Laser wire beam profile monitor in the spallation neutron source (SNS) superconducting linac (original) (raw)
Related papers
Measurement of ion beam profiles in a superconducting linac with a laser wire
Applied Optics, 2010
A laser wire ion beam profile monitor system has been developed at the Spallation Neutron Source accelerator complex. The laser wire system uses a single laser source to measure the horizontal and vertical profiles of a pulsed hydrogen ion (H −) beam along a 230 m long superconducting linac, which accelerates H − from 200 MeV to 1 GeV. In this paper, we describe the laser optics requirement for the system, the performance of the profile measurement, and the effects of laser parameters on the measurement reliability. The result provides a practical guideline for the development of a large-scale, operational, laser-based diagnostics in accelerator facilities.
Laser Based Diagnostics for Measuring H- Beam Parameters
2011
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
2011
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,
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.
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.
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.
The SNS laser profile monitor design and implementation
2003
After a successful demonstration of a non-intercepting beam profile monitor for the Hbeams at the 750 KeV and the 200 MeV LINAC at Brookhaven National Laboratory, the SNS project approved using a Nd:YAG laser rather than the traditional carbon wire for transverse profile monitors in the SNS super-conducting LINAC. Experiments have also been performed on SNS 2.5 MeV medium energy beam transport line at LBNL. The design and the implementation of a multi-station profile monitoring system using a single laser will be presented. The laser beam is scanned across the Hbeam to photoneutralize narrow slices. The liberated electrons are collected to provide a measurement of the transverse beam profile. The prototype system has been tested; the measurement and performance results will be presented.
SPALLATION NEUTRON SOURCE LINAC BEAM POSITION AND PHASE MONITOR SYSTEM
The SNS linac currently has over 60 beam position monitors which allow the measurement of both beam position and phase from a single pickup. The signals from the pickup lobes are down converted from either 402.5 MHz or 805 MHz to 50-MHz IF signals for processing. The IF signals are synchronously sampled at 40 MHz to generate I and Q signals from which the beam position and phase are calculated. Each BPM sampling reference frequency is locked to a phase-stable 2.5 MHz signal distributed along the linac. The system is continuously calibrated by generating and measuring rf bursts in the processor that travel to the BPM pickup, reflect off of the shorted BPM lobes and return to the processor for remeasurement. The electronics are built in a PCI card format and controlled vith LabVIEW. Details of the system design and performance are presented.
A Real-Time Energy Monitor System for the IPNS Linac
Injected beam energy and energy spread are critical parameters affecting the performance of our rapid cycling synchrotron (RCS). A real-time energy monitoring system is being installed to examine the H- beam out of the Intense Pulsed Neutron Source (IPNS) 50 MeV linac. The 200 MHz Alvarez linac serves as the injector for the 450 MeV IPNS RCS. The linac provides an 80 ms macropulse of approximately 3x1012 H- ions 30 times per second for coasting-beam injection into the RCS. The RCS delivers protons to a heavy-metal spallation neutron target for material science studies. Using a number of strip-line beam position monitors (BPMs) distributed along the 50 MeV transport line from the linac to the RCS, fast signals from the strip lines are digitized and transferred to a computer which performs an FFT. Corrections for cable attenuation and oscilloscope bandwidth are made in the frequency domain. Rectangular pulse train phasing (RPTP) is imposed on the spectra prior to obtaining the inverse...