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
The University of Texas at Austin, Austin, Texas
The Fermilab Main Injector is a rapid-cycling synchrotron designed to produce high-flux, high-energy protons beams for fixed-target applications, including antiproton and neutrino production. The present Main Injector produced about 400 kW of 120 GeV protons, but proposed upgrades are designed to produce in excess of 2 MW. One instability of concern is the electron cloud. We have observed the formation of the electron cloud at the Main Injector. At presents intensities it produces no instabilities. We will present measurements made at the Main Injector, including: a threshold for cloud formation, bunch length dependence, conditioning with exposure. In addition, we will describe the evolving program for making measurements at the Main Injector, in anticipation of beam charge upgrades.
ORNL, Oak Ridge, Tennessee
Beam loss is higher than expected in the Ring injection section and in the injection dump beam line. The primary causes are fairly well understood, and we have made some equipment modifications to reduce the loss. In the ring extraction beam line the beam distribution exhibits cross-plane coupling (tilt), and the cause has been traced to a large skew-quadrupole component in the extraction Lambertson septum magnet. In this talk we will discuss the issues surrounding the ring injection and extraction systems, the solutions we have implemented to date, and our plans for future improvements.
KEK, Ibaraki
University of Tennessee, Knoxville, Tennessee
ORNL, Oak Ridge, Tennessee
At the 39th ICFA HB2004 workshop and the EPAC-2006 conference, we reported the lifetime and properties of the HBC (Hybrid type Boron-mixed Carbon) foils, a newly developed material, measured by the use of a 3.2 MeV Ne+ ion beam, which deposits significant energy in the foil due to the heavy ion. The content reported showed superior durability against high temperature damage due to foil deformation, thickness reduction and pinhole production at 1700 ± 100K compared with the cluster foils made by the CADAD method. This time, we measured the lifetime of the HBC-foils and the high quality nanocrystalline diamond foils including commercially available foils at 1800 ± 100K which induces the high temperature damage. The measurements were performed by using the KEK-650 keV high intensity H- and DC beam, which generates the same energy deposition as the RCS of J-PARC. In this workshop, we report the results obtained.
PSI, Villigen
The cyclotron based high power proton accelerator facility at PSI drives a neutron spallation source and two Meson production targets with a CW proton beam at 590MeV kinetic energy. This talk concentrates on the operational and technical aspects specific to acceleration and transport of a high power beam. Furthermore a summary on upgrade plans to increase the beam power from presently 1.2MW to 1.8MW will be given.
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.
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.
Fermilab, Batavia, Illinois
Since January 2008 Fermilab's Main Injector has switched from 2 to 10 batch slip Stacking as an upgrade to 400 KW operation at 120 GeV. Currently the beam power has reached 350 KW and efforts are continuing in order to reach 400 KW. The current performance and the future plans for reaching 700 KW will be described.
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.
Fermilab, Batavia, Illinois
The NuMI beam at Fermilab has delivered almost 5x10 20 120 GeV protons to the neutrino production target, since the start for MINOS physics operation in 2005. We will report on beam operation status, including successes and challenges to date with the beam and NuMI system technical components. Also covered will be the ongoing program of increasing NuMI beam power using slip stacking of beam in the Main Injector accelerator.
KAERI, Daejon
The main purposes of the proton engineering frontier project (PEFP) are developing 100-MeV proton linac and supplying 20-MeV and 100-MeV proton beams to user group. The 20-MeV part of the linac with 24% beam duty has been successfully installed and tested at the KAERI site. Now we are supplying 20-MeV proton beams to users in a restricted beam condition. The fabrication of the remaining part of the DTL with the beam duty of 8% is in progress. The PEFP user facility includes 5 beam lines for 20-MeV and 100-MeV beams, respectively. Form the user surveys the purposes and beam specs are determined for the beam lines. The characteristics of the PEFP beam supplying systems are using the AC magnets to periodically distribute proton beams into several beam lines. At the same time, PEFP concentrates on developing the potential user group of the high intensity proton beams. Several beam utilization programs are under way for this purpose. The civil construction is scheduled to start at the end of this year. The present status and progress of the project are summarized in detail.
Fermilab, Batavia, Illinois
The NuMI proton beam at Fermilab currently delivers 120 GeV protons to the neutrino production target at beam powers up to 320 kW, with design capability to 400 kW. We are preparing for upgrade to 700 kW, and are in planning stage for delivering 2.3 MW beam provided by the Project X accelerator upgrade. We will report on the system of beam diagnostics and control used in operation of the NuMI beam, and the experience to date. Also covered will be the steps to provide a robust system for transport and targeting beam of 2 MW and beyond.
ORNL, Oak Ridge, Tennessee
KEK, Ibaraki
The working group D covered
- commissioning aspects of new high power machines,
- operational aspects of existing high power machines, and
- comparison of modeling and measurements of residual activation buildup.