Beam Position Measurement System Research Articles

Study on beam position measurement based on diode detection in HLS-II

In order to improve the sensitivity and long-term stability of beam position measurement for Hefei Light Source – II (HLS-II), it is necessary to improve the measurement method. The beam position monitor (BPM) electronics is used to measure the beam position and is an important part of the beam position measurement system. In this paper, a beam position measurement system based on the compensated diode detection (CDD) technology for electron storage ring was proposed. Since HALF under construction, the parameters of HLS-II were used to design the system and simulate the system circuits to verify its feasibility.

Experimental verification and analysis of the beam loading effect based on precise bunch-by-bunch 3D position measurement

The beam loading effect is one of the main bottlenecks in further improving the performance of synchrotron radiation light sources. Although theoretical analysis and numerical simulation of the beam loading effect have been very well performed, the corresponding diagnostic tools were rather poor, and in most cases, only streak cameras were used to observe the synchronous phase distribution and the intensity distribution in bunch trains. SSRF developed a precise bunch-by-bunch 3D beam position measurement system. This system allows precise measurement and recording of both transient state data and steady-state beam parameters (filling pattern, synchronous phase). Therefore, experimental verification and analysis of the beam loading effect can be more comprehensive and accurate. In this paper, the measurement results of the synchronous phase, synchrotron frequency and synchrotron damping time with and without a third harmonic cavity are introduced and discussed.

New generation of very low noise beam position measurement system for the LHC transverse feedback

Recent studies showed that the transverse feedback system noise floor in the Large Hadron Collider (LHC) must be reduced by at least factor of two in order to operate the machine with large beam-beam tune shift as foreseen in the High Luminosity (HL) LHC. Also, the future feedback system foreseen to suppress the LHC Crab Cavity noise relies on improved noise performance of the beam position measurement system. An upgrade program was launched to lower the LHC transverse feedback system noise floor during the LHC Long Shutdown II. A new generation, very low noise beam position measurement module was developed and tested with beam. Innovative methods in the RF receiver, digital signal processing, thorough optimization of every element in the signal chain from pickup to the kickers allowed to achieve a significant reduction of the system noise floor. This unprecedented noise performance opens also new possibilities for auxiliary instruments, using the position data from the transverse feedback. The paper presents the new system, notable implementation details and measured performance.

Beam position measurement system at HIRFL-CSRm

Beam position measurement system can not only provide the beam position monitoring, but also be used for global orbit correction to reduce beam loss risk and maximize acceptance. The Beam Position Monitors (BPM) are installed along the synchrotron to acquire beam position with the front-end electronics and data acquisition system (DAQ). To realize high precision orbit measurement in the main heavy ion synchrotron and cooling storage ring of heavy-ion research facility in Lanzhou (HIRFL-CSRm), a series of alignment and calibration work has been implemented on the BPM and its DAQ system. This paper analyzed the tests performed in the laboratory as well as with beam based on the developed algorithms and hardware. Several filtering algorithms were designed and implemented on the acquired BPM raw data, then the beam position and resolution were calculated and analyzed. The results show that the position precision was significantly improved from more than 100 μm to about 50 μm by implementing the new designed filtering algorithm. According to the analyzation of the measurement results and upcoming physical requirements, further upgrade scheme for the BPM DAQ system of CSRm based on field programmable gate array (FPGA) technology was proposed and discussed.

A new digital beam position and phase measurement implementation based on a field programmable gate array for the high intensity heavy-ion accelerator iLinac.

A new digital beam position and phase measurement (BPM) system was designed for the ion-Linac accelerator at the high intensity heavy ion accelerator facility. The fundamental and second harmonic signals are retrieved from the BPM electrodes to simultaneously calculate their respective beam positions and phases. All data acquisition and digital signal processing algorithm routines are performed in a field programmable gate array (FPGA). The position and phase information are obtained by using the in-phase and quadrature demodulation method. A practical and straightforward method is used to generate the second harmonic reference signal for processing the second harmonic beam signal. The reconfigurable filters are integrated into the FPGA to allow the measurement of short beam pulse length. The laboratory test results show that the achieved phase resolution is better than 0.2° and 0.03° when the input signal is -60 and -45 dBm, respectively. A position resolution better than 30 μm was achieved for an input power level of approximately -60 dBm, and it can reach 7 μm with the input power higher than -45 dBm. The entire execution time of the algorithm is accomplished within 3.4 µs, which provides a sufficient reaction time for the fast beam interlock signal to the machine protection system. The performance of this newly designed prototype BPM electronics was evaluated with the online proton beam.

A New System for Measuring the Beam Position in the Electron– Positron Transport Channel from the VEPP-3 Storage Ring of the VEPP-4M Collider

A new system for measuring the position of the beam in a pulsed transport channel from the VEPP-3 storage ring to the VEPP-4M collider is discussed, which provides measurement of the position and intensity of an electron or positron beam in one span. For reliable operation of the experimental complex, it is necessary to continuously monitor the beam trajectory in a non-destructive manner, as well as to measure the possible losses of the beam charge. In 2018, new sensors and new electronics of the beam position measurement system were developed, manufactured, and installed in the transportation channel, which provide much greater accuracy compared to the old system. In the new system, it was possible to almost completely eliminate interference and to achieve measurement accuracy better than 0.02 mm, which is more than enough for optimal tuning of the channel optics and achieving high bypass efficiency. The design of the sensor, the structure and the main features of the construction of electronics are described, the accuracy of measurements is analyzed, and some results of the operation of the new system in the channel are given.

Real-Time Phase Correction Based on FPGA in the Beam Position and Phase Measurement System

A fully digital beam position and phase measurement (BPPM) system was designed for the linear accelerator (LINAC) in Accelerator Driven Sub-critical System (ADS) in China. Phase information is obtained from the summed signals from four pick-ups of the Beam Position Monitor (BPM). Considering that the delay variations of different analog circuit channels would introduce phase measurement errors, we propose a new method to tune the digital waveforms of four channels before summation and achieve real-time error correction. The process is based on the vector rotation method and implemented within one single Field Programmable Gate Array (FPGA) device. Tests were conducted to evaluate this correction method and the results indicate that a phase correction precision better than +/- 0.3 degree over the dynamic range from -60 dBm to 0 dBm is achieved.

Beam Position and Phase Measurement System for the Proton Accelerator in ADS

A prototype of a beam position and phase measurement system is designed for the proton accelerator in the China Accelerator Driven Sub-critical system (ADS). The signals from the Beam Position Monitor (BPM) detector are narrow pulses with a repetition frequency of 162.5 MHz and the input amplitude would vary for more than 40 dB. By applying the high-speed high-resolution analog-to-digital conversion technique, the input radio-frequency (RF) signals are directly under sampled to orthogonal streams by precisely adjusting the sampling clock frequency. Compared with the traditional method to obtain the in-phase and quadrature-phase (IQ) data, it simplifies both the analog and digital processing circuits. All signal processing algorithms are integrated within one field programmable gate array (FPGA) chip for a good system simplicity. Initial testing results indicate that this prototype achieves a phase resolution better than 0.03° and a position resolution better than 5 μm over the input amplitude range from -44 dBm to -4 dBm, well beyond the requirement.

LogAmp electronics and optical transmission for the new SPS beam position measurement system

A new front-end board is under development for the CERN SPS Multi ORbit Position System (MOPOS).Based on logarithmic amplifiers, it measures the beamposition over a large dynamic range of beam intensities and resolves the multi-batch structure of the SPS beams. Analogue data are digitized at 10 MS/s, packed in frames by anFPGA and on every turn sent to the readout board, via a 2.4 Gb/s optical transmission link. A first prototype has been successfully tested with several SPS beams. This paper presents an overall description of the system and its capabilities highlighted by the first beammeasurements.

基于四象限光位置检测器的同步光位置测量系统

基于四象限光位置检测器的同步光位置测量系统

A beam position measurement system using quadrupole magnets magnetic centra as the position reference

This measurement system uses a method to measure the beam position with high precision in a storage ring with respect to the quadrupole magnets magnetic centra that is used as the absolute position reference. The absolute position of the pickup elements does not affect the beam position measurements so a calibration of the pickup elements absolute position can be done in situ. This paper describes the system, and shows results from a working system at the MAX I storage ring.

A photon beam position and angle shift measurement system for Aladdin

A system of two reticons has been designed and tested at the Aladdin synchrotron radiation Laboratory of the University of Wisconsin-Madison for the measurement of position and angle shifts of a photon beam line. Each reticon is a linear array of 256 photodiodes with a spatial resolution of 25 μm. The vibrations of the photon beam has been analyzed with this system and an oscillation at 36 Hz with an amplitude of 27 μm was observed. One of the reticons is located in the focal plane of a lens, thereby measuring the photon beam angle shifts. The other one is placed in the imaging plane of the second lens to indicate the changes in the source position. These signals are to be used to control a set of steering dipoles to stabilize the photon beam line.

The New Beam Position Measurement System for the Desy Synchrotron

In the DESY synchrotron a new beam position measurement system has been installed to provide a fast, reliable and precise determination of the closed orbit. The Q-value (6.2 ... 6.3) of the synchrotron leads to a minimum of 25 stations to satisfy that requirement. Due to lack of available space in the straight sections, very short pick-up electrodes of permalloy-taped ring cores were chosen for the technical solution. The low average beam current in the synchrotron operating in the single bunch mode, requires a very sensitive system. This led to a narrow-band resonant device tuned to the revolution frequency of 947 ± 60 kHz followed by a slow scan-processor. For initial operation the output data are transferred to a printer. Later on a link to a computer will be established to provide a fast display of the measured closed orbit, and data for a process computer orbit correction program. First measurements and results with the new system are reported.

Beam Position Measurement System at the Fermilab Main Accelerator

The beam position system of the Fermilab Main Ring contains one horizontal and one vertical Electrostatic Beam Pickup in each of the 96 cells of the machine. A pair of 75 ohm cables transmits the induced signal from the machine tunnel to the nearest service building. In each of the 24 service buildings, there is a solid-state multiplexer and a beam position detector which processes the A-B signal pairs to produce an intensity-normalized voltage proportional to beam displacement. This voltage is digitized, read into buffer of the Lockheed MAC A, and in turn transferred to the Xerox 530. Horizontal or vertical orbits can be obtained ih 50 millisec. Orbits are obtained at injection, and at a Main Ring Sample time, if requested, anywhere on the acceleration cycle. Injection orbits can be flattened automatically by a program that sets dipole trim magnets.