| 1. |
- Akkoyun, S., et al.
(författare)
-
AGATA - Advanced GAmma Tracking Array
- 2012
-
Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002 .- 0167-5087 .- 1872-9576. ; 668, s. 26-58
-
Tidskriftsartikel (refereegranskat)abstract
- The Advanced GAmma Tracking Array (AGATA) is a European project to develop and operate the next generation γ-ray spectrometer. AGATA is based on the technique of γ-ray energy tracking in electrically segmented high-purity germanium crystals. This technique requires the accurate determination of the energy, time and position of every interaction as a γ ray deposits its energy within the detector volume. Reconstruction of the full interaction path results in a detector with very high efficiency and excellent spectral response. The realisation of γ-ray tracking and AGATA is a result of many technical advances. These include the development of encapsulated highly segmented germanium detectors assembled in a triple cluster detector cryostat, an electronics system with fast digital sampling and a data acquisition system to process the data at a high rate. The full characterisation of the crystals was measured and compared with detector- response simulations. This enabled pulse-shape analysis algorithms, to extract energy, time and position, to be employed. In addition, tracking algorithms for event reconstruction were developed. The first phase of AGATA is now complete and operational in its first physics campaign. In the future AGATA will be moved between laboratories in Europe and operated in a series of campaigns to take advantage of the different beams and facilities available to maximise its science output. The paper reviews all the achievements made in the AGATA project including all the necessary infrastructure to operate and support the spectrometer. © 2011 Elsevier B.V. All rights reserved.
|
|
| 2. |
- Wiedorn, Max O., et al.
(författare)
-
Megahertz serial crystallography
- 2018
-
Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- The new European X-ray Free-Electron Laser is the first X-ray free-electron laser capable of delivering X-ray pulses with a megahertz inter-pulse spacing, more than four orders of magnitude higher than previously possible. However, to date, it has been unclear whether it would indeed be possible to measure high-quality diffraction data at megahertz pulse repetition rates. Here, we show that high-quality structures can indeed be obtained using currently available operating conditions at the European XFEL. We present two complete data sets, one from the well-known model system lysozyme and the other from a so far unknown complex of a beta-lactamase from K. pneumoniae involved in antibiotic resistance. This result opens up megahertz serial femtosecond crystallography (SFX) as a tool for reliable structure determination, substrate screening and the efficient measurement of the evolution and dynamics of molecular structures using megahertz repetition rate pulses available at this new class of X-ray laser source.
|
|
| 3. |
- Brenning, Nils, et al.
(författare)
-
Optimization of HiPIMS discharges : The selection of pulse power, pulse length, gas pressure, and magnetic field strength
- 2020
-
Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 38:3
-
Tidskriftsartikel (refereegranskat)abstract
- In high power impulse magnetron sputtering (HiPIMS) operation, there are basically two goals: a high ionized flux fraction of the sputtered target material and a high deposition rate. In this work, it is demonstrated that the former always comes at the cost of the latter. This makes a choice necessary, referred to as the HiPIMS compromise. It is here proposed that this compromise is most easily made by varying the discharge current amplitude, which opens up for optimization of additionally four external process parameters: the pulse length, the working gas pressure, the magnetic field strength, and the degree of magnetic unbalance to achieve the optimum combination of the ionized flux fraction and the deposition rate. As a figure of merit, useful for comparing different discharges, ( 1 - beta t ) is identified, which is the fraction of ionized sputtered material that escapes back-attraction toward the cathode target. It is shown that a discharge with a higher value of ( 1 - beta t ) always can be arranged to give better combinations of ionization and deposition rate than a discharge with a lower ( 1 - beta t ). Maximization of ( 1 - beta t ) is carried out empirically, based on data from two discharges with Ti targets in Ar working gas. These discharges were first modeled in order to convert measured plasma parameters to values of ( 1 - beta t ). The combined effects of varying the different process parameters were then analyzed using a process flow chart model. The effect of varying the degree of unbalance in the studied range was small. For the remaining three parameters, it is found that optimum is achieved by minimizing the magnetic field strength, minimizing the working gas pressure, and minimizing the pulse length as far as compatible with the requirement to ignite and maintain a stable discharge.
|
|
| 4. |
- Chelgani, Saeed Chehreh, et al.
(författare)
-
A review of rare earth minerals flotation : Monazite and xenotime
- 2015
-
Ingår i: International Journal of Mining Science and Technology. - : Elsevier. - 2095-2686. ; 25:6, s. 877-883
-
Tidskriftsartikel (refereegranskat)abstract
- This paper reviews rare earth minerals (monazite and xenotime) separation by flotation. A wide range of monazite and xenotime flotation test results are summarized including: reasons of variation in the point of zero charges on these minerals, the effects of various flotation conditions on zeta potential of monazite and xenotime, interactions of collectors and depressants on the surface of these minerals during flotation separation, relationship between surface chemistry of the minerals and different types of collector adsorptions and effects of the conditioning temperature on flotation of rare earth minerals. This review collects various approaches for the selective separation of monazite and xenotime by flotation and gives perspectives for further research in the future.
|
|
| 5. |
- Chelgani, Saeed Chehreh, et al.
(författare)
-
Study of the relationship between zinnwaldite chemical composition and magnetic susceptibility
- 2015
-
Ingår i: Minerals Engineering. - : Elsevier. - 0892-6875 .- 1872-9444. ; 72, s. 27-30
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigates the relationship between chemical analyses and magnetic susceptibility of zinnwaldite through magnetic separation of various size fractions. Statistical analyses were used to increase information about magnetic properties of this mineral as a future source of lithium. Statistical modeling indicated that magnetic susceptibility (as a main factor of magnetic separation) accurately can be predicted based on cations content of zinnwaldite. However the size of particles had a significant effect on magnetic susceptibility. The small difference between the estimated and measured values for the non-linear relationship of this prediction (less than 1 (10−8 m3/kg)) shows that these accurate theoretical techniques can be also applied to estimate magnetic properties of zinnwaldite in other resources, and in-situ analysis.
|
|
| 6. |
- Leistner, T., et al.
(författare)
-
A study of the reprocessing of fine and ultrafine cassiterite from gravity tailing residues by using various flotation techniques
- 2016
-
Ingår i: Minerals Engineering. - : Elsevier. - 0892-6875 .- 1872-9444. ; 96-97, s. 94-98
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigates the reprocessing of once disposed tin tailings from a historic German tin operation through different surface properties based processing techniques. Froth flotation and agglomeration flotation, by using commercially available cassiterite collectors from Clariant, were chosen as processing techniques. Isooctane as a nonpolar oil was used to promote the collection of ultrafine (−10 μm) cassiterite by selective agglomeration, and thus, size enlargement. Results indicate that by using sulfosuccinamates as a collector, around 80% of the fine (−50 μm) to very fine (−20 μm) cassiterite can be recovered (representing ∼50% of the total cassiterite in the tailings sample). Agglomeration flotation experiments showed inferior results for recovering the ultrafine cassiterite (for feed fractions in the −25 μm size range). Oil/froth interaction and increased pulp ion content are considered as the main contributing causes.
|
|
| 7. |
- Rudolph, Martin, et al.
(författare)
-
On how to measure the probabilities of target atom ionization and target ion back-attraction in high-power impulse magnetron sputtering
- 2021
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 129:3
-
Tidskriftsartikel (refereegranskat)abstract
- High-power impulse magnetron sputtering (HiPIMS) is an ionized physical vapor deposition technique that provides a high flux of ionized target species for thin film growth. Optimization of HiPIMS processes is, however, often difficult, since the influence of external process parameters, such as working gas pressure, magnetic field strength, and pulse configuration, on the deposition process characteristics is not well understood. The reason is that these external parameters are only indirectly connected to the two key flux parameters, the deposition rate and ionized flux fraction, via two internal discharge parameters: the target atom ionization probability alpha (t) and the target ion back-attraction probability beta (t). Until now, it has been difficult to assess alpha (t) and beta (t) without resorting to computational modeling, which has hampered knowledge-based optimization. Here, we present a simple method to deduce alpha (t) and beta (t) based on measured deposition rates of neutrals and ions. The core of the method is a refined analytical model, which is described in detail. This approach is furthermore validated by independent calculations of alpha (t) and beta (t) using the considerably more complex ionization region model, which is a plasma-chemical global discharge model.
|
|
