Performance of the Argonne Wakefield Accelerator facility and initial experimental results (original) (raw)
Related papers
The Argonne Wakefield Accelerator-overview and status
Proceedings of International Conference on Particle Accelerators, 1993
The Argonne Wakefield Accelerator (AWA) is a new facility for advanced accelerator research, with a particular emphasis on studies of high gradient (-100 MeV/m) wakefield accekration. A novel high current short pulse L-Band photocathode gun and preaccelerator will provide 100 nC electron bunches at 20 MeV to be used as a drive beam, while a second high brightness gun will be used to generate a 5 MeV witness beam for wakekld measurements. We will present an overview of the various AWA systems, the status of construction, and initial commissioning results.
A new high intensity electron beam for wakefield acceleration studies
A new RF photocathode electron gun and beamline have been built for the study of electron beam driven wakefield acceleration. The one and a half cell L-band gun operates with an electric field on the cathode surface of 80 MV/m, and generates electron bunches with tens of nanocoulombs of charge and rms bunch lengths of a few picoseconds. The beam diagnostics include a Cherenkov radiator and streak-camera for bunch length measurements, YAG screens for beam profile, integrating charge transformers (ICTs) for bunch charge, an energy spectrometer, and a pepper-pot plate for measurement of the transverse emittance. Measurements of the beam properties at various bunch charges are presented.
The Argonne Wakefield Accelerator Facility: Status and Recent Activities
We describe the Argonne Wakefield Accelerator Facility (AWA), pointing out its present capabilities and goals. We present recent measurements on beam loading observed in our photocathode RF gun. Wakefield measurements in dielectric loaded structures are also reported. Our most recent wakefield structure operates at 15 GHz, and has been excited by single electron bunches and also by sets of two closely spaced bunches. When driven by 43 nC bunches, the accelerating gradient in this structure reached 23 MV/m. No signs of electric breakdown have been observed. This report ends with a brief discussion on the next activities to take place at the AWA facility.
The Argonne Wakefield Accelerator: diagnostics and beam characterization
Proceedings of the 1997 Particle Accelerator Conference (Cat. No.97CH36167), 1998
The Argonne Wakefield Accelerator is comprised of two L-band photocathode RF guns and standing wave linac structures. The high charge bunches (20 -100 nC) produced by the main gun (drive gun) allow us to study the generation of wakefields in dielectric lined structures and plasmas. The secondary gun (witness gun) generates low charge bunches (80 -300 pC) that are used to probe the wakefields excited by the drive bunches. We use insertable phosphor screens for beam position monitoring. Beam intensity is measured with Faraday cups and integrating current transformers. Quartz or aerogel Cerenkov radiators are used in conjunction with a Hamamatsu streak-camera for bunch length measurements. The beam emittance is measured with a pepper-pot plate and also by quadrupole scan techniques. We present a description of the various diagnostics and the results of the measurements. These measurements are of particular interest for the high current (drive) linac, which operates in a much higher charge regime than other photoinjector-based linacs. 1996 0-7803-4376-X/98/$10.00
A Meter-Scale Plasma Wakefield Accelerator Driven by a Matched Electron Beam
2004
A high-gradient, meter-scale plasma-wakefield accelerator module operating in the electron blowout regime is demonstrated experimentally. The beam and plasma parameters are chosen such that the matched beam channels through the plasma over more than 12 beam beta functions without spreading or oscillating over a range of densities optimum for observing both deceleration and acceleration. The wakefield decelerates the bulk of the initially 28.5 GeV beam by up to 155 MeV; however, particles in the back of the same beam are accelerated by up to 280 MeV at a density of 1:9 10 14 cm ÿ3 as the wakefield changes sign.
Plasma Wakefield Accelerators Using Multiple Electron Bunches
Particle accelerators are the tools that physicists use today in order to probe the fundamental forces of Nature, by accelerating charged particles such as electrons and protons to high energies and then smashing them together. For the past 70 years the acceleration schemes have been based on the same technology, which is to place the particles onto radio-frequency electric fields inside metallic cavities. However, since the accelerating gradients cannot be increased arbitrarily due to limiting effects such as wall breakdown, in order to reach higher energies today’s accelerators require km-long structures that have become very expensive to built, and therefore novel accelerating techniques are needed to push the energy frontier further. Plasmas do not suffer from those limitations since they are gases that are already broken down into electrons and ions. In addition, the collective behavior of the particles in plasmas allows for generated accelerating electric fields that are orders of magnitude larger than those available in conventional accelerators. Such wakefields have been demonstrated experimentally, typically by feeding either single electron bunches or laser beams into high density plasmas. As such plasma acceleration technologies mature, one of the main future challenges is to monoenergetically accelerate a second trailing bunch by multiplying its energy in an efficient manner, so that it can potentially be used in a future particle collider. The work presented in this dissertation is a fruitful combination of theory, simulations and experiments that analyzes the use of multiple electron bunches in order to enhance certain plasma acceleration schemes. Specifically, the acceleration of a trailing electron bunch in a high-gradient wakefield driven by a preceding bunch is demonstrated experimentally for the first time by using bunches short enough to sample a small phase of the plasma wakes. Additionally, it is found through theoretical analysis and through simulations that by using multiple bunches to drive the wakefields, the energy of a trailing bunch could be efficiently multiplied in a single stage, thus possibly reducing the total length of the accelerator to a more manageable scale. Relevant proof-of-principle experimental results are also presented, along with suggested designs that could be tested in the near future. Furthermore, electron beam and plasma diagnostics are analyzed and presented, which are necessary for properly completing and understanding any plasma wakefield experiment. Finally, certain types of plasma sources that can be used in related experiments are designed, diagnosed and tested in detail.
Meter-scale plasma-wakefield accelerator driven by a matched electron beam
2004
A high-gradient, meter-scale plasma-wakefield accelerator module operating in the electron blowout regime is demonstrated experimentally. The beam and plasma parameters are chosen such that the matched beam channels through the plasma over more than 12 beam beta functions without spreading or oscillating over a range of densities optimum for observing both deceleration and acceleration. The wakefield decelerates the bulk of the initially 28.5 GeV beam by up to 155 MeV; however, particles in the back of the same beam are accelerated by up to 280 MeV at a density of 1:9 10 14 cm ÿ3 as the wakefield changes sign.
Physical Review Special Topics - Accelerators and Beams, 2000
We report on the experimental demonstration of a novel wakefield acceleration technique where a short electron bunch excites a broadband harmonic frequency spectrum, in a cylindrical dielectric structure, to synthesize an accelerating waveform. The structure is designed to have its TM 0n modes nearly equally spaced so that the modes generated by a single short electron bunch constructively interfere in the neighborhood of integral multiples of the fundamental wavelength producing large acceleration gradients. Realization of a harmonic multimode structure requires more stringent design considerations than a single-mode structure, since the permittivity and loss tangent of the material should not change substantially over the bandwidth of the structure. In this experiment, a bunch train of four 5 nC electron bunches, separated by 760 ps (one net wavelength), were passed through a 60 cm long dielectric-lined cylindrical harmonic structure. Use of a train of drive bunches spaced by one wavelength reinforced the accelerating wakefield; observation of the energy loss of each bunch via a magnetic spectrometer served as a diagnostic of the wakefield. The measured energy spectrum of the four beams after passing through the waveguide was found to be in excellent agreement with the predictions of the analytic model. This result demonstrates that a dielectric can be fabricated which can synthesize the required wakefield. We also discuss potential advantages of this harmonic approach over conventional single-mode wakefield accelerators.
First emittance measurement of the beam-driven plasma wakefield accelerated electron beam
2021
Next-generation plasma-based accelerators can push electron beams to GeV energies within centimetre distances. The plasma, excited by a driver pulse, is indeed able to sustain huge electric fields that can efficiently accelerate a trailing witness bunch, which was experimentally demonstrated on multiple occasions. Thus, the main focus of the current research is being shifted towards achieving a high quality of the beam after the plasma acceleration. In this letter we present beam-driven plasma wakefield acceleration experiment, where initially preformed high-quality witness beam was accelerated inside the plasma and characterized. In this experiment the witness beam quality after the acceleration was maintained on high level, with 0.2% final energy spread and 3.8 μ m resulting normalized transverse emittance after the acceleration. In this article, for the first time to our knowledge, the emittance of the PWFA beam was directly measured.
Driver-witness-bunches for plasma-wakefield acceleration at the MAX IV linear accelerator
2017
Beam-driven plasma-wakefield acceleration is an acceleration scheme promising accelerating fields of at least two to three orders of magnitude higher than in conventional radiofrequency accelerating structures. The scheme relies on using a charged particle bunch (driver) to drive a non-linear plasma wake, into which a second bunch (witness) can be injected at an appropriate distance behind the first, yielding a substantial energy gain of the witness bunch particles. This puts very special demands on the machine providing the particle beam. In this article, we use simulations to show that, if driver-witness-bunches can be generated in the photocathode electron gun, the MAX IV Linear Accelerator could be used for plasma-wakefield acceleration. (Less)