Romuald Duperrier - Academia.edu (original) (raw)
Papers by Romuald Duperrier
AIP Conference Proceedings, 2003
ABSTRACT
AIP Conference Proceedings, 2005
In the framework of the HIPPI project a 3D linac code comparison and benchmarking program have be... more In the framework of the HIPPI project a 3D linac code comparison and benchmarking program have been initiated. Particular attention is devoted to the validation of the space charge solvers, comparing the calculated electric field of a common initial distribution with a semi-analytical solution. In order to study the effects of numerical noise on the single particle dynamics, also the calculated single particle tune is compared with an analytical prediction. Particle tracking is eventually compared using the lattice of UNILAC DTL section, in preparation of validation with experimental emittance measurements to be carried out in the next two years.
To reduce the cavity transverse section at low frequencies, people use to increase the inductance... more To reduce the cavity transverse section at low frequencies, people use to increase the inductance using the longitudinal direction (coaxial RFQ). In the four rods cavity, the electrical current goes longitudinally in rods supports. The disadvantage of this technique is the increased power deposition in these supports. The proposed geometry is derived from the four vanes technology. The vanes are identical near the beam but asymmetrically cut near the bottom of the cavity to force the longitudinal electrical current. The benefit is a massive copper structure easy to cool and using technology and knowledge developed for the RFQ of the IPHI project. We give for an example the RF power depositions calculated with SOPRANO and mechanical deformations calculated with IDEAS of the design performed in favour of the SPIRAL II project (LINAG).
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440)
The Rare Isotope Accelerator (RIA) [1] requires a high power linac capable of accelerating all io... more The Rare Isotope Accelerator (RIA) [1] requires a high power linac capable of accelerating all ions up to uranium to energies of 400 MeV/u with a beam power of 100 to 400 kW in a CW regime. One of the most challenging features of the proposed RIA driver linac is the simultaneous acceleration of different charge states in order to increase the final beam power. The acceleration in the last part of the accelerator is provided by elliptical cavities. Three geometrical β are used: 0.47, 0.61 and 0.81. To minimize the cost, one option is to reduce the number of cryostats. This implies a maximal number of cavities per cryostat. Assuming a lattice composed by one doublet and one cryostat, this option leads to an increase of the longitudinal phase advance if each cavity is used at the maximum field. The transverse phase advance, has to be set correctly in order to ensure stable motion. This report aims to evaluate the sensitivity to instabilities induced by the transverse to longitudinal coupling in the elliptical cavities of the RIA linac for an 88 + uranium beam.
Physical Review Special Topics - Accelerators and Beams, 2000
A cw high power linear accelerator can only work with very low particle losses and structure acti... more A cw high power linear accelerator can only work with very low particle losses and structure activation. At low energy, the radio frequency quadrupole (RFQ) is an accelerator element that is very sensitive to losses. To design this structure, a good understanding of the beam dynamics is required. Generally, the reference code PARMTEQM is enough to design the accelerator. TOUTATIS has been written with the goals of cross-checking results and obtaining more reliable dynamics. This paper relates the different numerical methods used in the code. It is time based, using multigrids methods and adaptive mesh for a fine description of the forces without being time consuming. The field is calculated through a Poisson solver and the vanes are fully described, allowing it to properly simulate the coupling gaps and the RFQs extremities. Theoretical and experimental tests are also described and show a good agreement between simulations and reference cases.
IEEE Transactions on Appiled Superconductivity, 2000
During the design of a magnet, people generally pay particular attention to get the largest trans... more During the design of a magnet, people generally pay particular attention to get the largest transverse section with small contribution of undesirable multipoles, and the 2D cross-section is adjusted in that way with a good accuracy. But the poles are often cut with sharp ends in the beam direction. Otherwise, in order to minimize the stray field to avoid interaction with other elements on the beam lines and corner saturation, it is common to define a simple 45° chamber. The such truncated poles will create an amount of multipoles that could exceed the magnet required tolerances. The magnetic length is also affected by the way that the truncation is done. We propose in this paper a handy analytical model that allows both to control integrated focusing forces and magnetic lengths for each type of conventional magnets (dipole, quadrupole, sextupole). The different end pole profiles are simulated with the 3D-program TOSCA for the dipole and the quadrupole cases. To estimate a possible damaging of optical qualities introduced by the end pole profile, we compare the multipole components obtained by a 2D harmonic analysis at the magnet center, with an integrated one along the beam axis, taking into account the entire stray field. The results are then compared with those of the sharp end case
Arxiv preprint physics/ …, 2000
A CW high power linear accelerator can only work with very low particles losses and structure act... more A CW high power linear accelerator can only work with very low particles losses and structure activation. At low energy, the RFQ is a very sensitive element to losses. To design the RFQ, a good understanding of the beam dynamics is requested. Generally, the reference code ...
The ESS project (European Spallation Source) aims to deliver high power beams for matter studies.... more The ESS project (European Spallation Source) aims to deliver high power beams for matter studies. Both H + and Hbeams have to be accelerated and guided to the different spallation targets. Two 50 mA Hbranches are funnelled with one 100 mA H + beam at around 20 MeV. The Hfront end is constituted by a chopper lines between two RFQs and DTLs. The H + front end is composed by one RFQ and one DTL. The two species are transported through the same linac up to 1.334 GeV. This common part is composed by a SDTL and a CCL from 20 to 185 MeV and followed by a SCL (SuperConducting Linac) to reach the final energy. This paper presents the results of beams dynamics studies through the ESS linac including end-to-end simulations and errors studies.
One major system of the IFMIF project (International Fusion Materials Irradiation Facility) is it... more One major system of the IFMIF project (International Fusion Materials Irradiation Facility) is its two accelerators producing the neutron flux by accelerating Deuteron particles up to 40 MeV against a Lithium target. In a first phase called EVEDA (Engineering Validation and Engineering Design Activity), a full scale prototype accelerating particles up to 9 MeV is being studied and constructed in Europe, to be installed in Japan. Two unprecedented performances are required for the IFMIF-EVEDA accelerators: the very high power of 5 MW and very high intensity of 125 mA CW. That leads to numerous unprecedented challenges: harmful losses even for those as low as 10-6 of the beam, non-linear dynamics induced by very strong space charge forces, difficulties for equipment and diagnostic implementations in the high compact structure, need of specific tuning strategies in this context. These issues are highlighted in this article, and the ways they are addressed are detailed.
High-power accelerators are being studied for several projects including accelerator driven neutr... more High-power accelerators are being studied for several projects including accelerator driven neutron or neutrino sources. The low energy part of these facilities has to be carefully optimized to match the beam requirements of the higher energy parts. In this low energy part, the space charge self force, induced by a high intensity beam, has to be carefully controlled. This nonlinear force can generate a large and irreversible emittance growth of the beam. To reduce the space charge (SC), neutralization of the beam charge can be done by capturing some particles of the ionised residual gas in the vacuum chamber. This space charge compensation (SCC) regime complicates the beam dynamics study. This contribution aims to modelize the beam behavior in such regime and to provide criteria to the linac designer to estimate the neutralization rise time and the neutralization degree.
High-power accelerators are being studied for several projects including accelerator driven neutr... more High-power accelerators are being studied for several projects including accelerator driven neutron or neutrino sources. The low energy part of these facilities has to be carefully optimized to match the beam requirements of the higher energy parts. In this low energy part, the space charge self force, induced by a high intensity beam, has to be carefully controlled. This nonlinear force can generate a large and irreversible emittance growth of the beam. To reduce the space charge (SC), neutralization of the beam charge can be done by capturing some particles of the ionised residual gas in the vacuum chamber. This space charge compensation (SCC) regime complicates the beam dynamics study. Modelling the beam behavior in such a regime would be a significant contribution to the development of high intensity accelerators.
ABSTRACT One of the major challenge in the design of the Low En-ergy Beam Transport (LEBT) sectio... more ABSTRACT One of the major challenge in the design of the Low En-ergy Beam Transport (LEBT) section of the high intensity proton, H − and deuteron beam accelerators is to transport the beam from the ion source to the RFQ with minimizing the emittance growth. New PIC ray-tracing methods allows to design and sim-ulate the transport of high intensity beam in the LEBT systems of future accelerators like FAIR Proton Linac or IFMIF-EVEDA linacs. These techniques enable a precise prediction of the effect of residual gas ionisation and the consequent neutralisation of the large beam space charge on the beam emittances. The amount of space charge com-pensation along a high intensity LEBT section is crucial for the achievable beam quality at the exit of the section. An algorithm for adequate modelling of the compensation is presented. It includes the dynamic behaviour of the com-pensation as well as its dependence on the longitudinal and radial position along the beam line. The impact of this de-pendence on the beam quality and the source and LEBT design is presented.
The International Fusion Materials Irradiation Facility (IFMIF) project requests two linacs desig... more The International Fusion Materials Irradiation Facility (IFMIF) project requests two linacs designed to accelerate 125 mA deuteron beams up to 40 MeV. The linac operates in CW mode and uses one RFQ and 10 DTL tanks [1]. After extraction and transport, the two deuteron beams with strong space charge forces have to be bunched, accelerated and transported to the target for the production of high neutron flux. This paper presents the High Energy Beam Transport (HEBT) line which provides a flat rectangular beam profile on the liquid lithium target. Transverse uniform beam density is obtained using non-linear mutipole lenses (octupoles and duodecapoles). Optical design and beam dynamics with and without errors has been studied.
A superconducting proton linac (SPL) is considered since a few years as a very interesting accele... more A superconducting proton linac (SPL) is considered since a few years as a very interesting accelerator for the future of CERN. This device is planned to serve at the same time as a proton driver for EURISOL, for future neutrino experiments (beta beams, super beams, neutrino factory) and as injector for the CERN accelerator complex. Its parameters have recently been revised, taking into account the evolution of the physics requests and the latest developments in superconducting rf. This work will be summarized in a revised conceptual design report (CDR2) to be published by the end of 2005. This paper highlights the most important changes and the foreseen staged approach towards the SPL.
A revision of the physics needs and recent progress in the technology of superconducting (SC) RF ... more A revision of the physics needs and recent progress in the technology of superconducting (SC) RF cavities have triggered major changes in the design of a SC H¯ linac at CERN. With up to 5MW beam power, the SPL can be the proton driver for a next generation ISOL-type radioactive beam facility ("EURISOL") and/or supply protons to a neutrino (ν) facility (conventional superbeam + beta-beam or ν-factory). Furthermore the SPL can replace Linac2 and the PS booster (PSB), improving significantly the beam performance in terms of brightness, intensity, and reliability for the benefit of all proton users at CERN, including LHC and its luminosity upgrade. Compared with the first conceptual design, the beam energy is almost doubled (3.5GeV instead of 2.2 GeV) while the length is reduced by 40%. At a repetition rate of 50 Hz, the linac reuses decommissioned 352.2MHz RF equipment from LEP in the low-energy part. Beyond 90MeV the RF frequency is doubled, and from 180MeV onwards high-gradient SC bulkniobium cavities accelerate the beam to its final energy of 3.5GeV. This paper presents the overall design approach, together with the technical progress since the first conceptual design in 2000.
The two IFMIF (International Fusion Materials Irradiation Facility) accelerators will each have t... more The two IFMIF (International Fusion Materials Irradiation Facility) accelerators will each have to deliver 125mA, 5 MW of deuteron beam at 40 MeV. To validate the conceptual design, a prototype, consisting of one 9 MeV accelerator called EVEDA (Engineering Validation and Engineering Design Activity), is being constructed. Beam dynamics studies are entering the final phase for the whole EVEDA and for the accelerating part of IFMIF. The challenging points are the very high intensity and the very high power to be delivered. At energies up to 5 MeV, difficulties are to reach the requested intensity under a very strong space charge / compensation regime. Over 5 MeV, difficulties are to make sure that beam losses can be maintained well below 10-6 of the beam in order to meet hands-on maintenance requirements. This paper will report the strategies and choices adopted in the optics design and the beam measurement proposal.
The chopping line is a critical part of the ESS linac in term of technical realisation of the cho... more The chopping line is a critical part of the ESS linac in term of technical realisation of the choppers and preservation of the beam qualities. A new optimised design of the ESS RFQs and chopping lines is reported. The beam dynamics has been optimised with H beam currents up to 100-mA to have safety margin with respect to the ESS goals. The first RFQ transmits almost 99.7% of the beam up to 2 MeV. The line with two choppers allows a perfect chopping between 2 bunches. The second RFQ accelerates the particles up to 5 MeV with a transmission close to 100%.
AIP Conference Proceedings, 2003
ABSTRACT
AIP Conference Proceedings, 2005
In the framework of the HIPPI project a 3D linac code comparison and benchmarking program have be... more In the framework of the HIPPI project a 3D linac code comparison and benchmarking program have been initiated. Particular attention is devoted to the validation of the space charge solvers, comparing the calculated electric field of a common initial distribution with a semi-analytical solution. In order to study the effects of numerical noise on the single particle dynamics, also the calculated single particle tune is compared with an analytical prediction. Particle tracking is eventually compared using the lattice of UNILAC DTL section, in preparation of validation with experimental emittance measurements to be carried out in the next two years.
To reduce the cavity transverse section at low frequencies, people use to increase the inductance... more To reduce the cavity transverse section at low frequencies, people use to increase the inductance using the longitudinal direction (coaxial RFQ). In the four rods cavity, the electrical current goes longitudinally in rods supports. The disadvantage of this technique is the increased power deposition in these supports. The proposed geometry is derived from the four vanes technology. The vanes are identical near the beam but asymmetrically cut near the bottom of the cavity to force the longitudinal electrical current. The benefit is a massive copper structure easy to cool and using technology and knowledge developed for the RFQ of the IPHI project. We give for an example the RF power depositions calculated with SOPRANO and mechanical deformations calculated with IDEAS of the design performed in favour of the SPIRAL II project (LINAG).
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440)
The Rare Isotope Accelerator (RIA) [1] requires a high power linac capable of accelerating all io... more The Rare Isotope Accelerator (RIA) [1] requires a high power linac capable of accelerating all ions up to uranium to energies of 400 MeV/u with a beam power of 100 to 400 kW in a CW regime. One of the most challenging features of the proposed RIA driver linac is the simultaneous acceleration of different charge states in order to increase the final beam power. The acceleration in the last part of the accelerator is provided by elliptical cavities. Three geometrical β are used: 0.47, 0.61 and 0.81. To minimize the cost, one option is to reduce the number of cryostats. This implies a maximal number of cavities per cryostat. Assuming a lattice composed by one doublet and one cryostat, this option leads to an increase of the longitudinal phase advance if each cavity is used at the maximum field. The transverse phase advance, has to be set correctly in order to ensure stable motion. This report aims to evaluate the sensitivity to instabilities induced by the transverse to longitudinal coupling in the elliptical cavities of the RIA linac for an 88 + uranium beam.
Physical Review Special Topics - Accelerators and Beams, 2000
A cw high power linear accelerator can only work with very low particle losses and structure acti... more A cw high power linear accelerator can only work with very low particle losses and structure activation. At low energy, the radio frequency quadrupole (RFQ) is an accelerator element that is very sensitive to losses. To design this structure, a good understanding of the beam dynamics is required. Generally, the reference code PARMTEQM is enough to design the accelerator. TOUTATIS has been written with the goals of cross-checking results and obtaining more reliable dynamics. This paper relates the different numerical methods used in the code. It is time based, using multigrids methods and adaptive mesh for a fine description of the forces without being time consuming. The field is calculated through a Poisson solver and the vanes are fully described, allowing it to properly simulate the coupling gaps and the RFQs extremities. Theoretical and experimental tests are also described and show a good agreement between simulations and reference cases.
IEEE Transactions on Appiled Superconductivity, 2000
During the design of a magnet, people generally pay particular attention to get the largest trans... more During the design of a magnet, people generally pay particular attention to get the largest transverse section with small contribution of undesirable multipoles, and the 2D cross-section is adjusted in that way with a good accuracy. But the poles are often cut with sharp ends in the beam direction. Otherwise, in order to minimize the stray field to avoid interaction with other elements on the beam lines and corner saturation, it is common to define a simple 45° chamber. The such truncated poles will create an amount of multipoles that could exceed the magnet required tolerances. The magnetic length is also affected by the way that the truncation is done. We propose in this paper a handy analytical model that allows both to control integrated focusing forces and magnetic lengths for each type of conventional magnets (dipole, quadrupole, sextupole). The different end pole profiles are simulated with the 3D-program TOSCA for the dipole and the quadrupole cases. To estimate a possible damaging of optical qualities introduced by the end pole profile, we compare the multipole components obtained by a 2D harmonic analysis at the magnet center, with an integrated one along the beam axis, taking into account the entire stray field. The results are then compared with those of the sharp end case
Arxiv preprint physics/ …, 2000
A CW high power linear accelerator can only work with very low particles losses and structure act... more A CW high power linear accelerator can only work with very low particles losses and structure activation. At low energy, the RFQ is a very sensitive element to losses. To design the RFQ, a good understanding of the beam dynamics is requested. Generally, the reference code ...
The ESS project (European Spallation Source) aims to deliver high power beams for matter studies.... more The ESS project (European Spallation Source) aims to deliver high power beams for matter studies. Both H + and Hbeams have to be accelerated and guided to the different spallation targets. Two 50 mA Hbranches are funnelled with one 100 mA H + beam at around 20 MeV. The Hfront end is constituted by a chopper lines between two RFQs and DTLs. The H + front end is composed by one RFQ and one DTL. The two species are transported through the same linac up to 1.334 GeV. This common part is composed by a SDTL and a CCL from 20 to 185 MeV and followed by a SCL (SuperConducting Linac) to reach the final energy. This paper presents the results of beams dynamics studies through the ESS linac including end-to-end simulations and errors studies.
One major system of the IFMIF project (International Fusion Materials Irradiation Facility) is it... more One major system of the IFMIF project (International Fusion Materials Irradiation Facility) is its two accelerators producing the neutron flux by accelerating Deuteron particles up to 40 MeV against a Lithium target. In a first phase called EVEDA (Engineering Validation and Engineering Design Activity), a full scale prototype accelerating particles up to 9 MeV is being studied and constructed in Europe, to be installed in Japan. Two unprecedented performances are required for the IFMIF-EVEDA accelerators: the very high power of 5 MW and very high intensity of 125 mA CW. That leads to numerous unprecedented challenges: harmful losses even for those as low as 10-6 of the beam, non-linear dynamics induced by very strong space charge forces, difficulties for equipment and diagnostic implementations in the high compact structure, need of specific tuning strategies in this context. These issues are highlighted in this article, and the ways they are addressed are detailed.
High-power accelerators are being studied for several projects including accelerator driven neutr... more High-power accelerators are being studied for several projects including accelerator driven neutron or neutrino sources. The low energy part of these facilities has to be carefully optimized to match the beam requirements of the higher energy parts. In this low energy part, the space charge self force, induced by a high intensity beam, has to be carefully controlled. This nonlinear force can generate a large and irreversible emittance growth of the beam. To reduce the space charge (SC), neutralization of the beam charge can be done by capturing some particles of the ionised residual gas in the vacuum chamber. This space charge compensation (SCC) regime complicates the beam dynamics study. This contribution aims to modelize the beam behavior in such regime and to provide criteria to the linac designer to estimate the neutralization rise time and the neutralization degree.
High-power accelerators are being studied for several projects including accelerator driven neutr... more High-power accelerators are being studied for several projects including accelerator driven neutron or neutrino sources. The low energy part of these facilities has to be carefully optimized to match the beam requirements of the higher energy parts. In this low energy part, the space charge self force, induced by a high intensity beam, has to be carefully controlled. This nonlinear force can generate a large and irreversible emittance growth of the beam. To reduce the space charge (SC), neutralization of the beam charge can be done by capturing some particles of the ionised residual gas in the vacuum chamber. This space charge compensation (SCC) regime complicates the beam dynamics study. Modelling the beam behavior in such a regime would be a significant contribution to the development of high intensity accelerators.
ABSTRACT One of the major challenge in the design of the Low En-ergy Beam Transport (LEBT) sectio... more ABSTRACT One of the major challenge in the design of the Low En-ergy Beam Transport (LEBT) section of the high intensity proton, H − and deuteron beam accelerators is to transport the beam from the ion source to the RFQ with minimizing the emittance growth. New PIC ray-tracing methods allows to design and sim-ulate the transport of high intensity beam in the LEBT systems of future accelerators like FAIR Proton Linac or IFMIF-EVEDA linacs. These techniques enable a precise prediction of the effect of residual gas ionisation and the consequent neutralisation of the large beam space charge on the beam emittances. The amount of space charge com-pensation along a high intensity LEBT section is crucial for the achievable beam quality at the exit of the section. An algorithm for adequate modelling of the compensation is presented. It includes the dynamic behaviour of the com-pensation as well as its dependence on the longitudinal and radial position along the beam line. The impact of this de-pendence on the beam quality and the source and LEBT design is presented.
The International Fusion Materials Irradiation Facility (IFMIF) project requests two linacs desig... more The International Fusion Materials Irradiation Facility (IFMIF) project requests two linacs designed to accelerate 125 mA deuteron beams up to 40 MeV. The linac operates in CW mode and uses one RFQ and 10 DTL tanks [1]. After extraction and transport, the two deuteron beams with strong space charge forces have to be bunched, accelerated and transported to the target for the production of high neutron flux. This paper presents the High Energy Beam Transport (HEBT) line which provides a flat rectangular beam profile on the liquid lithium target. Transverse uniform beam density is obtained using non-linear mutipole lenses (octupoles and duodecapoles). Optical design and beam dynamics with and without errors has been studied.
A superconducting proton linac (SPL) is considered since a few years as a very interesting accele... more A superconducting proton linac (SPL) is considered since a few years as a very interesting accelerator for the future of CERN. This device is planned to serve at the same time as a proton driver for EURISOL, for future neutrino experiments (beta beams, super beams, neutrino factory) and as injector for the CERN accelerator complex. Its parameters have recently been revised, taking into account the evolution of the physics requests and the latest developments in superconducting rf. This work will be summarized in a revised conceptual design report (CDR2) to be published by the end of 2005. This paper highlights the most important changes and the foreseen staged approach towards the SPL.
A revision of the physics needs and recent progress in the technology of superconducting (SC) RF ... more A revision of the physics needs and recent progress in the technology of superconducting (SC) RF cavities have triggered major changes in the design of a SC H¯ linac at CERN. With up to 5MW beam power, the SPL can be the proton driver for a next generation ISOL-type radioactive beam facility ("EURISOL") and/or supply protons to a neutrino (ν) facility (conventional superbeam + beta-beam or ν-factory). Furthermore the SPL can replace Linac2 and the PS booster (PSB), improving significantly the beam performance in terms of brightness, intensity, and reliability for the benefit of all proton users at CERN, including LHC and its luminosity upgrade. Compared with the first conceptual design, the beam energy is almost doubled (3.5GeV instead of 2.2 GeV) while the length is reduced by 40%. At a repetition rate of 50 Hz, the linac reuses decommissioned 352.2MHz RF equipment from LEP in the low-energy part. Beyond 90MeV the RF frequency is doubled, and from 180MeV onwards high-gradient SC bulkniobium cavities accelerate the beam to its final energy of 3.5GeV. This paper presents the overall design approach, together with the technical progress since the first conceptual design in 2000.
The two IFMIF (International Fusion Materials Irradiation Facility) accelerators will each have t... more The two IFMIF (International Fusion Materials Irradiation Facility) accelerators will each have to deliver 125mA, 5 MW of deuteron beam at 40 MeV. To validate the conceptual design, a prototype, consisting of one 9 MeV accelerator called EVEDA (Engineering Validation and Engineering Design Activity), is being constructed. Beam dynamics studies are entering the final phase for the whole EVEDA and for the accelerating part of IFMIF. The challenging points are the very high intensity and the very high power to be delivered. At energies up to 5 MeV, difficulties are to reach the requested intensity under a very strong space charge / compensation regime. Over 5 MeV, difficulties are to make sure that beam losses can be maintained well below 10-6 of the beam in order to meet hands-on maintenance requirements. This paper will report the strategies and choices adopted in the optics design and the beam measurement proposal.
The chopping line is a critical part of the ESS linac in term of technical realisation of the cho... more The chopping line is a critical part of the ESS linac in term of technical realisation of the choppers and preservation of the beam qualities. A new optimised design of the ESS RFQs and chopping lines is reported. The beam dynamics has been optimised with H beam currents up to 100-mA to have safety margin with respect to the ESS goals. The first RFQ transmits almost 99.7% of the beam up to 2 MeV. The line with two choppers allows a perfect chopping between 2 bunches. The second RFQ accelerates the particles up to 5 MeV with a transmission close to 100%.