U. Iriso - Academia.edu (original) (raw)
Papers by U. Iriso
Physical Review Accelerators and Beams
Physical Review Accelerators and Beams
AIP Conference Proceedings, 2005
ABSTRACT
Physical Review Accelerators and Beams, 2016
The N beam position monitor method (N-BPM) which was recently developed for the LHC has significa... more The N beam position monitor method (N-BPM) which was recently developed for the LHC has significantly improved the precision of optics measurements that are based on BPM turn-by-turn data. The main improvement is due to the consideration of correlations for statistical and systematic error sources, as well as increasing the amount of BPM combinations which are used to derive the β-function at one location. We present how this technique can be applied at light sources like ALBA, and compare the results with other methods.
The luminosity in RHIC is limited by vacuum pressure rises, observed with high intensity beams of... more The luminosity in RHIC is limited by vacuum pressure rises, observed with high intensity beams of all species (Au{sup 79+}, d{sup +}, p{sup +}). At injection, the pressure rise could be linked to the existence of electron clouds. In addition, pressure rises in the experimental regions may be caused by electron clouds. They review the existing observations, comparisons with simulations,
Spin 2004, 2005
The Relativistic Heavy Ion Collider (RHIC) has collided protons with both transverse and longitud... more The Relativistic Heavy Ion Collider (RHIC) has collided protons with both transverse and longitudinal polarization at a centre-of-mass energy of 200 GeV. Future running will extend this to 500 GeV. This paper describes the methods used to accelerate and manipulate polarized proton beams in RHIC and its injectors. Special techniques include the use of a partial Siberian snake and an
After reviewing the basic features of electron clouds in particle accelerators, the pertinent vac... more After reviewing the basic features of electron clouds in particle accelerators, the pertinent vacuum-chamber surface properties, and the electron-cloud simulation tools in use at CERN, we report recent observations of electron-cloud phenomena at the Large Hadron Collider (LHC) and ongoing attempts to benchmark the measured LHC vacuum pressure increases and heat loads against electron-cloud build-up simulations aimed at determining the
Electron cloud is one of the leading mechanisms that limit the performance of high intensity circ... more Electron cloud is one of the leading mechanisms that limit the performance of high intensity circular accelerators and colliders. In the Relativistic Heavy Ion Collider, multibunch electron cloud effects are observed both in the warm region and super-conducting region when the number of ion bunches and their intensities are raised beyond the design values. Vacuum-pressure rises, transverse tune shifts, and electron detector signals are observed at injection, upon transition crossing, and at top energy. Transverse emittance growth, fast instabilities, and beam loss also occur upon transition crossing. With the Spallation Neutron Source Ring, single-bunch electron cloud effects are expected for the high intensity proton beam. A comprehensive list of mitigation measures are implemented both to reduce the production of electron cloud and to control the beam stability. This paper intends to provide an overview of observations, performance limitations, and beam dynamics challenges pertaining to electron cloud build-up in high intensity, circular hadron accelerators.
The design of stripline kickers shall be adapted to match the line impedance, maximize the effect... more The design of stripline kickers shall be adapted to match the line impedance, maximize the effective beam kick, reduce the heat load and minimize the transverse coupling impedance. These kickers are used for either tune measurements or transverse feedback. We describe the ALBA design of these kickers for the Storage Ring.
Low energy electrons generated by the interaction of high energy particles with the beam pipe sur... more Low energy electrons generated by the interaction of high energy particles with the beam pipe surface can be detrimental for accelerators performances increasing the vacuum pressure, the heat load and eventually producing beam instabilities. The low energy electrons accumulating in the beam pipe are often referred to as electron cloud. In this presentation we report on the direct evidence of the electron cloud in the electron storage ring of the synchrotron light source ANKA (ANgstrom source KArlsruhe).
This paper describes the pressure evolution produced by an electron-impact desorption in the Rela... more This paper describes the pressure evolution produced by an electron-impact desorption in the Relativistic Heavy Ion Collider (RHIC) beam pipes. The pressure crucially de- pends on the electron induced molecular desorption coef- cient of the beam pipe material, which provides the num- ber of molecules released when an electron hits its sur- face. This coefcient is inferred from electron detector and pressure gauge signals. The evolution of the electron- impact desorption coefcient after weeks of electron bom- bardment is shown.
In the framework of the CERN program on the electron cloud effects in existing and future acceler... more In the framework of the CERN program on the electron cloud effects in existing and future accelerators, a coaxial multipacting test stand was built. It consists of a 100 mm diameter vacuum chamber forming the outer conductor and 6 wires cage-aerial-type as the inner conductor. In order to simulate the bunched beam, this test stand is submitted to short RF pulses. The available field strength in a travelling wave mode allows to trigger electron multipacting in as received or baked stainless steel surfaces, but not in chambers treated to reduce the secondary emission yield. Thus a number of upgrades in the bench set-up have been pursued, mainly in two directions. The first one is a general improvement on mismatches and losses. Second, instead of dumping the pulsed power into a load, it is re-circulated in a multiple frequency ring resonator. For this purpose, we designed a directional coupler with several kV DC isolation, very low transmission losses and a four octave bandwidth. In th...
Synchrotron Radiation Monitors (SRM) are one of the most useful, non destructive tools, to easily... more Synchrotron Radiation Monitors (SRM) are one of the most useful, non destructive tools, to easily obtain inform a- tion of three important parameters for a synchrotron user: beam position, beam dimensions and beam stability. These monitors diagnose beam performance using the radiation produced when the beam traverses a bending magnet. An extensive usage of SRM, based on the visible part
Physical Review Accelerators and Beams
Physical Review Accelerators and Beams
AIP Conference Proceedings, 2005
ABSTRACT
Physical Review Accelerators and Beams, 2016
The N beam position monitor method (N-BPM) which was recently developed for the LHC has significa... more The N beam position monitor method (N-BPM) which was recently developed for the LHC has significantly improved the precision of optics measurements that are based on BPM turn-by-turn data. The main improvement is due to the consideration of correlations for statistical and systematic error sources, as well as increasing the amount of BPM combinations which are used to derive the β-function at one location. We present how this technique can be applied at light sources like ALBA, and compare the results with other methods.
The luminosity in RHIC is limited by vacuum pressure rises, observed with high intensity beams of... more The luminosity in RHIC is limited by vacuum pressure rises, observed with high intensity beams of all species (Au{sup 79+}, d{sup +}, p{sup +}). At injection, the pressure rise could be linked to the existence of electron clouds. In addition, pressure rises in the experimental regions may be caused by electron clouds. They review the existing observations, comparisons with simulations,
Spin 2004, 2005
The Relativistic Heavy Ion Collider (RHIC) has collided protons with both transverse and longitud... more The Relativistic Heavy Ion Collider (RHIC) has collided protons with both transverse and longitudinal polarization at a centre-of-mass energy of 200 GeV. Future running will extend this to 500 GeV. This paper describes the methods used to accelerate and manipulate polarized proton beams in RHIC and its injectors. Special techniques include the use of a partial Siberian snake and an
After reviewing the basic features of electron clouds in particle accelerators, the pertinent vac... more After reviewing the basic features of electron clouds in particle accelerators, the pertinent vacuum-chamber surface properties, and the electron-cloud simulation tools in use at CERN, we report recent observations of electron-cloud phenomena at the Large Hadron Collider (LHC) and ongoing attempts to benchmark the measured LHC vacuum pressure increases and heat loads against electron-cloud build-up simulations aimed at determining the
Electron cloud is one of the leading mechanisms that limit the performance of high intensity circ... more Electron cloud is one of the leading mechanisms that limit the performance of high intensity circular accelerators and colliders. In the Relativistic Heavy Ion Collider, multibunch electron cloud effects are observed both in the warm region and super-conducting region when the number of ion bunches and their intensities are raised beyond the design values. Vacuum-pressure rises, transverse tune shifts, and electron detector signals are observed at injection, upon transition crossing, and at top energy. Transverse emittance growth, fast instabilities, and beam loss also occur upon transition crossing. With the Spallation Neutron Source Ring, single-bunch electron cloud effects are expected for the high intensity proton beam. A comprehensive list of mitigation measures are implemented both to reduce the production of electron cloud and to control the beam stability. This paper intends to provide an overview of observations, performance limitations, and beam dynamics challenges pertaining to electron cloud build-up in high intensity, circular hadron accelerators.
The design of stripline kickers shall be adapted to match the line impedance, maximize the effect... more The design of stripline kickers shall be adapted to match the line impedance, maximize the effective beam kick, reduce the heat load and minimize the transverse coupling impedance. These kickers are used for either tune measurements or transverse feedback. We describe the ALBA design of these kickers for the Storage Ring.
Low energy electrons generated by the interaction of high energy particles with the beam pipe sur... more Low energy electrons generated by the interaction of high energy particles with the beam pipe surface can be detrimental for accelerators performances increasing the vacuum pressure, the heat load and eventually producing beam instabilities. The low energy electrons accumulating in the beam pipe are often referred to as electron cloud. In this presentation we report on the direct evidence of the electron cloud in the electron storage ring of the synchrotron light source ANKA (ANgstrom source KArlsruhe).
This paper describes the pressure evolution produced by an electron-impact desorption in the Rela... more This paper describes the pressure evolution produced by an electron-impact desorption in the Relativistic Heavy Ion Collider (RHIC) beam pipes. The pressure crucially de- pends on the electron induced molecular desorption coef- cient of the beam pipe material, which provides the num- ber of molecules released when an electron hits its sur- face. This coefcient is inferred from electron detector and pressure gauge signals. The evolution of the electron- impact desorption coefcient after weeks of electron bom- bardment is shown.
In the framework of the CERN program on the electron cloud effects in existing and future acceler... more In the framework of the CERN program on the electron cloud effects in existing and future accelerators, a coaxial multipacting test stand was built. It consists of a 100 mm diameter vacuum chamber forming the outer conductor and 6 wires cage-aerial-type as the inner conductor. In order to simulate the bunched beam, this test stand is submitted to short RF pulses. The available field strength in a travelling wave mode allows to trigger electron multipacting in as received or baked stainless steel surfaces, but not in chambers treated to reduce the secondary emission yield. Thus a number of upgrades in the bench set-up have been pursued, mainly in two directions. The first one is a general improvement on mismatches and losses. Second, instead of dumping the pulsed power into a load, it is re-circulated in a multiple frequency ring resonator. For this purpose, we designed a directional coupler with several kV DC isolation, very low transmission losses and a four octave bandwidth. In th...
Synchrotron Radiation Monitors (SRM) are one of the most useful, non destructive tools, to easily... more Synchrotron Radiation Monitors (SRM) are one of the most useful, non destructive tools, to easily obtain inform a- tion of three important parameters for a synchrotron user: beam position, beam dimensions and beam stability. These monitors diagnose beam performance using the radiation produced when the beam traverses a bending magnet. An extensive usage of SRM, based on the visible part