Measurement of ion beam profiles in a superconducting linac with a laser wire (original) (raw)
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Laser wire beam profile monitor in the spallation neutron source (SNS) superconducting linac
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2010
The spallation neutron source (SNS) at Oak Ridge National Laboratory is an accelerator-based, neutron-scattering facility. SNS uses a large-scale, high-energy superconducting linac (SCL) to provide high beam power utilizing hydrogen ion (H−) beams. For the diagnostics of high-brightness H− beams in the SCL, nonintrusive methods are preferred. This paper describes design, implementation, theoretical analysis, and experimental demonstration of a nonintrusive profile monitor system based on photodetachment, also known as laser wire, installed in the SNS SCL. The SNS laser wire system is the world's largest of its kind with a capability of measuring horizontal and vertical profiles of an operational H− beam at each of the 23 cryomodule stations along the SCL beam line by employing a single light source. Presently 9 laser wire stations have been commissioned that measure profiles of the H− beam at energy levels from 200 MeV to 1 GeV. The laser wire diagnostics has no moving parts inside the beam pipe, causes no contamination on the superconducting cavity, and can be run parasitically on an operational neutron production H− beam.
Laser Based Diagnostics for Measuring H- Beam Parameters
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In recent years, a number of laser based H- beam diagnostics systems have been developed in the Spallation Neutron Source (SNS). This talk reviews three types of laser-based diagnostics at SNS: the laser wire profile monitors at superconducting linac (SCL), the laser based transverse emittance measurement system at high energy beam transport (HEBT), and the laser bunch shape monitor at
A laser-wire beam-energy and beam-profile monitor at the BNL linac
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In 2009 a beam-energy monitor was installed in the high energy beam transport (HEBT) line at the Brookhaven National Lab linac. This device measures the energies of electrons stripped from the 40mA H beam by background gas. Electrons are stripped by the 2.0x10torr residual gas at a rate of 1.5x10/cm. Since beam electrons have the same velocities as beam protons,
Beam-Based Measurements of the ISAC-II Superconducting Heavy Ion Linac
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Preparation for experiments, which typically run for one to two weeks in the ISAC-II facility at TRIUMF, requires some amount of overhead, limiting the efficiency of the facility. Efforts are underway to improve the ISAC-II linac model to reduce this overhead while also improving the quality of the delivered ion beam. This can be accomplished with beam-based measurements and corrections of alignment, cavity gradients, focal strengths, and more. A review of the present state of the linac will be given, including measured mis-alignments and other factors that affect the reproducibility of tunes. The outlook on expected improvements will also be summarized, including progress on the automatic phasing of cavities with a focus on integration to the High Level Application platform being developed at TRIUMF. Lastly, a summary will be given on the expected paradigm shift in the tuning approach taken: moving from re-active tuning by operators or beam delivery experts to pro-active measuremen...
Optics Express, 2011
A high peak-power Q-switched laser has been used to monitor the ion beam profiles in the superconducting linac at the Spallation Neutron Source (SNS). The laser beam suffers from position drift due to movement, vibration, or thermal effects on the optical components in the 250-meter long laser beam transport line. We have designed, bench-tested, and implemented a beam position stabilization system by using an Ethernet CMOS camera, computer image processing and analysis, and a piezodriven mirror platform. The system can respond at frequencies up to 30 Hz with a high position detection accuracy. With the beam stabilization system, we have achieved a laser beam pointing stability within a range of 2 μrad (horizontal) to 4 μrad (vertical), corresponding to beam drifts of only 0.5 mm × 1 mm at the furthest measurement station located 250 meters away from the light source.
Instrumentation for diagnostics and control of laser-accelerated proton (ion) beams
Physica Medica, 2014
Suitable instrumentation for laser-accelerated proton (ion) beams is critical for development of integrated, laser-driven ion accelerator systems. Instrumentation aimed at beam diagnostics and control must be applied to the driving laser pulse, the lasereplasma that forms at the target and the emergent proton (ion) bunch in a correlated way to develop these novel accelerators. This report is a brief overview of established diagnostic techniques and new developments based on material presented at the first workshop on 'Instrumentation for Diagnostics and Control of Laser-accelerated Proton (Ion) Beams' in Abingdon, UK. It includes radiochromic film (RCF), image plates (IP), micro-channel plates (MCP), Thomson spectrometers, prompt inline scintillators, time and space-resolved interferometry (TASRI) and nuclear activation schemes. Repetition-rated instrumentation requirements for target metrology are also addressed.
Laser-based profile and energy monitor for H- beams
2008
A beam profile and energy monitor for H{sup -} beams based on laser photoneutralization was built at Brookhaven National Laboratory (BNL)* for use on the High Intensity Neutrino Source (HMS) at Fermilab. An H{sup -} ion has a first ionization potential of 0.75eV and can be neutralized by light from a Nd:YAG laser ({lambda}=1064nm). To measure beam profiles, a narrow laser beam is stepped across the ion beam, removing electrons from the portion of the H{sup -} beam intercepted by the laser. These electrons are channeled into a Faraday cup by a curved axial magnetic field. To measure the energy distribution of the electrons, the laser position is fixed and the voltage on a screen in front of the Faraday cup is raised in small steps. We present a model which reproduces the measured energy spectrum from calculated beam energy and space-charge fields. Measurements are reported from experiments in the BNL linac MEBT at 750keV.
10th International Beam Instrumentation Conference (IBIC'21), Pohang, Rep. of Korea, 24-28 May 2021, 2021
We demonstrate a novel technique to measure the longitudinal profile of an operational hydrogen ion (H-) beam in a nonintrusive, real-time fashion. The measurement is based on the photoionization of the ion beam with a phase modulated laser comb-pico-second laser pulses with controllable temporal structure. The measurement technique has been applied to a 1-GeV, 1.4-MW Hbeam at the Spallation Neutron Source (SNS) high energy beam transport (HEBT). A stroboscopic photograph of the Hbeam micro bunch can be obtained by using a phase modulated laser comb. The entire measurement takes only 700 s.
Development on Pulsed Laser Wire for Measurement of Beam Profile
2014
Production and handling of low emittance beam is important technology for linear colliders. For the view point of high energy experiments, luminosity and energy of collider is very important. So damping ring generates low emittance beam by radiation damping process. The advent of laser based beam profile monitor has increased the scope of studying low emittance beam dynamics. An Accelerator Test Facility (ATF) was built at KEK in hope of developing techniques for the low emittance beam. It consists of an electron linac, a damping ring in which beam emittance is reduced and an extraction line. The damping ring has two arc sections and two straight sections. 4 pm –rad vertical emittance was already confirmed by CW laser wire monitor at the ATF damping ring. The main goal of ATF damping ring was production of 10 pm-rad emittance beam stably with multibunch beam of 210 mA. In the damping ring at ATF, vertical beam size is less than 10 μm. For emittance measurement we are developing a ne...
Measurement of an electron beam size with a laser wire beam profile monitor
Physical Review Special Topics - Accelerators and Beams, 2001
We describe the first measurement of an electron beam size in the accelerator test facility damping ring at KEK with a laser wire beam profile monitor. This monitor is based upon the Compton scattering process of electrons with a laser light target, which is produced by injecting a cw laser beam into a Fabry-Pérot optical cavity. We have observed clear signals of the Compton scattered photons and confirmed that the observed energy spectrum as well as the count rate agree with the expected ones. From the measurement, we have deduced the vertical beam size s b to be 9.8 6 1.1 6 0.4 mm, where the first (second) error represents statistical (systematic) uncertainty. Various improvements are in progress to enhance the signal-to-noise ratio, which is essential for the detailed study of the beam dynamics.