Beam Intensity Measurements Research Articles

Development of a non-intercepting weak beam current measurement electronics for Heavy Ion Accelerator Facility in Lanzhou.

Non-destructive measurements of low-intensity charged particle beams are particularly challenging for beam diagnostics. At the Heavy Ion Accelerator Facility in Lanzhou (HIRFL), beams with weak currents below 1 µA are often provided for experiments. The detection of such low beam current is below the threshold of typical standard beam current transformers. Therefore, a low-intensity monitoring system is developed by using a sensitive capacitive pick-up (PU) and low-noise electronics. This device measures beam currents by digitally analyzing the amplitude of the PU signals using a homodyne detection scheme. During lab tests, the amplitude nonlinearity is <0.5% in the operational range of 1 nA-45 µA and the amplitude resolution is 0.94 nA. At present, four measurement systems for low beam currents are installed at HIRFL for the monitoring of standard operating conditions with low beam currents below 1 µA. After an absolute calibration with a Faraday cup, it can be used for accurate beam intensity measurement with a current resolution of about 1 nA.

A New Wall Current Transformer for Accurate Beam Intensity Measurements in the Large Hadron Collider

The Large Hadron Collider (LHC) stores two high-energy counter-rotating particle beams consisting of multiple bunches of a nanosecond length. Precise knowledge of the number of particles within each bunch, known as the bunch intensity, is crucial for physicists and accelerator operators. From the very beginning of the LHC operation, bunch intensity was measured by four commercial fast beam current transformers (FBCTs) coupling to the beam current. However, the FBCTs exhibited several shortcomings which degraded the measurement accuracy below the required level. A new sensor, the wall current transformer (WCT), has been developed to overcome the FBCT limitations. The WCT consists of eight small radio frequency (RF) current transformers distributed radially around the accelerator’s vacuum chamber. Each transformer couples to a fraction of the image current induced on the vacuum chamber by the passing particle beam. A network of RF combiners sums the outputs of all transformers to produce a single signal which, after integration, is proportional to the bunch intensity. In laboratory tests and during beam measurements, the WCT performance was demonstrated to convincingly exceed that of the FBCT. All originally installed FBCTs were replaced by four WCTs, which have been serving as the LHC reference bunch intensity sensors since 2016.

Simultaneous in-situ x-ray beam profile and intensity measurements with a minimally invasive pixelated diamond monitor

Measuring x-ray beam position, profile, and intensity at synchrotron beamlines provides valuable information for all experiments. Sydor’s transparent x-ray camera (TXC), based on technology originally developed at Brookhaven National Laboratory[1], enables these measurements in-line with experiments for live feedback. The TXC has a low beam profile that fits within a standard vacuum flange width and is composed of diamond material for > 90% transmission of > 5 keV x-rays, minimizing disruption of beamline space and the x-ray beam itself. Standard device parameters include 32 x 32, 60 µm pitch pixels, linearity over a 107 – 1016 photons/s dynamic imaging range, < 40 pA noise floor, and total flux measurement mode. Device performance has been evaluated using a pinhole mask with a benchtop silver x-ray tube and during beam focusing tests at the XFP beamline at NSLS-II and flux characterization at the FAST beamline at CHESS. This work will highlight the features of this commercial beam diagnostic, test results, and future directions and applications of the technology.

Ion beam intensity and phase space measurement techniques for ion sources.

Ion sources produce beams used in accelerators and other applications. Both development and use of ion sources need beam diagnostics to probe the plasma processes and beam formation for optimization purposes and to produce beam parameters needed for transport tuning. These diagnostics include beam intensity measurements usually carried out with Faraday cups or inductive pickups, magnetic separation, profile measurements with scintillation screens and wires, and phase space measurements with different types of emittance scanners.

Performances of current monitor for a long pulse width sensing

The current transformer (CT) is an important part of the current diagnostic system as a non-destructive beam intensity measurement monitor. The bandwidth, sensitivity, precision and droop are some characteristic parameters of a CT. In order to improve the limits of a commercial CTs, an electronic error compensator is developed in this paper. The proposed device compensates the phase error, the droop current through the secondary winding of the transformer and improves the characteristics of commercial sensor systems. The results of measurements demonstrated that the proposed circuit could precisely improve the low frequency response of a commercial CT without using any auxiliary.winding or auxiliary core, or any modification of these CTs. The droop error of the proposed design compared to the first droop remains negligible to the value less than 0.1%/µs, and a consistent sensitivity of 12.4 V/A.

Multidimensional four-wave mixing signals detected by quantum squeezed light

Four-wave mixing (FWM) of optical fields has been extensively used in quantum information processing, sensing, and memories. It also forms a basis for nonlinear spectroscopies such as transient grating, stimulated Raman, and photon echo where phase matching is used to select desired components of the third-order response of matter. Here we report an experimental study of the two-dimensional quantum noise intensity difference spectra of a pair of squeezed beams generated by FWM in hot Rb vapor. The measurement reveals details of the [Formula: see text] susceptibility dressed by the strong pump field which induces an AC Stark shift, with higher spectral resolution compared to classical measurements of probe and conjugate beam intensities. We demonstrate how quantum correlations of squeezed light can be utilized as a spectroscopic tool which unlike their classical counterparts are robust to external noise.

Proton beam intensity and proton fraction measurement of the 2.45 GHz ECR ion source

In this paper we report results of experimental studies of the dependence of the proton beam intensity and proton fraction of the 2.45 GHz electron cyclotron resonance (ECR) ion source on the operational parameters such as extraction voltage, microwave window, impedance matching, gas flow, microwave power, pipeline gas pressure, plasma chamber size, and magnetic field. The DC hydrogen ion beams are measured and analyzed on the bench of ion source and pre-analysis system of the Lanzhou university high intensity neutron generator ZF400. Our results show that a higher proton beam intensity and fraction can be obtained with a microwave window made up of 2 mm AlN. The proton beam intensity and fraction strongly depend on the three-stub tuner that controls the impedance matching between microwave and plasma. We also observe notable beam loss under the lower vacuum pressure condition.

Online measurement of the intensity of keV positron beam

The intensity of keV positron beam generated by 22Na slow positron beam device is weak (generally less than 106 e+/s). Therefore, the traditional method of obtaining beam intensity by Faraday cup is no longer applicable. Currently published methods of obtaining beam intensity are relatively deficient and insufficient. In this paper, a new method was developed to obtain the real-time intensity of positron beam, that is, the HPGe detector was used to collect the 511-keV photons emitted from the thick target bombarded by the positrons, combining with the experimental calibration value of HPGe detector for 511-keV photons as a22Na standard point source placed at the collision point of thick carbon target, and with the relevant parameters got by Monte Carlo simulation. Moreover, the method our group developed and the corrected method of others were both applied for online measurement of beam intensity of 4–9 keV positrons colliding with the pure thick targets (Al, Zn, Nb and Pb). Through comparative analyses, the method our group developed could measure positron beam intensity online more accurately.

Investigation of Compton scattering for gamma beam intensity measurements and perspectives at ELI-NP

Compton γ-ray sources have been in operation for over 30 years with new facilities being under construction or proposed. The gamma beam system under implementation at the Extreme Light Infrastructure - Nuclear Physics facility in Romania will deliver brilliant γ-ray beams with energies up to 19.5 MeV. Several instruments for measuring the parameters of the γ-ray beam are under development at ELI-NP. One of these instruments based on a High Purity Germanium detector is routinely used for beam energy measurements at other facilities. Here we investigate the use of a High Purity Germanium detector to continuously monitor the intensity of the ELI-NP gamma beam by measuring the inelastic scattering of photons. This method relies on both experimental and simulated data and it has been successfully tested during a recent experiment at the High Intensity γ-ray Source facility.

Experimental Study of a Differential Beam Intensity Monitoring for the CIADS LINAC

A BPM based beam loss monitoring scheme for the China initiative accelerator driven subcritical (CIADS) facility has been proposed for the MEBT section of its high power Linac. In this scheme, a differential beam monitoring algorithm is utilized that relies on beam intensity measurements using BPM electrodes. Discussions of the experimental results for the scheme are presented. Further experiments have been performed with some promising results. This paper describes the experimental results with some analyses on measurement errors of the system. The proposed physical design of this system is described and further development is presented.

Upgraded back-end electronics for the CMS Fast Beam Conditions Monitor

Abstract In the CMS experiment, the Fast Beam Conditions Monitor provides an online, bunch-by-bunch measurement of luminosity and machine induced background. The Beam Pickup Transformer provides a precise measurement of beam intensity and arrival time. Upgraded back-end electronics have been developed for the Beam Conditions Monitor, based on the μ TCA standard. This system is slated to replace the current readout systems of both detectors for the next LHC run.

Toward Pulse by Pulse Dosimetry Using an SC CVD Diamond Detector

Solid state detectors with nanosecond response times to incoming radiation are increasingly present at the forefront of radiotherapy dosimetry research. The fast response time of materials, such as diamond, allow pulse by pulse dosimetry. There is a trend in radiotherapy to move toward shorter treatments, using fewer but more intense pulses with varying pulse rates and intensities. This makes the possibility of measuring individual pulses very attractive and would allow intervention during the treatment and not just afterwards. Here, an analogue front end has been developed and combined with a chemical vapor deposition diamond detector to provide real time, pulse by pulse beam intensity measurements. The front end design is discussed and the experimental results obtained using a medical linear accelerator are presented. The results show that the device is capable of pulse by pulse beam intensity measurements up to pulse rates well above 1 kHz. The system performs so well that its variations are negligible compared to the pulse to pulse intensity variations. The dosimetric performance of our system was compared to a commercially available, integrating diamond detector, the microDiamond by PTW. The dose and dose-rate linearity of our system is comparable with the one of the microDiamond and has the additional advantage of being able to measure the deposited dose per pulse.

A Low-Noise Charge Amplifier for the ELENA Trajectory, Orbit, and Intensity Measurement System

A low-noise head amplifier has been developed for the extra low energy antiproton ring beam trajectory, orbit, and intensity measurement system at CERN. This system is based on 24 double-electrode electrostatic beam position monitors installed around the ring. A head amplifier is placed close to each beam position monitor to amplify the electrode signals and generate a difference and a sum signal. These signals are sent to the digital acquisition system, about 50 m away from the ring, where they are digitized and further processed. The beam position can be measured by dividing the difference signal by the sum signal while the sum signal gives information relative to the beam intensity. The head amplifier consists of two discrete charge preamplifiers with junction field effect transistor (JFET) inputs, a sum and a difference stage, and two cable drivers. Special attention has been paid to the amplifier printed circuit board design to minimize the parasitic capacitances and inductances at the charge amplifier stages to meet the gain and noise requirements. The measurements carried out on the head amplifier showed a gain of 40.5 and 46.5 dB for the sum and difference outputs with a bandwidth from 200 Hz to 75 MHz and an input voltage noise density lower than $400~\text {pV}/\surd \text{Hz}$ . Twenty head amplifiers have been already installed in the ring and they have been used to detect the first beam signals during the first commissioning stage in November 2016.

Antisolvent crystallization of aqueous ammonium dihydrogen phosphate solutions by addition of methanol

Experimental results of antisolvent crystallization of ammonium dihydrogen phosphate from their aqueous solutions saturated at 30°C by addition of methanol at preselected feeding rate RA, studied by in situ measurements of laser beam intensity I transmitted through solutions and their temperature T as functions of feeding time t for methanol at rate RA, are described and discussed. It was found that (1) measurement of temperature of solutions during antisolvent feeding is more informative and is more reliable than transmitted laser beam intensity measurements, (2) there are two regions of methanol feeding durations involving endothermic reactions and one region involving exothermic reactions, (3) the data of metastable zone width determined from the values of maximum antisolvent content Δxmax calculated from methanol feeding duration are reliable when the temperature difference ΔT=Ts−Tw, where Ts and Tw are temperatures of solution and water, respectively, for theoretical analysis, (4) rates ΔT/Δt of linear changes in temperatures of solution and water with methanol feeding time t increases with feeding rate RA, and (5) the maximum changes ΔTmax in the temperature of solution and water are related to antisolvent content Δx associated with their appearance. It is argued that feeding of antisolvent methanol to saturated solutions or water leads to chemical reactions with evolution of heat.

100-MeV proton beam intensity measurement by Au activation analysis using 197Au(p, pn)196Au and 197Au(p, p3n)194Au reactions

The proton beam intensity of a 100-MeV proton linac at the Korea Multi-purpose Accelerator Complex (KOMAC) was measured by an Au activation analysis using 197Au(p,pn)196Au and 197Au(p,p3n)194Au reactions to determine the accuracy and precision of beam intensity measurement using Gafchromic film dosimetry method. The target, irradiated by 100-MeV protons, was arranged in a stack consisting of Au, Al foils and Pb plates. The yields of produced radio-nuclei in Au foils were obtained by gamma-ray spectroscopy. The FLUKA code was employed to calculate the energy spectrum of protons onto the front surface of Au foils located at three different depth points of the target and also to investigate the condition of incident beam on the target. A good agreement was found between the beam intensity measurements using the activation analysis method at three different depth points of the target. An excellent agreement was also observed between the beam intensity measurements using the Au activation analysis method and the dosimetry method using Gafchromic film.

Neutron Energy Spectra and Yields from the 7Li(p,n) Reaction for Nuclear Astrophysics

Neutrons produced by the 7Li(p, n)7Be reaction close to threshold are widely used to measure the cross section of s-process nucleosynthesis reactions. While experiments have been performed so far with Van de Graaff accelerators, the use of RF accelerators with higher intensities is planned to enable investigations on radioactive isotopes. In parallel, high-power Li targets for the production of high-intensity neutrons at stellar energies are developed at Goethe University (Frankfurt, Germany) and SARAF (Soreq NRC, Israel). However, such setups pose severe challenges for the measurement of the proton beam intensity or the neutron fluence. In order to develop appropriate methods, we studied in detail the neutron energy distribution and intensity produced by the thick-target 7Li(p,n)7Be reaction and compared them to state-of- the-art simulation codes. Measurements were performed with the bunched and chopped proton beam at the Van de Graaff facility of the Institute for Reference Materials and Measurements (IRMM) using the time-of-flight (TOF) technique with thin (1/8") and thick (1") detectors. The importance of detailed simulations of the detector structure and geometry for the conversion of TOF to a neutron energy is stressed. The measured neutron spectra are consistent with those previously reported and agree well with Monte Carlo simulations that include experimentally determined 7Li(p,n) cross sections, two-body kinematics and proton energy loss in the Li-target.

Demonstration of the importance of a dedicated neutron beam monitoring system for BNCT facility

The neutron beam monitoring system is indispensable to BNCT facility in order to achieve an accurate patient dose delivery. The neutron beam monitoring of a reactor-based BNCT (RB-BNCT) facility can be implemented through the instrumentation and control system of a reactor provided that the reactor power level remains constant during reactor operation. However, since the neutron flux in reactor core is highly correlative to complicated reactor kinetics resulting from such as fuel depletion, poison production, and control blade movement, some extent of variation may occur in the spatial distribution of neutron flux in reactor core. Therefore, a dedicated neutron beam monitoring system is needed to be installed in the vicinity of the beam path close to the beam exit of the RB-BNCT facility, where it can measure the BNCT beam intensity as closely as possible and be free from the influence of the objects present around the beam exit. In this study, in order to demonstrate the importance of a dedicated BNCT neutron beam monitoring system, the signals originating from the two in-core neutron detectors installed at THOR were extracted and compared with the three dedicated neutron beam monitors of the THOR BNCT facility. The correlation of the readings between the in-core neutron detectors and the BNCT neutron beam monitors was established to evaluate the improvable quality of the beam intensity measurement inferred by the in-core neutron detectors. In 29 sampled intervals within 16 days of measurement, the fluctuations in the mean value of the normalized ratios between readings of the three BNCT neutron beam monitors lay within 0.2%. However, the normalized ratios of readings of the two in-core neutron detectors to one of the BNCT neutron beam monitors show great fluctuations of 5.9% and 17.5%, respectively.

HLSⅡ新的注入器束流强度测量系统

HLSⅡ新的注入器束流强度测量系统

New beam intensity measurement system for HLSII injector

New beam intensity measurement system for HLSII injector

A compact and portable X-ray beam position monitor using Medipix3

The present work reports on the design and implementation of a novel portable X-ray beam diagnostics (XBPM) device. The device is transparent to the X-ray beam and provides real-time measurements of beam position, intensity, and size. The measurement principle is based on a pinhole camera which records scattered radiation from a Kapton foil which is placed in the beam path. The use of hybrid detectors (Medipix3) that feature a virtually noiseless readout system with capability of single photon detection and energy resolving power enables the diagnostics with a better resolution and higher sensitivity compared to the use of traditional indirect X-ray detection schemes. We describe the detailed system design, which consists of a vacuum compatible focal plane sensor array, a sensor conditioning and readout board and a heterogeneous data processing unit, which also acts as a network server that handles network communications with clients. The readout protocol for the Medipix3 sensor is implemented using field programmable gate array (FPGA) logic resulting in a versatile and scalable system that is capable of performing advanced functions such as data compression techniques and feature extraction. For the system performance measurements, we equipped the instrument with a single Medipix3 die, bump bonded to a Si sensor, rather than four for which it was designed. Without data compression, it is capable of acquiring magnified images and profiles of synchrotron X-ray beams at a transfer rate through Ethernet of 27 frames/s for one Medipix3 die.