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C. Pagani

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Papers by C. Pagani

The TESLA Cryogenic Accelerator Modules

The Tera-eV Energy Superconducting Linear Accelerator (TESLA), a 33 km long superconducting linea... more The Tera-eV Energy Superconducting Linear Accelerator (TESLA), a 33 km long superconducting linear electron/positron collider of 500 GeV (upgradeable to 800 GeV) centre of mass energy, presently in the planning phase at DESY, will consist of about 21000 superconducting RF 9-cell cavities of pure Niobium. Each cavity of about 1 m length has to be cooled in a 2.0 K helium bath and operated at 1.3 GHz with 5 Hz beam repetition rate. The cavities, equipped with their individual helium vessels made from titanium, RF input couplers , tuners and magnetic shielding, will be assembled in groups of 12 in about 16 m long cryostats (cryomodules) with thermal radiation shielding at 5-8 K and 40-80 K. Part of the cryomodules will also be equipped with superconducting quadrupoles and steering coils. About 10% of the cryomodules will contain cryogenic valves and instrumentation required for cooling purposes. The paper presents design, construction and assembly details of the cryomodules, which are ...

High pressure rinsing system comparison

2007 IEEE Particle Accelerator Conference (PAC), 2007

High pressure rinsing (HPR) is a key process for the surface preparation of high field supercondu... more High pressure rinsing (HPR) is a key process for the surface preparation of high field superconducting cavities. A portable apparatus for the water jet characterization, based on the transferred momentum between the water jet and a load cell, has been used in different laboratories. This apparatus allows collecting quantitative parameters that characterize the HPR water jet. In this paper, we present a quantitative comparison of the different water jets produced by various nozzles routinely used in different laboratories for the HPR process.

“The Computer Control for the RF System of the Milan K800 Cyclotron

Results of two LANL β = 0.1759, 350-MHz, 2-gap spoke cavities

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

Two β = 0.175, 350 MHz, 2-gap superconducting (SC) spoke cavities were fabricated in industry und... more Two β = 0.175, 350 MHz, 2-gap superconducting (SC) spoke cavities were fabricated in industry under the Advanced Accelerator Applications (AAA) project for the transmutation of nuclear waste. These cavities are promising candidates for the accelerating structures between a RFQ and the elliptical SC cavities for proton and heavy ion linacs. Since their delivery in July 2002, they have been tested in terms of mechanical properties, low-temperature performance, i.e., Q 0-E acc curves at 4 K and 2 K, surface resistance dependence on temperature and for multipacting (MP). The two cavities achieved accelerating fields of 13.5 MV/m and 13.0 MV/m as compared to the required field of 7.5 MV/m with enough margin for the quality factor. These cavities seem to need more time to condition away MP than elliptical cavities, but MP does not occur once the cavity is conditioned and kept at 4 K. The length of the 103 mm-diameter nominal coupler port was found to be too short for the penetrating field.

Conceptual design of a high-brightness linac for soft X-ray SASE-FEL source

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2003

FELs based on SASE are believed to be powerful tools to explore the frontiers of basic sciences, ... more FELs based on SASE are believed to be powerful tools to explore the frontiers of basic sciences, from physics to chemistry to biology. Intense R&D programs have started in the USA and Europe in order to understand the SASE physics and to prove the feasibility of theese sources. The allocation of considerable resources in the Italian National Research Plan (PNR) brought about the formation of a CNR-ENEA-INFN-University of Roma "Tor Vergata" study group. A conceptual design study has been developped and possible schemes for linac sources have been investigated, bringing to the SPARX proposal. We report in this paper the results of a preliminary start to end simulation concerning one option we are considering based on an S-band normal conducting linac with high brightness photoinjector integrated in a RF compressor.

Superconducting RF Activities at Infn Milano-Lasa

RFSC Workshop, 1999

The ARES group at LASA (Laboratorio Acceleratori e Superconduttività Applicata, i.e. Laboratory f... more The ARES group at LASA (Laboratorio Acceleratori e Superconduttività Applicata, i.e. Laboratory for Accelerators and Applied Superconductivity), INFN Milano, is primarily engaged in the TESLA Test Facility International Collaboration. Our main responsibility in the collaboration are the design of the TTF 12 m long cryostats, manufactured by the Italian company Zanon under our supervision and the development and construction of the high brightness photocathode preparation system. The prototype TTF cryomodule has been successfully operated in DESY in 1997, and two second generation cryostats have been manufactured and sent to DESY, to be assembled and tested in 1998. The second generation cryostat has a much simpler and cheaper design than the prototype structure, and allowed a cost reduction of a factor of 2.5. A third generation design is in its final stage, in order to progress towards the stringent requirements and lower costs of the TESLA 500 cryomodules, including semi-rigid couplers and "Sekutowicz superstructures" compatibility. Six nine cell superconducting cavities, according to the Collaboration specifications, are being provided to DESY through Italian companies (Ansaldo and Zanon). Recently, a new R&D activity on RF superconducting cavities for a high current proton linac for nuclear waste transmutation and energy production has been funded in a two year program. Cryostat activities for the TESLA TTF Collaboration (and towards TESLA 500) Our main involvement in the superconducting RF activities of the TESLA TTF collaboration is the design, construction (with the Italian company Zanon) and installation of the eight cryostats of the TESLA Test Facility Linac. The TTF cryomodule is a unit containing eight 1.3 GHz nine-cell superconducting cavities and a superconducting quadrupole package. The whole structure is approximately 12 meters long, providing support, alignment, cooling and thermal insulation to the string of superconducting cavities.

Model Study of the RF Cavity for the Milan Superconducting Cyclotron

IEEE Transactions on Nuclear Science, 1979

Cavity design tools and applications to the TRASCO project

9th Workshop on RF …, 1999

In order to define the geometry of the beta scaled superconducting cavities for the TRASCO Projec... more In order to define the geometry of the beta scaled superconducting cavities for the TRASCO Project an automated tool has been realized. By means of a useful parameterization of the cavity shape all the goal parameters, qualifying the design performances, can be obtained by an automatic iteration on the electromagnetic codes and design tools. The resulting cavity shapes and design parameters can be stored in a database for analysis and cross-checks. The results of this optimization procedure is presented for the case of the common cavity design for the TRASCO (Italy) and ASH (France) waste transmutation linac Projects. The tool has been interfaced with a finite element structural mechanics code in order to study the stiffening systems needed to increase mechanical stability and to decrease the Lorentz forces detuning in case of pulsed operation.

Upgrade of the TRASCO SC Linac Design@ 700 MHz

We present an upgrade of the design of the high energy superconducting part of the TRASCO Linac. ... more We present an upgrade of the design of the high energy superconducting part of the TRASCO Linac. The RF frequency of the three section linac has been set to 704.4 MHz, in order to reduce the linac length and to benefit from the outstanding results of bulk niobium SC cavities driven by the TESLA Collaboration. The revised design takes into account the demanding linac reliability requirements, crucial for its application as a driver for a nuclear waste transmutation system. This design, that integrates the option of pulsed operation, is a step towards a common design with the French ASH project. A coordinated R&D program for the development of the major critical components has already started and the INFN part of this activity is also outlined in the following paragraphs.

Vacuum Interface Analysis of a Windowless Spallation Target for Accelerator-Driven Systems

Nuclear Science and Engineering, 2007

In recent years the research on nuclear power generation focused on an innovative subcritical rea... more In recent years the research on nuclear power generation focused on an innovative subcritical reactor concept, along with previous liquid-metal-cooled critical reactors. The accelerator-driven system reactor design matches higher and intrinsic safety requirements with the reduction of actinides and long-lived fission products, encumbrances on the nuclear waste final repository. The coupling of the accelerator technology with the reactor facility faces new challenges; the first is the design of the interface between accelerator and reactor. Currently two solutions are proposed and investigated: one with a solid beam-target window interface and the other one without a beam window. Our speculations focus on the windowless approach: No physical barrier is located in the interface region, so the ultrahigh vacuum environment of the accelerator is connected with the operative conditions of the reactor through an intermediate spallation target. In this work we describe our experimental activities and the numerical tool employed to give a basic characterization of the vacuum dynamics for a windowless interface, with particular regard given to proton beamline and target interface of the Ansaldo A80-XADS reference design.

Design considerations of 10 kW -scale extreme ultraviolet SASE FEL for lithography

Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2001

The semiconductor industry growth is driven to a large extent by steady advancements in microlith... more The semiconductor industry growth is driven to a large extent by steady advancements in microlithography. According to the newly updated industry roadmap, the 70nm generation is anticipated to be available in the year 2008. However, the path to get there is not obvious. The problem of construction of Extreme Ultraviolet (EUV) quantum laser for lithography is still unsolved: progress in

Neutralization of the emittance blowup induced by rf time dependent forces in rf guns

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Overview of ILC

AIP Conference Proceedings, 2007

RF gun emittance correction using unsymmetrical RF cavities

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1992

Characterization of an Elliptical Low Beta Multicell Structure for Pulsed Operation

Design Criteria for Elliptical Cavities

In the framework of the TRASCO project, we have developed a set of criteria to guide the design o... more In the framework of the TRASCO project, we have developed a set of criteria to guide the design of elliptical multicell SC cavities, supporting them with a few design tools to aid the geometry optimisation. In this paper we briefly summarize this work and the related codes we have implemented. Some examples are also given of their applications to cavity

Itaca: A New Computer Code for the Integration of Transient Particle and Field Equations in Axisymmetrical Cavities

Recent Developments at PITZ

Proceedings of the 2005 Particle Accelerator Conference, 2005

FORMATION OF THE Cs 2 Te PHOTOCATHODE: AUGER AND PHOTOEMISSION SPECTROSCOPY STUDY

The formation of the Cs 2 Te photocathode on a mo- lybdenum substrate passes through different ph... more The formation of the Cs 2 Te photocathode on a mo- lybdenum substrate passes through different phases, each of them has been characterised by X-ray photoemission spectroscopy and Auger spectroscopy as well. During the fabrication process different cesium tellurides have been identified in the photoemissive material. The ruggedness to pollution with molecular oxygen at different fabrica- tion stages has been tested. Approximately 5·10 -5 sec·torr of exposition reduces the quantum efficiency to one tenth of its original value. The oxidation damage can be par- tially recovered by simultaneously heating the substrate to ≈ 230 °C and illuminating it with the 4.9 eV ultraviolet radiation. No recovering has been observed under the ef- fect of the temperature or the radiation alone.

High QE photocathodes performance during operation at FLASH / PITZ photoinjectors

2007 IEEE Particle Accelerator Conference (PAC), 2007

The TESLA Cryogenic Accelerator Modules

The Tera-eV Energy Superconducting Linear Accelerator (TESLA), a 33 km long superconducting linea... more The Tera-eV Energy Superconducting Linear Accelerator (TESLA), a 33 km long superconducting linear electron/positron collider of 500 GeV (upgradeable to 800 GeV) centre of mass energy, presently in the planning phase at DESY, will consist of about 21000 superconducting RF 9-cell cavities of pure Niobium. Each cavity of about 1 m length has to be cooled in a 2.0 K helium bath and operated at 1.3 GHz with 5 Hz beam repetition rate. The cavities, equipped with their individual helium vessels made from titanium, RF input couplers , tuners and magnetic shielding, will be assembled in groups of 12 in about 16 m long cryostats (cryomodules) with thermal radiation shielding at 5-8 K and 40-80 K. Part of the cryomodules will also be equipped with superconducting quadrupoles and steering coils. About 10% of the cryomodules will contain cryogenic valves and instrumentation required for cooling purposes. The paper presents design, construction and assembly details of the cryomodules, which are ...

High pressure rinsing system comparison

2007 IEEE Particle Accelerator Conference (PAC), 2007

High pressure rinsing (HPR) is a key process for the surface preparation of high field supercondu... more High pressure rinsing (HPR) is a key process for the surface preparation of high field superconducting cavities. A portable apparatus for the water jet characterization, based on the transferred momentum between the water jet and a load cell, has been used in different laboratories. This apparatus allows collecting quantitative parameters that characterize the HPR water jet. In this paper, we present a quantitative comparison of the different water jets produced by various nozzles routinely used in different laboratories for the HPR process.

“The Computer Control for the RF System of the Milan K800 Cyclotron

Results of two LANL β = 0.1759, 350-MHz, 2-gap spoke cavities

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

Two β = 0.175, 350 MHz, 2-gap superconducting (SC) spoke cavities were fabricated in industry und... more Two β = 0.175, 350 MHz, 2-gap superconducting (SC) spoke cavities were fabricated in industry under the Advanced Accelerator Applications (AAA) project for the transmutation of nuclear waste. These cavities are promising candidates for the accelerating structures between a RFQ and the elliptical SC cavities for proton and heavy ion linacs. Since their delivery in July 2002, they have been tested in terms of mechanical properties, low-temperature performance, i.e., Q 0-E acc curves at 4 K and 2 K, surface resistance dependence on temperature and for multipacting (MP). The two cavities achieved accelerating fields of 13.5 MV/m and 13.0 MV/m as compared to the required field of 7.5 MV/m with enough margin for the quality factor. These cavities seem to need more time to condition away MP than elliptical cavities, but MP does not occur once the cavity is conditioned and kept at 4 K. The length of the 103 mm-diameter nominal coupler port was found to be too short for the penetrating field.

Conceptual design of a high-brightness linac for soft X-ray SASE-FEL source

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2003

FELs based on SASE are believed to be powerful tools to explore the frontiers of basic sciences, ... more FELs based on SASE are believed to be powerful tools to explore the frontiers of basic sciences, from physics to chemistry to biology. Intense R&D programs have started in the USA and Europe in order to understand the SASE physics and to prove the feasibility of theese sources. The allocation of considerable resources in the Italian National Research Plan (PNR) brought about the formation of a CNR-ENEA-INFN-University of Roma "Tor Vergata" study group. A conceptual design study has been developped and possible schemes for linac sources have been investigated, bringing to the SPARX proposal. We report in this paper the results of a preliminary start to end simulation concerning one option we are considering based on an S-band normal conducting linac with high brightness photoinjector integrated in a RF compressor.

Superconducting RF Activities at Infn Milano-Lasa

RFSC Workshop, 1999

The ARES group at LASA (Laboratorio Acceleratori e Superconduttività Applicata, i.e. Laboratory f... more The ARES group at LASA (Laboratorio Acceleratori e Superconduttività Applicata, i.e. Laboratory for Accelerators and Applied Superconductivity), INFN Milano, is primarily engaged in the TESLA Test Facility International Collaboration. Our main responsibility in the collaboration are the design of the TTF 12 m long cryostats, manufactured by the Italian company Zanon under our supervision and the development and construction of the high brightness photocathode preparation system. The prototype TTF cryomodule has been successfully operated in DESY in 1997, and two second generation cryostats have been manufactured and sent to DESY, to be assembled and tested in 1998. The second generation cryostat has a much simpler and cheaper design than the prototype structure, and allowed a cost reduction of a factor of 2.5. A third generation design is in its final stage, in order to progress towards the stringent requirements and lower costs of the TESLA 500 cryomodules, including semi-rigid couplers and "Sekutowicz superstructures" compatibility. Six nine cell superconducting cavities, according to the Collaboration specifications, are being provided to DESY through Italian companies (Ansaldo and Zanon). Recently, a new R&D activity on RF superconducting cavities for a high current proton linac for nuclear waste transmutation and energy production has been funded in a two year program. Cryostat activities for the TESLA TTF Collaboration (and towards TESLA 500) Our main involvement in the superconducting RF activities of the TESLA TTF collaboration is the design, construction (with the Italian company Zanon) and installation of the eight cryostats of the TESLA Test Facility Linac. The TTF cryomodule is a unit containing eight 1.3 GHz nine-cell superconducting cavities and a superconducting quadrupole package. The whole structure is approximately 12 meters long, providing support, alignment, cooling and thermal insulation to the string of superconducting cavities.

Model Study of the RF Cavity for the Milan Superconducting Cyclotron

IEEE Transactions on Nuclear Science, 1979

Cavity design tools and applications to the TRASCO project

9th Workshop on RF …, 1999

In order to define the geometry of the beta scaled superconducting cavities for the TRASCO Projec... more In order to define the geometry of the beta scaled superconducting cavities for the TRASCO Project an automated tool has been realized. By means of a useful parameterization of the cavity shape all the goal parameters, qualifying the design performances, can be obtained by an automatic iteration on the electromagnetic codes and design tools. The resulting cavity shapes and design parameters can be stored in a database for analysis and cross-checks. The results of this optimization procedure is presented for the case of the common cavity design for the TRASCO (Italy) and ASH (France) waste transmutation linac Projects. The tool has been interfaced with a finite element structural mechanics code in order to study the stiffening systems needed to increase mechanical stability and to decrease the Lorentz forces detuning in case of pulsed operation.

Upgrade of the TRASCO SC Linac Design@ 700 MHz

We present an upgrade of the design of the high energy superconducting part of the TRASCO Linac. ... more We present an upgrade of the design of the high energy superconducting part of the TRASCO Linac. The RF frequency of the three section linac has been set to 704.4 MHz, in order to reduce the linac length and to benefit from the outstanding results of bulk niobium SC cavities driven by the TESLA Collaboration. The revised design takes into account the demanding linac reliability requirements, crucial for its application as a driver for a nuclear waste transmutation system. This design, that integrates the option of pulsed operation, is a step towards a common design with the French ASH project. A coordinated R&D program for the development of the major critical components has already started and the INFN part of this activity is also outlined in the following paragraphs.

Vacuum Interface Analysis of a Windowless Spallation Target for Accelerator-Driven Systems

Nuclear Science and Engineering, 2007

In recent years the research on nuclear power generation focused on an innovative subcritical rea... more In recent years the research on nuclear power generation focused on an innovative subcritical reactor concept, along with previous liquid-metal-cooled critical reactors. The accelerator-driven system reactor design matches higher and intrinsic safety requirements with the reduction of actinides and long-lived fission products, encumbrances on the nuclear waste final repository. The coupling of the accelerator technology with the reactor facility faces new challenges; the first is the design of the interface between accelerator and reactor. Currently two solutions are proposed and investigated: one with a solid beam-target window interface and the other one without a beam window. Our speculations focus on the windowless approach: No physical barrier is located in the interface region, so the ultrahigh vacuum environment of the accelerator is connected with the operative conditions of the reactor through an intermediate spallation target. In this work we describe our experimental activities and the numerical tool employed to give a basic characterization of the vacuum dynamics for a windowless interface, with particular regard given to proton beamline and target interface of the Ansaldo A80-XADS reference design.

Design considerations of 10 kW -scale extreme ultraviolet SASE FEL for lithography

Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2001

The semiconductor industry growth is driven to a large extent by steady advancements in microlith... more The semiconductor industry growth is driven to a large extent by steady advancements in microlithography. According to the newly updated industry roadmap, the 70nm generation is anticipated to be available in the year 2008. However, the path to get there is not obvious. The problem of construction of Extreme Ultraviolet (EUV) quantum laser for lithography is still unsolved: progress in

Neutralization of the emittance blowup induced by rf time dependent forces in rf guns

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Overview of ILC

AIP Conference Proceedings, 2007

RF gun emittance correction using unsymmetrical RF cavities

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1992

Characterization of an Elliptical Low Beta Multicell Structure for Pulsed Operation

Design Criteria for Elliptical Cavities

In the framework of the TRASCO project, we have developed a set of criteria to guide the design o... more In the framework of the TRASCO project, we have developed a set of criteria to guide the design of elliptical multicell SC cavities, supporting them with a few design tools to aid the geometry optimisation. In this paper we briefly summarize this work and the related codes we have implemented. Some examples are also given of their applications to cavity

Itaca: A New Computer Code for the Integration of Transient Particle and Field Equations in Axisymmetrical Cavities

Recent Developments at PITZ

Proceedings of the 2005 Particle Accelerator Conference, 2005

FORMATION OF THE Cs 2 Te PHOTOCATHODE: AUGER AND PHOTOEMISSION SPECTROSCOPY STUDY

The formation of the Cs 2 Te photocathode on a mo- lybdenum substrate passes through different ph... more The formation of the Cs 2 Te photocathode on a mo- lybdenum substrate passes through different phases, each of them has been characterised by X-ray photoemission spectroscopy and Auger spectroscopy as well. During the fabrication process different cesium tellurides have been identified in the photoemissive material. The ruggedness to pollution with molecular oxygen at different fabrica- tion stages has been tested. Approximately 5·10 -5 sec·torr of exposition reduces the quantum efficiency to one tenth of its original value. The oxidation damage can be par- tially recovered by simultaneously heating the substrate to ≈ 230 °C and illuminating it with the 4.9 eV ultraviolet radiation. No recovering has been observed under the ef- fect of the temperature or the radiation alone.

High QE photocathodes performance during operation at FLASH / PITZ photoinjectors

2007 IEEE Particle Accelerator Conference (PAC), 2007