Effect of beam position measurement errors on closed orbit correction in a synchrotron

The realization of a fast and robust closed orbit feedback (COFB) system for the on-ramp orbit correction at SIS18 synchrotron of FAIR project is reported in this thesis. SIS18 has some peculiar behaviors including on-ramp optics variation, very short lengths of the ramps (200 ms to 1 s) and a cycle-to-cycle variation of beam parameters. The realized fast COFB system being robust against above mentioned features of SIS18 is a first of its kind and the course to its realization led to some novel contributions in the field of closed orbit correction. A new method relying on the discrete Fourier transform (DFT)-based decomposition of the orbit response matrix (ORM) has been introduced, exploiting the symmetry in the arrangement of beam position monitors (BPMs) and the corrector magnets in the synchrotrons. A nearest-circulant approximation has also been introduced for synchrotrons having slight deviation from the symmetry, making the method applicable to a vast majority of synchrotrons. Moreover, the performance and the stability analysis of COFB systems in the presence of ORM mismatch between the synchrotron and the feedback controller is presented. The COFB systems are divided into slow and fast regimes and a new stability criterion consistent with measurements, is introduced. The practicality of the criterion is verified experimentally at COSY Jülich and is used for the analysis of various sources of ORM mismatch at SIS18. The commissioning of the SIS18 COFB system is also reported in detail which relies on Libera Hadron as the main hardware resource for the controller implementation. The on-ramp orbit correction is demonstrated for the horizontal plane of SIS18, for the disturbance rejection up to 600 Hz.

Download Full-text

High Precision Position Measurement Method for Laguerre-Gaussian Beams Using a Quadrant Detector

Sensors ◽

10.3390/s18114007 ◽

2018 ◽

Vol 18 (11) ◽

pp. 4007 ◽

Cited By ~ 3

Author(s):

Qian Li ◽

Jiabin Wu ◽

Yunshan Chen ◽

Jingyuan Wang ◽

Shijie Gao ◽

...

Keyword(s):

Maximum Error ◽

Least Square ◽

New Method ◽

Beam Radius ◽

Engineering Practice ◽

Gaussian Beams ◽

Good Prospect ◽

Position Measurement ◽

Beam Position ◽

Mean Square Errors

In this paper, we propose a new method to improve the position measurement accuracy for Laguerre-Gaussian beams on a quadrant detector (QD). First, the error effects of the detector diameter and the gap size are taken into account, and the position error compensation factor is introduced into the conventional formula. Then, in order to reduce the number of parameters, the concept of effective radius is proposed. Thus, a new analytical expression is obtained with a best fit using the least square method. It is verified by simulation that this approach can reduce the maximum error by 97.4% when the beam radius is 0.95 mm; meanwhile, the root mean square errors under different radii are all less than 0.004 mm. The results of simulation show that the new method could effectively improve the accuracy of the QD measurement for different radii. Therefore, the new method would have a good prospect in the engineering practice of beam position measurements.

Download Full-text

A phase-space beam position monitor for synchrotron radiation

Journal of Synchrotron Radiation ◽

10.1107/s1600577515007390 ◽

2015 ◽

Vol 22 (4) ◽

pp. 946-955 ◽

Cited By ~ 4

Author(s):

Nazanin Samadi ◽

Bassey Bassey ◽

Mercedes Martinson ◽

George Belev ◽

Les Dallin ◽

...

Keyword(s):

Phase Space ◽

Synchrotron Radiation ◽

Incident Angle ◽

Operating Conditions ◽

Photon Beam ◽

Profile Measurement ◽

Beam Position Monitor ◽

Position Measurement ◽

Beam Position ◽

X Ray

The stability of the photon beam position on synchrotron beamlines is critical for most if not all synchrotron radiation experiments. The position of the beam at the experiment or optical element location is set by the position and angle of the electron beam source as it traverses the magnetic field of the bend-magnet or insertion device. Thus an ideal photon beam monitor would be able to simultaneously measure the photon beam's position and angle, and thus infer the electron beam's position in phase space. X-ray diffraction is commonly used to prepare monochromatic beams on X-ray beamlines usually in the form of a double-crystal monochromator. Diffraction couples the photon wavelength or energy to the incident angle on the lattice planes within the crystal. The beam from such a monochromator will contain a spread of energies due to the vertical divergence of the photon beam from the source. This range of energies can easily cover the absorption edge of a filter element such as iodine at 33.17 keV. A vertical profile measurement of the photon beam footprint with and without the filter can be used to determine the vertical centroid position and angle of the photon beam. In the measurements described here an imaging detector is used to measure these vertical profiles with an iodine filter that horizontally covers part of the monochromatic beam. The goal was to investigate the use of a combined monochromator, filter and detector as a phase-space beam position monitor. The system was tested for sensitivity to position and angle under a number of synchrotron operating conditions, such as normal operations and special operating modes where the photon beam is intentionally altered in position and angle at the source point. The results are comparable with other methods of beam position measurement and indicate that such a system is feasible in situations where part of the synchrotron beam can be used for the phase-space measurement.

Download Full-text

Beam closed orbit correction and feedback by constrained linear least squares method in Hefei light source

High Power Laser and Particle Beams ◽

10.3788/hplpb20102201.0155 ◽

2010 ◽

Vol 22 (1) ◽

pp. 155-158

Author(s):

宣科 Xuan Ke ◽

王琳 Wang Lin ◽

李川 Li Chuan ◽

李为民 Li Weimin ◽

王季刚 Wang Jigang ◽

...

Keyword(s):

Least Squares ◽

Light Source ◽

Least Squares Method ◽

Closed Orbit ◽

Linear Least Squares ◽

Orbit Correction

Download Full-text

Simulation of Closed Orbit Correction for the Nuclotron Booster

Physics of Particles and Nuclei Letters ◽

10.1134/s1547477118070051 ◽

2018 ◽

Vol 15 (7) ◽

pp. 854-857

Author(s):

V. V. Altsybeyev ◽

A. V. Butenko ◽

V. N. Emelianenko ◽

O. Kazinova ◽

V. A. Kozynchenko ◽

...

Keyword(s):

Closed Orbit ◽

Orbit Correction

Download Full-text

Proton beam position measurement in air using a BPM

AIP Advances ◽

10.1063/5.0021497 ◽

2020 ◽

Vol 10 (9) ◽

pp. 095023

Author(s):

Prabir K. Roy ◽

John W. Lewellen ◽

Levi P. Neukirch ◽

Heath A. Watkins

Keyword(s):

Proton Beam ◽

Position Measurement ◽

Beam Position

Download Full-text

CALCULATION OF NONLINEAR TUNE SHIFT USING BEAM POSITION MEASUREMENT RESULTS

International Journal of Modern Physics A ◽

10.1142/s0217751x09044437 ◽

2009 ◽

Vol 24 (05) ◽

pp. 974-986 ◽

Cited By ~ 1

Author(s):

PAVEL SNOPOK ◽

MARTIN BERZ ◽

CAROL JOHNSTONE

Keyword(s):

Linear Optics ◽

Position Measurement ◽

Linear Lattice ◽

Beam Position ◽

Proposed Model ◽

Measurement Results ◽

Tune Shift ◽

Form Transformation ◽

Normal Form Transformation ◽

Shift Calculation

The calculation of the nonlinear tune shift with amplitude based on the results of measurements and the linear lattice information is discussed. The tune shift is calculated based on a set of specific measurements and some extra information which is usually available, namely that about the size and particle distribution in the beam and the linear optics effect on the particles. The method to solve this problem uses the technique of normal form transformation. The proposed model for the nonlinear tune shift calculation is compared to both the numerical results for the nonlinear model of the Tevatron accelerator and the independent approximate formula for the tune shift by Meller et al. The proposed model shows a discrepancy of about 2%.

Download Full-text