasma, which fills the entire cross section surrounded by the cathode tips, is observed. Results show that the uniformity and stability of diffuse arc plasma are strongly related to the plasma forming gas. Based on these experimental results, an explanation to the arc diffusion is suggested. Moreover, the electron excitation temperature and electron density measured in diffuse helium plasma are much lower than those of constricted arc column, which indicates the diffuse helium plasma probably deviates from the local thermodynamic equilibrium state. Unlike the common non-transferred arc plasma devices, this device can provide a condition for axial-fed feedstock particles. The plasma device is attempted to spheroidize alumina powders by using the central axis to send the powder. Results show that the powder produced is usually a typical hollow sphere. (paper)

Progress in studies of Electron-Cloud-Induced Optics Distortions at CESRTA

International Nuclear Information System (INIS)

Crittenden, J.A.; Calvey, J.R.; Dugan, G.F.; Kreinick, D.L.; Leong, Z.; Livezey, J.A.; Palmer, M.A.; Rubin, D.L.; Sagan, D.C.; Holtzapple, R.L.; Furman, M.A.; Penn, G.; Venturini, M.; Pivi, M.; Wang, L.; Harkay, K.

2010-01-01

The Cornell Electron Storage Ring Test Accelerator (CesrTA) program has included extensive measurements of coherent betatron tune shifts for a variety of electron and positron beam energies, bunch population levels, and bunch train configurations. The tune shifts have been shown to result primarily from the interaction of the beam with the space-charge field of the beam-induced low energy electron cloud in the vacuum chamber. Comparison to several advanced electron cloud simulation program packages has allowed determination of the sensitivity of these measurements to physical parameters characterizing the synchrotron radiation flux, the production of photoelectrons on the vacuum chamberwall, the beam emittance, lattice optics, and the secondary-electron yield model. We report on progress in understanding the cloud buildup and decay mechanisms in magnetic fields and in field-free regions, addressing quantitatively the precise determination of the physical parameters of the modeling. Validation of these models will serve as essential input in the design of damping rings for future high-energy linear colliders.

Direct measurement of Cu surface self-diffusion on a checked surface

International Nuclear Information System (INIS)

Cousty, Jacques; Peix, Roger; Perraillon, Bernard.

1976-01-01

A radiotracer technique ( 64 Cu) was developed to measure surface diffusion on copper surfaces of total impurity concentration not exceeding some 10 -3 monolayers. The apparatus used consists of a slow electron diffraction device, an Auger analysis spectrometer (CMA), an ion gun and an evaporation device assembled in an ultra-vacuum chamber holding a residual pressure below 10 -10 Torr. A sample handler enables the surface studied to be positioned in front of each of these instruments. During the diffusion treatment the chemical composition of the surface is checked intermittently, and afterwards the spread of the deposit is measured outside the ultravacuum chamber. Slices several microns thick are removed and dissolved separately in dishes containing HNO 3 . The activity is then measured with a flow counter [fr

Evolution of particle composition in CLOUD nucleation experiments

CERN Document Server

Keskinen, H; Joutsensaari, J; Tsagkogeorgas, G; Duplissy, J; Schobesberger, S; Gysel, M; Riccobono, F; Bianchi, F; Yli-Juuti, T; Lehtipalo, K; Rondo, L; Breitenlechner, M; Kupc, A; Almeida, J; Amorim, A; Dunne, E M; Downard, A J; Ehrhart, S; Franchin, A; Kajos, M K; Kirkby, J; Kurten, A; Nieminen, T; Makhmutov, V; Mathot, S; Miettinen, P; Onnela, A; Petaja, T; Praplan, A; Santos, F D; Schallhart, S; Sipila, M; Stozhkov, Y; Tome, A; Vaattovaara, P; Wimmer, D; Prevot, A; Dommen, J; Donahue, N M; Flagan, R C; Weingartner, E; Viisanen, Y; Riipinen, I; Hansel, A; Curtius, J; Kulmala, M; Worsnop, D R; Baltensperger, U; Wex, H; Stratmann, F; Laaksonen, A; Slowik, J G

2013-01-01

Sulphuric acid, ammonia, amines, and oxidised organics play a crucial role in nanoparticle formation in the atmosphere. In this study, we investigate the composition of nucleated nanoparticles formed from these compounds in the CLOUD (Cosmics Leaving Outdoor Droplets) chamber experiments at CERN (Centre europ ́ een pour la recherche nucl ́ eaire). The investigation was carried out via analysis of the particle hygroscopicity, ethanol affinity, oxidation state, and ion composition. Hygroscopicity was studied by a hygroscopic tandem differential mobility analyser and a cloud condensation nuclei counter, ethanol affinity by an organic differential mobility analyser and particle oxidation level by a high-resolution time-of-flight aerosol mass spectrometer. The ion composition was studied by an atmospheric pressure interface time-of-flight mass spectrometer. The volume fraction of the organics in the particles during theirgrowth from sizes of a few nanometers to tens of nanometers was derived from measured hygros...

High-latitude molecular clouds and infrared cirrus

International Nuclear Information System (INIS)

Vries, H.W. de.

1988-01-01

The high-latitude infrared cirrus detected by IRAS is identified with atomic and molecular clouds. These clouds are small (usually less than 1 sq. deg.) and show weak CO emission. On the basis of a distance of 100 pc they are characterized by a mass of a few solar masses and a radius of about 1 pc. Thermal radiation by dust as a results of heating by the diffuse interstellar radiation field is the most-plausible origin of the cirrus emission at far-infrared wavelengths. On the basis of plausible assumptions regarding the uniformity of both the gas-to-dust ratio and the heating and cooling of the dust, the flux density at 100 μm from regions with low visual extinction should be a good tracer of the gas column density. Indeed, the data show an approximately linear proportionality between N(HI), obtained from 21-cm observations, and I 100 (HI), the flux density from dust associated with HI. If the ratio of column density to flux density in high-latitude molecular clouds is equal to the corresponding relation in atomic ones, a value for the ratio of H 2 column density to CO velocity-integrated radiation temperature may be obtained. Although low-mass clouds may be large in number, the fraction of the Galactic molecular mass in the form of these clouds is probably no more than 1%

Zero-gravity cloud physics laboratory: Candidate experiments definition and preliminary concept studies

Science.gov (United States)

Eaton, L. R.; Greco, R. V.; Hollinden, A. B.

1973-01-01

The candidate definition studies on the zero-g cloud physics laboratory are covered. This laboratory will be an independent self-contained shuttle sortie payload. Several critical technology areas have been identified and studied to assure proper consideration in terms of engineering requirements for the final design. Areas include chambers, gas and particle generators, environmental controls, motion controls, change controls, observational techniques, and composition controls. This unique laboratory will allow studies to be performed without mechanical, aerodynamics, electrical, or other type techniques to support the object under study. This report also covers the candidate experiment definitions, chambers and experiment classes, laboratory concepts and plans, special supporting studies, early flight opportunities and payload planning data for overall shuttle payload requirements assessments.

Diffuse solar radiation and associated meteorological parameters in India

Directory of Open Access Journals (Sweden)

A. B. Bhattacharya

Full Text Available Solar diffuse radiation data including global radiation, shortwave and longwave balances, net radiation and sunshine hours have been extensively analyzed to study the variation of diffuse radiation with turbidity and cloud discharges appearing in the form of atmospherics over the tropics. Results of surface radiation measurements at Calcutta, Poona, Delhi and Madras are presented together with some meteorological parameters. The monthly values of diffuse radiation and the monthly ratios of diffuse to global solar radiation have been examined, with a special emphasis in relation to the noise level of atmospherics at Calcutta in the very low frequency band. The results exhibit some definite seasonal changes which appear to be in close agreement with one another.

Collection efficiency of charges in ionization chambers in presence of constant or variable radiation intensity

International Nuclear Information System (INIS)

Decuyper, J.

1970-01-01

The theoretical and experimental study of the collection of carriers built up by ionization in standard chambers, is made by varying the value of different acting parameters. In the presence of constant ionization intensity and under a D.C. and A.C. voltage, the effect of geometry, recombination, diffusion and attachment is analyzed. The compensation of thermal neutron D.C. chambers is equally considered. Under a time dependent ionization intensity and D.C. voltage, is then studied the effect of recombination on current response, and on the collection efficiency of all formed charges. (author) [fr

Dispersion modeling by kinematic simulation: Cloud dispersion model

International Nuclear Information System (INIS)

Fung, J C H; Perkins, R J

2008-01-01

A new technique has been developed to compute mean and fluctuating concentrations in complex turbulent flows (tidal current near a coast and deep ocean). An initial distribution of material is discretized into any small clouds which are advected by a combination of the mean flow and large scale turbulence. The turbulence can be simulated either by kinematic simulation (KS) or direct numerical simulation. The clouds also diffuse relative to their centroids; the statistics for this are obtained from a separate calculation of the growth of individual clouds in small scale turbulence, generated by KS. The ensemble of discrete clouds is periodically re-discretized, to limit the size of the small clouds and prevent overlapping. The model is illustrated with simulations of dispersion in uniform flow, and the results are compared with analytic, steady state solutions. The aim of this study is to understand how pollutants disperses in a turbulent flow through a numerical simulation of fluid particle motion in a random flow field generated by Fourier modes. Although this homogeneous turbulent is rather a 'simple' flow, it represents a building block toward understanding pollutant dispersion in more complex flow. The results presented here are preliminary in nature, but we expect that similar qualitative results should be observed in a genuine turbulent flow.

Relationship between cloud radiative forcing, cloud fraction and cloud albedo, and new surface-based approach for determining cloud albedo

OpenAIRE

Y. Liu; W. Wu; M. P. Jensen; T. Toto

2011-01-01

This paper focuses on three interconnected topics: (1) quantitative relationship between surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo; (2) surfaced-based approach for measuring cloud albedo; (3) multiscale (diurnal, annual and inter-annual) variations and covariations of surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo. An analytical expression is first derived to quantify the relationship between cloud radiative forcing, cloud fractio...

Differences between signal currents for both polarities of applied voltages on cavity ionization chambers

International Nuclear Information System (INIS)

Takata, N.

2000-01-01

It is necessary to obtain precise values of signal currents for the measurement of exposure rates for gamma rays with cavity ionization chambers. Signal currents are usually expected to have the same absolute values for both polarities of applied voltages. In the case of cylindrical cavity ionization chambers, volume recombination loss of ion pairs depends on the polarity of the applied voltage. This is because the values of mobility are different for positive and negative ions. It was found, however, that values of signal currents from a cylindrical ionization chamber change slightly more with a negative than with a positive applied voltage, even after being corrected for volume recombination loss. Moreover, absolute values of saturation currents, which are obtained by extrapolation of correction of initial recombination and diffusion loss, were larger for the negative than for the positive applied voltage. It is known from an experiment with parallel plate ionization chambers that when negative voltage is applied to the repeller electrode, the saturated signal current decreases with an increase in the applied voltage. This is because secondary electrons are accelerated and the stopping power of air for these electrons decreases. When positive voltage is applied, the reverse is true. The effects of acceleration and deceleration of secondary electrons by the electric field thus seem to cause a tendency opposite to the experimental results on the signal currents from cylindrical ionization chambers. The experimental results for the cylindrical ionization chamber can be explained as follows. When negative voltage is applied, secondary electrons are attracted to the central (collecting) electrode. Consequently, the path length of the trajectories of these secondary electrons in the ionization volume increases and signal current increases. The energy gain from the electric field by secondary electrons which stop in the ionization chamber also contributes to the

The Mobile Chamber

Science.gov (United States)

Scharfstein, Gregory; Cox, Russell

2012-01-01

A document discusses a simulation chamber that represents a shift from the thermal-vacuum chamber stereotype. This innovation, currently in development, combines the capabilities of space simulation chambers, the user-friendliness of modern-day electronics, and the modularity of plug-and-play computing. The Mobile Chamber is a customized test chamber that can be deployed with great ease, and is capable of bringing payloads at temperatures down to 20 K, in high vacuum, and with the desired metrology instruments integrated to the systems control. Flexure plans to lease Mobile Chambers, making them affordable for smaller budgets and available to a larger customer base. A key feature of this design will be an Apple iPad-like user interface that allows someone with minimal training to control the environment inside the chamber, and to simulate the required extreme environments. The feedback of thermal, pressure, and other measurements is delivered in a 3D CAD model of the chamber's payload and support hardware. This GUI will provide the user with a better understanding of the payload than any existing thermal-vacuum system.

Effects of inlet distortion on gas turbine combustion chamber exit temperature profiles

Science.gov (United States)

Maqsood, Omar Shahzada

Damage to a nozzle guide vane or blade, caused by non-uniform temperature distributions at the combustion chamber exit, is deleterious to turbine performance and can lead to expensive and time consuming overhaul and repair. A test rig was designed and constructed for the Allison 250-C20B combustion chamber to investigate the effects of inlet air distortion on the combustion chamber's exit temperature fields. The rig made use of the engine's diffuser tubes, combustion case, combustion liner, and first stage nozzle guide vane shield. Rig operating conditions simulated engine cruise conditions, matching the quasi-non-dimensional Mach number, equivalence ratio and Sauter mean diameter. The combustion chamber was tested with an even distribution of inlet air and a 4% difference in airflow at either side. An even distribution of inlet air to the combustion chamber did not create a uniform temperature profile and varying the inlet distribution of air exacerbated the profile's non-uniformity. The design of the combustion liner promoted the formation of an oval-shaped toroidal vortex inside the chamber, creating localized hot and cool sections separated by 90° that appeared in the exhaust. Uneven inlet air distributions skewed the oval vortex, increasing the temperature of the hot section nearest the side with the most mass flow rate and decreasing the temperature of the hot section on the opposite side. Keywords: Allison 250, Combustion, Dual-Entry, Exit Temperature Profile, Gas Turbine, Pattern Factor, Reverse Flow.

A Neural Network Approach to Infer Optical Depth of Thick Ice Clouds at Night

Science.gov (United States)

Minnis, P.; Hong, G.; Sun-Mack, S.; Chen, Yan; Smith, W. L., Jr.

2016-01-01

One of the roadblocks to continuously monitoring cloud properties is the tendency of clouds to become optically black at cloud optical depths (COD) of 6 or less. This constraint dramatically reduces the quantitative information content at night. A recent study found that because of their diffuse nature, ice clouds remain optically gray, to some extent, up to COD of 100 at certain wavelengths. Taking advantage of this weak dependency and the availability of COD retrievals from CloudSat, an artificial neural network algorithm was developed to estimate COD values up to 70 from common satellite imager infrared channels. The method was trained using matched 2007 CloudSat and Aqua MODIS data and is tested using similar data from 2008. The results show a significant improvement over the use of default values at night with high correlation. This paper summarizes the results and suggests paths for future improvement.

Electron-cloud simulation studies for the CERN-PS in the framework of the LHC Injectors Upgrade project

CERN Document Server

Rioja Fuentelsaz, Sergio

The present study aims to provide a consistent picture of the electron cloud effect in the CERN Proton Synchrotron (PS) and to investigate possible future limitations due to the requirements foreseen by the LHC Injectors Upgrade (LIU) project. It consists of a complete simulation survey of the electron cloud build-up in the different beam pipe sections of the ring depending on several controllable beam parameters and vacuum chamber surface properties, covering present and future operation parameters. As the combined function magnets of the accelerator constitute almost the $80\\%$ in length of the ring, the implementation of a new feature for the simulation of any external magnetic field on the PyECLOUD code, made it possible to perform this study. All the results of the simulations are given as a function of the vacuum chamber surface properties in order to deduce them, both locally and globally, when compared with experimental data. In a first step, we characterize locally the maximum possible number of ...

In-vitro transdentinal diffusion of monomers from adhesives.

Science.gov (United States)

Putzeys, Eveline; Duca, Radu Corneliu; Coppens, Lieve; Vanoirbeek, Jeroen; Godderis, Lode; Van Meerbeek, Bart; Van Landuyt, Kirsten L

2018-06-01

Biocompatibility of adhesives is important since adhesives may be applied on dentin near the pulp. Accurate knowledge of the quantity of monomers reaching the pulp is important to determine potential side effects. The aim of this study was to assess the transdentinal diffusion of residual monomers from dental adhesive systems using an in-vitro pulp chamber model. Dentin disks with a thickness of 300 µm were produced from human third molars. These disks were fixed between two open-ended glass tubes, representing an in-vitro pulp chamber. The etch-and-rinse adhesive OptiBond FL and the self-etch adhesive Clearfil SE Bond were applied to the dentin side of the disks, while on in the pulpal side, the glass tube was filled with 600 µL water. The transdentinal diffusion of different monomers was quantified using ultra-performance liquid chromatography-tandem mass spectrometry. The monomers HEMA, CQ, BisGMA, GPDM, 10-MDP and UDMA eluted from the dental materials and were able to diffuse through the dentin disks to a certain extent. Compounds with a lower molecular weight (uncured group: HEMA 7850 nmol and CQ 78.2 nmol) were more likely to elute and diffuse compared to monomers with a higher molecular weight (uncured group: BisGMA 0.42 nmol). When the adhesives were left uncured, diffusion was up to 10 times higher compared to the cured conditions. This in-vitro research resulted in the quantification of various monomers able to diffuse through dentin and therefore contributes to a more detailed understanding about the potential exposure of the dental pulp to monomers from dental adhesives. Biocompatibility of adhesives is important since adhesives may be applied on dentin near the pulp, where tubular density and diameter are greatest. Copyright © 2018. Published by Elsevier Ltd.

A dirty window diffuse and translucent molecular gas in the interstellar medium

CERN Document Server

Magnani, Loris

2017-01-01

This book provides an introduction to the physics of interstellar gas in the Galaxy. It deals with the diffuse interstellar medium which supplies a complex environment for exploring the neutral gas content of a galaxy like the Milky Way and the techniques necessary for studying this non-stellar component. After an initial exposition of the phases of the interstellar medium and the role of gas in a spiral galaxy, the authors discuss the transition from atomic to molecular gas. They then consider basic radiative transfer and molecular spectroscopy with particular emphasis on the molecules useful for studying low-density molecular gas. Observational techniques for investigating the gas and the dust component of the diffuse interstellar medium throughout the electromagnetic spectrum are explored emphasizing results from the recent Herschel and Planck missions. A brief exposition on dust in the diffuse interstellar medium is followed by a discussion of molecular clouds in general and high-latitude molecular clouds...

Joint CARE-ELAN, CARE-HHH-APD, and EUROTEV-WP3 Workshop on Electron Cloud Clearing

CERN Document Server

Scandale, Walter; Schulte, D; Zimmermann, F; Electron Cloud Effects and Technological Consequences; ECL2

2007-01-01

This report contains the Proceedings of the joint CARE-HHH-APD, CARE-ELAN, and EUROTEV-WP3 Mini-Workshop on 'Electron Cloud Clearing - Electron Cloud and Technical Consequences', "ECL2", held at CERN in Geneva, Switzerland, 1-2 March 2007). The ECL2 workshop explored novel technological remedies against electron-cloud formation in an accelerator beam pipe. A primary motivation for the workshop was the expected harmful electron-cloud effects in the upgraded LHC injectors and in future linear colliders, as well as recent beam observations in operating facilities like ANKA, CESR, KEKB, RHIC, and SPS. The solutions discussed at ECL2 included enamel-based clearing electrodes, slotted vacuum chambers, NEG coating, and grooves. Several of the proposed cures were assessed in terms of their clearing efficiency and the associated beam impedance. The workshop also reviewed new simulation tools like the 3D electron-ion build-up 'Faktor', modeling assumptions, analytical calculations, beam experiments, and laboratory meas...

Joint INFN-CERN-EuCARD-AccNet Workshop on Electron-Cloud Effects

CERN Document Server

Rumolo, Giovanni; Zimmermann, Frank; ECLOUD'12

2013-01-01

This report contains the Proceedings of the Joint INFN-Frascati, INFN-Pisa, CERN-LER and EuCARD-AccNet Mini-Workshop on Electron-Cloud Effects, “ECLOUD12”, held at La Biodola, Isola d’Elba, from 5 to 9 June 2012. The ECLOUD12 workshop reviewed many recent electron-cloud (EC) observations at existing storage rings, EC predictions for future accelerators, electron-cloud studies at DAFNE, EC mitigation by clearing electrodes and graphite/carbon coatings, modeling of incoherent EC effects, self-consistent simulations, synergies with other communities like the Valencia Space Consortium and the European Space Agency. ECLOUD12 discussed new EC observations at existing machines including LHC, CesrTA, PETRA-3, J-PARC, and FNAL MI; latest experimental efforts to characterize the EC – including EC diagnostics, experimental techniques, mitigation techniques such as coating and conditioning, advanced chemical and physical analyses of various vacuum-chamber surfaces, beam instabilities and emittance growth –; the...

Mixing processes in the vitreous chamber induced by eye rotations

Energy Technology Data Exchange (ETDEWEB)

Stocchino, Alessandro [Department of Civil, Environmental and Architectural Engineering, University of Genoa (Italy); Repetto, Rodolfo [Department of Engineering of Structures, Water and Soil, University of L' Aquila (Italy); Siggers, Jennifer H [Department of Bioengineering, Imperial College London, London SW7 2AZ (United Kingdom)], E-mail: jorma@diam.unige.it

2010-01-21

In this paper, we study a model of flow in the vitreous humour in the posterior chamber of the human eye, induced by saccadic eye rotations. We concentrate on the effect of the shape of the chamber upon the mixing properties of the induced flows. We make particle image velocimetry measurements of the fluid velocity in a transparent plastic (Perspex) model of the posterior chamber during sinusoidal torsional oscillations about a vertical axis. We use a Newtonian fluid to model the vitreous humour, which is most realistic when either the vitreous humour is liquefied or has been replaced by purely viscous tamponade fluids. The model of the posterior chamber is a sphere with an indentation, representing the effect of the lens. In spite of the purely periodic forcing, a steady streaming flow is generated, which plays a fundamental role in the mixing processes in the domain. The streaming flow differs markedly from that in a perfect sphere, and its topological characteristics change substantially as the frequency of oscillation varies. We discuss the flow characteristics in detail and show that, for physiological parameter values, the Peclet number (based on a suitable measure of the steady streaming velocity) is large, suggesting that advection strongly dominates over diffusion for mass transport phenomena. We also compute particle trajectories based on the streaming velocity and use these to investigate the stirring properties of the flow.

Mixing processes in the vitreous chamber induced by eye rotations

International Nuclear Information System (INIS)

Stocchino, Alessandro; Repetto, Rodolfo; Siggers, Jennifer H

2010-01-01

In this paper, we study a model of flow in the vitreous humour in the posterior chamber of the human eye, induced by saccadic eye rotations. We concentrate on the effect of the shape of the chamber upon the mixing properties of the induced flows. We make particle image velocimetry measurements of the fluid velocity in a transparent plastic (Perspex) model of the posterior chamber during sinusoidal torsional oscillations about a vertical axis. We use a Newtonian fluid to model the vitreous humour, which is most realistic when either the vitreous humour is liquefied or has been replaced by purely viscous tamponade fluids. The model of the posterior chamber is a sphere with an indentation, representing the effect of the lens. In spite of the purely periodic forcing, a steady streaming flow is generated, which plays a fundamental role in the mixing processes in the domain. The streaming flow differs markedly from that in a perfect sphere, and its topological characteristics change substantially as the frequency of oscillation varies. We discuss the flow characteristics in detail and show that, for physiological parameter values, the Peclet number (based on a suitable measure of the steady streaming velocity) is large, suggesting that advection strongly dominates over diffusion for mass transport phenomena. We also compute particle trajectories based on the streaming velocity and use these to investigate the stirring properties of the flow.

Parametrical analysis on the diffuse ceiling ventilation by experimental and numerical studies

DEFF Research Database (Denmark)

Zhang, Chen; Kristensen, Martin Heine; Jensen, Jakob Sølund

2016-01-01

This paper aims to investigate the performance of diffuse ceiling ventilation in a classroom. An experimental study is carried out in a test chamber to examine the impact of diffuse ceiling opening area on the system cooling capacity and thermal comfort. The results indicate that diffuse ceiling ....... The numerical results reveal that even distribution of heat sources gives a lower draught risk environment than centralized distribution. In addition, there is a significant increase on the draught risk with increase of room height....

Homogeneous Nucleation Rate Measurements of 1-Propanol in Helium: The Effect of Carrier Gas Pressure

Czech Academy of Sciences Publication Activity Database

Brus, David; Ždímal, Vladimír; Stratmann, F.

2006-01-01

Roč. 124, č. 16 (2006), Art. No. 164306 ISSN 0021-9606 R&D Projects: GA AV ČR(CZ) IAA2076203 Institutional research plan: CEZ:AV0Z40720504 Keywords : diffusion cloud-chamber * supersaturated vapor * background gases Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.166, year: 2006

A statistical theory on the turbulent diffusion of Gaussian puffs

International Nuclear Information System (INIS)

Mikkelsen, T.; Larsen, S.E.; Pecseli, H.L.

1982-12-01

The relative diffusion of a one-dimensional Gaussian cloud of particles is related to a two-particle covariance function in a homogeneous and stationary field of turbulence. A simple working approximation is suggested for the determination of this covariance function in terms of entirely Eulerian fields. Simple expressions are derived for the growth of the puff's standard deviation for diffusion times that are small compared to the integral time scale of the turbulence. (Auth.)

Drift chamber

International Nuclear Information System (INIS)

Inagaki, Yosuke

1977-01-01

Drift chamber is becoming an important detector in high energy physics as a precision and fast position detector because of its high spatial resolution and count-rate. The basic principle is that it utilizes the drift at constant speed of electrons ionized along the tracks of charged particles towards the anode wire in the nearly uniform electric field. The method of measuring drift time includes the analog and digital ones. This report describes about the construction of and the application of electric field to the drift chamber, mathematical analysis on the electric field and equipotential curve, derivation of spatial resolution and the factor for its determination, and selection of gas to be used. The performance test of the chamber was carried out using a small test chamber, the collimated β source of Sr-90, and 500 MeV/C electron beam from the 1.3 GeV electron synchrotron in the Institute of Nuclear Study, University of Tokyo. Most chambers to date adopted one dimensional read-out, but it is very advantageous if the two dimensional read-out is feasible with one chamber when the resolution in that direction is low. The typical methods of delay line and charge division for two dimensional read-out are described. The development of digital read-out system is underway, which can process the signal of a large scale drift chamber at high speed. (Wakatsuki, Y.)

Multiple chamber ionization detector

International Nuclear Information System (INIS)

Solomon, E.E.

1980-01-01

A multi-chambered ionisation detector enables the amount of radiation entering each chamber from a single radioactive, eg β, source to be varied by altering the proportion of the source protruding into each chamber. Electrodes define chambers and an extended radioactive source is movable to alter the source length in each chamber. Alternatively, the source is fixed relative to outer electrodes but the central electrode may be adjusted by an attached support altering the chamber dimensions and hence the length of source in each. Also disclosed are a centrally mounted source tiltable towards one or other chamber and a central electrode tiltable to alter chamber dimensions. (U.K.)

Dense-gas dispersion advection-diffusion model

International Nuclear Information System (INIS)

Ermak, D.L.

1992-07-01

A dense-gas version of the ADPIC particle-in-cell, advection- diffusion model was developed to simulate the atmospheric dispersion of denser-than-air releases. In developing the model, it was assumed that the dense-gas effects could be described in terms of the vertically-averaged thermodynamic properties and the local height of the cloud. The dense-gas effects were treated as a perturbation to the ambient thermodynamic properties (density and temperature), ground level heat flux, turbulence level (diffusivity), and windfield (gravity flow) within the local region of the dense-gas cloud. These perturbations were calculated from conservation of energy and conservation of momentum principles along with the ideal gas law equation of state for a mixture of gases. ADPIC, which is generally run in conjunction with a mass-conserving wind flow model to provide the advection field, contains all the dense-gas modifications within it. This feature provides the versatility of coupling the new dense-gas ADPIC with alternative wind flow models. The new dense-gas ADPIC has been used to simulate the atmospheric dispersion of ground-level, colder-than-ambient, denser-than-air releases and has compared favorably with the results of field-scale experiments

Process of advective diffusive enrichment using differential gradients and the effects of variations in relaxation times

International Nuclear Information System (INIS)

Suarez Antola R.; Bernasconi, G.; Bertolotti, Angel

1995-01-01

A multicomponent solution is considered in advective diffusion chambers between two half-permeable barriers. A mathematical model is developed to calculate the concentration fields in the chamber. A new enrichment process is proposed and assessed using a digital simulation of space-time dynamics, based on the analytical solution of the model

Doriot Climatic Chambers

Data.gov (United States)

Federal Laboratory Consortium — The Doriot Climatic Chambers are two, 60-feet long, 11-feet high, 15-feet wide chambers that are owned and operated by NSRDEC. The Doriot Climatic Chambers are among...

Ionization chamber

International Nuclear Information System (INIS)

1977-01-01

An improved ionization chamber type X-ray detector comprises a heavy gas at high pressure disposed between an anode and a cathode. An open grid structure is placed next to the anode and is maintained at a voltage intermediate between the cathode and anode potentials. The electric field which is produced by positive ions drifting towards the cathode is thus shielded from the anode. Current measuring circuits connected to the anode are, therefore, responsive only to electron current flow within the chamber and the recovery time of the chamber is shortened. The grid structure also serves to shield the anode from electrical currents which might otherwise be induced by mechanical vibrations in the ionization chamber structure

Cloud-Top Entrainment in Stratocumulus Clouds

Science.gov (United States)

Mellado, Juan Pedro

2017-01-01

Cloud entrainment, the mixing between cloudy and clear air at the boundary of clouds, constitutes one paradigm for the relevance of small scales in the Earth system: By regulating cloud lifetimes, meter- and submeter-scale processes at cloud boundaries can influence planetary-scale properties. Understanding cloud entrainment is difficult given the complexity and diversity of the associated phenomena, which include turbulence entrainment within a stratified medium, convective instabilities driven by radiative and evaporative cooling, shear instabilities, and cloud microphysics. Obtaining accurate data at the required small scales is also challenging, for both simulations and measurements. During the past few decades, however, high-resolution simulations and measurements have greatly advanced our understanding of the main mechanisms controlling cloud entrainment. This article reviews some of these advances, focusing on stratocumulus clouds, and indicates remaining challenges.

Cloud type comparisons of AIRS, CloudSat, and CALIPSO cloud height and amount

Directory of Open Access Journals (Sweden)

B. H. Kahn

2008-03-01

Full Text Available The precision of the two-layer cloud height fields derived from the Atmospheric Infrared Sounder (AIRS is explored and quantified for a five-day set of observations. Coincident profiles of vertical cloud structure by CloudSat, a 94 GHz profiling radar, and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO, are compared to AIRS for a wide range of cloud types. Bias and variability in cloud height differences are shown to have dependence on cloud type, height, and amount, as well as whether CloudSat or CALIPSO is used as the comparison standard. The CloudSat-AIRS biases and variability range from −4.3 to 0.5±1.2–3.6 km for all cloud types. Likewise, the CALIPSO-AIRS biases range from 0.6–3.0±1.2–3.6 km (−5.8 to −0.2±0.5–2.7 km for clouds ≥7 km (<7 km. The upper layer of AIRS has the greatest sensitivity to Altocumulus, Altostratus, Cirrus, Cumulonimbus, and Nimbostratus, whereas the lower layer has the greatest sensitivity to Cumulus and Stratocumulus. Although the bias and variability generally decrease with increasing cloud amount, the ability of AIRS to constrain cloud occurrence, height, and amount is demonstrated across all cloud types for many geophysical conditions. In particular, skill is demonstrated for thin Cirrus, as well as some Cumulus and Stratocumulus, cloud types infrared sounders typically struggle to quantify. Furthermore, some improvements in the AIRS Version 5 operational retrieval algorithm are demonstrated. However, limitations in AIRS cloud retrievals are also revealed, including the existence of spurious Cirrus near the tropopause and low cloud layers within Cumulonimbus and Nimbostratus clouds. Likely causes of spurious clouds are identified and the potential for further improvement is discussed.

Measurement of absorbed dose with a bone-equivalent extrapolation chamber

International Nuclear Information System (INIS)

DeBlois, Francois; Abdel-Rahman, Wamied; Seuntjens, Jan P.; Podgorsak, Ervin B.

2002-01-01

A hybrid phantom-embedded extrapolation chamber (PEEC) made of Solid Water trade mark sign and bone-equivalent material was used for determining absorbed dose in a bone-equivalent phantom irradiated with clinical radiation beams (cobalt-60 gamma rays; 6 and 18 MV x rays; and 9 and 15 MeV electrons). The dose was determined with the Spencer-Attix cavity theory, using ionization gradient measurements and an indirect determination of the chamber air-mass through measurements of chamber capacitance. The collected charge was corrected for ionic recombination and diffusion in the chamber air volume following the standard two-voltage technique. Due to the hybrid chamber design, correction factors accounting for scatter deficit and electrode composition were determined and applied in the dose equation to obtain absorbed dose in bone for the equivalent homogeneous bone phantom. Correction factors for graphite electrodes were calculated with Monte Carlo techniques and the calculated results were verified through relative air cavity dose measurements for three different polarizing electrode materials: graphite, steel, and brass in conjunction with a graphite collecting electrode. Scatter deficit, due mainly to loss of lateral scatter in the hybrid chamber, reduces the dose to the air cavity in the hybrid PEEC in comparison with full bone PEEC by 0.7% to ∼2% depending on beam quality and energy. In megavoltage photon and electron beams, graphite electrodes do not affect the dose measurement in the Solid Water trade mark sign PEEC but decrease the cavity dose by up to 5% in the bone-equivalent PEEC even for very thin graphite electrodes (<0.0025 cm). In conjunction with appropriate correction factors determined with Monte Carlo techniques, the uncalibrated hybrid PEEC can be used for measuring absorbed dose in bone material to within 2% for high-energy photon and electron beams

A comparison of shock-cloud and wind-cloud interactions: effect of increased cloud density contrast on cloud evolution

Science.gov (United States)

Goldsmith, K. J. A.; Pittard, J. M.

2018-05-01

The similarities, or otherwise, of a shock or wind interacting with a cloud of density contrast χ = 10 were explored in a previous paper. Here, we investigate such interactions with clouds of higher density contrast. We compare the adiabatic hydrodynamic interaction of a Mach 10 shock with a spherical cloud of χ = 103 with that of a cloud embedded in a wind with identical parameters to the post-shock flow. We find that initially there are only minor morphological differences between the shock-cloud and wind-cloud interactions, compared to when χ = 10. However, once the transmitted shock exits the cloud, the development of a turbulent wake and fragmentation of the cloud differs between the two simulations. On increasing the wind Mach number, we note the development of a thin, smooth tail of cloud material, which is then disrupted by the fragmentation of the cloud core and subsequent `mass-loading' of the flow. We find that the normalized cloud mixing time (tmix) is shorter at higher χ. However, a strong Mach number dependence on tmix and the normalized cloud drag time, t_{drag}^' }, is not observed. Mach-number-dependent values of tmix and t_{drag}^' } from comparable shock-cloud interactions converge towards the Mach-number-independent time-scales of the wind-cloud simulations. We find that high χ clouds can be accelerated up to 80-90 per cent of the wind velocity and travel large distances before being significantly mixed. However, complete mixing is not achieved in our simulations and at late times the flow remains perturbed.

Some results of radiative balance in atmospheres with clouds

International Nuclear Information System (INIS)

Anduckia Avila, Juan Carlos; Pelkowski, Joaquin

2000-01-01

Vertical profiles of temperature for a semi grey three-Layer atmosphere are established using a radiative equilibrium condition. The approximation contains the greenhouse effect, scattering by clouds in one direction and isotropic diffuse reflection at the planet's surface. Absorption of short- wave radiation is also considered in one of the three layers. Similar models are contained therein

Cloud Computing, Tieto Cloud Server Model

OpenAIRE

Suikkanen, Saara

2013-01-01

The purpose of this study is to find out what is cloud computing. To be able to make wise decisions when moving to cloud or considering it, companies need to understand what cloud is consists of. Which model suits best to they company, what should be taken into account before moving to cloud, what is the cloud broker role and also SWOT analysis of cloud? To be able to answer customer requirements and business demands, IT companies should develop and produce new service models. IT house T...

Electron cloud in various kinds of magnetic field of BEPCII

International Nuclear Information System (INIS)

Liu Yudong; Guo Zhiyuan; Qin Qing; Wang Jiuqing

2006-01-01

Electron cloud instability (ECI) may take place in a positron storage ring when the machine is operated with a multi-bunch positron beam. According to the actual shape of the vacuum chamber in the BEPCII, a programme which is different from the other simulation codes has been developed. Because of the distance between dipole magnet and sextupole, the quadrupole magnet of BEPCII is very short, much of the photoelectrons can be produced and can move in magnetic fields. The motion of electrons in various kinds of magnetic fields is studied in detail, especially for the solenoid field which will be wound in the vacuum pipe of BEPCII. Simulation shows that the solenoid field is very effective to confine the electrons to the vicinity of the vacuum chamber wall and to make an electron free region at the vacuum pipe centre. (authors)

Characterization of Mixed-Phase Clouds in the Laboratory

Science.gov (United States)

Foster, T. C.; Hallett, J.

2005-12-01

A technique was developed in which a mixed-phase cloud of controllable ice and water content is created. First a freezer filled with a water droplet cloud becomes supercooled. Then, in an isolated small volume of the freezer, an adjustable adiabatic expansion locally nucleates ice. Finally the two regions of the cloud are vigorously stirred together producing a mixed-phase cloud throughout the chamber. At this point the water droplets evaporate and the crystals grow at a slow measurable rate, until a fully glaciated cloud results. Experiments were carried out at temperatures near -20 C in a standard top-opening chest freezer. A cloud of supercooled water droplets several micrometers in diameter was produced by a commercial ultrasonic nebulizer. Ice was nucleated using the discharge of an empty compressed air pistol pumped to different initial pressures. In that process high-pressure room temperature air in the pistol expands adiabatically, cooling the air enough to nucleate water droplets which then freeze homogeneously if sufficiently cold. The freezer was partitioned with thick movable walls of foam material to isolate the ice cloud in a small volume of the freezer before mixing occurs. Clouds of supercooled water droplets or of ice particles are readily produced and examined in collimated white light beams. They look similar visually in some cases although normally large crystals with flat reflecting surfaces clearly differ due to the flashes of reflected light. When the pistol is discharged into the supercooled water cloud, it displays a distinct hazy bluish "plume." But discharge into the ice particle cloud leaves no such plume: that discharge only mixes the particles present. This discharge is a test of glaciation in our initially mixed freezer cloud. A visible plume indicates that supercooled water remains in the cloud and no plume indicates the cloud is entirely ice at a high concentration. Our first unsuccessful experiments were done with the freezer

Premixed combustion under electric field in a constant volume chamber

KAUST Repository

Cha, Min Suk

2012-12-01

The effects of electric fields on outwardly propagating premixed flames in a constant volume chamber were experimentally investigated. An electric plug, subjected to high electrical voltages, was used to generate electric fields inside the chamber. To minimize directional ionic wind effects, alternating current with frequency of 1 kHz was employed. Lean and rich fuel/air mixtures for both methane and propane were tested to investigate various preferential diffusion conditions. As a result, electrically induced instability showing cracked structure on the flame surface could be observed. This cracked structure enhanced flame propagation speed for the initial period of combustion and led to reduction in flame initiation and overall combustion duration times. However, by analyzing pressure data, it was found that overall burning rates are not much affected from the electric field for the pressurized combustion period. The reduction of overall combustion time is less sensitive to equivalence ratio for methane/air mixtures, whereas the results demonstrate pronounced effects on a lean mixture for propane. The improvement of combustion characteristics in lean mixtures will be beneficial to the design of lean burn engines. Two hypothetical mechanisms to explain the electrically induced instability were proposed: 1) ionic wind initiated hydrodynamic instability and 2) thermodiffusive instability through the modification of transport property such as mass diffusivity. © 2012 IEEE.

Premixed combustion under electric field in a constant volume chamber

KAUST Repository

Cha, Min; Lee, Yonggyu

2012-01-01

The effects of electric fields on outwardly propagating premixed flames in a constant volume chamber were experimentally investigated. An electric plug, subjected to high electrical voltages, was used to generate electric fields inside the chamber. To minimize directional ionic wind effects, alternating current with frequency of 1 kHz was employed. Lean and rich fuel/air mixtures for both methane and propane were tested to investigate various preferential diffusion conditions. As a result, electrically induced instability showing cracked structure on the flame surface could be observed. This cracked structure enhanced flame propagation speed for the initial period of combustion and led to reduction in flame initiation and overall combustion duration times. However, by analyzing pressure data, it was found that overall burning rates are not much affected from the electric field for the pressurized combustion period. The reduction of overall combustion time is less sensitive to equivalence ratio for methane/air mixtures, whereas the results demonstrate pronounced effects on a lean mixture for propane. The improvement of combustion characteristics in lean mixtures will be beneficial to the design of lean burn engines. Two hypothetical mechanisms to explain the electrically induced instability were proposed: 1) ionic wind initiated hydrodynamic instability and 2) thermodiffusive instability through the modification of transport property such as mass diffusivity. © 2012 IEEE.

An analytic model for the electrostatic contribution of the electron cloud to the vertical tune-shift

International Nuclear Information System (INIS)

Schaechter, Levi

2008-01-01

An analytic quasi-static model is developed for the analysis of the tune-shift associated with the presence of an electron cloud in a damping ring. The essential assumption is that in its direction of motion, a bunch experiences a uniform cloud density but the latter varies from one bunch to another. A second important component of the model is the life-time since it controls the build-up, the equilibrium as well as the decay of the cloud. It is demonstrated analytically that in case of a train of positron bunches, electrons may be trapped in the vertical direction for the entire train duration. Assuming that the ring is dominated by vertical magnetic fields due to either bends or wigglers, we found excellent agreement between the theoretical predictions and the experimental results reported at Cornell Electron/Positron Storage Ring. The ratio between the vertical and horizontal tune-shifts is shown to be indicative of the distribution of the cloud in the beam-chamber

+Cloud: An Agent-Based Cloud Computing Platform

OpenAIRE

González, Roberto; Hernández de la Iglesia, Daniel; de la Prieta Pintado, Fernando; Gil González, Ana Belén

2017-01-01

Cloud computing is revolutionizing the services provided through the Internet, and is continually adapting itself in order to maintain the quality of its services. This study presents the platform +Cloud, which proposes a cloud environment for storing information and files by following the cloud paradigm. This study also presents Warehouse 3.0, a cloud-based application that has been developed to validate the services provided by +Cloud.

Factors That Influence Adoption of Cloud Computing: An Empirical Study of Australian SMEs

Directory of Open Access Journals (Sweden)

Ishan Senarathna

2018-06-01

Full Text Available Cloud computing is a recent computing paradigm enabling organizations to have access to sophisticated computing services via the Internet on a fee-for-service basis. It provides Small and Medium-sized Enterprises (SMEs with opportunities to become as technologically advanced as their larger counterparts, without significant financial outlays. This paper examined the important factors that influence SMEs’ adoption of cloud computing technology. Drawing upon aspects of the Technology, Organization and Environment framework and Diffusion of Innovation Theory, we developed a research model of SMEs’ adoption of cloud computing and tested it through an online survey of 149 Australian SMEs. Data was analyzed using multiple regression methods, with results showing that SMEs were influenced by factors related to advantaging their organizational capability (i.e., relative advantage, quality of service and awareness rather than risk-related factors (i.e., security, privacy and flexibility. The findings offer insights to SMEs owners, Cloud service providers and government in establishing Cloud computing adoption strategies for SMEs.

TRACING THE MAGNETIC FIELD MORPHOLOGY OF THE LUPUS I MOLECULAR CLOUD

Energy Technology Data Exchange (ETDEWEB)

Franco, G. A. P. [Departamento de Física—ICEx—UFMG, Caixa Postal 702, 30.123-970 Belo Horizonte (Brazil); Alves, F. O., E-mail: franco@fisica.ufmg.br, E-mail: falves@mpe.mpg.de [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstr. 1, D-85748 Garching (Germany)

2015-07-01

Deep R-band CCD linear polarimetry collected for fields with lines of sight toward the Lupus I molecular cloud is used to investigate the properties of the magnetic field within this molecular cloud. The observed sample contains about 7000 stars, almost 2000 of them with a polarization signal-to-noise ratio larger than 5. These data cover almost the entire main molecular cloud and also sample two diffuse infrared patches in the neighborhood of Lupus I. The large-scale pattern of the plane-of-sky projection of the magnetic field is perpendicular to the main axis of Lupus I, but parallel to the two diffuse infrared patches. A detailed analysis of our polarization data combined with the Herschel/SPIRE 350 μm dust emission map shows that the principal filament of Lupus I is constituted by three main clumps that are acted on by magnetic fields that have different large-scale structural properties. These differences may be the reason for the observed distribution of pre- and protostellar objects along the molecular cloud and the cloud’s apparent evolutionary stage. On the other hand, assuming that the magnetic field is composed of large-scale and turbulent components, we find that the latter is rather similar in all three clumps. The estimated plane-of-sky component of the large-scale magnetic field ranges from about 70 to 200 μG in these clumps. The intensity increases toward the Galactic plane. The mass-to-magnetic flux ratio is much smaller than unity, implying that Lupus I is magnetically supported on large scales.

TRACING THE MAGNETIC FIELD MORPHOLOGY OF THE LUPUS I MOLECULAR CLOUD

International Nuclear Information System (INIS)

Franco, G. A. P.; Alves, F. O.

2015-01-01

Deep R-band CCD linear polarimetry collected for fields with lines of sight toward the Lupus I molecular cloud is used to investigate the properties of the magnetic field within this molecular cloud. The observed sample contains about 7000 stars, almost 2000 of them with a polarization signal-to-noise ratio larger than 5. These data cover almost the entire main molecular cloud and also sample two diffuse infrared patches in the neighborhood of Lupus I. The large-scale pattern of the plane-of-sky projection of the magnetic field is perpendicular to the main axis of Lupus I, but parallel to the two diffuse infrared patches. A detailed analysis of our polarization data combined with the Herschel/SPIRE 350 μm dust emission map shows that the principal filament of Lupus I is constituted by three main clumps that are acted on by magnetic fields that have different large-scale structural properties. These differences may be the reason for the observed distribution of pre- and protostellar objects along the molecular cloud and the cloud’s apparent evolutionary stage. On the other hand, assuming that the magnetic field is composed of large-scale and turbulent components, we find that the latter is rather similar in all three clumps. The estimated plane-of-sky component of the large-scale magnetic field ranges from about 70 to 200 μG in these clumps. The intensity increases toward the Galactic plane. The mass-to-magnetic flux ratio is much smaller than unity, implying that Lupus I is magnetically supported on large scales

A diffusivity model for predicting VOC diffusion in porous building materials based on fractal theory.

Science.gov (United States)

Liu, Yanfeng; Zhou, Xiaojun; Wang, Dengjia; Song, Cong; Liu, Jiaping

2015-12-15

Most building materials are porous media, and the internal diffusion coefficients of such materials have an important influences on the emission characteristics of volatile organic compounds (VOCs). The pore structure of porous building materials has a significant impact on the diffusion coefficient. However, the complex structural characteristics bring great difficulties to the model development. The existing prediction models of the diffusion coefficient are flawed and need to be improved. Using scanning electron microscope (SEM) observations and mercury intrusion porosimetry (MIP) tests of typical porous building materials, this study developed a new diffusivity model: the multistage series-connection fractal capillary-bundle (MSFC) model. The model considers the variable-diameter capillaries formed by macropores connected in series as the main mass transfer paths, and the diameter distribution of the capillary bundles obeys a fractal power law in the cross section. In addition, the tortuosity of the macrocapillary segments with different diameters is obtained by the fractal theory. Mesopores serve as the connections between the macrocapillary segments rather than as the main mass transfer paths. The theoretical results obtained using the MSFC model yielded a highly accurate prediction of the diffusion coefficients and were in a good agreement with the VOC concentration measurements in the environmental test chamber. Copyright © 2015 Elsevier B.V. All rights reserved.

Silicon Photonics Cloud (SiCloud)

DEFF Research Database (Denmark)

DeVore, P. T. S.; Jiang, Y.; Lynch, M.

2015-01-01

Silicon Photonics Cloud (SiCloud.org) is the first silicon photonics interactive web tool. Here we report new features of this tool including mode propagation parameters and mode distribution galleries for user specified waveguide dimensions and wavelengths.......Silicon Photonics Cloud (SiCloud.org) is the first silicon photonics interactive web tool. Here we report new features of this tool including mode propagation parameters and mode distribution galleries for user specified waveguide dimensions and wavelengths....

COSMIC ORIGINS SPECTROGRAPH OBSERVATIONS OF TRANSLUCENT CLOUDS: Cyg OB2 8A

International Nuclear Information System (INIS)

Snow, Theodore P.; Destree, Joshua D.; Burgh, Eric B.; Ferguson, Ryan M.; Danforth, Charles W.; Cordiner, Martin

2010-01-01

Data from the Cosmic Origins Spectrograph (COS) are presented for the first highly reddened target (Cyg OB2 8A) under the COS Science Team's guaranteed time allocation. Column densities of ionic, atomic, and molecular species are reported and implications are discussed. Data from Cyg OB2 8A demonstrate the ability to analyze highly reddened interstellar sight lines with the COS that were unavailable to previous UV instruments. Measured column densities indicate that the Cyg OB2 8A line of sight contains multiple diffuse clouds rather than a dominant translucent cloud.

Ambipolar diffusion regulated collapse of filaments threaded by perpendicular magnetic fields

Science.gov (United States)

Burge, C. A.; Van Loo, S.; Falle, S. A. E. G.; Hartquist, T. W.

2016-11-01

Context. In giant molecular clouds (GMCs), the fractional ionisation is low enough that the neutral and charged particles are weakly coupled. A consequence of this is that the magnetic flux redistributes within the cloud, allowing an initially magnetically supported region to collapse. Aims: We aim to elucidate the effects of ambipolar diffusion on the evolution of infinitely long filaments and the effect of decaying turbulence on that evolution. Methods: First, in ideal magnetohydrodynamics (MHD), a two-dimensional cylinder of an isothermal magnetised plasma with initially uniform density was allowed to evolve to an equilibrium state. Then, the response of the filament to ambipolar diffusion was followed using an adaptive mesh refinement multifluid MHD code. Various ambipolar resistivities were chosen to reflect different ratios of Jeans length to ambipolar diffusion length scale. To study the effect of turbulence on the ambipolar diffusion rate, we perturbed the equilibrium filament with a turbulent velocity field quantified by a rms sonic Mach number, Mrms, of 10, 3 or 1. Results: We numerically reproduce the density profiles for filaments that are in magnetohydrostatic and pressure equilibrium with their surroundings obtained in a published model and show that these equilibria are dynamically stable. If the effect of ambipolar diffusion is considered, these filaments lose magnetic support initiating cloud collapse. The filaments do not lose magnetic flux. Rather the magnetic flux is redistributed within the filament from the dense centre towards the diffuse envelope. The rate of the collapse is inversely proportional to the fractional ionisation and two gravitationally-driven ambipolar diffusion regimes for the collapse are observed as predicted in a published model. For high values of the ionisation coefficient, that is X ≥ 10-7, the gas is strongly coupled to the magnetic field and the Jeans length is larger than the ambipolar diffusion length scale. Then

Low-Frequency Carbon Recombination Lines in the Orion Molecular Cloud Complex

Science.gov (United States)

Tremblay, Chenoa D.; Jordan, Christopher H.; Cunningham, Maria; Jones, Paul A.; Hurley-Walker, Natasha

2018-05-01

We detail tentative detections of low-frequency carbon radio recombination lines from within the Orion molecular cloud complex observed at 99-129 MHz. These tentative detections include one alpha transition and one beta transition over three locations and are located within the diffuse regions of dust observed in the infrared at 100 μm, the Hα emission detected in the optical, and the synchrotron radiation observed in the radio. With these observations, we are able to study the radiation mechanism transition from collisionally pumped to radiatively pumped within the H ii regions within the Orion molecular cloud complex.

Cloud Processed CCN Suppress Stratus Cloud Drizzle

Science.gov (United States)

Hudson, J. G.; Noble, S. R., Jr.

2017-12-01

Conversion of sulfur dioxide to sulfate within cloud droplets increases the sizes and decreases the critical supersaturation, Sc, of cloud residual particles that had nucleated the droplets. Since other particles remain at the same sizes and Sc a size and Sc gap is often observed. Hudson et al. (2015) showed higher cloud droplet concentrations (Nc) in stratus clouds associated with bimodal high-resolution CCN spectra from the DRI CCN spectrometer compared to clouds associated with unimodal CCN spectra (not cloud processed). Here we show that CCN spectral shape (bimodal or unimodal) affects all aspects of stratus cloud microphysics and drizzle. Panel A shows mean differential cloud droplet spectra that have been divided according to traditional slopes, k, of the 131 measured CCN spectra in the Marine Stratus/Stratocumulus Experiment (MASE) off the Central California coast. K is generally high within the supersaturation, S, range of stratus clouds (< 0.5%). Because cloud processing decreases Sc of some particles, it reduces k. Panel A shows higher concentrations of small cloud droplets apparently grown on lower k CCN than clouds grown on higher k CCN. At small droplet sizes the concentrations follow the k order of the legend, black, red, green, blue (lowest to highest k). Above 13 µm diameter the lines cross and the hierarchy reverses so that blue (highest k) has the highest concentrations followed by green, red and black (lowest k). This reversed hierarchy continues into the drizzle size range (panel B) where the most drizzle drops, Nd, are in clouds grown on the least cloud-processed CCN (blue), while clouds grown on the most processed CCN (black) have the lowest Nd. Suppression of stratus cloud drizzle by cloud processing is an additional 2nd indirect aerosol effect (IAE) that along with the enhancement of 1st IAE by higher Nc (panel A) are above and beyond original IAE. However, further similar analysis is needed in other cloud regimes to determine if MASE was

Potential for improvement in estimation of solar diffuse irradiance

International Nuclear Information System (INIS)

Muneer, T.; Munawwar, S.

2006-01-01

Most of the meteorological stations around the world measure global irradiation and provide information on weather elements. Diffuse radiation measurement, however, is unavailable for many of those sites. This accentuates the need to estimate it whereupon it can be used for the simulation of solar applications. This paper explores the role of synoptic information, e.g. sunshine fraction, cloud cover and air mass on the basic k-k t relationship for nine sites across the globe. The influence on the k-k t regressions is studied qualitatively, and the inclusion of these parameters is suggested based on that. Thus, it is recommended to use the complementary data usually provided with the database apart from the global irradiation in order to estimate the diffuse irradiation more accurately. It was found by analysing each synoptic parameter individually that while the sunshine fraction showed a strong bearing, it was followed closely by cloud cover. Air mass, on the other hand, was found to be a weak parameter for general estimation of diffuse radiation. It was concluded that air mass if coupled with other synoptic parameters might improve the estimation accuracy, but it does not show much promise on its own when used with the global irradiation

Probing the diffuse interstellar medium with diffuse interstellar bands

Science.gov (United States)

Theodorus van Loon, Jacco; Bailey, Mandy; Farhang, Amin; Javadi, Atefeh; Khosroshahi, Habib

2015-08-01

For a century already, a large number of absorption bands have been known at optical wavelengths, called the diffuse interstellar bands (DIBs). While their carriers remain unidentified, the relative strengths of these bands in various environments make them interesting new probes of the diffuse interstellar medium (ISM). We present the results from two large, dedicated campaigns to map the ISM using DIBs measured in the high signal-to-noise spectra of hundreds of early-type stars: [1] in and around the Local Bubble using ESO's New Technology Telescope and the Isaac Newton Telescope, and [2] across both Magellanic Clouds using the Very Large Telescope and the Anglo-Australian Telescope. We discuss the implications for the structure and dynamics of the ISM, as well as the constraints these maps place on the nature of the carriers of the DIBs. Partial results have appeared in the recent literature (van Loon et al. 2013; Farhang et al. 2015a,b; Bailey, PhD thesis 2014) with the remainder being prepared for publication now.

Dual ionization chamber

International Nuclear Information System (INIS)

Mallory, J.; Turlej, Z.

1981-01-01

Dual ionization chambers are provided for use with an electronic smoke detector. The chambers are separated by electrically-conductive partition. A single radiation source extends through the partition into both chambers, ionizing the air in each. The mid-point current of the device may be balanced by adjusting the position of the source

Cloud vertical profiles derived from CALIPSO and CloudSat and a comparison with MODIS derived clouds

Science.gov (United States)

Kato, S.; Sun-Mack, S.; Miller, W. F.; Rose, F. G.; Minnis, P.; Wielicki, B. A.; Winker, D. M.; Stephens, G. L.; Charlock, T. P.; Collins, W. D.; Loeb, N. G.; Stackhouse, P. W.; Xu, K.

2008-05-01

CALIPSO and CloudSat from the a-train provide detailed information of vertical distribution of clouds and aerosols. The vertical distribution of cloud occurrence is derived from one month of CALIPSO and CloudSat data as a part of the effort of merging CALIPSO, CloudSat and MODIS with CERES data. This newly derived cloud profile is compared with the distribution of cloud top height derived from MODIS on Aqua from cloud algorithms used in the CERES project. The cloud base from MODIS is also estimated using an empirical formula based on the cloud top height and optical thickness, which is used in CERES processes. While MODIS detects mid and low level clouds over the Arctic in April fairly well when they are the topmost cloud layer, it underestimates high- level clouds. In addition, because the CERES-MODIS cloud algorithm is not able to detect multi-layer clouds and the empirical formula significantly underestimates the depth of high clouds, the occurrence of mid and low-level clouds is underestimated. This comparison does not consider sensitivity difference to thin clouds but we will impose an optical thickness threshold to CALIPSO derived clouds for a further comparison. The effect of such differences in the cloud profile to flux computations will also be discussed. In addition, the effect of cloud cover to the top-of-atmosphere flux over the Arctic using CERES SSF and FLASHFLUX products will be discussed.

The Effect of Heat Treatments and Coatings on the Outgassing Rate of Stainless Steel Chambers

Energy Technology Data Exchange (ETDEWEB)

Mamum, Md Abdullah A. [Old Dominion Univ., Norfolk, VA (United States); Elmustafa, Abdelmageed A, [Old Dominion Univ., Norfolk, VA (United States); Stutzman, Marcy L. [JLAB, Newport News, VA (United States); Adderley, Philip A. [JLAB, Newport News, VA (United States); Poelker, Matthew [JLAB, Newport News, VA (United States)

2014-03-01

The outgassing rates of four nominally identical 304L stainless steel vacuum chambers were measured to determine the effect of chamber coatings and heat treatments. One chamber was coated with titanium nitride (TiN) and one with amorphous silicon (a-Si) immediately following fabrication. One chamber remained uncoated throughout, and the last chamber was first tested without any coating, and then coated with a-Si following a series of heat treatments. The outgassing rate of each chamber was measured at room temperatures between 15 and 30 deg C following bakes at temperatures between 90 and 400 deg C. Measurements for bare steel showed a significant reduction in the outgassing rate by more than a factor of 20 after a 400 deg C heat treatment (3.5 x 10{sup 12} TorrL s{sup -1}cm{sup -2} prior to heat treatment, reduced to 1.7 x 10{ sup -13} TorrL s{sup -1}cm{sup -2} following heat treatment). The chambers that were coated with a-Si showed minimal change in outgassing rates with heat treatment, though an outgassing rate reduced by heat treatments prior to a-Si coating was successfully preserved throughout a series of bakes. The TiN coated chamber exhibited remarkably low outgassing rates, up to four orders of magnitude lower than the uncoated stainless steel. An evaluation of coating composition suggests the presence of elemental titanium which could provide pumping and lead to an artificially low outgassing rate. The outgassing results are discussed in terms of diffusion-limited versus recombination-limited processes.

Measurement and modeling of shortwave irradiance components in cloud-free atmospheres

Energy Technology Data Exchange (ETDEWEB)

Halthore, R.N.

1999-08-04

Atmosphere scatters and absorbs incident solar radiation modifying its spectral content and decreasing its intensity at the surface. It is very useful to classify the earth-atmospheric solar radiation into several components--direct solar surface irradiance (E{sub direct}), diffuse-sky downward surface irradiance (E{sub diffuse}), total surface irradiance, and upwelling flux at the surface and at the top-of-the atmosphere. E{sub direct} depends only on the extinction properties of the atmosphere without regard to details of extinction, namely scattering or absorption; furthermore it can be accurately measured to high accuracy (0.3%) with the aid of an active cavity radiometer (ACR). E{sub diffuse} has relatively larger uncertainties both in its measurement using shaded pyranometers and in model estimates, owing to the difficulty in accurately characterizing pyranometers and in measuring model inputs such as surface reflectance, aerosol single scattering albedo, and phase function. Radiative transfer model simulations of the above surface radiation components in cloud-free skies using measured atmospheric properties show that while E{sub direct} estimates are closer to measurements, E{sub diffuse} is overestimated by an amount larger than the combined uncertainties in model inputs and measurements, illustrating a fundamental gap in the understanding of the magnitude of atmospheric absorption in cloud-free skies. The excess continuum type absorption required to reduce the E{sub diffuse} model overestimate ({approximately}3--8% absorptance) would significantly impact climate prediction and remote sensing. It is not clear at present what the source for this continuum absorption is. Here issues related to measurements and modeling of the surface irradiance components are discussed.

The effect of catastrophic collisional fragmentation and diffuse medium accretion on a computational interstellar dust system

Science.gov (United States)

Liffman, Kurt

1990-01-01

The effects of catastrophic collisional fragmentation and diffuse medium accretion on a the interstellar dust system are computed using a Monte Carlo computer model. The Monte Carlo code has as its basis an analytic solution of the bulk chemical evolution of a two-phase interstellar medium, described by Liffman and Clayton (1989). The model is subjected to numerous different interstellar processes as it transfers from one interstellar phase to another. Collisional fragmentation was found to be the dominant physical process that shapes the size spectrum of interstellar dust. It was found that, in the diffuse cloud phase, 90 percent of the refractory material is locked up in the dust grains, primarily due to accretion in the molecular medium. This result is consistent with the observed depletions of silicon. Depletions were found to be affected only slightly by diffuse cloud accretion.

Dispersion of the Volcanic Sulfate Cloud from the Mount Pinatubo Eruption

Science.gov (United States)

Aquila, Valentina; Oman, Luke D.; Stolarski, Richard S.; Colarco, Peter R.; Newman, Paul A.

2012-01-01

We simulate the transport of the volcanic cloud from the 1991 eruption of Mount Pinatubo with the GEOS-5 general circulation model. Our simulations are in good agreement with observational data. We tested the importance of initial condition corresponding to the specific meteorological situation at the time of the eruption by employing reanalysis from MERRA. We found no significant difference in the transport of the cloud. We show how the inclusion of the interaction between volcanic sulfate aerosol and radiation is essential for a reliable simulation of the transport of the volcanic cloud. The absorption of long wave radiation by the volcanic sulfate induces a rising of the volcanic cloud up to the middle stratosphere, combined with divergent motion from the latitude of the eruption to the tropics. Our simulations indicate that the cloud diffuses to the northern hemisphere through a lower stratospheric pathway, and to mid- and high latitudes of the southern hemisphere through a middle stratospheric pathway, centered at about 30 hPa. The direction of the middle stratospheric pathway depends on the season. We did not detect any significant change of the mixing between tropics and mid- and high latitudes in the southern hemisphere.

Are relative depletions altered inside diffuse clouds?

International Nuclear Information System (INIS)

Joseph, C.L.

1988-01-01

The data of Jenkins, Savage, and Spitzer (1986) were used to analyze interstellar abundances and depletions of Fe, P, Mg, and Mn toward 37 stars, spanning nearly 1.0 (dex) in mean line-of-sight depletion. It was found that the depletions of these elements are linearly correlated and do not show evidence of differences in the rates of depletion or sputtering from one element to another. For a given level of overall depletion, the sightline-to-sightline rms variance in the depletion for each of these elements was less than 0.16 (dex), which is significantly smaller than is the element-to-element variance. The results suggest that, for most diffuse lines of sight, the relative abundances of these elements are set early in the lifetime of the grains and are not altered significantly thereafter. 53 references

Competition for water vapour results in suppression of ice formation in mixed-phase clouds

Directory of Open Access Journals (Sweden)

E. L. Simpson

2018-05-01

Full Text Available The formation of ice in clouds can initiate precipitation and influence a cloud's reflectivity and lifetime, affecting climate to a highly uncertain degree. Nucleation of ice at elevated temperatures requires an ice nucleating particle (INP, which results in so-called heterogeneous freezing. Previously reported measurements for the ability of a particle to nucleate ice have been made in the absence of other aerosol which will act as cloud condensation nuclei (CCN and are ubiquitous in the atmosphere. Here we show that CCN can outcompete INPs for available water vapour thus suppressing ice formation, which has the potential to significantly affect the Earth's radiation budget. The magnitude of this suppression is shown to be dependent on the mass of condensed water required for freezing. Here we show that ice formation in a state-of-the-art cloud parcel model is strongly dependent on the criteria for heterogeneous freezing selected from those previously hypothesised. We have developed an alternative criteria which agrees well with observations from cloud chamber experiments. This study demonstrates the dominant role that competition for water vapour can play in ice formation, highlighting both a need for clarity in the requirements for heterogeneous freezing and for measurements under atmospherically appropriate conditions.

Competition for water vapour results in suppression of ice formation in mixed-phase clouds

Science.gov (United States)

Simpson, Emma L.; Connolly, Paul J.; McFiggans, Gordon

2018-05-01

The formation of ice in clouds can initiate precipitation and influence a cloud's reflectivity and lifetime, affecting climate to a highly uncertain degree. Nucleation of ice at elevated temperatures requires an ice nucleating particle (INP), which results in so-called heterogeneous freezing. Previously reported measurements for the ability of a particle to nucleate ice have been made in the absence of other aerosol which will act as cloud condensation nuclei (CCN) and are ubiquitous in the atmosphere. Here we show that CCN can outcompete INPs for available water vapour thus suppressing ice formation, which has the potential to significantly affect the Earth's radiation budget. The magnitude of this suppression is shown to be dependent on the mass of condensed water required for freezing. Here we show that ice formation in a state-of-the-art cloud parcel model is strongly dependent on the criteria for heterogeneous freezing selected from those previously hypothesised. We have developed an alternative criteria which agrees well with observations from cloud chamber experiments. This study demonstrates the dominant role that competition for water vapour can play in ice formation, highlighting both a need for clarity in the requirements for heterogeneous freezing and for measurements under atmospherically appropriate conditions.

Spectral Analysis and Computation of Effective Diffusivities for Steady Random Flows

Science.gov (United States)

2016-04-28

even in the motion of sea ice floes influenced by winds and ocean currents. The long time, large scale behavior of such systems is equivalent to an...flow plays a key role in many important processes in the global climate system [55] and Earth’s ecosys- tems [14]. Advection of geophysical fluids...HOMOGENIZATION OF THE ADVECTION-DIFFUSION EQUATION The dispersion of a cloud of passive scalars with density φ diffusing with molecular dif- fusivity ε and

Confinement and Isotropization of Galactic Cosmic Rays by Molecular-Cloud Magnetic Mirrors When Turbulent Scattering Is Weak

International Nuclear Information System (INIS)

Chandran, Benjamin D. G.

2000-01-01

Theoretical studies of magnetohydrodynamic (MHD) turbulence and observations of solar wind fluctuations suggest that MHD turbulence in the interstellar medium is anisotropic at small scales, with smooth variations along the background magnetic field and sharp variations perpendicular to the background field. Turbulence with this anisotropy is inefficient at scattering cosmic rays, and thus the scattering rate ν may be smaller than has been traditionally assumed in diffusion models of Galactic cosmic-ray propagation, at least for cosmic-ray energies E above 1011-1012 eV at which self-confinement is not possible. In this paper, it is shown that Galactic cosmic rays can be effectively confined through magnetic reflection by molecular clouds, even when turbulent scattering is weak. Elmegreen's quasi-fractal model of molecular-cloud structure is used to argue that a typical magnetic field line passes through a molecular cloud complex once every ∼300 pc. Once inside the complex, the field line will in most cases be focused into one or more dense clumps in which the magnetic field can be much stronger than the average field in the intercloud medium (ICM). Cosmic rays following field lines into cloud complexes are most often magnetically reflected back into the ICM, since strong-field regions act as magnetic mirrors. For a broad range of cosmic-ray energies, a cosmic ray initially following some particular field line separates from that field line sufficiently slowly that the cosmic ray can be trapped between neighboring cloud complexes for long periods of time. The suppression of cosmic-ray diffusion due to magnetic trapping is calculated in this paper with the use of phenomenological arguments, asymptotic analysis, and Monte Carlo particle simulations. Formulas for the coefficient of diffusion perpendicular to the Galactic disk are derived for several different parameter regimes within the E-ν plane. In one of these parameter regimes in which scattering is weak, it

Stochasticity in the Kepler problem and a model of possible dynamics of comets in the Oort cloud

Energy Technology Data Exchange (ETDEWEB)

Sagdeev, R Z; Zaslavsky, G M

1987-02-11

The orbits of comets from the Oort cloud have eccentricities very close to unity. These orbits are highly elongated which provide one more possibility of their delivery into the planetary zone, besides collisions of comets with stars which are effective near the aphelions. Weak but repetitive perturbations being produced by the great planets, Jupiter and Saturn, on comets with perihelious < 20 AU can cause chaotization of dynamics of comets at orbits with major axes a> or approx.10/sup 3/ AU. A comet may suffer as large as 100/1000 such ''weak'' collisions before it is expelled onto a hyperbolic orbit. The dynamic chaos mechanism provides filling of the loss cone, diffusion of comets from inner parts of the Oort cloud into the outer one (the halo) and fluctuatory comings of comets into the inner part of planetary zone. A diffusive evolution of eccentricity can serve as one of the mechanisms of formation of the Oort cloud. A similar role can be played by both the Galactic gravitational field and periodic perturbations from the hypothetical Sun's companion, Nemesis. The dynamic chaos allows us, along with star encounters, to fill the loss cone in the outer part of the Oort cloud. In the inner part of the Oort cloud the dynamical chaos can be a primary mechanism of the loss cone filling between consecutive rare (although strong) collisions with stars.

A novel enhanced diffusion sampler for collecting gaseous pollutants without air agitation.

Science.gov (United States)

Pan, Xuelian; Zhuo, Shaojie; Zhong, Qirui; Chen, Yuanchen; Du, Wei; Cheng, Hefa; Wang, Xilong; Zeng, Eddy Y; Xing, Baoshan; Tao, Shu

2018-03-06

A novel enhanced diffusion sampler for collecting gaseous phase polycyclic aromatic hydrocarbons (PAHs) without air agitation is proposed. The diffusion of target compounds into a sampling chamber is facilitated by continuously purging through a closed-loop flow to create a large concentration difference between the ambient air and the air in the sampling chamber. A glass-fiber filter-based prototype was developed. It was demonstrated that the device could collect gaseous PAHs at a much higher rate (1.6 ± 1.4 L/min) than regular passive samplers, while the ambient air is not agitated. The prototype was also tested in both the laboratory and field for characterizing the concentration gradients over a short distance from the soil surface. The sampler has potential to be applied in other similar situations to characterize the concentration profiles of other chemicals.

Wire Chamber

CERN Multimedia

Magnetoscriptive readout wire chamber. Multi-wire detectors contain layers of positively and negatively charged wires enclosed in a chamber full of gas. A charged particle passing through the chamber knocks negatively charged electrons out of atoms in the gas, leaving behind positive ions. The electrons are pulled towards the positively charged wires. They collide with other atoms on the way, producing an avalanche of electrons and ions. The movement of these electrons and ions induces an electric pulse in the wires which is collected by fast electronics. The size of the pulse is proportional to the energy loss of the original particle.

Wire chamber

CERN Multimedia

1967-01-01

Magnetoscriptive readout wire chamber.Multi-wire detectors contain layers of positively and negatively charged wires enclosed in a chamber full of gas. A charged particle passing through the chamber knocks negatively charged electrons out of atoms in the gas, leaving behind positive ions. The electrons are pulled towards the positively charged wires. They collide with other atoms on the way, producing an avalanche of electrons and ions. The movement of these electrons and ions induces an electric pulse in the wires which is collected by fast electronics. The size of the pulse is proportional to the energy loss of the original particle.

The diffusion and adoption of a cloud-based enterprise system in Danish municipalities

DEFF Research Database (Denmark)

Fogh Frisenvang, Jakob; Ejerskov Pedersen, Christoffer; Svejvig, Per

2014-01-01

municipalities and the vendor of the Opus solution. We tell the history of Opus and analyze how it has diffused into Danish municipalities. The findings are that the diffusion is strongly influenced by regulative, normative and cultural-cognitive pressures. Institutional processes play an essential part...

First Observation of the Submillimeter Polarization Spectrum in a Translucent Molecular Cloud

Science.gov (United States)

Ashton, Peter C.; Ade, Peter A. R.; Angilè, Francesco E.; Benton, Steven J.; Devlin, Mark J.; Dober, Bradley; Fissel, Laura M.; Fukui, Yasuo; Galitzki, Nicholas; Gandilo, Natalie N.; Klein, Jeffrey; Korotkov, Andrei L.; Li, Zhi-Yun; Martin, Peter G.; Matthews, Tristan G.; Moncelsi, Lorenzo; Nakamura, Fumitaka; Netterfield, Calvin B.; Novak, Giles; Pascale, Enzo; Poidevin, Frédérick; Santos, Fabio P.; Savini, Giorgio; Scott, Douglas; Shariff, Jamil A.; Soler, Juan D.; Thomas, Nicholas E.; Tucker, Carole E.; Tucker, Gregory S.; Ward-Thompson, Derek

2018-04-01

Polarized emission from aligned dust is a crucial tool for studies of magnetism in the ISM, but a troublesome contaminant for studies of cosmic microwave background polarization. In each case, an understanding of the significance of the polarization signal requires well-calibrated physical models of dust grains. Despite decades of progress in theory and observation, polarized dust models remain largely underconstrained. During its 2012 flight, the balloon-borne telescope BLASTPol obtained simultaneous broadband polarimetric maps of a translucent molecular cloud at 250, 350, and 500 μm. Combining these data with polarimetry from the Planck 850 μm band, we have produced a submillimeter polarization spectrum, the first for a cloud of this type. We find the polarization degree to be largely constant across the four bands. This result introduces a new observable with the potential to place strong empirical constraints on ISM dust polarization models in a previously inaccessible density regime. Compared to models by Draine & Fraisse, our result disfavors two of their models for which all polarization arises due only to aligned silicate grains. By creating simple models for polarized emission in a translucent cloud, we verify that extinction within the cloud should have only a small effect on the polarization spectrum shape, compared to the diffuse ISM. Thus, we expect the measured polarization spectrum to be a valid check on diffuse ISM dust models. The general flatness of the observed polarization spectrum suggests a challenge to models where temperature and alignment degree are strongly correlated across major dust components.

STAR FORMATION LAWS: THE EFFECTS OF GAS CLOUD SAMPLING

International Nuclear Information System (INIS)

Calzetti, D.; Liu, G.; Koda, J.

2012-01-01

Recent observational results indicate that the functional shape of the spatially resolved star formation-molecular gas density relation depends on the spatial scale considered. These results may indicate a fundamental role of sampling effects on scales that are typically only a few times larger than those of the largest molecular clouds. To investigate the impact of this effect, we construct simple models for the distribution of molecular clouds in a typical star-forming spiral galaxy and, assuming a power-law relation between star formation rate (SFR) and cloud mass, explore a range of input parameters. We confirm that the slope and the scatter of the simulated SFR-molecular gas surface density relation depend on the size of the sub-galactic region considered, due to stochastic sampling of the molecular cloud mass function, and the effect is larger for steeper relations between SFR and molecular gas. There is a general trend for all slope values to tend to ∼unity for region sizes larger than 1-2 kpc, irrespective of the input SFR-cloud relation. The region size of 1-2 kpc corresponds to the area where the cloud mass function becomes fully sampled. We quantify the effects of selection biases in data tracing the SFR, either as thresholds (i.e., clouds smaller than a given mass value do not form stars) or as backgrounds (e.g., diffuse emission unrelated to current star formation is counted toward the SFR). Apparently discordant observational results are brought into agreement via this simple model, and the comparison of our simulations with data for a few galaxies supports a steep (>1) power-law index between SFR and molecular gas.

Analysis of direct to diffuse partitioning of global solar irradiance at the radiometric station in Badajoz (Spain)

Science.gov (United States)

Sanchez, G.; Cancillo, M. L.; Serrano, A.

2010-09-01

This study is aimed at the analysis of the partitioning of global solar irradiance into its direct and diffuse components at the radiometric station in Badajoz (Spain). The detailed knowledge of the solar radiation field is of increasing interest in Southern Europe due to its use as renewable energy. In particular, the knowledge of the solar radiation partitioning into direct and diffuse radiation has become a major demand for the design and suitable orientation of solar panels in solar power plants. In this study the first measurements of solar diffuse irradiance performed in the radiometric station in Badajoz (Spain) are presented and analyzed in the framework of the partitioning of solar global radiation. Thus, solar global and diffuse irradiance were measured at one-minute basis from 23 November 2009 to 31 March 2010. Solar irradiances were measured by two Kipp&Zonen CMP11 pyranometers, using a Kipp&Zonen CM121 shadow ring for the measurements of solar diffuse irradiance. Diffuse measurements were corrected from the solid angle hidden by the ring and direct irradiance was calculated as the difference between global and diffuse measurements. Irradiance was obtained from the pyranomenters by applying calibration coefficients obtained in an inter-comparison campaign performed at INTA/El Arenosillo, in Huelva (Spain), last September 2009. There, calibration coefficients were calculated using as a reference a CMP11 pyranometer which had been previously calibrated by the Physikalisch-Meteorologisches Observatorium Davos/World Radiation Centre in Switzerland. In order to study the partitioning of the solar radiation, the global and diffuse irradiances have been analyzed for three typical different sky conditions: cloud-free, broken clouds and overcast. Particular days within the period of study have been selected by visual inspection. Along with the analysis of the global and diffuse irradiances themselves, ratios of these irradiances to the downward irradiance at the

Disk and circumsolar radiances in the presence of ice clouds

Directory of Open Access Journals (Sweden)

P. Haapanala

2017-06-01

Full Text Available The impact of ice clouds on solar disk and circumsolar radiances is investigated using a Monte Carlo radiative transfer model. The monochromatic direct and diffuse radiances are simulated at angles of 0 to 8° from the center of the sun. Input data for the model are derived from measurements conducted during the 2010 Small Particles in Cirrus (SPARTICUS campaign together with state-of-the-art databases of optical properties of ice crystals and aerosols. For selected cases, the simulated radiances are compared with ground-based radiance measurements obtained by the Sun and Aureole Measurements (SAM instrument. First, the sensitivity of the radiances to the ice cloud properties and aerosol optical thickness is addressed. The angular dependence of the disk and circumsolar radiances is found to be most sensitive to assumptions about ice crystal roughness (or, more generally, non-ideal features of ice crystals and size distribution, with ice crystal habit playing a somewhat smaller role. Second, in comparisons with SAM data, the ice cloud optical thickness is adjusted for each case so that the simulated radiances agree closely (i.e., within 3 % with the measured disk radiances. Circumsolar radiances at angles larger than ≈ 3° are systematically underestimated when assuming smooth ice crystals, whereas the agreement with the measurements is better when rough ice crystals are assumed. Our results suggest that it may well be possible to infer the particle roughness directly from ground-based SAM measurements. In addition, the results show the necessity of correcting the ground-based measurements of direct radiation for the presence of diffuse radiation in the instrument's field of view, in particular in the presence of ice clouds.

Ionization chambers

International Nuclear Information System (INIS)

Boag, J.W.

1987-01-01

Although a variety of solid-state and chemical methods for measuring radiation dose have been developed in recent decades and calorimetry can now provide an absolute standard of reference, ionization dosimetry retains its position as the most widely used, most convenient, and, in most situations, most accurate method of measuring either exposure or absorbed dose. The ionization chamber itself is the central element in this system of dosimetry. In this chapter the principles governing the construction and operation of ionization chambers of various types are examined. Since the ionization chambers now in general use are nearly all of commercial manufacture, the emphasis is on operating characteristics and interpretation of measurements rather than on details of construction, although some knowledge of the latter is often required when applying necessary corrections to the measured quantities. Examples are given of the construction of typical chambers designed for particular purposes, and the methods of calibrating them are discussed

Deposition and Characterization of the Titanium-Based Coating by a Multi-Chamber Detonation Sprayer

Directory of Open Access Journals (Sweden)

Arseenko M.Yu.

2015-01-01

Full Text Available This work introduces some of the aspects of the deposition of titanium-based coating (80-120 μm thick on aluminium samples using a multi-chamber detonation sprayer (MCDS. The characteristic feature of MCDS is that the powder is accelerated by using combustion products that are formed in MCDS chambers and are converged before entering the nozzle, where they interact with the two-phase gas-powder cloud. The microstructures and properties of the coating were characterized with the use of scanning electronic microscopes (SEM, optical microscope (OM, X-ray Diffraction (XRD techniques, and Vickers hardness tester with a 50 g test load. Wear tests were carried out using a computer controlled pin-on-disc type tribometer. It was established that MCDS has provided the conditions for formation of a dense titanium-based coating with a porosity of less than 1.0%, microhardness 810±250 HV0.05 and a specific wear rate of 2.077∙10-4 mm3(m∙N-1.

A diffusivity model for predicting VOC diffusion in porous building materials based on fractal theory

International Nuclear Information System (INIS)

Liu, Yanfeng; Zhou, Xiaojun; Wang, Dengjia; Song, Cong; Liu, Jiaping

2015-01-01

Highlights: • Fractal theory is introduced into the prediction of VOC diffusion coefficient. • MSFC model of the diffusion coefficient is developed for porous building materials. • The MSFC model contains detailed pore structure parameters. • The accuracy of the MSFC model is verified by independent experiments. - Abstract: Most building materials are porous media, and the internal diffusion coefficients of such materials have an important influences on the emission characteristics of volatile organic compounds (VOCs). The pore structure of porous building materials has a significant impact on the diffusion coefficient. However, the complex structural characteristics bring great difficulties to the model development. The existing prediction models of the diffusion coefficient are flawed and need to be improved. Using scanning electron microscope (SEM) observations and mercury intrusion porosimetry (MIP) tests of typical porous building materials, this study developed a new diffusivity model: the multistage series-connection fractal capillary-bundle (MSFC) model. The model considers the variable-diameter capillaries formed by macropores connected in series as the main mass transfer paths, and the diameter distribution of the capillary bundles obeys a fractal power law in the cross section. In addition, the tortuosity of the macrocapillary segments with different diameters is obtained by the fractal theory. Mesopores serve as the connections between the macrocapillary segments rather than as the main mass transfer paths. The theoretical results obtained using the MSFC model yielded a highly accurate prediction of the diffusion coefficients and were in a good agreement with the VOC concentration measurements in the environmental test chamber.

The Drift Chambers Handbook, introductory laboratory course (based on, and adapted from, A H Walenta's course notes)

International Nuclear Information System (INIS)

Ferreira, Ix-B GarcIa; Herrera, J GarcIa; Villasenor, L

2005-01-01

This handbook was written for the Drift Chambers introductory laboratory course to be held at 11th Mexican School of Particles and Fields that will be held at the Universidad Veracruzana on the campus of the University at Xalapa, Veracruz, Mexico. This course intends to introduce drift chambers, which play an important role in particle physics experiments as tracking detectors. We start such laboratory course with a brief review of the physics theoretical background. The experimental setup consists of a single-sided, single-cell drift chamber, a plastic scintillator detector, the standard P-10 gas mixture (90% Ar, 10% CH 4 ) and a collimated 90 Sr source. The measurements on the drift velocity of electrons, its change as a function of a drift field, gas gain and diffusion are performed at this laboratory course

Time evolution of artificial plasma cloud in atmospheric environment

International Nuclear Information System (INIS)

Lu Qiming; Yang Weihong; Liu Wandong

2004-01-01

By analyzing the time evolution of artificial plasma cloud in the high altitude of atmospheric environment, the authors found that there are two zones, an exponential attenuation zone and a linearly attenuating zone, existing in the spatial distribution of electron density of the artificial plasma clouds. The plasma generator's particle flux density only contributes to the exponential attenuation zone, and has no effect on the linear attenuation zone. The average electron density in the linear attenuation zone is about 10 -5 of neutral particle density, and can diffuse over a wider area. The conclusion will supply some valuable references to the research of electromagnetic wave and artificial plasma interaction, the plasma invisibleness research of missile and special aerocraft, and the design of artificial plasma source. (authors)

Gas microstrip chambers

International Nuclear Information System (INIS)

McIntyre, P.M.; Barasch, E.F.; Bowcock, T.J.V.; Demroff, H.P.; Elliott, S.M.; Howe, M.R.; Lee, B.; Mazumdar, T.K.; Pang, Y.; Smith, D.D.; Wahl, J.; Wu, Y.; Yue, W.K.; Gaedke, R.M.; Vanstraelen, G.

1992-01-01

The gas microstrip chamber has been developed from concept to experimental system during the past three years. A pattern of anode and grid lines are microfabricated onto a dielectric substrate and configured as a high-resolution MWPC. Four recent developments are described: Suitable plastic substrates and lithography techniques for large-area chambers; non-planar silicon-based chambers for 20 μm resolution; integrated on-board synchronous front-end electronics and data buffering; and a porous silicon active cathode for enhanced efficiency and time response. The microstrip chamber appears to be a promising technology for applications in microvertex, tracking spectrometer, muon spectrometer, and transition radiation detection. (orig.)

Production and transport chemistry of atomic fluorine in remote plasma source and cylindrical reaction chamber

International Nuclear Information System (INIS)

Gangoli, S P; Johnson, A D; Fridman, A A; Pearce, R V; Gutsol, A F; Dolgopolsky, A

2007-01-01

Increasingly, NF 3 -based plasmas are being used in semiconductor manufacturing to clean chemical vapour deposition (CVD) chambers. With advantages such as faster clean times, substantially lower emissions of gases having high global warming potentials, and reduced chamber damage, NF 3 plasmas are now favoured over fluorocarbon-based processes. Typically, a remote plasma source (RPS) is used to dissociate the NF 3 gas and produce atomic fluorine that etches the CVD residues from the chamber surfaces. However, it is important to efficiently transport F atoms from the plasma source into the process chamber. The current work is aimed at understanding and improving the key processes involved in the production and transport of atomic fluorine atoms. A zero-dimensional model of NF 3 dissociation and F production chemistry in the RPS is developed based on various known and derived plasma parameters. Additionally, a model describing the transport of atomic fluorine is proposed that includes both physical (diffusion, adsorption and desorption) and chemical processes (surface and three-body volume recombination). The kinetic model provides an understanding of the impact of chamber geometry, gas flow rates, pressure and temperature on fluorine recombination. The plasma-kinetic model is validated by comparing model predictions (percentage F atom density) with experimental results (etch rates)

Simulation study of electron cloud induced instabilities and emittance growth for the CERN Large Hadron Collider proton beam

CERN Document Server

Benedetto, Elena; Schulte, Daniel; Rumolo, Giovanni

2005-01-01

The electron cloud may cause transverse single-bunch instabilities of proton beams such as those in the Large Hadron Collider (LHC) and the CERN Super Proton Synchrotron (SPS). We simulate these instabilities and the consequent emittance growth with the code HEADTAIL, which models the turn-by-turn interaction between the cloud and the beam. Recently some new features were added to the code, in particular, electric conducting boundary conditions at the chamber wall, transverse feedback, and variable beta functions. The sensitivity to several numerical parameters has been studied by varying the number of interaction points between the bunch and the cloud, the phase advance between them, and the number of macroparticles used to represent the protons and the electrons. We present simulation results for both LHC at injection and SPS with LHC-type beam, for different electron-cloud density levels, chromaticities, and bunch intensities. Two regimes with qualitatively different emittance growth are observed: above th...

MOLECULAR CLOUD CHEMISTRY AND THE IMPORTANCE OF DIELECTRONIC RECOMBINATION

International Nuclear Information System (INIS)

Bryans, P.; Kreckel, H.; Savin, D. W.; Roueff, E.; Wakelam, V.

2009-01-01

Dielectronic recombination (DR) of singly charged ions is a reaction pathway that is commonly neglected in chemical models of molecular clouds. In this study we include state-of-the-art DR data for He + , C + , N + , O + , Na + , and Mg + in chemical models used to simulate dense molecular clouds, protostars, and diffuse molecular clouds. We also update the radiative recombination (RR) rate coefficients for H + , He + , C + , N + , O + , Na + , and Mg + to the current state-of-the-art values. The new RR data have little effect on the models. However, the inclusion of DR results in significant differences in gas-grain models of dense, cold molecular clouds for the evolution of a number of surface and gas-phase species. We find differences of a factor of 2 in the abundance for 74 of the 655 species at times of 10 4 -10 6 yr in this model when we include DR. Of these 74 species, 16 have at least a factor of 10 difference in abundance. We find the largest differences for species formed on the surface of dust grains. These differences are due primarily to the addition of C + DR, which increases the neutral C abundance, thereby enhancing the accretion of C onto dust. These results may be important for the warm-up phase of molecular clouds when surface species are desorbed into the gas phase. We also note that no reliable state-of-the-art RR or DR data exist for Si + , P + , S + , Cl + , and Fe + . Modern calculations for these ions are needed to better constrain molecular cloud models.

Double chamber ion source

International Nuclear Information System (INIS)

Uman, M.F.; Winnard, J.R.; Winters, H.F.

1978-01-01

The ion source is comprised of two discharge chambers one of which is provided with a filament and an aperture leading into the other chamber which in turn has an extraction orifice. A low voltage arc discharge is operated in an inert gas atmosphere in the filament chamber while an arc of higher voltage is operated in the second ionization chamber which contains a vapor which will give the desired dopant ion species. The entire source is immersed in an axial magnetic field parallel to a line connecting the filament, the aperture between the two chambers and the extraction orifice. (author)

Ussing Chamber

NARCIS (Netherlands)

Westerhout, J.; Wortelboer, H.; Verhoeckx, K.

2015-01-01

The Ussing chamber system is named after the Danish zoologist Hans Ussing, who invented the device in the 1950s to measure the short-circuit current as an indicator of net ion transport taking place across frog skin (Ussing and Zerahn, Acta Physiol Scand 23:110-127, 1951). Ussing chambers are

DELPHI Barrel Muon Chamber Module

CERN Multimedia

1989-01-01

The module was used as part of the muon identification system on the barrel of the DELPHI detector at LEP, and was in active use from 1989 to 2000. The module consists of 7 individual muons chambers arranged in 2 layers. Chambers in the upper layer are staggered by half a chamber width with respect to the lower layer. Each individual chamber is a drift chamber consisting of an anode wire, 47 microns in diameter, and a wrapped copper delay line. Each chamber provided 3 signal for each muon passing through the chamber, from which a 3D space-point could be reconstructed.

Star-Forming Clouds Feed, Churn, and Fall

Science.gov (United States)

Kohler, Susanna

2017-12-01

Molecular clouds, the birthplaces of stars in galaxies throughout the universe, are complicated and dynamic environments. A new series of simulations has explored how these clouds form, grow, and collapse over their lifetimes.This composite image shows part of the Taurus Molecular Cloud. [ESO/APEX (MPIfR/ESO/OSO)/A. Hacar et al./Digitized Sky Survey]Stellar BirthplacesMolecular clouds form out of the matter in between stars, evolving through constant interactions with their turbulent environments. These interactions taking the form of accretion flows and surface forces, while gravity, turbulence, and magnetic fields interplay are thought to drive the properties and evolution of the clouds.Our understanding of the details of this process, however, remains fuzzy. How does mass accretion affect these clouds as they evolve? What happens when nearby supernova explosions blast the outsides of the clouds? What makes the clouds churn, producing the motion within them that prevents them from collapsing? The answers to these questions can tellus about the gas distributed throughout galaxies, revealing information about the environments in which stars form.A still from the simulation results showing the broader population of molecular clouds that formed in the authors simulations, as well as zoom-in panels of three low-mass clouds tracked in high resolution. [Ibez-Meja et al. 2017]Models of TurbulenceIn a new study led by Juan Ibez-Meja (MPI Garching and Universities of Heidelberg and Cologne in Germany, and American Museum of Natural History), scientists have now explored these questions using a series of three-dimensional simulations of a population of molecular clouds forming and evolving in the turbulent interstellar medium.The simulations take into account a whole host of physics, including the effects of nearby supernova explosions, self-gravitation, magnetic fields, diffuse heating, and radiative cooling. After looking at the behavior of the broader population of

Design of new dusty plasma apparatus to view 3D particle dynamics of fluorescent dust clouds

Science.gov (United States)

Thome, Kathreen; Fontanetta, Alexandra; Zwicker, Andrew

2008-11-01

Particles suspended in dusty plasmas represent both contamination in industrial plasmas and a primary interstellar medium component. Typically, dusty plasma behavior is studied by laser scattering techniques that provide 2D dust cloud images. However, the 3D structure of the dust cloud is essential to understand the waves, group dynamics, and stabilities of the cloud. Techniques used to study this structure include stereoscopic particle image velocimetry and rapid laser scanning. Our UV illumination technique reveals translational and rotational velocities of fluorescent dust particles as a function of UV intensity. The new argon DC glow discharge experiment designed to study the 3D aspects of fluorescent dust consists of a 13.25'' diameter chamber, two 8'' window ports for CCD cameras, one along the plasma and another transverse to it, two additional 8'' window ports transverse to the plasma for laser or UV light illumination of the dust cloud, and a diagnostic probe port. Results from different electrodes--including mesh and ring--observations and imaging will be presented.

Stratocumulus Cloud Top Radiative Cooling and Cloud Base Updraft Speeds

Science.gov (United States)

Kazil, J.; Feingold, G.; Balsells, J.; Klinger, C.

2017-12-01

Cloud top radiative cooling is a primary driver of turbulence in the stratocumulus-topped marine boundary. A functional relationship between cloud top cooling and cloud base updraft speeds may therefore exist. A correlation of cloud top radiative cooling and cloud base updraft speeds has been recently identified empirically, providing a basis for satellite retrieval of cloud base updraft speeds. Such retrievals may enable analysis of aerosol-cloud interactions using satellite observations: Updraft speeds at cloud base co-determine supersaturation and therefore the activation of cloud condensation nuclei, which in turn co-determine cloud properties and precipitation formation. We use large eddy simulation and an off-line radiative transfer model to explore the relationship between cloud-top radiative cooling and cloud base updraft speeds in a marine stratocumulus cloud over the course of the diurnal cycle. We find that during daytime, at low cloud water path (CWP correlated, in agreement with the reported empirical relationship. During the night, in the absence of short-wave heating, CWP builds up (CWP > 50 g m-2) and long-wave emissions from cloud top saturate, while cloud base heating increases. In combination, cloud top cooling and cloud base updrafts become weakly anti-correlated. A functional relationship between cloud top cooling and cloud base updraft speed can hence be expected for stratocumulus clouds with a sufficiently low CWP and sub-saturated long-wave emissions, in particular during daytime. At higher CWPs, in particular at night, the relationship breaks down due to saturation of long-wave emissions from cloud top.

Cloud networking understanding cloud-based data center networks

CERN Document Server

Lee, Gary

2014-01-01

Cloud Networking: Understanding Cloud-Based Data Center Networks explains the evolution of established networking technologies into distributed, cloud-based networks. Starting with an overview of cloud technologies, the book explains how cloud data center networks leverage distributed systems for network virtualization, storage networking, and software-defined networking. The author offers insider perspective to key components that make a cloud network possible such as switch fabric technology and data center networking standards. The final chapters look ahead to developments in architectures

Portable mini-chamber for temperature dependent studies using small angle and wide angle x-ray scattering

Science.gov (United States)

Dev, Arun Singh; Kumar, Dileep; Potdar, Satish; Pandit, Pallavi; Roth, Stephan V.; Gupta, Ajay

2018-04-01

The present work describes the design and performance of a vacuum compatible portable mini chamber for temperature dependent GISAXS and GIWAXS studies of thin films and multilayer structures. The water cooled body of the chamber allows sample annealing up to 900 K using ultra high vacuum compatible (UHV) pyrolytic boron nitride heater, thus making it possible to study the temperature dependent evolution of structure and morphology of two-dimensional nanostructured materials. Due to its light weight and small size, the chamber is portable and can be accommodated at synchrotron facilities worldwide. A systematic illustration of the versatility of the chamber has been demonstrated at beamline P03, PETRA-III, DESY, Hamburg, Germany. Temperature dependent grazing incidence small angle x-ray scattering (GISAXS) and grazing incidence wide angle x-ray scattering (GIWAXS) measurements were performed on oblique angle deposited Co/Ag multilayer structure, which jointly revealed that the surface diffusion in Co columns in Co/Ag multilayer enhances by increasing temperature from RT to ˜573 K. This results in a morphology change from columnar tilted structure to densely packed morphological isotropic multilayer.

A new type of coating to chase the clouds away

CERN Multimedia

Stefania Pandolfi

2016-01-01

The electron cloud problem needs to be addressed with innovative solutions, particularly in view of the rapidly approaching HL-LHC upgrade. CERN’s Vacuum, Surfaces and Coatings group has greatly improved its amorphous carbon coating technique, which is an alternative to the scrubbing process used so far. This technique is now fully mature and is being used for the vacuum chambers of the SPS magnets and the delicate beam screens of the LHC’s quadrupole triplets.   The violet light is produced by the argon plasma used when sputtering the amorphous carbon. The beam screen is coated in this case using the magnetic field of the quadrupole itself. (Image: Pedro Costa Pinto) We know that conditioning (or “scrubbing”) the beam pipe reduces the avalanche-like creation of secondary electrons from the tube’s walls, thus preventing the formation of unwanted electron clouds. But it has also been observed that scrubbing natur...

Gridded ionization chamber

International Nuclear Information System (INIS)

Houston, J.M.

1977-01-01

An improved ionization chamber type x-ray detector comprises a heavy gas at high pressure disposed between an anode and a cathode. An open grid structure is disposed adjacent the anode and is maintained at a voltsge intermediate between the cathode and anode potentials. The electric field which is produced by positive ions drifting toward the cathode is thus shielded from the anode. Current measuring circuits connected to the anode are, therefore, responsive only to electron current flow within the chamber and the recovery time of the chamber is shortened. The grid structure also serves to shield the anode from electrical currents which might otherwise be induced by mechanical vibrations in the ionization chamber structure

Culture of normal human blood cells in diffusion chamber systems. I. Granulocyte survival and proliferation. [X radiation, mice

Energy Technology Data Exchange (ETDEWEB)

Chikkappa, G.; Carsten, A.L.; Chanana, A.D.; Cronkite, E.P.

1978-01-01

Blood cells from four normal volunteers were cultured in diffusion chambers (DC), made of Millipore (MDC) or Nuclepore (NDC) filters, in the peritoneal cavities of whole body X-irradiated (700 rad) mice. The total nucleated cell recovery from the two types of DC over 18 days indicates that the cells in DC persist and proliferate. The mature neutrophilic cells, metamyelocytes (M/sub 5/) + band forms (M/sub 6/) + segmented forms (M/sub 7/), survived with T/sup 1///sub 2/ of 29 and 34 h in MDC and NDC, respectively. The reduction of the cells in the DC was surmised to be due to degeneration and death of the M/sub 7/. The /sup 3/H-diisopropylfluorophosphate (/sup 3/HDFP) labeled M/sub /sub 6/+/sub 7// survival in MDC was slightly shorter than that of unlabeled cells, which may be explained on the basis of the loss of /sup 3/HDFP (5.1%/day) from the cells. The eosinophils survived with an average T/sup 1///sub 2/ of 7.2 days (range 4.8 to 9.6), and the results were comparable in both types of DC. Formation of myeloblasts, promyelocytes, and neutrophilic, eosinophilic and basophilic myelocytes, occasional megakaryocytes and rare normoblasts in DC indicated that the normal human blood contains progenitors (pluripotent and/or committed stem cells) of hemopoietic cells. The neutrophilic cell recovery pattern was similar from both types of DC, but the total number recovered was always greater from NDC than from MDC.

A flux-limited treatment for the conductive evaporation of spherical interstellar gas clouds

Science.gov (United States)

Dalton, William W.; Balbus, Steven A.

1993-01-01

In this work, we present and analyze a new analytic solution for the saturated (flux-limited) thermal evaporation of a spherical cloud. This work is distinguished from earlier analytic studies by allowing the thermal conductivity to change continuously from a diffusive to a saturated form, in a manner usually employed only in numerical calculations. This closed form solution will be of interest as a computational benchmark. Using our calculated temperature profiles and mass-loss rates, we model the thermal evaporation of such a cloud under typical interstellar medium (ISM) conditions, with some restrictions. We examine the ionization structure of the cloud-ISM interface and evaluate column densities of carbon, nitrogen, oxygen, neon, and silicon ions toward the cloud. In accord with other investigations, we find that ionization equilibrium is far from satisfied under the assumed conditions. Since the inclusion of saturation effects in the heat flux narrows the thermal interface relative to its classical structure, we also find that saturation effects tend to lower predicted column densities.

Formation of giant molecular clouds in global spiral structures: the role of orbital dynamics and cloud-cloud collisions

International Nuclear Information System (INIS)

Roberts, W.W. Jr.; Stewart, G.R.

1987-01-01

The different roles played by orbital dynamics and dissipative cloud-cloud collisions in the formation of giant molecular clouds (GMCs) in a global spiral structure are investigated. The interstellar medium (ISM) is simulated by a system of particles, representing clouds, which orbit in a spiral-perturbed, galactic gravitational field. The overall magnitude and width of the global cloud density distribution in spiral arms is very similar in the collisional and collisionless simulations. The results suggest that the assumed number density and size distribution of clouds and the details of individual cloud-cloud collisions have relatively little effect on these features. Dissipative cloud-cloud collisions play an important steadying role for the cloud system's global spiral structure. Dissipative cloud-cloud collisions also damp the relative velocity dispersion of clouds in massive associations and thereby aid in the effective assembling of GMC-like complexes

Evaluation of Passive Multilayer Cloud Detection Using Preliminary CloudSat and CALIPSO Cloud Profiles

Science.gov (United States)

Minnis, P.; Sun-Mack, S.; Chang, F.; Huang, J.; Nguyen, L.; Ayers, J. K.; Spangenberg, D. A.; Yi, Y.; Trepte, C. R.

2006-12-01

During the last few years, several algorithms have been developed to detect and retrieve multilayered clouds using passive satellite data. Assessing these techniques has been difficult due to the need for active sensors such as cloud radars and lidars that can "see" through different layers of clouds. Such sensors have been available only at a few surface sites and on aircraft during field programs. With the launch of the CALIPSO and CloudSat satellites on April 28, 2006, it is now possible to observe multilayered systems all over the globe using collocated cloud radar and lidar data. As part of the A- Train, these new active sensors are also matched in time ad space with passive measurements from the Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) and Advanced Microwave Scanning Radiometer - EOS (AMSR-E). The Clouds and the Earth's Radiant Energy System (CERES) has been developing and testing algorithms to detect ice-over-water overlapping cloud systems and to retrieve the cloud liquid path (LWP) and ice water path (IWP) for those systems. One technique uses a combination of the CERES cloud retrieval algorithm applied to MODIS data and a microwave retrieval method applied to AMSR-E data. The combination of a CO2-slicing cloud retireval technique with the CERES algorithms applied to MODIS data (Chang et al., 2005) is used to detect and analyze such overlapped systems that contain thin ice clouds. A third technique uses brightness temperature differences and the CERES algorithms to detect similar overlapped methods. This paper uses preliminary CloudSat and CALIPSO data to begin a global scale assessment of these different methods. The long-term goals are to assess and refine the algorithms to aid the development of an optimal combination of the techniques to better monitor ice 9and liquid water clouds in overlapped conditions.

Investigation of Shock Diffusers at Mach Number 1.85. 1 - Projecting Single Shock Cones

Science.gov (United States)

1947-06-17

cylindrical simulated combustion chamber was used to vary the outlet area of the flow through the diffuser. The pitot -static rake, located as shown in the...and II. Proc. Roy. Soc. (London), ser. A, vol. 139, no 838, Feb. 1, 1933, pp. 278-311. 5. Wyatt, DeMarquis D., and Hunczak, Henry R.: An...Simulated combustion u chamber A 90° W •—Conical damper S Static-pressure orifice ps pitot -static ""rake’ NATIONAL ADVISORY

Ice nucleating particles measured during the laboratory and field intercomparisons FIN-2 and FIN-3 by the diffusion chamber FRIDGE

Science.gov (United States)

Weber, Daniel; Schrod, Jann; Curtius, Joachim; Haunold, Werner; Thomson, Erik; Bingemer, Heinz

2016-04-01

The measurement of atmospheric ice nucleating particles (INP) is still challenging. In the absence of easily applicable INP standards the intercomparison of different methods during collaborative laboratory and field workshops is a valuable tool that can shine light on the performance of individual methods for the measurement of INP [1]. FIN-2 was conducted in March 2015 at the AIDA facility in Karlsruhe as an intercomparison of mobile instruments for measuring INP [2]. FIN-3 was a field campaign at the Desert Research Institutes Storm Peak Laboratory in Colorado in September 2015 [3]. The FRankfurt Ice nucleation Deposition freezinG Experiment (FRIDGE) participated in both experiments. FRIDGE measures ice nucleating particles by electrostatic precipitation of aerosol particles onto Si-wafers in a collection unit, followed by activation, growth, and optical detection of ice crystals on the substrate in an isostatic diffusion chamber [4,5]. We will present and discuss results of our measurements of deposition/condensation INP and of immersion INP with FRIDGE during FIN-2 and FIN-3. Acknowledgements: The valuable contributions of the FIN organizers and their institutions, and of the FIN Workshop Science team are gratefully acknowledged. Our work was supported by Deutsche Forschungsgemeinschaft (DFG) under the Research Unit FOR 1525 (INUIT) and the EU FP7-ENV- 2013 BACCHUS project under Grant Agreement 603445.

Cloud Computing Fundamentals

Science.gov (United States)

Furht, Borko

In the introductory chapter we define the concept of cloud computing and cloud services, and we introduce layers and types of cloud computing. We discuss the differences between cloud computing and cloud services. New technologies that enabled cloud computing are presented next. We also discuss cloud computing features, standards, and security issues. We introduce the key cloud computing platforms, their vendors, and their offerings. We discuss cloud computing challenges and the future of cloud computing.

Diffusion of [2-14C]diazepam across hairless mouse skin and human skin

International Nuclear Information System (INIS)

Koch, R.L.; Palicharla, P.; Groves, M.J.

1987-01-01

The objectives of this study were to investigate the absorption of diazepam applied topically to the hairless mouse in vivo and to determine the diffusion of diazepam across isolated hairless mouse skin and human skin. [ 14 C]Diazepam was readily absorbed after topical administration to the intact hairless mouse, a total of 75.8% of the 14 C-label applied being recovered in urine and feces. Diazepam was found to diffuse across human and hairless mouse skin unchanged in experiments with twin-chambered diffusion cells. The variation in diffusion rate or the flux for both human and mouse tissues was greater among specimens than between duplicate or triplicate trials for a single specimen. Fluxes for mouse skin (stratum corneum, epidermis, and dermis) were greater than for human skin (stratum corneum and epidermis): 0.35-0.61 microgram/cm2/h for mouse skin vs 0.24-0.42 microgram/cm2/h for human skin. The permeability coefficients for mouse skin ranged from 1.4-2.4 X 10(-2)cm/h compared with 0.8-1.4 X 10(-2)cm/h for human skin. Although human stratum corneum is almost twice the thickness of that of the hairless mouse, the diffusion coefficients for human skin were 3-12 times greater (0.76-3.31 X 10(-6) cm2/h for human skin vs 0.12-0.27 X 10(-6) cm2/h for hairless mouse) because of a shorter lag time for diffusion across human skin. These differences between the diffusion coefficients and diffusion rates (or permeability coefficients) suggest that the presence of the dermis may present some barrier properties. In vitro the dermis may require complete saturation before the diazepam can be detected in the receiving chamber

Carbon chemistry in dense molecular clouds: Theory and observational constraints

International Nuclear Information System (INIS)

Blake, G.A.

1990-01-01

For the most part, gas phase models of the chemistry of dense molecular clouds predict the abundances of simple species rather well. However, for larger molecules and even for small systems rich in carbon these models often fail spectacularly. Researchers present a brief review of the basic assumptions and results of large scale modeling of the carbon chemistry in dense molecular clouds. Particular attention is to the influence of the gas phase C/O ratio in molecular clouds, and the likely role grains play in maintaining this ratio as clouds evolve from initially diffuse objects to denser cores with associated stellar and planetary formation. Recent spectral line surveys at centimeter and millimeter wavelengths along with selected observations in the submillimeter have now produced an accurate inventory of the gas phase carbon budget in several different types of molecular clouds, though gaps in our knowledge clearly remain. The constraints these observations place on theoretical models of interstellar chemistry can be used to gain insights into why the models fail, and show also which neglected processes must be included in more complete analyses. Looking toward the future, larger molecules are especially difficult to study both experimentally and theoretically in such dense, cold regions, and some new methods are therefore outlined which may ultimately push the detectability of small carbon chains and rings to much heavier species

Diffusive-to-ballistic transition of the modulated heat transport in a rarefied air chamber

Science.gov (United States)

Gomez-Heredia, C. L.; Macias, J.; Ordonez-Miranda, J.; Ares, O.; Alvarado-Gil, J. J.

2017-01-01

Modulated heat transfer in air subject to pressures from 760 Torr to 10-4 Torr is experimentally studied by means of a thermal-wave resonant cavity placed in a vacuum chamber. This is done through the analysis of the amplitude and phase delay of the photothermal signal as a function of the cavity length and pressure through of the Knudsen's number. The viscous, transitional, and free molecular regimes of heat transport are observed for pressures P>1.5 Torr, 25 mTorrheat transport.

The VLT-FLAMES Tarantula Survey. IX. The interstellar medium seen through diffuse interstellar bands and neutral sodium

NARCIS (Netherlands)

van Loon, J.Th.; Bailey, M.; Tatton, B.L.; Maíz Apellániz, J.; Crowther, P.A.; de Koter, A.; Evans, C.J.; Hénault-Brunet, V.; Howarth, I.D.; Richter, P.; Sana, H.; Simón-Díaz, S.; Taylor, W.; Walborn, N.R.

2013-01-01

Context. The Tarantula Nebula (a.k.a. 30 Dor) is a spectacular star-forming region in the Large Magellanic Cloud (LMC), seen through gas in the Galactic disc and halo. Diffuse interstellar bands (DIBs) offer a unique probe of the diffuse, cool-warm gas in these regions. Aims. The aim is to use DIBs

Relationships among cloud occurrence frequency, overlap, and effective thickness derived from CALIPSO and CloudSat merged cloud vertical profiles

Science.gov (United States)

Kato, Seiji; Sun-Mack, Sunny; Miller, Walter F.; Rose, Fred G.; Chen, Yan; Minnis, Patrick; Wielicki, Bruce A.

2010-01-01

A cloud frequency of occurrence matrix is generated using merged cloud vertical profiles derived from the satellite-borne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and cloud profiling radar. The matrix contains vertical profiles of cloud occurrence frequency as a function of the uppermost cloud top. It is shown that the cloud fraction and uppermost cloud top vertical profiles can be related by a cloud overlap matrix when the correlation length of cloud occurrence, which is interpreted as an effective cloud thickness, is introduced. The underlying assumption in establishing the above relation is that cloud overlap approaches random overlap with increasing distance separating cloud layers and that the probability of deviating from random overlap decreases exponentially with distance. One month of Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and CloudSat data (July 2006) support these assumptions, although the correlation length sometimes increases with separation distance when the cloud top height is large. The data also show that the correlation length depends on cloud top hight and the maximum occurs when the cloud top height is 8 to 10 km. The cloud correlation length is equivalent to the decorrelation distance introduced by Hogan and Illingworth (2000) when cloud fractions of both layers in a two-cloud layer system are the same. The simple relationships derived in this study can be used to estimate the top-of-atmosphere irradiance difference caused by cloud fraction, uppermost cloud top, and cloud thickness vertical profile differences.

ROSAT view of the ISM in the Large Magellanic Cloud

Science.gov (United States)

Chu, You-Hua

1996-01-01

Rosat observations of the Large Magellanic Cloud (LMC) show a large scale unbounded diffuse X-ray emission, as well as an enhanced emission within large shell structures. These observations allow the distribution of hot ionized medium in the LMC to be examined. Moreover, the hot interior of supernova shells and superbubbles, supernova remnants and the multi-phase structure of the interstellar medium (ISM) can be investigated.

Sources, Composition, and Properties of Newly Formed and Regional Organic Aerosol in a Boreal Forest during the Biogenic Aerosol: Effects on Clouds and Climate Field Campaign Report

Energy Technology Data Exchange (ETDEWEB)

Thornton, Joel [Univ. of Washington, Seattle, WA (United States)

2016-05-01

The Thornton Laboratory participated in the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility’s Biogenic Aerosol Effects on Clouds and Climate (BAECC) campaign in Finland by deploying our mass spectrometer. We then participated in environmental simulation chamber studies at Pacific Northwest National Laboratory (PNNL). Thereafter, we analyzed the results as demonstrated in the several presentations and publications. The field campaign and initial environmental chamber studies are described below.

Development of a Time Projection Chamber using CF4 gas for relativistic heavy ion experiments

International Nuclear Information System (INIS)

Isobe, T.; Hamagaki, H.; Ozawa, K.; Inuzuka, M.; Sakaguchi, T.; Matsumoto, T.; Kametani, S.; Kajihara, F.; Gunji, T.; Kurihara, N.; Oda, S.X.; Yamaguchi, Y.L.

2006-01-01

A prototype Time Projection Chamber (TPC) using pure CF 4 gas was developed for possible use in heavy ion experiments. Basic characteristics such as gain, drift velocity, longitudinal diffusion and attenuation length of produced electrons were measured with the TPC. At an electric field of 900V/cm, the drift velocity and longitudinal diffusion for 1cm drift were obtained as 10cm/μs and 60μm, respectively. The relatively large gain fluctuation is explained to be due to the electron attachment process in CF 4 . These characteristics are encouraging for the measurement of the charged particle trajectories under high multiplicity conditions at RHIC

Clustering, randomness, and regularity in cloud fields: 2. Cumulus cloud fields

Science.gov (United States)

Zhu, T.; Lee, J.; Weger, R. C.; Welch, R. M.

1992-12-01

During the last decade a major controversy has been brewing concerning the proper characterization of cumulus convection. The prevailing view has been that cumulus clouds form in clusters, in which cloud spacing is closer than that found for the overall cloud field and which maintains its identity over many cloud lifetimes. This "mutual protection hypothesis" of Randall and Huffman (1980) has been challenged by the "inhibition hypothesis" of Ramirez et al. (1990) which strongly suggests that the spatial distribution of cumuli must tend toward a regular distribution. A dilemma has resulted because observations have been reported to support both hypotheses. The present work reports a detailed analysis of cumulus cloud field spatial distributions based upon Landsat, Advanced Very High Resolution Radiometer, and Skylab data. Both nearest-neighbor and point-to-cloud cumulative distribution function statistics are investigated. The results show unequivocally that when both large and small clouds are included in the cloud field distribution, the cloud field always has a strong clustering signal. The strength of clustering is largest at cloud diameters of about 200-300 m, diminishing with increasing cloud diameter. In many cases, clusters of small clouds are found which are not closely associated with large clouds. As the small clouds are eliminated from consideration, the cloud field typically tends towards regularity. Thus it would appear that the "inhibition hypothesis" of Ramirez and Bras (1990) has been verified for the large clouds. However, these results are based upon the analysis of point processes. A more exact analysis also is made which takes into account the cloud size distributions. Since distinct clouds are by definition nonoverlapping, cloud size effects place a restriction upon the possible locations of clouds in the cloud field. The net effect of this analysis is that the large clouds appear to be randomly distributed, with only weak tendencies towards

Emission from small dust particles in diffuse and molecular cloud medium

International Nuclear Information System (INIS)

Bernard, J.P.; Desert, X.

1990-01-01

Infrared Astronomy Satellite (IRAS) observations of the whole galaxy has shown that long wavelength emission (100 and 60 micron bands) can be explained by thermal emission from big grains (approx 0.1 micron) radiating at their equilibrium temperature when heated by the InterStellar Radiation Field (ISRF). This conclusion has been confirmed by continuum sub-millimeter observations of the galactic plane made by the EMILIE experiment at 870 microns (Pajot et al. 1986). Nevertheless, shorter wavelength observations like 12 and 25 micron IRAS bands, show an emission from the galactic plane in excess with the long wavelength measurements which can only be explained by a much hotter particles population. Because dust at equilibrium cannot easily reach high temperatures required to explain this excess, this component is thought to be composed of very small dust grains or big molecules encompassing thermal fluctuations. Researchers present here a numerical model that computes emission, from Near Infrared Radiation (NIR) to Sub-mm wavelengths, from a non-homogeneous spherical cloud heated by the ISRF. This model fully takes into account the heating of dust by multi-photon processes and back-heating of dust in the Visual/Infrared Radiation (VIS-IR) so that it is likely to describe correctly emission from molecular clouds up to large A sub v and emission from dust experiencing temperature fluctuations. The dust is a three component mixture of polycyclic aromatic hydrocarbons, very small grains, and classical big grains with independent size distributions (cut-off and power law index) and abundances

Electromagnetic reverberation chambers

CERN Document Server

Besnier, Philippe

2013-01-01

Dedicated to a complete presentation on all aspects of reverberation chambers, this book provides the physical principles behind these test systems in a very progressive manner. The detailed panorama of parameters governing the operation of electromagnetic reverberation chambers details various applications such as radiated immunity, emissivity, and shielding efficiency experiments.In addition, the reader is provided with the elements of electromagnetic theory and statistics required to take full advantage of the basic operational rules of reverberation chambers, including calibration proc

Effects of Mg pre-flow, memory, and diffusion on the growth of p-GaN with MOCVD (Conference Presentation)

Science.gov (United States)

Tu, Charng-Gan; Chen, Hao-Tsung; Chen, Sheng-Hung; Chao, Chen-Yao; Kiang, Yean-Woei; Yang, Chih-Chung

2017-02-01

In MOCVD growth, two key factors for growing a p-type structure, when the modulation growth or delta-doping technique is used, include Mg memory and diffusion. With high-temperature growth (>900 degree C), doped Mg can diffuse into the under-layer. Also, due to the high-pressure growth and growth chamber coating in MOCVD, plenty Mg atoms exist in the growth chamber for a duration after Mg supply is ended. In this situation, Mg doping continues in the following designated un-doped layers. In this paper, we demonstrate the study results of Mg preflow, memory, and diffusion. The results show that pre-flow of Mg into the growth chamber can lead to a significantly higher Mg doping concentration in growing a p-GaN layer. In other words, a duration for Mg buildup is required for high Mg incorporation. Based on SIMS study, we find that with the pre-flow growth, a high- and a low-doping p-GaN layer are formed. The doping concentration difference between the two layers is about 10 times. The thickness of the high- (low-) doping layer is about 40 (65) nm. The growth of the high-doping layer starts 10-15 min after Mg supply starts (Mg buildup time). The diffusion length of Mg into the AlGaN layer beneath (Mg content reduced to doping concentration is reduced to <1%.

Dorsal skinfold chamber models in mice

Directory of Open Access Journals (Sweden)

Schreiter, Jeannine

2017-07-01

Full Text Available Background/purpose: The use of dorsal skinfold chamber models has substantially improved the understanding of micro-vascularisation in pathophysiology over the last eight decades. It allows pathophysiological studies of vascularisation over a continuous period of time. The dorsal skinfold chamber is an attractive technique for monitoring the vascularisation of autologous or allogenic transplants, wound healing, tumorigenesis and compatibility of biomaterial implants. To further reduce the animals’ discomfort while carrying the dorsal skinfold chamber, we developed a smaller chamber (the Leipzig Dorsal Skinfold Chamber and summarized the commercial available chamber models. In addition we compared our model to the common chamber. Methods: The Leipzig Dorsal Skinfold Chamber was applied to female mice with a mean weight of 22 g. Angiogenesis within the dorsal skinfold chamber was evaluated after injection of fluorescein isothiocyanate dextran with an Axio Scope microscope. The mean vessel density within the dorsal skinfold chamber was assessed over a period of 21 days at five different time points. The gained data were compared to previous results using a bigger and heavier dorsal skinfold model in mice. A PubMed and a patent search were performed and all papers related to “dorsal skinfold chamber” from 1 of January 2006 to 31 of December 2015 were evaluated regarding the dorsal skinfold chamber models and their technical improvements. The main models are described and compared to our titanium Leipzig Dorsal Skinfold Chamber model.Results: The Leipzig Dorsal Skinfold Chamber fulfils all requirements of continuous models known from previous chamber models while reducing irritation to the mice. Five different chamber models have been identified showing substantial regional diversity. The newly elaborated titanium dorsal skinfold chamber may replace the pre-existing titanium chamber model used in Germany so far, as it is smaller and lighter

A combination drift chamber/pad chamber for very high readout rates

International Nuclear Information System (INIS)

Spiegel, L.; Cataldi, G.; Elia, V.; Mazur, P.; Murphy, C.T.; Smith, R.P.; Yang, W.; Alexopoulos, T.; Durandet, C.; Erwin, A.; Jennings, J.; Antoniazzi, L.; Introzzi, G.; Lanza, A.; Liguori, G.; Torre, P.; Arenton, M.; Conetti, S.; Cox, B.; Dukes, E.; Golovatyuk, V.; Hanlet, P.; McManus, A.; Nelson, K.; Recagni, M.; Segal, J.; Sun, J.; Ballagh, C.; Bingham, H.; Kaeding, T.; Lys, J.; Misawa, S.; Blankman, A.; Borodin, S.; Kononenko, W.; Newcomer, M.; Selove, W.; Trojak, T.; VanBerg, R.; Zhang, S.N.; Block, M.; Corti, G.; LeCompte, T.; Rosen, J.; Yao, T.; Boden, A.; Cline, D.; Ramachandran, S.; Rhoades, J.; Tokar, S.; Budagov, J.; Tsyganov, E.; Cao, Z.L.; He, M.; Wang, C.; Wei, C.; Zhang, N.; Chen, T.Y.; Yao, N.; Clark, K.; Jenkins, M.; Cooper, M.; Creti, P.; Gorini, E.; Grancagnolo, F.; Panareo, M.; Fortney, L.; Kowald, W.; Haire, M.; Judd, D.; Turnbull, L.; Wagoner, D.; Lau, K.; Mo, G.; Trischuk, J.

1991-11-01

Six medium-sized (∼1 x 2 m 2 ) drift chambers with pad and stripe readout have been constructed for and are presently operating in Fermi National Accelerator Laboratory experiment E-771. Each chamber module actually represents a pair of identical planes: two sets of anode wires, two sets of stripes, and two sets of pads. The wire planes are read out separately and represent X measurements in the coordinate system of the experiment. The twin stripe and pad planes are internally paired within the chamber modules; stripe signals represent Y measurements and pad signals combination X and Y measurements. Signals which develop on the stripes and pads are mirror (but inverted) images of what is seen on the wires. In addition to being used in the off-line pattern recognition, pad signals are also used as inputs to an on-line high transverse momentum (pt) trigger processor. While the techniques involved in the design and construction of the chambers are not novel, they may be of interest to experiments contemplating very large area, high rate chambers for future spectrometers

A combination drift chamber/pad chamber for very high readout rates

Energy Technology Data Exchange (ETDEWEB)

Spiegel, L.; Cataldi, G.; Elia, V.; Mazur, P.; Murphy, C.T.; Smith, R.P.; Yang, W. (Fermi National Accelerator Lab., Batavia, IL (United States)); Alexopoulos, T.; Durandet, C.; Erwin, A.; Jennings, J. (Wisconsin Univ., Madison, WI (United States)); Antoniazzi, L.; Introzzi, G.; Lanza, A.; Liguori, G.; Torre, P. (Pavia Univ. (Italy) Istituto Nazionale di Fisica Nucleare, Rome (Italy)); Arenton, M.; Conetti, S.

1991-11-01

Six medium-sized ({approx}1 {times} 2 m{sup 2}) drift chambers with pad and stripe readout have been constructed for and are presently operating in Fermi National Accelerator Laboratory experiment E-771. Each chamber module actually represents a pair of identical planes: two sets of anode wires, two sets of stripes, and two sets of pads. The wire planes are read out separately and represent X measurements in the coordinate system of the experiment. The twin stripe and pad planes are internally paired within the chamber modules; stripe signals represent Y measurements and pad signals combination X and Y measurements. Signals which develop on the stripes and pads are mirror (but inverted) images of what is seen on the wires. In addition to being used in the off-line pattern recognition, pad signals are also used as inputs to an on-line high transverse momentum (pt) trigger processor. While the techniques involved in the design and construction of the chambers are not novel, they may be of interest to experiments contemplating very large area, high rate chambers for future spectrometers.

Review of wire chamber aging

International Nuclear Information System (INIS)

Va'Vra, J.

1986-02-01

This paper makes an overview of the wire chamber aging problems as a function of various chamber design parameters. It emphasizes the chemistry point of view and many examples are drawn from the plasma chemistry field as a guidance for a possible effort in the wire chamber field. The paper emphasizes the necessity of variable tuning, the importance of purity of the wire chamber environment, as well as it provides a practical list of presently known recommendations. In addition, several models of the wire chamber aging are qualitatively discussed. The paper is based on a summary talk given at the Wire Chamber Aging Workshop held at LBL, Berkeley on January 16-17, 1986. Presented also at Wire Chamber Conference, Vienna, February 25-28, 1986. 74 refs., 18 figs., 11 tabs

High-energy radiation from collisions of high-velocity clouds and the Galactic disc

Science.gov (United States)

del Valle, Maria V.; Müller, A. L.; Romero, G. E.

2018-04-01

High-velocity clouds (HVCs) are interstellar clouds of atomic hydrogen that do not follow normal Galactic rotation and have velocities of a several hundred kilometres per second. A considerable number of these clouds are falling down towards the Galactic disc. HVCs form large and massive complexes, so if they collide with the disc a great amount of energy would be released into the interstellar medium. The cloud-disc interaction produces two shocks: one propagates through the cloud and the other through the disc. The properties of these shocks depend mainly on the cloud velocity and the disc-cloud density ratio. In this work, we study the conditions necessary for these shocks to accelerate particles by diffusive shock acceleration and we study the non-thermal radiation that is produced. We analyse particle acceleration in both the cloud and disc shocks. Solving a time-dependent two-dimensional transport equation for both relativistic electrons and protons, we obtain particle distributions and non-thermal spectral energy distributions. In a shocked cloud, significant synchrotron radio emission is produced along with soft gamma rays. In the case of acceleration in the shocked disc, the non-thermal radiation is stronger; the gamma rays, of leptonic origin, might be detectable with current instruments. A large number of protons are injected into the Galactic interstellar medium, and locally exceed the cosmic ray background. We conclude that under adequate conditions the contribution from HVC-disc collisions to the galactic population of relativistic particles and the associated extended non-thermal radiation might be important.

Cloud occurrences and cloud radiative effects (CREs) from CERES-CALIPSO-CloudSat-MODIS (CCCM) and CloudSat radar-lidar (RL) products

Science.gov (United States)

Ham, Seung-Hee; Kato, Seiji; Rose, Fred G.; Winker, David; L'Ecuyer, Tristan; Mace, Gerald G.; Painemal, David; Sun-Mack, Sunny; Chen, Yan; Miller, Walter F.

2017-08-01

Two kinds of cloud products obtained from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), CloudSat, and Moderate Resolution Imaging Spectroradiometer (MODIS) are compared and analyzed in this study: Clouds and the Earth's Radiant Energy System (CERES)-CALIPSO-CloudSat-MODIS (CCCM) product and CloudSat radar-lidar products such as GEOPROF-LIDAR and FLXHR-LIDAR. Compared to GEOPROF-LIDAR, low-level (40°). The difference occurs when hydrometeors are detected by CALIPSO lidar but are undetected by CloudSat radar. In the comparison of cloud radiative effects (CREs), global mean differences between CCCM and FLXHR-LIDAR are mostly smaller than 5 W m-2, while noticeable regional differences are found. For example, CCCM shortwave (SW) and longwave (LW) CREs are larger than FXLHR-LIDAR along the west coasts of Africa and America because the GEOPROF-LIDAR algorithm misses shallow marine boundary layer clouds. In addition, FLXHR-LIDAR SW CREs are larger than the CCCM counterpart over tropical oceans away from the west coasts of America. Over midlatitude storm-track regions, CCCM SW and LW CREs are larger than the FLXHR-LIDAR counterpart.

SDP_wlanger_3: State of the Diffuse ISM: Galactic Observations of the Terahertz CII Line (GOT CPlus)

Science.gov (United States)

Langer, W.

2011-09-01

Star formation activity throughout the Galactic disk depends on the thermal and dynamical state of the interstellar gas, which in turn depends on heating and cooling rates, modulated by the gravitational potential and shock and turbulent pressures. Molecular cloud formation, and thus the star formation, may be regulated by pressures in the interstellar medium (ISM). To understand these processes we need information about the properties of the diffuse atomic and diffuse molecular gas clouds, and Photon Dominated Regions (PDR). An important tracer of these regions is the CII line at 158 microns (1900.5 GHz). We propose a "pencil-beam" survey of CII with HIFI band 7b, based on deep integrations and systematic sparse sampling of the Galactic disk plus selected targets, totaling over 900 lines of sight. We will detect both emission and, against the bright inner Galaxy and selected continuum sources, absorption lines. These spectra will provide the astronomical community with a large rich statistical database of the diffuse cloud properties throughout the Galaxy for understanding the Milky Way ISM and, by extension, other galaxies. It will be extremely valuable for determining the properties of the atomic gas, the role of barometric pressure and turbulence in cloud evolution, and the properties of the interface between the atomic and molecular clouds. The CII line is one of the major ISM cooling lines and is present throughout the Galactic plane. It is the strongest far-IR emission line in the Galaxy, with a total luminosity about a 1000 times that of the CO J=1-0 line. Combined with other data, it can be used to determine density, pressure, and radiation environment in gas clouds, and PDRs, and their dynamics via velocity fields. HSO is the best opportunity over the next several years to probe the ISM in this tracer and will provide a template for large-scale surveys with dedicated small telescopes and future surveys of other important ISM tracers.

KPOT_wlanger_1: State of the Diffuse ISM: Galactic Observations of the Terahertz CII Line (GOT CPlus)

Science.gov (United States)

Langer, W.

2007-10-01

Star formation activity throughout the Galactic disk depends on the thermal and dynamical state of the interstellar gas, which in turn depends on heating and cooling rates, modulated by the gravitational potential and shock and turbulent pressures. Molecular cloud formation, and thus the star formation, may be regulated by pressures in the interstellar medium (ISM). To understand these processes we need information about the properties of the diffuse atomic and diffuse molecular gas clouds, and Photon Dominated Regions (PDR). An important tracer of these regions is the CII line at 158 microns (1900.5 GHz). We propose a "pencil-beam" survey of CII with HIFI band 7b, based on deep integrations and systematic sparse sampling of the Galactic disk plus selected targets, totaling over 900 lines of sight. We will detect both emission and, against the bright inner Galaxy and selected continuum sources, absorption lines. These spectra will provide the astronomical community with a large rich statistical database of the diffuse cloud properties throughout the Galaxy for understanding the Milky Way ISM and, by extension, other galaxies. It will be extremely valuable for determining the properties of the atomic gas, the role of barometric pressure and turbulence in cloud evolution, and the properties of the interface between the atomic and molecular clouds. The CII line is one of the major ISM cooling lines and is present throughout the Galactic plane. It is the strongest far-IR emission line in the Galaxy, with a total luminosity about a 1000 times that of the CO J=1-0 line. Combined with other data, it can be used to determine density, pressure, and radiation environment in gas clouds, and PDRs, and their dynamics via velocity fields. HSO is the best opportunity over the next several years to probe the ISM in this tracer and will provide a template for large-scale surveys with dedicated small telescopes and future surveys of other important ISM tracers.

Relation of Cloud Occurrence Frequency, Overlap, and Effective Thickness Derived from CALIPSO and CloudSat Merged Cloud Vertical Profiles

Science.gov (United States)

Kato, Seiji; Sun-Mack, Sunny; Miller, Walter F.; Rose, Fred G.; Chen, Yan; Minnis, Patrick; Wielicki, Bruce A.

2009-01-01

A cloud frequency of occurrence matrix is generated using merged cloud vertical profile derived from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Cloud Profiling Radar (CPR). The matrix contains vertical profiles of cloud occurrence frequency as a function of the uppermost cloud top. It is shown that the cloud fraction and uppermost cloud top vertical pro les can be related by a set of equations when the correlation distance of cloud occurrence, which is interpreted as an effective cloud thickness, is introduced. The underlying assumption in establishing the above relation is that cloud overlap approaches the random overlap with increasing distance separating cloud layers and that the probability of deviating from the random overlap decreases exponentially with distance. One month of CALIPSO and CloudSat data support these assumptions. However, the correlation distance sometimes becomes large, which might be an indication of precipitation. The cloud correlation distance is equivalent to the de-correlation distance introduced by Hogan and Illingworth [2000] when cloud fractions of both layers in a two-cloud layer system are the same.

Recent Experimental Results on Amorphous Carbon Coatings for Electron Cloud Mitigation

CERN Document Server

Yin Vallgren, C; Chiggiato, P; Costa Pinto, P; Neupert, H; Taborelli, M; Rumolo, G; Shaposhnikova, E; Vollenberg, W

2011-01-01

Amorphous carbon (a-C) thin films, produced in different coating configurations by using DC magnetron sputtering, have been investigated in laboratory for low secondary electron yield (SEY) applications. After the coatings had shown a reliable low initial SEY, the a-C thin films have been applied in the CERN Super Proton Synchrotron (SPS) and tested with Large Hadron Collider (LHC) type beams.Currently, we have used a-C thin film coated in so-called liner configuration for the electron cloud monitors. In addition the vacuum chambers of three dipole magnets have been coated and inserted into the machine. After describing the different configurations used for the coatings, results of the tests in the machine and a summary of the analyses after extraction will be presented. Based on comparison between different coating configurations, a new series of coatings has been applied on three further dipole magnet vacuum chambers. They have been installed and will be tested in coming machine development runs.

Change of Pressing Chamber Conicalness at Briquetting Process in Briquetting Machine Pressing Chamber

Directory of Open Access Journals (Sweden)

Peter Križan

2012-01-01

Full Text Available In this paper, we will present the impact of the conical shape of a pressing chamber, an important structural parameter. Besides the known impact of the technological parameters of pressing chambers, it is also very important to pay attention to their structural parameters. In the introduction, we present a theoretical analysis of pressing chamber conicalness. An experiment aimed at detecting this impact was performed at our institute, and it showed that increasing the conicalness of a pressing chamber improves the quality of the final briquettes. The conicalness of the pressing chamber has a significanteffect on the final briquette quality and on the construction of briquetting machines. The experimental findings presented here show the importance of this parameter in the briquetting process.