Talk will cover state-of-the-art photocathodes for bright-beam and spin-polarized-beam generation.

New materials beyond the standard bulk niobium have the potential to greatly improve the performance of Superconducting Radio Frequency (SRF) cavities. Specifically, thin coatings of normal conductors such as gold have the potential to improve the key RF performance metric of quality factor. We present progress on depositing thin gold layers onto 2.6 GHz SRF cavities and testing their RF performance.

The Cornell High Pulsed Power Sample Host Cavity (CHPPSHC) is a new system designed to measure the superheating field of candidate superconducting RF (SRF) materials, giving insight into their operational limits. This system is designed to reach peak magnetic fields of up to 0.5 T in only a few microseconds, allowing us to achieve a pure magnetic field quench on the sample. We present an overview of the CHPPSHC system and proof of principle data from a niobium sample.

The proposed novel 100 MeV injector for the LANSCE Accelerator Facility* is designed to replace the existing 750-keV Cockcroft-Walton-columns-based injector. The new Front End includes two independent low-energy transports for H+ and H- beams merging at the entrance of a single RFQ, with the subsequent acceleration of particles in the new Drift Tube Linac. The challenge of the design is associated with the necessity of simultaneous acceleration of protons and H- ions with different beam currents, beam charges per bunch, beam emittances, and space charge depression, in a single RFQ and DTL, while injection beam energy is reduced from 750 keV to 100 keV. Acceleration of various beams in a single RFQ provides less flexibility for optimal adjustment of acceleration and focusing parameters concerning the existing LANSCE setup. The paper discusses details of self-consistent multi-beam dynamics in the proposed injector.

The installation and alignment of new beamlines and beamline components is necessary at any accelerator facility. The equipment and methods used to perform these precision driven tasks must be accurate, reliable and above all, easily repeatable. Using coordinate measuring machines (CMM), laser trackers, combined with Spatial Analyzer, Autodesk Inventor and other custom tools, it is possible to rapidly and accurately take an idea from model to reality, as shown through the construction of the ATLAS Multi-User beamline.

The Cornell High Pulsed Power Sample Host Cavity (CHPPSHC) is a new system designed to measure the superheating field of candidate superconducting RF (SRF) materials, giving insight into their operational limits. This system is designed to reach peak magnetic fields of up to 0.5 T in only a few microseconds, allowing us to achieve a pure magnetic field quench on the sample. We present an overview of the CHPPSHC system and proof of principle data from a niobium sample.

High intensity linacs based on compact accelerating RF structures suffer from beam loading effects, which result into a bunch-to-bunch energy loss as a consequence of the beam-induced excitation of the fundamental accelerating mode. To track charged particles under this effect, the code RF-Track implemented a beam loading module in version 2.2.2. For ultrarelativistic scenarios in travelling-wave structures, the simulation tool was limited to trains of bunches with equal charge per bunch. In this work, we present the latest update of the beam loading module in version 2.3.0, extending its capabilities to account for this effect in trains with different charges per bunch and allowing the performance of beam loading compensation studies in these scenarios.

In this paper, we derive the multipolar form of the change in transverse and longitudinal momenta of an ultra-relativistic charged particle that traverses a harmonic TM$_{mn0}$ mode in a pillbox cavity with a beam pipe. The relevant equations are first formalised before presenting results from the numerical integration of RF cavity field maps. In particular, we show that the radial dependence of the change in transverse and longitudinal momenta through a TM$_{mn0}$ mode has polynomial, and not Bessel, dependence.

Fermilab recently completed production and testing of 1.3 GHz cryomodules for the LCLS-II project. Each cryomodule consists of eight TESLA-shaped superconducting elliptical cavities equipped with two High Order Mode (HOM) coupler ports. Measurement of the HOM spectrum is part of the incoming quality control of cavities at room temperature and the final qualification cold test of cryomodules at the Cryomodule Test Facility (CMTF). In this paper we describe the procedure for measuring the HOM spectrum along with further data processing. Finally, we present accumulated statistics of individual HOM frequencies and quality factors related to various cavity vendors and discuss the possible contribution of HOMs to heat loads and beam dynamics.

To minimize the contamination of SRF cavities, remote installation techniques are needed during the installation of components. Recent work at Fermilab has been performed to begin the process of developing techniques for assembling cavities using robotics. Multiple alignment methods were prototyped including alignment and computer vision methods. Using a remotely controlled robotic arm, the alignment and installation of couplers have been successfully performed on prototype PIP-II SSR2 cavities in a cleanroom. The installation process will be shown to show to demonstrate the potential of future installations on other cavities and cavity ancillaries.

The PIP-II linac will include thirty-five 325 MHz Single Spoke Resonators Type 2 (SSR2) cavities. Each cavity will be equipped with a tuner for resonance control. The tuner consists of mechanical frame with a motor for coarse frequency tuning and a piezoelectric actuator for fine frequency tuning. The tuner was tested for the first time at Fermilab on an SSR2 cavity. This dressed cavity-tuner system was tested at the single spoke testing cryo-stat (STC) in Fermilab at 2 K. The tuner performance was evaluated and is presented. Lastly, cavity-tuner mechanical modes were measured via the piezos.

The implementation of High Pressure Rinse (HPR) not only ensures thorough cleaning of the inner high purity niobium surface of Superconducting Radio Frequency (SRF) cavities but also unlocks their full potential for achieving peak performance. By effectively removing contaminants and impurities, HPR sets the stage for enhanced superconducting properties, improved energy efficiency, and superior operational stability. A simulation tool has been developed, facilitating the accurate prediction of both the quality and effectiveness of the rinsing process before its execution in the cleanroom. This tool, the focus of this paper, stands as a pivotal advancement in optimizing Superconducting Radio Frequency (SRF) cavity preparation. Furthermore, our paper will also present correlations with cavity cold testing results, demonstrating the practical applicability and reliability of the simulation predictions in real-world scenarios.

Charged particle dynamics under the influence of electromagnetic fields is a challenging spatiotemporal problem. Current physics-based simulators for beam diagnostics are computationally expensive, limiting their utility for solving inverse problems in real time. The problem of estimating upstream six-dimensional phase space given downstream measurements of charged particles is an inverse problem of growing interest. In this work, we propose a latent evolution model to invert the forward spatiotemporal beam dynamics. In this two-step unsupervised deep learning framework, we first use a variational autoencoder (VAE) to transform 6D phase space projections of a charged particle beam into a lower-dimensional latent distribution. We then autoregressively learn the inverse temporal dynamics in the latent space using a long-short-term memory (LSTM) network. The coupled VAE-LSTM framework can predict 6D phase space projections in upstream accelerating sections given downstream phase space projections as inputs.

From being the first computer-controlled accelerator, through its 52-year long operational history, today the LANSCE Instrumentation and Control System (LICS) shows little resemblance of its early days. Over the past 5 decades, generations of control system engineers were faced with the challenge of maintaining the LICS. However, its maintainability depends on the ability that a failed component or system can be restored or repaired. Complicating this task is the undeniable fact that technology has significantly evolved over the last decades and that older component and systems, while still performing their function, have become obsolete and unmaintainable. When a technology migration path isn't viable to ensure LICS maintainability, the only alternative and opportunity is to upgrade to a new technology platform. Consideration needs to be given that the new technology platform needs to seamlessly integrate with the existing LICS infrastructure while allowing for technological progress. Given LICS’s technology complexity multiple dependencies make the migration and upgrade paths a challenging one. In this paper, we discuss technology choices and compromises made, technology migration and upgrade challenges still faced, and LICS vision for the future. All this under the budgetary and schedule constraints of an operating accelerator facility with an enduring mission.

RadiaSoft and RadiaBeam are partnering on the development of a low level RF control system to support a 100MeV C-Band LINAC. Our system utilizes a Keysight data acquisition system and arbitrary waveform generator to drive the LINAC. The controllers are fully integrated with EPICS and are actively being commissioned. In this presentation we will provide an overview of the design architecture, discuss details of the epics integration, and show initial results controlling a photoinjector.

RadiaBeam and RadiaSoft have been developing a LLRF system for a 100MeV C-band LINAC. The system is based on a Keysight PXIE arbitrary waveform generator and ADCs. We are in the process of commissioning our system and validating its performance. In this presentation, we will provide details on amplitude and phase calibration, improvements to signal conditioning, comparisons between measurements and simulations, and performance of our pulse to pulse feedback scheme.

The advent of c-band and x-band technology has made it possible to reduce the footprint of linear accelerators. Additionally, for industrial systems a more compact linac is enabling technology for burgeoning applications in security and defense. A key aspect to operating these machines in an industrial environments is stabilization of the amplitude and phase signals for the cavities. In this poster we present the design and recent results for a LLRF and pulse-to-pulse correction scheme utilizing an RFSoC based FPGA system.

Conventional beam diagnostics only measure 2D projections of the phase space in x-x', y-y' and z-z'. To estimate a 6D beam phase space distribution for simulations, these 2D projections are multiplied without any correlations between them. It is true only if their degrees of freedom are independent. Recent studies show that there exists correlation across conjugate pairs. This correlation can affect beam dynamics and cause beam loss. In our study, we sought to measure 4D beam phase space distribution with possible correlations across conjugate pairs. For this purpose, we used a direct method of measuring the 4D phase space distribution using slits. A set of 4 slits is used to slice the beam into a specific volume of the 4D phase space, and the charge inside each volume is measured. KOMAC has a test bench called BTS (Beam Test Stand) which consists of a microwave ion source, LEBT, a 200 MHz RFQ and two beamlines. At one of the beamlines, we have just installed slit emittance meter system to measure 4D beam phase space distribution. This paper presents design and fabrication of a slit emittance meter system and shows preliminary experimental results thereof.

Efficient control of frequency detuning for the radio-frequency quadrupole (RFQ) at the Facility for Rare Isotope Beams (FRIB) is still challenging. The transport delay and the complicated heat transfer process in the cooling water control system convolute the control problem. In this work, a long-short term memory (LSTM)-based Koopman model is proposed to deal with this time-delayed control problem. By learning the time-delayed correlations hidden in the historical data, this model can predict the behavior of RFQ frequency detuning with given control actions. With this model, a model predictive control (MPC) strategy is developed to pursue better control performance.

Significant progress towards the suitability of Additive Manufacturing (AM) metal parts for the production of linear accelerator components has been made in recent years. One significant factor for the suitability of AM parts to produce linac rf structures is the surface quality of the parts. Due to the inherently higher surface roughness of AM metal parts, post-processing is necessary to reach surfaces suitable for rf operation. We present most recent results of surface post-processing trials with AM parts from stainless steel.

The International Fusion Materials Irradiation Facility – DEMO-Oriented Neutron Early Source (IFMIF-DONES) will provide a deuteron beam of unprecedented intensity for irradiation and characterization of materials to be used in fusion reactors. In recent years, the possibility to use a small fraction of this beam for other applications in parasitic mode was discussed. This not only has the potential to enlarge the user community without perturbing the main operation, but also allows characterization measurements for beam quality management purposes. Considering various requirements and constraints, the most promising option for the extraction towards such a parasitic line involves the use of a meander-line travelling-pulse beam deflector at the start of the High Energy Beam Transfer (HEBT) line. This paper describes preliminary studies aiming at a first definition of the structure, materials and geometrical parameters of the meander-line deflector.

The Japan Atomic Energy Agency (JAEA) is designing a 30-MW CW proton linear accelerator (linac) for nuclear waste transmutation. Space-charge is the primary challenge in achieving low losses and high beam quality for high-power accelerators, especially at low energy levels where space-charge forces are greater. To counteract the space-charge effects, the low-energy beam transport (LEBT) uses a magnetostatic design to enable the neutralization of the beam charge, the so-called space charge compensation. The neutralization is an accumulation process that reaches a charge balance between the main beam and the opposite ionized particles. However, this equilibrium is destroyed by the chopper system used during beam ramping. During those transient regimes, the beam optics conditions are not optimal for the beam, producing considerable degradation that can end in serious damage to the accelerator. Thus, analysis of beam behavior at these periods is essential to develop a robust design and an efficient operation of the JAEA-ADS linac. This study presents the beam dynamics of neutralization build-up and chopper operation for the JAEA-ADS LEBT.

The 60 kW CW AR RF HPA is critical major equipment in new RF system for ALS-U project at LBNL and so it has been designed & built with a modular redundant topology having large array of 96 RF final PA modules (each delivering ~ 700 W RF output) that are combined in parallel, and large 30 DC PS modules (each ~ 5 kW DC power) operating in parallel for achieving very high reliability (MTBF ~ 135,000 hours) & availability (~ 99.997 %) of RF HPA which is essential for continuous 24/7 beam operations. The redundancy design to modules failures is such that in the event upto 10% failures of RF PA modules and simultaneously upto 15 % failures of DC PS modules the HPA still can generate minimum 48 kW CW RF output that is needed for full beam power and so RF power headroom of 12 kW is built in. The operating power levels & temperatures of all components in HPA are well below to their maximum ratings for high reliability. The MBTF values of subsystems in HPA has been estimated based on components with high failures rates. The reliability probabilities having exponential distribution parameterized on failure rate were determined and the binomial distribution used for modules having redundancy. This paper presents such redundancy design analysis of HPA to such modules failures to achieve such minimum output power. Also the Availability (~99.997%) and the Reliability (MTBF ~ 135,000 hours) Estimation analysis of the overall HPA with such redundancy to modules failures is presented.

Present status and future prospects of the iBNCT accelerator will be discussed. Several accelerator-based neutron sources for Boron Neutron Capture Therapy (BNCT) have been developed in the world. The iBNCT (Ibaraki, BNCT) is a linac-based BNCT facility which is operated by University of Tsukuba and KEK in close collaboration with the local government, Ibaraki prefecture. The accelerator is based on the design and experiences of the J-PARC linac, and consists of an ion source, 3-MeV RFQ, 8-MeV DTL and a Beryllium target with modulators. The project aims to realize a compact and low activation BNCT accelerator of several mA proton beam with high duty factor to obtain the thermal neutron flux required for BNCT, but with high stability as a medical accelerator. Originally the cavities were designed with the minimum amount of cooling water, and their resonance frequencies were maintained by dynamical control of the water temperature according to the RF power input. However, after the interlock due to RFQ discharge, the resonance frequency was shifted frequently. By improving and enhancing the cooling water and vacuum, stable operation at an average current of 2 mA has been achieved. We are performing the pre-clinical testing in FY2022, and prepare to start clinical trials in FY2023. This reports the present status of the iBNCT accelerator and its future prospects.

Linear accelerators for FELs have very high requirements for the accuracy of synchronization. The long and short term stability is influenced by various sources of interference. In this paper it will be shown which methods of stabilization exist and how synchronization accuracies up to the fs-level can be achieved.

Machine learning (ML) tools have been growing in popularity for accelerator applications, but still struggle with time varying systems, for which they require lengthy brute-force re-training. LANL has developed generative machine learning (ML)-based tools, that utilize adaptive model independent feedback control theory together with hard physics constraints, to make the tools much more robust to distribution shift. These adaptive ML tools are able to extrapolate much further beyond the span of the training data and are thus much more robust for time-varying systems. This talk will give a broad overview of the challenges of various time-varying accelerator systems at various accelerator facilities (known as systems with distribution shift in the ML community) and will present adaptive ML tools for 6D phase space diagnostics of intense charged particle beams. The talk will give a general overview of diffusion-based generative models and also adaptive latent space tuning, which is the novel method we have developed for adaptive ML, and how we are strictly enforcing hard physics constraints in our ML tools, which traditional ML tools lack. We demonstrate our general methods for various accelerators: the 5-meter long ultra-fast electron diffraction (UED) HiRES compact accelerator at LBNL, the ~kilometer long plasma wakefield accelerator FACET-II at SLAC, and the LANL ion accelerator LANSCE.

The Compact X-ray Light Source (CXLS) is a compact source of femtosecond pulses of x-rays that is now commissioning in the hard x-ray energy range 6-20 keV. It collides the electron beam from recently developed X-band distributed-coupling, room-temperature, standing-wave linacs and photoinjectors operating at 1 kHz repetition rates and 9300 MHz RF frequency with a Yb:YAG 1030 nm laser beam operating at high peak and average power at 1 kHz repetition rate with pulse energy up to 200 mJ. We present the performance of the CXLS accelerator, laser, and timing systems, and initial x-ray results.

Facility for Rare Isotope Beams (FRIB) requires diverse primary ion species beams to produce rare isotopes. The beam tuning time can be reduced by employing Machine Learning (ML) techniques. In this presentation, we aim to explore practical perspectives on shortening beam tuning time. Specifically, we discuss customization of Bayesian Optimization for maximum beam time utilization, and virtual diagnostics that are currently under development.

The FRIB diagnostics system covers an extensive range of primary and secondary beam intensities of 14 orders of magnitude and requires continuous improvements. The linac diagnostic system has provided straightforward linac commissioning and supports the development of many primary heavy ion beam species for producing rare isotopes. The diagnostics system for the secondary beam has a unique feature of detecting and measuring low-intensity rare isotope beams. This talk will report on the performance of the FRIB diagnostics system and ongoing improvements.

We will present the results of the commissioning program to establish x-ray lasing and operation of the LCLS-II facility, based on the 4 GeV superconducting accelerator. The commissioning scope included the cryogenic systems, SRF and cryomodules, beam transport and two undulator beamlines serving the hard and soft x-ray programs. The talk will include a discussion of achieved beam performance, both for electron and photon beam and our plans to ramp up to the final objectives. A report of operational issues will be included as well. Finally a brief summary of the status of LCLS-II-HE will be provided.

Several measures were developed and deployed at the pulsed linacs FLASH and European XFEL operated at DESY in order to reduce the energy consumption of the RF systems. A staged implementation of several techniques allowed energy savings up to 25% for both facilities, at the cost of reducing the RF overhead and increasing the complexity of the low-level radio frequency (LLRF) system. However, through tool development and automation, the energy saving linac configuration could be implemented without compromising the RF stability, maximum beam energy, accelerator availability and with minimal impact on the setup time.

The assembly of cavity string in the clean room is a tedious work that has noisy and painful steps such as cleaning the taped holes of a part. CEA together with the company INGELIANCE has developed a cobot: a collaborative robot operated by an technician one time and repeating the action without the operator. The cobot can work anytime without any operators: therefore it is working at night reducing the assembly duration by some hours. The cobot consists of a FANUC CRX10 a 6-axis arm on an Arvis cart. At CEA, the cobot is used to blow the flange holes of the cavities and bellows. This allows to reduce the noisy steps that the technicians are exposed to. The process is also more reproducible since the cobot does always the same steps. The cobot is used on ESS cavity string to clean the coupler and cavity flanges. Our activities, results and technical choices for next development will be presented in this poster.

Recent studies have identified intra-beam scattering (IBS) as one of the processes that can have a significant impact on the beam dynamics of linacs with high-density and low-energy beams, such as in free electron sources (FELs), where IBS appears to be one of the effects that most limits their performance. Most existing simulation codes have been developed for circular lattices or assume Gaussian beams and thus cannot accurately simulate the desired scenario. Motivated by this problem, this work presents the implementation of IBS in RF-Track, a tracking code developed for linear accelerators. The numerical simulation follows a novel methodology based on a hybrid-kinetic Monte Carlo approach. The method has proven to be stable using different input parameters and has shown emittance and a Sliced-Energy-Spread (SES) growth in different scenarios, demonstrating the accuracy of the tool and making it a promising solution to understand SES growth in FELs.

The CERN Linear Accelerator for Research (CLEAR) at CERN is a user facility providing a 200 MeV electron beam for accelerator R&D and irradiation studies, including medical applications. In this paper we will outline the most recent improvements in CLEAR operation and beam control and delivery, and describe the upgrades under way, giving an update of their current status. These upgrades include a new front-end for the laser system which will enable an highly flexible time structure, better stability and higher repetition rates, and the implementation of a second beam line which will provide additional testing capability and whose optics has been designed to match user requirements. Finally, we will discuss the proposed future experimental programme of the facility, particularly in view of the novel capabilities provided by the upgrades.

A programmable signal processor-based credited safety control that calculates pulsed beam power based on beam kinetic energy and charge was designed as part of the Proton Power Upgrade (PPU) project at the Spallation Neutron Source (SNS). The system must reliably shut off the beam if the average power exceeds 2.145 MW averaging over 60 seconds. System calibration requires pedigree in measurements, calibration setup, and calculations. This paper discusses the calibration of the analog beam signal components up to and including the Analog Digital Convertors (ADCs) for implementation into the Safety Programmable Logic Controllers (PLCs) and Field Programmable Gate Arrays (FPGAs).

RF long-term stability (drift) is as important as RF short-term stability for the stable operation of particle accelerators including PAL-XFEL. Increasing the performance of LLRF itself becomes an important factor in maintaining the long and short-term stability of the RF field. The reference tracking method applied to LLRF is effectively used as a method of reducing the drift of the RF phase. However, this drift improvement method was not applied to the RF amplitude. This time, the method of reference tracking was newly expanded to improve the RF amplitude drift. As a result of applying this new function to PAL-XFEL LLRF, it is showing some effect in improving the RF amplitude drift. We would like to share the progress so far.

The RIKEN Linear Accelerator (RILAC), one of the injectors at RIBF was upgraded by installing a superconducting RILAC (SRILAC) to search for superheavy elements with element number 119 and above. Before the SRILAC upgrade, the machine protection system in the RILAC was constructed using simple relay circuits. On the other hand, most of the accelerators at RIBF other than RILAC have been equipped with machine protection systems using Mitsubishi MELSEC-Q Programmable Logic Controllers (PLCs) since 2006. They have a mechanism that triggers an anomaly signal to drive the beam chopper to stop the beam and are called beam interlock systems (BIS). Machine protection was needed in the SRILAC project to prevent vacuum deterioration of the superconducting cavity due to changes in the beam orbit. We have developed an FA-M3 PLC-based system to realize a BIS with high response performance at a lower cost than conventional systems. This system is characterized by implementing relatively slow response and I/O requiring high response performance. For example, in the case triggered by an anomaly signal of the electromagnet power supply, simulation of the beam orbit shows that the response performance is relatively slow, a few milliseconds being sufficient. In this conference, the performance results of the constructed BIS will be reported based on the types of anomaly signals in actual SRILAC operation.

BPMs have been used for decades since their easy-to-use absolute transverse position capability. Left signal minus right signal divided by the sum times the radius gives the beam position. The charge is “just” a relative measurement and has to be calibrated (or ironed) against a toroid signal. Even when the incoming charge variation is high (like 3% rms for the superconducting LCLS2), the relative variations are only 0.1%. This opens up quite some uses. Besides even small charge losses at beam restrictions like collimators or septum magnets it has been found that this signal is very useful in quantifying the charge loss during a wire scan since losses of around 2% are observed. By taking the difference of a few BPMs before and after the wire scanners signal-to-noise levels of up to 5000 are observed, making this method compatible to the typical scintillator plus photomultiplier setup. This is especially helpful where the first beam loss is hundreds of meters downstream since most of the scattered electron make it down the relatively wide bore of the superconducting cavities. An SVD method to analyze the data independent by human judgement is discussed.

A compact, high-voltage (HV) pulser in the nanosecond regime for transverse electromagnetic (TEM) kickers is presented. TEM kickers are electromagnetic deflectors used in particle accelerators to redirect bunches of particles out of their original trajectory into a new path, such as alternate beam paths, detectors, or other instrumentation devices. The circuit proposed in this design consists of two main portions: a gate driver and a HV switch. The gate driver consists of an isolated and high-speed gate driver, powered by an isolated DC/DC converter with dual output voltages. The HV switch portion was simulated in Ansys HFSS and is composed of a SiC MOSFET, LC resonance components, and specialized diodes. When switched, the MOSFET is used to pump a high voltage into the LC circuit and diode stack, and the ultrafast diode turnoff delivers the final HV pulse to the resistor load. Careful layout techniques were implemented for the MOSFET driver to reduce pulse to pulse instability. A 1 MHz repetition rate was the target of our design.

The bipolar pulsed electropolishing (BPEP), due to its HF-free feature, can offer much safer, more environmentally friendly, and lower-cost operation compared to the conventional electropolishing, using concentrated HF and H2SO4 as electrolyte. Jefferson Lab has developed the BPEP system using diluted H2SO4 only for implementing final surface processing of niobium SRF cavities, including single cells, 7-cell CEBAF C100 cavity, and 9-cell TESLA-style cavities. The BPEP-treated cavity, followed by 120°C baking, has achieved an accelerating gradient (Eacc) of 37 MV/m with a quality factor (Q0) above 1e10 at 2K, which demonstrated the success of the system's development. The detailed BPEP parameter optimization and study of the surface engineering by BPEP will also be presented.

Superconducting RadioFrequency (SRF) technology is a key component in many particle accelerators operating in a continuous wave, or high duty cycle, mode. The on-line performance of SRF cavities can be negatively impacted by the gradual reduction in the accelerating gradient that can be attained within a reasonable field emission level. Conventional cleaning procedures are both time- and resource-exhaustive as they are done *ex-situ*. As such, *in-situ* techniques are quite attractive. Plasma processing is an emerging *in-situ* method of cleaning which utilizes a mixture of oxygen and an inert gas to chemically remove hydrocarbon-based field emitters through plasma. At TRIUMF's Advanced Rare IsotopE Laboratory (ARIEL), an R&D program is in place to develop plasma processing procedures using fundamental power couplers on 1.3 GHz ARIEL 9-cell cavities. Single cell and multi-cell processing has been performed off-line. The studies involve varying the input parameters and testing the effectiveness of the treatment through RGA analysis. The progress on the developments will be reported.

Since its completion in 2017, Linac4, the new 160 MeV proton injector for the CERN accelerator complex, has undergone some tests to assess and improve reliability, until being connected to the Proton Synchrotron Booster (PSB) during the 2018-2020 Long Shutdown 2 (LS2). The performance requirements for the LHC high-luminosity upgrade have been successfully met, and during its first three complete years of operation the linac has shown high reliability figures. Recent improvements of the H- ion source enable the increase of the beam current from the nominal 35 mA to 50 mA, opening the possibility for increasing the intensity of the Booster beams, for the benefit of the experimental programmes. This paper presents the operational experience and reliability of Linac4 in its first three years of operation.