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.
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.
KEK, Ibaraki
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
J-PARC, KEK&JAEA, Ibaraki-ken
Proportional counter is adopted as a main beam loss monitor system for the RCS and MR of J-PARC. The advantages are signal amplification and radiation hardness. In our case the signal amplification more than 500 and the radiation hardness of not only component materials but also its sensitivity which keeps constant upto the charge accumulation of 0.0035 C/mm by Co-60 γ-ray source irradiation, corresponds more than several years operation. The rise time is an order of μs which satisfies the requirement of MPS (Machine Protection System). The system will be overviewed and the performance with radiation sources and beams will be reported comparing with the MARS simulation.
Fermilab, Batavia, Illinois
The FNAL Booster Accelerator delivers about 1017 8 GeV protons/hour. The Booster present cycling rate is 8 Hz but can go as high as 10 Hz with plans to run at 15 Hz. Booster's current operations and future plans required upgrades to most of Booster 30 year old diagnostic hardware and software. Beam quality as well as beam intensity and cycle repetition rate first became an issue when the neutrino experiment BooNE started in 2002. Since then MI slip stacking and continuation of running to MiniBooNE continues to push Booster diagnostics and software upgrades. Control of residual radiation while increasing the Booster throughput over 10 fold has been successful but the work is not done.
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.