| 1. |
- Afanasiev, Sergey V., et al.
(författare)
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Experimental apparatus to study crystal channeling in an external SPS beamline
- 2007
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Ingår i: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 6634
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Tidskriftsartikel (refereegranskat)abstract
- For the new generation of high intensity hadronic machines as, for instance, LHC, halo collimation is a necessary issue for the accelerator to operate at the highest possible luminosity and to prevent the damage of superconductor magnets.1 We propose an experiment aimed to systematic study of the channeling phenomenology and of the newly observed "volume reflection" effect. This experiment will be performed for an external SPS beamline and will make use of a primary proton beam with 400 GeV/c momentum and very small (∼ 3 μrad) divergence. The advantage of a proposed experiment is precise tracking of particles that interacted with a crystal, so that to determine the single-pass efficiency for all the processes involved. For this purpose, a telescope equipped with high-resolution silicon microstrip detectors will be used. New generation silicon crystals and an extra-precise goniometer are mandatory issues. Main goal of the experiment is to get the precise information on channeling of relativistic particles and, ultimately, on the feasibility of such technique for halo collimation at LHC. In this contribution we review the status of the setting-up of experimental apparatus and its future development in sight of the planned run in September 2006.
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| 2. |
- Baricordi, S., et al.
(författare)
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Low-energy-channeling surface analysis on silicon crystals designed for high-energy-channeling in accelerators
- 2005
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 87:9
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Tidskriftsartikel (refereegranskat)abstract
- Channeling of relativistic particles in bent Si crystals is a powerful technique for use with accelerators. Its efficiency can be found to be highly dependent on the state of the surface of the crystal steering the particles. We investigated the morphology and structure of the surface of the samples that have been used with high efficiency for channeling in accelerators. Low-energy channeling of 2 MeVα particles or protons was used as a probe. We found that mechanical treatment of the samples leads to a superficial damaged layer, which is correlated to efficiency limitations of the crystal in accelerators. In contrast, chemical etching, which was used to treat the surface of the most efficient crystals, leaves a surface with superior perfection. © 2005 American Institute of Physics.
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| 3. |
- Baricordi, S., et al.
(författare)
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Optimal crystal surface for efficient channeling in the new generation of hadron machines
- 2007
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 91:6
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Tidskriftsartikel (refereegranskat)abstract
- The new generation of hadron machines may profitably take advantage of channeling for steering and collimation of high-energy particle beams. In that case, the requirements on the quality of the crystal surface are rather stringent in terms of both lattice perfection and roughness. Here, the authors show the structural and morphological characterizations of crystals fabricated through a method to achieve a surface that fulfills all needed specifications for application in hadron machines. © 2007 American Institute of Physics.
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| 4. |
- Bemmerer, D., et al.
(författare)
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Feasibility of low-energy radiative-capture experiments at the LUNA underground accelerator facility
- 2005
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Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 24:2, s. 313-319
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Tidskriftsartikel (refereegranskat)abstract
- The LUNA (Laboratory Underground for Nuclear Astrophysics) facility has been designed to study nuclear reactions of astrophysical interest. It is located deep underground in the Gran Sasso National Laboratory, Italy. Two electrostatic accelerators, with 50 and 400 kV maximum voltage, in combination with solid and gas target setups allowed to measure the total cross-sections of the radiative-capture reactions 2H2H(p, γ) 3He3Heand 14N14N(p, γ) 15O15Owithin their relevant Gamow peaks. We report on the gamma background in the Gran Sasso laboratory measured by germanium and bismuth germanate detectors, with and without an incident proton beam. A method to localize the sources of beam-induced background using the Doppler shift of emitted gamma rays is presented. The feasibility of radiative-capture studies at energies of astrophysical interest is discussed for several experimental scenarios. © Società Italiana di Fisica/Springer-Verlag 2005.
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| 5. |
- Bianchi, S., et al.
(författare)
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Indium oxide quasi-monodimensional low temperature gas sensor
- 2006
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 118:1-2, s. 204-207
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the sensing properties of indium oxide nanostructures and tailored the deposition conditions in order to obtain nano-wires of indium oxide. We have comparatively tested the gas sensing properties of nano-wires with micrometric or even nanometric size. The micro-wires feature interesting gas sensitivity at room temperature, particularly in the case of nitrogen dioxide detection. The sensing performance is improved as the lateral dimension of the wire decreases. © 2006 Elsevier B.V. All rights reserved.
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| 6. |
- Boscarino, Diego, et al.
(författare)
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Deposition of silica-silver nanocomposites by magnetron cosputtering
- 2005
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 23:1, s. 11-19
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Tidskriftsartikel (refereegranskat)abstract
- Thin films have been grown on silicon and silica substrates by cosputtering of silica and silver in Ar, Ar+2.5% O2, and Ar+5% O2 gas mixtures. Rutherford backscattering spectrometry showed that the films have Ag atomic fractions xAg in the range of ∼1 to ∼10 at. %, and, by valence considerations, that the fraction of oxidized Ag in the films deposited in presence of oxygen is limited. Transmission electron microscopy images revealed the presence of Ag nanoclusters, with a mean size diameter not larger than 5 nm. The clusters are preferentially arranged along columns. It is suggested that the columns are regions with diameter in the nanometer range in which the density of the dielectric matrix is lower, thus favoring the formation of metal clusters. In presence of O2, the clusters were observed to have a more regular spherical shape. The optical absorption spectra of films grown in presence of O2 are distinguished from those grown in Ar by specific features, which are attributed to oxidation at the cluster surface. © 2005 American Vacuum Society.
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| 7. |
- Carturan, S., et al.
(författare)
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Formation of silver nanoclusters in transparent polyimides by Ag-K ion-exchange process
- 2007
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Ingår i: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 42:2, s. 243-251
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Tidskriftsartikel (refereegranskat)abstract
- Silver nanoclusters embedded in two transparent fluorinated polyimides, 4,4'-hexafluoroisopropylidene diphthalic anhydride - 2,3,5,6-tetramethyl paraphenylene diamine (6FDA-DAD) and 3,3',4,4' - biphenyltetracarboxylic acid dianhydride - 1,1-bis(4-aminophenyl)-1-phenyl-2,2,2-trifluoroethane (BPDA-3F), have been produced by surface modification with KOH aqueous solution followed by K-assisted Ag doping and thermal reduction in hydrogen atmosphere. The reaction rate of the nucleophilic hydrolysis in KOH, studied by Fourier transform infrared spectroscopy (FT-IR) and Rutherford backscattering spectrometry (RBS), depends on the polyimide chemical structure. After ion-exchange in AgNO 3 solution and subsequent annealing, the polyimide structure recovery was monitored by FT-IR whereas the characteristic surface plasmon absorption band of silver nanoparticles was evidenced by optical absorption measurements. The structure of silver nanoclusters as related to size and size distribution in the different polyimide matrices was thoroughly investigated by Transmission electron microscopy (TEM) and X-ray diffraction (XRD). The collected data evidenced a uniform distribution of Ag clusters of nanometric size after thermal treatment at 300 °C in both polyimides. For the same ion-exchange treatment parameters and annealing temperature, XRD analyses evidenced the presence of crystallites with similar sizes. © EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2007.
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| 8. |
- Carturan, S., et al.
(författare)
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Polyimide-based scintillators studied by ion beam induced luminescence
- 2005
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Ingår i: IEEE Transactions on Nuclear Science. - 0018-9499 .- 1558-1578. ; 52:3 II, s. 748-751
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Tidskriftsartikel (refereegranskat)abstract
- New organic scintillators for ionizing radiation sensors are synthesized by dispersing dye molecules into chemically imidized polyimide hosts in order to obtain detection systems with improved radiation resistance with respect to the traditional polyvinyltoluene-based materials. Nile red (NR) and rhodamine B (RB) are dispersed at different concentrations in polyimides derived from the following monomers: 6FDA-DAD, 6FDA-DAB, and BPDA-3F. Scintillating thin films are produced by the spin coating technique. Scintillation tests are performed both on pure polyimides and on binary systems by means of ion beam induced luminescence (IBIL), in which the emission spectrum is collected during the irradiation of the films with a 4He+ beam. From the intensity and the degradation rate of the IBIL signal during irradiation, the scintillation efficiency with respect to NE102 and the radiation hardness of the produced films are calculated. © 2005 IEEE.
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| 9. |
- Carturan, S., et al.
(författare)
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Polyimide-based scintillators studied by ion beam induced luminescence
- 2004
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Ingår i: IEEE Nuclear Science Symposium Conference Record. - 1095-7863. ; 2, s. 869-873
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Tidskriftsartikel (refereegranskat)abstract
- New organic scintillators for ionizing radiation sensors are synthesized by dispersing dye molecules into chemically imidized polyimide hosts in order to obtain detection systems with improved radiation resistance with respect to the traditional polyvinyltoluene based materials. Nile Red and Rhodamine B are dispersed at different concentrations in polyimides derived from the following monomers 6FDA-DAD, 6FDA-DAB and BPDA-3F. Scintillating thin films are produced by the spin coating technique. Scintillation tests are performed both on pure polyimides and on binary systems by means of Ion Beam Induced Luminescence (IBIL), in which the emission spectrum is collected during the irradiation of the films with a 4He+ beam. From the intensity and the degradation rate of the IBIL signal during irradiation, the scintillation efficiency with respect to NE102 and the radiation hardness of the produced films are calculated. © 2004 IEEE.
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| 10. |
- Comini, Elisabetta, et al.
(författare)
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Effects of Ta/Nb-doping on titania-based thin films for gas-sensing
- 2005
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 108:1-2 SPEC. ISS., s. 21-28
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of titania with the addition of niobium and tantalum have been achieved by reactive sputtering process. Structural and morphological studies have been carried out by means of XRD, RBS, TEM and AFM in order to correlate the microstructural features to the sensing performance of the layers. The films proved sensitive to ethanol and carbon monoxide and ammonia. In the case of niobium addition, it was shown that annealing temperature and niobium content strongly influence the gas response of the films converting a n-type response, which is typical of pure TiO2 and of most of metal-oxide sensors, to a p-type response; this peculiarity is crucial for the discrimination of different gases. In the case of tantalum addition, the annealing treatment at 800 °C led only to a phase transformation that reduced the sensing performance of the layer. High sensitivity to CO is achieved with anatase or mixed anatase and rutile phases, while the rutile phase only exhibit a low gas sensitivity. © 2005 Elsevier B.V. All rights reserved.
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