Fermilab, Batavia, Illinois
Project X is a concept for an intense 8 GeV proton source that provides beam for the Fermilab Main Injector and an 8 GeV physics program. The source consists of an 8 GeV superconducting linac that injects into the Fermilab Recycler where multiple linac beam pulses are stripped and accumulated. The 8 GeV linac consists of a low energy front end possibly based on superconducting technology and a high energy end composed of ILC-like cryomodules.
Fermilab, Batavia, Illinois
Cooling of hadron beams is often the only technique by which accelerator facilities around the world achieve the necessary beam brightness necessary for their physics research. In this paper, we will give an overview of the latest developments in hadron beam cooling, for which high energy electron cooling at Fermilab’s Recycler ring and bunched beam stochastic cooling at Brookhaven National Laboratory’s RHIC facility represent two recent major accomplishments. Novel ideas in the field will also be introduced.
BNL, Upton, Long Island, New York
A strong interest in running RHIC at low energies in a range of 2.5-25 GeV/nucleon total energy of a single beam has emerged recently. Providing collisions in this energy range, which in RHIC case is termed “low-energy” operation, will help to answer one of the key questions in the field of QCD about existence and location of critical point on the QCD phase diagram. To evaluate the challenges of RHIC operation at such low energies there have been several short test runs during RHIC operations in 2006, 2007 and 2008. The beam lifetime observed during the test runs was clearly limited by machine nonlinearities. This performance can be improved provided sufficient time is given for machine development at these low energies. After the lifetime caused by nonlinearities is improved the strongest limitation comes from transverse and longitudinal Intra-beam Scattering (IBS), and ultimately by the space-charge limit. A significant luminosity improvement can be provided with electron cooling applied directly in RHIC at low energies. This report summarizes various beam dynamics limiting effects and possible improvement with electron cooling.
UMD, College Park, Maryland
Beam halo is one of the major limiting factors to the effective transport of intense beams. In this paper, we use the WARP particle-in-cell code to numerically investigate the effect of different initial particle distributions on the properties of mismatch-induced halo. In particular, we use equilibrium and non-equilibrium distributions, the latter prompted by experimental measurements of the beam distribution in the University of Maryland Electron Ring (UMER). In both cases, we observe the phase space structure expected in the case of resonances between beam envelope oscillations and single-particle trajectories.
Tech-X, Boulder, Colorado
BNL, Upton, Long Island, New York
Jefferson Lab, Newport News, Virginia
Novel electron-hadron collider concepts are a long-term priority for the international nuclear physics community. Effective beam cooling for intense, relativistic hadron beams will be necessary to obtain the orders-of-magnitude higher luminosities being proposed. Coherent electron cooling (CEC) [1] combines the best features of electron cooling and stochastic cooling, via free-electron laser technology [2], to offer the possibility of cooling high-energy hadron beams much faster. Many technical difficulties must be resolved via full-scale 3D simulations, before the CEC concept can be validated experimentally. The parallel VORPAL framework [3] is the ideal code for simulating the modulator and kicker regions, where the electron and hadron beams will co-propagate as in a conventional electron cooling section. We present initial VORPAL simulations of the electron density wake driven by single ions in the modulator section. Also, we present a plan for simulating the full modulator-amplifier-kicker dynamics, by through use of a loosely-coupled code suite including VORPAL, an FEL code and a beam dynamics code.
[1] Y.S. Derbenev, Proc. COOL07, 149 (2007).
[2] V.N. Litvinenko & Y.S. Derbenev, Proc. FEL07, 268 (2007).
[3] G.I. Bell et. al., J. Comp. Phys. (2008), in press.
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
LBNL, Berkeley, California
We present electron-cloud build-up simulations for the FNAL Main Injector at the location of the RFA electron detector. By comparing our simulated results against measurements for various bunch intensities and beam fill patterns, we determine the likely value of the peak secondary emission yield. We then extrapolate our results to higher intensities, within the range contemplated by the proposed MI upgrade program. We predict a substantial increase of the electron cloud density relative to its present value. We consider two values of the RF frequency, namely 53 and 212 MHz, and compare the electron cloud density for these two frequencies at fixed total beam intensity. We contrast the MI results against those from a similar simulation for the PS2, the first storage ring in the proposed future upgrade of the LHC injector complex. Time permitting, we will briefly comment on effects from the electron cloud on the beam dynamics.
LANL, Los Alamos, New Mexico
TechSource, Santa Fe, New Mexico
Recent beam studies have focused on understanding the main sources and locations of electron clouds (EC) which drive the observed e-p instability at the PSR. New results using a recently developed electron diagnostic will be reported which demonstrate the important role of EC activity in quadrupole magnets, including definitive evidence that ~80% or more of the drift space EC signal is “seeded” by electrons ejected by ExB drifts from adjacent quadrupole magnets*. Other observations include distinctive brown colored tracking in various dipole and quadrupole vacuum chambers, which we hypothesize is caused by energetic electrons striking the wall during beam-induced multipacting. The tracking observations point to a simple and useful signature for regions of EC activity. Modeling of EC observations using a modified version of the POSINST** code shows general agreement on many features of the observations, given the large uncertainties in the distribution of seed electrons from beam loss which is a key input into the simulations. Progress will be reported on resolving the features not in agreement.
* R. Macek et al, PRSTAB, 11, 010101 (2008).
** M. T. F. Pivi and M. A. Furman, PRSTAB, 6, 034201 (2003).
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.
Fermilab, Batavia, Illinois
The stable region of the Fermilab Booster beam in the complex coherent-tune-shift plane appears to have been shifted far away from the origin by its intense space charge making Landau damping appear impossible. However, it is shown that the bunching structure of the beam reduces this space-charge shift. As a result, the beam can be stabilized by suitable octupole driven tune spread.
ORNL, Oak Ridge, Tennessee
With the increase of average power of present and future high intensity proton rings and rapid progress of laser technology, laser-assisted stripping become a real alternative for carbon foils that are used for charge-exchange injection. High efficiency laser stripping, achieved experimentally at Spallation Neutron Source in Oak Ridge, TN, paved the way to full scale devices of such type. This paper presents overview of machines and choices of parameters for future powerful accelerators with possible laser stripping use.
Fermilab, Batavia, Illinois
The Fermilab Project X R&D program is focused on the design of a new proton source utilizing a superconducting linac to accelerate H-minus ions to 8 GeV (K.E) for injection and accumulation into the permanent magnet Recycler ring. The initial linac runs at a 5 Hz rep-rate with a 1 ms pulse length and 9 mA average current which produce a beam power of 360 kW at 8 GeV. This beam power will provide 2.3 MW at 120 GeV from the Main Injector in addition to 200 kW at 8 GeV for an 8 GeV physics program. The challenges faced with the transport and injection of 8 GeV H- will be discussed. The topics will include uncontrolled beam losses and their mitigation in both the transport and injection processes, injection stripping options, and transverse phase space painting options. A review of the issues that have been highlighted and addressed by numerous authors will be presented. The current plans for continued R&D on H- stripping mechanisms and techniques and in collimation and absorber design will be outlined and initial concepts of the design will be discussed. Upgrade plans for Project X call for a 2 MW facility at 8 GeV. The additional challenges faced in the upgrade will be outlined.
BNL, Upton, Long Island, New York
MIT, Middleton, Massachusetts
The design status of the high luminosity electron-ion collider, eRHIC, is presented. The goal of eRHIC will be to provide collisions of electrons and possibly positrons) on ions and protons in the center-of-mass energy range from 25 to 140 GeV, at luminosities exceeding 1033 cm-2s-1. A considerable part of the physics program calls for a high polarization level of electrons, protons and He3 ions. The electron beam is accelerated in a recirculating energy recovery linac. Major R&D items for the electron beam include the development of a high intensity polarized source, studies of various aspects of energy recovery technology for high power beams and the development of compact magnets for recirculating passes. In a linac-ring scheme the beam-beam interaction has several very specific features which have to be thoroughly studied. In order to maximize the collider luminosity, several upgrades of the existing RHIC accelerator are required. Those upgrades may include the increase of total beam intensity as well as transverse and longitudinal cooling of ions and protons.
Jefferson Lab, Newport News, Virginia
TRIUMF, Vancouver
A conceptual design of a ring-ring electron-ion collider based on CEBAF with a center-of-mass energy up to 90 GeV at luminosity up to 1035 cm-2s-1 has been proposed at JLab to fulfil science requirements. Four interaction points on two crossing straight sections of Figure-8 shape rings are planed for collisions of both highly polarized electron and light ion beams. The Green field design of the ion complex including electron cooling and new way of organizing interacting regions are directly aimed at full exploitation of science program. Here, we summarize design progress including collider ring and interaction region optics with chromatic aberration compensation. Stacking of ion beams in an accumulator-cooler ring, beam-beam simulations and a faster kicker for the circulator electron cooler ring are also discussed.
Fermilab, Batavia, Illinois
High intense hadron beams of > 2 MW beam power are a key element for the new proposed Neutrino experiments at Fermilab. Therefore a new beam facility, called Project-X, is under discussion. We will present requirements, and first conceptual ideas for beam instrumentation and diagnostics, and the related R&D initiatives taking place in the high intense test accelerators, currently under construction. First results of beam profile measurements using OTR screens and laser wires are shown.
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.