Beam Positioning and Beam Polarization Monitor Based on Large Area HTS Pickup Coils
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46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
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A method for simultaneous linear optics and coupling correction for storage rings with turn-by-turn beam position monitor data
We propose a method to simultaneously correct linear optics errors and linear coupling for storage rings using turn-by-turn (TbT) beam position monitor (BPM) data. The independent component analysis (ICA) method is used to isolate the betatron normal modes from the measured TbT BPM data. The betatron amplitudes and phase advances of the projections of the normal modes on the horizontal and vertical planes are then extracted, which, combined with dispersion measurement, are used to fit the lattice model. The fitting results are used for lattice correction. The method has been successfully demonstrated on the NSLS-II storage ring.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
A Study of Beam Position Diagnostics with Beam-excited Dipole Higher Order Modes using a Downconverter Test Electronics in Third Harmonic 3.9 GHz Superconducting Accelerating Cavities at FLASH
Beam-excited higher order modes (HOM) in accelerating cavities contain transverse beam position information. Previous studies have narrowed down three modal options for beam position diagnostics in the third harmonic 3.9 GHz cavities at FLASH. Localized modes in the beam pipes at approximately 4.1 GHz and in the fifth cavity dipole band at approximately 9 GHz were found, that can provide a local measurement of the beam position. In contrast, propagating modes in the first and second dipole bands between 4.2 and 5.5 GHz can reach a better resolution. All the options were assessed with a specially designed test electronics built by Fermilab. The aim is to define a mode or spectral region suitable for the HOM electronics. Two data analysis techniques are used and compared in extracting beam position information from the dipole HOMs: direct linear regression and singular value decomposition. Current experiments suggest a resolution of 50 {\mu}m accuracy in predicting local beam position using modes in the fifth dipole band, and a global resolution of 20 {\mu}m over the complete module. Based on these results we decided to build a HOM electronics for the second dipole band and the fifth dipole band, so that we will have both high resolution measurements for the whole module, and localized measurements for individual cavity. The prototype electronics is being built by Fermilab and planned to be tested in FLASH by the end of 2012.
43 PARTICLE ACCELERATORS↗
SU-E-T-467: Definition of the Proper Tolerances for Beam-Position Accuracy and Beam Width for Quality Assurance in Active Proton Pencil Beam Scanning
Purpose: To estimate the correlation between different dosimetric indices and the clinical outcome, which was recorded at different time points after the treatment, regarding the structure of salivary glands in head and neck cancer radiotherapy. Methods: 218 salivary glands from patients with head and neck tumours treated at IPOCFG from 2007 to 2013 were included in this study. The follow up of those patients consisted on weekly medical visits during the treatment that take about seven weeks. After that the patients had consults every three months. Treatment complications were graded using the RTOG/EORTC guidelines. The response of the salivary glands (both parotids, oral cavity and both submandibular glands) was analyzed for six time periods: 7th week, 3rd, 7th, 12th, 18th and 24th months after the start of the radiotherapy. The total dose distributions, converted to a fractionation scheme of 2Gy fractional doses, were used to calculate the DVHs and dose-response plots of salivary glands. Results: The small differences obtained between the mean DVHs showed that patients should be grouped into: with complications (G1+G2) and without complications (G0). The mean dose/2Gy was 22.2±13.2 Gy (G0) and 33.2±8.0 Gy (G1+G2) for the 7th week, 31.9±9.6 Gy (G0) and 34.6±6.8 Gy (G1+G2) for the 12th month and, 32.9±9.3 Gy (G0) and 37.2±8.5 Gy (G1+G2) for the 24th month. The dose-response plots for the 7th week and 24th month were similar to the dose-response curves published in the literature. Conclusion: In some cases, there were not major differences between the mean DVHs of the groups with and without complications in the salivary glands, when comparing them at different time periods. More radiobiological analysis should thus be made to estimate the clinical impact of those differences.
60 APPLIED LIFE SCIENCES↗
Correcting Magnetic-Field Diffusion Effects in Beam Position Monitors
Beam position monitors (BPMs) provide timeresolved measurements of the current and centroid position of high-current electron beams in linear induction accelerators (LIAs). The data from some types of BPMs can be influenced by magnetic field diffusion into the surrounding metal. We derive an estimate of the correction factor from first principles, and show how it is applied in practice to nearly eliminate the effect from the data.
43 PARTICLE ACCELERATORS↗
Progress on the development of the next generation x-ray beam position monitors at the advanced photon source
Accurate and stable x-ray beam position monitors (XBPMs) are key elements in obtaining the desired user beam stability in the Advanced Photon Source (APS). The next generation XBPMs for high heat load front ends (HHL FEs) have been designed to meet these requirements by utilizing Cu K-edge x-ray fluorescence (XRF) from a pair of copper absorbers and have been installed at the front ends (FEs) of the APS. Commissioning data showed a significant performance improvement over the existing photoemission-based XBPMs. While a similar design concept can be applied for the canted undulator front ends, where two undulator beams are separated by 1.0-mrad, the lower beam power (< 10 kW) per undulator allows us to explore lower-cost solutions based on Compton scattering from the diamond blades placed edge-on to the x-ray beam. A prototype of the Compton scattering XBPM system was installed at 24-ID-A in May 2015. In this report, the design and test results for XRF-based XBPM and Compton scattering based XBPM are presented. Ongoing research related to the development of the next generation XBPMs on thermal contact resistance of a joint between two solid bodies is also discussed.
43 PARTICLE ACCELERATORS↗
A study of beam position diagnostics using beam-excited dipole modes in third harmonic superconducting accelerating cavities at a free-electron laser
We investigate the feasibility of beam position diagnostics using higher order mode (HOM) signals excited by an electron beam in the third harmonic 3.9 GHz superconducting accelerating cavities at FLASH. After careful theoretical and experimental assessment of the HOM spectrum, three modal choices have been narrowed down to fulfill different diagnostics requirements. These are localized dipole beam-pipe modes, trapped cavity modes from the fifth dipole band, and propagating modes from the first two dipole bands. These modes are treated with various data analysis techniques: modal identification, direct linear regression (DLR), and singular value decomposition (SVD). Promising options for beam diagnostics are found from all three modal choices. This constitutes the first prediction, subsequently confirmed by experiments, of trapped HOMs in third harmonic cavities, and also the first direct comparison of DLR and SVD in the analysis of HOM-based beam diagnostics.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
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.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Fast readout algorithm for cylindrical beam position monitors providing good accuracy for particle bunches with large offsets
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43 PARTICLE ACCELERATORS↗
Development of Electronics for the ATF2 Interaction Point Region Beam Position Monitor
Nanometer resolution beam position monitors have been developed to measure and control beam position stability at the interaction point region of ATF2. The position of the beam has to be measured to within a few nanometers at the interaction point. In order to achieve this performance, electronics for the low-Q IP-BPM was developed. Every component of the electronics have been simulated and checked on the bench and using the ATF2 beam. We will explain each component and define their working range. Then, we will show the performance of the electronics measured with beam signal. ATF2 is a final focus test beam line for ILC in the framework of the ATF international collaboration. The new beam line was constructed to extend the extraction line at ATF, KEK, Japan. The first goal of ATF2 is the acheiving of a 37 nm vertical beam size at focal point (IP). The second goal is to stabilize the beam at the focal point at a few nanometer level for a long period in order to ensure the high luminosity. To achieve these goals a high resolution IP-BPM is essential. In addition for feedback applications a low-Q system is desirable.
43 PARTICLE ACCELERATORS↗
Beam position monitor for energy recovered linac beams
A method of determining the beam position in an energy recovered linac (ERL). The method makes use of in phase and quadrature (I/Q) demodulation techniques to separate the pickup signal generated by the electromagnetic fields generated by the first and second pass beam in the energy recovered linac. The method includes using analog or digital based I/Q demodulation techniques in order to measure the relative amplitude of the signals from a position sensitive beam pickup such as a button, strip line or microstripline beam position monitor.
47 OTHER INSTRUMENTATION↗
Magnetic-Field Diffusion Effects in Beam Position Monitors III: Application to DARHT-II Beam Data
Beam position monitors (BPMs) provide time-resolved measurements of the current and centroid position of high-current electron beams in linear induction accelerators (LIAs). One of the types of detectors used in BPMs is the B-dot loop, which generates a signal from the EMF due to the time varying magnetic flux through the loop. If some of the boundaries of the loop are composed of thick metal walls with finite conductivity, the resulting signal must be corrected for the magnetic field diffusion into the metal. The theoretically predicted flux due to diffusion is in remarkable agreement with experimental measurements. Although accurate BPM measurements of beam current require correction of magnetic field diffusion, accurate measurement of beam position requires no correction. In this note, we present experimental validation of current and position results from a prototype detector employing finite conductivity sensing areas, based on experiments on the DARHT-II LIA.
43 PARTICLE ACCELERATORS↗
Noise estimation of beam position monitors at RHIC
Beam position monitors (BPM) are used to record the average orbits and transverse turn-by-turn displacements of the beam centroid motion. The Relativistic Hadron Ion Collider (RHIC) has 160 BPMs for each plane in each of the Blue and Yellow rings: 72 dual-plane BPMs in the insertion regions (IR) and 176 single-plane modules in the arcs. Each BPM is able to acquire 1024 or 4096 consecutive turn-by-turn beam positions. Inevitably, there are broadband noisy signals in the turn-by-turn data due to BPM electronics as well as other sources. A detailed study of the BPM noise performance is critical for reliable optics measurement and beam dynamics analysis based on turn-by-turn data.
43 PARTICLE ACCELERATORS↗
Electron bunch position determination using a high frequency button beam position monitor in the AWAKE facility
The AWAKE facility uses novel proton beam-driven plasma wakefields to accelerate electron bunches over 10m of Rubidium plasma. Precise monitoring of 2 diverse beam types necessitates an electron beam position monitor (BPM) working in a frequency regime of tens of GHz. A high frequency conical button-style BPM with a working regime of up to 40 GHz has been investigated as a way to discriminate the electromagnetic fields of 19 MeV, 4 ps electron bunches propagating spatially and temporally together with a 400 GeV, 170 ps proton bunch in the AWAKE common beamline. The sensitivity of the HF BPM to the electron beam position is determined under various beam conditions, with both electrons and protons, and integration with a TRIUMF front-end is discussed.
43 PARTICLE ACCELERATORS↗
Electro-optic sampling beam position monitor for relativistic electron beams
Here, an electro-optic sampling beam position monitor for installation at the SLAC National Accelerator Laboratory FACET-II facility is described. Simulations of the detector signal were performed using realistic electron beam current profiles, demonstrating that this single-shot, non-destructive, compact detector is capable of resolving the relative transverse offset and longitudinal separation of an ultra-relativistic, two-bunch electron beam to order 1 μm and 10 fs, respectively. A design study was performed to optimize the detector’s response to the ultra-relativistic two-bunch electron beam utilized in plasma wakefield accelerator experiments. In addition, the expected sensitivity to beam tilt is studied for typical electron beams used in free electron lasers.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Data analysis of photon beam position at PLS-II
In the third generation light source, photon beam position stability is critical issue on user experiment. Generally photon beam position monitors have been developed for the detection of the real photon beam position and the position is controlled by feedback system in order to keep the reference photon beam position. In the PLS-II, photon beam position stability for front end of particular beam line, in which photon beam position monitor is installed, has been obtained less than rms 1μm for user service period. Nevertheless, detail analysis for photon beam position data in order to demonstrate the performance of photon beam position monitor is necessary, since it can be suffers from various unknown noises. (for instance, a back ground contamination due to upstream or downstream dipole radiation, undulator gap dependence, etc.) In this paper, we will describe the start to end study for photon beam position stability and the Singular Value Decomposition (SVD) analysis to demonstrate the reliability on photon beam position data.
43 PARTICLE ACCELERATORS↗
Hybrid monitor for both beam position and tilt of pulsed high-current beams
A Hybrid beam monitor, integrated with both azimuthal and axial B-dot probes, was designed for simultaneous measurement of both beam position and beam angle for pulsed high-current beams at the same location in beam pipe. The output signals of axial B-dot probes were found to be mixed with signals caused by transverse position deviation. In order to eliminate the unwanted signals, an elimination method was developed and its feasibility tested on a 50-Ω coaxial line test stand. By this method, a waveform, shape-like to that of input current and proportional to the tilt angle, was simulated and processed by following integration step to achieve the tilt angle. The tests showed that the measurement error of displacement and tilt angle less than 0.3 mm and 1.5 mrad, respectively. The latter error could be reduced with improved probes by reducing the inductance of the axial B-dot probe, but the improvement reached a limit due to some unknown systemic mechanism.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Magnetic-Field Diffusion Effects in Beam Position Monitors I: Theory
Beam position monitors (BPMs) provide time-resolved measurements of the current and centroid position of high-current electron beams in linear induction accelerators (LIAs). One of the types of detectors used in BPMs is the B-dot loop, which generates a signal from the EMF due to the time varying magnetic flux through the loop. If some of the boundaries of the loop are composed of thick metal walls with finite conductivity, the resulting signal must be corrected for the magnetic field diffusion into the metal. The theoretically predicted flux due to diffusion is in remarkable agreement with experimental measurements
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗