PAC2013 - List of Authors (Liu, C.)

Paper	Title	Page
TUPBA05	Implementation of Optics Correction on the Ramp in RHIC	529
	C. Liu, A. Marusic, M.G. Minty 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. In this report we describe and present experimental results from correction of the accelerator optics during acceleration and preparation for collisions at the Relativistic Heavy Ion Collider (RHIC) at BNL. Past experiences with beam optics correction at RHIC have concentrated on measurements and corrections at store beam energies. While well-corrected beam optics is desirable for maximizing beam and polarization lifetime, well-corrected beam optics during the ramp is also desirable for example to reduce the strength of depolarizing resonances. With optics measurements on the ramp at every 2 or 4 seconds, corrections were computed for several fixed points on the ramp using a well-tested weighted Singular Value Decomposition algorithm. Successful implementation of correction on the second part of the ramp (rotator ramp), together with some observations on the first part of the ramp (the energy ramp) will be presented.

TUPBA06	Global Optics Correction in RHIC Based on Turn-by-turn Data from ARTUS Tune Meter	532
	C. Liu, M. Blaskiewicz, K.A. Drees, W. Fischer, A. Marusic, M.G. Minty 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. Deviation of the optical functions from the model may result in reduced dynamic aperture, luminosity and beam polarization all of which are of particular interest in the polarized proton program at RHIC. Peak to peak beta-beats as large as ± 80% have been observed. In run-13, we demonstrated that the optical functions can be corrected globally by two different approaches, beta-beat and phase-beat corrections. The optics measurement, correction algorithm and beta-beat measurements before and after correction will be presented.

TUPBA08	Measurement of Beam Optics During Acceleration in the Relativistic Heavy Ion Collider	538
	M.G. Minty, K.A. Drees, R.L. Hulsart, C. Liu, A. Marusic, R.J. Michnoff, P. Thieberger 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. We describe a new and minimally invasive method for near real-time measurement of the evolution of critical beam optical parameters during acceleration of beams to high energies in the Relativistic Heavy Ion Collider (RHIC) at BNL. The implementation uses existing hardware to periodically excite a single bunch in the beam and leverages off of improved precision and deterministic data delivery from the RHIC beam position monitors operating in turn-by-turn mode. The beam response to the external excitations was observed to decohere on a relatively short time scale so allowing near-simultaneous data acquisition in the horizontal and vertical planes. The excitations and acquisitions are carefully timed to allow coexistence with normal ramp orbit feedback operating at a 1 Hz rate. Respecting the limitations of the data transfer times, important parameters such as the beta functions, local phase advance, and betatron tune spread were measured in both accelerators and both transverse planes at a maximum rate of once every 2 seconds / 4 seconds in each of the two RHIC accelerators respectively. The measurement architecture is described together with select experimental results.

TUPBA13	NS-FFAG for Electron-Ion Collider in RHIC (eRHIC)	553
	D. Trbojevic, J.S. Berg, S.J. Brooks, O.V. Chubar, Y. Hao, V. Litvinenko, C. Liu, W. Meng, F. Méot, B. Parker, V. Ptitsyn, T. Roser, N. Tsoupas, W.-T. Weng BNL, Upton, Long Island, New York, USA
	Funding: Work performed under Contract Number DE-AC02-98CH10886 with the auspices of the US Department of Energy. A future electron ion collider "QCD test facility" is designed in the present Relativistic Heavy Ion Collider (RHIC) tunnel. Electron acceleration and de-acceleration is preformed with energy recovery linac with multiple passes. We report on a combination of a multi-pass linac with the Non-Scaling Fixed Field Alternating Gradient (NS-FFAG) arcs. A single NS-FFAG arc allow electrons to pass through the same structure with an energy range between 1.425 and 10 GeV. The NS-FFAG is placed in the existing RHIC tunnel. The 200 MeV injector bring the polarized electrons to the 1.225 GeV GeV superconducting linac. After one pass through the linac 1.425 GeV electrons enter NS-FFAG arc and after 7 passes reach the energy of 10 GeV. After collisions the beam is brought back by the NS-FFAG and decelerated to the initial energy and directed to the dump.

THPAC13	Simulation and Optimization of Multi-Slit Based Emittance Measurement for BNL ERL	1166
	C. Liu, D.M. Gassner, D. Kayran, M.G. Minty, P. Thieberger 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. A code for determining the beam emittance from a multi-slit image has been developed. To verify its validity, we simulated a beam distribution in 4D phase space at the multi-slit position and the resulting image at a downstream profile measurement device. We applied the algorithm to this image pattern to recover the beam emittance at the slit position. The dependence of the relative difference of the inferred emittance and the input emittance on the slit width and drift length are studied in detail and presented in this report.

Paper

Title

Page

Implementation of Optics Correction on the Ramp in RHIC

529

C. Liu, A. Marusic, M.G. Minty
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.
In this report we describe and present experimental results from correction of the accelerator optics during acceleration and preparation for collisions at the Relativistic Heavy Ion Collider (RHIC) at BNL. Past experiences with beam optics correction at RHIC have concentrated on measurements and corrections at store beam energies. While well-corrected beam optics is desirable for maximizing beam and polarization lifetime, well-corrected beam optics during the ramp is also desirable for example to reduce the strength of depolarizing resonances. With optics measurements on the ramp at every 2 or 4 seconds, corrections were computed for several fixed points on the ramp using a well-tested weighted Singular Value Decomposition algorithm. Successful implementation of correction on the second part of the ramp (rotator ramp), together with some observations on the first part of the ramp (the energy ramp) will be presented.

TUPBA06

Global Optics Correction in RHIC Based on Turn-by-turn Data from ARTUS Tune Meter

532

C. Liu, M. Blaskiewicz, K.A. Drees, W. Fischer, A. Marusic, M.G. Minty
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.
Deviation of the optical functions from the model may result in reduced dynamic aperture, luminosity and beam polarization all of which are of particular interest in the polarized proton program at RHIC. Peak to peak beta-beats as large as ± 80% have been observed. In run-13, we demonstrated that the optical functions can be corrected globally by two different approaches, beta-beat and phase-beat corrections. The optics measurement, correction algorithm and beta-beat measurements before and after correction will be presented.

TUPBA08

Measurement of Beam Optics During Acceleration in the Relativistic Heavy Ion Collider

538

M.G. Minty, K.A. Drees, R.L. Hulsart, C. Liu, A. Marusic, R.J. Michnoff, P. Thieberger
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.
We describe a new and minimally invasive method for near real-time measurement of the evolution of critical beam optical parameters during acceleration of beams to high energies in the Relativistic Heavy Ion Collider (RHIC) at BNL. The implementation uses existing hardware to periodically excite a single bunch in the beam and leverages off of improved precision and deterministic data delivery from the RHIC beam position monitors operating in turn-by-turn mode. The beam response to the external excitations was observed to decohere on a relatively short time scale so allowing near-simultaneous data acquisition in the horizontal and vertical planes. The excitations and acquisitions are carefully timed to allow coexistence with normal ramp orbit feedback operating at a 1 Hz rate. Respecting the limitations of the data transfer times, important parameters such as the beta functions, local phase advance, and betatron tune spread were measured in both accelerators and both transverse planes at a maximum rate of once every 2 seconds / 4 seconds in each of the two RHIC accelerators respectively. The measurement architecture is described together with select experimental results.

TUPBA13

NS-FFAG for Electron-Ion Collider in RHIC (eRHIC)

553

D. Trbojevic, J.S. Berg, S.J. Brooks, O.V. Chubar, Y. Hao, V. Litvinenko, C. Liu, W. Meng, F. Méot, B. Parker, V. Ptitsyn, T. Roser, N. Tsoupas, W.-T. Weng
BNL, Upton, Long Island, New York, USA

Funding: Work performed under Contract Number DE-AC02-98CH10886 with the auspices of the US Department of Energy.
A future electron ion collider "QCD test facility" is designed in the present Relativistic Heavy Ion Collider (RHIC) tunnel. Electron acceleration and de-acceleration is preformed with energy recovery linac with multiple passes. We report on a combination of a multi-pass linac with the Non-Scaling Fixed Field Alternating Gradient (NS-FFAG) arcs. A single NS-FFAG arc allow electrons to pass through the same structure with an energy range between 1.425 and 10 GeV. The NS-FFAG is placed in the existing RHIC tunnel. The 200 MeV injector bring the polarized electrons to the 1.225 GeV GeV superconducting linac. After one pass through the linac 1.425 GeV electrons enter NS-FFAG arc and after 7 passes reach the energy of 10 GeV. After collisions the beam is brought back by the NS-FFAG and decelerated to the initial energy and directed to the dump.

THPAC13

Simulation and Optimization of Multi-Slit Based Emittance Measurement for BNL ERL

1166

C. Liu, D.M. Gassner, D. Kayran, M.G. Minty, P. Thieberger
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.
A code for determining the beam emittance from a multi-slit image has been developed. To verify its validity, we simulated a beam distribution in 4D phase space at the multi-slit position and the resulting image at a downstream profile measurement device. We applied the algorithm to this image pattern to recover the beam emittance at the slit position. The dependence of the relative difference of the inferred emittance and the input emittance on the slit width and drift length are studied in detail and presented in this report.