IPAC2021 - Classification: MC6: Beam Instrumentation, Controls, Feedback and Operational Aspects / T17 Alignment and Survey

Paper	Title	Page
TUPAB110	Measurement and Correction of RF Kicks in the LCLS Accelerator to Improve Two-Bunch Operation	1644
	R.A. Margraf, F.-J. Decker, Z. Huang, G. Marcus SLAC, Menlo Park, California, USA Z. Huang Stanford University, Stanford, California, USA
	Funding: This work was supported by the Department of Energy, Laboratory Directed Research and Development program at SLAC National Accelerator Laboratory, under contract DE-AC02-76SF00515. RF kicks, caused by a misalignment of an electron beam and acceleration structure, produce an electron orbit in the accelerator which decreases the final energy of the accelerated electron beam and is detrimental to lasing electron bunches in an X-ray Free Electron Laser (XFEL). RF kicks can depend on the RF waveform of the accelerating structure, so controlling this effect is particularly important when two or more electron bunches are accelerated within an RF fill time. Multibunch modes have been successfully developed for the Linac Coherent Light Source (LCLS) accelerator at SLAC,* and are being continually improved to accommodate new experiments. One such experiment, the Cavity-Based XFEL (CBXFEL)** project will require two electron bunches separated by 218.5 ns which must be identical in energy and orbit. To reduce variation in energy and orbit between the two bunches, we studied the RF kicks produced by each of 75 accelerator segments in the LCLS linac at several RF timings. Here, we discuss these measurements and propose a method to correct RF kicks in the LCLS accelerator using corrector dipoles and quadrupoles. * F.-J. Decker, et al. Recent Developments and Plans for Two Bunch Operation, Proc. of FEL2017, TUP023. ** Gabriel Marcus et al. CBXFEL Physics Requirements Document. SLAC-I-120-103-121-00. 2020.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB110
About •	paper received ※ 19 May 2021 paper accepted ※ 15 June 2021 issue date ※ 29 August 2021
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TUPAB307	Robust Optical Instrumentation for Accelerator Alignment Using Frequency Scanning Interferometry	2203
	M. Sosin, H. Mainaud Durand, F. Micolon, V. Rude, J.M. Rutkowski CERN, Meyrin, Switzerland
	The precise alignment of components inside particle accelerators is an important engineering challenge in high-energy physics. Optical interferometry, being a precise, optical distance measurement technique, is often a method of choice in such applications. However, classical fringe-counting interferometers present several drawbacks in terms of system complexity. Due to the increasing availability of broadband, high-speed, sweeping laser sources, Frequency Scanning Interferometry (FSI) based systems, using Fourier analysis of the interference signal, are becoming a subject of growing interest. In the framework of the High-Luminosity LHC project at CERN, a range of FSI-based sensor solutions have been developed and tested. It includes the optical equipment for monitoring the position of cryogenic components inside their cryostats and FSI instrumentation like inclinometers and water-based levelling sensors. This paper presents the results of preliminary tests of these components.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB307
About •	paper received ※ 17 May 2021 paper accepted ※ 07 June 2021 issue date ※ 12 August 2021
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TUPAB308	Mechanical Consolidation of the LHC Inner Triplet Magnet Supporting System for Remote Alignment	2207
	F. Micolon, N. Bourcey, J-B. Deschamps, A. Herty, S. Le Naour, T. Mikkola, V. Parma, D. Ramos, V. Rude, M. Sosin CERN, Meyrin, Switzerland
	Given the high radiation area and the tight alignment tolerances, the LHC inner triplet magnets were designed to be realigned remotely using motorized supporting jacks. However, during run 2 the LHC triplet realignment system started to show an unexpected behavior with erratic load variations on the magnet supporting jacks when operated. It was then decided to freeze any further realignment of the LHC triplet magnet for the remainder of the run. Subsequently, a project team was set up at CERN to understand better the conditions leading to such unexpected behavior and to study and propose a technical consolidation for the realignment system of the LHC triplet magnet. A fully instrumented magnet string using LHC triplet spare magnets was assembled and used at CERN to provide a realistic test bench for this study. This paper reports on the work undertaken to study the triplet magnet overall realignment kinematic, the findings on the readjustment system malfunction and details the consolidation solution implemented for the next LHC run
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB308
About •	paper received ※ 18 May 2021 paper accepted ※ 07 June 2021 issue date ※ 18 August 2021
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TUPAB309	Alignment Verification and Monitoring Strategies for the Sirius Light Source	2210
	R. Oliveira Neto, R. Junqueira Leão, L.R. Leão CNPEM, Campinas, SP, Brazil
	The approach for the alignment of Sirius is the use of portable coordinate metrology instruments in a common reference, via a network of stable points previously surveyed. This type of network is composed of a dense distribution of points materialized in the form of embedded target holders on the special slab and radiation shielding. Phenomena such as ground movements, temperature gradients and vibrations could lead to misalignment of the components, possibly causing a degradation in machine performance. Therefore, the relative positions of the accelerator magnets need to be periodically verified along with the structures surrounding it to ensure a good reference to future alignment operations. This paper will present the status of Sirius monitoring systems, including data from the first months of operation of the hydrostatic levelling sensors. Also, possibilities with simplified network measurements for detecting structural deformations and assessing its stability will be presented, along with a proposal of a photogrammetric reconstruction of the alignment profile of the storage ring. Finally, it will be shown a compilation of analysis on the deformation of the Sirius facilities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB309
About •	paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 27 August 2021
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TUPAB310	Establishing a Metrological Reference Network for the Alignment of Sirius	2214
	H. Geraissate, G.R. Rovigatti de Oliveira LNLS, Campinas, Brazil R. Junqueira Leão CNPEM, Campinas, SP, Brazil
	Sirius is the Brazilian 4th generation synchrotron light source. It consists of three electron accelerators and it has room for up to 38 beamlines. To make the alignment of Sirius components possible, there is a need for a network of points comprising the installation volume, allowing the location of portable coordinate instruments on a common reference frame. This work describes the development of such networks for the whole Sirius facility. The layout of the networks is presented together with the survey strategies. Details are given on how the calculations combined laser trackers and optical level measurements data and how the Earth curvature compensation was performed. A novel laser tracker orientation technique applied for linking networks on different environments is also presented. Finally, the uncertainty estimation for the resulting network and its deformation history is shown.
	Poster TUPAB310 [4.084 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB310
About •	paper received ※ 20 May 2021 paper accepted ※ 07 June 2021 issue date ※ 21 August 2021
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TUPAB311	Nonlinear Correctors Tuning for the Collector Ring Isochronous Mode	2218
	M.A. Lyalin, I. Koop, D.B. Shwartz BINP SB RAS, Novosibirsk, Russia I. Koop, M.A. Lyalin, D.B. Shwartz NSU, Novosibirsk, Russia
	One of the operating modes for the Collector Ring (CR) under construction in Darmstadt is the isochronous mode, in which the captured ions circulate with an equal period regardless of their momentum. The measurement of the orbital period T by the time-of-flight sensors makes it possible to precisely determine the mass to the charge ratio of the ion under study. For this, the change of the circulation period dT should not exceed 1·10^-6 for dT/T in the entire momentum acceptance of the 0.62%. Modeling in the Strategic Accelerator Design code showed that without nonlinear effects compensation, the orbital period variation is 1·10^-5. In this work, the parameters of nonlinear correctors, which are sextupoles and octupoles in CR, are determined, necessary for the isochronous mode implementation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB311
About •	paper received ※ 29 May 2021 paper accepted ※ 16 June 2021 issue date ※ 14 August 2021
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TUPAB313	Arrangement Optimization of Quadrupoles and Correctors for Beam Alignment	2221
	L. Xu, Q.M. Zhang Xi’an Jiaotong University, People’s Republic of China H.X. Deng SARI-CAS, Pudong, Shanghai, People’s Republic of China N. Huang UCAS, Beijing, People’s Republic of China N. Huang SINAP, Shanghai, People’s Republic of China
	In the X-ray free-electron laser (XFEL), the alignment and stability of beam orbit have a great impact on power and qualities of the generated X-ray pulses. Currently, the beam-based alignment (BBA) is the most widely used technique in beam alignment. In order to find the best arrangement of quadrupoles and correctors, a mathematical model is established based on the transmission matrix method. With this model, several simple arrangements of quadrupoles and correctors are selected to simulate the beam alignment process. It is found that when two correctors adjust two quadrupoles, the beam can pass through the center of quadrupoles approximately collimated.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB313
About •	paper received ※ 16 May 2021 paper accepted ※ 31 August 2021 issue date ※ 16 August 2021
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THXB06	Results of the First Alignment Run for Sirius	3728
	R. Junqueira Leão, R. Oliveira Neto CNPEM, Campinas, SP, Brazil H. Geraissate, F. Rodrigues, G.R. Rovigatti de Oliveira LNLS, Campinas, Brazil
	It is widely known that the position of particle accelerator components is critical for its performance. For the latest generation light sources, whose magnetic lattice is optimized for achieving very low emittance, the tolerable misalignments are in the order of a few dozen micrometers. Due to the perimeter of these machines, the requirements push the limits of large-volume dimensional metrology and associated instruments and techniques. Recently a fine alignment campaign of the Sirius accelerators was conducted following the pre-alignment performed during the installation phase. To conform with the strict relative positioning demands, measurement good practices were followed, and several 3D metrology procedures were developed. Also, to improve positioning resolution, high rigidity translation devices were produced. Finally, the special target holders designed as removable fiducials for the magnets were revisited to assure maximum reliability. Data processing algorithms were implemented to evaluate the alignment results in a robust and agile manner. This paper will present the final positioning errors for Sirius magnets with an expression of the estimated uncertainty.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXB06
About •	paper received ※ 20 May 2021 paper accepted ※ 02 July 2021 issue date ※ 01 September 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Measurement and Correction of RF Kicks in the LCLS Accelerator to Improve Two-Bunch Operation

1644

R.A. Margraf, F.-J. Decker, Z. Huang, G. Marcus
SLAC, Menlo Park, California, USA
Z. Huang
Stanford University, Stanford, California, USA

Funding: This work was supported by the Department of Energy, Laboratory Directed Research and Development program at SLAC National Accelerator Laboratory, under contract DE-AC02-76SF00515.
RF kicks, caused by a misalignment of an electron beam and acceleration structure, produce an electron orbit in the accelerator which decreases the final energy of the accelerated electron beam and is detrimental to lasing electron bunches in an X-ray Free Electron Laser (XFEL). RF kicks can depend on the RF waveform of the accelerating structure, so controlling this effect is particularly important when two or more electron bunches are accelerated within an RF fill time. Multibunch modes have been successfully developed for the Linac Coherent Light Source (LCLS) accelerator at SLAC,* and are being continually improved to accommodate new experiments. One such experiment, the Cavity-Based XFEL (CBXFEL)** project will require two electron bunches separated by 218.5 ns which must be identical in energy and orbit. To reduce variation in energy and orbit between the two bunches, we studied the RF kicks produced by each of 75 accelerator segments in the LCLS linac at several RF timings. Here, we discuss these measurements and propose a method to correct RF kicks in the LCLS accelerator using corrector dipoles and quadrupoles.
* F.-J. Decker, et al. Recent Developments and Plans for Two Bunch Operation, Proc. of FEL2017, TUP023.
** Gabriel Marcus et al. CBXFEL Physics Requirements Document. SLAC-I-120-103-121-00. 2020.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB110

About •

paper received ※ 19 May 2021 paper accepted ※ 15 June 2021 issue date ※ 29 August 2021

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reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPAB307

Robust Optical Instrumentation for Accelerator Alignment Using Frequency Scanning Interferometry

2203

M. Sosin, H. Mainaud Durand, F. Micolon, V. Rude, J.M. Rutkowski
CERN, Meyrin, Switzerland

The precise alignment of components inside particle accelerators is an important engineering challenge in high-energy physics. Optical interferometry, being a precise, optical distance measurement technique, is often a method of choice in such applications. However, classical fringe-counting interferometers present several drawbacks in terms of system complexity. Due to the increasing availability of broadband, high-speed, sweeping laser sources, Frequency Scanning Interferometry (FSI) based systems, using Fourier analysis of the interference signal, are becoming a subject of growing interest. In the framework of the High-Luminosity LHC project at CERN, a range of FSI-based sensor solutions have been developed and tested. It includes the optical equipment for monitoring the position of cryogenic components inside their cryostats and FSI instrumentation like inclinometers and water-based levelling sensors. This paper presents the results of preliminary tests of these components.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB307

About •

paper received ※ 17 May 2021 paper accepted ※ 07 June 2021 issue date ※ 12 August 2021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPAB308

Mechanical Consolidation of the LHC Inner Triplet Magnet Supporting System for Remote Alignment

2207

F. Micolon, N. Bourcey, J-B. Deschamps, A. Herty, S. Le Naour, T. Mikkola, V. Parma, D. Ramos, V. Rude, M. Sosin
CERN, Meyrin, Switzerland

Given the high radiation area and the tight alignment tolerances, the LHC inner triplet magnets were designed to be realigned remotely using motorized supporting jacks. However, during run 2 the LHC triplet realignment system started to show an unexpected behavior with erratic load variations on the magnet supporting jacks when operated. It was then decided to freeze any further realignment of the LHC triplet magnet for the remainder of the run. Subsequently, a project team was set up at CERN to understand better the conditions leading to such unexpected behavior and to study and propose a technical consolidation for the realignment system of the LHC triplet magnet. A fully instrumented magnet string using LHC triplet spare magnets was assembled and used at CERN to provide a realistic test bench for this study. This paper reports on the work undertaken to study the triplet magnet overall realignment kinematic, the findings on the readjustment system malfunction and details the consolidation solution implemented for the next LHC run

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB308

About •

paper received ※ 18 May 2021 paper accepted ※ 07 June 2021 issue date ※ 18 August 2021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPAB309

Alignment Verification and Monitoring Strategies for the Sirius Light Source

2210

R. Oliveira Neto, R. Junqueira Leão, L.R. Leão
CNPEM, Campinas, SP, Brazil

The approach for the alignment of Sirius is the use of portable coordinate metrology instruments in a common reference, via a network of stable points previously surveyed. This type of network is composed of a dense distribution of points materialized in the form of embedded target holders on the special slab and radiation shielding. Phenomena such as ground movements, temperature gradients and vibrations could lead to misalignment of the components, possibly causing a degradation in machine performance. Therefore, the relative positions of the accelerator magnets need to be periodically verified along with the structures surrounding it to ensure a good reference to future alignment operations. This paper will present the status of Sirius monitoring systems, including data from the first months of operation of the hydrostatic levelling sensors. Also, possibilities with simplified network measurements for detecting structural deformations and assessing its stability will be presented, along with a proposal of a photogrammetric reconstruction of the alignment profile of the storage ring. Finally, it will be shown a compilation of analysis on the deformation of the Sirius facilities.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB309

About •

paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 27 August 2021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPAB310

Establishing a Metrological Reference Network for the Alignment of Sirius

2214

H. Geraissate, G.R. Rovigatti de Oliveira
LNLS, Campinas, Brazil
R. Junqueira Leão
CNPEM, Campinas, SP, Brazil

Sirius is the Brazilian 4th generation synchrotron light source. It consists of three electron accelerators and it has room for up to 38 beamlines. To make the alignment of Sirius components possible, there is a need for a network of points comprising the installation volume, allowing the location of portable coordinate instruments on a common reference frame. This work describes the development of such networks for the whole Sirius facility. The layout of the networks is presented together with the survey strategies. Details are given on how the calculations combined laser trackers and optical level measurements data and how the Earth curvature compensation was performed. A novel laser tracker orientation technique applied for linking networks on different environments is also presented. Finally, the uncertainty estimation for the resulting network and its deformation history is shown.

Poster TUPAB310 [4.084 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB310

About •

paper received ※ 20 May 2021 paper accepted ※ 07 June 2021 issue date ※ 21 August 2021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPAB311

Nonlinear Correctors Tuning for the Collector Ring Isochronous Mode

2218

M.A. Lyalin, I. Koop, D.B. Shwartz
BINP SB RAS, Novosibirsk, Russia
I. Koop, M.A. Lyalin, D.B. Shwartz
NSU, Novosibirsk, Russia

One of the operating modes for the Collector Ring (CR) under construction in Darmstadt is the isochronous mode, in which the captured ions circulate with an equal period regardless of their momentum. The measurement of the orbital period T by the time-of-flight sensors makes it possible to precisely determine the mass to the charge ratio of the ion under study. For this, the change of the circulation period dT should not exceed 1·10^-6 for dT/T in the entire momentum acceptance of the 0.62%. Modeling in the Strategic Accelerator Design code showed that without nonlinear effects compensation, the orbital period variation is 1·10^-5. In this work, the parameters of nonlinear correctors, which are sextupoles and octupoles in CR, are determined, necessary for the isochronous mode implementation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB311

About •

paper received ※ 29 May 2021 paper accepted ※ 16 June 2021 issue date ※ 14 August 2021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPAB313

Arrangement Optimization of Quadrupoles and Correctors for Beam Alignment

2221

L. Xu, Q.M. Zhang
Xi’an Jiaotong University, People’s Republic of China
H.X. Deng
SARI-CAS, Pudong, Shanghai, People’s Republic of China
N. Huang
UCAS, Beijing, People’s Republic of China
N. Huang
SINAP, Shanghai, People’s Republic of China

In the X-ray free-electron laser (XFEL), the alignment and stability of beam orbit have a great impact on power and qualities of the generated X-ray pulses. Currently, the beam-based alignment (BBA) is the most widely used technique in beam alignment. In order to find the best arrangement of quadrupoles and correctors, a mathematical model is established based on the transmission matrix method. With this model, several simple arrangements of quadrupoles and correctors are selected to simulate the beam alignment process. It is found that when two correctors adjust two quadrupoles, the beam can pass through the center of quadrupoles approximately collimated.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB313

About •

paper received ※ 16 May 2021 paper accepted ※ 31 August 2021 issue date ※ 16 August 2021

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reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THXB06

Results of the First Alignment Run for Sirius

3728

R. Junqueira Leão, R. Oliveira Neto
CNPEM, Campinas, SP, Brazil
H. Geraissate, F. Rodrigues, G.R. Rovigatti de Oliveira
LNLS, Campinas, Brazil

It is widely known that the position of particle accelerator components is critical for its performance. For the latest generation light sources, whose magnetic lattice is optimized for achieving very low emittance, the tolerable misalignments are in the order of a few dozen micrometers. Due to the perimeter of these machines, the requirements push the limits of large-volume dimensional metrology and associated instruments and techniques. Recently a fine alignment campaign of the Sirius accelerators was conducted following the pre-alignment performed during the installation phase. To conform with the strict relative positioning demands, measurement good practices were followed, and several 3D metrology procedures were developed. Also, to improve positioning resolution, high rigidity translation devices were produced. Finally, the special target holders designed as removable fiducials for the magnets were revisited to assure maximum reliability. Data processing algorithms were implemented to evaluate the alignment results in a robust and agile manner. This paper will present the final positioning errors for Sirius magnets with an expression of the estimated uncertainty.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXB06

About •

paper received ※ 20 May 2021 paper accepted ※ 02 July 2021 issue date ※ 01 September 2021

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reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)