The linear accelerator (LINAC) at the Los Alamos Neu-tron Science Center (LANSCE) consists of Pre-buncher, Main-Buncher, low-energy beam transport (LEBT), four 201.25-MHz Drift Tube Linacs (DTLs) and forty-four 805-MHz Coupled Cavity Linacs (CCLs). As a part of the upcoming LANSCE Modernization project, low-level RF (LLRF) systems of four 201-MHz DTLs and twenty-six 805-MHz SCLs have been digitized. Hence the net-work-based control of the cavity field and RF commis-sioning are possible. Each LLRF and high-power RF (HPRF) systems have many process variables (PVs) lo-cated on different computer control screens provided by the Extensible Display Manager (EDM). Several MATLAB m-scripts have been developed to efficiently process the necessary PVs while auto-start, ampli-tude/phase calibration, gain tuning of the cavity field feedback controllers, gain and phase tuning of the beam feedforward controllers, and high power RF trip recovery, processes are configured and validated. This paper ad-dresses the sequence of RF commissioning of the LANSCE LINAC from the time of RF-turn-on to beam feedforward control and its relevant EDMs and MATLAB m-scripts.
The front end of Los Alamos Neutron Science Center (LANSCE) linear accelerator uses four 201.25-MHz Drift-Tube Linacs (DTLs) to accelerate the H+ and H- beams to 100 MeV. Three of the 201.25-MHz DTLs are powered by diacrodes and the first DTL is powered by a tetrode. A 20-kW solid-state power amplifier (SSPA) is used to provide ~15 kW drive power to the tetrode. The SSPA is water-cooled and consists of 24 push-pull LDMOS transistors operating at 45% of their power saturation capability, providing ample power headroom and excellent linearity. However, the phase of the SSPA is perturbed at +/-20…
Suppression of beam losses is essential for successful operation of high-intensity linac. Historically, the values of the field amplitudes and phases of the side-coupled, 805-MHz LANSCE linac modules are maintained using a well-known delta-t tuning procedure. Transverse matching of the beam with accelerator is performed through adjustments of beam ellipses in 4D phase space with accelerator lattice using matching quadrupoles. Control of the beam-energy ramp along the length of a proton linear accelerator is required to improve tune of accelerator and decrease beam losses. Time-of-flight measur…
The disassembly of the Unilac prestripper linac of the Wideroe type took place at the beginning of 1999. An increase of more than two orders of magnitude in particle number for the most heavy elements in the SIS had to be gained. Since that time the new High Current Injector (HSI) consisting of H-type RFQ and DTL-structures for dual beam operation was installed and successfully commissioned. The High Charge Injector (HLI) supplied the main linac during that time. Simultaneously conditioning and running in of the rf-transmitters and rf-structures were done. The HSI commissioning strategy includ…
The 750-keV low-energy beam transport of the Los Alamos Neutron Science Center (LANSCE) linac consists of two independent beam lines that facilitate simultaneous injection of H+ and H- beams into the linear accelerator. The efficiency of beam transport within this structure is largely controlled by the effects of space-charge neutralization. In this paper, we report a series of experiments that were performed to determine the level, as well as the required timescale for the onset of beam space charge neutralization. Measurements performed along the structure indicate significant variation of n…
The LANSCE Isotope Production Facility (IPF) utilizes a 100-MeV proton beam with average power of 23 kW for isotope production in the fields of medicine, nuclear physics, national security, environmental science and industry. Typical tolerable fractional beam loss in the 100-MeV beamline is 4 x10-3. Experimental beam study was made to minimize the beam losses. Adjustments to the ion source extraction voltage resulted in the removal of tails in phase space. Beam based steering in beamlines led to the reduction of beam emittance growth. Readjustment of the 100-MeV quadrupole transport resulted i…
The new 1.4 MeV/u front end HSI (HochStromInjektor) of the Unilac accelerates ions with A/q ratios of up to 65 and with beam intensities in emA of up to 0.25 A/q. The maximum beam pulse power is up to 1300 kW. During the stepwise linac commissioning from April to Septem-ber 1999 the beam behind of each cavity was analysed within two weeks. A very stable Ar1+ beam out of a vol-ume plasma source MUCIS was used mainly. The meas-ured norm. 80 % emittance areas around 0.45 pi mm mrad are close to the results from beam simulations. Up to 80 % of the design intensity at the linac exit were achieved. …
We report results of the beam commissioning and first operation of the 1.3 GHz superconducting RF electron linear accelerator at Fermilab Accelerator Science and Technology (FAST) facility. Construction of the linac was completed and the machine was commissioned with beam in 2017. The maximum total beam energy of about 300 MeV was achieved with the record energy gain of 250 MeV in the ILC-type SRF cryomodule. The photoinjector was tuned to produce trains of 200 pC bunches with a frequency of 3 MHz at a repetition rate of 1 Hz. This report describes the aspects of machine commissioning such as …
In order to ensure the beam quality and meet the requirements introduced by the BEPCII storage ring, the beam energy feedback system has been developed at the exit of the linac. This paper describes the implementation and commissioning of this system in detail. The energy feedback system consists of an energy measurement unit, an application software and an execution unit. In order to ensure the real-time monitoring and adjustment of beam energy, we need to introduce a non-interceptive type of online beam energy measurement method which is on the first try in China and the effective mechanism …
This work describes first commissioning results from the Cornell Brookhaven Energy Recovery Test Accelerator Fractional Arc Test. These include the recommissioning of the Cornell photo-injector, the first full energy operation of the main linac with beam, as well as commissioning of the lowest energy matching beamline (splitter) and a partial section of the Fixed Field Alternating gradient (FFA) return loop featuring first production Halbach style permanent magnets. Achieving these tasks required characterization of the injection beam, calibration and phasing of the main linac cavities, demons…
The China spallation neutron source (CSNS) linac is designed with beam energy of 81MeV and a peak current of 15mA in the first phase. The RF power system for the 81 MeV Linac requires 8 units of RF power sources, each unit has one independent digital low level RF (LLRF) control system which is used to stabilize the amplitude and phase of the RF accelerating field along the linac, and to minimize beam loss. During beam commissioning, all of 8 on-line units of LLRF control system were operating stably and reliable, the control precision of accelerating fields met requirement of beam commissionin…
A new experimental area designed to develop, test and verify muon ionization cooling apparatus using the 400-MeV Fermilab Linac proton beam has been fully installed and is presently being commissioned. Initially, this area was used for cryogenic tests of liquid-hydrogen absorbers for the MUCOOL R&D program and, now, for high-power beam tests of absorbers, high-gradient rf cavities in the presence of magnetic fields (including gas-filled cavities), and other prototype muon-cooling apparatus. The experimental scenarios being developed for muon facilities involve collection, capture, and cooling …
KEK electron linac was upgraded to 8 GeV for the KEK B-Factory (KEKB) project. During the commissioning of the upgraded linac, even continuing SOR ring injections, we had achieved a primary electron beam with 10-nC (6.24 x 10^10) per bunch up to 3.7-GeV for positron generation. This could be classified as one of the brightest S-band linac's. Since the KEKB rings were completed in December 1998, those 3.5-GeV position and 8-GeV electron beams have been injected with an excellent performance. Moreover, we have succeeded in switching among the high-intensity beams for KEKB and beams for two SOR r…
The China Spallation Neutron Source (CSNS) accelerator uses H- stripping and phase space painting method of filling large ring acceptance with the linac beam of small emittance. The beam commissioning software system is the key part of CSNS accelerator. The injection beam commissioning software for CSNS contains three parts currently: painting curve control, injection beam control and injection orbit correction. The injection beam control contains two subsections: single bunch beam calculation and LRBT beam control at the foil. The injection orbit correction also contains two subsections: inje…
We outline the design of beam experiments for the electron linac at the Fermilab Accelerator Science and Technology (FAST) facility and for the Integrable Optics Test Accelerator (IOTA), based on synchrotron light emitted by the electrons in bend dipoles, detected with gated microchannel-plate photomultipliers (MCP-PMTs). The system can be used both for beam diagnostics (e.g., beam intensity with full dynamic range, turn-by-turn beam vibrations, etc.) and for scientific experiments, such as the direct observation of the time structure of the radiation emitted by single electrons in a storage r…
The first phase of the HIE-ISOLDE project at CERN consists of a superconducting (SC) linac upgrade in order to increase the energy of post-accelerated radioactive ion beams from 2.8 MeV/u to over 10 MeV/u (for A/q = 4.5). In preparation for the upgrade, we present beam dynamics studies of the booster section of the normal conducting (NC) REX-ISOLDE linac, focused on the longitudinal development of the beam in the 101.28 MHz Interdigital H-mode Structure (IHS), employing a Combined Zero Degree Structure (KONUS), pulsing at a high gradient of over 3 MV/m. The evolution of the transverse emittanc…
The KEK 8-GeV electron / 3.5-GeV positron linac has been operated with very different beam specifications for downstream rings, KEKB, PF and PF-AR. For the reliable operation among these beam modes intelligent beam switching and beam feedback systems have been developed and used since its commissioning. A software panel is used to choose one of four beam modes and a switching sequence is executed in about two minutes. Most items in a sequence are simple operations followed by failure recoveries. The magnet standardization part consumes most of the time. The sequence can be re-arranged easily b…
As an important measure of improving the efficiency and usability of X-ray free electron laser facilities, simultaneous operation of multiple undulator lines realized by a beam distribution system has become a standard configuration in the recent built XFEL facilities. In Shanghai, SXFEL-UF, the first soft X-ray free electron laser user facility in China, has finished construction and started commissioning recently. Electron beam from linac is alternately distributed between the two parallel undulator beam lines by a beam distribution system with a 6° deflection line. The beam distribution sys…
In synchrotron machines, the beam extraction is accomplished by a combination of septa and kicker magnets which deflect the beam from an accelerator into another. Ideally the kicker field must rise/fall in between the beam bunches. However, in reality, an intentional beam-free time region (aka "notch") is created on the beam pulse to assure that the beam can be extracted with minimal losses. In the case of the Fermilab Booster, the notch is created in the ring near injection energy by the use of fast kickers which deposit the beam in a shielded collimation region within the accelerator tunnel.…
Longitudinal space charge (LSC) effects are generally considered harmful in free-electron lasers as they can seed unfavorable energy modulations that can result in density modulations with associated emittance dilution. It was pointed out, however, that such "micro-bunching instabilities" could be potentially useful to support the generation of broadband coherent radiation. Therefore there has been an increasing interest in devising accelerator beam lines capable of controlling LSC induced density modulations. In the present paper we augment these previous investigations by combining a grid-le…
Linear accelerators containing the sequence of independently phased cavities with constant geometrical velocity along each structure are widely used in practice. The chain of cavities with identical cell lengths is utilized within a certain beam velocity range, with subsequent transformation to the next chain with higher cavity velocity. Design and analysis of beam dynamics in this type of accelerator are usually performed using numerical simulations. A full theoretical description of particle acceleration in an array of independent phased cavities has not been developed. In the present paper,…
Over the last years, the generation and acceleration of ultra-short, high quality electron beams has attracted more and more interest in accelerator science. Electron bunches with these properties are necessary to operate and test novel diagnostics and advanced high gradient accelerating schemes such as plasma accelerators or dielectric laser accelerators. Furthermore, several medical and industrial applications require high-brightness electron beams. The dedicated R&D facility ARES at DESY will provide such probe beams in the upcoming years. After the setup of the normal-conducting RF photoin…
The Proton Improvement Plan II (PIP-II) at Fermilab is a program of upgrades to the injection complex. At its core is the design and construction of a CW-compatible, pulsed H- superconducting RF linac. To validate the concept of the front-end of such machine, a test accelerator (a.k.a. PXIE) is under construction. It includes a 10 mA DC, 30 KeV H- ion source, a 2 m-long Low Energy Beam Transport (LEBT), a 2.1 MeV CW RFQ, followed by a Medium Energy Beam Transport (MEBT) that feeds the first of 2 cryomodules increasing the beam energy to ~25 MeV, and a High Energy Beam Transport section (HEBT) …
X-rays have widespread applications in science and industry, but developing a simple, compact, and high-quality X-ray source remains a challenge. Our collaboration has explored the possible use of channeling radiation driven by a 50 MeV low-emittance electron beam to produce narrowband hard X-rays with photon energy of 40 to 140 keV. Here we present the simulated X-ray spectra including the background bremsstrahlung contribution, and a description of the required optimization of the relevant electron-beam parameters necessary to maximize brilliance of the resulting X-ray beam. Results are pres…
The Linac to End Station A (LESA) beamline is being constructed at SLAC and will provide a near-CW beam of multi-GeV electrons to the SLAC End Station A for experiments in particle physics. The 1st half of LESA is ready for commissioning at the end of FY22 and the full beamline will be operational Q1 FY24. The low-current multi-GeV electron beam is produced parasitically by the superconducting RF (SRF) linac for the LCLS-II/LCLS-II-HE X-ray Free Electron Laser. LESA is designed to host experiments to detect light dark matter such as the Light Dark Matter eXperiment (LDMX) as well as a wide ran…
Significant transient beam loading effects were observed during beam commissioning tests of prototype II of the injector for the Accelerator Driven Sub-critical (ADS) system, which took place at the Institute of Modern Physics, Chinese Academy of Sciences, between October and December 2014. During these tests experiments were performed with CW operation of the cavities with pulsed beam current, and the system was configured to make use of a prototype digital low level radio frequency (LLRF) controller. The system was originally operated in pulsed mode with a simple PID feedback control algorit…
The Source Development Lab (SDL) at BNL consists of a 230 MeV electron linac and a 10 m long wiggler for short wavelength Free Electronic Laser (FEL) development. The original control system [1] was based on the one in use at the National Synchrotron Light Source. In 2000 the control system was upgraded to be based on EPICS to facilitate software interfaces for extensions at all levels. The FEL began commissioning in May 2001. The upgraded control systems have been stable, reliable and easy to operate. An overview of the control systems, including for the linac, the waveform digitizer controls…
CEA is committed to the design, construction and commissioning of a Medium Energy Beam Transfer line and a superconducting linac (SCL) for SARAF accelerator in order to accelerate 5mA beam of either protons from 1.3 MeV to 35 MeV or deuterons from 2.6 MeV to 40 MeV. The Low Level RF (LLRF) is a subsystem of the CEA control domain for the SARAF-LINAC instrumentation. The top level requirement of the LLRF system has been presented in the last LLRF conference. The paper shows a simulink model to analyse and determinate the LLRF technical specification. The public bidding for SARAF LLRF is in the …
To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energy RHIC electron Cooler (LEReC) is currently under commissioning at BNL. The Linac of LEReC is designed to deliver a 1.6 MeV to 2.6 MeV electron beam, with rms dp/p less than 5e-4. A 704 MHz superconducting radio frequency (SRF) booster cavity in this Linac provides up to 2.2 MeV accelerating voltage. With such a low energy and very demanding energy spread requirement, control of Higher Order Modes (HOMs) in the cavities becomes critical and needs to be carefully evaluated to ensure minimum impact on the b…
Implementation and commissioning of the EPICS based control system for the ISAC radioactive beam facility was completed. The target ion source, mass separator, and low-energy beam-lines started beam production for experiments. In parallel, controls for the accelerator system, a radio-frequency quadrupole followed by a drift-tube linac, and several high-energy beam-lines were implemented and commissioned. The number of controlled devices more than doubled since the last report. An overview of relational database usage, software engineering and quality control methods used will be given.
Operation of Superconducting Radio Frequency (SRF) cavities with high loaded quality factors is becoming increasingly preferred for applications which involve low beam loading including Energy Recovery Linacs (ERL). Vibration induced microphonics detuning poses a major operational bottleneck in these low bandwidth systems, adversely affecting field stability. Besides passive measures of mitigating the vibration sources, modern SRF cavities are also attached to fast tuners incorporating piezo-electric actuators. We demonstrate the narrow band active noise control algorithm for realizing active …
Los Alamos is currently developing novel particle accelerator controls and diagnostics algorithms to enable higher quality beams with lower beam losses than is currently possible. The purpose of this workshop was to consider tuning and optimization challenges of a wide range of particle accelerators including linear proton accelerators such as the Los Alamos Neutron Science Center (LANSCE), rings such as the Advanced Photon Source (APS) synchrotron, free electron lasers (FEL) such as the Linac Coherent Light Source (LCLS) and LCLS-II, the European X-ray Free Electron Laser (EuXFEL), the Swiss …
The SwissFEL Injector Test Facility operated at the Paul Scherrer Institute between 2010 and 2014, serving as a pilot plant and testbed for the development and realization of SwissFEL, the X-ray Free-Electron Laser facility under construction at the same institute. The test facility consisted of a laser-driven rf electron gun followed by an S-band booster linac, a magnetic bunch compression chicane and a diagnostic section including a transverse deflecting rf cavity. It delivered electron bunches of up to 200 pC charge and up to 250 MeV beam energy at a repetition rate of 10 Hz. The measuremen…
The Low Energy RHIC electron Cooler (LEReC) is currently under commissioning at BNL to improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon. The linac of LEReC consists of a DC photoemission gun, one 704 MHz superconducting radio frequency (SRF) booster cavity, and three normal conducting cavities. It is designed to deliver a 1.6 MeV to 2.6 MeV electron beam, with peak-to-peak momentum spread dp/p of less than 7e4. Two of the three normal conducting cavities will be used in LEReC for energy spread correction. A single-cell 704 MHz cavity for energy de-chirping and a three-c…
LCLS-II is currently in its commissioning phase at SLAC. It is an X-ray FEL driven by a CW superconducting LINAC. The beam injector plays a crucial role in the overall performance of the accelerator, and is critical to the final electron beam performance parameters. The LCLS-II injector comprises of a 185.7 MHz VHF copper gun cavity, and a 1.3 GHz two-cell L-band copper buncher cavity. The FPGA-based controller employs feedback and Self-Excited Loop logic in order to regulate the cavity fields. It also features several other functionalities, such as live detune computation, active frequency tr…
