1,616 research outputs found
Quasi-monoenergetic femtosecond photon sources from Thomson Scattering using laser plasma accelerators and plasma channels
Narrow bandwidth, high energy photon sources can be generated by Thomson
scattering of laser light from energetic electrons, and detailed control of the
interaction is needed to produce high quality sources. We present analytic
calculations of the energy-angular spectra and photon yield that parametrize
the influences of the electron and laser beam parameters to allow source
design. These calculations, combined with numerical simulations, are applied to
evaluate sources using conventional scattering in vacuum and methods for
improving the source via laser waveguides or plasma channels. We show that the
photon flux can be greatly increased by using a plasma channel to guide the
laser during the interaction. Conversely, we show that to produce a given
number of photons, the required laser energy can be reduced by an order of
magnitude through the use of a plasma channel. In addition, we show that a
plasma can be used as a compact beam dump, in which the electron beam is
decelerated in a short distance, thereby greatly reducing radiation shielding.
Realistic experimental errors such as transverse jitter are quantitatively
shown to be tolerable. Examples of designs for sources capable of performing
nuclear resonance fluorescence and photofission are provided
Effects of Hyperbolic Rotation in Minkowski Space on the Modeling of Plasma Accelerators in a Lorentz Boosted Frame
Laser driven plasma accelerators promise much shorter particle accelerators
but their development requires detailed simulations that challenge or exceed
current capabilities. We report the first direct simulations of stages up to 1
TeV from simulations using a Lorentz boosted calculation frame resulting in a
million times speedup, thanks to a frame boost as high as gamma=1300. Effects
of the hyperbolic rotation in Minkowski space resulting from the frame boost on
the laser propagation in the plasma is shown to be key in the mitigation of a
numerical instability that was limiting previous attempts
Computational accelerator science needs towards laser-plasma accelerators for future colliders
Laser plasma accelerators have the potential to reduce the size of future
linacs for high energy physics by more than an order of magnitude, due to their
high gradient. Research is in progress at current facilities, including the
BELLA PetaWatt laser at LBNL, towards high quality 10 GeV beams and staging of
multiple modules, as well as control of injection and beam quality. The path
towards high-energy physics applications will likely involve hundreds of such
stages, with beam transport, conditioning and focusing. Current research
focuses on addressing physics and R&D challenges required for a detailed
conceptual design of a future collider. Here, the tools used to model these
accelerators and their resource requirements are summarized, both for current
work and to support R&D addressing issues related to collider concepts
Electroporation Therapy in Soft Tissue Sarcoma: A Potentially Effective Novel Treatment
Purpose. Examination of the potential of electroporation therapy (EPT) in a patient with metastatic soft tissue sarcoma. Patient. A 24-year-old male who underwent extensive resection and postoperative radiotherapy for a malignant peripheral nerve sheath tumor in the right infratemporal fossa with intracranial extension and invasion of the maxillary sinus and mandible had a recurrence in the scar of his craniotomy for which he was initially treated with doxorubicin. After discontinuation of doxorubicin he developed a metastatic mass at the same site for which he was treated with electroporation therapy. Method. The subcutaneous metastasis was infiltrated with bleomycin and electroporated. Results. Gradually the tumor became increasingly necrotic and demarcated from surrounding tissue. After 10 weeks no tumor was seen anymore. The wound healed secondarily. Discussion. Intralesional bleomycin followed by EPT is potentially effective, well tolerated, and easy to perform in well accessible soft tissue sarcoma sites
Growth and phase velocity of self-modulated beam-driven plasma waves
A long, relativistic charged particle beam propagating in a plasma is subject
to the self-modulation instability. This instability is analyzed and the growth
rate is calculated, including the phase relation. The phase velocity of the
accelerating field is shown to be significantly less than the drive beam
velocity. These results indicate that the energy gain of a plasma accelerator
driven by a self-modulated beam will be severely limited by dephasing. In the
long-beam, strongly-coupled regime, dephasing is reached in less than four
e-foldings, independent of beam-plasma parameters
A predictive model for swallowing dysfunction after curative radiotherapy in head and neck cancer
Laser guiding at > 1018 W/cm2 in plasma channels formed by the ignitor heater method
Experiments explore guiding of intense laser pulses, optimization using channel formation beams and gas jet targets, and the interplay of channel guiding and relativistic self guiding. Impact on laser wakefield particle acceleration is being assessed
Laser-heated capillary discharge plasma waveguides for electron acceleration to 8 GeV
A plasma channel created by the combination of a capillary discharge and inverse Bremsstrahlung laser heating enabled the generation of electron bunches with energy up to 7.8 GeV in a laser-driven plasma accelerator. The capillary discharge created an initial plasma channel and was used to tune the plasma temperature, which optimized laser heating. Although optimized colder initial plasma temperatures reduced the ionization degree, subsequent ionization from the heater pulse created a fully ionized plasma on-axis. The heater pulse duration was chosen to be longer than the hydrodynamic timescale of ≈ 1 ns, such that later temporal slices were more efficiently guided by the channel created by the front of the pulse. Simulations are presented which show that this thermal self-guiding of the heater pulse enabled channel formation over 20 cm. The post-heated channel had lower on-axis density and increased focusing strength compared to relying on the discharge alone, which allowed for guiding of relativistically intense laser pulses with a peak power of 0.85 PW and wakefield acceleration over 15 diffraction lengths. Electrons were injected into the wake in multiple buckets and times, leading to several electron bunches with different peak energies. To create single electron bunches with low energy spread, experiments using localized ionization injection inside a capillary discharge waveguide were performed. A single injected bunch with energy 1.6 GeV, charge 38 pC, divergence 1 mrad, and relative energy spread below 2% full-width half-maximum was produced in a 3.3 cm-long capillary discharge waveguide. This development shows promise for mitigation of energy spread and future high efficiency staged acceleration experiments
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