RESUMO
Particle-beam-driven plasma wakefield acceleration (PWFA) enables various novel high-gradient techniques for powering future compact light-source and high-energy physics applications. Here, a driving particle bunch excites a wakefield response in a plasma medium, which may rapidly accelerate a trailing witness beam. In this Letter, we present the measurement of ratios of acceleration of the witness bunch to deceleration of the driver bunch, the so-called transformer ratio, significantly exceeding the fundamental theoretical and thus far experimental limit of 2 in a PWFA. An electron bunch with ramped current profile was utilized to accelerate a witness bunch with a transformer ratio of 4.6_{-0.7}^{+2.2} in a plasma with length â¼10 cm, also demonstrating stable transport of driver bunches with lengths on the order of the plasma wavelength.
RESUMO
At the Photo Injector Test facility at DESY in Zeuthen (PITZ), an R&D platform for electron FLASH and very high energy electron radiation therapy and radiation biology is being prepared (FLASHlab@PITZ). The beam parameters available at PITZ are worldwide unique. They are based on experiences from 20â¯+â¯years of developing high brightness beam sources and an ultra-intensive THz light source demonstrator for ps scale electron bunches with up to 5 nC bunch charge at MHz repetition rate in bunch trains of up to 1â¯ms length, currently 22â¯MeV (upgrade to 250â¯MeV planned). Individual bunches can provide peak dose rates up to 1014 Gy/s, and 10â¯Gy can be delivered within picoseconds. Upon demand, each bunch of the bunch train can be guided to a different transverse location, so that either a "painting" with micro beams (comparable to pencil beam scanning in proton therapy) or a cumulative increase of absorbed dose, using a wide beam distribution, can be realized at the tumor. Full tumor treatment can hence be completed within 1â¯ms, mitigating organ movement issues. With extremely flexible beam manipulation capabilities, FLASHlab@PITZ will cover the current parameter range of successfully demonstrated FLASH effects and extend the parameter range towards yet unexploited short treatment times and high dose rates. A summary of the plans for FLASHlab@PITZ and the status of its realization will be presented.
Assuntos
Elétrons , Neoplasias , Humanos , RadiobiologiaRESUMO
The first Lewis acid-catalyzed intramolecular interrupted Nazarov cyclization of 1,4-pentadien-3-ols is described. Using FeBr3 as the catalyst, a series of new substituted cyclopenta[b]indoles was prepared-through a sequence of Nazarov cyclization, nucleophilic amination, and isomerization-with good yields and high diastereo- and regioselectivities. A similar catalytic process was also developed for the synthesis of structurally interesting spiro[indene-1,4'-quinoline]s.
RESUMO
Tsinghua Thomson Scattering X-ray Source (TTX) is the first-of-its-kind dedicated hard X-ray source in China based on the Thomson scattering between a terawatt ultrashort laser and relativistic electron beams. In this paper, we report the experimental generation and characterization of the first hard X-ray pulses (51.7 keV) via head-on collision of an 800 nm laser and 46.7 MeV electron beams. The measured yield is 1.0 × 10(6) per pulse with an electron bunch charge of 200 pC and laser pulse energy of 300 mJ. The angular intensity distribution and energy spectra of the X-ray pulse are measured with an electron-multiplying charge-coupled device using a CsI scintillator and silicon attenuators. These measurements agree well with theoretical and simulation predictions. An imaging test using the X-ray pulse at the TTX is also presented.