Cavity Beam Position Monitor Research Articles

Principal Component Analysis of cavity beam position monitor signals

Model-independent analysis (MIA) methods are generally useful foranalysing complex systems in which relationships between theobservables are non-trivial and noise is present. Principal ComponentAnalysis (PCA) is one of MIA methods allowing to isolate components inthe input data graded to their contribution to the variability of thedata. In this publication we show how the PCA can be applied todigitised signals obtained from a cavity beam position monitor (CBPM)system on the example of a 3-cavity test system installed at theAccelerator Test Facility 2 (ATF2) at KEK in Japan. We demonstratethat the PCA based method can be used to extract beam positioninformation, and matches conventional techniques in terms ofperformance, while requiring considerably less settings and data forcalibration.

Design and test of SX-FEL cavity BPM

This paper reports the design and cold test of the cavity beam position monitor (CBPM) for SX-FEL to fulfill the requirement of beam position measurement resolution of less than 1 μm, even 0.1 μm. The CBPM was optimized by using a coupling slot to damp the TM010 mode in the output signal. The isolation of TM010 mode is about 117 dB, and the shunt impedance is about 200 Ω@4.65 GHz with the quality factor 80 from MAFIA simulation and test result. A special antenna was designed to load power for reducing excitation of other modes in the cavity. The resulting output power of TM110 mode was about 90 mV/mm when the source was 6 dBm, and the accomplishable minimum voltage was about 200 μV. The resolution of the CBPM was about 0.1 μm from the linear fitting result based on the cold test.

Design of the X-band cavity beam position monitor

The free-electron laser (FEL) is a fourth-generation light source producing coherent X-rays by using an interaction between the electromagnetic field and the electron bunch. Producing coherent X-rays requires sub-micron beam alignment in the undulator section of the FEL. The cavity beam position monitor (BPM), as a non-destructive diagnostics tool, can provide sub-micron resolution in the beam position reading. In this research, an X-band cavity BPM were modelled and simulated. The RF properties and the signal response of the cavity BPM were calculated by using an electromagnetic field simulation program (CST Studio Suite).

Cavity Beam Position Monitor Test System Based on Virtual Instrument

Based on the virtual instrument technology, a dedicated test system has been developed for cavity beam position monitor (CBPM). The system consists of commercial nanopositioning stage and its controller, the analog output DAQ card based on PXI and network analyzer. In the LABVIEW environment, software which implemented function of instrument control and data acquisition based on virtual instrument soft architecture (VISA) has been developed. Experimental results illustrated that the test system achieved positioning precision of sub micron which meets requirement of test of CBPM. Also it could serve CBPM signal processing system.

A metrology system for a high resolution cavity beam position monitor system

International Linear Collider (ILC) interaction region beam sizes and component position stability requirements will likely be as small as a few nanometers. It is important to the ILC design effort to demonstrate that these tolerances can be achieved–ideally using a beam-based stability measurement. We developed a high resolution RF cavity Beam Position Monitor (BPM) system. A triplet of these BPMs, installed in the extraction line of the KEK Accelerator Test Facility (ATF) and tested with its ultra-low emittance beam, achieved a position measurement resolution of 15nm. A metrology system for the three BPMs was subsequently installed. This system employed optical encoders to measure each BPM's position and orientation relative to a zero-coefficient of thermal expansion carbon fiber frame. We have demonstrated that the three BPMs behave as a rigid-body at the level of less than 5nm.

Development of an S-band cavity Beam Position Monitor for ATF2

We have developed an S-band cavity Beam Position Monitor (BPM) in order to measure the position of an electron beam in the final focus area at ATF2, which is the test facility for the final focus design for the International Linear Collider (ILC). The lattice of the ILC Beam Delivery System (BDS) has been modified, requiring a larger physical aperture of 40 mm in the final focus area. The beam orbit measurement in this area is now covered with high resolution S-Band cavity BPMs. In this paper we summarize the design of the cavity BPM and the first experimental results. The calibration slopes were measured as 0.87 counts/μm in the x-coordinate direction and 1.16 counts/μm in the y-coordinate direction.

Design and cold test of a rectangular cavity beam position monitor

The CBPM is a kind of monitor which is used for the measurement of beam transverse position. It is becoming increasingly popular due to its high potential in resolution performance. In theory, the resolution can reach about 1 nanometer. In this paper, a rectangular CBPM is designed for it has better X-Y isolation than a cylindrical one. It has been simulated and measured, and the results agree with each other very well. The procedures and results for the simulation and the cold test will be shown later and it will be proved that this is a reliable method for the CBPM design.

Sub-micron resolution rf cavity beam position monitor system at the SACLA XFEL facility

We have developed and constructed a C-band (4.760GHz) rf cavity beam position monitor (RF-BPM) system for the XFEL facility at SPring-8, SACLA. The demanded position resolution of the RF-BPM is less than 1μm, because an electron beam and x-rays must be overlapped within 4μm precision in the undulator section for sufficient FEL interaction between the electrons and x-rays. In total, 57 RF-BPMs, including IQ demodulators and high-speed waveform digitizers for signal processing, were produced and installed into SACLA. We evaluated the position resolutions of 20 RF-BPMs in the undulator section by using a 7GeV electron beam having a 0.1nC bunch charge. The position resolution was measured to be less than 0.6μm, which was sufficient for the XFEL lasing in the wavelength region of 0.1nm, or shorter.

Cavity beam position monitor system for the Accelerator Test Facility 2

The Accelerator Test Facility 2 (ATF2) is a scaled demonstrator system for final focus beam lines of linear high energy colliders. This paper describes the high resolution cavity beam position monitor (BPM) system, which is a part of the ATF2 diagnostics. Two types of cavity BPMs are used, C-band operating at 6.423 GHz, and S-band at 2.888 GHz with an increased beam aperture. The cavities, electronics, and digital processing are described. The resolution of the C-band system with attenuators was determined to be approximately 250 nm and 1 m for the S-band system. Without attenuation the best recorded C-band cavity resolution was 27 nm.

A novel electromagnetic design and a new manufacturing process for the cavity BPM (Beam Position Monitor)

The Cavity Beam Position Monitor (BPM) is a beam diagnostic instrument which, in a seeded Free Electron Laser (FEL), allows the measurement of the electron beam position in a non-destructive way and with sub-micron resolution. It is composed by two resonant cavities called reference and position cavity, respectively. The measurement exploits the dipole mode that arises when the electron bunch passes off axis. In this paper we describe the Cavity BPM that has been designed and realized in the context of the FERMI@Elettra project [1] . New strategies have been adopted for the microwave design, for both the reference and the position cavities. Both cavities have been simulated by means of Ansoft HFSS [2] and CST Particle Studio [3] , and have been realized using high precision lathe and wire-EDM (Electro-Discharge) machine, with a new technique that avoids the use of the sinker-EDM machine. Tuners have been used to accurately adjust the working frequencies for both cavities. The RF parameters have been estimated, and the modifications of the resonant frequencies produced by brazing and tuning have been evaluated. Finally, the Cavity BPM has been installed and tested in the presence of the electron beam.

Design and experiments for the waveguide to coaxial cable adapter of a cavity beam position monitor

The waveguide to coaxial cable adapter is very important to the cavity beam position monitor (CBPM) because it determines how much of the energy in the cavity could be coupled outside. In this paper, the waveguide to coaxial cable adapter of a CBPM is designed and experiments are conducted. The curve shapes of experiments and simulations are very similar and the difference in reflection is less than 0.1. This progress provides a reliable method for designing the adapter.

Design Studies for a High Resolution Cold Cavity Beam Position Monitor

In order to preserve a low emittance beam along the ~11 km long main linacs of the International Linear Collider (ILC), precise monitoring and control of the beam orbit is mandatory. A resolution <; 1 μm is required for the beam position monitors (BPM), which are located inside the cryomodules, i.e. operated at cryogenic temperatures. By using the electromagnetic field simulation programs (CST Studio Suite), we have designed a high resolution cold cavity BPM, operating in the L-Band at a 1.3 GHz dipole-mode frequency. This enables the measurement of the beam position with a Project-X like beam structure, as well as with ILC beam parameters at the superconducting RF test accelerator in the Fermilab New Muon Lab (NML) building. The results of the design studies predicts a resolution potential of a few hundred nanometers with a signal decay time of 50 ns.

Simulation and experiments for the Qext of a cavity beam position monitor

The external Q (Qext) of the dipole mode is a key parameter of the Cavity Beam Position Monitor (CBPM). It determines the amplitude and length of the dipole mode signal. In this paper, Qext of a CBPM whose waveguides were open to the air was simulated and measured, and the results agreed with each other. Then four waveguide-to-coaxial cable adpaters were adjusted and assembled to the CBPM, and Qext remained unchanged. This progress provides a reliable method to evaluate Qext in the physics design without simulating the structurally complex adapters.

Performance of a reentrant cavity beam position monitor

The beam-based alignment and feedback systems, essential operations for the future colliders, require high resolution beam position monitors (BPMs). In the framework of the European CARE/SRF program, a reentrant cavity BPM with its associated electronics was developed by the CEA/DSM/Irfu in collaboration with DESY. The design, the fabrication, and the beam test of this monitor are detailed within this paper. This BPM is designed to be inserted in a cryomodule, work at cryogenic temperature in a clean environment. It has achieved a resolution better than $10\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ and has the possibility to perform bunch to bunch measurements for the x-ray free electron laser (X-FEL) and the International Linear Collider (ILC). Its other features are a small size of the rf cavity, a large aperture (78 mm), and an excellent linearity. A first prototype of a reentrant cavity BPM was installed in the free electron laser in Hamburg (FLASH), at Deutsches Elektronen-Synchrotron (DESY) and demonstrated its operation at cryogenic temperature inside a cryomodule. The second, installed, also, in the FLASH linac to be tested with beam, measured a resolution of approximately $4\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ over a dynamic range $\ifmmode\pm\else\textpm\fi{}5\text{ }\text{ }\mathrm{mm}$ in single bunch.

Cavity BPM system tests for the ILC energy spectrometer

The main physics programme of the International Linear Collider (ILC) requires a measurement of the beam energy at the interaction point with an accuracy of 10-4 or better. To achieve this goal a magnetic spectrometer using high resolution beam position monitors (BPMs) has been proposed. This paper reports on the cavity BPM system that was deployed to test this proposal. We demonstrate sub-micron resolution and micron level stability over 20h for a 1m long BPM triplet. We find micron-level stability over 1h for 3 BPM stations distributed over a 30m long baseline. The understanding of the behaviour and response of the BPMs gained from this work has allowed full spectrometer tests to be carried out.

RF measurements of a C-band cavity beam position monitor**Supported by Development Plan of the State Key Fundamental Research (2002CB713600)

RF cold test of a novel C-band cavity beam position monitor (PBM) to be used in the SDUVFEL Test Facility is described. The test results are presented and some characteristics discussed. The main parameters obtained are in reasonable agreement with the analytical estimations. Effective suppression of the common mode has been demonstrated. The position sensitivity over the test region of ±0.5 mm is about −21.58 dB/10 μm for the TM110 mode and is linear in the central region of the BPM cavity.

Design of a Low-Q S-Band Cavity Beam Position Monitor

Design of a Low-Q S-Band Cavity Beam Position Monitor

Performance of a high resolution cavity beam position monitor system

It has been estimated that an RF cavity Beam Position Monitor (BPM) could provide a position measurement resolution of less than 1 nm. We have developed a high resolution cavity BPM and associated electronics. A triplet comprised of these BPMs was installed in the extraction line of the Accelerator Test Facility (ATF) at the High Energy Accelerator Research Organization (KEK) for testing with its ultra-low emittance beam. The three BPMs were each rigidly mounted inside an alignment frame on six variable-length struts which could be used to move the BPMs in position and angle. We have developed novel methods for extracting the position and tilt information from the BPM signals including a robust calibration algorithm which is immune to beam jitter. To date, we have demonstrated a position resolution of 15.6 nm and a tilt resolution of 2.1 μ rad over a dynamic range of approximately ± 20 μ m .