IPAC2012 - List of Authors (Alexahin, Y.)

Paper	Title	Page
TUPPC041	A 3 TeV Muon Collider Lattice Design	1254
	Y. Alexahin, E. Gianfelice-Wendt Fermilab, Batavia, USA
	Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy A new lattice for 3 TeV c.o.m. energy with β^=5mm was developed which follows the basic concept of the earlier 1.5 TeV design but uses quad triplets for the final focus in order to keep the maximum magnet strength and aperture about the same as in 1.5 TeV case. Another difference is employment of combined-function magnets with the goal to lower heat deposition in magnet cold mass and to eliminate regions without bending field which produce “hot spots” of neutrino radiation that can be an issue at higher energy. The proposed lattice is shown to satisfy the requirements on luminosity, dynamic aperture and momentum acceptance. * Y.Alexahin, E.Gianfelice-Wendt, A.Netepenko, Proc. IPAC10, Kyoto, May 2010, p. 1563

TUPPC042	Effect of Field Errors in Muon Collider IR Magnets on Beam Dynamics	1257
	Y. Alexahin, E. Gianfelice-Wendt, V.V. Kapin Fermilab, Batavia, USA
	Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy In order to achieve peak luminosity of a Muon Collider (MC) in the 10³⁵/cm²/s range very small values of beta-function at the interaction point (IP) are necessary (β^* ~ 5 mm) while the distance from IP to the first quadrupole can not be made shorter than ~6m as dictated by the necessity of detector protection from backgrounds. In the result the beta-function at the final focus quadrupoles can reach 100 km making beam dynamics very sensitive to all kind of errors. In the present report we consider the effects on momentum acceptance and dynamic aperture of multipole field errors in the body of IR dipoles as well as of fringe-fields in both dipoles and quadrupoles in the case of 1.5 TeV (c.o.m.) MC. Analysis shows these effects to be strong but correctable with dedicated multipole correctors.

TUPPC043	Design of Accumulator and Compressor Rings for the Project-X Based Proton Driver	1260
	Y. Alexahin, D.V. Neuffer Fermilab, Batavia, USA
	Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy. A Muon Collider (MC) and Neutrino Factory (NF), which may be considered as a step towards MC, both require high-power (~4 MW) proton driver providing short (<1m) bunches for muon production. However, the driver repetition rate required for these two machines is different: ~15 Hz for MC and ~60 Hz for NF. This difference necessitates employing two separate rings: one for accumulation of the proton beam from the Project-X linac in a few (e.g., 4) long bunches, the other for bunch compression - one by one for NF or all at a time for MC with simultaneous delivery to the target. The lattice requirements for these two rings are different: the momentum compaction factor in the accumulator ring should be large (and possibly negative) to avoid the microwave instability, while the compressor ring can be nearly isochronous in order to limit the required RF voltage and reduce the dispersion contribution to the beam size. In the present report we consider ring lattice designs which achieve these goals.

WEPPR004	Effect of Beam-beam Interactions on Stability of Coherent Oscillations in a Muon Collider	2940
	K. Ohmi KEK, Ibaraki, Japan Y. Alexahin Fermilab, Batavia, USA
	In order to achieve the peak luminosity of a muon collider in the 10³⁵ cm^-2 s^-1 range the number of muons per bunch should be of the order of a few units of 10¹² rendering the beam-beam parameter as high as 0.1 per IP. Such strong beam-beam interaction can be a source of instability if the working point is chosen close to a coherent beam-beam resonance. On the other hand, the beam-beam tune spread can provide a mechanism of suppression of the beam-wall driven instabilities. In this report the coherent instabilities driven by beam-beam and beam-wall interactions are studied with the help of BBSS code for the case of 1.5 TeV c.o.m muon collider.

WEPPR085	Observation of Instabilities of Coherent Transverse Ocillations in the Fermilab Booster	3129
	Y. Alexahin, N. Eddy, E. Gianfelice-Wendt, V.A. Lebedev, W.L. Marsh, W. Pellico, A.K. Triplett Fermilab, Batavia, USA
	Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy. The Fermilab Booster - built more than 40 years ago - operates well above the design proton beam intensity of 4.e12 ppp. Still, the Fermilab neutrino experiments call for even higher intensity of 5.5·10¹² ppp. A multitude of intensity related effects must be overcome in order to meet this goal including suppression of coherent dipole instabilities of transverse oscillations which manifest themselves as a sudden drop in the beam current. In this report we present the results of observation of these instabilities at different tune, coupling and chromaticity settings and discuss possible cures.

THPPD035	Magnets for Interaction Regions of a 1.5×1.5 TeV Muon Collider	3584
	V. Kashikhin, Y. Alexahin, N.V. Mokhov, A.V. Zlobin Fermilab, Batavia, USA
	Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy The updated IR optics and conceptual designs of large aperture superconducting quadrupole magnets for a muon collider with a c.o.m. energy of 3 TeV and an average luminosity of 4·10³⁴ cm^-2 s^-1 are presented. All magnets are based on the Nb3Sn superconductor and designed to provide an adequate operation field gradient in the given aperture with the critical current margin required for reliable machine operation. Special dipole coils were added to quadrupole designs to provide ~2 T bending field and thus facilitate chromaticity correction and dilute decay electron fluxes on the detector. Magnet cross-sections were optimized to achieve the best possible field quality in the magnet aperture occupied with beams. Magnet parameters are reported and compared with the requirements. Energy deposition calculations with the MARS code have allowed to optimize parameters of inner absorbers, collimators in interconnect regions and Machine-Detector Interface.

THPPD036	High-Field Combined-Function Magnets for a 1.5×1.5 TeV Muon Collider Storage Ring	3587
	V. Kashikhin, Y. Alexahin, N.V. Mokhov, A.V. Zlobin Fermilab, Batavia, USA
	Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy A new storage ring lattice based on combined function high-field magnets and conceptual designs of superconducting magnets with dipole and quadrupole coils for a muon collider with a c.o.m. energy of 3 TeV and an average luminosity of 4x10³⁴ cm^-2 s^-1 are presented. Magnets are designed to provide the required focusing field gradient and bending field in the aperture with the appropriate operation margin. Magnets have large apertures to provide an adequate space for internal absorbers, vacuum insulation, beam pipe, and helium channel. Coil cross-sections were optimized to achieve the best possible field quality in the magnet aperture occupied with beams. Magnet parameters are reported and compared with the requirements. Energy deposition calculations with the MARS code have allowed to optimize parameters of inner absorbers and collimators in interconnect regions, thus reducing peak power density and dynamic loads to the tolerable levels.

THPPP019	Tune Determination of Strongly Coupled Betatron Oscillations in a Fast Ramping Synchrotron	3770
	Y. Alexahin, E. Gianfelice-Wendt, W.L. Marsh, A.K. Triplett Fermilab, Batavia, USA
	Funding: Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. Tune identification - i.e. attribution of the spectral peak to a particular normal mode of oscillations - can present a significant difficulty in the presence of strong transverse coupling when the normal mode with a lower damping rate dominates spectra of Turn-by-Turn oscillations in both planes. The introduced earlier phased sum algorithm* helped to recover the weaker normal mode signal from the noise, but by itself proved to be insufficient for automatic peak identification in the case of close phase advance distribution in both planes. To resolve this difficulty we modified the algorithm by taking and analyzing Turn-by-Turn data for two different ramps with the beam oscillation excited in each plane in turn. Comparison of the relative amplitudes of Fourier components allows for automatic correct tune identiﬁcation. The proposed algorithm was implemented in the Fermilab Booster B38 console application and successfully used in tune, coupling and chromaticity measurements. * Y. Alexahin, E. Gianfelice-Wendt, W. Marsh, Proc. IPAC10, Kyoto, May 2010, p. 1179.

Paper

Title

Page

A 3 TeV Muon Collider Lattice Design

1254

Y. Alexahin, E. Gianfelice-Wendt
Fermilab, Batavia, USA

Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy
A new lattice for 3 TeV c.o.m. energy with β^*=5mm was developed which follows the basic concept of the earlier 1.5 TeV design* but uses quad triplets for the final focus in order to keep the maximum magnet strength and aperture about the same as in 1.5 TeV case. Another difference is employment of combined-function magnets with the goal to lower heat deposition in magnet cold mass and to eliminate regions without bending field which produce “hot spots” of neutrino radiation that can be an issue at higher energy. The proposed lattice is shown to satisfy the requirements on luminosity, dynamic aperture and momentum acceptance.
* Y.Alexahin, E.Gianfelice-Wendt, A.Netepenko, Proc. IPAC10, Kyoto, May 2010, p. 1563

TUPPC042

Effect of Field Errors in Muon Collider IR Magnets on Beam Dynamics

1257

Y. Alexahin, E. Gianfelice-Wendt, V.V. Kapin
Fermilab, Batavia, USA

Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy
In order to achieve peak luminosity of a Muon Collider (MC) in the 10³⁵/cm²/s range very small values of beta-function at the interaction point (IP) are necessary (β^* ~ 5 mm) while the distance from IP to the first quadrupole can not be made shorter than ~6m as dictated by the necessity of detector protection from backgrounds. In the result the beta-function at the final focus quadrupoles can reach 100 km making beam dynamics very sensitive to all kind of errors. In the present report we consider the effects on momentum acceptance and dynamic aperture of multipole field errors in the body of IR dipoles as well as of fringe-fields in both dipoles and quadrupoles in the case of 1.5 TeV (c.o.m.) MC. Analysis shows these effects to be strong but correctable with dedicated multipole correctors.

TUPPC043

Design of Accumulator and Compressor Rings for the Project-X Based Proton Driver

1260

Y. Alexahin, D.V. Neuffer
Fermilab, Batavia, USA

Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy.
A Muon Collider (MC) and Neutrino Factory (NF), which may be considered as a step towards MC, both require high-power (~4 MW) proton driver providing short (<1m) bunches for muon production. However, the driver repetition rate required for these two machines is different: ~15 Hz for MC and ~60 Hz for NF. This difference necessitates employing two separate rings: one for accumulation of the proton beam from the Project-X linac in a few (e.g., 4) long bunches, the other for bunch compression - one by one for NF or all at a time for MC with simultaneous delivery to the target. The lattice requirements for these two rings are different: the momentum compaction factor in the accumulator ring should be large (and possibly negative) to avoid the microwave instability, while the compressor ring can be nearly isochronous in order to limit the required RF voltage and reduce the dispersion contribution to the beam size. In the present report we consider ring lattice designs which achieve these goals.

WEPPR004

Effect of Beam-beam Interactions on Stability of Coherent Oscillations in a Muon Collider

2940

K. Ohmi
KEK, Ibaraki, Japan
Y. Alexahin
Fermilab, Batavia, USA

In order to achieve the peak luminosity of a muon collider in the 10³⁵ cm^-2 s^-1 range the number of muons per bunch should be of the order of a few units of 10¹² rendering the beam-beam parameter as high as 0.1 per IP. Such strong beam-beam interaction can be a source of instability if the working point is chosen close to a coherent beam-beam resonance. On the other hand, the beam-beam tune spread can provide a mechanism of suppression of the beam-wall driven instabilities. In this report the coherent instabilities driven by beam-beam and beam-wall interactions are studied with the help of BBSS code for the case of 1.5 TeV c.o.m muon collider.

WEPPR085

Observation of Instabilities of Coherent Transverse Ocillations in the Fermilab Booster

3129

Y. Alexahin, N. Eddy, E. Gianfelice-Wendt, V.A. Lebedev, W.L. Marsh, W. Pellico, A.K. Triplett
Fermilab, Batavia, USA

Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy.
The Fermilab Booster - built more than 40 years ago - operates well above the design proton beam intensity of 4.e12 ppp. Still, the Fermilab neutrino experiments call for even higher intensity of 5.5·10¹² ppp. A multitude of intensity related effects must be overcome in order to meet this goal including suppression of coherent dipole instabilities of transverse oscillations which manifest themselves as a sudden drop in the beam current. In this report we present the results of observation of these instabilities at different tune, coupling and chromaticity settings and discuss possible cures.

THPPD035

Magnets for Interaction Regions of a 1.5×1.5 TeV Muon Collider

3584

V. Kashikhin, Y. Alexahin, N.V. Mokhov, A.V. Zlobin
Fermilab, Batavia, USA

Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy
The updated IR optics and conceptual designs of large aperture superconducting quadrupole magnets for a muon collider with a c.o.m. energy of 3 TeV and an average luminosity of 4·10³⁴ cm^-2 s^-1 are presented. All magnets are based on the Nb3Sn superconductor and designed to provide an adequate operation field gradient in the given aperture with the critical current margin required for reliable machine operation. Special dipole coils were added to quadrupole designs to provide ~2 T bending field and thus facilitate chromaticity correction and dilute decay electron fluxes on the detector. Magnet cross-sections were optimized to achieve the best possible field quality in the magnet aperture occupied with beams. Magnet parameters are reported and compared with the requirements. Energy deposition calculations with the MARS code have allowed to optimize parameters of inner absorbers, collimators in interconnect regions and Machine-Detector Interface.

THPPD036

High-Field Combined-Function Magnets for a 1.5×1.5 TeV Muon Collider Storage Ring

3587

V. Kashikhin, Y. Alexahin, N.V. Mokhov, A.V. Zlobin
Fermilab, Batavia, USA

Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy
A new storage ring lattice based on combined function high-field magnets and conceptual designs of superconducting magnets with dipole and quadrupole coils for a muon collider with a c.o.m. energy of 3 TeV and an average luminosity of 4x10³⁴ cm^-2 s^-1 are presented. Magnets are designed to provide the required focusing field gradient and bending field in the aperture with the appropriate operation margin. Magnets have large apertures to provide an adequate space for internal absorbers, vacuum insulation, beam pipe, and helium channel. Coil cross-sections were optimized to achieve the best possible field quality in the magnet aperture occupied with beams. Magnet parameters are reported and compared with the requirements. Energy deposition calculations with the MARS code have allowed to optimize parameters of inner absorbers and collimators in interconnect regions, thus reducing peak power density and dynamic loads to the tolerable levels.

THPPP019

Tune Determination of Strongly Coupled Betatron Oscillations in a Fast Ramping Synchrotron

3770

Y. Alexahin, E. Gianfelice-Wendt, W.L. Marsh, A.K. Triplett
Fermilab, Batavia, USA

Funding: Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Tune identification - i.e. attribution of the spectral peak to a particular normal mode of oscillations - can present a significant difficulty in the presence of strong transverse coupling when the normal mode with a lower damping rate dominates spectra of Turn-by-Turn oscillations in both planes. The introduced earlier phased sum algorithm* helped to recover the weaker normal mode signal from the noise, but by itself proved to be insufficient for automatic peak identification in the case of close phase advance distribution in both planes. To resolve this difficulty we modified the algorithm by taking and analyzing Turn-by-Turn data for two different ramps with the beam oscillation excited in each plane in turn. Comparison of the relative amplitudes of Fourier components allows for automatic correct tune identiﬁcation. The proposed algorithm was implemented in the Fermilab Booster B38 console application and successfully used in tune, coupling and chromaticity measurements.
* Y. Alexahin, E. Gianfelice-Wendt, W. Marsh, Proc. IPAC10, Kyoto, May 2010, p. 1179.