IPAC2012 - List of Authors (Tsoupas, N.)

Paper

Title

Page

Modelling of the AGS Using Zgoubi - Status

181

F. Méot, L. A. Ahrens, Y. Dutheil, J.W. Glenn, H. Huang, T. Roser, V. Schoefer, N. Tsoupas
BNL, Upton, Long Island, New York, USA

A computer model, based on the ray-tracing code Zgoubi, is being developed in view of on-line simulation of the RHIC injector AGS, and of beam and spin dynamics simulations and studies in the presence of the cold and warm helical partial snakes. A status of this work is given here.

MOPPC025

RHIC Polarized Proton Operation in Run 12

184

V. Schoefer, L. A. Ahrens, A. Anders, E.C. Aschenauer, G. Atoian, M. Bai, J. Beebe-Wang, M. Blaskiewicz, J.M. Brennan, K.A. Brown, D. Bruno, R. Connolly, T. D'Ottavio, A. Dion, K.A. Drees, W. Fischer, C.J. Gardner, J.W. Glenn, X. Gu, M. Harvey, T. Hayes, L.T. Hoff, H. Huang, R.L. Hulsart, A. Kirleis, J.S. Laster, C. Liu, Y. Luo, Y. Makdisi, G.J. Marr, A. Marusic, F. Méot, K. Mernick, R.J. Michnoff, M.G. Minty, C. Montag, J. Morris, S. Nemesure, A. Poblaguev, V. Ptitsyn, V.H. Ranjbar, G. Robert-Demolaize, T. Roser, W.B. Schmidke, F. Severino, D. Smirnov, K.S. Smith, D. Steski, S. Tepikian, D. Trbojevic, N. Tsoupas, J.E. Tuozzolo, G. Wang, M. Wilinski, K. Yip, A. Zaltsman, A. Zelenski, K. Zeno, S.Y. Zhang
BNL, Upton, Long Island, New York, USA

Successful RHIC operation with polarized protons requires meeting demanding and sometimes competing goals for maximizing both luminosity and beam polarization. In Run 12 we sought to fully integrate into operation the many systems that were newly commissioned in Run 11 as well as to enhance collider performance with incremental improvements throughout the acceleration cycle. For luminosity maximization special attention was paid to several possible source of emittance dilution along the injector chain, in particular to optical matching during transfer between accelerators. Possible sources of depolarization in the AGS and RHIC were also investigated including the effects of local coupling and low frequency (10 Hz) oscillations in the vertical equilibrium orbit during the RHIC ramp. The results of a fine storage energy scan made in an effort to improve store polarization lifetime are also reported in this note.

TUPPC062

Transfer of Polarized 3He Ions in the AtR Beam Transfer Line

1317

N. Tsoupas, W.W. MacKay, F. Méot, T. Roser, D. Trbojevic
BNL, Upton, Long Island, New York, USA

Funding: Work supported by the US Department of Energy
In addition to collisions of electrons with various unpolarized ion species as well as polarized protons, the proposed electron-hadron collider (eRHIC) will also facilitate the collisions of electrons with polarized 3He ions. The AGS is the last acceleration stage of ions before injection into one RHIC for final acceleration. The AtR (AGS to RHIC) transfer line will be utilized to transport the polarized 3He ions from AGS into one of the RHIC’s collider rings. In this paper we investigate the extraction energy of the polarized 3He ions from the AGS which will optimize the polarization of 3He ions injected into RHIC. Some of the peculiarities (interleaved horizontal and vertical bends) of the AtR line's layout may degrade this spin matching of the polarized 3He ions. We will also discuss possible simple modifications of the AtR line to accomplish a perfect “spin matching” of the injected 3He beam with that of the stable spin direction at the injection point of the RHIC ring.

TUPPC063

The AGS Synchrotron with Four Helical Magnets

1320

N. Tsoupas, H. Huang, W.W. MacKay, T. Roser, D. Trbojevic
BNL, Upton, Long Island, New York, USA

Funding: *Work supported by the US Department of Energy.
The idea* of using two partial helical magnets was applied successfully to the AGS synchrotron**, to preserve the proton beam polarization. In this paper we explore in details the idea of using four helical magnets placed symmetrically in the AGS ring. This modification provides many advantages over the present setup of the AGS that uses two partial helical magnets. First, the symmetric placement of the four helical magnets allows for a better control of the AGS optics with reduced values of the beta functions especially near beam injection, second, the vertical spin direction during beam injection and extraction is closer to vertical, and third, it provides a larger “spin tune gap” for the placement of both the vertical and horizontal tunes of the AGS during acceleration, second. Although the same spin gap can be obtained with two partial helices of equal strength, the required strength of the two helices makes it impractical. In this paper we will provide results on the spin tune and on the optics of the AGS with four partial helical magnets, and comparison of these results with the present setup of the AGS that uses two partial helical magnets***.
* T. Roser et al., Proc. EPAC04, p. 1577 (2004).
** H. Huang et al., PRL 99, 154801(2007).
*** N. Tsoupas et. al., these proceedings.

TUPPC101

A Model of the AGS Based on Stepwise Ray-Tracing Through the Measured Field Maps of the Main Magnets

1395

Y. Dutheil, F. Méot, N. Tsoupas
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Two dimensional mid-plane magnetic field maps of two of the main AGS magnets were produced, from Hall probe measurements, for a series of different current settings. The analysis of these data yielded the excitation functions and harmonic coefficients of the main magnets [BNL TN 424 & TN 429] which have been used so far in all the models of the AGS. The constant increase of computation power makes it possible today to directly use stepwise ray-tracing through these measured field maps with a reasonable computation time. We describe in detail how these field maps have allowed generation of models of the 6 different types of AGS main magnets, and how they are being handled with the Zgoubi ray-tracing code. We give and discuss a number of results so obtained regarding both beam and spin dynamics in the AGS, and provide comparisons with other numerical and analytical modeling methods.

TUXA03

Increasing the AGS Beam Polarization with 80 Tune Jumps

1015

V. Schoefer, L. A. Ahrens, M. Bai, E.D. Courant, W. Fu, C.J. Gardner, J.W. Glenn, H. Huang, F. Lin, A.U. Luccio, J.-L. Mi, J. Morris, P.J. Rosas, T. Roser, P. Thieberger, N. Tsoupas, A. Zelenski, K. Zeno
BNL, Upton, Long Island, New York, USA

Vertical depolarizing resonances in the AGS are removed by partial Siberian snakes. These magnets move the stable spin direction and lead to horizontal depolarizing resonances. The tune jump quadrupole system increases the crossing rate for horizontal resonances by a factor of six. This presentation will review the fundamental mechanism of depolarizing resonances, the partial Siberian snake solution and describe recent experimental evidence at the AGS demonstrating improvements to beam polarization and the beam dynamics challenges posed by the tune jump.

Slides TUXA03 [5.199 MB]

THPPP030

Near Integer Tune for Polarization Preservation in the AGS

3797

N. Tsoupas, L. A. Ahrens, M. Bai, K.A. Brown, J.W. Glenn, H. Huang, W.W. MacKay, T. Roser, V. Schoefer, K. Zeno
BNL, Upton, Long Island, New York, USA

Funding: *Work supported by the US Department of Energy.
The high energy (T=250 GeV) polarized proton beam experiments performed in RHIC, require high polarization of the beam. In order to preserve the polarization of the proton beam, during the acceleration in the AGS, which is the pre-injector to RHIC, two partial helical magnets* have been installed in AGS. In order to minimize the loss of the beam polarization due to the various intrinsic spin resonances occurring during the proton acceleration, we constrain the value of the vertical tune to be higher than 8.97. With the AGS running at near integer tune the perturbations caused by the partial helical magnets is large resulting in large beta and dispersion waves. To mitigate the adverse effect of the partial helices on the optics of the AGS, we have introduced compensation quads** in AGS. In this paper we present the beam optics of the AGS which ameliorates this effect of the partial helices.
* H. Huang, et al., Proc. EPAC06, p. 273, (2006).
** N. Tsoupas et al., Proc. PAC07, p. 3723 (2007).

Paper	Title	Page
MOPPC024	Modelling of the AGS Using Zgoubi - Status	181
	F. Méot, L. A. Ahrens, Y. Dutheil, J.W. Glenn, H. Huang, T. Roser, V. Schoefer, N. Tsoupas BNL, Upton, Long Island, New York, USA
	A computer model, based on the ray-tracing code Zgoubi, is being developed in view of on-line simulation of the RHIC injector AGS, and of beam and spin dynamics simulations and studies in the presence of the cold and warm helical partial snakes. A status of this work is given here.

MOPPC025	RHIC Polarized Proton Operation in Run 12	184
	V. Schoefer, L. A. Ahrens, A. Anders, E.C. Aschenauer, G. Atoian, M. Bai, J. Beebe-Wang, M. Blaskiewicz, J.M. Brennan, K.A. Brown, D. Bruno, R. Connolly, T. D'Ottavio, A. Dion, K.A. Drees, W. Fischer, C.J. Gardner, J.W. Glenn, X. Gu, M. Harvey, T. Hayes, L.T. Hoff, H. Huang, R.L. Hulsart, A. Kirleis, J.S. Laster, C. Liu, Y. Luo, Y. Makdisi, G.J. Marr, A. Marusic, F. Méot, K. Mernick, R.J. Michnoff, M.G. Minty, C. Montag, J. Morris, S. Nemesure, A. Poblaguev, V. Ptitsyn, V.H. Ranjbar, G. Robert-Demolaize, T. Roser, W.B. Schmidke, F. Severino, D. Smirnov, K.S. Smith, D. Steski, S. Tepikian, D. Trbojevic, N. Tsoupas, J.E. Tuozzolo, G. Wang, M. Wilinski, K. Yip, A. Zaltsman, A. Zelenski, K. Zeno, S.Y. Zhang BNL, Upton, Long Island, New York, USA
	Successful RHIC operation with polarized protons requires meeting demanding and sometimes competing goals for maximizing both luminosity and beam polarization. In Run 12 we sought to fully integrate into operation the many systems that were newly commissioned in Run 11 as well as to enhance collider performance with incremental improvements throughout the acceleration cycle. For luminosity maximization special attention was paid to several possible source of emittance dilution along the injector chain, in particular to optical matching during transfer between accelerators. Possible sources of depolarization in the AGS and RHIC were also investigated including the effects of local coupling and low frequency (10 Hz) oscillations in the vertical equilibrium orbit during the RHIC ramp. The results of a fine storage energy scan made in an effort to improve store polarization lifetime are also reported in this note.

TUPPC062	Transfer of Polarized 3He Ions in the AtR Beam Transfer Line	1317
	N. Tsoupas, W.W. MacKay, F. Méot, T. Roser, D. Trbojevic BNL, Upton, Long Island, New York, USA
	Funding: Work supported by the US Department of Energy In addition to collisions of electrons with various unpolarized ion species as well as polarized protons, the proposed electron-hadron collider (eRHIC) will also facilitate the collisions of electrons with polarized 3He ions. The AGS is the last acceleration stage of ions before injection into one RHIC for final acceleration. The AtR (AGS to RHIC) transfer line will be utilized to transport the polarized 3He ions from AGS into one of the RHIC’s collider rings. In this paper we investigate the extraction energy of the polarized 3He ions from the AGS which will optimize the polarization of 3He ions injected into RHIC. Some of the peculiarities (interleaved horizontal and vertical bends) of the AtR line's layout may degrade this spin matching of the polarized 3He ions. We will also discuss possible simple modifications of the AtR line to accomplish a perfect “spin matching” of the injected 3He beam with that of the stable spin direction at the injection point of the RHIC ring.

TUPPC063	The AGS Synchrotron with Four Helical Magnets	1320
	N. Tsoupas, H. Huang, W.W. MacKay, T. Roser, D. Trbojevic BNL, Upton, Long Island, New York, USA
	Funding: Work supported by the US Department of Energy. The idea of using two partial helical magnets was applied successfully to the AGS synchrotron, to preserve the proton beam polarization. In this paper we explore in details the idea of using four helical magnets placed symmetrically in the AGS ring. This modification provides many advantages over the present setup of the AGS that uses two partial helical magnets. First, the symmetric placement of the four helical magnets allows for a better control of the AGS optics with reduced values of the beta functions especially near beam injection, second, the vertical spin direction during beam injection and extraction is closer to vertical, and third, it provides a larger “spin tune gap” for the placement of both the vertical and horizontal tunes of the AGS during acceleration, second. Although the same spin gap can be obtained with two partial helices of equal strength, the required strength of the two helices makes it impractical. In this paper we will provide results on the spin tune and on the optics of the AGS with four partial helical magnets, and comparison of these results with the present setup of the AGS that uses two partial helical magnets. T. Roser et al., Proc. EPAC04, p. 1577 (2004). H. Huang et al., PRL 99, 154801(2007). * N. Tsoupas et. al., these proceedings.

TUPPC101	A Model of the AGS Based on Stepwise Ray-Tracing Through the Measured Field Maps of the Main Magnets	1395
	Y. Dutheil, F. Méot, N. Tsoupas BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Two dimensional mid-plane magnetic field maps of two of the main AGS magnets were produced, from Hall probe measurements, for a series of different current settings. The analysis of these data yielded the excitation functions and harmonic coefficients of the main magnets [BNL TN 424 & TN 429] which have been used so far in all the models of the AGS. The constant increase of computation power makes it possible today to directly use stepwise ray-tracing through these measured field maps with a reasonable computation time. We describe in detail how these field maps have allowed generation of models of the 6 different types of AGS main magnets, and how they are being handled with the Zgoubi ray-tracing code. We give and discuss a number of results so obtained regarding both beam and spin dynamics in the AGS, and provide comparisons with other numerical and analytical modeling methods.

TUXA03	Increasing the AGS Beam Polarization with 80 Tune Jumps	1015
	V. Schoefer, L. A. Ahrens, M. Bai, E.D. Courant, W. Fu, C.J. Gardner, J.W. Glenn, H. Huang, F. Lin, A.U. Luccio, J.-L. Mi, J. Morris, P.J. Rosas, T. Roser, P. Thieberger, N. Tsoupas, A. Zelenski, K. Zeno BNL, Upton, Long Island, New York, USA
	Vertical depolarizing resonances in the AGS are removed by partial Siberian snakes. These magnets move the stable spin direction and lead to horizontal depolarizing resonances. The tune jump quadrupole system increases the crossing rate for horizontal resonances by a factor of six. This presentation will review the fundamental mechanism of depolarizing resonances, the partial Siberian snake solution and describe recent experimental evidence at the AGS demonstrating improvements to beam polarization and the beam dynamics challenges posed by the tune jump.
	Slides TUXA03 [5.199 MB]

THPPP030	Near Integer Tune for Polarization Preservation in the AGS	3797
	N. Tsoupas, L. A. Ahrens, M. Bai, K.A. Brown, J.W. Glenn, H. Huang, W.W. MacKay, T. Roser, V. Schoefer, K. Zeno BNL, Upton, Long Island, New York, USA
	Funding: Work supported by the US Department of Energy. The high energy (T=250 GeV) polarized proton beam experiments performed in RHIC, require high polarization of the beam. In order to preserve the polarization of the proton beam, during the acceleration in the AGS, which is the pre-injector to RHIC, two partial helical magnets have been installed in AGS. In order to minimize the loss of the beam polarization due to the various intrinsic spin resonances occurring during the proton acceleration, we constrain the value of the vertical tune to be higher than 8.97. With the AGS running at near integer tune the perturbations caused by the partial helical magnets is large resulting in large beta and dispersion waves. To mitigate the adverse effect of the partial helices on the optics of the AGS, we have introduced compensation quads** in AGS. In this paper we present the beam optics of the AGS which ameliorates this effect of the partial helices. * H. Huang, et al., Proc. EPAC06, p. 273, (2006). ** N. Tsoupas et al., Proc. PAC07, p. 3723 (2007).