Stripline Beam Position Monitor Research Articles

Design and study of cavity quadrupole moment and energy spread monitor

A nondestructive method to measure beam energy spread using the quadrupole modes within a microwave cavity is proposed. Compared with a button beam position monitor (BBPM) or a stripline beam position monitor (SBPM), the cavity monitor is a narrow band pickup and therefore has better signal-to-noise ratio (SNR) and resolution. In this study, a rectangular cavity monitor is designed. TM220 mode operating at 4.76 GHz in the cavity reflects the quadrupole moment of the beam. The cavity plans to be installed behind a bending magnet in Dalian Coherent Light Source (DCLS), an extreme ultraviolet FEL facility. In this position, the beam has a larger dispersion, which is beneficial to measure the energy spread. A quadrupole magnet, a fluorescent screen, and a SBPM with eight electrodes is installed near the cavity for calibration and comparison. The systematic framework and simulation results are also discussed in this paper.

Beam Position Monitor Characterization for the High Energy Photon Source Synchrotron

Beam position monitor (BPM) characterization has been widely studied at the synchrotron. The characteristic impedance of a stripline BPM was designed using a simulation and measured using the time-domain reflectometer method. The mechanical and electrical parameters of the feedthroughs with the buttons used for the BPMs were measured. Special care was taken in the analysis of the consistency of the four channels of the BPM. The feedthroughs were sorted based on their capacitance values. This paper presents the characterization results of the feedthroughs and BPMs. The electro-mechanical offsets were measured using the Lambertson method, and the calibration coefficients were measured using a stretched wire. The BPM differences introduced during mass production were determined by a statistical analysis of the measurement results.

Beam position monitor design for the High Energy Photon Source

A button and stripline beam position monitor (BPM) were designed and developed to achieve sub-micron orbit stability in the High Energy Photon Source (HEPS). Analytical formulae and CST electromagnetic simulation software were used to calculate the radio frequency characteristics of the BPM. The BPM design procedure was developed according to the HEPS requirements. The characteristic impedances of the stripline were designed to be 50 Ω and confirmed by measurements. The position sensitivity, position resolution, capacitance, and wakefield impedance of the button BPM were calculated. The measurement results confirmed that the design satisfied the HEPS requirements.

Experimental investigation of transverse quadrupolar beam oscillation in the Hefei Light Source-II storage ring

Research on the transverse beam dynamics issues and collective bunch behaviors in association with the higher-mode oscillation fields are important in analyzing beam properties and improving machine performance of particle accelerators. In this study, a simple effective excitation and detection scheme was developed to analyze the transverse quadrupole-mode beam oscillation in electron storage rings. Transverse quadrupole-mode beam oscillation was induced by the stripline transverse quadrupole kicker, and then, measured using the stripline beam position monitor in the Hefei Light Source-II storage ring. A spectrum analyzer was employed for the real-time detection of the excitation sidebands of the horizontal quadrupole-mode oscillation in both single-bunch and nominal multi-bunch operations. Additionally, the horizontal dipolar and quadrupolar kick factors are obtained as 6.992 × 1014 and −4.458 × 1014 V/mC with accuracy of 7.49% and 2.03%, respectively, for the single-bunch operation. The dipolar and quadrupolar kick factors in the nominal multi-bunch operation are −2.567 × 1013 and −2.344 × 1013 V/mC with accuracy of 3.53% and 4.91%, respectively. The experimental measurements thus validate the practicability and reliability of this scheme. Moreover, it is demonstrated that this excitation and detection method for the transverse quadrupole oscillation is valid for studying the properties of transverse higher-mode wakefields and related beam behaviors in storage ring light sources.

Design and fabrication of stripline BPM for the ESS MEBT

Beam Position Monitors (BPM) are non-destructive diagnostics devices used in particle accelerators to measure the transverse beam position (beam center of mass) and phase of the accelerated beam. There are various ways of realization of the BPMs in accelerators having different measurement requirements, particle type or energy. Several types of BPM pickups have been studied including the button type, grounded striplines and matched striplines. The choice and final design is based on a matched stripline to accommodate the signal transmission to electronics and provide relatively higher signal level for low velocity (β=0.088) proton beam within MEBT. Due to mechanical space limits, all the BPMs are embedded inside quadrupoles; hence it is required to use non-magnetic materials in the BPM sensor, in particular the feedthroughs. The BPM sensor is composed of several components, which are separately machined with tolerances of 10μm, and then welded together by the use of electron beam welding. The analysis show for long bunches, the multi bunch transfer impedance is different than of single bunch due to bunch signals overlapping. The design, fabrication and tests of the BPM sensors were performed at ESS-Bilbao and their installation and the electrical checks at ESS-Lund. Prior to installation in the ESS accelerator tunnel, one BPM stripline was installed and the BPM system tested with the CEA-IPHI beam. This paper gives an overview of the electromagnetic and mechanical design and the fabrication of BPM striplines. Furthermore, the results of the RF measurements are compared with the simulations.

Proton beam position measurement in air using a BPM

A Beam Position Monitor (BPM) is potentially useful to measure the position and phase of the beam in air in a non-destructive way. An air-gap BPM in experiments, such as beam-induced radioactive waste management and dynamic radiography applications, where a so-called air gap is needed, can be utilized to measure the beam position and phase. In this study, a stripline BPM was used in the air-gap of an 800 MeV proton beam transport line. The downstream end of the primary beamline exit window was made of a thin aluminum plate and allowed the beam to travel 1.2 m in ambient air before re-entering into a vacuum drift section. Such a configuration was arranged to examine the BPM effectiveness in atmospheric temperature and pressure where ionization of air occurs. In this study, a high energy (800 MeV), high current (0.6 A beam peak current/pulse) proton beam of 5 mm radius was transported in the air. The beam position relative to the axis was measured by detecting the signature of the beam in a nanosecond scale. This nanosecond scale detection ability was useful to identify other signals such as plasma effects. The BPM signals were processed at a frequency of 201 MHz; thus, one gets a stronger response in a stripline pattern as it was used in this study instead of a dot-type BPM. Experimental data show that the BPM works well in air, but ionization of air or plasma formation could not be measured over the BPM signal. The design, construction, and performance of a BPM in air environment are presented.

Design and offline testing of a resonant stripline beam position monitor for the IRFEL project at NSRL

A 476 MHz resonant stripline beam position monitor (BPM) is planned to be installed in an infrared free electron laser machine at National Synchrotron Radiation Laboratory. This type of BPM was developed based on a standard stripline BPM by moving the coupling feedthrough closer to the short end downstream, which introduces a resonance and therefore a capability for higher resolution compared with broadband BPMs. The design and offline measurement results of the prototype are shown in this paper. The design goal is the optimization of the central frequencies and corresponding quality factors of the three intrinsic transverse electromagnetic modes to roughly 476 MHz and 30, respectively, the fulfillment of which is demonstrated by a transmission parameter test via a network analyzer. Induced voltage signal modeling and an estimation of the position resolution of the designed BPM are shown in detail. Furthermore, a calibration test of the prototype using the stretched wire method is presented, including a description of the test stand and the evaluation of position sensitivities.

Stripline beam position monitor for X-ray free electron laser of Pohang Accelerator Laboratory.

Beam position monitors (BPMs) are important instruments even in the case of an X-ray free-electron laser (XFEL). Pohang Accelerator Laboratory (PAL) finished the construction of an XFEL (PAL-XFEL) in 2015, and new stripline BPMs were installed in PAL-XFEL. New BPMs were designed to have a strong signal and a high resolution. In addition, the impedance matching was considered to reduce a signal reflection. These features of the BPM design were confirmed with a simulation study as well. Fabricated BPMs were tested by using a wire test stand. Two-dimensional position errors and offsets were measured to select best BPMs for PAL-XFEL. Finally, a real beam test was tried to check the BPM performance and a better resolution than the requirement was obtained.

Design and operation of a prototype interaction point beam collision feedback system for the International Linear Collider

A high-resolution, intratrain position feedback system has been developed to achieve and maintain collisions at the proposed future electron-positron International Linear Collider (ILC). A prototype has been commissioned and tested with a beam in the extraction line of the Accelerator Test Facility at the High Energy Accelerator Research Organization in Japan. It consists of a stripline beam position monitor (BPM) with analogue signal-processing electronics, a custom digital board to perform the feedback calculation, and a stripline kicker driven by a high-current amplifier. The closed-loop feedback latency is 148 ns. For a three-bunch train with 154 ns bunch spacing, the feedback system has been used to stabilize the third bunch to 450 nm. The kicker response is linear, and the feedback performance is maintained, over a correction range of over $\pm$60 {\mu}m. The propagation of the correction has been confirmed by using an independent stripline BPM located downstream of the feedback system. The system has been demonstrated to meet the BPM resolution, beam kick, and latency requirements for the ILC.

High resolution and low charge button and strip-line beam position monitor electronics upgrade at FLASH

Historically the FLASH (Free Electron Laser in Hamburg) facility at DESY (Deutsches Elektronen-Synchrotron) in Germany has foreseen operation in a charge range from 1 nC-3 nC for which a VME based BPM (Beam Position Monitor) system has been in operation since 2005 with a later upgrade to lower charges. In the past few years the standard machine operation settled at a few hundreds of pC with a tendency to smaller charges down to 100 pC and less. The performance of the BPM system at charges below 300 pC was in many locations along the machine unsatisfactory, making the operation of the linac more unstable and less reliable. Therefore a new BPM electronic system based on the utca (Micro Telecommunication Computing Architecture) for physics MTCA.4 standard has been developed to overcome the limitations of the old electronics and has already been successfully in operation in FLASH 2. A substantially improved version of the RF (radio frequency) front-end and digital electronics/firmware has been developed in 2016 and tested successfully. The peak detector electronics have been extended to a double peak detection in four channels and the fully customized Firmware is working machine synchronous. In summer 2017 all old button and strip-line BPM electronics have been replaced with the new type. This paper summarizes the features and performance of the new BPM system, compares the beam jitter free resolution of the old and new BPM system and highlights its high single shot resolution of better than 10 μm rms at a charge of 15 pC.

High Resolution and Low Charge Button and Strip-Line Beam Position Monitor Electronics Upgrade at Flash

High Resolution and Low Charge Button and Strip-Line Beam Position Monitor Electronics Upgrade at Flash

Simulation of a stripline beam position monitor of a single electrode for educational purposes

A beam position monitor is a device used in particle accelerators which determine the position of the beam. In this work, the results obtained by computational simulation and the characterization of a stripline beam position monitor using a single electrode under the action of an electric potential are shown. The electric potential is generated along a copper cable, concentrically located on the monitor, to emulate the particle beam. The simulations were made in COMSOL®, and the response of the electric potential, on the electrode, is shown when varying the position of the copper cable on the vertical axis of the monitor. In addition, the teaching value of the device is discussed.

Prototyping of beam position monitor for medium energy beam transport section of RAON heavy ion accelerator

A heavy ion accelerator, RAON is going to be built by Rare Isotope Science Project in Korea. Its target is to accelerate various stable ions such as uranium, proton, and xenon from electron cyclotron resonance ion source and some rare isotopes from isotope separation on-line. The beam shaping, charge selection, and modulation should be applied to the ions from these ion sources because RAON adopts a superconducting linear accelerator structure for beam acceleration. For such treatment, low energy beam transport, radio frequency quadrupole, and medium energy beam transport (MEBT) will be installed in injector part of RAON accelerator. Recently, development of a prototype of stripline beam position monitor (BPM) to measure the position of ion beams in MEBT section is under way. In this presentation, design of stripline, electromagnetic (EM) simulation results, and RF measurement test results obtained from the prototyped BPM will be described.

Output beam energy measurement of a 100-MeV KOMAC drift tube linac by using a stripline beam position monitor

The 100-MeV proton linac at the KOMAC (Korea Multi-purpose Accelerator Complex) is composed of a 50-keV proton injector, a 3-MeV RFQ (radio-frequency quadrupole) and a 100-MeV DTL (drift tube linac). The proton beam is accelerated from 3 MeV to 100 MeV through 11 DTL tanks. The precise measurement of the proton-beam’s energy at the output of each DTL tank is important for the longitudinal beam dynamics and can be performed by using a time-of-flight method with a BPM (beam position monitor), which is installed between each DTL tank. The details of the output beam energy measurement of the KOMAC DTL with stripline-type BPM and BPM signal processing, along with a comparison with the simulation results, will be presented in this paper.

Design and performance of a high resolution, low latency stripline beam position monitor system

A high-resolution, low-latency beam position monitor (BPM) system has been developed for use in particle accelerators and beam lines that operate with trains of particle bunches with bunch separations as low as several tens of nanoseconds, such as future linear electron-positron colliders and free-electron lasers. The system was tested with electron beams in the extraction line of the Accelerator Test Facility at the High Energy Accelerator Research Organization (KEK) in Japan. It consists of three stripline BPMs instrumented with analogue signal-processing electronics and a custom digitizer for logging the data. The design of the analogue processor units is presented in detail, along with measurements of the system performance. The processor latency is $15.6\ifmmode\pm\else\textpm\fi{}0.1\text{ }\mathrm{ns}$. A single-pass beam position resolution of $291\ifmmode\pm\else\textpm\fi{}10\text{ }\mathrm{nm}$ has been achieved, using a beam with a bunch charge of approximately 1 nC.

HLS Ⅱ储存环条带束流位置检测器的离线标定

HLS Ⅱ储存环条带束流位置检测器的离线标定

Single Pass Stripline Beam Position Monitor Design, Fabrication and Commissioning

To monitor the position of the electron beam during transport from the Booster Synchrotron to the Storage Ring at the Australian Synchrotron, a stripline Beam Position Monitor (BPM) has been designed, fabricated and installed in-house. The design was based on an existing stripline in the Booster and modified for the transfer line with a particular emphasis on ensuring the line impedance is properly matched to the detector system. The initial bench tests of a prototype stripline showed that the fabrication of the four individual striplines in the BPM was made precisely, each with a measured standing wave ratio (SWR) of 1.8 at 500 MHz. Further optimization for impedance matching will be done for new stripline BPMs. The linearity and gain factor was measured with the detector system. The detector system that digitizes the signals is an Instrumentation Technologies Brilliance Single Pass [1]. The results show an error of 1 mm at an offset (from the electrical centre) of 10 mm when a linear gain factor is assumed and an RMS noise of ~150 um that decreases to < 10 um with increasing signal intensity. The results were under our requirements for the transport line. The commissioning results of the stripline will also be presented showing a strong signal for an electron beam with an estimated integrated charge of ~50 nC with a position stability of 28 um (horizontal) and 75 um (vertical).

Libera Brilliance Single Pass束流位置处理器性能测试

In the upgrade of Hefei Light Source (HLS), Libera Brilliance Single Pass is chosen to constitute a signal processing system in order to enhance the overall performance of the injector beam position monitor (BPM) system. The characterization test of the apparatus was made. The mapping of stripline BPM was carried out on a workbench with Libera Brilliance Single Pass. The beam position was tested at HLSs existing 200 MeV linear accelerator using Libera Brilliance Single Pass. The results show that the offline resolution is 4 m to 17 m, better than that of the original logarithmic processing system. The online horizontal and vertical resolution is better than 26 m and 19 m, respectively, also better than the existing systems 58 m and 33 m.

Wake-field in an array of metallic posts: Possible application for beam position monitoring

It is proposed to use an array of metallic posts as a beam position monitor (BPM). The structure consists of a set of N × N metallic vertical posts bounded from above and below by two horizontal metallic plates. The beam position offset from the symmetry axis is determined by measuring the backward radiation emitted by the beam as it traverses the array. The suggested BPM's position resolution is dominated by the thermal noise level and the shot noise level of the detectors measuring the radiation whereas the time resolution is dominated by their operation frequencies. In the optical regime and for ultra-relativistic beams the time resolution is of order of 10 ps i.e. at least two orders of magnitude higher than the common time resolution in stripline BPM. Utilizing the state of the art optical detectors the position resolution of such a BPM may reach the level of a few nanometers which is one order of magnitude better than the common position resolution of existing systems.

Single-pass BPM system of the Photon Factory storage ring.

At the 2.5 GeV ring of the Photon Factory, a single-pass beam-position monitor (BPM) system is being prepared for the storage ring and the beam transport line. In the storage ring, the injected beam position during the first several turns can be measured with a single injection pulse. The BPM system has an adequate performance, useful for the commissioning of the new low-emittance lattice. Several stripline BPMs are being installed in the beam transport line. The continuous monitoring of the orbit in the beam transport line will be useful for the stabilization of the injection energy as well as the injection beam orbit.