SNS

Paper	Title	Other Keywords	Page
MOZAPA02	Commissioning Highlights of the Spallation Neutron Source	linac, target, proton, extraction	29
	N. Holtkamp ORNL, Oak Ridge, Tennessee
	The Spallation Neutron Source (SNS) is a second generation pulsed neutron source at Oak Ridge National Laboratory. The SNS is funded by the U.S. Department of Energy's Office of Basic Energy Sciences and is dedicated to the study of the structure and dynamics of materials by neutron scattering. A collaboration composed of six national laboratories (ANL, BNL, TJNAF, LANL, LBNL, ORNL) is responsible for the design and construction of the various subsystems. With the official start in October 1998, the operation of the full facility has begun in late spring 2006 delivering a 1.0 GeV proton beam with a pulse length of approximately 700 nanoseconds on a liquid mercury target. Within the next two years a beam power of more than one MW should be achieved. The multi-lab collaboration provided a large variety of expertise in order to enhance the beam power delivered by the accelerator by almost an order of magnitude compared to existing neutron facilities. The SNS linac consists of a room temperature and superconducting (sc) structures and is the first pulsed high power sc linac in the world. The compressor ring and the target are the final subsystems that were commissioned during early 06.
	Transparencies
MOPCH127	SNS Warm Linac Commissioning Results	linac, CCL, beam-losses, emittance	342
	A.V. Aleksandrov, S. Assadi, W. Blokland, P. Chu, S.M. Cousineau, V.V. Danilov, C. Deibele, J. Galambos, S. Henderson, D.-O. Jeon, M.A. Plum, A.P. Shishlo ORNL, Oak Ridge, Tennessee
	The Spallation Neutron Source accelerator systems will deliver a 1.0 GeV, 1.4 MW proton beam to a liquid mercury target for neutron scattering research. The accelerator complex consists of an H- injector, capable of producing one-ms-long pulses at 60Hz repetition rate with 38 mA peak current, a 1 GeV linear accelerator, an accumulator ring and associated transport lines. The 2.5MeV beam from the Front End is accelerated to 86 MeV in the Drift Tube Linac, then to 185 MeV in a Coupled-Cavity Linac and finally to 1 GeV in the Superconducting Linac. The staged beam commissioning of the accelerator complex is proceeding as component installation progresses. Current results of the beam commissioning program of the warm linac will be presented including transverse emittance evolution along the linac, longitudinal bunch profile measurements at the beginning and end of the linac, and beam loss study.
MOPCH129	Status of the SNS Beam Power Upgrade Project	target, linac, emittance, kicker	345
	S. Henderson, A.V. Aleksandrov, D.E. Anderson, S. Assadi, I.E. Campisi, F. Casagrande, M.S. Champion, R.I. Cutler, V.V. Danilov, G.W. Dodson, D.A. Everitt, J. Galambos, J.R. Haines, J.A. Holmes, N. Holtkamp, T. Hunter, D.-O. Jeon, S.-H. Kim, D.C. Lousteau, T.L. Mann, M.P. McCarthy, T. McManamy, G.R. Murdoch, M.A. Plum, B.R. Riemer, M.P. Stockli, D. Stout, R.F. Welton ORNL, Oak Ridge, Tennessee
	The baseline Spallation Neutron Source (SNS) accelerator complex, consisting of an H- injector, a 1 GeV linear accelerator, an accumulator ring and associated transport lines, will provide a 1 GeV, 1.44 MW proton beam to a liquid mercury target for neutron production. Upgrades to the SNS accelerator and target systems to increase the beam power to at least 2 MW, with a design goal of 3 MW, are in the planning stages. The increased SNS beam power can be achieved primarily by increasing the peak H- ion source current from 38 mA to 59 mA, installing additional superconducting cryomodules to increase the final linac beam energy to 1.3 GeV, and modifying injection and extraction hardware in the ring to handle the increased beam energy. The mercury target power handling capability will be increased to 2 MW or greater by i) mitigating cavitation damage to the target container through improved materials/surface treatments, and introducing a fine dispersion of gas bubbles in the mercury, and ii) upgrading the proton beam window, inner reflector plug and moderators. The upgrade beam parameters will be presented and the required hardware modifications will be described.
MOPCH193	SNS 2.1K Cold Box Turn-down Studies	cryogenics, controls, linac, SLAC	514
	F. Casagrande, P.A. Gurd, D.R. Hatfield, M.P. Howell, W.H. Strong ORNL, Oak Ridge, Tennessee D. Arenius, J. Creel, V. Ganni, P. Knudsen Jefferson Lab, Newport News, Virginia
	The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is nearing completion. The cold section of the Linac consists of 81 superconducting radio frequency cavities cooled to 2.1K by a 2400 watt cryogenic refrigeration system. The 2.1K cold box consists of four stages of centrifugal compressors with LN2-cooled variable speed electric motors and magnetic bearings. The cryogenic system successfully supported the Linac beam commissioning at both 4.2K and 2.1K and has been fully operational since June 2005. This paper describes the control principles utilized and the experimental results obtained for the SNS cold compressors turn-down capability to about 30% of the design flow, and possible limitation of the frequency dependent power factor of the cold compressor electric motors, which was measured for the first time during commissioning. These results helped to support the operation of the Linac over a very broad and stable cold compressor operating flow range (refrigeration capacity) and pressure. This in turn helped to optimise the cryogenic system operating parameters, minimizing the utilities and improving the system reliability and availability.
TUOCFI01	Radiation Measurements vs. Predictions for SNS Linac Commissioning	linac, radiation, shielding, CCL	977
	I.I. Popova, F. X. Gallmeier, P. L. Gonzalez, D. C. Gregory ORNL, Oak Ridge, Tennessee
	Detailed predictions for radiation fields, induced inside and outside of the accelerator tunnel, were performed for each of the SNS accelerator commissioning stages, from the ion source through the entire LINAC. Analyses were performed for normal commissioning parameters, for worst possible beam accidents, and for beam fault studies, using the Monte Carlo code MCNPX. Proper temporary shielding was developed and installed in local areas near beam termination points (beam stops) and some critical locations, such as penetrations, in order to minimize dose rates in general occupied areas. Areas that are not full-time occupied and have dose rates above a specified limit during beam accident and fault studies were properly restricted. Radiation monitoring was performed using real time radiation measurement devices and TLDs to measure absorbed dose and dose equivalent rates. The measured radiation fields were analyzed and compared with transport simulations. TLD readings vs. calculations are in a good agreement, generally within a factor of two difference. A large inconsistency among instrument readings is observed, and an effort is underway to understand the variations.
	Transparencies
TUOCFI02	First Results of SNS Laser Stripping Experiment	laser, ion, proton, electron	980
	V.V. Danilov, A.V. Aleksandrov, S. Assadi, J. Barhen, Y. Braiman, D.L. Brown, W. Grice, S. Henderson, J.A. Holmes, Y. Liu, A.P. Shishlo ORNL, Oak Ridge, Tennessee
	Thin carbon foils are used as strippers for charge exchange injection into high intensity proton rings. However, the stripping foils become radioactive and produce uncontrolled beam loss, which is one of the main factors limiting beam power in high intensity proton rings. Recently, we presented a scheme for laser stripping of an H- beam for the SNS ring. First, H- atoms are converted to H0 by a magnetic field, then H0 atoms are excited from the ground state to the upper levels by a laser, and the excited states are converted to protons by a magnetic field. This paper presents first results of the SNS laser stripping proof-of-principle experiment. The experimental setup is described, and possible explanations of the data are discussed.
	Transparencies
TUPLS129	EURISOL 100 kW Target Stations Operation and Implications for its Proton Driver Beam	target, proton, EURISOL, ion	1807
	E. Noah, F. Gerigk, J. Lettry, M. Lindroos, T. Stora CERN, Geneva
	Targets for the next generation radioactive ion beam (RIB) facilities (RIA, EURISOL) will be subjected to energy deposition levels that call for a specific design of the target and ion source assembly to dissipate the deposited heat and to extract and ionize isotopes of interest efficiently. EURISOL, the next generation European RIB facility, plans to operate four target stations in parallel, three 100 kW direct targets and one 5 MW spallation neutron source with a GeV proton linac driver. The nature of the beam sharing has yet to be defined because in practice it will have a direct impact on target design, operation and lifetime. Splitting the beam in time implies that each target would be subjected to a pulsed beam, whose pulse width and repetition cycle have to be optimized in view of the RIB production. The 100 kW targets are expected to have a goal lifetime of three weeks. Target operation from the moment it is installed on a target station until its exhaustion involves several phases during which the incident proton beam intensity will vary. This paper discusses challenges for high power targetry at EURISOL, with an emphasis on requirements for the proton linac parameters.
TUPLS140	An Overview of the SNS Accelerator Mechanical Engineering	target, vacuum, BNL, RTBT	1831
	G.R. Murdoch, J.J. Error, M.P. Hechler, S. Henderson, M. Holding, T. Hunter, P. Ladd, T.L. Mann, R. Savino, J.P. Schubert ORNL, Oak Ridge, Tennessee H.-C. Hseuh, H. Ludewig, G.J. Mahler, C. Pai, C. Pearson, J. Rank, J.E. Tuozzolo, J. Wei BNL, Upton, Long Island, New York
	The Spallation Neutron Source (SNS) is an accelerator-based neutron source currently nearing completion at Oak Ridge National Laboratory. When completed in 2006, the SNS will provide a 1GeV, 1.44MW proton beam to a liquid mercury target for neutron production. SNS is a collaborative effort between six U.S. Department of Energy national laboratories and offered a unique opportunity for the mechanical engineers to work with their peers from across the country. This paper presents an overview of the overall success of the collaboration concentrating on the accelerator ring mechanical engineering along with some discussion regarding the relative merits of such a collaborative approach. Also presented are a status of the mechanical engineering installation and a review of the associated installation costs.
THPCH025	Electron Cloud Self-consistent Simulations for the SNS Ring	electron, proton, simulation, lattice	2832
	A.P. Shishlo, S.M. Cousineau, V.V. Danilov, S. Henderson, J.A. Holmes, M.A. Plum ORNL, Oak Ridge, Tennessee
	The electron cloud dynamics is simulated for the Spallation Neutron Source ring using the self-consistent electron-cloud model for long-bunched proton beams implemented in the ORBIT code. These simulations feature simultaneous calculations of the dynamics of the proton bunch and of the electron cloud, including electron multipacting using a realistic secondary emission surface model. The frequency spectra and growth rates of the proton bunch transverse instability are studied as functions of the RF cavity voltage. The effectiveness of an electron-cloud instability suppression system is also studied using an ORBIT model of the real feedback system. SNS is a collaboration of six US National Laboratories: Argonne National Laboratory (ANL), Brookhaven National Laboratory (BNL), Thomas Jefferson National Accelerator Facility (TJNAF), Los Alamos National Laboratory (LANL), Lawrence Berkeley National Laboratory (LBNL), and Oak Ridge National Laboratory (ORNL).
THPCH156	SNS Transverse and Longitudinal Laser Profile Monitors Design, Implementation and Results	laser, electron, SCL, linac	3161
	S. Assadi ORNL, Oak Ridge, Tennessee
	SNS is using a Nd:YAG laser to measure transverse profiles at nine-stations in the 186-1000 MeV Super-Conducting LINAC (SCL) and a Ti:Sapphire mode-locked laser to measure longitudinal profiles in the 2.5 MeV Medium Energy Beam Transport (MEBT). The laser beam is scanned across the H- beam to photo-neutralize narrow slices. The liberated electrons are directly collected to measure the transverse or longitudinal beam profiles. We have successfully measured the transverse and longitudinal profiles at all stations. The SCL laser system uses an optical transport line that is installed alongside the 300 meter super-conducting LINAC to deliver laser light at nine locations. Movement of the laser light in the optical transport system can lead to problems with the profile measurement. We are using telescopes to minimize the oscillations and active feedback system on mirrors to correct the drifts and movements. In this paper we present our implementation and beam profiles measured during SCL commissioning. We also discuss future improvements, drift/vibration cancellation system, as well as plan to automate subsystems for both the transverse and the longitudinal profiles.