ORNL, Oak Ridge, Tennessee
The Spallation Neutron Source is designed to produce 1.4 MW of beam power on a mercury target produced in short (1 μSec) pulses at 60 Hz with a 1 GeV beam. Since the initial beam operations in Oct. 2006, the Spallation Neutron Source has operated production runs with beam power up to 520 kW. Apart from equipment issues, the primary challenge in power ramp up is beam loss. Suspected causes of observed beam loss will be discussed. While not contributing to beam loss at present operational parameters, evidence of collective effects is seen at higher intensities, and will be presented. Other issues of interest at high intensity include foil survivability, and maintaining acceptable power density on the neutron production target
ORNL, Oak Ridge, Tennessee
The 248 meter Spallation Neutron Source accumulator ring is designed to operate with a beam intensity of 1.5·1014 ppp. A major concern for high intensity operation is the possibility of beam instabilities. Recently a series of experiments have been performed to systematically map out the instability parameter space. Beam instabilities have been measured versus betatron tune, ring RF voltage, lattice chromaticity, and beam intensity. The results of these studies are presented here
ORNL, Oak Ridge, Tennessee
The paper describes a usage of the XAL online model for transverse and longitudinal tuning of the SNS linac. Most of the SNS control room physics applications based on the XAL online model which allows synchronizing the model with an accelerator live state and using this model for tuning the machine. Peculiarities of applying of the simplest single particle mode of the model for orbit correction and longitudinal dynamics control of the SNS linac are discussed. The procedure of parameters finding, algorithms, and results are presented.
KEK, Ibaraki
The beam commissioning of J-PARC linac has been started since November 2006, and the initial commissioning has been completed in September 2007. Since then, the linac beam has been supplied to the succeeding RCS (Rapid Cycling Synchrotron) for its commissioning. The emphasis of the linac tuning has been shifted to the stabilization of the beam parameters, and better beam availability has gradually been required for the linac operation. On the other hand, the average beam power is rather limited because we are still in the initial commissioning stage for RCS and MR (Main Ring). The hourly average of the beam power from RCS is limited to 4 kW due to the available beam dump capacity. Accordingly, we still have little experience on the machine activation with a high-power and stable beam operation. In this regard, we are in a transitional stage for our linac from commissioning to operation. In this paper, we present the current linac performance and operational experiences obtained so far after briefly reviewing the commissioning history. Particular emphasis is put on the technical challenges we faced up to the present. Future plans to increase the beam power are also discussed.
ORNL, Oak Ridge, Tennessee
Since the start of neutron production in October of 2006, the average beam power level has increased from ~ 5 kW to over 500 kW. This increased has been realized by increases in the beam current, pulse length and repetition rate. Equipment issues encountered during this ramp-up will be discussed along with mitigation efforts. A major concern in the power ramp up has been minimization of uncontrolled beam loss. The beam loss levels, loss reduction efforts, and experience levels with residual activation will be discussed. Also the operational run cycles will be discussed, with an evolution in emphasis from beam-studies to neutron production.
STFC/RAL/ISIS, Chilton, Didcot, Oxon
ISIS is currently the world's most productive spallation neutron source. A total beam power of ~0.2 MW is delivered by a 70 MeV H- linac and an 800 MeV rapidly cycling proton synchrotron to two target stations, one which has been running since 1984, and a second which is being commissioned this year (2008). ISIS runs for typically ~200 days each year scheduled as some five ~40-day user cycles, although shutdowns lasting several months for major maintenance and upgrade work took place in 2002, 2004 and 2007 (during user cycles ISIS runs 7 days/week, 24 hours/day, and the ~200 days excludes run-up and machine physics time). In order to enable hands-on maintenance régimes to prevail, considerable efforts are made to minimise beam losses during operations, and engineering design of accelerator and beam line components specifically includes measures to limit radiation doses to personnel. The talk will cover these issues and others, and will also describe the difficult balances to be struck between operations, maintenance and upgrade work.
LANL, Los Alamos, New Mexico
The heart of the Los Alamos Neutron Science Center (LANSCE) is a pulsed linear accelerator that is used to simultaneously provide H+ and H- beams to several user facilities. This accelerator contains two Cockcroft-Walton style injectors, a 100-MeV drift tube linac and an 800-MeV coupled cavity linac. This presentation will touch on various aspects of the high power operation including performance and limitations, tune-up strategy, beam losses and machine protection.
PSI, Villigen
The ring cyclotron at the PSI accelerator facility accelerates protons to 590MeV with a current of 2 mA at present. The stepwise increase to 3 mA is planned. During normal operation there are main beam loss points at targets, beam dumps and collimators. If the beam strikes material particles are lost due to multiple scattering. Subsequent nuclear reactions lead to the production of activated materials in the components itself and their surroundings. During shutdown radioactive components have to be removed for disposal or repair. To some extent the removal requires operations done by personnel nearby the activated components. To estimate the personal dose and to plan working procedures, a way to calculate the expected dose is essential. In addition, for later disposal of the radioactive components the nuclide inventory is required by the authorities. The Monte Carlo particle transport code MCNPX coupled to the build-up and decay codes SP-FISPACT, Orihet3 and Cinder’90, as well as the bookkeeping system PWWMBS developed at PSI, are used to calculate the required quantities. Both methods will be presented and the results are compared to measurements of different activated components.
ORNL, Oak Ridge, Tennessee
The Spallation Neutron Source accelerator is a neutron scattering facility for materials research that recently started operations and presently is in the process of power ramp-up to reach mega-watt power level within a year in cycles of operations and maintenance and tuning periods. The structural materials inside the accelerator tunnel are activated by protons beam losses and by secondary particles. Secondary particles appear due to spallation reactions caused by the proton losses, and produce the residual radiation after shut down in the tunnel environment. In order to plan maintenance work after each operations period, residual dose measurements are taking at 30 cm distance from the accelerator structures and on contact. During normal operation, beam losses and beam scenario are recorded and used as a source to calculate expected residual dose rates after shut down. Calculation analyses are performed using the transport code MCNPX followed by the activation calculation script, which uses the nuclear inventory code CINDER’90, then converting gammas production spectra and gamma power to the dose rates. Calculated results for various locations are compared with measured data.
ORNL, Oak Ridge, Tennessee
The paper describes a parallel flow of the Spallation Neutron Source (SNS) linac and ring commissioning and development of commissioning tools. An evolution of the physics control system, its features, problems and solutions are presented. The peculiarities of the SNS project such as a collaboration between six Department of Energy laboratories, an absence of previous experience in large accelerator construction and operation in Oak Ridge National Laboratory, an original upper level of a control system (physics applications) and their effect on SNS commissioning are discussed. SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
University of the Basque Country, Faculty of Science and Technology, Bilbao
Bilbao, Faculty of Science and Technology, Bilbao
Fundación TEKNIKER, Eibar (Gipuzkoa)
Elytt Energy, Madrid
A revised layout for the proton linear accelerator as proposed by the European Spallation Source-Bilbao (Spain) bid to host the installation is here described. The new machine concept aims to incorporate advances which have been registered within the ï¬eld of high power accelerators during the last decade. Particularly relevant are the ongoing works within Magnetic Fusion activities (IFMIF/EVEDA), waste transmutation (EUROTRANS) or radioactive ion beam (EURISOL) and heavy-ion physics (FAIR, SPIRAL2) which have lead to signiï¬cantly shorter accelerators incorporating state-of-the-art technology which mainly replaces decades-old copper drift-tubes, coupled-cavity LINACs or some other accelerating structures employed for energies beyond 50 MeV or so by superconducting cavities (SC) of a wholly new kind. The design of such a new accelerator layout will be critically dependent upon the development and/or adaptation of low β superconducting cavities already developed for some of the referred projects into those adequate for pulsed operation and high duty cycle.
The authors wish to acknowledge extremely fruitful discussions held with scientists from CEA/SACLAY, IPN/ORSAY as well as from the ISIS Spallation Neutron Source.
ORNL, Oak Ridge, Tennessee
The Spallation Neutron Source (SNS) has been in commissioning and then operation since 2002. Beam Instruments for full operation and transition to beam powers of 1.0 MW and beyond needs to evolve to mostly non-intrusive, parasitically available and functioning at 30-60 Hz. High power operation necessitates careful monitoring to minimize un-controlled losses. In this paper, we discuss the overview of all diagnostics and present new improvements to, beam loss monitoring system, transverse and longitudinal laser profile monitors, introduction of laser emittance, addition of view screens at various locations and Mid-IR camera to observe electron deposit due to carbon foils at ring injection area. We also present the challenges in the ring instrumentations to have three decades of response and .01% losses.
ORNL, Oak Ridge, Tennessee
SNS is a 1.5 MW hadron beam facility; so the Beam Loss Monitor (BLM) system is a crucial part of MPS and an important tool for beam tuning. We have installed a number of Neutron Detectors (ND), Ionization Chambers and Photo-Multiplier Tubes (PMT) along the SNS beamline. In this paper we present the current status of equipment installed and experimental data obtained during SNS commissioning and operations. We compare several different types of BLMs and show advantages and disadvantages of every type. The losses are simulated by 3-D transport codes (GEANT4, SHIELD) for different loss scenarios and compared with experimental data. Also we discuss equipment issues like part obsolescence and our vision of next generation BLM system.