J.S. Berg

Design of FFAGs based on a FODO lattice

An FFAG is a lattice with fixed magnetic fields that has an extremely wide energy acceptance. One particularly simple type of FFAG is based on a FODO lattice, where both quads can be combined-function bending/quadrupole magnets. The spaces between the combined-function magnets are left open for RF cavities and other hardware. This paper describes a general method for creating lattice designs for this type of lattice which gives the lattice optimal properties for an FFAG accelerator. The properties of this lattice as a function of input parameters are explored. The use of sextupoles to improve lattice properties is also explored.

Muon cooling in the RFOFO ring cooler

The performance of the ring described here compares favorably with the linear cooling channel used in the second U.S. Neutrino Factory Study [ref.1]. The 6D phase space density of an idealized ring is increased by a factor of 238, compared with the linear channels factor of only 15. The simulations make use of fully realistic magnetic fields, and include absorber and rf cavity windows, and empty lattice cells for injection/extraction.

RFOFO RING COOLER.

This note describes the design of an ionization cooling ring that uses an alternating polarity solenoid lattice. The ring is approximately 33 m in circumference and has 12 cells. Each cell has two opposing focusing solenoids placed either side of a hydrogen wedge absorber. The solenoid coils are located outside pillbox rf cavities. Bending is provided by tipping the solenoid coils. The simulated merit factor (≈ the increase in six-dimensional phase-space density) is 81.

RFOFO Cooling Ring: Simulation Results

Practical cooling rings could lead to lower cost or improved performance in neutrino factory or muon collider designs. The ring modeled here uses realistic 3‐dimensional fields and includes such “real‐world” effects as windows on the absorbers and RF cavities and leaving empty lattice cells for injection and extraction. The ring increases the density of muons in a fixed acceptance volume by a factor of 4.2.

FFAG lattice for muon acceleration with distributed RF

A future muon collider or neutrino factory requires fast acceleration to minimize muon decay. We have previously described an FFAG ring that accelerated muons from 10 to 20 GeV in energy. The ring achieved its large momentum acceptance using a low-emittance lattice with a small dispersion. In this paper, we present an update on that ring. We have used design tools that more accurately represent the rings behavior at large momentum offsets. We have also improved the dynamic aperture from the earlier design.

Muon acceleration with a very fast ramping synchrotron for a neutrino factory

A 4600 Hz fast ramping synchrotron is explored as an economical way of accelerating muons from 4 to 20 GeV/c for a neutrino factory. Eddy current losses are minimized by the low machine duty cycle plus thin grain oriented silicon steel laminations and thin copper wires. Combined function magnets with high gradients alternating within single magnets form the lattice we describe. Muon survival is 83%.

Meson Production Simulations for a Mercury Jet Target

A study of target parameters for a high‐power, liquid mercury jet target system for a neutrino factory or muon collider is presented. Using the MARS15 code, we simulate particle production initiated by incoming protons below the jet with kinetic energies between 2 and 100 GeV. For each proton beam energy, we maximize production by varying the geometric parameters of the target: the mercury jet radius, the incoming proton beam angle, and the crossing angle between the mercury jet and the proton beam. With an 8 GeV proton beam, we study the variation of meson production with the direction of the proton beam relative to the jet.

Linear model for nonisosceles absorbers

Previous analyses have assumed that wedge absorbers are triangularly shaped with equal angles for the two faces. In this case, to linear order, the energy loss depends only on the position in the direction of the face tilt, and is independent of the incoming angle. One can instead construct an absorber with entrance and exit faces facing rather general directions. In this case, the energy loss can depend on both the position and the angle of the particle in question. This paper demonstrates that and computes the effect to linear order.

Linear design of combined-function ionization cooling lattices

Ionization cooling lattices simultaneously require small beta-functions at the absorber and large energy acceptances to be effective. Simultaneously achieving these goals as well as having a good dynamic aperture requires that the lattice be relatively compact. If one wishes to avoid solenoids, one choice for creating such a lattice is to use combined-function magnets. These magnets can simultaneously focus in both planes, allowing one to achieve a low beta in both planes with a minimum number of magnets. In this paper we explore the design of lattices which contain only combined-function bending magnets using a thin-lens approximation, showing how to optimally achieve the requirements for muon cooling.

End field effects in bend-only cooling lattices

Cooling lattices consisting only of bends (using either rotated pole faces or gradient dipoles to achieve focusing) often require large apertures and short magnets. One expects the effect of end fields to be significant in this case. In this paper we explore the effect of adding end fields to a working lattice design that originally lacked them. The paper describes the process of correcting the lattice design for the added end fields so as to maintain desirable lattice characteristics. It then compares the properties of the lattice with end fields relative to the lattice without them.