T. Roser - Academia.edu (original) (raw)

Papers by T. Roser

Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003

The RHIC spin design goal assumes 2 × 10 11 proton/bunch with 70% polarization. As the injector t... more The RHIC spin design goal assumes 2 × 10 11 proton/bunch with 70% polarization. As the injector to RHIC, polarized protons have been accelerated at the AGS for years to increase the polarization transmission efficiency. Several novel techniques have been applied in the AGS to overcome the intrinsic and imperfection resonances. The present level of accelerator performance is discussed. Progress on understanding the beam polarization behavior is presented. The outlook and future plan are also discussed.

Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003

During the summer of 2002, eight superconducting helical spin rotators were installed into RHIC i... more During the summer of 2002, eight superconducting helical spin rotators were installed into RHIC in order to control the polarization directions independently at the STAR and PHENIX experiments. Without the rotators, the orientation of polarization at the interaction points would only be vertical. With four rotators around each of the two experiments, we can rotate either or both beams from vertical into the horizontal plane through the interaction region and then back to vertical on the other side. This allows independent control for each beam with vertical, longitudinal, or radial polarization at the experiment. In this paper, we present results from the first run using the new spin rotators at PHENIX.

Physics Letters B, 1999

The reaction "C(p.2~ + n) was measured for momentum transfers of 4.8 and 6.2 (GeV/c)' at beam mom... more The reaction "C(p.2~ + n) was measured for momentum transfers of 4.8 and 6.2 (GeV/c)' at beam momenta of 5.9 and 7.5 GeV/c. We measured the quasi-elastic reaction ( p,2 p) at f3,, = 90", in a kinematically complete measurement. The neutron momentum was measured in triple coincidence with the two emerging high momentum protons. We present the correlation between the momenta of the struck target proton and the neutron. The events are associated with the high momentum components of the nuclear wave function. We present sparse data which. combined with a quasi elastic description of the ( p.2 p) reaction and kinematical arguments, point to a novel way for isolating two-nucleon short range correlations. 0

Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366), 1999

The RHIC spin program requires excellent polarimetry so that the knowledge of the beam polarizati... more The RHIC spin program requires excellent polarimetry so that the knowledge of the beam polarization does not limit the errors on the experimental measurements. However, polarimetry of proton beams with energies higher than about 30GeV poses a difficult challenge. For polarization monitoring during operation, a fast and reliable polarimeter is required that produces a polarization measurement with a 10% relative error within a few minutes. The p-Carbon elastic scattering in the Coulomb-Nuclear-Scattering(CNI) region has a calculable and large analyzing power, but detecting the recoil carbon needs sophisticated detector system and a very thin target. Experiment has been planned in the AGS. This paper describes the experimental setup in the AGS. polarimeter for RHIC. It is quite attractive because measurement is compatible with the pion polarimeter and the detectors could be simple and inexpensive.

Proceedings of the IEEE Particle Accelerator Conference, 2007

where s = 1 corresponds to a full snake, which rotates the Dual partial snake scheme has provided... more where s = 1 corresponds to a full snake, which rotates the Dual partial snake scheme has provided polarized proton beams with 1.5 x 10'' intensity and 65% polarization for the Relativistic Heavy Ion Collider (RHIC) spin program. To overcome the residual polarization loss due to horizontal resonances in the Brookhaven Alternating Gradient Synchrotron (AGS), a new string of quadrupoles have been added. The horizontal tune can then be set in the spin tune gap generated by the two partial snakes, such that horizontal resonances can also be avoided. This paper presents the accelerator setup and preliminary results.

Proceedings of the 1997 Particle Accelerator Conference (Cat. No.97CH36167), 1998

In the recent polarized proton runs in the AGS, a 5% partial snake was used successfully to overc... more In the recent polarized proton runs in the AGS, a 5% partial snake was used successfully to overcome the imperfection depolarizing resonances. Polarized proton beam was accelerated up to the required RHIC injection energy of 25 GeV. However, significant amount of polarization was lost at 0+ν y , 12+ν y and 36+ν y , which is believed to be partially due to the coupling resonances. To overcome the coupling resonance, an energy-jump was generated by rapidly changing the beam circumference using the powerful AGS rf system. It clearly demonstrates that the novel energy-jump method can successfully overcome coupling resonances and weak intrinsic resonances. 1460 0-7803-4376-X/98/$10.00

Physical Review Special Topics - Accelerators and Beams, 2005

ABSTRACT

The last nms in both gold-gold and polarized proton-proton required necessary corrections in the ... more The last nms in both gold-gold and polarized proton-proton required necessary corrections in the ramp as the intensities in the two rings were rising towards design values. Corrections were made with respect to the beam-beam effects, transverse and longitudinal instabilities, transition crossing (for the gold-gold ramps), transverse tune resonances, local and global coupliug problems, aperture restrictions, chromatic effects. Along the ramps we had to use the beam separation, ''Landau'' cavities, chromatic and tune control, orbit correction, special gamma-t quadrupole system for the transition crossing in the gold run, correction octupole circuits, beam position monitor system decoupling etc.

Nuclear Physics B - Proceedings Supplements, 1996

Since 1993, a digital transverse damper system has been used at the Brookhaven Alternating Gradie... more Since 1993, a digital transverse damper system has been used at the Brookhaven Alternating Gradient Synchrotron (AGS). The dampers are used to damp coherent oscillations and injection errors in both planes for protons and all species of Heavy Ions. Over nine years, several AGS improvements, the addition of the Relativistic Heavy Ion Collider (RHIC) operations, and our experience, created a critical need to improve the original system. Several enhancements have been made to the digital electronics including compatibility with harmonic numbers up to 24, an increase in the system resolution from eight to ten bits, and the conversion of the system interface to VME. The analog electronics were also modified to appropriately interface with the new digital electronics, as well as to provide an overall functional improvement. The pick-up electrode (PUE) preamplifiers were redesigned to decrease the radiation susceptibility of the electronics. The concepts of the AGS Damper system can be uti...

Polarized protons were injected and accelerated in the clockwise ring of RHIC to commission the f... more Polarized protons were injected and accelerated in the clockwise ring of RHIC to commission the first full helical Siberian snake ever used in an accelerator. With the snake turned on, the stable spin direction is in the horizontal plane. Vertically polarized protons were injected with the snake off. The snake was adiabatically ramped to give a spin rotation of 180 • around a horizontal rotation axis about 13 • from the longitudinal. When the beam was accelerated from injection Gγ = 46.5 to Gγ = 48 the spin flipped sign as expected and polarization was preserved. At Gγ = 48 without the snake, no polarization was observed since several spin resonances were crossed. Eventually polarized beam was accelerated to Gγ = 55.7 (29.1 GeV). In the next proton running period we plan to run with two full helical snakes in each ring and collide both transversely and longitudinally polarized protons at an energy around 100 GeV per beam.

Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003

The RHIC spin design goal assumes 2 × 10 11 proton/bunch with 70% polarization. As the injector t... more The RHIC spin design goal assumes 2 × 10 11 proton/bunch with 70% polarization. As the injector to RHIC, polarized protons have been accelerated at the AGS for years to increase the polarization transmission efficiency. Several novel techniques have been applied in the AGS to overcome the intrinsic and imperfection resonances. The present level of accelerator performance is discussed. Progress on understanding the beam polarization behavior is presented. The outlook and future plan are also discussed.

Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003

During the summer of 2002, eight superconducting helical spin rotators were installed into RHIC i... more During the summer of 2002, eight superconducting helical spin rotators were installed into RHIC in order to control the polarization directions independently at the STAR and PHENIX experiments. Without the rotators, the orientation of polarization at the interaction points would only be vertical. With four rotators around each of the two experiments, we can rotate either or both beams from vertical into the horizontal plane through the interaction region and then back to vertical on the other side. This allows independent control for each beam with vertical, longitudinal, or radial polarization at the experiment. In this paper, we present results from the first run using the new spin rotators at PHENIX.

Physics Letters B, 1999

The reaction "C(p.2~ + n) was measured for momentum transfers of 4.8 and 6.2 (GeV/c)' at beam mom... more The reaction "C(p.2~ + n) was measured for momentum transfers of 4.8 and 6.2 (GeV/c)' at beam momenta of 5.9 and 7.5 GeV/c. We measured the quasi-elastic reaction ( p,2 p) at f3,, = 90", in a kinematically complete measurement. The neutron momentum was measured in triple coincidence with the two emerging high momentum protons. We present the correlation between the momenta of the struck target proton and the neutron. The events are associated with the high momentum components of the nuclear wave function. We present sparse data which. combined with a quasi elastic description of the ( p.2 p) reaction and kinematical arguments, point to a novel way for isolating two-nucleon short range correlations. 0

Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366), 1999

The RHIC spin program requires excellent polarimetry so that the knowledge of the beam polarizati... more The RHIC spin program requires excellent polarimetry so that the knowledge of the beam polarization does not limit the errors on the experimental measurements. However, polarimetry of proton beams with energies higher than about 30GeV poses a difficult challenge. For polarization monitoring during operation, a fast and reliable polarimeter is required that produces a polarization measurement with a 10% relative error within a few minutes. The p-Carbon elastic scattering in the Coulomb-Nuclear-Scattering(CNI) region has a calculable and large analyzing power, but detecting the recoil carbon needs sophisticated detector system and a very thin target. Experiment has been planned in the AGS. This paper describes the experimental setup in the AGS. polarimeter for RHIC. It is quite attractive because measurement is compatible with the pion polarimeter and the detectors could be simple and inexpensive.

Proceedings of the IEEE Particle Accelerator Conference, 2007

where s = 1 corresponds to a full snake, which rotates the Dual partial snake scheme has provided... more where s = 1 corresponds to a full snake, which rotates the Dual partial snake scheme has provided polarized proton beams with 1.5 x 10'' intensity and 65% polarization for the Relativistic Heavy Ion Collider (RHIC) spin program. To overcome the residual polarization loss due to horizontal resonances in the Brookhaven Alternating Gradient Synchrotron (AGS), a new string of quadrupoles have been added. The horizontal tune can then be set in the spin tune gap generated by the two partial snakes, such that horizontal resonances can also be avoided. This paper presents the accelerator setup and preliminary results.

Proceedings of the 1997 Particle Accelerator Conference (Cat. No.97CH36167), 1998

In the recent polarized proton runs in the AGS, a 5% partial snake was used successfully to overc... more In the recent polarized proton runs in the AGS, a 5% partial snake was used successfully to overcome the imperfection depolarizing resonances. Polarized proton beam was accelerated up to the required RHIC injection energy of 25 GeV. However, significant amount of polarization was lost at 0+ν y , 12+ν y and 36+ν y , which is believed to be partially due to the coupling resonances. To overcome the coupling resonance, an energy-jump was generated by rapidly changing the beam circumference using the powerful AGS rf system. It clearly demonstrates that the novel energy-jump method can successfully overcome coupling resonances and weak intrinsic resonances. 1460 0-7803-4376-X/98/$10.00

Physical Review Special Topics - Accelerators and Beams, 2005

ABSTRACT

The last nms in both gold-gold and polarized proton-proton required necessary corrections in the ... more The last nms in both gold-gold and polarized proton-proton required necessary corrections in the ramp as the intensities in the two rings were rising towards design values. Corrections were made with respect to the beam-beam effects, transverse and longitudinal instabilities, transition crossing (for the gold-gold ramps), transverse tune resonances, local and global coupliug problems, aperture restrictions, chromatic effects. Along the ramps we had to use the beam separation, ''Landau'' cavities, chromatic and tune control, orbit correction, special gamma-t quadrupole system for the transition crossing in the gold run, correction octupole circuits, beam position monitor system decoupling etc.

Nuclear Physics B - Proceedings Supplements, 1996

Since 1993, a digital transverse damper system has been used at the Brookhaven Alternating Gradie... more Since 1993, a digital transverse damper system has been used at the Brookhaven Alternating Gradient Synchrotron (AGS). The dampers are used to damp coherent oscillations and injection errors in both planes for protons and all species of Heavy Ions. Over nine years, several AGS improvements, the addition of the Relativistic Heavy Ion Collider (RHIC) operations, and our experience, created a critical need to improve the original system. Several enhancements have been made to the digital electronics including compatibility with harmonic numbers up to 24, an increase in the system resolution from eight to ten bits, and the conversion of the system interface to VME. The analog electronics were also modified to appropriately interface with the new digital electronics, as well as to provide an overall functional improvement. The pick-up electrode (PUE) preamplifiers were redesigned to decrease the radiation susceptibility of the electronics. The concepts of the AGS Damper system can be uti...

Polarized protons were injected and accelerated in the clockwise ring of RHIC to commission the f... more Polarized protons were injected and accelerated in the clockwise ring of RHIC to commission the first full helical Siberian snake ever used in an accelerator. With the snake turned on, the stable spin direction is in the horizontal plane. Vertically polarized protons were injected with the snake off. The snake was adiabatically ramped to give a spin rotation of 180 • around a horizontal rotation axis about 13 • from the longitudinal. When the beam was accelerated from injection Gγ = 46.5 to Gγ = 48 the spin flipped sign as expected and polarization was preserved. At Gγ = 48 without the snake, no polarization was observed since several spin resonances were crossed. Eventually polarized beam was accelerated to Gγ = 55.7 (29.1 GeV). In the next proton running period we plan to run with two full helical snakes in each ring and collide both transversely and longitudinally polarized protons at an energy around 100 GeV per beam.