Results 1 - 10 of 179
Results 1 - 10 of 179. Search took: 0.021 seconds
|Sort by: date | relevance|
[en] MAX Laboratory is a national laboratory in Sweden hosted by Lund University. It operates accelerators producing synchrotron light of very high intensity and quality. As a new high capacity facility, MAX IV, was built at a new site the installations and the entire MAX-lab facility at the University was shutdown late 2015 for immediate decommissioning. After completion of the radiological survey and the planning activities, the physical decommissioning of the MAX-lab facility started in 4. quarter 2015. The buildings will after completed decommissioning be used for other purposes by Lund University. The intention is to complete the entire decommissioning process including clearance of the facility before the end of 2016. An early strategic decision was to apply a waste led decommissioning and to use a risk based graded approach concept. As mentioned above an early action was to perform a radiological characterisation to map the facility in a radiological perspective. Based on the characterisation results, plant owner knowledge and an investigation of historical operational records and incidents the facility was categorised in risk for radioactivity in materials and structures. The plant owner experience that no loose contamination had been generated by the operations of the accelerators was confirmed. Induced activity was found in the installations as well as in the building structure. The radiological survey measurements was also used to generate nuclide vectors to be used for the waste management and the clearance measurements. A rip and ship concept was preferred by the plant owner over several reasons not at least the time aspect. After dismantling all material but concrete with a potential or likely content of radioactivity was sent to the waste treatment facilities at the Studsvik site for clearance measurements or waste treatment. Staff from the waste treatment organisation were involved already in the planning and dismantling processes which made the decommissioning very efficient. After completed dismantling, the surfaces of the remaining structures were measured nuclide specific. Surface areas both over and under the clearance regulation limits were measured. Most results were as expected but, like in all decommissioning processes, some unexpected locations with elevated radioactivity content was identified and was to be managed before application to the regulatory body for clearance of the facility and termination of license. This paper gives an overview of the decommissioning project from the early characterisation activities up to completion and how the plant owner, the decommissioning team and the waste treatment organisations effectively can work together. (authors)
[en] The quest for the missing mass of the universe has become one of the big challenges of todays particle physics and cosmology. Astronomical observations show that only 1% of the matter of the Universe is luminous. Moreover there is now convincing evidence that 85% of all gravitationally observable matter in the Universe is of a new exotic kind, different from the 'ordinary' matter surrounding us. In a series of three lectures we discuss past, recent and future efforts made world- wide to detect and/or decipher the nature of Dark Matter. In Lecture I we review our present knowledge of the Dark Matter content of the Universe and how experimenters search for it's candidates; In Lecture II we discuss so-called 'direct detection' techniques which allow to search for scattering of galactic dark matter particles with detectors in deep-underground laboratories; we discuss the interpretation of experimental results and the challenges posed by different backgrounds; In Lecture III we take a look at the 'indirect detection' of the annihilation of dark matter candidates in astrophysical objects, such as our sun or the center of the Milky Way; In addition we will have a look at efforts to produce Dark Matter particles directly at accelerators and we shall close with a look at alternative nonparticle searches and future prospects. (author)
[en] The quest for the mysterious missing mass of the universe has become one of the big challenges of today's particle physics and cosmology. Astronomical observations show that only 1% of the matter of the universe is luminous. Moreover there is now convincing evidence that 85% of all gravitationally observable matter in the universe is of a new exotic kind, different from the 'ordinary' matter surrounding us. In a series of three lectures we discuss past, recent and future efforts made world-wide to detect and/or decipher the nature of Dark Matter. In Lecture I we review our present knowledge of the Dark Matter content of the Universe and how experimenters search for it's candidates; In Lecture II we discuss so-called 'direct detection' techniques which allow to search for scattering of galactic dark matter particles with detectors in deep-underground laboratories; we discuss the interpretation of experimental results and the challenges posed by different backgrounds; In Lecture III we take a look at the 'indirect detection' of the annihilation of dark matter candidates in astrophysical objects, such as our sun or the center of the Milky Way; In addition we will have a look at efforts to produce Dark Matter particles directly at accelerators and we shall close with a look at alternative nonparticle searches and future prospects. (author)
[en] This white paper informs the nuclear astrophysics community and funding agencies about the scientific directions and priorities of the field and provides input from this community for the 2015 Nuclear Science Long Range Plan. It also summarizes the outcome of the nuclear astrophysics town meeting that was held on August 21–23, 2014 in College Station at the campus of Texas A&M University in preparation of the NSAC Nuclear Science Long Range Plan. It also reflects the outcome of an earlier town meeting of the nuclear astrophysics community organized by the Joint Institute for Nuclear Astrophysics (JINA) on October 9–10, 2012 Detroit, Michigan, with the purpose of developing a vision for nuclear astrophysics in light of the recent NRC decadal surveys in nuclear physics (NP2010) and astronomy (ASTRO2010). Our white paper is informed informed by the town meeting of the Association of Research at University Nuclear Accelerators (ARUNA) that took place at the University of Notre Dame on June 12–13, 2014. In summary we find that nuclear astrophysics is a modern and vibrant field addressing fundamental science questions at the intersection of nuclear physics and astrophysics. These questions relate to the origin of the elements, the nuclear engines that drive life and death of stars, and the properties of dense matter. A broad range of nuclear accelerator facilities, astronomical observatories, theory efforts, and computational capabilities are needed. Answers to long standing key questions are well within reach in the coming decade because of the developments outlined in this white paper.
[en] Parallel coupled voltage multiplier based accelerator topologies offer advantages of better regulation and ripple compared to their series coupled counterparts for Industrial electron beam accelerators. During conditioning and operation these systems undergoes various types of electrical discharges. The discharge can be a direct spark over from the high voltage terminal to ground through SF_6 insulation, vacuum breakdown in the accelerating tube maintained in the order of 10"-"7 mbar pressure, or local discharge between corona guards which are used to couple RF power to the multiplier. There could be discharges in between dynodes of the accelerating tube. As the inter electrode discharges do not reflect in load current, detection of these conditions becomes very difficult. Optical discharge detection methods can be used effectively in this situation. Photo multiplier based optical discharge detection has been deployed in a 3 MeV DC accelerator. Characteristics of the optical signal received during conditioning phase have been presented in this paper. (author)
[en] Particle accelerators are devices that produce beams of energetic ions and electrons which have applications in various fields. Historically, particle accelerators were developed for nuclear physics research. Although the particle physics community is still the main user group, joined by others. There is also an increasing interest in radiation therapy in the medical world and industry has been a long-time user of ion implantation an many other applications. Accelerators are also being used for nuclear energy generation using Thorium and waste management through incineration of minor actinides using accelerator driven sub-critical reactor system (ADS). This is of great interest to India as it has large resources of good quality thorium. The ADS are considered to be an inherently safe system as the reactor is sub-critical. However, ADS require high energy and high current proton beams which involve complex technologies. Accelerators deliver energy to the charged particles by means of electromagnetic fields. Depending on how the electric and magnetic fields are used, the accelerators can be grouped in three categories namely electrostatic or DC accelerators, RF accelerators and colliding rings. In DC accelerators, particles pass through a high voltage and gain energy given by E= qV where q is the charge of ion and V is the voltage tough which ion pass. In order to sustain high voltage accelerator column section is housed inside a pressure vessel which is filled with gas, normally SF_6, at high pressure (100 -150 psig)
[en] The Accelerator and Pulse Power Division (APPD) has designed and developed a 3 MeV, 10 mA DC electron beam accelerator at Electron Beam Centre, Kharghar, Navi Mumbai. This machine has been utilized for reduction of SO_x and NO_x in simulated flue gases and treatment of waste water to reduce COD and BOD
[en] We consider two scenarios of New Physics: the Large Extra Dimensions (LED), where sterile neutrinos can propagate in a (4 + d)-dimensional space-time, and the Non Standard Interactions (NSI), where the neutrino interactions with ordinary matter are parametrized at low energy in terms of effective flavour-dependent complex couplings εαβ. We study how these models have an impact on oscillation parameters in reactor and accelerator experiments.
[en] In pulse power systems, it is required to have synchronized triggering of two or more high voltage spark gaps capable of switching large currents, using electrical trigger pulses. This paper intends to study the synchronization of spark gaps using electrical trigger. The trigger generator consists of dc supply, IGBT switch and driver circuit which generates 8kV, 400ns (FWHM) pulses. The experiment was carried out using two 0.15uF/50kV energy storage capacitors charged to 12kV and discharged through stainless steel spark gaps of diameter 9 mm across 10 ohm non inductive load. The initial experiment shows that synchronization has been achieved with jitter of 50 to 100ns. Further studies carried out to reduce the jitter time by varying various electrical parameters will be presented. (author)
[en] Pulsed electron beam generation requires high power pulses of fast rise, short duration pulse with flat top. With this objective we have designed a low cost compact pulsed power driver based on water dielectric transmission line. The paper describes the design aspects and construction of the pulse power driver and its experimental results. The pulsed power driver consist of a capacitor bank and its charging power supply, high voltage generator, high voltage switch and pulse compression system. (author)