Alper Garren

High Field HTS R&D Solenoid for Muon Collider

This paper presents the goal and status of the high field High Temperature Superconductor (HTS) solenoid program funded through a series of SBIRs. The target of this R&D program is to build HTS coils that are capable of producing fields greater than 20 T when tested alone and approaching 40 T when tested in a background field magnet. The solenoid will be made with second generation (2G) high engineering current density HTS tape. To date, 17 HTS pancake coils have been built and tested in the temperature range from 20 K to 80 K. Quench protection, high stresses and minimization of degradation of conductor are some of the major challenges associated with this program.

High Field HTS Solenoid for a Muon Collider—Demonstrations, Challenges, and Strategies

The proposed muon collider requires very high field solenoids in the range of 30-50 T. The use of High Temperature Superconductors (HTS) operating at low temperature (~ 4 K) is essential for achieving such high fields in a superconducting magnet. As a part of this program, we have built and successfully tested a 25 mm aperture HTS insert generating 16 T peak field (the highest field ever achieved in an all-HTS magnet), a 100 mm aperture HTS midsert generating 9 T peak field, and designed an outsert with a conventional Low Temperature Superconductor (LTS) to provide additional field. In addition to presenting the test results and progress made in support technologies, we will also discuss a number of challenges associated with the high field HTS magnets. Finally, we present a set of strategies to overcome some of those challenges.

A comparison of several lattice tools for computation of orbit functions of an accelerator

The values of orbit functions for accelerator lattices as computed with accelerator design programs may differ between different programs. For a simple lattice, consisting of identical constant-gradient bending magnets, the functions (horizontal and vertical betatron tunes, dispersions, closed orbit offsets, orbit lengths, chromaticities etc.) can be evaluated analytically. This lattice was studied with the accelerator physics tools SYNCH [1], COSY INFINITY [2], MAD [3], and TEAPOT [4]. It was found that while all the programs give identical results at the central design momentum, the results differ substantially among the various lattice tools for non-zero momentum deviations. Detailed results and comparisons are presented.

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.

A MUON COOLING RING WITH LITHIUM LENSES

We discuss particle tracking simulations in a storage ring with Lithium lens inserts designed for the transverse phase space cooling of muons by the ionization cooling. In a hard-edged magnetic element model, we demonstrate the equilibrium normalized transverse emittance of 0.3 mm*rad which is necessary for a Higgs Factory, a low energy mu+mu- Collider. For the 6 dimensional phase space cooling of muons, a method of using bent Lithium lenses were discussed.

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.

A very fast ramping muon synchrotron for a neutrino factory

A 4600 Hz fast ramping synchrotron is studied 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. Muon survival is 83%.