GSI, Darmstadt
The FAIR accelerator project at GSI should increase the intensity of primary proton and heavy ion beams by up to two orders of magnitude, relative to the existing GSI facility. In addition to the design of the new synchrotrons and storage rings, the intensity upgrade of the existing UNILAC linac and SIS-18 synchrotron plays a key role for the FAIR project. In order to reach the FAIR design beam parameters several challenges related to operation with high brightness, high current beams in SIS-18 and in the new SIS-100 have to mastered. Important issues are
- the minimization of beam loss caused by space charge induced resonance crossing and the identification of appropriate working points.
- The control of coherent beam instabilities in the presence of space charge, image currents and different ring impedance sources.
- Beam quality conservation during the rf cycle.
- The control of dynamic vacuum pressure during operation with medium charge state heavy ions.
KEK, Ibaraki
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
This talk will review the impedance and beam instabilities study for the J-PARC RCS and MR rings. RCS is possibly the first synchrotron employing a massive amount of ceramic chambers to reduce the eddy current effects on the chambers. The resulting RF shields on the chambers to reduce the beam impedance required new considerations on impedance calculation procedure. MR, on the other hand, uses conventional stain-less steel chambers due to its relatively small rep rate (0.3Hz), but then induces huge resistive-wall impedance. The recent study of resistive-wall impedance shows that the actual impedance will be even larger than the calculated one using the conventional formula, when the typical skin depth becomes comparable to the thickness of the chamber. In my talk, I will also touch on the issues of kicker impedances and their possible cures.
Fermilab, Batavia, Illinois
While a beam is being bunched, a coherent synchrotron frequency grows from zero to a maximal value, crossing many synchro-betatron resonances of the bunch motion. If a related driving force is high enough, the beam can get unstable. This phenomenon is important at Fermilab Booster, presumably being driven by dispersion in the cavities. To stabilize the beam, high chromaticities are required.
GSI, Darmstadt
The head-tail instability is a well known intensity limitation for hadron bunches in synchrotrons. The instability has been observed in several synchrotrons and storage rings. Also for the FAIR synchrotrons the head-tail instability represents a potential intensity limitation. In the SIS-18 and SIS-100 synchrotrons space charge effects together with image currents play an important role for the determination of the instability threshold. In this work we study head-tail modes using 3D particle simulations for SIS100 beam parameters. The unstable modes are driven by the resistive wall impedance. Space-charge and image currents are taken into account. The possibility to include space charge into long-term simulations, which are necessary for head-tail instability studies, is investigated using the HEADTAIL code and the PATRIC code, developed at GSI. Potential instability cures will be discussed.
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.
STFC/RAL/ISIS, Chilton, Didcot, Oxon
ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Presently, it runs at beam powers of 0.2 MW, with upgrades in place to supply increased powers for the new Second Target Station. Studies are also underway for major upgrades in the megawatt regime. Underpinning this programme of operations and upgrades is a study of the high intensity effects that impose the limitations on beam power. This paper summarises work looking at the key topics of half integer resonance, image effects and injection painting under high space charge conditions, plus progress on overall machine modelling. A core aim of the work is to experimentally confirm simulations and theory, therefore progress on modelling the machine in both operational and specially configured modes is reported. Closely related diagnostics studies are also described, as is initial work on instabilities. Finally, future plans are summarised.
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
Fermilab plans to boost the power of Main Injector beam to about 2 MW by building a new SC 8 GeV linac. Its H- beam will be strip injected and accumulated in upgraded Recycler ring, and then transferred to Main Injector for further acceleration to 120 GeV. Beam physics issues related to high intensity operation of Recycler ring and Main Injector are considered.
CERN, Geneva
BNL, Upton, Long Island, New York
In view of the CERN Proton Synchrotron replacement with a new ring (PS2), a detailed optics design is undertaken following several options, which cross or avoid transition. The different lattices are compared with respect to their linear optics flexibility, acceptance and chromatic properties. The effect of magnet misalignments in the beam orbit and linear optics functions are reviewed and correction schemes are proposed. Finally, the different lattice options are compared with respect to single particle non-linear dynamics.
STFC/RAL/ISIS, Chilton, Didcot, Oxon
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
ISIS is the world’s most productive spallation neutron source, at the Rutherford Appleton Laboratory in the UK. Presently, it runs at beam powers of 0.2 MW, with upgrades in place to supply increased powers for the new Second Target Station due to start operation in 2008. This paper outlines favoured schemes for major upgrades to the facility in the megawatt regime, with options for 1, 2 and 5 MW. The ideas centre around new 3.2 GeV RCS designs that can be employed to increase the energy of the existing ISIS beam to provide powers of ~1 MW or, possibly as a second upgrade stage, accumulate and accelerate beam from a new 0.8 GeV linac for 2-5 MW beams. Summaries of ring designs are presented, along with studies and simulations to assess the key loss mechanisms that will impose intensity limitations. Important factors include injection, RF systems, instabilities, longitudinal and transverse space charge.
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.
STFC/RAL/ISIS, Chilton, Didcot, Oxon
ISIS is the spallation neutron source based at the Rutherford Appleton Laboratory in the UK. There are currently 227 individual diagnostic devices distributed between the 70MeV Linac, the 800MeV accelerator ring and the two target beam lines (TS1, TS2). This paper summaries the current state of the ISIS diagnostic systems and describes how the various diagnostics are used to tune the machine, to monitor beam intensity and beam losses and to provide fast machine protection. The limitations and accuracy of the various diagnostic systems (e.g. spatial and energy resolution, sensitivity, speed) are explored along with the steps that are being carried out to tackle any shortcomings. This paper will also briefly look at the new PXI based data acquisition and diagnostic control electronics used on ISIS and the problems encountered in using these systems within radiation environments.
J-PARC, KEK&JAEA, Ibaraki-ken
KEK, Ibaraki
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
J-PARC, KEK & JAEA, Ibaraki-ken
The beam commissioning of the J-PARC Main Ring synchrotron (MR) has been started from May of this year. A single bunch beam from 3 GeV Rapid Cycling Synchrotron (RCS) was injected to the ring through 3-50 beam transporting (3-50BT) and then was extracted to the beam dump after 1000 turns (typically) without acceleration. The beam intensity was 4·1011 ppb that is 2 orders of magnitude smaller than that of the design intensity. The beam diagnostic system was used to establish the beam operational parameters. The system includes the instrumentations as follows; 3 types of Current Transformers (CTs), DCCT, fast CT (FCT), and Wall Current Monitor (WCM); Beam Position Monitors (BPMs); proportional counter type Beam Loss Monitors (BLMs) at each quadropole magnet; horizontal and vertical tune monitors with exciter systems; and 3 types of beam profile monitors, Multi Wire Profile Monitors (MWPMs) at 3-50BT and downstream of injection septa, a horizontal Flying Wire Profile Monitor (FWPM) and a vertical residual gas Ionization Profile Monitor (IPM) in the ring. At the workshop, the present status of the system will be presented.
TRIUMF, Vancouver
GSI, Darmstadt
CERN, Geneva
32 papers were presented. Rather than summarizing each one individually, we give a few highlights, conditioned by the items in the working group charge, namely:
- Summarize the state of the art in simulation capabilities. What developments are needed?
- Summarize the state of the art in theory. What developments are needed?
- Summarize recent developments in benchmarking experimental data with simulations. What critical experiments and diagnostic developments are needed to further refine the theory and simulations?
- Summarize the state of the art in instability mitigation techniques. What further technology developments are needed?
- Summarize the primary limitations to beam intensity in existing circular machines.
- Summarize the key beam dynamics questions for high-intensity circular machines
- Summarize opportunities for advancing the field.