| 1. |
- Cederfelt, Sven Inge, et al.
(författare)
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On the charge limit for crystallizing particles
- 1990
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Ingår i: Journal of Aerosol Science. - 0021-8502. ; 21:SUPPL. 1, s. 127-130
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Tidskriftsartikel (refereegranskat)abstract
- The electrical charge limit of crystallizing sodium chloride droplets has been studied. Moderately charged sodium chloride solution droplets were dried to highly charged residual particles. The charge limit was found to be near the Rayleigh charge limit for saturated sodium chloride droplets of the same size as the residual particle. The charge loss was not found to affect the particle size to a detectable degree.
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| 2. |
- Martinsson, Bengt G., et al.
(författare)
-
A high-sensitivity method for hydrogen analysis in thin targets
- 1993
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Ingår i: Nuclear Inst. and Methods in Physics Research, B. - 0168-583X. ; 82:4, s. 589-599
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Tidskriftsartikel (refereegranskat)abstract
- A sensitive and fast method for hydrogen analysis has been developed. The method is based on a technique where a proton beam of a few MeV impinges on the target and the elastically scattered proton and the recoiling target hydrogen nucleus are detected in coincidence. The method makes use of the difference in time of flight and requires no energy determination. The system consists of two thin, large-area plastic scintillation detectors placed at angles of 45° relative to the beam direction on either side of the beam. Evaluations of the system showed that a stable coincidence yield with respect to position in the target plane and target displacement can be obtained provided that the geometry of the setup is carefully designed. The yield as a function of target thickness was almost linear for target thicknesses up to 2000 μg/cm2. It was also found that count rates up to 500000 s-1 in each branch may be used. The minimum detection limit for the hydrogen detection system was found to be of the order of a few pg/cm2 for a proton beam energy of 3.6 MeV.
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| 3. |
- MARTINSSON, BENGT G., et al.
(författare)
-
A relative humidity processing method for the sampling of aerosol particles with low growth‐ability
- 1992
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Ingår i: Tellus. Series B: Chemical and Physical Meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 44:5, s. 632-644
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Tidskriftsartikel (refereegranskat)abstract
- A method for the fractionation of aerosol particles with respect to size and ability to grow with an increased relative humidity has been developed. The system consists of cascade impactors, diffusion driers, a humidifier and a temperature stabiliser. Diffusion driers were designed and the vapour penetration was modelled below 20%. A humidifier which can be operated with an output relative humidity above 95% was developed. Flow‐rates up to 51/min can be used and the relative humidity can be controlled within approximately 1%. The ability of the system to fractionate aerosol particles with respect to growth with relative humidity was investigated. The equivalent aerodynamic diameter growth factor for sodium chloride was determined to 2 at a relative humidity of 98%, in good agreement with theory. The growth is used to collect particles with no, or limited growth with increased relative humidity in separate fractions for chemical characterisation. This is obtained with an impactor stage operated at high relative humidity followed by a diffusion drier and an impactor stage with a factor of 1.4 lower cut‐off diameter operated at low relative humidity, where the particles with low growth‐ability are collected. The system was in operation during the EUROTRAC sub‐project Ground‐based Cloud Experiment (GCE) at Po Valley, supplying important information on the particle size related scavenging and the elemental composition of particles with a low growth‐ability.
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| 4. |
- Martinsson, Bengt G., et al.
(författare)
-
Elemental composition of fog interstitial particle size fractions and hydrophobic fractions related to fog droplet nucleation scavenging
- 1992
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Ingår i: Tellus. Series B: Chemical and Physical Meteorology. - : Stockholm University Press. - 0280-6509. ; 44:5, s. 593-603
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Tidskriftsartikel (refereegranskat)abstract
- The cloud nucleation scavenging process was studied during a joint campaign of the EUROTRAC sub‐project Ground‐based Cloud Experiment. It was found that the particle size has a strong influence on the partitioning of particles between the cloud droplet and the interstitial aerosol reservoirs. A new aerosol sampling unit, the relative humidity processing system, was employed for the extraction of particles with a low growth‐ability with respect to increased relative humidity. The system supplied tracer elements on the particle growth‐ability. These elements could be used to identify a factor related to particle hygroscopic properties, which was in effect as a selector of cloud condensation nuclei.
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| 5. |
- Martinsson, Bengt G., et al.
(författare)
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Experimental cross sections for Bremsstrahlung production by the impact of MeV protons on low-Z targets
- 1990
-
Ingår i: Nuclear Inst. and Methods in Physics Research, B. - 0168-583X. ; 47:4, s. 361-369
-
Tidskriftsartikel (refereegranskat)abstract
- The production of continuously distributed X-rays by the impact of protons of 1.9-3.0 MeV for X-ray energies between 4 and 6.5 keV, and 1.9-2.65 MeV for X-ray energies between 1.7 and 4 keV has been investigated. Five different target types have been irradiated: polyethylene, polystyrene, carbon. KaptonTM and MylarTM. The results are presented as absolute cross sections for continuous X-ray production at the proton energy 2.55 MeV, and the proton energy dependence is presented in terms of linear and exponential functions in different regimes related to electron binding energy. The effect of electron escape was investigated. The data were modelled using the concept of effective electron escape depth.
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