- Queen Mary University of London
School of Electronic Engineering and Computer Science
327 MIle End Road
London, E1 4NS
UK - +447590076822
- Please visit my updated personal homepage, http://www.timaras.com . I completed my undergraduate degree in 2003 at t... morePlease visit my updated personal homepage, http://www.timaras.com .
I completed my undergraduate degree in 2003 at the electrical and computer engineering department in the National and Technical University of Athens, Greece, and my Ph.D. degree in 2008 at the electrical engineering department of the University of Southern California in Los Angeles. My doctoral research work focused on using multiple electron bunches as a tool for the development of next-generation particle accelerators based on plasma wakefields. I was involved in experimentally demonstrating for the first time the acceleration of a trailing electron bunch in a high-gradient wakefield driven by a preceding bunch, through using bunches short enough to sample a small phase of the plasma wakes. Additionally, I analyzed schemes that utilize multiple bunches to drive the wakefields, showing that the energy of a trailing bunch can be efficiently multiplied in a single stage, thus possibly reducing the total length of an accelerator to a more manageable scale. I am presently a post-doctoral researcher in the Queen Mary University of London, United Kingdom, working on metamaterial-based electromagnetic cloaks.edit
Transformation-based cylindrical cloaks and concentrators are illuminated with non-monochromatic waves and unusual effects are observed with interesting potential applications. The transient responses of the devices are studied... more
Transformation-based cylindrical cloaks and concentrators are illuminated with non-monochromatic waves and unusual effects are observed with interesting potential applications. The transient responses of the devices are studied numerically with the Finite-Difference Time-Domain method and the results are verified with analytical formulas. We compute the effective bandwidth of several cloaking schemes as well as the effect of losses on the performance of the structures. We also find that narrowband behavior, frequency shift effects, time delays and spatial disturbances of the incoming waves are dominant due to the inherently dispersive nature of the devices. These effects are important and should be taken into account when designing metamaterial-based devices.
A plasma wakefield experiment is presented where two 60-MeV subpicosecond electron bunches are sent into a plasma produced by a capillary discharge. Both bunches are shorter than the plasma wavelength, and the phase of the second bunch... more
A plasma wakefield experiment is presented where two 60-MeV subpicosecond electron bunches are sent into a plasma produced by a capillary discharge. Both bunches are shorter than the plasma wavelength, and the phase of the second bunch relative to the plasma wave is adjusted by tuning the plasma density. It is shown that the second bunch experiences a 150 MeV/m loaded accelerating gradient in the wakefield driven by the first bunch. This is the first experiment to directly demonstrate high-gradient, controlled acceleration of a short-pulse trailing electron bunch in a high-density plasma.
We demonstrate that trains of subpicosecond electron microbunches, with subpicosecond spacing, can be produced by placing a mask in a region of the beam line where the beam transverse size is dominated by the correlated energy spread. We... more
We demonstrate that trains of subpicosecond electron microbunches, with subpicosecond spacing, can be produced by placing a mask in a region of the beam line where the beam transverse size is dominated by the correlated energy spread. We show that the number, length, and spacing of the microbunches can be controlled through the parameters of the beam and the mask. Such microbunch trains can be further compressed and accelerated, and have applications to free electron lasers (FELs) and plasma wakefield accelerators (PWFAs).
Particle-in-cell simulations of a plasma wakefield accelerator in the linear regime are presented, consisting of four electron bunches that are fed into a high-density plasma. It is found that a high transformer ratio can be maintained... more
Particle-in-cell simulations of a plasma wakefield accelerator in the linear regime are presented, consisting of four electron bunches that are fed into a high-density plasma. It is found that a high transformer ratio can be maintained over 40cm of plasma if the charge in each bunch is increased linearly, the bunches are placed 1.5 plasma wavelengths apart and the bunch emmitances are adjusted to compensate for the nonlinear focusing forces. The generated wakefield is sampled by a test witness bunch whose energy gain after the plasma is six times the energy loss of the drive bunches. The possibility of extending these schemes to the blowout regime is also examined and it is found to be complicated without shaping the drive bunches. This work was supported by the US Department of Energy.
We present some preliminary experimental results of a plasma wakefield accelerator technique which utilizes multiple electron bunches in order to drive a plasma wave. The experiments were performed at the Accelerator Test Facility of... more
We present some preliminary experimental results of a plasma wakefield accelerator technique which utilizes multiple electron bunches in order to drive a plasma wave. The experiments were performed at the Accelerator Test Facility of Brookhaven National Laboratory where 5-8 equidistant bunches with a spacing which was varied between 100-200μm were fed into a 6mm-long capillary discharge plasma. By varying the time delay of the bunches with respect to the discharge different plasma densities could be tuned, and the effects of the plasma on the bunches were recorded. Such multiple bunch schemes are of great interest because they can provide increased efficiencies and high transformer ratios for advanced accelerators.
We present experimental results obtained with a method for producing trains of microbunches with time separation and length of less than a picosecond. The method uses a solid mask placed in a region of the beam line where the bunch... more
We present experimental results obtained with a method for producing trains of microbunches with time separation and length of less than a picosecond. The method uses a solid mask placed in a region of the beam line where the bunch transverse size is dominated by its correlated energy spread. The mask spoils the emittance of selected bunch slices. The particles scattered by the solid parts of the mask are lost along the beam line. The modulation in energy of the beam charge therefore also corresponds to a modulation of the beam current in time. The mask and beam parameters can be chosen to design the bunch current profile for particular applications, such as plasma wakefield accelerators (PWFAs) or free electron lasers (FELs).
We demonstrate that trains of subpicosecond electron microbunches, with subpicosecond spacing, can be produced by placing a mask in a large dispersion region of the beam line where the beam transverse size is dominated by the correlated... more
We demonstrate that trains of subpicosecond electron microbunches, with subpicosecond spacing, can be produced by placing a mask in a large dispersion region of the beam line where the beam transverse size is dominated by the correlated energy spread. The particles are selected based on the scattering of their emittance at the mask. The electrons that hit the solid arts of the mask are subsequently lost. The mask spatial pattern is converted into a time pattern in the dispersion-free region of the beam line. The experiment was performed with the Brookhaven National Laboratory Accelerator Test Facility 60 MeV beam. We show that the number, length, and spacing of the microbunches can be controlled through the parameters of the beam and the mask. Trains with one to eight equidistant microbunches are produced. The microbunches spacing is adjusted in the 100 to 300 microns or 300 fs to 1 ps range and comparable microbunch length. The train structure is measured using CTR interferometry, and is stable in time and energy. Such microbunch trains can be further compressed and accelerated, and have applications to free electron lasers (FELs) and plasma wakefield accelerators (PWFAs).
We investigate various plasma wakefield accelerator schemes that rely on multiple electron bunches to drive a large amplitude plasma wave, which are followed by a witness bunch at a phase where it will sample the high acceleration... more
We investigate various plasma wakefield accelerator schemes that rely on multiple electron bunches to drive a large amplitude plasma wave, which are followed by a witness bunch at a phase where it will sample the high acceleration gradient and gain energy. Experimental verifications of various two bunch schemes are available in the literature; here we provide analytical calculations and numerical simulations of the wakefield dependency and the transformer ratio when M drive bunches and one witness bunch are fed into a high density plasma, where M is between 2 and 10. This is a favorable setup since the bunches can be adjusted such that the transformer ratio and the efficiency of the accelerator are enhanced compared to single bunch schemes. The possibility of a five bunch ILC afterburner to accelerate a witness bunch from 100 GeV to 500 GeV is also examined.
We use a wire mesh mask placed in a dispersive region of the Accelerator Test Facility (ATF) at Brookhaven National Laboratory to produce a train of picosecond microbunches. The bunch spacing and charge can be tailored for specific... more
We use a wire mesh mask placed in a dispersive region of the Accelerator Test Facility (ATF) at Brookhaven National Laboratory to produce a train of picosecond microbunches. The bunch spacing and charge can be tailored for specific applications. We plan on using this method to generate a train of drive bunches and a witness bunch for plasma wakefield accelerator experiments.
Two subpicosecond electron bunches, separated in energy by approximately 2 MeV and in time by 0.5-1 ps, are sent through a capillary discharge plasma. The plasma density is varied from ~1e14 cm-3 to ~1e18 cm-3. A 1-D plasma wakefield... more
Two subpicosecond electron bunches, separated in energy by approximately 2 MeV and in time by 0.5-1 ps, are sent through a capillary discharge plasma. The plasma density is varied from ~1e14 cm-3 to ~1e18 cm-3. A 1-D plasma wakefield acceleration (PWFA) model indicates the net wakefield produced by the bunches will depend on their relative charge, temporal separation, and the plasma density. The wakefield of the first bunch will also affect the amount of energy gain or loss of the second bunch. During measurements of the energy spectrum of the bunches, we observed a difference in the amount of loss depending on the plasma density. Indication of gain was also observed.
We employed periodic trains of femtosecond electron bunches for testing several novel concepts of acceleration. A microwave-driven linac sends a 45-MeV electron beam (e-beam) through a magnetic wiggler wherein the e-beam energy is... more
We employed periodic trains of femtosecond electron bunches for testing several novel concepts of acceleration. A microwave-driven linac sends a 45-MeV electron beam (e-beam) through a magnetic wiggler wherein the e-beam energy is modulated via the inverse free electron laser (IFEL) technique by interacting with a 30-GW CO2 laser beam, so creating 3 fs long microbunches separated by a 30 fs laser period. We show several examples of utilizing such a femtosecond bunch train in advanced accelerator and radiation source research. We demonstrated that microbunching improves the performance of the laser acceleration process compared to the previously investigated single-bunch technique. Specifically, microbunches were phased to the electromagnetic wave of the CO2 laser beam inside a matched tapered wiggler where ~80% of electrons gained energy as an ensemble while maintaining a narrow energy spread (i.e., monoenergetic). Another plasma wakefield acceleration (PWFA) experiment explored resonant wakefield excitation in an electric discharge plasma with the plasma frequency matched to that of the CO2 laser. Simulations predict orders-of-magnitude enhancement in the wakefield's amplitude compared with that attained with single bunches. In the Particle Acceleration by Stimulated Emission of Radiation (PASER) experiment, we tested a prediction that an active laser medium can produce particle acceleration by stimulating the emission of radiation. The process benefits from the action of a periodic train of microbunches resonating with the laser transition. Finally, we analyze prospects for using partially coherent x-ray sources based on Thomson backscattering from the electron microbunch train.
The recent results indicate formation and measurement of the micro bunch structures of the different time scales. Double beam structure produced and characterized at 100 fs - 05. ps range using beam splitting during compression in the... more
The recent results indicate formation and measurement of the micro bunch structures of the different time scales. Double beam structure produced and characterized at 100 fs - 05. ps range using beam splitting during compression in the magnetic chicane - "dog leg" arrangement. Arbitrary number of 10-50 fs microbunches are sliced out of 5 ps long beam using wire mesh. CSR interferometer is used for detailed characterization of the beams in the two techniques above. 0.3 fs bunches are produced by IFEL and characterized by spectral measurements of the multiple harmonics. Presentation covers experimental results at Brookhaven Accelerator Test Facility.
In the multibunch plasma wakefield acceleration experiment at the Brookhaven National Lab's Accelerator Test Facility a 45 MeV electron beam is initially modulated through the IFEL interaction with a CO2 laser beam at 10.6 µm into a train... more
In the multibunch plasma wakefield acceleration experiment at the Brookhaven National Lab's Accelerator Test Facility a 45 MeV electron beam is initially modulated through the IFEL interaction with a CO2 laser beam at 10.6 µm into a train of short microbunches, which are spaced at the laser wavelength. It is then fed into a high-density capillary plasma with a density resonant at this spacing (1.0 × 1019 cm-3). The microbunched beam can resonantly excite a plasma wakefield much larger than the wakefield excited from the non-bunched beam. Here we present plasma simulations that confirm the wakefield enhancement and the results of a series of CTR measurements performed of the multibunched electron beam.
The Staged Electron Laser Acceleration — Laser Wakefield (STELLA-LW) experiment is investigating two new methods for laser wakefield acceleration (LWFA) using the TW CO2 laser available at the Brookhaven National Laboratory Accelerator... more
The Staged Electron Laser Acceleration — Laser Wakefield (STELLA-LW) experiment is investigating two new methods for laser wakefield acceleration (LWFA) using the TW CO2 laser available at the Brookhaven National Laboratory Accelerator Test Facility. The first is seeded self-modulated LWFA where an ultrashort electron bunch (seed) precedes the laser pulse to generate a wakefield that the laser pulse subsequently amplifies. The second is pseudo-resonant LWFA where nonlinear pulse steepening of the laser pulse occurs in the plasma allowing the laser pulse to generate significant wakefields. The status of these experiments is reviewed. Evidence of wakefield generation caused by the seed bunches has been obtained as well as preliminary energy gain measurements of a witness bunch following the seeds. Comparison with a 1-D linear model for the wakefield generation appears to agree with the data.
We have demonstrated creating two compressed electron beam bunches from a single 60-MeV bunch. Measurements indicate they have comparable bunch lengths (~100–200 fs) and are separated in energy by ~1.8 MeV with the higher-energy bunch... more
We have demonstrated creating two compressed electron beam bunches from a single 60-MeV bunch. Measurements indicate they have comparable bunch lengths (~100–200 fs) and are separated in energy by ~1.8 MeV with the higher-energy bunch preceding the lower-energy bunch by 0.5–1 ps. A possible explanation for the double-bunch formation process is also presented.
Results of plasma density measurements in ablative and hydrogen-filled discharge capillaries are presented. The method of plasma density measurement is based on Stark broadening of atomic hydrogen spectral lines in the plasma due to... more
Results of plasma density measurements in ablative and hydrogen-filled discharge capillaries are presented. The method of plasma density measurement is based on Stark broadening of atomic hydrogen spectral lines in the plasma due to interaction of the hydrogen atoms with free charges. To ensure the measured plasma density corresponds to the internal portion of the discharge volume, we also examine a possibility to collect the plasma light emission with an optical fiber inserted inside the capillary channel. We studied the time dependence of the plasma density relative to the beginning of the discharge with a temporal resolution of 150 ns. The plasma density was found to vary over a range of 1017 – 1015 cm-3. The dependence of the plasma density upon discharge voltage and hydrogen pressure in the hydrogen-filled capillary was also studied. The possibility of designing a hybrid ablative hydrogen-filled capillary that allows us to simplify the high voltage generator scheme and reach high plasma densities is discussed.
The Accelerator Test Facility at Brookhaven National Laboratory (BNL ATF) offers to its users a unique combination of research tools that include a high-brightness 70-MeV electron beam, a mid-infrared (λ= 10μm) CO2 laser of terawatt... more
The Accelerator Test Facility at Brookhaven National Laboratory (BNL ATF) offers to its users a unique combination of research tools that include a high-brightness 70-MeV electron beam, a mid-infrared (λ= 10μm) CO2 laser of terawatt power, and a capillary discharge as a plasma source. These cutting-edge technologies have enabled us to launch a new R&D program at the forefronts of advanced accelerators and radiation sources. The main subjects that we are researching are innovative methods of producing wakes in a linear regime using plasma resonance with the electron microbunch train periodic to the laser’s wavelength and so called “seeded” laser wakefield acceleration (LWFA) that is driven and probed by a combination of electron and laser beams. We describe the present status of the ATF experimental program, including simulations and preliminary experiments; in addition, we review previous ATF experiments that were the precursors to the present program. They encompass our demonstration of longitudinal- and transverse-field phasing inside the plasma wave, plasma channeling of intense CO2 laser beams, and the generation of e -beam microbunch trains by the inverse FEL technique.
We investigate a plasma wakefield acceleration scheme where a train of electron microbunches feeds into a high density plasma. When the microbunch train enters such a plasma that has a corresponding plasma wavelength equal to the... more
We investigate a plasma wakefield acceleration scheme where a train of electron microbunches feeds into a high density plasma. When the microbunch train enters such a plasma that has a corresponding plasma wavelength equal to the microbunch separation distance, a strong wakefield is expected to be resonantly driven to an amplitude that is at least one order of magnitude higher than that using an unbunched beam. PIC simulations have been performed using the beamline parameters of the Brookhaven National Laboratory Accelerator Test Facility operating in the configuration of the STELLA inverse free electron laser (IFEL) experiment. A 65 MeV electron beam is modulated by a 10.6 μm CO2 laser beam via an IFEL interaction. This produces a train of ~90 microbunches separated by the laser wavelength. In this paper, we present both a simple theoretical treatment and simulation results that demonstrate promising results for the multibunch technique as a plasma-based accelerator.
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... more
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.
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.
In this proposal several ablative and gas-filled capillary plasma sources are reviewed, relevant diagnostics that can be utilized to diagnose the peak plasma density and the density evolution over time are investigated, experimental... more
In this proposal several ablative and gas-filled capillary plasma sources are reviewed, relevant diagnostics that can be utilized to diagnose the peak plasma density and the density evolution over time are investigated, experimental results are presented, and also methods and techniques that can be implemented in order to generate and diagnose high density (~1e19 cm-3) plasmas are proposed for this realm of densities which is at the moment not reliably available using capillaries. The work is aimed towards utilizing such plasma sources in high gradient plasma wakefield accelerators.
When a charged particle propagates parallel to a periodic structure, energy is radiated in the form of an electromagnetic wave. This type of radiation is caused due to the interaction of the charged particle’s field (such as an electron)... more
When a charged particle propagates parallel to a periodic structure, energy is radiated in the form of an electromagnetic wave. This type of radiation is caused due to the interaction of the charged particle’s field (such as an electron) with the periodicity of the structure, and belongs to a wide category of phenomena which arise through the interaction of electrons with a medium. The energy radiates under a specific angle with regard to the line of propagation, an angle which depends on the frequency of the particle. So, different frequencies radiate the energy into different angles. This phenomenon was predicted by Frank in 1942 and was experimentally observed in 1953 by Smith and Purcell.
Here we study theoretically the structure which consists of a dielectric waveguide (slab) of specific width, with a sinusoidal periodicity with regard to one of its surfaces. A line current moves parallel to the direction of periodicity and in short distance from it, which causes waves to arise inside the waveguide. These waves are periodical following the period of the structure.
We solve both the homogenous problem (without the source line) and we find the dispersion relation and the propagation factors of the waveguide, as well as the non homogenous problem where the Green function is derived. We use the Floquet theorem for periodic structures, find solutions to the Helmholtz equation, and then apply boundary conditions of continuity to find the unknown coefficients.
The results are calculated arithmetically using Matlab; we draw the electromagnetic fields and the power Poynting vector everywhere in space. Through Poynting vector we derive conclusions about the angle of radiation with respect to frequency. The computer programs are parameterized with respect to the frequency, the geometrical features of the structure and the speed of the source line. Finally, this technique is not limited to sinusoidal structures but applies in any periodic one.
Here we study theoretically the structure which consists of a dielectric waveguide (slab) of specific width, with a sinusoidal periodicity with regard to one of its surfaces. A line current moves parallel to the direction of periodicity and in short distance from it, which causes waves to arise inside the waveguide. These waves are periodical following the period of the structure.
We solve both the homogenous problem (without the source line) and we find the dispersion relation and the propagation factors of the waveguide, as well as the non homogenous problem where the Green function is derived. We use the Floquet theorem for periodic structures, find solutions to the Helmholtz equation, and then apply boundary conditions of continuity to find the unknown coefficients.
The results are calculated arithmetically using Matlab; we draw the electromagnetic fields and the power Poynting vector everywhere in space. Through Poynting vector we derive conclusions about the angle of radiation with respect to frequency. The computer programs are parameterized with respect to the frequency, the geometrical features of the structure and the speed of the source line. Finally, this technique is not limited to sinusoidal structures but applies in any periodic one.
We present some preliminary experimental results of a plasma wakefield accelerator technique which utilizes multiple electron bunches in order to drive a plasma wave. The experiments were performed at the Accelerator Test Facility of... more
We present some preliminary experimental results of a plasma wakefield accelerator technique which utilizes multiple electron bunches in order to drive a plasma wave. The experiments were performed at the Accelerator Test Facility of Brookhaven National Laboratory where 5-8 equidistant bunches with a spacing which was varied between 100-200μm were fed into a 6mm-long capillary discharge plasma. By varying the time delay of the bunches with respect to the discharge different plasma densities could be tuned, and the effects of the plasma on the bunches were recorded. Such multiple bunch schemes are of great interest because they can provide increased efficiencies and high transformer ratios for advanced accelerators.
This presentation is a literature survey that summarizes the major evidence that support the existence of Dark Matter. I analyze the galaxy rotation curves, the motions of galaxies inside clusters, the baryonic mass density estimated from... more
This presentation is a literature survey that summarizes the major evidence that support the existence of Dark Matter. I analyze the galaxy rotation curves, the motions of galaxies inside clusters, the baryonic mass density estimated from Big Bang Nucleosynthesis, the data accumulated from the cosmic microwave background radiation (WMAP, COBE) and finally the dark matter estimates from gravitationally lensed data such as the bullet cluster. Alongside I present some proof for the existence of Dark Energy, as well as evidence that the universe is flat.
This report is aimed at providing a summary of the field of biofuels: the production of liquid fuels from plants. Biofuels are not aiming at solving the world energy problem, but rather at providing a viable alternative to the... more
This report is aimed at providing a summary of the field of biofuels: the production of liquid fuels from plants. Biofuels are not aiming at solving the world energy problem, but rather at providing a viable alternative to the transportation fuels which are presently derived almost in their entirety from imported oil. Rising oil prices, instabilities in the oil-producing regions of the world and greenhouse gas emissions from fossil fuels provide the motivation behind a field in ferment.
As opposed to other renewable intermittent energy technologies such as photovoltaic cells and wind farms, which require (currently inefficient) electrical storage mechanisms in order to function reliably over long periods of time, plants absorb solar energy and store it chemically inside their biomass. It is estimated by our report that 1TW of average power is stored into available for biofuel production biomass in the United States only (the global power consumption is during the year 2007 at 15TW). Even if a small fraction of that stored energy can be retrieved from the biomass, a significant portion of motor fuel could be replaced.
The first chapter summarizes the present global situation in terms of energy demand, CO2 emissions and oil consumption. Chapter 2 provides a basic background on biofuels and examines their potential from an energy perspective. Chapter 3 provides an overview of the biofuel landscape in the United States, which is currently relying on ethanol fuel derived from corn kernels to provide 3% of its transportation fuels, although this type of ethanol could not be expanded into large scale. Chapter 4 examines the details of producing ethanol from the cellulose molecules that comprise the plant walls, which, if harnessed properly, can have much higher efficiencies and energy outputs than crop-derived ethanol because it can consume non-traditional biomass which is not used directly for other purposes. Chapter 5 describes briefly other biofuel production techniques, such as Biodiesel (popular in Germany), sugarcane-derived ethanol (successful in Brazil), Biobutanol and algae cultivation. Finally, we summarize the report in chapter 6.
The document was prepared as a requirement of the ENE505 class at USC (Energy and the Environment) under prof. Ravindra.
As opposed to other renewable intermittent energy technologies such as photovoltaic cells and wind farms, which require (currently inefficient) electrical storage mechanisms in order to function reliably over long periods of time, plants absorb solar energy and store it chemically inside their biomass. It is estimated by our report that 1TW of average power is stored into available for biofuel production biomass in the United States only (the global power consumption is during the year 2007 at 15TW). Even if a small fraction of that stored energy can be retrieved from the biomass, a significant portion of motor fuel could be replaced.
The first chapter summarizes the present global situation in terms of energy demand, CO2 emissions and oil consumption. Chapter 2 provides a basic background on biofuels and examines their potential from an energy perspective. Chapter 3 provides an overview of the biofuel landscape in the United States, which is currently relying on ethanol fuel derived from corn kernels to provide 3% of its transportation fuels, although this type of ethanol could not be expanded into large scale. Chapter 4 examines the details of producing ethanol from the cellulose molecules that comprise the plant walls, which, if harnessed properly, can have much higher efficiencies and energy outputs than crop-derived ethanol because it can consume non-traditional biomass which is not used directly for other purposes. Chapter 5 describes briefly other biofuel production techniques, such as Biodiesel (popular in Germany), sugarcane-derived ethanol (successful in Brazil), Biobutanol and algae cultivation. Finally, we summarize the report in chapter 6.
The document was prepared as a requirement of the ENE505 class at USC (Energy and the Environment) under prof. Ravindra.
We investigate various plasma wakefield accelerator schemes that rely on multiple electron bunches to drive a large amplitude plasma wave, which are followed by a witness bunch at a phase where it will sample the high acceleration... more
We investigate various plasma wakefield accelerator schemes that rely on multiple electron bunches to drive a large amplitude plasma wave, which are followed by a witness bunch at a phase where it will sample the high acceleration gradient and gain energy. Experimental verifications of various two bunch schemes are available in the literature; here we provide analytical calculations and numerical simulations of the wakefield dependency and the transformer ratio when M drive bunches and one witness bunch are fed into a high density plasma, where M is between 2 and 10. This is a favorable setup since the bunches can be adjusted such that the transformer ratio and the efficiency of the accelerator are enhanced compared to single bunch schemes. The possibility of a five bunch ILC afterburner to accelerate a witness bunch from 100 GeV to 500 GeV is also examined.
In the multibunch plasma wakefield acceleration experiment at the Brookhaven National Lab's Accelerator Test Facility a 45 MeV electron beam is initially modulated through the IFEL interaction with a CO2 laser beam at 10.6 µm into a train... more
In the multibunch plasma wakefield acceleration experiment at the Brookhaven National Lab's Accelerator Test Facility a 45 MeV electron beam is initially modulated through the IFEL interaction with a CO2 laser beam at 10.6 µm into a train of short microbunches, which are spaced at the laser wavelength. It is then fed into a high-density capillary plasma with a density resonant at this spacing (1.0 × 1019 cm-3). The microbunched beam can resonantly excite a plasma wakefield much larger than the wakefield excited from the non-bunched beam. Here we present plasma simulations that confirm the wakefield enhancement and the results of a series of CTR measurements performed of the multibunched electron beam.
We investigate a plasma wakefield acceleration scheme where a train of electron microbunches feeds into a high density plasma. When the microbunch train enters such a plasma that has a corresponding plasma wavelength equal to the... more
We investigate a plasma wakefield acceleration scheme where a train of electron microbunches feeds into a high density plasma. When the microbunch train enters such a plasma that has a corresponding plasma wavelength equal to the microbunch separation distance, a strong wakefield is expected to be resonantly driven to an amplitude that is at least one order of magnitude higher than that using an unbunched beam. PIC simulations have been performed using the beamline parameters of the Brookhaven National Laboratory Accelerator Test Facility operating in the configuration of the STELLA inverse free electron laser (IFEL) experiment. A 65 MeV electron beam is modulated by a 10.6 μm CO2 laser beam via an IFEL interaction. This produces a train of ~90 microbunches separated by the laser wavelength. In this paper, we present both a simple theoretical treatment and simulation results that demonstrate promising results for the multibunch technique as a plasma-based accelerator.