Beam Diagnostics Using a Vibrating Wire Monitor

The gradient of the beam is indicated by the difference in color from reference [4]. The halo beam region is denoted by the outer region of the beam core using the ±1σ concept from Ref. Due to the unknown fact about the size of each pixel of the film, the units are arbitrary.

This shifted natural oscillation frequency after beam irradiation is used to construct the beam profile. To diagnose the beam with the appropriate frequency shift value, it is important to set the starting frequency by firmly fixing the end of the wire.

Fig. 2.1.1. Basic figure of Vibrating Wire. There are two permanent magnets at the top and the bottom for each

Beam halo

Gaussian fit is used to the top of the profile to represent the core and then integrate the area by summing the midpoint. The jet halo region is denoted by the outer region of the jet core using the ±1σ concept, from Ref [6]. The wire scanner is the device that uses secondary emission (SEM) of particles after hitting the wire.

VWM assembly

Based on the wire materials, different weight values must be applied to the wire to obtain the correct starting frequency. Finally, it is necessary to know the value of the frequency shifts depending on the VWM position from the center of the beam, which is marked as Position/Sigma in Fig. This can be achieved as the beam density varies based on the position of the wire.

It is very beneficial because it only requires a compact place to install this device and the entire size of the beam can be measured in ms [10]. This solution was suggested by means of computers as the power increases as it reaches the point of 86% of the beam. There are a number of holes on the bottom to facilitate the positioning of the adapter.

A film is applied just before the vibrating wire to compare the result of the profile from the VWM. Here the films are installed just in front of the collimator and the convection protection box. It is installed to obtain a stable signal and the direction of the phase of motion along the beam axis is captured as closely as possible.

Due to the unknown fact of each pixel size of the film, the units are arbitrary. Change in frequency shift is proportional to the change in frequency of the electron beam source. In this LASER experiment, the objective was to measure the beam size and beam profile.

Saturated image of the beam because in this case no neutral density filters were installed. The main advantage of a CCD camera is its sensitivity to light, so that delicate data can be obtained from the beam.

Fig. 2.3.2. Name of the parts of Vibrating Wire.

A string generator

Bethe-Bloch formula

This is the key formula to understand and analyze the beam profile based on the data coming from VWM [8][9]. Equation 2.5.1 can be applied to protons, while 2.4.2 can be applied to electrons and 2.5.3 to low energies, such as a particle with small velocities β <<1. This formula represents the average energy loss per distance of charged particles such as protons and protons, so the beam as a photon beam cannot be exploited with this formula.

VWM parameter choice software

2.6.4) where 𝜎𝑆𝑇𝐵 – Stefan-Boltzmann constant, 𝑇0− Initial temperature of the wire, d-wire diameter, 𝜀 – Emissivity of the wire surface. Since the response time of VWM, 𝜏𝑅𝐸𝑆𝑃 is defined by three thermal mechanisms, such as the following; Conduction, convection and radiation. Moreover, 𝜎𝑆𝐶𝐴𝑁 = 𝜎𝑋 is the case for measurements in the horizontal direction and 𝜎𝑆𝐶𝐴𝑁 = 𝜎𝑌 is the case for measurements in the vertical direction.

Principles of Resonant Target Vibrating Wire Monitor

Beam diameter

The D86 width, to which the name refers, describes the diameter of the circle from the center, which contains 86% of the beam power. The main goal of beam commissioning, which is to deliver 100-MeV, 1-kW proton beams to the bump of the target compartment, has been achieved. In the physics department in UNIST, many studies are going on, and a LASER beam was used to research the photon beam with VWM here in UNIST.

Since the diameter of the beam is very small, accurate measurement with VWM is necessary, and it was an opportunity to know how VWM can accurately measure the small size beam. This movie was used to make a comparison with the beam profile data from VWM. The main reason why the value of 𝐸𝑝=15 MeV is due to the loss of beam energy during its propagation to the target due to the air.

8λS L⁄ +4εσST_BT03πdL+ηχCONVπdL]εHEAT(δp/e)Ip (5.1.2) where F0= (1 L⁄ )√σ0/ρ is the initial frequency of the vibrating wire (L is the length of the wire, σ0) initial voltage of the wire, ρ is the density of wire material), α is the coefficient of thermal expansion of the wire material, E is the modulus of elasticity of the wire material, S is the wire cross-section, λ is the heat conduction coefficient of the wire, 𝑇0 is the initial temperature of the wire, σST_B is the Stefan-Boltzmann constant, ε is the thermal emissivity of the wire ( a measure of the ability of the conductor's surface to radiate energy), χCONV is the coefficient of thermal convective losses (η = 1 for atmosphere and η = 0 for vacuum). The factor −F0αE/2σ0 describes the dependence of the frequency on the line temperature, the factor 1/[8λS L⁄ + 4εσST_BT03πdL + ηχCONVπdL] describes the dependence on the line temperature that increases to the power deposited in the line. The purpose of the 2nd experiment was the following: measuring the beam size and FWHM to compare the result of FWHM data taken by DIRAMS, identify the variation of momentum by changing the effect.

5.2.6, at the distance of 60 mm which is the same distance of the VWM experiment, FWHM is ~7.20 mm with slightly higher RF power compared to the VWM experiment. This is consistent with our prediction that as the RF power increases, the momentum of the jet will also increase. Although a modern technique, RT-VWM was not applied in this experiment, several reasonable data were obtained and explicitly analyzed.

But such facilities need a huge budget and time due to the scale. Kinsho., "A PRELIMINARY STUDY OF THE VIBRATION TEAR MONITOR FOR BEAM HALO DIAGNOSTIC IN J-PARC L3BT".

Fig. 3.1.1. Birds eye view of the KOMAC from, Ref [13].

Dongnam Institute of Radiological and Medical Sciences (DIRAMS)

Ulsan National Institute of Science and Technology (UNIST)

Electron beam

After placing a Thorlabs motion stage on the DIRAMS motion stage, because the Thorlabs motion stage can be controlled more accurately, VW was covered with a convection protection box to make the VW stable. Since the room size of the electron gun is relatively compact and we turned off the air conditioner due to the convection, the room temperature becomes higher and higher during our experiment.

LASER beam

First, there should be no dependence on the degree of movement speed during the beam scan. It is found that there is no dependence on the rate of movement speed as shown in the figure. After turning on the beam, the room temperature naturally rises due to the heat that is exposed to many electrical devices.

With an energy of 20 MeV and a maximum repetition rate of 1 Hz, this experiment was performed in air because there was no vacuum at the time of this experiment. The beam was tested at 2.4 MW of RF power and then at 2.05 MW. Considering other factors such as humidity, temperature and air convection, the FWHM of 7.66 mm of the VWM experiment data is quite reasonable and matches the DIRAMS data.

Due to the rapid development of the LASER industry, such as defense, semiconductor and other applications, etc., there are various types of LASER beam diagnostic equipment. 5.3.7, the result of the VWM data corresponds to the results from the CCD camera in terms of beam shape and diameter. However, VWM proves that this device also measures the radius accurately and also RT-VWM can be used for further research and investigation in the future.

In this case, unlike CCD, after installing diagnostic devices, RT-VWM and VWM do not need to be disassembled, because it does not automatically interrupt the beam after measurement. Due to the development of modern science and technology, many countries are striving to explore further cutting-edge sciences. Bartkoski et al., Development of computational tools for halo analysis and the study of halo growth in a linear spallation neutron source, Tenth European Conference on Particle Accelerators, EPAC 2006, Edinburgh, 2006, e-proceedings (JACoW), p.

Fig. 4.4.1 Frequency shift by motion stage: blue line- 0.2mm/s, red line – 0.05 mm/s, yellow line – 0.01 mm/s speed of the motion stage

Preliminary experiment for VWM operation

Electron beam

The first experiment was done to know how to control the operation of the VW based on the frequency change. RF shielding paper to protect against RF noise and part of the cables were soldered. It is useful because a USB motion stage did not work well when the RF power is increased.

Fig 5.2.3 Shielding effectiveness of the paper.

LASER beam

However, after covering the lens with ND filters, fine figure data was obtained as in the figure. In this perspective, accelerator facilities are mandatory in various fields such as biology, nanotechnology, cosmology and so on. For proton beam, Bethe-Bloch formula was described to analyze and investigate the results of proton beam.

Finally, CCD camera laser beam measurement data were used for comparison with VWM data. In the future, RT-VWM will replace VWM, as it has many more advantages compared to other devices. However, there are many kinds of challenges to be solved, such as RT-VWM software stabilization, convection protection, etc.

By also processing wire material, further research can be done as follows: Gadolinium wire for neutron detector and graphene wire for low energy beam. Scarpine, “Large aperture vibrating wire monitor with two mechanically coupled wires for beam halo measurements Phys. 5] Arutunian S.G., Margaryan A.V., “OSCILLATING WIRE AS A “RESONANT SIGN” FOR BEAM-TRANSVERSAL GRADIENT INVESTIGATION Proceedings of IPAC2014, Dresden, Germany.

7] Arutunian S.G., Davtyan M.M., Vasiniuk I.E., “LARGE APERTURE ELECTRON BEAM SCANNING WITH A VIBRATION MONITOR IN AIR”, Proceedings of IPAC'10, Kyoto, Japan [8] Kye-Ryungta Beam and Prospect. Use in KOMAC,” ICABU'13.